DE69609561T2 - Control method and device for reducing drive shocks in a hybrid vehicle. - Google Patents

Description

BACKGROUND OF THE INVENTION Field of the invention

The present invention relates generally to a drive device and a method for controlling the same. More particularly, the invention relates to a drive device for effectively transmitting or outputting a force or power from a motor to an output shaft and a method for controlling such a drive device.

Description of the state of the art

In proposed drive devices mounted in a motor vehicle, an output shaft of an engine is electromagnetically connected to an output shaft connected to a rotor of an engine via an electromagnetic clutch so that a power of the engine is transmitted to the output shaft (as disclosed, for example, in JAPANESE PATENT LAYING-OPEN GAZETTE No. 53-133814). When the rotational speed of the engine which starts driving the vehicle reaches a certain level, the proposed drive device supplies an exciting current to the electromagnetic clutch to crank the engine and thus performs fuel injection into the engine as well as spark ignition, starting the engine and enabling the engine to generate power. On the other hand, when the vehicle speed is reduced and the rotational speed of the engine decreases to or below the predetermined level, the drive device stops supplying the excitation current. Excitation current to the electromagnetic coupling or connection as well as fuel injection into the engine and spark ignition, thereby terminating the operation of the engine.

In the known drive devices described above, the torque output to the output shaft is significantly varied when the engine is started and stopped. This results in uneven driving. When the engine is started, the torque output from the engine is used to crank the machine, and the torque output to the output shaft is reduced by the amount required for cranking. When the engine is stopped, the supply of excitation current is stopped while the current from the engine is transmitted to the output shaft via the electromagnetic clutch, and the torque output to the output shaft is reduced by the amount of the current transmitted from the engine. Such a drop in the torque output occurs unexpectedly because the driver does not determine the time to start or stop the machine. Compared to an expected change, an unexpected change in the torque output to the output shaft exerts a greater shock on the driver, resulting in unsmooth driving.

Document AU 58401/73 (cf. the preambles of claims 1, 4, 8 and 10) discloses an embodiment comprising a clutch motor with two relatively rotatable rotors and an auxiliary motor. With such an arrangement, an efficient way of driving a vehicle in an electric mode and in a non-electric mode is provided. Part of the energy can be transferred mechanically and part electrically. However, such a torque converter with twin rotors becomes ineffective if there is a large slip between the rotors. The converter is therefore designed on the basis that periods of large slip would be short-lived and that normally a small amount of energy would be converted into electrical energy. de. Consequently, it is not possible to carry out fine or precise control.

Document EP 0 645 278 relates to an arrangement of an engine and a generator which are only electrically connected. The generator is connected to an engine while the engine drives an output shaft. A mode of the fifth embodiment is essentially carried out when the voltage VB of the battery is greater than or equal to the predetermined value Vmax (overcharge state of the battery) for a predetermined time, and solves the problem of preventing the emission gradation and the fuel consumption drop by gradually decreasing the generator output PG. The idle command is only supplied to the engine and the generator. With such control, blistering and heat generation caused by a voltage increase in the battery are prevented. The engine is controlled in response to the operation of the accelerator pedal, the brake or the like as well as in response to the speed.

SUMMARY OF THE INVENTION

The object of the invention is therefore to provide a drive device which can transmit or output a force from a motor to an output shaft with high efficiency.

Another object of the invention is to stop the engine without changing the torque output to the output shaft and in a method for controlling such a drive device.

The above and other related objects are achieved by devices according to claims 1 and 4 and methods according to claims 8 and 10. These comprise: The first drive device comprises: a motor having an output shaft; a motor drive device for driving of the motor; a first motor comprising a first rotor connected to the output shaft of the motor and a second rotor connected to the output shaft, the second rotor being coaxial and relatively rotatable to the first rotor, wherein power is transmitted between the output shaft of the motor and the output shaft via an electromagnetic connection between the first rotor and the second rotor; a first motor drive circuit for controlling the degree of electromagnetic connection of the first rotor and the second rotor in the first motor and for controlling rotation of the second rotor relative to the first rotor; a second motor connected to the output shaft; a second motor drive circuit for driving and controlling the second motor; a storage battery that is charged with a current regenerated by the first motor via the first motor drive circuit, that is charged with a current regenerated by the second motor via the second motor drive circuit, that discharges a current required to drive the first motor via the first motor drive circuit, and that discharges a current required to drive the second motor via the second motor drive circuit; a current decrease signal detecting means for detecting a current decrease signal to reduce a current output from the motor; a drive circuit control means for, when the current decrease signal detecting means detects the current decrease signal, controlling the first motor drive circuit in response to the signal to gradually reduce the degree of electromagnetic connection of the first rotor with the second rotor in the first motor, and for controlling the second motor drive circuit to allow the second motor to use the current stored in the storage battery and to compensate for a decrease in the current transmitted by the first motor accompanied by the decrease in the degree of electromagnetic connection; and a motor current reducing device for controlling the motor driving device to reduce the current output from the motor with the decrease of the degree of electromagnetic Connection of the first rotor with the second rotor, which is accompanied by the drive circuit control device.

The first drive device of the invention can effectively transmit or output the power from the motor to the output shaft through the functions of the first and second motors. In response to the current decrease signal, the degree of electromagnetic coupling of the first rotor with the second rotor in the first motor is gradually reduced. The second motor is then controlled to compensate for the decrease in the transmitted current, which is accompanied by the decrease in the degree of electromagnetic coupling, with the current stored in the second cell. This arrangement effectively reduces the current output from the motor without changing the power output to the output shaft.

According to an aspect of the first drive device, the current reduction signal detecting means comprises means for detecting an engine stop signal to stop the operation of the engine, and the engine current reduction means comprises means for controlling the engine drive means to interrupt the supply of fuel to the engine and stop the operation of the engine when the drive circuit control means releases the electromagnetic connection of the first rotor with the second rotor in the first engine.

According to one aspect, the present invention is directed to a second drive device for transmitting a force to an output shaft. The second drive device comprises: a motor having an output shaft; a motor drive device for driving the motor; a complex motor having a first rotor connected to the output shaft of the motor, a second rotor connected to the output shaft, coaxially and relatively rotatable to the first rotor, and comprising a stator for rotating the second rotor, the first rotor and the second rotor forming a first motor, the second rotor and the stator forming a second motor; a first motor drive circuit for driving and controlling the first motor in the complex motor; a second motor drive circuit for driving and controlling the second motor in the complex motor; a storage battery which is charged with a current regenerated by the first motor via the first motor drive circuit, which is charged with a current regenerated by the second motor via the second motor drive circuit, which discharges a current required to drive the first motor via the first motor drive circuit, and which discharges a current required to drive the second motor via the second motor drive circuit; a current take-off signal detecting means for detecting a current take-off signal to reduce a current output from the motor; drive circuit control means for, when the current decrease signal detecting means detects the current decrease signal, controlling the first motor drive circuit in response to the signal to gradually decrease the degree of electromagnetic connection of the first rotor with the second rotor in the first motor, and for controlling the second motor drive circuit to allow the second motor to use the power stored in the storage battery and to compensate for a decrease in the current transmitted by the first motor accompanied by the decrease in the degree of electromagnetic connection; and motor current reducing means for controlling the motor drive means to reduce the current output from the motor with the decrease in the degree of electromagnetic connection of the first rotor with the second rotor accompanied by the drive circuit control means.

The second drive device of the invention can transfer the power from the motor to the output shaft through the functions of the first motor, which consisting of the first rotor and the second rotor of the complex motor, and the second motor consisting of the second rotor and the stator. In response to the current decrease signal, the degree of electromagnetic coupling of the first rotor with the second rotor in the first motor is gradually reduced. The second motor is then controlled to compensate for the decrease in the transmitted current, which is accompanied by the decrease in the degree of electromagnetic coupling, with the current stored in the second cell. This arrangement effectively reduces the current output from the motor without changing the power output to the output shaft. The arrangement comprising the first motor and the second motor integrally connected to each other realizes a compact drive device.

According to an aspect of the second drive device, the current reduction signal detecting means comprises means for detecting an engine stop signal to stop the operation of the engine, and the engine current reduction means comprises means for controlling the engine drive means to interrupt the supply of fuel to the engine and stop the operation of the engine when the drive circuit control means releases the electromagnetic connection of the first rotor with the second rotor in the first engine.

According to another aspect, the invention is also directed to a third drive device for transmitting a force to an output shaft. The third drive device comprises: a motor having an output shaft; a motor drive device for driving the motor; a first motor comprising a first rotor connected to the output shaft of the motor and a second rotor connected to the output shaft, the first motor being coaxial and relatively rotatable to the first rotor, a force being transmitted between the output shaft of the motor and the output shaft via an electromagnetic connection. connection between the first rotor and the second rotor; a first motor drive circuit for controlling the degree of electromagnetic connection of the first rotor and the second rotor in the first motor and for controlling rotation of the second rotor relative to the first rotor; a second motor connected to the output shaft of the motor; a second motor drive circuit for driving and controlling the second motor; a storage battery charged with a current regenerated by the first motor via the first motor drive circuit, charged with a current regenerated by the second motor via the second motor drive circuit, discharging a current required to drive the first motor via the first motor drive circuit, and discharging a current required to drive the second motor via the second motor drive circuit; current take-off signal detecting means for detecting a current take-off signal to reduce a current output from the motor; a motor current reducing means for, when the current decrease signal detecting means detects the current decrease signal, controlling the motor drive circuit in response to the signal to gradually reduce the current output from the motor; and a drive circuit control means for controlling the first motor drive circuit and the second motor drive circuit to allow the first motor and the second motor to use the current stored in the storage battery and to compensate for a decrease in the current output from the motor accompanied by the motor current reducing means.

The third drive device of the invention can efficiently transmit or output the power from the motor to the output shaft through the functions of the first and second motors. In response to the current decrease signal, the current output from the motor is gradually decreased. The first motor and the second motor are then controlled to decrease the current output from the motor with the current stored in the second cell. This arrangement effectively reduces the current output from the motor without changing the power output or current output to the output shaft.

According to an aspect of the third drive device, the drive circuit control means comprises means for controlling the first motor drive circuit to allow the first motor to compensate for a decrease in the rotational speed of the output shaft of the motor under the decrease in the current output from the motor, and for controlling the second motor drive circuit to allow the second motor to compensate for a decrease in the torque under the decrease in the current output from the motor. In this arrangement, the current decrease signal detecting means comprises means for detecting an engine stop signal to stop the operation of the motor, and the motor current reducing means comprises means for controlling the motor drive means to stop the supply of fuel to the engine and to stop the operation of the motor when the current output from the motor becomes zero.

According to yet another aspect, the invention also provides a fourth drive device for transmitting a power to an output shaft. The fourth drive device comprises: a motor having an output shaft; a motor drive device for driving the motor; a complex motor comprising a first rotor connected to the output shaft of the motor, a second rotor connected to the output shaft, coaxial and relatively rotatable to the first rotor, and a stator for rotating the first rotor, the first rotor and the second rotor forming a first motor, the first rotor and the stator forming a second motor; a first motor drive circuit for driving and controlling the first motor in the complex motor; a second motor drive circuit device for driving and controlling the second motor in the complex motor; a storage battery which is charged with a power regenerated by the first motor via the first motor drive circuit, which is charged with a power regenerated by the second motor via the second motor drive circuit, which discharges a current required to drive the first motor via the first motor drive circuit, and which discharges a current required to drive the second motor via the second motor drive circuit; a current take-off signal detecting means for detecting a current take-off signal to reduce a current output from the motor; a motor current reducing means for, when the current take-off signal detecting means detects the current take-off signal, controlling the motor drive circuit in response to the signal to gradually reduce the current output from the motor; and drive circuit control means for controlling the first motor drive circuit and the second motor drive circuit to allow the first motor and the second motor to use the power stored in the storage battery and to compensate for a decrease in the current output from the motor accompanied by the motor current reducing means.

The fourth drive device of the invention can effectively transmit or output the power from the motor to the output shaft through the functions of the first motor consisting of the first rotor and the second rotor of the complex motor and the second motor consisting of the first rotor and the stator. In response to the current decrease signal, the current output from the motor is gradually decreased. The first motor and the second motor are then controlled to compensate for the decrease in the current output from the motor with the current stored in the second cell. This arrangement effectively decreases the current output from the motor without changing the power output. current output to the output shaft. The arrangement comprising the first motor and the second motor integrally connected to each other realizes a compact drive device.

According to an aspect of the fourth drive device, the drive device comprises means for controlling the first motor drive circuit to allow the first motor to compensate for a decrease in the rotational speed of the output shaft of the motor under the decrease in the current output from the motor, and for controlling the second motor drive circuit to allow the second motor to compensate for a decrease in the torque under the decrease in the current output from the motor. In this arrangement, the current decrease signal detecting means comprises means for detecting an engine stop signal to stop the operation of the motor, and the motor current reducing means comprises means for controlling the motor drive means to stop the supply of fuel to the engine and to stop the operation of the engine when the current output from the motor becomes zero.

The above objects are also at least partially achieved by a first method of controlling a drive device for transmitting a power to an output shaft. The first method comprises the steps of: (a) providing a motor having an output shaft, a motor drive device for driving the motor, a first motor comprising a first rotor connected to the output shaft of the motor and a second rotor connected to the output shaft, the first motor being coaxial and relatively rotatable to the first rotor, a power being transmitted between the output shaft of the motor and the output shaft via an electromagnetic connection of the first rotor and the second rotor, a second motor connected to the output shaft, and a storage battery charged with power regenerated by the first motor, the storage battery being connected to a charged with current regenerated by the second motor, discharging a current required to drive the first motor, and discharging a current required to drive the second motor; (b) detecting a current decrease signal to decrease the current output from the motor, (c) controlling the first motor in response to the current decrease signal to gradually decrease the degree of electromagnetic connection of the first rotor with the second rotor in the first motor, (d) controlling the second motor to enable the second motor to use power stored in the storage battery and compensate for a decrease in the current transmitted by the first motor accompanied by the decrease in the degree of electromagnetic connection, and (e) controlling the motor drive device to decrease the current output from the motor with the decrease in the degree of electromagnetic connection of the first rotor with the second rotor accompanied in step (c).

According to an aspect of the first method, the detected current take-off signal represents an engine stop signal to stop operation of the engine, and step (e) further comprises the step of controlling the engine drive means to interrupt a supply of fuel to the engine and to stop operation of the engine when the electromagnetic connection of the first rotor with the second rotor in the first engine has been reduced to a release position in response to the engine stop signal.

According to one aspect, the invention is also directed to a second method for controlling a drive device for transmitting a force to an output shaft. The method comprises the steps of: (a) providing a motor having an output shaft, a motor drive device for driving the motor, a first motor comprising a first rotor connected to the output shaft of the motor, and a second rotor connected to the output shaft, the second rotor being coaxial and is rotatable relative to the first rotor, wherein power is transmitted between the output shaft of the motor and the output shaft via an electromagnetic connection of the first rotor and the second rotor, a second motor connected to the output shaft of the motor, and a storage battery charged with current regenerated by the first motor, charged with current regenerated by the second motor, discharging current required to drive the first motor, and discharging current required to drive the second motor; (b) detecting a current decrease signal to decrease the current output from the motor, (c) controlling the motor drive device in response to the current decrease signal to gradually decrease the current output from the motor, and (d) controlling the first motor and the second motor to allow the first motor and the second motor to use current stored in the storage battery and to compensate for the decrease in current output from the motor accompanied by step (c).

According to an aspect of the second method, step (d) further comprises the steps of: (e) controlling the first motor to allow the first motor to compensate for a decrease in the speed of the output shaft of the motor under the decrease in the current output from the motor, and (f) controlling the second motor to allow the second motor to compensate for a decrease in the torque under the decrease in the current output from the motor.

These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view showing an arrangement of a ner drive device 20 as a first embodiment according to the present invention,

Fig. 2 is a cross-sectional view showing detailed arrangements of a clutch motor 30 and an auxiliary motor 40 included in the drive device 20 of Fig. 1,

Fig. 3 is a schematic view showing a general structure of a vehicle with the drive device 20 of Fig. 1 incorporated therein,

Fig. 4 is a graphical representation showing the basic operation of the drive device 20,

Fig. 5 is a flowchart showing a torque control routine executed by the controller 80,

Fig. 6 is a flow chart showing essential steps for controlling the clutch motor 30, which are carried out by the control device 80,

Fig. 7 and 8 are flow charts showing essential steps for controlling the auxiliary motor 40, which are carried out by the control device 80,

Fig. 9 is a flowchart showing an engine stop time torque control routine executed by the controller 80,

Fig. 10 is a flow chart showing essential steps for controlling the auxiliary motor 40 which are carried out by the controller 80 when the motor 50 stops operating,

Fig. 11 schematically shows a drive device 20A as a modification of a first embodiment,

Fig. 12 schematically illustrates the arrangement of another drive device 20B as a second embodiment according to the present invention,

Fig. 13 is a flowchart showing a torque control routine executed by the controller 80 in the second embodiment,

Fig. 14 is a flowchart showing an engine stop time torque control routine executed by the controller 80 in the second embodiment,

Fig. 15 schematically shows a drive device 20C as a modification of the second embodiment, and

Fig. 16 schematically shows a drive device 20D as another modification of the second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 is a schematic view showing the arrangement of a drive device 20 as a first embodiment according to the present invention; Fig. 2 is a cross-sectional view showing the detailed arrangements of a clutch motor 30 and an auxiliary motor 40 included in the drive device 20 of Fig. 1; and Fig. 3 is a schematic view showing a general structure of a vehicle having the drive device 20 of Fig. 1 included therein. The general arrangement of the vehicle will be described first for better understanding.

Referring to Fig. 3, the vehicle is provided with an engine or machine 50 which uses gasoline as a power source to is driven. The air taken in from an air supply system via a throttle valve 66 is mixed with fuel, ie in this embodiment gasoline, injected from a fuel injection valve 51. The air/fuel mixture is supplied to a combustion chamber 52 to be explosively ignited and burned. A linear movement of the piston 54, which is pushed down by the explosion of the air/fuel mixture, is converted into a rotary movement of a crankshaft 56. The throttle valve 66 is driven to open and close a moving element 68. A spark plug 62 converts a high voltage applied from an ignition device 58 via a distributor 60 to a spark plug, which explosively ignites and burns the air/fuel mixture.

The operation of the engine 50 is controlled by an electronic control unit (hereinafter referred to as EFIECU) 70. The EFIECU 70 receives information from various sensors that detect the operating conditions of the engine 50. These sensors include a throttle valve position sensor 67 for detecting the position of the throttle valve 66, a total vacuum sensor 72 for measuring a load applied to the engine 50, a water temperature sensor 74 for measuring the temperature of cooling water in the engine 50, and a speed sensor 76 and an angle sensor 78 mounted on the distributor 60 for measuring the rotational speed and the rotational angle of the crankshaft 56. A start switch 79 for detecting a start state ST of an ignition key (not shown) is also connected to the EFIECU 70. Other sensors and switches connected to the EFIECU 70 are omitted from the drawings.

The crankshaft 56 of the engine 50 is connected to an output shaft 22 via a clutch motor 30 and an auxiliary motor 40 (described in detail later). The output shaft 22 further connects a differential gear 24 which optionally transmits the torque output from the output shaft 22 of the drive device 20 to the left and right drive wheels 26 and 28. The clutch motor 30 and the auxiliary motor 40 are driven and controlled by a controller 80. The controller 80 includes an internal control CPU and receives inputs from a shift lever position sensor 84 attached to a shift lever 82 and an accelerator position sensor 65 attached to an accelerator pedal 64, as described in detail later. The controller 80 sends and receives a variety of data and information to and from the EFIECU 70 by means of communication. Details of the control process including a communication protocol will be described later.

With reference to Fig. 1, the drive device 20 essentially comprises the engine 50, the clutch motor 30 with an outer rotor 32 and an inner rotor 34, the auxiliary motor 40 with a rotor 42 and the control device 80 for driving and controlling the clutch motor 30 and the auxiliary motor 40. The outer rotor 32 of the clutch motor 30 is mechanically connected to the crankshaft 56 of the engine 50, while its inner rotor 34 is mechanically connected to the rotor 42 of the auxiliary motor 40.

As shown in Fig. 1, the clutch motor is constructed as a synchronous motor having permanent magnets 35 fixed to an inner surface of the outer rotor 32 and three-phase coils 36 wound on slots formed in the inner rotor 34. Power is supplied to the three-phase coils 36 via a rotary transformer 38. A thin laminated sheet of non-directional electromagnetic steel is used to form projections and slots for the three-phase coils 36 in the inner rotor 34. A resolver 39 for measuring a rotation angle θe of the crankshaft 56 is attached to the crankshaft 56. The function sensor 39 can also serve as the angle sensor 78 which is mounted on the distributor 60.

The auxiliary motor 40 is also designed as a synchronous motor having three-phase coils 44 wound on a stator 43 fixed to a housing 45 to generate a rotating magnetic field. The stator 43 is also made of a thin laminated sheet of non-directional electromagnetic steel. A plurality of permanent magnets 46 are attached to an outer surface of the rotor 42. In the auxiliary motor 40, an interaction between a magnetic field formed by the permanent magnets 46 and a rotating magnetic field formed by the three-phase coils 44 results in rotation of the rotor 42. The rotor 42 is mechanically connected to the output shaft 22, which functions as a torque output shaft of the drive device 20. A resolver 48 for measuring a rotation angle θd of the output shaft 22 is attached to the output shaft 22, which is further supported by a bearing 49 held in the housing 45.

The inner rotor 34 of the clutch motor 30 is mechanically connected to the rotor 42 of the auxiliary motor 40 and further to the output shaft 22. When the rotation and axial torque of the crankshaft 56 of the engine 50 are transmitted to the inner rotor 34 of the clutch motor 30 via the outer rotor 32, the rotation and torque are added to or subtracted from the transmitted rotation and torque by the auxiliary motor 40.

While the auxiliary motor 40 is designed as a conventional three-phase synchronous motor of the permanent magnet type, the clutch motor 30 comprises two rotating elements or rotating elements or rotors, ie the outer rotor 32 with the permanent magnets 35 and the inner rotor 34 with the three-phase coils 36. The detailed structure of the clutch motor 30 is shown in FIG. 2. The outer rotor 32 of the clutch motor 30 is fixed to a peripheral end of a gear 57 rotating around the crankshaft 56 by means of a thrust bolt 59a and a screw 59b. A central portion of the gear 57 projects to form a shaft-shaped member to which the inner rotor 34 is rotatably fixed by means of bearings 37A and 37B. One end of the output shaft 22 is fixed to the inner rotor 34.

A plurality of permanent magnets 35, four in this embodiment, are fixed to the inner surface of the outer rotor 32, as mentioned above. The permanent magnets 35 are magnetized toward the axial center of the clutch motor 30 and have magnetic poles of alternately opposite directions. The three-phase coils 36 of the inner rotor 34, which face the permanent magnets 35 with a small gap, are wound on a total of 24 slots (not shown) formed in the inner rotor 34. Supply of electricity to the respective coils generates magnetic fluxes passing through the projections (not shown) separating the slots from each other. Supply of three-phase alternating current to the respective coils rotates this magnetic field. The three-phase coils 36 are connected to receive electrical current supplied from the rotary transformer 38. The rotary transformer 38 includes primary windings 38a attached to the housing 45 and secondary windings 38b attached to the output shaft 22 coupled to the inner rotor 34. Electromagnetic induction allows electrical current to be transferred from the primary windings 38a to the secondary windings 38b or vice versa. The rotary transformer 38 has windings for three phases, i.e., the U, V and W phases, to enable the transfer of three-phase electrical currents.

Mutual influence of a magnetic field formed by an adjacent pair of permanent magnets 35 and a rotating magnetic field formed by the three-phase coils 36 of the inner rotor 34 results in a variety of behaviors of the outer rotor 32 and the inner rotor 34. The frequency of the three-phase alternating current supplied to the three-phase coils 36 is generally equal to a difference between the rotational speed (revolutions per second) of the outer rotor 32 directly connected to the crankshaft 56 and the rotational speed of the inner rotor 34. This results in a slip between the rotations of the outer rotor 32 and the inner rotor 34. Details of the control operations of the clutch motor 30 and the auxiliary motor 40 will be described later using the flow charts.

As mentioned above, the clutch motor 30 and the auxiliary motor 40 are driven and controlled by the controller 80. Now returning to Fig. 1, the controller 80 includes a first drive circuit 91 for driving the clutch motor 30, a second drive circuit 92 for driving the auxiliary motor 40, a control CPU 90 for controlling the first and second drive circuits 91 and 92, and a battery 94 including a number of secondary cells. The control CPU 90 is a one-chip microprocessor including a RAM 90a used as a working memory, a ROM 90b in which various control programs are stored, an input/output port (not shown), and a serial communication port (not shown) through which data is sent to and received from the EFIECU 70. The control CPU 90 receives a variety of data through the input/output interface. The input data includes a rotation angle θe of the crankshaft 56 of the engine 50 from the function encoder 39, a rotation angle θd of the output shaft 22 from the function encoder 48, an accelerator pedal position AP (pressure amount of the accelerator pedal 64) from the accelerator pedal position sensor 65, a shift lever position SP from the shift lever position sensor 84, currents Iuc and Ivc of the clutch motor from two ammeters or ampere-hour meters 95 and 96 in the first drive circuit 91, currents Iua and Iva of the auxiliary motor from two ammeters or ampere-hour meters 97 and 98 in the second drive circuit 92, and a remaining capacity BRM of the battery 94 from a remaining capacity meter 99. The remaining capacity meter 99 can measure the remaining capacity BRM of the battery 94 by any known method, for example, by measuring the specific gravity of an electrolytic solution in the battery 94 or the total weight of the battery 94, by calculating the currents and charging and discharging time, or by causing an instantaneous short circuit between terminals of the battery and measuring the internal resistance to the electric current.

The control CPU 90 outputs a first control signal SW1 for driving six transistors Tr1 to Tr6 which function as circuit elements of the first drive circuit 91, and a second control signal SW2 for driving six transistors Tr11 to Tr16 which function as circuit elements for the second drive circuit 92. The six transistors Tr1 to Tr6 in the first drive circuit 91 constitute a transistor inverter and are arranged in pairs to function as a source and a sink with respect to a pair of power lines P1 and P2. The three-phase coils (U, V, W) 36 of the clutch motor 30 are connected to the corresponding contacts of the paired transistors via the rotary transformer 38. The power lines P1 and P2 are connected to plus and minus terminals of the battery 94, respectively. The first control signal SW1 output from the control CPU 90 sequentially controls the turn-on time of the paired transistors Tr1 to Tr6. The electric current flowing through each coil 36 undergoes PWM (Pulse Width Modulation) to generate a quasi-sinusoidal oscillation, which allows the three-phase coils 36 to produce a rotating mass. to form a magnetic field.

The six transistors Tr11 to Tr16 in the second drive circuit 92 also form a transistor inverter and are arranged in the same manner as the transistors Tr1 to Tr6 in the first drive circuit 91. The three-phase coils (U, V, W) 44 of the auxiliary motor 40 are connected to the corresponding contacts of the paired transistors. The second control signal SW2 output from the control CPU 90 sequentially controls the on-time of the paired transistors Tr11 to Tr16. The electric current flowing through each coil 44 undergoes PWM to generate a quasi-sinusoidal oscillation, which allows the three-phase coils 44 to form a rotating magnetic field.

The drive device 20 thus configured operates according to the operating principles described below, in particular the principle of torque conversion. For example, it is assumed that the motor 50 driven by the EFIECU 70 rotates at a speed Ne equal to a predetermined value N1. While the transistors Tr1 to Tr6 in the first drive circuit 91 are in an OFF position, the controller 80 does not supply current to the three-phase coils 36 of the clutch motor 30 via the rotary transformer 38. No supply of electric current causes the outer rotor 32 of the clutch motor 30 to be electromagnetically separated from the inner rotor 34. This causes the crankshaft 56 of the engine 50 to spin. Under the condition that all transistors Tr1 to Tr6 are in the OFF position, no regeneration of energy occurs from the three-phase coils 36 and the engine 50 is kept in an idle state.

When the control CPU 90 of the control device 80 outputs the first control signal SW1 to turn on and off the transistors Tr1 to Tr6 in the first drive circuit 91, a constant electric current through the three-phase coils 36 of the clutch motor 30 based on the difference between the rotational speed Ne of the crankshaft 56 of the engine 50 and a rotational speed Nd of the output shaft 22 (i.e., a difference Nc (=Ne-Nd) between the rotational speed of the outer rotor 32 and that of the inner rotor 34 in the clutch motor 30). A certain slip accordingly exists between the outer rotor 32 and the inner rotor 34 which are connected to each other in the clutch motor 30. At this time, the inner rotor 34 rotates at the rotational speed Nd which is smaller than the rotational speed Ne of the crankshaft 56 of the engine 50. In this state, the clutch motor 30 operates as a generator and performs the regenerative operation to regenerate an electric current via the first drive circuit 91. In order to allow the assist motor 40 to consume energy identical to the electric energy regenerated by the clutch motor 30, the control CPU 90 controls on and off the transistors Tr11 to Tr16 in the second drive circuit 92. The on/off control of the transistors Tr11 to Tr16 allows an electric current to flow through the three-phase coils 44 of the assist motor 40, and thus the assist motor 40 performs the current operation to generate a torque.

Referring to Fig. 4, while the crankshaft 56 of the engine 50 is driven at a speed N1 and a torque T1, an energy in a range G1 is regenerated as an electric current by the clutch motor 30. The regenerated current is supplied to the auxiliary motor 40 and converted into an energy in a range G2 which enables the output shaft 22 to rotate at a speed N2 and a torque T2. The torque conversion is performed in the manner discussed above, and the energy is thus generated as a torque to the output shaft 22 in accordance with the slip in the clutch motor 30 or the speed difference Nc(=Ne-Nd).

In another example, assume that the motor 50 is driven at a speed Ne=N2 and a torque Te=T2, with the output shaft 22 being rotated at the speed N1 which is greater than the speed N2. In this state, the inner rotor 34 of the clutch motor 30 rotates relative to the outer rotor 32 in the rotational direction of the output shaft 22 at a speed defined by the absolute value of the speed difference Nc(=Ne-Nd). When operating as a normal motor, the clutch motor 30 consumes electric power to apply the energy of rotation to the output shaft 22. When the control CPU 90 of the controller 80 controls the second drive circuit 92 to allow the auxiliary motor 40 to regenerate electric power, slip between the rotor 42 and the stator 43 of the auxiliary motor 40 causes the regenerative current to flow through the three-phase coils 44. To allow the clutch motor 30 to consume the energy regenerated by the auxiliary motor 40, the control CPU 90 controls the first drive circuit 91 and the second drive circuit 92. This allows the clutch motor 30 to be driven without using electric power stored in the battery 94.

Returning to Fig. 4, when the crankshaft 56 of the engine 50 is driven at the speed N2 and the torque T2, the energy in the sum of the areas G2 and G3 is regenerated as an electric current by the auxiliary motor 40 and supplied to the clutch motor 30. Supply of regenerated current enables the output shaft 22 to rotate at the speed N1 and the torque T1.

Other than the torque conversion and speed conversion discussed above, the drive device 20 of the embodiment can charge the battery 94 with a surplus of electric energy or discharge the battery 94 to supplement the electric energy. This is possible by controlling the mechanical energy output from the motor 50 (ie, the product of the torque Te and rotational speed Ne), the electrical energy regenerated or consumed by the clutch motor 30 and the electrical energy regenerated or consumed by the auxiliary motor 40. The output energy from the motor 50 can therefore be transmitted as power to the output shaft 22 with a higher efficiency.

The torque conversion discussed above is implemented by a torque control method illustrated in the flow chart of Figure 5. The torque control routine of Figure 5 is executed to control the torque while the battery 94 is neither charging nor discharging.

When the program starts the torque control routine, the control CPU 90 of the controller 80 first receives data of the rotational speed Nd of the output shaft 22 in step S100. The rotational speed Nd of the output shaft 22 can be calculated from the rotational angle θd of the output shaft 22 read by the function generator 48. The control CPU 90 then reads the accelerator position AP from the accelerator position sensor 65 in step S101. The driver depresses the accelerator pedal 64 when ineffectiveness of the torque output is sensed. The value of the accelerator position AP accordingly corresponds to the desired output torque (i.e., the torque of the output shaft 22) that the driver desires. In subsequent step S102, the control CPU 90 calculates a target output torque (torque of the output shaft 22) Td* corresponding to the accelerator position input AP. The target output torque Td* is thus referred to as the torque output control value. Torque output control values Td* have been previously set for the corresponding accelerator positions AP. In response to an accelerator position AP input, the torque output control value Td* corresponding to the accelerator position input AP is taken from the preset torque output control values Td*.

In step S103, a power Pd to be applied to the output shaft 22 is calculated according to the expression Pd = Td*xNd, that is, the extracted torque output control value Td* (of the output shaft 22) is multiplied by the speed input Nd of the output shaft 22. The program then proceeds to step S104, in which the control CPU 90 sets a target motor torque Te* and a target motor speed Ne* of the motor 50 based on the power output Pd thus obtained. It is assumed here that all of the power Pd to be applied to the output shaft 22 is supplied from the motor 50. Since the energy supplied by the motor 50 is equal to the product of the torque Te and the speed Ne of the motor 50, the relationship between the energy output Pd and the target motor torque Te* and the target motor speed Ne* can be expressed as Pd = Te*xNe*. However, there are numerous combinations of the target motor torque Te* and the target motor speed Ne* that satisfy the above relationship. In this embodiment, an optimal combination of the target motor torque Te* and the target motor speed Ne* is selected to realize operation of the motor 50 with the highest possible efficiency.

In subsequent step S106, the control CPU 90 sets a torque control value Tc* of the clutch motor 30 based on the target motor torque Te* set in step S104. In order to keep the rotation speed Ne of the motor 50 at a substantially constant level, it is desirable to set the torque of the clutch motor 30 equal to the torque of the motor 50. The process in step S106 accordingly sets the torque control value Tc* of the clutch motor 30 equal to the target motor torque Te* of the motor 50.

After setting the torque control value Tc* of the clutch motor in step S106, the program continues with steps en S108, S110 and S111 to control the clutch motor 30, the auxiliary motor 40 and the motor 50, respectively. Advantageously, the control operations of the clutch motor 30, the auxiliary motor 40 and the motor 50 are shown as separate steps. In the current method, however, these control operations are comprehensively carried out. For example, the control CPU 90 simultaneously controls the clutch motor 30 and the auxiliary motor 40 by an interrupt process while passing an instruction to the EFIECU 70 by communication to simultaneously control the motor 50.

The control of the clutch motor 30 (step S108 of Fig. 5) is implemented according to a clutch motor control routine shown in the flow chart of Fig. 6. When the program starts with the clutch motor control routine, the control CPU 90 of the controller 80 first reads a rotation angle θd of the output shaft 22 from the function generator 48 in step 112 and a rotation angle θe of the crankshaft 56 of the engine 50 from the function generator 39 in step 114. The control CPU 90 then calculates a relative angle θc of the output shaft 22 and the crankshaft 56 by the equation θc = θe-θd in step S116.

The program proceeds to step S118, in which the control CPU 90 receives inputs of the clutch motor currents Iuc and Ivc flowing through the U-phase and V-phase of the three-phase coils 36 in the clutch motor 30, respectively, from the ammeters 95 and 96. Although the currents naturally flow through all three phases U, V and W, measurement is only required for the currents passing through the two phases since the sum of the currents is zero. In the following step S120, the control CPU 90 carries out a transformation of coordinates (a three-phase to a two-phase transformation) using the values of the currents flowing through the three phases obtained in step S118. The transformation of coordinates forms the values of the currents passing through the three phases, on the values of currents passing through d- and q-axes of the permanent magnet type synchronous motor, and is carried out according to equation (1) given below:

The transformation of coordinates is performed because the currents flowing through the d and q axes are essential for the torque control in the permanent magnet type synchronous motor. Alternatively, the torque control may be directly performed with the currents flowing through the three phases. After transformation into the currents of the two axes, the control CPU 90 calculates deviations of the currents Idc and Iqc actually flowing through the d and q axes from the current control values Idc* and Iqc* of the respective axes calculated from the torque control value Tc* of the clutch motor 30, and determines voltage control values Vdc and Vqc for the d and q axes in step S122. According to a concrete procedure, the control CPU 90 performs operations following the equations (2) and (3) below:

ΔIdc = Idc* - Idc

ΔIqc = Iqc* - Iqc.......... (2)

Vdc = Kp1 · ΔIdc + ΣKi1 · ΔIdc

Vqc = Kp2 · ΔIqc + Sigma;Ki2 · ΔIqc......... (3)

where Kp1, Kp2, Ki1 and Ki2 represent coefficients which are adjusted to suit the characteristics of the motor used.

The voltage control value Vdc (Vqc) includes a part in proportion to the deviation ΔI from the current control value I* (first term on the right side of equation (3)) and a summation of historical data of the deviations ΔI for "i" times (second term on the right side). The control CPU 90 then reverse transforms the coordinates of the voltage control values thus obtained (a two-phase to a three-phase transformation) in step S124. This corresponds to a reversal of the transformation performed in step S120. The reverse transformation determines voltages Vuc, Vvc and Vwc actually applied to the three-phase coils 36 as given below:

The actual voltage control is performed by an on-off operation of the transistors Tr1 to Tr6 in the first drive circuit 91. In step S126, the on-and-off time of the transistors Tr1 to Tr6 in the first drive circuit 91 is PWM (Pulse Width Modulation) controlled to obtain the voltage control values determined by the above equation (4).

The torque control value Tc* is positive when a positive torque is applied to the output shaft 22 in the rotation direction of the crankshaft 56. For example, it is assumed that a positive value is set to the torque control value Tc*. In this assumption, when the rotation speed Ne of the motor 50 is larger than the rotation speed Nd of the output shaft 22, that is, when the rotation speed difference Nc(=Ne-Nd) is positive, the clutch motor 30 is controlled to perform the regenerative operation and generate a regenerative current corresponding to the rotation speed difference Nc. When the rotation speed Ne of the motor 50 is smaller than the rotation speed Nd of the output shaft 22, that is, On the other hand, when the speed difference Nc(=Ne-Nd) is negative, the clutch motor 30 is controlled to perform the current operation and rotate relative to the crankshaft 56 in the rotational direction of the output shaft 22 at a speed defined by the absolute value of the speed difference Nc. For the positive torque control value Tc*, the regenerative operation and the current operation of the clutch motor 30 perform the identical circuit control. According to a concrete method, the transistors Tr1 to Tr6 of the first drive circuit 91 are controlled to allow a positive torque to be applied to the output shaft 22 by the combination of the magnetic field generated by the permanent magnets 35 applied to the outer rotor 32 with the rotating magnetic field generated by the currents flowing through the three-phase coils 36 on the inner rotor 34 in the clutch motor 30. The identical switching control is carried out for the regenerative operation and the current operation of the clutch motor 30 as long as the sign of the torque control value Tc* is not changed. The clutch motor control routine of Fig. 6 is therefore applicable to the regenerative operation and the current operation. Under the condition of braking of the output shaft 22 or reverse movement of the vehicle, the torque control value Tc* has a negative sign. The clutch motor control routine of Fig. 6 is therefore applicable to the control operation under such conditions when the relative angle θc is varied in the reverse direction in step S126.

7 and 8 are flowcharts showing details of the control process of the auxiliary motor 40 executed in step S110 in the flowchart of Fig. 5. Referring to the flowchart of Fig. 7, when the program enters the auxiliary motor control routine, the control CPU 90 first receives data of the rotation speed Nd of the output shaft 22 in step S131. The rotation speed Nd of the output shaft 22 is calculated from the rotation angle θd of the output shaft 22 obtained by the function ossgeber 48. The control CPU 90 then receives data of the rotational speed Ne of the engine 50 in step S132. The rotational speed Ne of the engine 50 may be calculated from the rotational angle θe of the crankshaft 56 read by the function sensor 39 or directly measured by the speed sensor 76 mounted on the distributor 60. In the latter case, the control CPU 90 receives data of the rotational speed Ne of the engine 50 by communicating with the EFIECU 70 connected to the speed sensor 76.

A speed difference Nc between the speed input Nd of the output shaft 22 and the speed input Ne of the motor 50 is calculated according to the equation Nc = Ne-Nd in step S133. In the following step S134, the electric current (energy) Pc regenerated or consumed by the clutch motor 30 is calculated according to the given equation (5):

Pc = Ksc Nc Tc.......... (5)

where Ksc represents the efficiency of a regenerative operation or a current operation in the clutch motor 30. The product NcxTc defines the current corresponding to the area G1 in the graph of Fig. 4, where Nc and Tc denote the speed difference and the actual torque generated by the clutch motor 30, respectively.

In step S135, a torque control value Ta* of the assist motor 40 is determined by the given equation (6):

Ta* = ksa Pc/Nd.......... (6)

where ksa represents the efficiency of the regenerative operation or the current operation in the auxiliary motor 40. The torque control value Ta* of the auxiliary motor 40 thus obtained is multiplied by a maximum torque Tamax which drives the auxiliary motor 40. potentially loaded, in step S136. If the torque control value Ta* exceeds the maximum torque Tamax, the program jumps to step S138 in which the torque control value Ta* is limited to the maximum torque Tamax.

After the torque control value Ta* is set equal to the maximum torque Tamax in step S138 or after the torque control value Ta* in step S138 is determined not to exceed the maximum torque Tamax in step S136, the program proceeds to step S140 in the flowchart of Fig. 8. The control CPU 90 reads the rotation angle θd of the output shaft 22 from the function generator 48 in step S140 and receives data of the currents Iua and Iva of the auxiliary motor, which flow through the U-phase and the V-phase of the three-phase coils 44 in the auxiliary motor 40, respectively, from the ammeters 97 and 98 in step S142. The control CPU 90 then performs transformation of coordinates for the currents of the three phases in step S144, calculates voltage control values Vda and Vqa in step S146, and performs inverse transformation of coordinates for the voltage control values in step S148. In subsequent step S150, the control CPU 90 determines the on and off timing of the transistors Tr11 to Tr16 in the second drive circuit 92 for PWM (Pulse Width Modulation) control. The process performed in steps S144 to S150 is similar to that performed in steps S120 to S126 of the clutch motor control routine shown in the flowchart of Fig. 6.

The auxiliary motor 40 is subject to the current operation for the positive torque control value Ta* and to the regenerative operation for the negative torque control value Ta*. Like the current operation and the regenerative operation of the clutch motor 30, the auxiliary motor control routine of Figs. 7 and 8 is applicable to the current operation and the regenerative operation of the auxiliary motor 40. This is also true when the output shaft 22 rotates in the opposite direction of the crankshaft 56, ie, when the vehicle is moving backwards. The torque control value Ta* of the auxiliary motor 40 is positive when a positive torque is transmitted to the output shaft 22 in the direction of rotation of the crankshaft 56.

The control of the engine 50 (step S111 in Fig. 5) is performed in the following manner. In order to obtain a stationary drive with the target engine torque Te* and the target engine speed Ne* (set in step S104 in Fig. 5), the control CPU 90 controls the torque Te and the speed Ne of the engine 50 to approximate the target engine torque Te* and the target engine speed Ne*, respectively. According to a concrete method, the control CPU 90 sends an instruction to the EFIECU 70 through communication to control the amount of fuel injection or the throttle valve position. Such control eventually makes the torque Te and the speed Ne of the engine 50 approximate the target engine torque Te* and the target engine speed Ne.

This process allows the output (TexNe) of the motor 50 to perform a free torque conversion and to be transmitted to the output shaft 22 if necessary.

A charge control of the battery 94 starts when the remaining capacity BRM of the battery 94 becomes equal to or less than a charge start value BL previously set as a value required for the charge process. A charge energy Pbi required for charging the battery 94 is added to the output energy Pd calculated in the torque control routine of Fig. 5 in step S103. The process in step S104 and subsequent steps is carried out with the newly set output energy Pd. On the other hand, the charge energy Pbi is supplied from the current Pc of the clutch motor 30 calculated in the assist motor control routine of Fig. 7 in step S134. is calculated. The process in step S135 and subsequent steps is carried out with the newly set clutch motor current Pc. This process allows the battery 94 to be charged with the charging energy Pbi.

On the other hand, a discharge control of the battery 94 starts when the remaining capacity BRM of the battery 94 becomes equal to or larger than a discharge start value BH set as a value requiring the discharge process. A discharge energy Pbo required for discharge of the battery 94 is subtracted from the output energy Pd calculated in the torque control routine of Fig. 5 in step S103. The process in step S104 and subsequent steps is carried out with the newly set output energy Pd. On the other hand, the discharge energy Pbo is added to the current Pc of the clutch motor 30 calculated in the assist motor control routine of Fig. 7 in step S134. The process in step S135 and subsequent steps is carried out with the renewed set current Pc of the clutch motor. This process allows the battery 94 to be discharged with the discharge energy Pbo.

Discharge control of the battery 94 is performed, for example, by stopping the operation of the motor 50 and allowing the vehicle to be driven only by the power from the battery 94. Driving of the vehicle with the power discharged from the battery 94 under the non-driving condition of the motor 50 starts when the remaining capacity BRM of the battery 94 becomes equal to or larger than the discharge start value BH set as a value requiring the discharge process, or when the driver gives a clear instruction to start the discharge process. An engine stop time torque control routine shown in the flowchart of Fig. 9 is executed to stop operation of the motor 50 and the vehicle with the power stored in the battery 94. Instead of the torque control routine of Fig. 5, the engine stop time torque control routine of Fig. 9 is repeatedly executed at predetermined time intervals when the controller 80 receives a battery discharge signal indicating that the remaining capacity BRM of the battery 94 becomes equal to or greater than the discharge start value BH or a clear instruction from the driver as a stop signal to stop or interrupt the operation of the engine 50.

When the program starts the engine stop time torque control routine, the control CPU 90 first receives accelerator pedal position AP data from the accelerator pedal position sensor 65 in step S160 and calculates a torque output control value Td* corresponding to the accelerator pedal position input AP in step S162. The torque control value Tc* of the clutch motor 30 is compared with a subtraction amount ΔTc in step S164. In order to gradually reduce the power output Pd of the motor 50 to the no-load state, the torque control value Tc* of the clutch motor 30 acting as the torque Te of the motor 50 is gradually reduced by subtraction amounts ΔTc. The subtraction amount ΔTc is determined depending on the execution interval of this routine and the performance of the clutch motor 30 and the motor 50. When this routine is activated for the first time in response to the stop signal for stopping the operation of the motor 50, the torque control value Tc* of the clutch motor 30 is generally larger than the subtraction amount ΔTc because the clutch motor 30 transmits the torque Te of the motor 50 to the output shaft 22.

If the torque control value Tc* of the clutch motor 30 is larger than the subtraction amount ΔTc, the program proceeds to step S166, in which the control CPU 90 subtracts the subtraction amount ΔTc from the torque control value Tc* set in the previous cycle of this routine to obtain a new torque control value Tc* of the clutch motor 30. as expressed by equation (7) given below:

New Tc* - Previous Tc* - ΔTc.......... (7)

In subsequent step S168, the control CPU 90 further calculates the torque control value Ta* of the assist motor 40 by subtracting the new torque control value Tc* from the torque output control value Td*, as expressed by the equation (8) given below:

Ta* = Td* - Tc*.......... (8)

The control CPU 90 calculates a new power output Pd of the engine 50 by subtracting a subtraction amount ΔPd from the power output Pd set in the previous cycle of this routine in step S170. The power output Pd of the engine 50 is decreased by the subtraction amount ΔPd every time this routine is executed. The power output Pd therefore decreases gradually to the no-load state. In order to allow the target engine torque Te* and the target rotation speed Ne* of the engine 50 to gradually approach the idle state, the subtraction amount ΔPd is set to be slightly larger than the value calculated according to the equation (9) given below:

ΔPd = ΔTc · Ne.......... (9)

In step S172, the control CPU 90 sets the target motor torque Te* and the target motor speed Ne* of the motor 50 based on the torque control value Tc* of the clutch motor 30 and the power output Pd of the motor 50, which are set in steps S166 and S170, respectively. The target motor torque Te* is set equal to the torque control value Tc* of the clutch motor 30 to cause stable rotation of the motor 50. The target Engine speed Ne* is calculated according to equation (10) given below:

Pd = Te* Ne*.......... (10)

As described above, the subtraction amount ΔPd is set to be approximately larger than the product of the subtraction amount ΔTc and the rotation speed Ne of the motor 50 in this embodiment. That is, the target motor rotation speed Ne* is set to be slightly smaller than the actual rotation speed Ne of the motor 50. Under the condition that the subtraction amount ΔTc is set equal to the amount calculated by the equation (9), the target rotation speed Ne* is equal to the actual rotation speed Ne of the motor 50. In this case, the rotation speed Ne of the motor 50 is unchanged while the target motor torque Te* is reduced.

After setting the torque control values Tc* and Ta* as well as the target motor torque Te* and the target motor speed Ne*, the control CPU 90 controls the clutch motor 30 (step S174), the auxiliary motor 40 (step S176), and the motor 50 (step S178) to obtain these values. The control of the clutch motor 30 executed in step S174 follows the clutch motor control routine shown in the flowchart of Fig. 6. Repeated execution of the motor stop time torque control routine makes the target motor speed Ne* of the motor 50 equal to or smaller than the rotation speed Nd of the output shaft 22. Under such conditions, the clutch motor 30 is controlled with the power stored in the battery 94 to obtain the rotation speed (Nd-Ne) with the torque control value Tc*.

The control of the auxiliary motor 40 executed in step S176 follows an auxiliary motor control routine shown in the flowchart of Fig. 10 instead of the auxiliary motor control routine of Figs. 7 and 8. The process executed in the auxiliary motor control routine of Fig. 10 in steps S190 to S197 is identical to the process performed in steps S136 to S150 in the auxiliary motor control routine of Figs. 7 and 8. Since the torque control value Ta* of the auxiliary motor 40 has been set in the motor stop time torque control routine of Fig. 9, the process for determining the torque control value Ta* in the auxiliary motor control routine of Figs. 7 and 8 is not required. Current regenerated by the clutch motor 30 is insufficient for PWM (Pulse Width Modulation) control of the auxiliary motor 40 to generate voltages corresponding to the preset torque control value Ta*. The shortage is supplied by the current stored in the battery 94.

Regardless of the power output Pd of the motor 50, the torque output to the output shaft 22 as a result of the torque control becomes equal to the torque output control value Td*, which is the sum of the torque control value Tc* of the clutch motor 30 and the torque control value Ta* of the auxiliary motor 40. The torque output depends on the accelerator pedal position AP. As long as the accelerator pedal position AP remains unchanged, repeated execution of this routine does not change the torque output to the output shaft 22.

Since the engine stop time torque control routine is repeatedly executed, the torque control value Tc* of the clutch motor 30 becomes equal to or smaller than the subtraction amount ΔTc in step S164. Under such conditions, the engine 50 is kept substantially idle and the vehicle is substantially driven only by a torque Ta of the auxiliary motor 40. When the program recognizes this condition, the control CPU 90 sets the torque control value Tc* of the clutch motor 30 equal to zero in step S180. The control CPU 90 sets the torque control value Ta* of the auxiliary motor 40 equal to the torque output control value Td* in step S182 and assigns the value "0" to the target engine torque Te* and the target engine speed Ne* of the engine 50 in step S184. After the processing in steps S180 to S184, the program proceeds to steps S174 to S178 to control the clutch motor 30, the auxiliary motor 40, and the engine 50 as described above. The engine stop time torque control process completely releases the electromagnetic coupling of the output shaft 22 to the crankshaft 56 via the clutch motor 30, stops the operation of the engine 50, and allows the vehicle to be driven only by the torque Ta of the auxiliary motor 40 generated by the power stored in the battery 94.

As explained above, the drive device 20 of the first embodiment can stop the operation of the motor 50 without changing the torque output to the output shaft 22. Namely, the arrangement of the embodiment prevents the unexpected change of the torque output to the output shaft 22 and ensures smooth running. The fixed torque output to the output shaft 22 effectively prevents undesirable vibration of the vehicle. The power output from the motor 50 is used as the current in the process of stopping the operation of the motor 50. This further promotes energy efficiency.

In the drive device 20 of the first embodiment, the motor stop time torque control routine of Fig. 9 is repeatedly executed when the controller 80 receives a battery discharge signal indicating that the remaining capacity BRM of the battery 90 is equal to or greater than the discharge start value BH or a clear instruction from the driver as a stop signal to stop the operation of the motor 50. Alternatively, the same routine may be repeatedly executed when the battery discharge signal or the clear instruction from the driver is an input as a power decrease signal indicating that the output power Pd of the motor 50 has decreased. In the last In this case, the torque control value Tc* of the clutch motor 30 is compared with the reduced target motor torque Te* of the motor 50 calculated from the reduced output power Pd of the motor 50 in step S164 in the flowchart of Fig. 9, instead of the subtraction amount ΔTc. When the torque control value Tc* is larger than the reduced target motor torque Te*, the program executes the processing in steps S166 to S178. On the other hand, when the torque control value Tc* is equal to the reduced target torque Te*, the program executes only step S168 before the processing in steps S174 to S178. This arrangement reduces the output power Pd of the motor 50 without changing the output torque to the output shaft 22.

In the arrangement of the drive device 20 shown in Fig. 1, the clutch motor 30 and the auxiliary motor 40 are separately attached to the different positions of the output shaft 22. However, similar to a modified drive device 20A shown in Fig. 11, the clutch motor and the auxiliary motor may be integrally connected. A clutch motor 30A of the drive device 20A includes an inner rotor 34A connected to the crankshaft 56 and an outer rotor 32A connected to the output shaft 22. Three-phase coils 36A are attached to the inner rotor 34A and permanent magnets 35A are attached to the outer rotor 32A such that the outer surface and the inner surface thereof have different magnetic poles. An auxiliary motor 40A includes the outer rotor 32A of the clutch motor 30A and a stator 43 with three-phase coils 44 mounted thereon. In this arrangement, the outer rotor 32A of the clutch motor 30A also functions as a rotor of the auxiliary motor 40A. Since the three-phase coils 36A are mounted on the inner rotor 34A connecting the crankshaft 56, a rotary transformer 38A for supplying electric current to the three-phase coils 36A of the clutch motor 30A is attached to the crankshaft 56.

In the drive device 20A, the voltage applied to the three-phase coils 36A on the inner rotor 34A is controlled with respect to the inner surface magnetic pole of the permanent magnets 35A arranged on the outer rotor 32A. This allows the clutch motor 30A to operate in the same manner as the clutch motor 30 of the drive device 20 shown in Fig. 1. The voltage applied to the three-phase coils 44 on the stator 43 is controlled with respect to the outer surface magnetic pole of the permanent magnets 35 arranged on the outer rotor 32A. This allows the auxiliary motor 40A to operate in the same manner as the auxiliary motor 40 of the drive device 20. The torque control routine of Fig. 5 and the engine stop time torque control routine of Fig. 9 are also applicable to the drive device 20A shown in Fig. 11, which accordingly performs the same operations and exerts the same effects as those of the drive device 20 shown in Fig. 1.

As explained above, the outer rotor 32A functions simultaneously as one of the rotors in the clutch motor 30A and as the rotor of the auxiliary motor 40A, effectively reducing the size and weight of the entire drive device 20A.

Fig. 12 schematically shows an essential part of another drive device 20B as a second embodiment of the present invention. The drive device 20B of Fig. 11 has a similar structure to that of the drive device 20 of Fig. 1, except that the auxiliary motor 40 is attached to the crankshaft 56 arranged between the engine 50 and the clutch motor 30. In the drive device 20B of the second embodiment, the same reference numerals and symbols denote the same elements as those of the drive device 20 of Fig. 1. The symbols used in the description have the same meanings, unless otherwise stated.

The following describes the essential operation of the drive device 20B shown in Fig. 12. For example, assume that the engine 50 is driven with a torque Te and a rotational speed Ne. When a torque Ta is added to the crankshaft 56 by the auxiliary motor 40 connected to the crankshaft 56, the sum of the torques (Te + Ta) is consequently applied to the crankshaft 56. When the clutch motor 30 is controlled to generate the torque Tc equal to the sum of the torques (Te + Ta), the torque Tc (= Te + Ta) is transmitted to the output shaft 22.

When the rotation speed Ne of the motor 50 is greater than the rotation speed Nd of the output shaft 22, the clutch motor 30 regenerates an electric current based on the rotation speed difference Nc between the rotation speed Ne of the motor 50 and the rotation speed Nd of the output shaft 22. The regenerated current is supplied to the auxiliary motor 40 via the power lines P1 and P2 and the second drive circuit 92 to activate the auxiliary motor 40. Provided that the torque Ta of the auxiliary motor 40 is substantially equal to the electric current regenerated by the clutch motor 30, free torque conversion is permitted for the power output from the motor 50 in a range that satisfies the relationship of equation (11) given below. Since the relationship of equation (11) represents the ideal state with an efficiency of 100%, (TcxNd) is a little smaller than (TexNe) in the actual state:

Te · Ne = Tc · Nd.......... (11)

Referring to Fig. 4, under the condition that the crankshaft 56 rotates at the torque T1 and at the speed N1, the energy corresponding to the sum of the areas G1 + G3 is regenerated by the clutch motor 30 and supplied to the Auxiliary motor 40 converts the energy received in the sum of the areas G1 + G3 into the energy corresponding to the sum of the areas G2 + G3 and transfers the converted energy to the crankshaft 56.

When the rotational speed Ne of the motor 50 is smaller than the rotational speed Nd of the output shaft 22, the clutch motor 30 operates as a normal motor. In the clutch motor 30, the inner rotor 34 rotates relative to the outer rotor 32 in the rotational direction of the output shaft 22 at a rotational speed defined by the absolute value of the rotational speed difference Nc(=Ne-Nd). Provided that the torque Ta of the auxiliary motor 40 is set to a negative value that allows the auxiliary motor 40 to regenerate electric power substantially equal to the electric power consumed by the clutch motor 30, free torque conversion is also permitted for the power output from the motor 50 within the range that satisfies the relationship of the equation (11) given above.

Referring to Fig. 4, under the condition that the crankshaft 56 rotates at the torque T2 and at the speed N2, the energy corresponding to the area G2 is regenerated by the assist motor 40 and consumed by the clutch motor 30 like the energy corresponding to the area G1.

The control method of the second embodiment discussed above follows the torque control routine shown in the flowchart of Fig. 13. When the program starts the torque control routine, the control CPU 90 of the controller 80 first performs the processing of steps S200 to S208, which are identical to those of steps S100 to S104 in the flowchart of Fig. 5. The control CPU 90 reads the rotation speed Nd of the output shaft 22 in step S200 and the accelerator pedal position AP (down) in step S202, and calculates the torque output control value Td* from the input accelerator pedal position AP. The control CPU 90 then calculates the power Pd to be transmitted from the output shaft 22 based on the calculated torque output control value Td* and the input rotation speed Nd of the output shaft 22 in step S206, and sets the target engine torque Te* and the target rotation speed Ne* of the engine 50 in step S208.

In the following step S210, the control CPU 90 calculates the torque control value Ta* of the auxiliary motor 40 according to the given equation (12):

Ta* = Ksc · (Td* - Te*)........ (12)

In step S212, the torque control value Tc* of the clutch motor 30 is calculated from the torque control value Ta* of the assist motor 40 thus obtained according to the expression Equation (13):

Tc* = Te* + Ta*.......... (13)

The control CPU 90 controls the clutch motor 30 in step S214, the assist motor 40 in step S216, and the motor 50 in step S217 based on the torque control values Ta* and Tc*, the target motor torque Te*, and the target rotation speed Ne* thus obtained. The concrete operation of the clutch motor control (step S214) is identical to that described above according to the flowchart of Fig. 6, and the concrete operation of the motor control (step S217) is identical to that of the first embodiment described above. The auxiliary motor control executed in step S216 basically follows the procedure of steps S192 to S196 in the auxiliary motor control routine of Fig. 10, except that the rotation angle θe of the crankshaft 56 of the engine 50 measured by the function encoder 39 is processed instead of the rotation angle θd of the output shaft 22. This modification is due to the position of the auxiliary motor 40 which is attached to the crankshaft 56.

The drive device 20B of the second embodiment can effectively control the charge and discharge of the battery 94. The vehicle can be driven only by the power stored in the battery 94 while the operation of the motor 50 is stopped. The following describes the process of stopping the operation of the motor 50 and driving the vehicle with the power discharged from the battery 94 based on a motor stop time torque control routine of the second embodiment shown in the flowchart of Fig. 14. Similar to the same routine of the first embodiment, the engine stop time torque control routine of Fig. 14 is repeatedly executed at predetermined time intervals instead of the torque control routine of Fig. 13 when the controller receives a battery discharge signal indicating that the remaining capacity BRM of the battery 94 becomes equal to or greater than the discharge start value BH or a clear instruction from the driver as a stop signal to stop the operation of the engine 50.

When the program enters the engine stop time torque control routine, the control CPU 90 first receives accelerator pedal position AP data from the accelerator pedal position sensor 65 in step S220 and calculates the torque output control value Td* corresponding to the input accelerator pedal position AP in step S222. The output power Pd of the engine 50 is compared with a threshold value Pdref in step S224. The threshold value Pdref is set to be slightly greater than the output power Pd of the engine 50 at idle. When this routine is first activated in response to the stop signal to stop or suspend operation of the engine 50, the output power Pd is generally greater than the threshold value Pdref since the vehicle is driven by the power output from the engine 50.

If the output energy Pd is greater than the threshold value Pdref in step S224, the program proceeds to step S226, in which the control CPU 90 subtracts the subtraction amount ΔPd from the output energy Pd set in the previous cycle of this routine to determine a new output energy Pd. In subsequent step S228, the control CPU 90 sets a target motor torque Te* and a target motor speed Ne* of the motor 50 by considering the efficiency of the motor 50 and other conditions according to equation (14) given below:

Pd = Te* Ne*.......... (14)

It is preferable that the target engine torque Te* and the target engine speed Ne* are set to gradually obtain the idling state of the engine 50. The torque control value Ta* of the auxiliary motor 50 is calculated in step S230 according to the equation (15) given below:

Ta* = Td* - Te*.......... (15)

wherein the torque control value Tc* of the clutch motor 30 is set equal to the torque output control value Td* in step S232.

The control CPU 90 executes control of the clutch motor 30 (step S234), control of the assist motor 40 (step S236), and control of the motor 50 (in step S238), which are identical to the processes executed in steps S214 to S217 in the torque control routine of Fig. 13.

Repeated execution of this routine makes the target motor speed Ne* of the motor 50 equal to or less than the speed Nd of the output shaft 22. Under such conditions, the clutch motor 30 is controlled with the current stored in the battery 94 to control the speed (Nd-Ne) at a rate of torque control value Tc*. Current regenerated by the clutch motor 30 is not sufficient for a PWM control of the auxiliary motor 40 to generate voltages corresponding to the preset torque control value Ta*. The shortage is supplied by the current stored in the battery 94.

Regardless of the decrease in the output power Pd of the motor 50, the torque output to the output shaft 22 as a result of the torque control becomes equal to the torque output control value Td*, which depends on the accelerator pedal position AP. As long as the accelerator pedal position AP remains unchanged, repeated execution of this routine does not change the torque output to the output shaft 22.

As the engine stop time torque control routine is repeatedly executed, the output power Pd of the engine 50 becomes equal to or less than the threshold value Pdref in step S224. Under such conditions, the engine 50 is kept substantially idle. When the program detects this condition, the control CPU 90 sets the target engine torque Te* and the target engine speed Ne* of the engine 50 equal to zero in step S240, sets the torque control value Ta* of the auxiliary motor 40 equal to the torque output control value Td* in step S242, and sets the torque control value Tc* of the clutch motor 30 equal to the torque output control value Td* in step S244. This is followed by controlling the clutch motor 30 (step S234), the auxiliary motor 40 (step S236), and the engine 50 (step S238). The engine stop time torque control operation stops the operation of the engine 50 and allows the vehicle to be driven by the torque Tc of the clutch motor 30 generated by the current discharged from the battery 94. The auxiliary motor 40 receives the reaction force of the torque control value Tc* transmitted from the clutch motor 30 to the output shaft 22. When the engine 50 stops the operation, the rotation speed Ne of the engine 50 becomes zero and a constant current, which generates a torque relative to the torque control value Tc*, through the three-phase coils of the auxiliary motor 40. The crankshaft 56 is accordingly electromagnetically locked or immobilized by the auxiliary motor 40.

As explained above, the drive device 20B of the second embodiment can stop or interrupt the operation of the engine 50 without changing the torque output to the output shaft 22. Namely, the arrangement of the second embodiment prevents the unexpected change of a torque output to the output shaft 22 and ensures a smooth ride. The fixed torque to the output shaft 22 effectively prevents undesirable vibration of the vehicle.

In the drive device 20B of the second embodiment, the motor stop time torque control routine of Fig. 14 is repeatedly executed when the controller 80 receives a battery discharge signal indicating that the remaining capacity BRM of the battery 94 becomes equal to or greater than the discharge start value BH or a clear instruction from the driver as a stop signal to stop the operation of the motor 50. Alternatively, the same routine may be repeatedly executed when the battery discharge signal or the clear instruction from the driver is an input as a power decrease signal indicating that the output power of the motor 50 has decreased. In the latter case, the output power Pd of the motor 50 is compared with a target output power Pd* of the motor 50 instead of with the threshold value Pdref in step S224 in the flowchart of Fig. 14. When the output energy Pd is larger than the target output energy Pd*, the program executes the processing in steps S226 to S238. On the other hand, when the output energy Pd becomes equal to the target output energy Pd*, the program executes steps S230 to S238. This arrangement can reduce the output energy Pd of the motor 50 without changing the torque output to the output shaft 22.

In the drive device 20B of Fig. 12, which is presented as the second embodiment explained above, the auxiliary motor 40 is fixed to the crankshaft 26, which is arranged between the engine 50 and the clutch motor 30. However, similar to another drive device 20C shown in Fig. 15, the engine 50 may be arranged between the clutch motor 30 and the auxiliary motor 40, both of which are connected to the crankshaft 56.

In the drive device 20B of Fig. 12, the clutch motor 30 and the auxiliary motor 40 are separately mounted at different locations of the crankshaft 56. Similar to a drive device 20D shown in Fig. 16, the clutch motor and the auxiliary motor may be integrally connected to each other. A clutch motor 30D of the drive device 20D includes an outer rotor 32D connecting the crankshaft 56 and an inner rotor 34 connected to the output shaft 22. Three-phase coils 36 are mounted on the inner rotor 34, and permanent magnets 35D are arranged on the outer rotor 32D such that the outer surface and the inner surface thereof have different magnetic poles. An auxiliary motor 40D includes the outer rotor 32D of the clutch motor 30D and a stator 43 with three-phase coils 44 attached thereto. In this structure, the outer rotor 32D of the clutch motor 30D acts as a rotor of the auxiliary motor 40D.

In the drive device 20D, the voltage applied to the three-phase coils 36 on the inner rotor 34 is controlled with respect to the inner surface magnetic pole of the permanent magnets 35D attached to the outer rotor 32D. This allows the clutch motor 30D to operate in the same manner as the clutch motor 30 of the drive device 20B shown in Fig. 12. The voltage applied to the three-phase coils 44 on the stator 43 is controlled with respect to the outer surface magnetic pole of the permanent magnets 35D attached to the outer rotor 32D. This allows the auxiliary motor 40D to operate in the same manner as the auxiliary motor 40 of the driving device 20B. The torque control routine of Fig. 13 and the motor stop time torque control routine of Fig. 14 are also applicable to the driving device 20D shown in Fig. 16, which accordingly perform the same operations and exert the same effects as those of the driving device 20B shown in Fig. 12.

Similar to the drive device 20A shown in Fig. 11, the outer rotor 32D in the drive device 20D of Fig. 16 simultaneously functions as one of the rotors in the clutch motor 30D and as the rotor of the auxiliary motor 40D, effectively reducing the size and weight of the entire output device 20D.

Many other modifications, variations and changes may exist without departing from the spirit of the invention. It is therefore to be clearly understood that the above embodiments are only illustrative.

The gasoline-powered engine is used as the engine 50 in the above drive devices. However, the principle of the invention is applicable to other internal and external combustion engines such as diesel engines, turbine engines and jet engines.

Permanent magnet (PM) type synchronous motors are used for the clutch motor 30 and the auxiliary motor 40 in the above-described drive devices. Other motors such as variable reluctance (VR) type synchronous motors, vernier thrusters, DC motors, induction motors, superconducting motors, and stepping motors can be used for the regenerative operation and the current operation.

The rotating transformer 38, which acts as a The device used for transmitting electric power to the clutch motor 30 may be replaced by a slip ring brush contact, slip ring mercury contact, semiconductor coupling of magnetic energy or the like.

In the above driving devices, transistor inverters are used for the first and second driving circuits 91 and 92. Other examples applicable to the driving circuits 91 and 92 include IGBT (Insulated Gate Bipolar Mode Transistor) inverters, thyristor inverters, voltage PWN (Pulse Width Modulation) inverters, square wave inverters (voltage inverters and current inverters), and resonance inverters.

The battery 94 may comprise Pb cells, NiMH cells, Li cells or the like cells. A capacitor may be used instead of the battery 94.

Although the drive device in the above embodiments is mounted on or in a vehicle, it can be mounted on or in other transportation devices, such as ships and aircraft, as well as on a variety of industrial machines or systems.

The spirit and teaching of the present invention are limited only by the terms of the appended claims.

Claims (11)

1. Drive device for transmitting a force to an output shaft (22), the drive device comprising: A motor (50) having an output shaft (56), a motor drive device for driving the motor (50), a first motor (30; 30A, C, D) comprising a first rotor connected to the output shaft (56) of the motor and a second rotor connected to the output shaft (22), the second rotor being coaxial and relatively rotatable to the first rotor, a power being transmitted between the output shaft (56) of the motor and the output shaft (22) via an electromagnetic connection of the first rotor and the second rotor, a first motor drive circuit (91) for controlling a degree of electromagnetic connection of the first rotor and the second rotor in the first motor (30) and for controlling a rotation of the second rotor relative to the first rotor, a second motor (40; 40A, D) connected to the output shaft (22), and a second motor drive circuit (92) for driving and controlling the second motor (40), marked by a storage battery (94) electrically connected to the first motor (30) and the second motor (40) via the first motor drive circuit (91) and the second motor drive circuit (92), a current sampling signal detecting device for detecting a current sampling signal to provide a current output (Pd) from the engine, a drive circuit control means for reducing the degree of electromagnetic connection of the first rotor with the second rotor in the first motor (30) by subtraction amounts (ΔTc) by controlling the first motor drive circuit (91) in response to a current decrease signal detected by the current decrease signal detection means and for turning on the second motor (40) by controlling the second motor drive circuit (92) to use power stored in the storage battery (94) and to compensate for a decrease in the current transmitted by the first motor (30; 30A, C, D) accompanied by the decrease in the degree of electromagnetic connection, and a motor current reducing means for reducing the current output (Pd) from the motor by the decrease in the degree of electromagnetic connection of the first rotor with the second rotor, which is accompanied by the drive circuit control means, by controlling the motor drive means. 2. Drive device according to claim 1, in which a complex motor (20A) comprises the first motor (30A) and the second motor (40A), and the second rotor of the first motor (30A) and a stator form the second motor (40A). 3. A drive device according to claim 1 or 2, wherein the current reduction signal detecting means comprises means for detecting an engine stop signal for stopping the operation of the engine (50), and wherein the motor current reduction means comprises means for controlling the motor drive means to interrupt the supply of fuel to the engine (50) and to stop the operation of the engine (50) when the drive circuit control means releases the electromagnetic connection of the first rotor with the second rotor in the first motor (30; 30A). 4. Drive device (20B, D) for transmitting a force to an output shaft (22), the drive device comprising: A motor (50) having an output shaft (56), a motor drive device for driving the motor (50), a first motor (30; 30D) comprising a first rotor which is connected to the output shaft (56) of the motor, and a second rotor which is connected to the output shaft (22), wherein the first motor (30; 30D) is coaxial and relatively rotatable to the first rotor, wherein a force is transmitted between the output shaft (56) of the motor and the output shaft (22) via an electromagnetic connection of the first rotor and the second rotor, a first motor drive circuit (91) for controlling a degree of electromagnetic connection of the first rotor and the second rotor in the first motor (30) and for controlling a rotation of the second rotor relative to the first rotor, marked by a second motor (40; 40D) connected to the output shaft (56) of the motor, a second motor drive circuit (92) for driving and controlling the second motor (40), a storage battery (94) electrically connected to the first motor (30B) and the second motor (40; 40D) via the first motor drive circuit (91) and the second motor drive circuit (92), a current take-off signal detecting device for detecting a current take-off signal to reduce a current output from the motor (50), a motor current reduction means for reducing the current output (Pd) from the motor (50) by subtraction amounts (ΔPd) by controlling the motor drive means in response to a current take-off signal detected by the current take-off signal detecting means, and a drive circuit control means for turning on the first motor (30) and the second motor (40; 40D) by controlling the first motor drive circuit (91) and the second motor drive circuit (92) to use power stored in the storage battery (94) and to compensate for the decrease in the current output (Pd) from the motor (50) accompanied by the motor current reducing means. 5. Drive device according to claim 4, in which a complex motor (20D) comprises the first motor (30D) and the second motor (40D), and the first rotor of the first motor (30D) and a stator form a second motor (40D). 6. A drive device according to claim 4 or 5, wherein the drive circuit control means comprises means for controlling the first motor drive circuit (91) to allow the first motor (30; 30D) to compensate for a decrease in the rotational speed of the output shaft (56) of the motor under the decrease in the current output from the motor (50), and for controlling the second motor drive circuit (92) to allow the second motor (40; 40D) to compensate for a decrease in the torque under the decrease in the current output (Pd) from the motor. 7. A drive device according to any one of claims 4 to 6, wherein the current take-off signal detecting means comprises means for detecting an engine stop signal for stopping the operation of the engine (50), and wherein the engine current reducing means comprises means for controlling the engine drive means to stop the supply of fuel to the engine (50) and to stop the operation of the engine (50) when the current output from the engine becomes zero. 8. A method for controlling a drive device for transmitting a force to an output shaft (22), wherein the Procedure which includes steps: (a) providing a motor (50) having an output shaft (56), a motor drive device for driving the motor (50), a first motor (30; 30A, C, D) comprising a first rotor connected to the output shaft (56) of the motor and a second rotor connected to the output shaft (22), the first motor (30; 30A, C, D) being coaxial and rotatable relative to the first rotor, a force being transmitted between the output shaft (56) of the motor and the output shaft (22) via an electromagnetic connection of the first rotor and the second rotor, a second motor (40; 40A, D) connected to the output shaft (22), and a storage battery (94) electrically connected to the first motor (30; 30A, C, D) and the second motor (40; 40A, D) via the first motor drive circuit (91) and the second motor drive circuit (92), characterized by the steps: (b) detecting a current decrease signal to reduce the current output from the motor (50), (c) controlling the first motor (30) in response to the current take-off signal to reduce the degree of electromagnetic connection of the first rotor with the second rotor in the first motor (30) by subtraction amounts (ΔTc), (d) controlling the second motor (40) to enable the second motor to use power stored in the storage battery (94) and to compensate for a decrease in the current transmitted by the first motor (30) accompanied by the decrease in the degree of electromagnetic connection, and (e) controlling the motor drive means to decrease the current output from the motor (50) with the decrease in the degree of electromagnetic connection of the first rotor with the second rotor accompanied by step (c). 9. The method of claim 8, wherein the detected current draw signal represents an engine stop signal to stop operation of the engine (50), wherein step (e) further comprises the step of controlling the engine drive means to interrupt a supply of fuel to the engine (50) and to terminate operation of the engine (50) when the electromagnetic connection of the first rotor to the second rotor in the first engine (30; 30A, C, D) has been reduced to a release position in response to the engine stop signal. 10. Method for controlling a drive device for transmitting a force to an output shaft (22), the method comprising the steps: (a) providing a motor (50) having an output shaft (56), a motor drive device for driving the motor (50), a first motor (30; 30D) comprising a first rotor, which is connected to the output shaft (56) of the motor (50), and a second rotor, which is connected to the output shaft (22), wherein the second rotor is coaxial and relatively rotatable to the first rotor, wherein a force is transmitted between the output shaft (56) of the motor and the output shaft (22) via an electromagnetic connection of the first rotor and the second rotor, a second motor (40; 40D) connected to the output shaft (56) of the motor, and a storage battery (94) electrically connected to the first motor (30; 30D) and the second motor (40; 40D) via the first motor drive circuit (91) and the second motor drive circuit (92), characterized by the steps: (b) detecting a current decrease signal to reduce the current output from the motor (50), (c) controlling the motor drive device in response to the Current take-off signal for reducing the current output from the motor (50) by subtraction amounts (ΔPd), and (d) controlling the first motor (30; 30D) and the second motor (40) to enable the first motor (30) and the second motor (40) to use power stored in the storage battery (94) and to compensate for the decrease in power output from the motor (50) accompanied by step (c). 11. The method of claim 10, wherein step (d) further comprises the steps of: (e) controlling the first motor (30; 30D) to enable the first motor to compensate for a decrease in the speed of the output shaft (56) of the motor corresponding to the decrease in the current output from the motor (50), and (f) controlling the second motor (40; 40D) to allow the second motor (40) to compensate for a decrease in torque corresponding to the decrease in current output from the motor (50).