JP2007238018A - Driving force control device for electric motor type four-wheel-drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent two-wheel drive from being continued resulting from low response in switching to four-wheel drive when the switching between the two-wheel drive and the four-wheel drive is frequently repeated. <P>SOLUTION: In the case that an engine driven front wheel slips at time t1, a motor driven rear wheel is driven by 4WD field current, and, the slip of the front-wheel drive is cleared at time t2, from the time t2 to the time t3 after a set time Δ elapsed, a generator and an electric motor are pre-excited. In the Δt, the generator and the electric motor is pre-excited by Ifh=the pre-excitation field current and Ifm=pre-excitation field current. When the switching request from the two-wheel drive to the four-wheel drive occurs in the Δt, the excitation for the generator and the electric motor is promptly completed from the pre-excitation state, and the four-wheel drive response is improved. Thus, under the environment where the switching between the two-wheel and the four wheel drive is repeated, the switching to the four-wheel drive is promptly completed, and the two-wheel drive can be prevented from being continued. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, one of the front and rear wheels is driven by a main power source such as an internal combustion engine (engine), and the other wheel is driven by power from an electric motor that responds to power generated by a generator coupled to the main power source. In particular, the four-wheel drive vehicle is appropriately driven by driving the electric motor with electric power generated by applying a power generation load to the generator when a drive slip of the main drive wheel occurs. The present invention relates to a driving force control technique for an electric motor type four-wheel drive vehicle.

  In addition to main drive wheels driven by power from a main power source such as an internal combustion engine (engine), an electric motor driven by power from an electric motor that responds to power generated by a generator coupled to the main power source Conventionally, as an electric motor type four-wheel drive vehicle including a drive wheel, there is a vehicle as described in Patent Document 1, for example.

  This vehicle drives the front two wheels (or the rear two wheels) with an engine, and the rear two wheels (or the front two wheels) can be driven by an electric motor. To directly drive the electric motor.

When controlling the generator and electric motor during four-wheel drive, the surplus torque that causes the drive slip of the main drive wheel is determined by comparing the road surface reaction force of the main drive wheel and the engine torque. By driving the electric motor with the electric power generated by applying the corresponding power generation load to the generator and driving the corresponding wheel with the electric motor under the situation where the main driving wheel is driven to slip, this and the main driving wheel Let the four wheels run.
JP 2004-215499 A

Therefore, unless the main drive wheels are in a driving slip condition, the generator cannot apply a power generation load, and there is no power generated from this. Therefore, the electric motor is not driven, so the vehicle is a two-wheel drive using only the main drive wheels. Drive driving will be performed.
When the main drive wheel slips from this situation, the corresponding wheel is driven via the electric motor with the power generated by applying the power generation load corresponding to the surplus torque to the generator, and four-wheel drive running is performed. Make it.

  By the way, when switching from the two-wheel drive to the four-wheel drive, both the generator and the electric motor are excited by energizing the field coil from the no-load state, and the generator performs power generation according to the power generation load. Since the electric motor outputs torque according to the energization (excitation force) to the field coil based on the power of the motor, switching from two-wheel drive to four-wheel drive is performed, so two-wheel drive to four-wheel drive There was a problem that the switching response to was bad.

  This poor four-wheel drive response is contrary to the rapid changeover from four-wheel drive to two-wheel drive in a road environment where switching between two-wheel drive and four-wheel drive is frequently repeated. Since the switch from 2-wheel drive to 4-wheel drive is not completed quickly, 2-wheel drive is required before the switch to 4-wheel drive is completed. Sometimes.

  In addition, with the recent increase in vehicle speed in the four-wheel drive vehicle speed range, it is not possible to switch to four-wheel drive travel after long distance travel after the four-wheel drive command is issued, and although it should be driven by four wheels, long distance As a result, the two-wheel drive is forced over, and the above problem becomes more prominent, and there is a concern that the rough road running performance may be further deteriorated.

In order to solve this problem, it is determined that the road environment is frequently switched between two-wheel drive and four-wheel drive, and the road is determined to be a low μ road, and the four-wheel drive state is maintained until the main power source engine is stopped. It may be fixed.
However, in this case, since the four-wheel drive driving is continued ignoring the changing road conditions, it is inevitable that the fuel consumption deteriorates due to the four-wheel drive driving even under the road conditions where the two-wheel driving is possible. .
This problem is a problem that cannot be overlooked because the generator and the electric motor have recently been increased in capacity, and the drive energy of the generator is large.

  The present invention proposes a measure for improving the four-wheel drive response of an electric motor type four-wheel drive vehicle from the viewpoint that all of the above problems are caused by poor switching response from two-wheel drive to four-wheel drive. Therefore, an object is to solve the above-mentioned problems.

For this purpose, the driving force control apparatus for an electric motor type four-wheel drive vehicle according to the present invention has the following configuration as described in claim 1.
First of all, the premise of the electric motor type four-wheel drive vehicle is
A main drive wheel driven by power from a main power source;
An electric motor drive wheel driven by power from an electric motor that responds to power generated by a generator coupled to the main power source,
When a driving slip state of the main driving wheel is detected based on a wheel speed difference between the main driving wheel and the electric motor driving wheel, the electric motor generates electric power by applying a power generation load to the generator via the electric motor. Four-wheel drive is performed by driving electric motor drive wheels.

The driving force control device of the present invention is such an electric motor type four-wheel drive vehicle,
Even when the driving slip state of the main driving wheel is not detected, at least one of the field of the generator and the electric motor is maintained in a pre-excited state during the set time.

According to the driving force control apparatus of the present invention,
Even when the driving slip state of the main driving wheel is not detected, to keep at least one of the field of the generator and the electric motor in the pre-excited state during the set time,
When there is a request to switch from two-wheel drive to four-wheel drive during this set time and the field of the generator and electric motor is excited, at least one of these excitations is from the pre-excited state. It will be completed quickly, and the response to switching from 2-wheel drive to 4-wheel drive will be faster.

  For this reason, in a road environment where switching between two-wheel drive and four-wheel drive is frequently repeated, switching from two-wheel drive to four-wheel drive is performed quickly, as is switching from four-wheel drive to two-wheel drive. When completed, the conventional problem described above that two-wheel drive running may continue under the road environment can be solved.

  In addition, due to the rapid response of the four-wheel drive, the recent increase in the vehicle speed range of the four-wheel drive has switched to four-wheel drive within a relatively short distance, and the two-wheel drive is supposed to be driven by four-wheel drive. Therefore, the above-mentioned problem solving can be further ensured, and further improvement in rough road running performance can be realized.

Furthermore, once it is determined that the four-wheel drive should be driven, the generator and the electric motor are not used during the set time even after the drive slip of the main drive wheel is resolved, without relying on the measure to continue the four-wheel drive state until the main power source is stopped. Because the above-mentioned effect was achieved by the measure of keeping the field of
There is no inconvenience of performing four-wheel drive traveling even under road conditions where two-wheel drive traveling is possible, and deterioration of fuel consumption due to unnecessary four-wheel drive traveling can be avoided.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 schematically shows a drive system of an electric motor type four-wheel drive vehicle including a drive force control device according to an embodiment of the present invention.
In this embodiment, this vehicle is a front engine / front wheel drive vehicle (F / F vehicle) driven by an engine (internal combustion engine) 2 with the left and right front wheels 1L and 1R as the main power source, and the left and right rears. A so-called electric motor type four-wheel drive vehicle in which the wheels 3L and 3R can be driven by a rear wheel drive motor 4, which is an electric motor, as required.

As usual, the engine 2 is assumed to increase its output according to the degree to which the driver depresses an accelerator pedal (not shown).
The engine 2 is drivably coupled to the left and right front wheels (main drive wheels) 1L and 1R via a transaxle in which the automatic transmission 5 and the differential gear device 6 are configured as an integral unit. It is assumed that the vehicle is transmitted to the left and right front wheels 1L and 1R via the differential gear device 6 and used for traveling of the vehicle.

  Next, a rear wheel drive system by the electric motor 4 will be described. This includes a dedicated generator 8 driven via an endless belt 7 by a part of the output torque of the engine 2, and the generator 8 The engine is driven at a rotational speed obtained by multiplying the rotational speed of 2 by the belt pulley ratio, and a load is applied to the engine 2 in accordance with the field current Ifh applied to the field current line 8a adjusted by the four-wheel drive controller 9. Electric power is generated according to the torque.

The electric power generated by the generator 8 is supplied to the rear wheel drive motor 4 through the relay 11 through the power line 10.
The relay 11 is also controlled by the command from the controller 9 when the power line 10 is cut off when the generator 8 becomes poorly controlled, or when the rear wheel drive is unnecessary and the controller 9 does not apply a power generation load to the generator 8. Since there is some power generation by the permanent magnet, the power line 10 is cut off so as not to be supplied to the motor 4.

  The drive shaft of the rear wheel drive motor 4 is coupled to the differential gear device 14 of the left and right rear wheels (electric motor drive wheels) 3L and 3R via the speed reducer 12 and the 4WD clutch 13 incorporated therein, and the output of the motor 4 If the torque is increased by the gear ratio by the speed reducer 12 and the 4WD clutch 13 is engaged by the electric power from the clutch engagement power line 13a, this increased torque is distributed and output to the left and right rear wheels 3L, 3R by the differential gear device 14. To be done.

The four-wheel drive controller 9 also controls the engagement / release of the 4WD clutch 13 and the rotation direction / drive torque of the electric motor 4.
In controlling the electric motor 4, the controller 9 obtains the motor torque command value of the electric motor 4 corresponding to the target driving force of the left and right rear wheels (electric motor driving wheels) 3L, 3R determined according to the vehicle operating state, and calculates the field current. By adjusting the field current Ifm from the line 4a to the electric motor 4, the motor drive torque is controlled to coincide with this command value, and the motor rotation direction is controlled by the direction of the field current Ifm.

In addition to inputting the signal from the four-wheel drive switch 21 to the four-wheel drive controller 9 for performing the above-described control of the motor 4, the generator 8, the relay 11, and the 4WD clutch 13,
Signals from the wheel speed sensor group 22 for individually detecting the wheel speeds (front wheel speeds) V _WFL and V _WFR of the left and right front wheels 1L and 1R and the wheel speeds (rear wheel speeds) V _WRL and V _WRR of the left and right rear wheels 3L and 3R When,
A signal from the motor rotation sensor 23 for detecting the rotational speed Nm of the rear wheel drive motor 4,
A signal from an accelerator opening sensor 25 that detects an accelerator pedal depression amount (accelerator opening) APO is input.

The four-wheel drive controller 9 determines whether the four-wheel drive is necessary and automatically performs the motor four-wheel drive while the driver is turning on the four-wheel drive switch 21 as described later.
While the driver is turning off the four-wheel drive switch 21, the two-wheel drive by only the engine drive of the front two wheels is continuously performed.

Hereinafter, basic four-wheel drive control performed by the controller 9 will be described.
First, by the process shown in FIG. 2, surplus torque of the engine 2 that causes the driving (acceleration) slip of the front wheels 1L and 1R that are the main driving wheels (engine driving wheels) is calculated.
In step S1, from the average front wheel speed Vwf that can be obtained from the front wheel speeds V _WFL and V _WFR detected by the wheel speed sensor group 22, the average after that that can be obtained from the rear wheel speeds V _WRL and V _WRR that are also detected by the wheel speed sensor group 22 By subtracting the wheel speed Vwr, the driving (acceleration) slip amount ΔVf of the left and right front wheels 1L and 1R as the main driving wheels is obtained.

In the next step S2, it is determined whether or not a driving slip has occurred depending on whether or not the driving slip amount ΔVf of the left and right front wheels 1L and 1R is a predetermined value, for example, 3 km / h or more.
When it is determined that the drive slip amount ΔVf is less than 3 km / h, the drive slip is not generated and the control is terminated as it is because there is no surplus of engine output.

When a drive slip is generated in step S2, where the drive slip amount ΔVf is determined to be 3 km / h or more, it is necessary to suppress the excess torque of the engine that generates the drive slip of the front wheels 1L, 1R, that is, the drive slip in step S3. The absorption torque T (ΔVf) is calculated by T (ΔVf) = K1 × ΔVf.
K1 is a gain obtained through experiments or the like.

In the next step S4, the current load torque Tg of the generator 8 is obtained. In step S5, the current generator load torque Tg and the surplus torque T (ΔVf) are added together to obtain the target power generation load of the generator 8. Find the torque Th.
In step S6, the motor speed VSP that can be obtained from the wheel speeds V _WFL , V _WFR , V _WRL , V _WRR is a motor overspeed vehicle speed that is a lower limit value of the vehicle speed range in which the motor 4 is overrotated when the 4WD clutch 13 is engaged ( For example, check whether it is less than 30km / h).

If the vehicle speed VSP is equal to or higher than the motor overspeed vehicle speed, the motor 4 is overrotated and its durability is lowered. Therefore, the control is terminated as it is so that the four-wheel drive is not performed, but the vehicle speed VSP is less than the motor overspeed vehicle speed. Then, in step S7, the maximum load torque Thmax of the generator 8 is obtained.
Next, in step S8, it is checked whether or not the target power generation load torque Th (step S5) of the generator 8 is greater than or equal to the maximum load torque Thmax, and if so, the limit in which the target power generation load torque Th can be realized by setting Th = Thmax in step S9. If Th <Thmax, the control is terminated and the target power generation load torque Th is set to the value as obtained in step S5.

In FIG. 2, the method of obtaining the target power generation load torque Th of the generator 8 only when the engine drive wheels 1L and 1R generate a drive slip has been described.
Even if the engine drive wheels 1L and 1R may cause a drive slip or when the engine drive wheels 1L and 1R are in a low speed state below a predetermined level, the target power generation load torque Th of the generator 8 is driven in order to realize the four-wheel drive of the electric motor. According to

The controller 9 controls the generator 8 and the motor 4 by the control program of FIG. 3 based on the target power generation load torque Th of the generator 8 obtained as described above.
In step S11, it is checked whether or not there is a power generation request depending on whether or not the target power generation load torque Th of the generator 8 is positive.
If there is no power generation request, the control is terminated, so that the power generation load of the generator 8 is not applied to the engine 2, and the 4WD clutch 13 is in a released state.
If there is a power generation request, in step S12, the target motor field current Ifm is calculated from the motor rotation speed Nm based on the scheduled map.
Although not shown, at the same time, when the input / output rotational speeds of the 4WD clutch 13 coincide with each other, the 4WD clutch 13 is engaged so that the rotation of the motor 4 can be transmitted to the rear wheels 3L and 3R.

Here, as shown in step S12, the target motor field current Ifm with respect to the rotational speed Nm of the motor 4 is set to a constant predetermined current value when the motor rotational speed Nm is equal to or smaller than the predetermined rotational speed, and the motor rotational speed beyond that is determined. When the number is reached, the field current Ifm of the motor 4 is reduced by a known field weakening control method.
The reason for this is that when the motor 4 rotates at a high speed, the motor torque decreases due to the increase of the motor back electromotive force E. Therefore, when the motor rotation speed Nm exceeds a predetermined value, the field current Ifm of the motor 4 is decreased and reversed. This is because the current flowing through the motor 4 is increased by reducing the electromotive voltage E so that the required motor torque Tm can be obtained.

Next, at step S13, the back electromotive force E of the motor 4 is calculated from the target motor field current Ifm and the rotation speed Nm of the motor 4 obtained as described above, based on a predetermined map.
Further, in step S14, a corresponding motor torque command value tTm is calculated based on the power generation load torque Th, and a target motor field current Ifm corresponding to the motor torque command value tTm is commanded to the electric motor 4, so that the electric motor 4 outputs a torque corresponding to the motor torque command value tTm.

In step S15, a target armature current Ia that is a function of the motor torque command value tTm and the target motor field current Ifm is calculated.
Thereafter, in step S16, the target voltage V of the generator 8 is obtained from the target armature current Ia, the total resistance R, and the counter electromotive voltage E by calculation of V = Ia × R + E.
The controller 9 feedback-controls the field current Ifh of the generator 8 so that the generated voltage of the generator 8 becomes the target voltage V thus obtained.

Apart from the control of the generator 8 and the electric motor 4, the four-wheel drive controller 9 executes the control program of FIG. 4 to perform pre-excitation control of the generator 8 and the electric motor 4 as follows.
First, in step S21, the left and right front wheel 1L, 1R (main drive wheel) obtained by subtracting the average rear wheel speed Vwr from the average front wheel speed Vwf is determined according to whether the drive slip amount ΔVf is a predetermined value, for example, 3 km / h or more. It is determined whether or not a driving slip of the front wheels 1L and 1R (main driving wheels) has occurred.

If it is determined in step S21 that the left and right front wheels 1L and 1R have generated a drive slip, in step S22, the above-described normal four-wheel drive control is executed by the processing after step S2 in FIG. 2 and the processing in FIG. And
Each time this loop is selected, in step S23, the period from the current time until the moment when the set time Δt elapses is updated as the pre-excitation time Δt of the generator 8 and the electric motor 4 and is continuously stored.

  If it is determined in step S21 that driving slips on the left and right front wheels 1L and 1R are no longer generated, the control is advanced to step S24, so that the driving slip of the left and right front wheels 1L and 1R is generated in the period stored in the previous step S23. The period from the time when it stops to the moment when the set time Δt elapses is determined as the pre-excitation period Δt of the generator 8 and the electric motor 4.

In step S24, it is checked whether or not the pre-excitation period Δt has ended. Until the pre-excitation period Δt ends, the generator 8 and the electric motor 4 are pre-excited in step S25.
Here, the pre-excitation of the generator 8 and the electric motor 4 means that the generator 8 and the electric motor 4 do not drive the left and right rear wheels 3L and 3R, but immediately the left and right rear wheels 3L when the field currents Ifh and Ifm increase. , It means that the fields of the generator 8 and the electric motor 4 are set to a slight excitation state in advance so that the switching from the two-wheel drive to the four-wheel drive is immediately executed after starting to drive the 3R. ,
The field currents Ifh and Ifm for the slightly excited state are determined in advance for each traveling condition of the vehicle by experiments and the like. In step S24, the field currents Ifh and Ifm for the slightly excited state are generated by the generator. 8 and the electric motor 4 are commanded to perform respective pre-entrainment.

  When it is determined in step S24 that the pre-excitation period Δt has ended, the pre-excitation of the generator 8 and the electric motor 4 is ended in step S26, and this pre-excitation ends due to the disappearance of the field currents Ifh and Ifm. Carry out.

As shown in FIG. 5, the effect of the present embodiment is as follows. The front wheel drive slip amount ΔVf exceeds a predetermined value (for example, 3 km / h) at the instant t1, and the processing after step S2 in FIG. 2 and the processing in FIG. In normal four-wheel drive control (4WD field current is shown in FIG. 5), the case where the front wheel drive slip amount ΔVf becomes less than a predetermined value (for example, 3 km / h) at the instant t2 is added.
A period from the time t2 when the driving slip of the front wheel is eliminated to an instant t3 when the set time Δt elapses is set as a pre-excitation period for the generator 8 and the electric motor 4 (step S23). During this pre-excitation period Δt, the generator 8 and The above-described pre-excitation (step S25) of the electric motor 4 is performed by Ifh = pre-excitation field current and Ifm = pre-excitation field current (in FIG. 5, these are shown as the same value for convenience).

In other words, to maintain the field of the generator 8 and the electric motor 4 in the pre-excited state during the set time Δt even after the instant t2 when the front wheel drive slip is no longer detected.
When there is a request to switch from two-wheel drive to four-wheel drive during this set time Δt and the fields of the generator 8 and the electric motor 4 are excited, this excitation is from the pre-excited state. It will be completed quickly, and the response to switching from 2-wheel drive to 4-wheel drive will be faster.

  For this reason, in a road environment where switching between two-wheel drive and four-wheel drive is frequently repeated, switching from two-wheel drive to four-wheel drive is performed quickly in the same way as switching from four-wheel drive to two-wheel drive. When completed, the conventional problem described above that two-wheel drive running may continue under the road environment can be solved.

Also, due to the above-mentioned speeding up of the four-wheel drive response, the recent increase in vehicle speed in the four-wheel drive vehicle speed range has changed to four-wheel drive within a relatively short mileage, and two-wheel drive should be driven. The distance for which wheel driving is forced is shortened, so that the above problem can be solved more reliably, and further improvement in rough road running performance can be realized.
In the present embodiment, the case where both the field of the generator 8 and the electric motor 4 are maintained in the pre-excited state has been described, but only one of the field of the generator 8 and the electric motor 4 is in the pre-excited state. You may make it keep.
However, in this case, depending on the running state, the same effect as in the above embodiment can be obtained by applying pre-enhancement to those who take time by shifting from the two-wheel drive state to the four-wheel drive state. Can be achieved.

FIG. 6 is a pre-excitation control program similar to FIG. 4, showing a driving force control apparatus according to another embodiment of the present invention.
In FIG. 6, steps for performing the same processing as in FIG. 4 are denoted by the same reference numerals. In this embodiment, the pre-set time Δt is made variable as follows.

  That is, when a driving slip occurs in which the driving slip amount ΔVf of the left and right front wheels 1L, 1R (main driving wheels) is determined to be a predetermined value, for example, 3 km / h or more in step S21, the ease of driving slip is checked in step S31.

The ease of driving slip can be determined by the following physical quantities.
As shown in FIG. 7, at the instant t1, the front wheel drive slip amount ΔVf becomes a predetermined value (for example, 3 km / h) or more, and in the normal four-wheel drive control (the 4WD field current is shown in FIG. 7), the instant t2 The front wheel drive slip amount ΔVf becomes less than a predetermined value (for example, 3 km / h), and then the front wheel drive slip amount ΔVf again becomes a predetermined value (for example, 3 km / h) again at the instant t3. In the case where the front wheel drive slip amount ΔVf becomes less than a predetermined value (for example, 3 km / h) at the instant t4,
Based on the maximum value of the front wheel drive slip amount ΔVf and / or the number of occurrences of the drive slip during pre-excitation control, or the magnitude of both, and the time integral value of the front wheel drive slip amount ΔVf, it is considered that the larger the value, the easier the drive slip. be able to.

In step S31, it is checked whether or not the driving slip is easy depending on whether or not the driving slip is more than a set value.
If the ease of driving slip is not great, in step S32, the set time Δt for pre-excitation is added to the previous value Δt (previous value) by a short value, for example, 0.01 seconds, and this 0.01. Set the length to be longer in seconds,
If the driving slip is easy to perform, in step S33, the pre-set time Δt is added to the previous value Δt (previous value), for example, 0.02 seconds, and then 0.02 seconds. Determine to be longer.
Accordingly, in the present embodiment, the pre-excitation set time Δt changes so as to increase as the front wheel drive slip amount ΔVf and / or the number of front wheel drive slip occurrences during the pre-excitation control of the generator 8 and the electric motor 4 increases. It becomes.

In step S23 after the set time Δt for pre-excitation is determined as described above, the period from the present time to the moment when the set time Δt elapses is updated as the pre-excitation time Δt for the generator 8 and the electric motor 4. Continue to memory.
In the next step S34, the setting time Δt for pre-excitation determined as described above in step S32 or step S33 is stored as Δt (previous value) used in the next setting of Δt (step S32 or step S33). .

  In the last step S22, in response to the determination of the occurrence of drive slip in step S21, normal four-wheel drive control is executed by the processing after step S2 in FIG. 2 and the processing in FIG.

If it is determined in step S21 that the driving slips on the left and right front wheels 1L and 1R are no longer generated, the control loops off from the loop passing through step S31 and the control proceeds to step S24, where the driving slips on the left and right front wheels 1L and 1R occur. Whether or not the pre-excitation period has ended is checked based on whether or not the set time Δt has elapsed since the point in time (instantaneous t2 and t4 in FIG. 7).
Until the pre-excitation period Δt ends, the generator 8 and the electric motor 4 are pre-excited in step S25,
After the pre-excitation period Δt ends, the pre-excitation of the generator 8 and the electric motor 4 ends in step S26.

When it is determined in step S24 that the pre-excitation period has not yet ended, it is determined in step S21 that a driving slip has occurred on the left and right front wheels 1L and 1R, that is, for example, between instants t2 and t3 in FIG. Thus, if the drive slip of the left and right front wheels 1L and 1R occurs again before the set time Δt elapses from the time t2 when the drive slip of the left and right front wheels 1L and 1R no longer occurs (at the pre-excitation period), At t3, step S21 advances the control to step S31 to recalculate the pre-set time Δt.
As shown in FIG. 7, after the instant t4, the left and right front wheels 1L, 1R are driven (during the pre-excitation period) from the time t4 when the driving slip of the left and right front wheels 1L, 1R no longer occurs until the set time Δt elapses. If drive slip does not occur, the period from time t4 to time t5 after the set time Δt is determined as the pre-excitation period Δt for the generator 8 and the electric motor 4.

  The operation and effect of the present embodiment will be described below with reference to FIG. 7. The period until the set time Δt elapses from the time t2 and t4 when the front wheel drive slip is eliminated is the pre-excitation period of the generator 8 and the electric motor 4. If the front wheel drive slip does not occur during this pre-excitation period Δt (step S23), the above-described pre-excitation of the generator 8 and the electric motor 4 (step S25) becomes Ifh = pre-excitation field current and Ifm = preexcitation field current (in FIG. 7, for convenience, these are shown as the same value).

In other words, even after the front wheel drive slip is eliminated (instant t2, t5), during the set time Δt, if the front wheel drive slip does not occur, the field of the generator 8 and the electric motor 4 is kept in the pre-excited state.
During the set time Δt, as shown at the moment t3 in FIG. 7, there is a request to switch from two-wheel drive to four-wheel drive due to the occurrence of front wheel drive slip, and when the fields of the generator 8 and the electric motor 4 are excited, Since excitation is from the pre-excited state, it is completed quickly, and the switching response from two-wheel drive to four-wheel drive becomes faster.

  For this reason, in a road environment where switching between two-wheel drive and four-wheel drive is frequently repeated, switching from two-wheel drive to four-wheel drive is performed quickly in the same way as switching from four-wheel drive to two-wheel drive. When completed, the conventional problem described above that two-wheel drive running may continue under the road environment can be solved.

  Also, due to the above-mentioned speeding up of the four-wheel drive response, the recent increase in vehicle speed in the four-wheel drive vehicle speed range has changed to four-wheel drive within a relatively short mileage, and two-wheel drive should be driven. The distance for which wheel driving is forced is shortened, so that the above problem can be solved more reliably, and further improvement in rough road running performance can be realized.

In addition, in the present embodiment, as described above, the pre-set time Δt is increased as the front wheel drive slip amount and / or the number of drive slip occurrences during the pre-excitation control of the generator 8 and the electric motor 4 increases ( Step S32, step S33),
The pre-excitation period length is appropriate according to the ease of drive slip, and the pre-excitation period is too long even though the road is high, resulting in deterioration of the battery charge state and fuel consumption deterioration due to increased energy loss. Can be avoided and
Even though the road is a low μ road, it is possible to avoid the adverse effect that the pre-enhancement period is too short and the above-mentioned effects cannot be achieved.

FIG. 8 is a pre-excitation control program similar to FIG. 6, showing a driving force control apparatus according to still another embodiment of the present invention.
In FIG. 8, steps for performing the same processing as in FIG. 6 are denoted by the same reference numerals. In this embodiment, the pre-excitation set time Δt is made variable as in FIG. Set the upper limit for the set time Δt.

Therefore, in this embodiment, as shown in FIG. 8, steps S41 and S42 are added to the pre-excitation control program of FIG.
In step S41, which is selected after setting the pre-excitation set time Δt in step S32 or step S33, it is checked whether or not the pre-excitation set time Δt exceeds an upper limit value (for example, 30 seconds).

If it is determined in step S41 that the pre-excitation set time Δt has exceeded the upper limit value (eg, 30 seconds), the pre-excitation set time Δt is set to the upper limit value (eg, 30 seconds) in step S42, and this upper limit is set. After limiting so as not to exceed, control proceeds to step S23.
When it is determined in step S41 that the pre-excitation set time Δt does not exceed the upper limit value (for example, 30 seconds), step S42 is skipped and control is advanced to step S23, so that it is determined in step S32 or step S33. The set time Δt for preliminary excitation is used as it is.

According to the present embodiment, in addition to the same effects as the embodiment shown in FIG. 6 and FIG. 7, the pre-excitation set time Δt does not exceed the upper limit (for example, 30 seconds),
It is possible to avoid adverse effects such as the pre-excitation of the generator 8 and the electric motor 4 being performed indefinitely for a long time so that the battery storage state is remarkably deteriorated or the fuel consumption is greatly deteriorated due to an extreme increase in energy loss.

FIG. 9 is a pre-excitation control program similar to FIG. 6, showing a driving force control apparatus according to still another embodiment of the present invention.
In FIG. 9, steps for performing the same processing as in FIG. 6 are denoted by the same reference numerals. In this embodiment, step S51 is provided instead of step S31 in FIG. Δt is changed.

That is, in step S51, whether the vehicle speed VSP is higher than the set vehicle speed VSP1 or not is checked based on whether the vehicle speed VSP is equal to or higher than the set vehicle speed VSP1.
While it is determined that the vehicle speed is low in step S51, in step S32, the pre-excitation set time Δt is added to the previous value Δt (previous value) by a short value, for example, 0.01 seconds, and this 0.01 seconds. We decided to make it longer,
While it is determined in step S51 that the vehicle speed is high, in step S33, the pre-excitation set time Δt is added to its previous value Δt (previous value), for example, 0.02 seconds, and this 0.02 seconds. Determine to be longer.
Accordingly, in the case of the present embodiment, the set time Δt for pre-excitation changes so as to increase as the vehicle speed increases.

According to this embodiment, in addition to the same effects as the embodiment shown in FIGS. 6 and 7, the pre-excitation set time Δt is increased as the vehicle speed increases.
As the vehicle speed increases, the tendency of the two-wheel drive mileage to become longer due to the four-wheel drive response delay can be alleviated, and the above-described effects can be reliably achieved even at high vehicle speeds.

FIG. 10 is a pre-excitation control program similar to FIG. 4, showing a driving force control apparatus according to still another embodiment of the present invention.
In FIG. 10, steps for performing the same processing as in FIG. 4 are denoted by the same reference numerals. In this embodiment, step S61 is inserted between step S21 and step S24 in FIG. When it is determined that the road surface is easy to drive slip, such as a gravel road, the generator 8 and the electric motor 4 are pre-excited even if no drive slip occurs.

That is, when it is determined in step S21 that no front wheel drive slip has occurred, in step S61, depending on whether or not the wheel speed fluctuation is greater than or equal to the rough road judgment fluctuation range, the road surface is prone to drive slip such as a snowy road or a gravel road. Check if it exists.
Incidentally, as can be seen from FIG. 11 which shows the change over time of the average front wheel speed V _WF and the average rear wheel speed V _WR , the wheels on the pavement surface are as seen in the change over time of the wheel speeds V _WF and V _WR until the instant t1. The speed changes smoothly with almost no fluctuation, and on road surfaces such as snowy roads and gravel roads where driving slip is likely to occur, the wheel speed is large as seen in the temporal changes of the wheel speeds V _WF and V _WR after the instant t1. It changes while fluctuating.
In view of this situation, in step S61, it is checked whether or not the road surface is prone to drive slip depending on whether or not the wheel speed fluctuation is greater than or equal to the rough road judgment fluctuation width.

While it is determined in step S61 that the wheel speed fluctuation is less than the rough road determination fluctuation width, the control is advanced to step S24 and subsequent steps, and the pre-excitation control of the generator 8 and the electric motor 4 is performed as described above with reference to FIG. Do, but
While it is determined in step S61 that the wheel speed fluctuation is greater than or equal to the rough road determination fluctuation range, the control proceeds to step S25, and the generator 8 is continuously continued without depending on the end of the pre-excitation period in step S24. And the electric motor 4 is pre-excited.

Therefore, according to the present embodiment, even if there is no front wheel drive slip (step S21), the wheel speed fluctuation of the front wheel and / or the rear wheel is greater than or equal to the rough road determination fluctuation width, and the snow road or gravel road On the road surface where driving slip is likely to occur, the fields of the generator 8 and the electric motor 4 are kept in the pre-excited state,
In case of sudden driving slip even though you are driving carefully on a road surface that is easy to drive slip, you can quickly complete the transition to 4-wheel drive and improve the rough road running performance in this case be able to.

  Each of the above-described embodiments can be used in combination to achieve the corresponding functions and effects.

  Further, the pre-excitation of the generator 8 and the electric motor 4 may be performed by the electric power from the battery, respectively, but the electric motor 4 is pre-excited by the generated electric power generated by the pre-excitation of the generator 8. By doing so, it is not necessary to cover the pre-excitation energy of the electric motor 4 with the battery, and it is possible to suppress a decrease in the battery storage state, which is advantageous.

This requirement can be realized by configuring the control circuit for the generator 8 and the electric motor 4 as shown in FIG.
12, parts that function in the same manner as in FIG. 1 are given the same reference numerals.
Reference numeral 16 denotes an in-vehicle battery mainly for vehicle electrical components 17 (air conditioners, wipers, lamps, etc.), and the vehicle electrical components 17 are connected to the in-vehicle battery 16 via an operation switch (not shown).
Then, the electromagnetic coil of the rear wheel drive motor 4 is connected to the connection point between the in-vehicle battery 16 and the vehicle electrical component 17 via the relay switch 31 and the inverter 4b, and the electromagnetic coil of the generator 8 via the relay switch 31. Connect.
The relay switch 31 is turned off when the four-wheel drive switch 21 (see FIG. 1) is turned on and the motor four-wheel drive is desired, but is turned on when the generated voltage of the generator 8 is less than 14V under the same conditions. When the four-wheel drive switch 21 (see FIG. 1) is OFF and motor four-wheel drive is not desired, it is turned ON.

On the other hand, the field coil of the rear wheel drive motor 4 is connected to the battery 16 via the field current line 4a, and the field coil of the generator 8 is connected to the battery 16 via the field current line 8a and the power line 18 Then, the power line 10 is connected between the electromagnetic coils of the generator 8 and the motor 4.
One end of the electromagnetic coil of the 4WD clutch 13 is connected to the battery 16 by the clutch engagement power line 13a and the other end is connected to the 4WD controller 9.
Further, the 4WD controller 9 is not used to determine whether or not the field current Ifh is applied to the field coil of the generator 8, and the terminal for that purpose is used as the control terminal of the switching transistor on the ground side of the generator field coil. Connecting.

In FIG. 12, when the four-wheel drive switch 21 (see FIG. 1) is ON and motor four-wheel drive is desired, and the generated voltage of the generator 8 is 14 V or higher, the relay switch 31 is turned OFF and the following Four-wheel drive driving is possible with the rear wheel drive by the motor 4.
At this time, the four-wheel drive controller 9 puts the field current Ifh into the field coil of the generator 8 and engages the 4WD clutch 13.

Therefore, the generator 8 driven by the engine generates power corresponding to the power generation load determined by the field current Ifh, and directs the power to the electromagnetic coil of the rear wheel drive motor 4 via the inverter 4b through the power line 10.
At this time, the inverter 4b can drive the motor 4 to output torque and rotation in a direction according to the field current Ifm, and can drive the vehicle in four-wheel drive by rear wheel drive by the motor 4.

During the four-wheel drive traveling, when the motor overspeed exceeds the target speed, the motor 4 is brought into a braking state by a three-phase short circuit of the motor 4 by the inverter 4b.
The motor 4 generates electric power (voltage Viv) by such regenerative braking, and this electric power generated by the motor 4 is supplied to the field coil of the generator 8 through the power line 18 to cause the generator 8 to generate electric power.
If the voltage of the generated power is less than 14V, the relay switch 31 is turned on to go to the battery 16 to be charged.

By the way, in this embodiment, during the pre-excitation of the generator 8 by the field current Ifh, the generated power generated by this pre-excitation is indicated by the wavy arrow α, the power line 10, the closed relay switch 31, and the field The field current Ifm is supplied to the field coil of the electric motor 4 through the current line 4a, so that the electric motor 4 can be pre-excited.
Therefore, the electric motor 4 can be pre-excited with the generated power generated by the pre-excitation of the generator 8, and it is not necessary to cover the pre-excitation energy of the electric motor 4 with the battery, thereby suppressing the decrease in the battery storage state. be able to.

1 is a schematic diagram showing a drive control system of an electric motor type four-wheel drive vehicle including a drive force control device according to an embodiment of the present invention. It is a flowchart which shows the engine surplus torque calculation program which the four-wheel drive controller in the drive control system of the motor four-wheel drive vehicle performs. It is a flowchart which shows the control program of the generator and electric motor which the same 4 wheel drive controller performs. It is a flowchart which shows the pre-excitation control program of the generator and electric motor which the same 4 wheel drive controller performs. 5 is an operation time chart by pre-excitation control of the generator and the electric motor shown in FIG. 6 is a flowchart showing a generator and electric motor pre-excitation control program in place of FIG. 4, showing a driving force control apparatus according to still another embodiment of the present invention. 7 is an operation time chart by pre-excitation control of the generator and the electric motor shown in FIG. FIG. 7 is a flowchart showing a generator and electric motor pre-excitation control program instead of FIG. 6, showing a driving force control apparatus according to still another embodiment of the present invention. FIG. 7 is a flowchart showing a generator and electric motor pre-excitation control program instead of FIG. 6, showing a driving force control apparatus according to still another embodiment of the present invention. 6 is a flowchart showing a generator and electric motor pre-excitation control program in place of FIG. 4, showing a driving force control apparatus according to still another embodiment of the present invention. It is a time chart which shows the time-series change of a wheel speed about the case where it switches from a pavement running state to a snowy road or a gravel road running. It is a control circuit diagram of a generator and an electric motor when pre-exciting the electric motor with the electric power generated by the pre-excitation of the generator.

Explanation of symbols

1L front left wheel (main drive wheel)
1R right front wheel (main drive wheel)
2 Engine (Main power source)
3L left rear wheel (electric motor drive wheel)
3R right rear wheel (electric motor drive wheel)
4 Rear wheel drive motor (electric motor)
5 Automatic transmission 6 Differential gear device 7 Endless belt 8 Generator 9 Four-wheel drive controller
10 Power line
11 Relay
12 Reducer
13 4WD clutch
14 Differential gear unit
21 Four-wheel drive switch
22 Wheel speed sensors
23 Motor rotation sensor
25 Accelerator position sensor

Claims (6)

A main drive wheel driven by power from a main power source;
An electric motor drive wheel driven by power from an electric motor that responds to power generated by a generator coupled to the main power source,
When a driving slip state of the main driving wheel is detected based on a wheel speed difference between the main driving wheel and the electric motor driving wheel, the electric motor generates electric power by applying a power generation load to the generator via the electric motor. In an electric motor type four-wheel drive vehicle that drives an electric motor drive wheel to perform four-wheel drive,
An electric motor type four-wheel that is configured to keep at least one of the field of the generator and the electric motor in a pre-excited state during a set time even when the driving slip state of the main driving wheel is not detected Driving force control device for driving vehicle. The driving force control apparatus for an electric motor type four-wheel drive vehicle according to claim 1,
The set time is lengthened as the drive slip amount and / or the number of occurrences of the drive slip of the main drive wheel during the set time after the drive slip state of the main drive wheel is canceled is increased. Driving force control device for electric motor type four-wheel drive vehicle. In the driving force control device of the electric motor type four-wheel drive vehicle according to claim 2,
A driving force control device for an electric motor type four-wheel drive vehicle, wherein an upper limit is set for the set time. In the driving force control device for an electric motor type four-wheel drive vehicle according to any one of claims 1 to 3,
A driving force control device for an electric motor type four-wheel drive vehicle, characterized in that the set time is increased as the vehicle speed increases. In the driving force control device for an electric motor type four-wheel drive vehicle according to any one of claims 1 to 4,
While the drive slip of the main drive wheel is not generated, the field of the generator and the electric motor is pre-excited while the wheel speed fluctuation of the main drive wheel and / or the electric motor drive wheel is equal to or larger than the set fluctuation width. A driving force control device for an electric motor type four-wheel drive vehicle, characterized by being configured to maintain In the driving force control device for an electric motor type four-wheel drive vehicle according to any one of claims 1 to 5,
A driving force control device for an electric motor type four-wheel drive vehicle, wherein the electric motor is pre-excited by electric power generated by pre-excitation of the generator.

Images