JP2003237598A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power loss due to wiring resistance between a controller and an electric motor, protect a torque detecting coil and a controller from dust and water droplets, and adjust characteristics of a torque detecting circuit on a controller side. Provided is an electric power steering device. SOLUTION: A controller box 31 accommodating a controller 30 is mounted outside a housing 1a. A cylindrical space 1d is formed outside the vicinity of the arrangement of the detection coils 13 and 14 of the housing 1a, and a cylindrical protrusion 31a that fits into the space 1d is formed in the controller box 31. Projection 31a in space 1d
Are fitted and detachably fixed. It is preferable to interpose a sealing member 33 such as an O-ring on the fitting surface. The connection terminals 13a and 14a of the detection coil and the terminals on the board of the controller 30 are connected by a flexible lead wire 28, but the characteristics of the torque detection circuit are adjusted before the housing and the controller box are fixed. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus, and more particularly, to an arrangement structure of a housing for housing a torque sensor thereof and a controller box.

[0002]

2. Description of the Related Art Generally, an electric power steering apparatus currently in practical use includes a torque sensor for detecting steering torque, an actuator for supplying steering assist force to a steering mechanism by an electric motor, a torque detection circuit, and an actuator. And a controller that integrates a control circuit for controlling the motor and a motor drive circuit.

In the torque sensor, for example, a torsion bar is connected to a part of the steering shaft, the degree of torsion of the torsion bar is converted into a change in magnetism, and this change in magnetism is detected by a detection coil, and the obtained signal is obtained. The torque detection circuit performs signal processing to obtain the torque. The detection coil for detecting a change in magnetism is arranged near the steering shaft where the torsion bar is provided, and the torque detection circuit is also arranged near the detection coil, that is, near the steering shaft.

The actuator has a structure called a column assist type for transmitting the rotational force of the electric motor to the steering shaft, and a pinion for transmitting the rotational force of the electric motor to a pinion shaft of a rack and pinion mechanism arranged below the steering shaft. There are several types, such as a configuration called the assist type, and a configuration called the rack assist type that transmits the rotational force of the electric motor to the rack shaft of the rack and pinion mechanism arranged below the steering shaft. Type actuators are arranged in the vehicle compartment, and pinion assist type and rack assist type actuators are arranged in the engine room.

On the other hand, since the controller has a relatively large outer dimension, it is generally arranged in an engine room or a vehicle compartment away from the actuator, and the torque detection coil and the controller are connected by a wire. Target.

[0006]

In the electric power steering apparatus, since the electric power is supplied from the battery,
It is required to reduce power consumption as much as possible.
For this reason, it is required to reduce the power loss due to the resistance of the wiring between the controller that controls and drives the actuator and the electric motor.To this end, the length of the wiring between the battery, controller and electric motor must be reduced. The task is to make the length as short as possible.

In order to address such a problem, it is conceivable to arrange the controller inside the engine room, that is, outside the vehicle compartment. In this case, the wiring connecting the detection coil and the controller has a sealed structure, and the controller is It is necessary to prevent dust and water droplets from entering the inside, and it is also required that the controller can adjust the characteristics of the torque detection circuit after connection. The present invention is intended to solve the above-mentioned various problems.

[0008]

The present invention is to solve the above problems. According to the invention of claim 1, the input shaft and the output shaft arranged coaxially are connected by a torsion bar to prevent the torsion bar from twisting. A housing for accommodating an input shaft and an output shaft in an electric power steering device for detecting a torque based on the detected torque and controlling an electric motor for steering assist connected to an output shaft through a speed reduction mechanism in accordance with the detected torque. And a controller including a torque detection circuit that detects torque based on the output of a detection unit that detects the amount of twist of the torsion bar, and a control circuit that controls the electric motor according to the detected torque. A controller box is provided, and one of the housing and the controller box is fitted with a protrusion having a cylindrical cross section, and the other is fitted into the protrusion. Comprising a surface cylindrical recess, both an electric power steering apparatus characterized by being removably and tightly coupled.

The controller box may be provided with a protrusion having a cylindrical cross section, and the housing may be provided with a recess having a cylindrical cross section to be fitted into the protrusion.

A seal member may be arranged between the housing and the controller box between a protrusion having a cylindrical cross section and a concave portion having a cylindrical cross section fitted to the other protrusion. .

The controller box may include a storage space for storing a wiring member that connects the torque detection circuit and the controller.

The wiring member for connecting the torque detection circuit and the controller includes a connection board which is detachably attached to the connection terminal of the torque detection circuit and electrically connected to the connection terminal. The connection board is inside the housing. It is good to fix it with a screw.

In the screw for fixing the connection board inside the housing, the space between the screw head and the protrusion of the controller box is shorter than the effective screw length of the screw, and the screw may fall off due to loosening of the screw. It is better not to use it.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] A first embodiment is a pinion assist type electric power steering apparatus, and FIG. 1 shows a structure of a main part of the electric power steering apparatus of the first embodiment. Sectional drawing, FIG. 2 is an enlarged sectional view of the main part thereof, and FIG. 3 is an enlarged main section showing a modified example of the mounting position of the seal member on the mounting surface of the controller box of the electric power steering apparatus shown in FIGS. 1 and 2. FIG. FIG. 4 is a perspective view showing the configuration of the torque detection unit of the torque sensor.

In FIGS. 1 and 2, reference numerals 1a and 1b denote housings, which have a two-part structure of an input shaft side 1a and an output shaft side 1b. Inside the housings 1a and 1b, an input shaft 2 rotatably supported by a bearing 6, a torsion bar 3 arranged therein, and an output shaft 4 connected to the input shaft 2 via the torsion bar 3 are provided. 7
It is rotatably supported by a and 7b.

The input shaft 2, the torsion bar 3 and the output shaft 4 are arranged coaxially, and the input shaft 2 and the torsion bar 3 are fixedly coupled by a pin 2a, and the torsion bar 3 is provided.
The output shaft 4 and the output shaft 4 are joined together by a spline SP formed therebetween so as to be integrated in the rotational direction and movable in the axial direction. Further, in FIG. 1, a steering shaft (not shown) and a steering wheel at the tip thereof are integrally attached to the left end side of the input shaft 2.

A pinion shaft 4a is formed integrally with the output shaft 4, and the teeth of the pinion shaft 4a mesh with the rack teeth of the rack shaft 8 to form a known rack-and-pinion type steering mechanism. .

A worm wheel 9 which is coaxial with the output shaft 4 and rotates integrally therewith is fixed to the output shaft 4 and meshes with a worm wheel 10 driven by an electric motor for steering assistance (not shown). . The rotational force of the electric motor is transmitted to the output shaft 4 via the worm 10 and the worm wheel 9, and a steering assist torque in an arbitrary direction is applied to the output shaft 4 by appropriately switching the rotation direction of the electric motor.

Next, the torque sensor will be briefly described. The configuration and operation thereof are not directly related to the gist of the invention of the present application, so a detailed description thereof will be omitted here.
The details are disclosed in JP-A-38715.

The configuration of the torque detecting portion of the torque sensor will be described below with reference to FIGS. 2 and 4. The torque detector is
A sensor shaft portion 11 formed on the input shaft 2 and detection coils 13 and 14 arranged inside the housing 1a;
And a cylindrical member 12 arranged between the sensor shaft portion 11 and the detection coils 13 and 14.

As apparent from FIG. 2, a sensor shaft portion 11 made of a magnetic material is formed on the outer peripheral surface of the input shaft 2 near the left end in FIG. 2, and the surface of the sensor shaft portion 11 is formed. Includes a plurality of ridges 11 extending in the axial direction.
A are formed at equal intervals along the circumferential direction, and groove portions 11b wider than the width of the ridges are formed between the ridges.

On the outside of the sensor shaft portion 11,
A cylindrical member 12 made of a conductive and non-magnetic material, for example, aluminum, is arranged coaxially with the sensor shaft portion 11 in proximity to the sensor shaft portion 11, and an extension 12e of the cylindrical member 12 has an extension 12e. It is fixed to the outside of the end of.

The cylindrical member 12 has a first window row composed of a plurality of rectangular windows arranged at equal intervals in the circumferential direction at positions facing the protrusions 11a on the surface of the sensor shaft portion 11 described above. 12a and a second window row 12b formed of a plurality of rectangular windows having the same shape as the windows and having different phases in the circumferential direction are provided at positions axially displaced from the first window row. ing.

The outer periphery of the cylindrical member 12 is surrounded by a yoke 15 around which detection coils 13 and 14 of the same standard are wound. The detection coils 13 and 14 are arranged coaxially with the cylindrical member 12, the detection coil 13 encloses the first window row 12a portion, and the detection coil 14 encloses the second window row portion 12b. The yoke 15 is fixed inside the housing 1a, and the output wires of the detection coils 13 and 14 are terminals 13a and 14a.
Connected to.

Input shaft 2 by operating the steering wheel
When a rotational force is applied to, the rotational force is transmitted to the output shaft 4 via the torsion bar 3. At this time, a frictional force between the steering wheel and the road surface and a frictional force due to meshing of gears of the steering mechanism coupled to the output shaft 4 act on the output shaft 4, so that the input shaft 2 and the output shaft 4 are separated from each other. Twisting occurs in the torsion bar 3 connecting the two, and the ridges 11a and 11b on the surface of the sensor shaft portion 11 on the side of the input shaft 2 and the output shaft 4 are twisted.
Relative rotation occurs between the first window row 12a and the second window row 12b of the cylindrical member 12 on the side of the sensor shaft portion 1
The magnetic flux generated at 1 increases or decreases, and one of the inductances of the detection coils 13 and 14 increases and the other decreases as the magnetic flux increases or decreases. The torsion angle of the torsion bar 3 changes in proportion to the magnitude of the torque, and the amount of increase or decrease in the inductance of the detection coils 13 and 14 changes.
The magnitude of the torque can be detected from the difference between the inductances of 14 and 14.

FIG. 5 is a circuit block diagram of the controller 30. The controller 30 comprises a torque detection circuit 22, a control circuit 25, a motor drive circuit 26 and the like.

The torque detection circuit 22 is a bridge circuit composed of a first arm in which a detection coil 13 and a resistor R1 are connected in series, and a second arm in which a detection coil 14 and a resistor R2 are connected in series. Composed of.

The detection coils 13 and 14 of the first arm and the second arm are connected to a power supply VDD which outputs an AC voltage of a predetermined frequency through a PNP type transistor Tr, and the first arm and the second arm. The other ends of the resistors R1 and R2 are grounded. In addition, 21 is the detection coils 13 and 1
4 is a diode that allows a current only when a reverse electromotive force is generated.

When no torque is applied, the detection coil 1
The values of the resistors R1 and R2 are adjusted in advance so that the voltages appearing at both ends of 3 and 14 become equal.

The voltage signals appearing at both ends of the detection coil 13 and the detection coil 14 are converted into a signal of the difference between the detection coils in the differential amplifier 23, amplified, and output to the control circuit 25 via the sample hold circuit 24. .

The control circuit 25 uses the sample hold circuit 2
Based on the signal of the difference between the two detection coils supplied from 4, the direction and magnitude of the relative rotational displacement between the input shaft 2 and the cylindrical member 12, that is, the output shaft 4 are calculated, and steering is performed by multiplying by a predetermined constant. The direction and magnitude of the torque are obtained, the magnitude and direction of the current supplied to the electric motor for steering assistance are determined, and the motor drive circuit 26 is controlled. Motor drive circuit 2
6 is a publicly known four field effect transistor (FET)
H bridge circuit etc. configured using is used,
The control of the magnitude of the current supplied to the electric motor is executed by changing the duty ratio of the FET.

Although it has been described here that the motor drive circuit 26 is incorporated in the controller 30,
Separate the motor drive circuit 26 from the controller 30,
It may be integrated into an electric motor for steering assistance.

Next, the arrangement of the controller 30 and its mounting structure will be described with reference to FIGS. The controller box 31 that houses the controller 30 is
It is attached to the outside of the housing 1a. Housing 1a
A cylindrical space 1d is formed on the outside of the vicinity where the detection coils 13 and 14 of FIG.
1 is a cylindrical protrusion 31a that fits in this space 1d.
Then, the protrusion 31a is fitted into the cylindrical space 1d and fixed by the mounting bolt 32.

The space between the space 1d and the protrusion 31a is fitted with O.
When the seal member 33 such as a ring is used for sealing, airtight sealing can be performed, and intrusion of dust and water droplets can be effectively prevented.

In the configuration of FIGS. 1 and 2, the detection coil 1
The connection terminals 13 a and 14 a of the controllers 3 and 14 are exposed in a cylindrical space 1 d formed in the housing 1 a, and the controller 3 is disposed inside the controller box 31.
A flexible lead wire 28 is connected to the terminal on the substrate 0. When connecting the lead wire 28, the controller box 31 is removed from the housing 1a and the lead wire 28
Is connected to adjust the characteristics of the torque detection circuit 22, and then the lead wire 28 is folded to make the controller box 3
It should be accommodated in the concave portion 31e provided in the first cylindrical protrusion 31a.

According to this structure, when the electric motor is attached to the housing 1b, the length of the wiring between the controller and the electric motor can be shortened.
The torque detection circuit and the controller can have a sealed structure to prevent intrusion of dust and water droplets, and after the torque detection circuit and the controller are connected, the characteristics of the torque detection circuit can be adjusted on the controller side.

FIG. 3 is an enlarged sectional view of a main part showing a modified example of the mounting position of the seal member on the mounting surface of the controller box of the electric power steering apparatus shown in FIGS. The configuration is substantially the same as that shown in FIGS. 1 and 2, and only the mounting position of the seal member is different. Therefore, the same reference numerals are given to the same members and the description thereof will be omitted.

In the configuration shown in FIGS. 1 and 2, a groove for fitting the seal member 33 is provided on the housing 1a side, but in the configuration shown in FIG. 3, the seal member 33 is provided on the protrusion 31a of the controller box 31. Is provided with a groove for fitting. With this configuration, the groove into which the seal member is fitted can be easily processed.

[Second Embodiment] The second embodiment has a structure similar to that of the above-described first embodiment, and is a structure for attaching lead wires on the controller side to the connection terminals of the detection coil. However, the same parts as those of the first embodiment will be designated by the same reference numerals and description thereof will be omitted, and only different points will be described.

FIG. 6 is an enlarged sectional view of a main part of the electric power steering system according to the second embodiment. The connection terminals 13a and 14a of the detection coil are the coupler (wiring connection device) 28a provided at the tip of the lead wire 28 on the controller side.
Are connected by. With this configuration, it is possible to easily connect the detection coil and the controller.

[Third Embodiment] The third embodiment has a configuration similar to that of the first embodiment described above, and the tip of the lead wire on the controller side connected to the connection terminal of the detection coil. The only difference is that the connection is made via a connection substrate, and therefore, the portions common to the configuration of the first embodiment are assigned the same reference numerals and explanations thereof are omitted.
Only the differences will be described.

FIG. 7 is an enlarged cross-sectional view of an essential part of the electric power steering apparatus of the third embodiment, showing a state in which the controller box and the connection board are attached to the housing, and FIG. 8 shows the controller box in the housing. It is sectional drawing which shows the state removed.

In the third embodiment, the connection board 29 is connected to the tip of the lead wire 28 on the controller side.
The contact piece of the connection board 29 is connected to the connection terminal 13a of the detection coil,
The configuration is such that the detection coil and the controller are connected by being inserted into 14a.

First, as shown in FIG. 8, with the controller box 31 removed from the housing 1a, the contact pieces of the connection board 29 are connected to the detection coil connection terminals 13a and 1a.
4a, and the connection board 29 is fixed to the housing 1a with fixing screws 29a. At this time, the space between the screw head of the fixing screw 29a and the protrusion of the controller box 31 is set to be shorter than the effective screw length of the fixing screw 29a. As a result, even if the fixing screw 29a becomes loose, it does not fall off.

The member 29b on the connection board 29
Is a characteristic adjusting member of the torque detection circuit, and is a connection board 2
After fixing 9 to the housing 1a, the characteristics are adjusted.

Next, as shown in FIG. 7, the housing 1a
The cylindrical projection 31a of the controller box 31 is fitted into the cylindrical space 1d formed in the above, and is fixed by the mounting bolt 32.

With this configuration as well, the detection coil and the controller can be easily connected, and the characteristic of the torque detection circuit can be easily adjusted by removing the controller box 31.

[Fourth Embodiment] The fourth embodiment is a column assist type electric power steering apparatus. FIG. 9 is a cross-sectional view showing the configuration of the main part of the electric power steering apparatus of the fourth embodiment, which includes a torque detector arranged in the steering column, a worm wheel and a worm arranged under the steering shaft. 2 shows the arrangement of the worm gear mechanism and the controller.

In FIG. 9, reference numerals 41a and 41b denote housings, which have a two-part structure of an input shaft side 41a and an output shaft side 41b. A steering shaft housing 42 has one end fixed to the housing 41a.

The bearing 4 is provided inside the steering shaft housing 42.
An input shaft 45 rotatably supported by 3 is arranged,
Although not shown, the steering wheel is integrally attached to the right end of the input shaft 45 in FIG.

In addition, one end of a torsion bar 46 is connected to the left side of the input shaft 45 in FIG. The output shaft 47 is rotatably supported by bearings 48a and 48b. Although not shown on the left side of the output shaft 4 in FIG. 9, it is connected to a known rack-and-pinion type steering mechanism through a universal joint.

A worm wheel 50, which is coaxial with and rotates integrally with the output shaft 47, is fixed to the output shaft 47, and meshes with a worm wheel 51 driven by an electric motor for steering assistance (not shown). . The rotational force of the electric motor is transmitted to the output shaft 47 via the worm 51 and the worm wheel 50, and a steering assist torque in an arbitrary direction is applied to the output shaft 47 by appropriately switching the rotation direction of the electric motor.

Since the torque detector is the same as that of the third embodiment described above, the same members are designated by the same reference numerals and the description thereof will be omitted. A cylindrical space portion 41d is formed,
The controller box 31 is placed in the cylindrical space 41d.
The cylindrical protrusions 31a are fitted and fixed by the mounting bolts 32.

This configuration is an application of the connection configuration of the torque detection unit and the controller of the third embodiment to a column assist type electric power steering device, and like the third embodiment, The detection coil and the controller can be easily connected, and by removing the controller box 31, the characteristics of the torque detection circuit can be easily adjusted.

FIG. 10 is a harness (wiring) between the controller box 31, the electric motor MT, and the battery BT in the first to third embodiments.
FIG. 3 is a diagram for explaining the state of WR, in which a controller box 31 is attached to a housing 1a equipped with a torque detection unit, and a housing 1b which is paired with the housing 1a.
Since the electric motor MT is attached to the electric motor MT, the harness (wiring) WR from the battery BT is connected to the controller box 31, and the wiring is completed between the controller box 31 and the electric motor MT. .

In the first to third embodiments, since the controller box 31 is in the engine room outside the vehicle compartment, the length of the harness (wiring) WR from the battery BT can be shortened.

Also, in the column assist type electric power steering apparatus of the fourth embodiment, the controller box 31 is attached to the housing 1a having the torque detecting portion, and the housing 1a portion is located outside the vehicle compartment. When arranged in the engine room, the length of the harness (wiring) WR from the battery BT can be similarly shortened.

[0059]

As described above, according to the present invention, in the electric power steering apparatus for controlling the electric motor for steering assist, which is coupled to the output shaft through the speed reduction mechanism, according to the detected torque, A housing for accommodating the output shaft, a torque detection circuit for detecting torque based on the output of the detection means for detecting the amount of twist of the torsion bar, and a control circuit for controlling the electric motor according to the detected torque are provided. And a controller box for accommodating the controller are detachably and tightly coupled by a protrusion having a cylindrical cross section provided on one side and a concave portion having a cylindrical cross section fitted to the protrusion provided on the other side. Since the controller and the electric motor are arranged close to each other, the length of the wiring can be shortened and the power loss due to the wiring resistance can be reduced. It becomes possible to.

Further, since the wiring connecting the detection coil and the controller is housed in the hermetically sealed structure, intrusion of dust and water droplets into the controller can be prevented, and the housing and the controller box can be attached and detached. Therefore, after the detection coil and the controller are connected by wiring, it is possible to adjust the characteristics of the torque detection circuit on the controller side before sealing, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a main part of an electric power steering device according to a first embodiment.

FIG. 2 is an enlarged cross-sectional view of a main part of the electric power steering device shown in FIG.

FIG. 3 is an enlarged cross-sectional view of a main part showing a modified example of the mounting position of the seal member on the mounting surface of the controller box of the electric power steering device.

FIG. 4 is a perspective view showing a configuration of a torque detection unit of the torque sensor.

FIG. 5 is a circuit block diagram of a controller.

FIG. 6 is an enlarged cross-sectional view of a main part of the electric power steering device according to the second embodiment.

FIG. 7 is an enlarged cross-sectional view of a main part of an electric power steering device according to a third embodiment.

8 is an enlarged cross-sectional view of a main part of the electric power steering device shown in FIG. 7, with a controller box removed.

FIG. 9 is an enlarged cross-sectional view of a main part of an electric power steering device according to a fourth embodiment.

FIG. 10 is a diagram illustrating a state of a harness (wiring) between the controller box, the electric motor, and the battery in the first to third embodiments.

[Explanation of symbols]

1a, 1b housing 1d Cylindrical space 2 input axes 3 torch bar 4 output shafts 4a Pinion shaft 8 rack axes 9 worms 10 worm wheel 11 Sensor shaft part 12 Cylindrical member 13, 14 Detection coil 15 York 22 Torque detection circuit 23 Differential amplifier 24 sample and hold circuit 25 Control circuit 26 Motor drive circuit 28 Lead wire (wiring) 28a coupler (wiring connection device) 29 connection board 29a fixing screw 30 controller 31 Controller Box 31a Cylindrical protrusion 31e recess 32 mounting bolts 33 seal member 33

Claims (6)

[Claims] 1. An input shaft and an output shaft, which are coaxially arranged, are connected by a torsion bar, torque is detected based on the torsion of the torsion bar, and the output shaft is connected to the output shaft via a reduction mechanism according to the detected torque. In an electric power steering device that controls a combined electric motor for steering assistance, a torque is generated based on an output of a housing that houses an input shaft and an output shaft and a detection unit that detects the magnitude of twist of the torsion bar. A torque detection circuit for detecting,
A controller box for accommodating a controller having a control circuit for controlling the electric motor according to the detected torque, wherein the housing and the controller box are provided with a protrusion having a cylindrical cross section on one side and a protrusion on the other side. An electric power steering device comprising: a recess having a cylindrical cross section that fits into a protrusion, and the two are detachably and tightly coupled to each other. 2. The electric power according to claim 1, wherein the controller box has a protrusion having a cylindrical cross section, and the housing has a recess having a cylindrical cross section fitted into the protrusion. Steering device. 3. A seal member is disposed between one of the protrusions having a cylindrical cross section between the housing and the controller box and the other concave portion having a cylindrical cross section fitted to the protrusion. The electric power steering device according to claim 1, wherein 4. The electric power steering system according to claim 1, wherein the controller box has a storage space for storing a wiring member that connects the torque detection circuit and the controller. apparatus. 5. The wiring member for connecting the torque detection circuit and the controller includes a connection board which is detachably attached to the connection terminal of the torque detection circuit and electrically connected to the connection terminal, and the connection board is inside the housing. The electric power steering device according to any one of claims 1 to 4, wherein the electric power steering device is fixed to the shaft with a screw. 6. The screw for fixing the connection board to the inside of the housing has a space between the screw head and a protrusion of the controller box shorter than an effective screw length of the screw, and the screw is loosened to prevent the screw from being released. The electric power steering apparatus according to claim 5, wherein the electric power steering apparatus has a structure that does not fall off.