JP3257462B2 - Rear wheel steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering device for steering rear wheels by an electric motor.

[0002]

2. Description of the Related Art Conventionally, this type of apparatus is disclosed in
As disclosed in JP-A-215226, an electric motor for steering rear wheels is housed in a housing, the housing is supported by a suspension member, and the suspension member is fixed to a vehicle body. .

[0003]

However, in a vehicle equipped with the above-mentioned conventional rear wheel steering device, noise may be mixed into the AM band of a radio mounted on the vehicle, making it difficult to hear the radio. There was a problem.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the conventional device, the present inventors worked on investigating the cause of the generation of the noise. As a result, when the phase of the motor drive current was switched, pulse width modulation (PWM) was performed. I discovered that noise appeared to be generated from the housing due to electromagnetic waves generated from the electric motor when the drive current suddenly changed, such as when switching the drive current in control. On the other hand, the housing is a conductor, and the housing is supported by a relatively large iron (conductive) suspension member, and the suspension member is also mounted on an iron (conductive) vehicle body. Therefore, it is unlikely that noise is generated from the housing. However, as a result of the present inventors further investigating the cause, since the suspension member and the vehicle body are connected via the rubber bush, the housing Since the suspension member is not completely grounded to the vehicle body, the above-mentioned noise cannot be prevented by the capacity of the housing and the suspension member, and the housing serves as an antenna to generate noise. It was concluded that the noise was mixed into the radio mounted on the vehicle.

Based on this conclusion, in order to solve the above-mentioned problem, a first structural feature of the present invention resides in that a housing made of a conductive material and containing an electric motor is grounded to a vehicle body. As a result, the housing is grounded to a conductive large-capacity object such as a vehicle body, and theoretically, the electric motor is electrostatically shielded by the housing, thereby significantly reducing noise mixing into a radio mounted on the vehicle. It became easier to hear. This was also confirmed experimentally.

A second structural feature of the present invention is that, in the rear wheel steering device, a lead having one end connected to the housing is guided into a trunk room, and the other end of the lead is connected to the trunk room in the trunk room. The housing is grounded to the vehicle body by connecting to the wall of the vehicle. According to this, in addition to the effect of the first feature, the conductor for grounding the housing can be arranged so that stepping stones or the like from the road surface do not hit, and the conductor can be provided at a position relatively close to the housing. The housing can be grounded to the vehicle body.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an entire four-wheel steering vehicle to which the present invention is applied. This four-wheel steering vehicle
A front wheel steering device A that is assembled to the front lower portion of the vehicle and that steers the front wheels FW, FW by turning the steering wheel 11.
And a rear wheel steering device B mounted on a lower rear portion of the vehicle to steer rear wheels RW, RW, and an electric control device C for electrically controlling the rear wheel steering device B.

As shown in FIGS. 1 to 3, the rear wheel steering device B is formed by penetrating a relay rod 21 extending in the vehicle width direction, and displacing the rod 21 in the axial direction to produce a rear wheel RW. , RW steering actuator unit 20
It has. The relay rod 21 has tie rods 22a and 22b and knuckle arms 23a and 23a at both ends.
The rear wheels RW, RW are steerably connected via 3b.

The actuator unit 20 has a housing 24 which is formed of a conductive material such as aluminum and has a cylindrical shape and through which a relay rod 21 penetrates. An electric motor 25 is incorporated in the housing 24.
The electric motor 25 is fixed to the housing 24 on the outer periphery of the relay rod 21 to form a stator. The three-phase coil 25a is provided between the relay rod 21 and the coil 25a so as to face the coil 25a. 24, a brushless motor including an iron connecting member 25b formed in a cylindrical shape and rotatable about an axis, and a rotor having a permanent magnet 25c fixed on the outer periphery of the member 25b. The rotation of the electric motor 25 is controlled by a first member connected to the connecting member 25b so as to transmit power.
And reduction gear 2 including second and second planetary gear mechanisms 26a and 26b
6, the power is transmitted to a nut 27a rotatably assembled to the housing 24. Nut 27
a meshes with a male screw portion 27b formed on the outer peripheral surface of the relay rod 21 on the inner peripheral surface thereof.
Together with b, a movement direction converter 27 is constituted. Thereby, the connecting member 25b of the electric motor 25 and the permanent magnet 25
When the rotator made of c rotates forward and reverse, the relay rod 21
Are displaced in the left-right direction, and the rear wheels RW, RW are steered in the left-right direction.

In the housing 24, a coil 25 is provided.
A magnetic pole position sensor 25d for detecting the rotational position of the rotor composed of the connecting member 25b and the permanent magnet 25c with respect to the stator constituted by a is accommodated. A displacement sensor 28 is mounted on the outer periphery of the housing 24.
The displacement sensor 28 accommodates a potentiometer that detects the amount of displacement (steering angle of the rear wheels RW, RW) of the rod 21 relative to the reference position to the left and right in conjunction with the relay rod 21.

The electric control device C has a box-shaped electric control circuit unit 30 containing an electric control circuit mainly composed of a computer. Electric control circuit unit 30
Are connected to an electric motor 25 (a coil 25a and a magnetic pole position sensor 25d) and a displacement sensor 28, and also include a plurality of sensors for detecting various state quantities of the vehicle, such as a vehicle speed sensor, a steering angle sensor, and a yaw rate sensor. 31, 31, ... are also connected. The electric control circuit unit 30 receives detection signals from the various sensors 25d, 28, 31, 31... And outputs three-phase drive current to the electric motor 25 as shown in detail in FIG. It is supplied to the three-phase coil 25a. In this case, a driving current composed of a pulse train is supplied to the coil 25a by two sets of three switching transistors 32 and 33 connected in series between the voltage source + V and the ground. The switching transistor 32 is switching-controlled by a three-phase control signal in order to supply a three-phase pulse drive current to each coil 25a of the electric motor 25. The switching transistor 33 is used for pulse width modulation (PWM) control for controlling the amount of drive current for each coil 25a of the electric motor 25.

Next, these actuator units 2
A description will be given of an assembly state and electrical wiring of the vehicle body No. 0. As shown in FIG. 2, the actuator unit 20 is fixed to a front end of the suspension member 43 via a bracket 42 by a bolt 41. Bolt 41,
The bracket 42 and the suspension member 43 are both made of iron (conductive), are electrically connected to each other, and have a relatively large capacity. The suspension member 43 includes a bush 44
, Is fixed to a frame 45 extending at a lower portion of the vehicle by an iron (conductive) bolt 46. The bush 44 is a coaxially arranged iron (conductive) inner cylinder 44.
a and the outer cylinder 44b, and a cylindrical rubber which is an insulating material interposed between the two cylinders 44a and 44b. The frame 45 forms a skeleton of an iron vehicle integrally formed with the front side member, the main floor side member, and the rear floor side member. Is electrically connected to the vehicle body including a trunk room 46 described later, and is a large-capacity object electrically equivalent to ground. In the present specification, these parts are regarded as synonymous with the vehicle body as far as the grounding is concerned.

As shown in FIG. 5, a wire harness 5 for supplying a drive current to a coil 25a of the electric motor 25 is provided.
1 and a wire harness 52 for extracting a detection signal from the magnetic pole position sensor 25d of the motor 25 are drawn out of the housing 24 of the actuator unit 20, and these wire harnesses 51 and 52 are connected to the displacement sensor 28. Along with the wire harness 53, the outer peripheral surface of the housing 24 extends in the axial direction thereof and is covered with a corrugated tube 54. The corrugated tube 54 is made of an insulating elastic material such as rubber or synthetic resin so as to be able to expand and contract. The corrugated tube 54 is fixed to the housing 24 at an appropriate location, and extends in the axial direction on the outer peripheral surface of the housing 24, and extends rearward at substantially the center in the vehicle width direction as shown in FIG. 2. Bent. And the corrugated tube 54
Is extended rearward between the suspension member 43 and the lower wall of the trunk room 46 located above the suspension member 43, and through a hole 46a provided in the lower wall of the trunk room 46 at an appropriate position as shown in FIG. Guided inside. A grommet 55 is mounted on the outer peripheral surface of the corrugated tube 54 at a position where the tube 54 passes through the hole 46a to block the inside of the trunk room 46 from the outside. In the trunk room 46, the corrugated tube 54 extends laterally along the lower wall and is guided slightly forward. The electric control circuit unit 30 is assembled at a front portion on the side of the trunk room 46, and the unit 30 has a wire harness 51 drawn out from the front end of the corrugated tube 54.
To 53 are connected.

As shown in FIG. 5, a crimp terminal 56a provided at one end of a grounding wire harness 56 is connected to the outer peripheral surface of the housing 24 of the actuator unit 20 by an iron (conductive) screw 57. ing. The wire harness 56 also extends in the axial direction on the outer peripheral surface of the housing 24, is covered with the corrugated tube 54 together with the other wire harnesses 51 to 53, and enters the trunk room 46. In the trunk room 46, as shown in FIG.
And the grounding wire harness 5
6 has been pulled out. Further, a grounding washer 58 made of a conductive material is provided at an appropriate position on the lower wall of the trunk room 46 beside the tire house 46b, and the washer 58 is provided at the other end of the grounding wire harness 56. The crimp terminal 56b is connected by an iron (conductive) screw 59.

In the four-wheel steering vehicle configured as described above, when the steering wheel 11 is turned, the front wheels FW, FW are steered according to the turning. Further, the electric control circuit unit 30 determines the target rear wheel steering angle in accordance with the various state quantities of the vehicle input from the various sensors 31, and determines the rear wheel R in accordance with the outputs of the displacement amount sensor 28 and the magnetic pole position sensor 25d.
The actual rear wheel steering angles of W and RW are calculated, and a three-phase drive current having a magnitude corresponding to the difference between the target rear wheel steering angle and the actual rear wheel steering angle is output to the electric motor 25 to output the rear wheel. RW, RW is steered to the target rear wheel steering angle. In this case, an electromagnetic wave is generated from the electric motor when the drive current changes abruptly, for example, when the drive current is switched in phase or when the drive current is switched in pulse width modulation (PWM) control. However, since the housing 24 accommodating the electric motor 25 is grounded to the vehicle body in the trunk room 46 by the grounding wire harness 56, the housing 24 acts as a shield member for electromagnetic waves, and the housing 24 moves from the electric motor 25 to the outside of the housing 24. The amount of leaked electromagnetic waves is extremely small. Accordingly, noise contamination into the radio mounted on the vehicle is significantly reduced, making the radio easier to listen to, and this was also confirmed by experiments.

The grounding wire harness 56 is connected to the corrugated tube 54 together with the other wire harnesses 51 to 53.
The tube 54 is connected to the suspension member 4
3 and is installed between the lower wall of the trunk room 46 and guided into the trunk room 46, so that there is no need for a major change, and no damage is caused by stepping stones from the road surface. The effect that the housing 24 can be grounded to the vehicle body can also be expected.

In the above embodiment, the housing 24 is electrically connected to the lower wall of the trunk room 46 by the grounding wire harness 56 to be grounded to the vehicle body. However, the housing 24 may be grounded by another method. Can be grounded to the vehicle body. For example, the inner cylinder 44a and the outer cylinder 44b of the bush 44 for connecting the suspension member 43 and the frame 45 are connected by a short stretchable wire (cable bond), or the suspension member 43 is connected to the frame 45 or It can be directly connected to other vehicle positions via conductors,
4 may be directly connected to the frame 45 or other vehicle body positions via conductive wires. Further, at least one of the wire harnesses 51 to 53 is formed of a shield wire (a wire harness in which an outer peripheral surface of an insulating layer covering an inner conductor is covered with a conductive layer such as a metal ground for grounding or a metal net). In this case, one end of the grounding conductive layer may be grounded to the vehicle body, and the other end may be connected to the outer peripheral surface of the housing 24. In particular, forming the wire harness 51 for supplying a drive current to the electric motor 25 with a shielded wire is useful for suppressing electromagnetic waves generated from the harness 51 itself.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of a four-wheel steering vehicle equipped with a rear-wheel steering device according to the present invention.

FIG. 2 is an exploded perspective view of a rear portion of the vehicle for explaining an assembled state of the actuator unit of FIG. 1;

FIG. 3 is a partially cutaway view of the actuator unit.

FIG. 4 is an electric circuit diagram showing a part of the electric motor and an electric control circuit unit in detail for describing a connection state of the unit.

5 is an enlarged view of a part of the actuator unit of FIG. 2 for explaining a connection state of a wire harness.

FIG. 6 is a perspective view schematically showing the inside of a trunk room for explaining a connection state of a wire harness.

[Explanation of symbols]

A: Front wheel steering device, B: Rear wheel steering device, C: Electric control device, RW, RW: Rear wheel, 20: Actuator unit, 21: Relay rod, 24: Housing, 25: Electric motor, 25d: Magnetic pole position sensor , 28: Displacement sensor, 30: Electric control circuit unit, 31: Various sensors,
43 ... suspension member, 44 ... bush, 45 ...
Frame, 46: Trunk room, 51 to 53: Wire harness, 54: Corrugated tube, 56: Wire harness for grounding.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B62D 5/04 B62D 7/14 B60R 16/00

Claims (2)

(57) [Claims] As an electric motor for steering the 1. A rear wheel
Conductive housing housed inside is insulated from vehicle body
In a rear wheel steering device supported by a suspension member assembled in a state , the housing is electrically connected to the vehicle body and grounded,
The housing protects the electric motor from electrostatic shielding.
Wheel steering system was to be. In rear wheel steering apparatus as claimed in claim 2] 請 Motomeko 1 guides the wire having one end connected to said housing to said vehicle body <br/> the trunk room, the trunk and the other end of the wire
Rear wheel steering apparatus, characterized in that the ground Ri by the be connected to the inner wall surface of the room.