JPH0733034A - Power steering device - Google Patents

Abstract

PURPOSE:To easily and securely carry out both the backlash adjustment of a gear speed-reduction device interposed in the transmission system for transmitting power from a steering auxiliary motor to a steering mechanism, and the gap adjustment of an electromagnetic clutch for connecting or disconnecting the motor and the steering mechanism. CONSTITUTION:The backlash adjustment of a speed-reduction device is carried out in such a procedure that a bearing case 8 is screwed in the screw hole 10a formed inside a transmission housing 10, the transmission shaft 14 of a steering auxiliary motor 11 is supported by a ball bearing 13 that has been internally fitted and fixed in the bearing case, and the pinion 7b of this transmission shaft is moved in the axial direction by the screwing-in of the bearing case, and then it its fixed by the tightening of a lock nut 80. An electromagnetic clutch 12 is made up of an armature 22 that has been slidably inserted into the other side of the transmission shaft, and a clutch rotor 20 that has been fitted to the output shaft of the motor; and the armature is energized toward the motor side by means of a coil spring 9 that has been interposed between the armature and a collar 15.

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 (power steering apparatus) which uses an electric motor as a source of a steering assist force.

[0002]

2. Description of the Related Art Based on the detection result of the steering torque applied to a steering wheel, a steering assisting motor disposed in the middle of the steering mechanism is driven, and the rotational force of the motor is applied to the steering mechanism. An electric power steering device that is designed to assist steering is compared with a hydraulic power steering device that uses a hydraulic actuator as a source of steering assist force.
There is an advantage that the assist force characteristics can be easily changed according to the traveling state such as the speed of the vehicle and the frequency of steering, by the rotation control of the motor.

On the other hand, a drawback of the electric power steering apparatus is that it is difficult to obtain a small motor capable of generating a sufficient rotational force for assisting the steering operation. A configuration is adopted in which a reduction gear is interposed in the middle of a transmission system from the output side of a motor for use in a steering mechanism, and the output taken out to the output shaft of the motor is increased by deceleration to be added to the steering mechanism. In many cases, the output shaft of the steering assisting motor and the input shaft to the steering mechanism are arranged such that their axial centers intersect with each other. It is desirable that the transmission direction can be changed to the shaft, and the applicant of the present application responds to such a request and aims at downsizing of the entire transmission system.
A power steering apparatus using a hypoid gear as the speed reducer has been previously proposed.

Further, since the reduction gear is interposed in the transmission system from the steering assisting motor to the steering mechanism, the inertia of the rotating portion of the motor is amplified and added to the steering mechanism when the motor is not operating. However, there is a problem that the operation of the steering mechanism, particularly the operation of returning to the straight traveling state, is adversely affected. Therefore, conventionally, a transmission shaft is arranged between the output shaft of the motor and the input shaft to the steering mechanism, and the speed reducer is configured between the transmission shaft and the input shaft to the steering mechanism. An electromagnetic clutch is arranged between the transmission shaft and the output shaft of the motor, and the electromagnetic clutch is engaged only when required, thereby eliminating the influence of the inertia of the motor.

FIG. 3 is a longitudinal sectional view showing a main part of a conventional electric power steering apparatus. In the figure, 1 is an upper shaft, and 2 is a lower shaft, which are rotatably supported in a cylindrical housing 4 which can be vertically divided into two parts, and which are coaxial with each other via a torsion bar 3. Are linked to. The upper shaft 1 projects above the housing 4 by an appropriate length, and the projecting end is connected to a steering wheel (not shown). A rack shaft 5 is supported on the lower portion of the housing 4 in a manner substantially orthogonal to the shaft centers of the upper shaft 1 and the lower shaft 2, and the rack shaft 5 is a pinion formed on the outer periphery of the lower half of the lower shaft 2. A rack and pinion type steering mechanism that meshes with 2a and is steered by sliding the rack shaft 5 in the axial direction according to the rotation of the lower shaft 2 is configured.

Therefore, when a steering torque is applied to the steered wheels, the upper shaft 1 tends to rotate accordingly, while the lower shaft 2 is constrained from rotating by the resistance applied to the steering mechanism. Torsion corresponding to the magnitude and direction of the steering torque is generated in the torsion bar 3. Reference numeral 6 in the figure denotes a torque sensor that detects the steering torque applied to the steered wheels. In the illustrated torque sensor 6, a magnetic circuit is formed in the connecting portion between the upper shaft 1 and the lower shaft 2, and the torsion bar 3 is formed in this magnetic circuit.
Is a well-known structure in which a change in magnetic resistance caused by the twisting of the output coil is extracted as a change in impedance of the output coil.

A large gear 7a of a hypoid gear 7 is fitted on the outer periphery of the middle portion of the lower shaft 2 with its tooth surface facing downward. The housing 4 is located at a position facing the fitting portion of the large gear 7a,
A stationary bracket 40 having a cylindrical shape is provided so as to project outward, and a steering assisting motor 11 is fixed to an end of the stationary bracket 40 via a transmission housing 10.

A transmission shaft 14 is coaxially supported inside the transmission housing 10. At one end of the transmission shaft 14 extending inside the housing 4 through the fixing bracket 40,
The small gear 7b of the hypoid gear 7 is fitted to the lower shaft 2
The reduction gear device is configured to mesh with a large gear 7a fitted to the lower gear 2 and to reduce and transmit the rotation of the transmission shaft 14 to the lower shaft 2 serving as an input shaft to the steering mechanism. The other end of the transmission shaft 14 is coaxially opposed to the output shaft 11a of the motor 11, and an electromagnetic clutch 12 is formed in the opposed part.

The steering assisting motor 11 is driven based on the detection result of the steering torque by the torque sensor 6,
An output corresponding to the magnitude of the steering torque is generated in the direction of the steering torque applied to the steering wheel. Output shaft
The output of the motor 11 extracted to 11a is the electromagnetic clutch 12
Is transmitted to the transmission shaft 14 via the gear, and then the hypoid gear 7 composed of the small gear 7b and the large gear 7a changes the direction together with deceleration and is transmitted to the lower shaft 2.
A rack shaft 5 that meshes with a pinion 2a formed on the lower shaft 2.
And the rack shaft 5 slides, that is, the steering operation occurs. In this way, the force required to operate the steering wheel for steering is assisted by the generated force of the motor 11.

[0010]

In the conventional power steering apparatus configured as described above, the output of the motor 11 taken out to the output shaft 11a is passed through the electromagnetic clutch 12 and the hypoid gear 7 to the steering mechanism. Lower shaft 2 which is the input shaft of
However, in order to make this transmission go well,
It is important that the gap between the friction plates in the electromagnetic clutch 12 (clutch gap) be properly maintained, and that the backlash at the meshing portion of the large gear 7a and the small gear 7b of the hypoid gear 7 be properly adjusted.

The transmission shaft 14 is supported by a four-point contact ball bearing 13 which is internally fitted and fixed in the transmission housing 10 so as to restrain the movement in the axial direction, and the hypoid gear 7 is mounted on the transmission shaft 14 side. The small gear 7b, which is a constituent member, is integrally formed on one end of the transmission shaft 14, and the armature 22, which is a constituent member of the electromagnetic clutch 12 on the transmission shaft 14 side, is arranged at the other end of the transmission shaft 14 in the axial direction. It is fixed by restraining movement.

Thus, when adjusting the backlash of the hypoid gear 7, when the transmission housing 10 incorporating the transmission shaft 14 is assembled to the fixed bracket 40, a thin plate-shaped shim S1 is provided at the abutting portion of the two to reduce the size. The procedure is performed by changing the axial position of the transmission shaft 14 with the gear 7b fitted therein and optimizing the relative position with respect to the lower shaft 2 with the large gear 7a fitted therein. The gap can be adjusted by changing the axial position of the output shaft 11a of the motor 11 to which the clutch rotor 20 is fixed by inserting the shim S2 at the butting portion between the two when the motor 11 is assembled to the end of the transmission housing 10. Then, the procedure for optimizing the relative position with respect to the transmission shaft 14 to which the armature 22 is fitted is performed.

As described above, in the conventional power steering apparatus, when adjusting the backlash of the hypoid gear 7, the state of meshing between the small gear 7b and the large gear 7a is confirmed, and the space between the fixed bracket 40 and the transmission housing 10 is confirmed. Sim to intervene
By changing the thickness of S1 and reassembling multiple times, when adjusting the clutch gap of the electromagnetic clutch 12, similarly, while checking the gap between the clutch rotor 20 and the armature 22, the gap between the transmission housing 10 and the motor 11 is checked. Sim to intervene in
It was necessary to change the thickness of S2 and reassemble multiple times, and this adjustment work took a lot of time even for a skilled assembler, and there was a problem that the assembly man-hour increased. .

The present invention has been made in view of such circumstances, and the backlash of the gear type speed reducer interposed in the transmission system from the steering assisting motor to the steering mechanism and the clutch gap of the electromagnetic clutch are eliminated. An object of the present invention is to provide a power steering device that can be easily adjusted without complicating troublesome work and can significantly reduce the number of assembly steps.

[0015]

A power steering apparatus according to the present invention supports a transmission shaft inside a transmission housing connected to a part of a steering mechanism, and a steering assisting motor is provided on the other side of the transmission housing. And an electromagnetic clutch between the output shaft of the motor and the transmission shaft, and a gear type speed reducer between the input shaft to the steering mechanism and the transmission shaft, respectively.
An electric motor which is adapted to engage and disengage the rotational force of the motor taken out to the output shaft by the electromagnetic clutch, transmit the torque to the input shaft through deceleration by the speed reducer, and assist the steering operation of the steering mechanism. In a power steering apparatus, a bearing case that is mounted inside the transmission housing so as to be movable in the axial direction and that holds a bearing for supporting the transmission shaft internally, and the movement of the bearing case at an appropriate position. A restraint means for restraining, a constituent member of the electromagnetic clutch that is slidably fitted in an end portion of the transmission shaft on the output shaft side in the axial direction, and the constituent member and a part of the transmission shaft. Intervening between
An urging unit that urges the constituent member toward the motor side is provided.

[0016]

According to the present invention, the bearing for supporting the transmission shaft is fitted and held in the bearing case which is mounted inside the transmission housing so as to be movable in the axial direction. The movement of the bearing case causes the shaft of the transmission shaft to move. The longitudinal position is changed to adjust the backlash of the speed reducer configured with the input shaft to the steering mechanism. After this adjustment, the movement of the bearing case is restrained by the restraining means, whereby the constituent members of the electromagnetic clutch are slidably inserted in the axial direction of the shaft end of the transmission shaft whose axial position is restrained. At the same time, an urging means is interposed between this constituent member and a part of the transmission shaft, and urges toward the motor side fixed to the other side of the transmission housing to form a constituent member of the motor side electromagnetic clutch. The relative positional relationship between the electromagnetic clutch and the electromagnetic clutch is automatically determined, and the clutch gap of the electromagnetic clutch is maintained within an appropriate range.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a vertical sectional view showing a main part of a power steering apparatus according to the present invention. It should be noted that this figure is an enlarged view of a part of the transmission system that transmits the output of the steering assisting motor 11 to the lower shaft 2 of the steering mechanism in the electric power steering apparatus configured as shown in FIG. Is shown.

In the figure, 10 is a transmission housing that coaxially supports a transmission shaft 14 therein. Unlike the transmission housing 10 shown in FIG. 3, the transmission housing 10 is integrally configured so as to project to the outside of the housing 4 that supports the upper shaft 1 and the lower shaft 2, and has an opening at the tip side thereof. A motor 11 for steering assistance is coaxially fixed to the section. Inside the transmission housing 10, a cylindrical bearing case 8 is coaxially mounted at a midway portion in the longitudinal direction, and the transmission shaft 14 is fitted in and held by the bearing case 8. It is supported by a point contact ball bearing 13.

A male screw is formed on the outer periphery of the bearing case 8 from one side over a suitable length, and a female screw corresponding to the male screw is provided on the inner periphery at a predetermined position on the inner periphery of the transmission housing 10. The screw hole 10a is formed with an opening on the fixed side of the motor 11. The bearing case 8 is mounted by inserting the male screw non-forming side into the screw hole 10a first, and screwing the male screw forming portion into the screw hole 10a.
The ring-shaped lock nut 80 is screwed onto the projecting portion of the opening 0a toward the opening side. The bearing case 8 mounted in this way is transmitted by the screwing in the screw hole 10a accompanying the rotation of itself. It is possible to move in the axial direction with respect to the housing 10, and the lock nut at an appropriate moving position.
It is possible to fix it in this position by tightening 80.

The inside of the bearing case 8 is machined to have a larger diameter than the other portion over a predetermined length from the end portion on the insertion side into the screw hole 10a, and the large diameter portion supports the transmission shaft 14 described above. A four-point contact ball bearing 13 is fitted inside. The four-point contact ball bearing 13 is fixed to the inside of the bearing case 8 by being caulked inwardly at the open end of the large diameter portion after caulking inwardly at the open end of the large diameter portion. It is held by restraining its movement in the axial direction.

The transmission shaft 14 is fitted into the inner ring of the four-point contact ball bearing 13 and has a collar 15 fitted to the outer periphery on the motor 11 side, so that the large diameter portion on the other side (the side connected to the steering mechanism). Four-point contact ball bearings 1 supported by holding the inner ring between 16 and
3, and the bearing case 8 holding this is restrained from moving in the axial direction. Further, the transmission shaft 14 has an extension portion to the side of connection with the steering mechanism by a needle roller bearing 17 fitted and fixed in the transmission housing 10 and an extension end to the motor 11 side by an electromagnetic wave which will be described later. The bearings are respectively supported by ball bearings 18 fitted to the shaft center portion of the clutch rotor 20 of the clutch 12, and are supported by these bearings 17 and 18 while allowing movement in the axial direction.

Thus, the transmission shaft 14 is appropriately restricted in its axial position in the transmission housing 10 by the movement of the bearing case 8 as described above, and is restrained in an appropriate movement position by tightening the lock nut 80. It In the power steering apparatus according to the present invention, the backlash adjustment of the hypoid gear 7 (see FIG. 3) at the extension end to the coupling side with the steering mechanism is performed by changing the axial position of the transmission shaft 14 as described above. I do.

FIG. 2 is an explanatory diagram of a procedure for performing backlash adjustment. As shown in the figure, when the bearing case 8 assembled with the transmission shaft 14 is screwed into the screw hole 10a of the transmission housing 10 and the bearing case 8 is rotated and screwed along the screw hole 10a, As a result, the transmission shaft 14 moves in the axial direction, and the small gear 7b of the hypoid gear 7 integrally formed at the end of the transmission shaft 14 becomes the large gear 7a fitted to the lower shaft 2 of the steering mechanism. As it advances toward the end, backlash between both gears 7a, 7b is reduced.

Therefore, the rotation of the bearing case 8 causes the transmission shaft to rotate.
By moving 14 to obtain a state in which the backlash of the hypoid gear 7 is zero, the bearing case 8 is returned and rotated a predetermined number of times from this state, and the lock nut 80 is tightened at this position, whereby the backlash of the hypoid gear 7 is reduced. Can be adjusted accurately. This adjustment can be performed only by the operation of applying a rotational force to the bearing case 8 and the lock nut 80, and the addition of such a rotational force is as shown in FIG.
It can be easily performed from the opening side of the transmission housing 10. Further, after the lock nut 80 is tightened, the position of the transmission shaft 14 in the axial direction is restricted, so that the backlash of the hypoid gear 7 remains in the adjusted state, and the transmission from the transmission shaft 14 to the lower shaft 2 is good. To be done.

The motor 11 for steering assist is fixed to the open end of the transmission housing 10 via the clutch housing 11b after the bearing case 8 is mounted. Output shaft 11a of motor 11
Is coaxially opposed to the shaft end portion of the transmission shaft 14 which is projected into the clutch housing 11b by an appropriate length and is supported in the transmission housing 10 as described above. Electromagnetic clutch 12 to disengage transmission to 14
Is configured.

The electromagnetic clutch 12 is an output shaft 11a of the motor 11.
A clutch rotor 20 press-fitted and fixed to the shaft end of the motor, a drive coil 21 fixed to one surface of the motor 11 facing the inside of the clutch housing 11b, and a shaft end of a transmission shaft 14 facing the output shaft 11a. And an armature 22 attached to the. The clutch rotor 20 is a thick disk-shaped member, and a recess is formed over the entire circumference on the surface facing the motor 11, and the drive coil 21 has a minute gap on the bottom surface of the recess. Are opposed to each other. On the other hand, on the surface of the clutch rotor 20 facing the transmission shaft 14, a support hole 23 having a predetermined depth is formed at the axial center position, and inside the support hole 23, as described above, the shaft end of the transmission shaft 14 is formed. A ball bearing 18 for supporting the portion is fitted, and a friction plate 20a is circumferentially fitted at a position substantially aligned in the radial direction with the concave portion on the other surface side.

Further, the armature 22 of the electromagnetic clutch 12
Is a boss 2 that is splined to the shaft end of the transmission shaft 14.
A disc-shaped holding plate is provided around 2b, and a friction plate 22a is provided on a surface of the holding plate facing the clutch rotor 20 via a thin movable plate.
It is configured to be studded. The friction plate 22a is radially aligned with the friction plate 20a circumferentially attached to the clutch rotor 20.

When the drive coil 21 is excited, the friction plate of the armature 22 is generated by the action of the magnetic field formed in the vicinity of the armature 22 via the clutch rotor 20.
22a causes the clutch rotor 20
The output of the motor 11 that is attracted to the side, comes into sliding contact with the friction plate 20a of the clutch rotor 20, and is taken out to the output shaft 11a is transmitted to the transmission shaft 14 via the clutch rotor 20 and the armature 22, but the drive coil 21 is demagnetized. If yes,
Friction plates 20a and 22a are also released from sliding contact, and motor 11 and transmission shaft 14
The connection with is cut off.

In the electromagnetic clutch 12 having the above-described structure, the armature 22 which is a constituent member on the transmission shaft 14 side is attached by the spline connection of the boss portion 22b to the transmission shaft 14 so as to be slidable in the axial direction. ing. Armature
A coil spring 9 loosely fitted to the transmission shaft 14 is interposed between the boss portion 22b of 22 and the collar 15 fitted to the transmission shaft 14 so as to hold the inner ring of the four-point contact ball bearing 13. The armature 22 is urged toward the motor 11 side by the spring force of the coil spring 9 acting on the boss portion 22b, and the ball bearing 18 fitted to the shaft center portion of the clutch rotor 20 as shown in the drawing. The inner ring is positioned at a position where the end surface of the boss 22b is pressed.

Since the transmission shaft 14 inside the transmission housing 10 is moved in the axial direction in the backlash adjustment of the hypoid gear 7 performed as described above, the relative position of the transmission shaft 14 in the axial direction is determined by the transmission housing 14. The armature 22, which is a constituent member of the electromagnetic clutch 12 on the side of the transmission shaft 14 is urged toward the motor 11 side by the spring force of the coil spring 9, although it is not constant with respect to the motor 11 and the motor 11 fixed thereto. And is pressed against the ball bearing 18 that is integrally fitted to the clutch rotor 20, the positional relationship in the axial direction between the armature 22 and the clutch rotor 20 remains unchanged regardless of the relative position of the transmission shaft 14. Yes, each friction plate 20a, 2
The gap G between 2a is automatically adjusted to a substantially constant value within the range of machining accuracy in the axial direction of the clutch rotor 20 and the armature 22.

That is, in the power steering apparatus according to the present invention, the clutch gap G of the electromagnetic clutch 12 is automatically adjusted when the motor 11 is fixed to the transmission housing 10 without any special adjustment work. That is, the engaging operation of the electromagnetic clutch 12 accompanying the excitation of the drive coil 21, that is, the friction plate 2
The sliding contact between 0a and 22a is always reliably performed under constant conditions. In addition, the coil spring 9 connects the armature 22 to the motor 11
It has a function of urging toward the side, and instead of the coil spring 9, other urging means such as a disc spring and a wave washer may be used. Further, in the present embodiment, the fixing collar 15 of the four-point contact ball bearing 13 is used for interposing the coil spring 9 between the armature 22 and the armature 22. It suffices if it is interposed between a portion of the shaft 14 and, for example, a large diameter portion is provided in the middle of the transmission shaft 14, and the coil spring 9 or another portion is provided between the large diameter portion and the armature 22. You may make it interpose a biasing means.

The steering assisting motor 11 is, as described above,
It is driven to rotate based on the detection result of the steering torque by the torque sensor 6 (see FIG. 3), and the output of the motor 11 is taken out to the transmission shaft 14 via the electromagnetic clutch 12 in the engaged state, and the transmission is performed. It is decelerated by a hypoid gear 7 formed on the other side of the shaft 14 and transmitted to the lower shaft 2, and is further converted into sliding in the axial direction of the rack shaft 5 by meshing between the pinion 2a and the rack shaft 5 for steering. Is assisted.

In order for such steering assist to be performed reliably, it is necessary that the electromagnetic clutch 12 be reliably engaged and that the hypoid gear 7 be smoothly transmitted. In the power steering apparatus according to the present invention, the backlash adjustment of the hypoid gear 7 is performed easily and accurately by moving the transmission shaft 14 together with the bearing case 8 in a stepless manner, and at the end of the transmission housing 10. By fixing the motor 11 via the clutch housing 11b,
Since the clutch gap G of the electromagnetic clutch 12 is automatically optimized, the steering assist by the output of the motor 11 is surely performed and the complicated adjustment work at the time of assembly is not required.

In the above embodiment, the configuration in which the output of the steering assist motor 11 is transmitted to the pinion 2a in the rack and pinion type steering mechanism has been described.
The output of 11 may be directly transmitted to another part of the steering mechanism, for example, to the rack shaft 5, and the present invention provides a steering mechanism of another type such as a ball screw type. It is also possible to apply it to a power steering device provided.

[0035]

As described above in detail, in the power steering apparatus according to the present invention, the transmission shaft for transmitting from the steering assisting motor to the steering mechanism is provided inside the transmission housing in the axial direction. Since it is supported by the bearing case that is movable and can be restrained at each moving position, the backlash adjustment of the reduction gear transmission for input to the steering mechanism can be easily performed by moving the bearing case with respect to the transmission housing. Can be done reliably. Further, the component on the transmission shaft side of the electromagnetic clutch formed between the transmission shaft and the motor is urged toward the motor side by the urging means interposed between the electromagnetic clutch and a part of the transmission shaft. Therefore, by fixing the motor to the transmission housing that supports the transmission shaft, the constituent member is pressed against the constituent member on the motor side, and the clutch gap between them is automatically adjusted to an appropriate value. As a result, the troublesome adjustment work in the transmission system from the steering assisting motor to the steering mechanism becomes unnecessary, and the number of assembling steps is significantly reduced, and the present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part of a power steering apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a procedure for performing backlash adjustment of the reduction gear transmission.

FIG. 3 is a vertical sectional view of a conventional power steering apparatus.

[Explanation of symbols]

 7 Hypoid gear 8 Bearing case 9 Coil spring 10 Transmission housing 11 Motor 11a Output shaft 12 Electromagnetic clutch 13 Four-point contact ball bearing 14 Transmission shaft 15 Collar 20 Clutch rotor 22 Armature 80 Lock nut

Claims (1)

[Claims] 1. A transmission shaft is supported inside a transmission housing connected to a part of a steering mechanism, a steering assisting motor is attached to the other side of the transmission housing, and an output shaft of the motor and the transmission shaft are provided. An electromagnetic clutch is provided between the input shaft and the transmission shaft to the steering mechanism, and a gear type speed reducer is configured between the input shaft and the transmission shaft, respectively, and the rotational force of the motor extracted to the output shaft is generated by the electromagnetic clutch. In an electric power steering device that is engaged and disengaged and transmitted to the input shaft through deceleration by the speed reducer to assist the steering operation of the steering mechanism, in the axial direction of the transmission housing. A movably mounted bearing case for internally fitting and holding the bearing for supporting the transmission shaft, restraining means for restraining the movement of the bearing case at an appropriate position, and an end of the transmission shaft on the output shaft side. Free to slide in the axial direction And a biasing means that is interposed between the component and a part of the transmission shaft and that biases the component toward the motor. A power steering device characterized by: