JPH06183356A - Motor-driven power steering - Google Patents

Abstract

PURPOSE:To enable the steering of wheels with very little steering wheel operating force by actuating a clutch through the engagement of an engaging member with the outer peripheral surface of an output shaft and the inner peripheral surface of a driving shaft by the relative rotation of the input shaft and output shaft at the time of the steering wheel operating force exceeding the set torque. CONSTITUTION:When a steering wheel 11 is rotatory-operated, an input shaft 13 is not rotated much when a steering wheel operating force is the set torque or less, so that a clutch 30 is not actuated. Accordingly, when the steering wheel operating force is small, there is no transmission of torque of an output shaft 15, so that steering wheel operation is performed manually. On the other hand, operating force is transmitted to wheels, and torque is generated to a steering shaft 12. The torque is detected by a sensor 26 provided at the steering shaft 12, and a motor 28 is driven. The rotation of the motor 28 is transmitted to a driving shaft 31 through gear reduction mechanism 29, then to the output shaft 15 and further to the wheels through a pinion shaft 23, a pinion 24 and a rack 25. Changeover to a power steering is thus performed in the case of the steering wheel operating force exceeding the set torque.

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 device for assisting steering by an electric motor.

[0002]

2. Description of the Related Art FIG. 14 shows a general structure of an electric power steering system. In this device, when the handle 1 is rotated right or left, torque is generated on the handle shaft 3 due to resistance from the wheels 2. This torque is the handle shaft 3
It is detected by the sensor 4 provided in the above, and the motor 6 is driven through the control device 5. The drive shaft of the motor 6 is connected to the pinion 9 of the handle shaft 3 via a speed reducer 7 and a clutch 8, and the wheels 2 are steered via a rack 10 engaged with the pinion 9. As a result, the wheels 2 can be steered with a very slight steering wheel operating force.

[0003]

However, in such an electric power steering device, when an abnormality occurs in the drive system including the control device 5, the motor 6 and the speed reducer 7 and they do not operate, the steering wheel is operated. Since the speed reducer 7 and the motor 6 are connected to the shaft 3, there is a problem that the steering wheel manual operation force becomes excessive and steering becomes substantially impossible.

According to the present invention, the conventional rolling problem is solved, and even if an abnormality occurs in the drive system for assisting steering, the clutch can be mechanically disengaged by the relative displacement of the input shaft and the output shaft. Thus, it is a technical subject to improve the safety and reliability of the electric power steering device.

[0005]

In order to solve the above problems, in the first invention, an input shaft connected to a steering wheel, an output shaft connected to a wheel steering gear, and an output shaft In an electric power steering device including a sensor that detects a rotational torque, a motor controlled by an output from the sensor, and a clutch that interrupts rotation transmission from the motor to the output shaft, the input shaft and the output shaft A cylinder in which an elastic member that transmits the rotation of the input shaft to the output shaft and elastically deforms when the transmitted torque exceeds a set torque is provided, and the clutch is provided outside the output shaft and concentrically with the output shaft. A drive shaft, and an engaging member that is provided between the drive shaft and the output shaft and that operates in conjunction with the relative displacement of the input shaft with respect to the output shaft to engage the drive shaft and the output shaft. , With the motor It was constructed out with providing the gear reduction mechanism for transmitting the rotation of the motor to the outer ring between the shaft.

In the second aspect of the invention, the input shaft connected to the steering wheel, the output shaft connected to the wheel steering gear, the sensor for detecting the rotational torque to the output shaft, and the output from the sensor. In an electric power steering device comprising a motor controlled by the motor and a clutch for intermittently transmitting rotation transmission from the motor to the output shaft, the output shaft is cylindrical and is provided concentrically outside the input shaft, and its output An elastic member that transmits the rotation of the input shaft to the output shaft and elastically deforms when the transmitted torque exceeds a set torque is provided between the shaft and the input shaft. The motor includes a drive shaft concentrically rotated by the motor, and an engagement member that operates in association with relative displacement of the input shaft with respect to the output shaft to engage the drive shaft and the output shaft. It has a configuration in which a gear reduction mechanism for transmitting the rotation of the motor to the outer ring between the outer ring.

[0007]

According to the first aspect of the invention, when the operating force of the handle connected to the input shaft is less than the set torque of the elastic member, the manual operating force is transmitted from the input shaft to the output shaft through the elastic member. It When the operating force of the handle exceeds the set torque, the engaging member engages with the outer peripheral surface of the output shaft and the inner peripheral surface of the drive shaft due to the relative rotation between the input shaft and the output shaft, the clutch operates, and the motor rotates. Is transmitted to the output shaft via the gear reduction mechanism.

As a result, it becomes possible to steer the wheels with a very small steering wheel operating force.

If an abnormality occurs in the drive system including the motor and the handle operating force exceeds the set torque of the elastic member, the engagement member rotates the drive shaft due to the relative rotation of the input shaft and the output shaft. Although it is in the state of being transmitted to the output shaft, with respect to the rotational movement from the input shaft, the engaging member slides on the inner peripheral surface of the drive shaft, and the handle operating force is transmitted to the output shaft in the state of being disconnected from the drive system, and the manual operation is performed. Steering by.

Further, when the steering wheel is returned from the wheel side at the time of recovering from a curve, the driver applies only a torque such that the steering wheel is lightly slid by hand, so the torque is less than the set torque, and the drive system means clutch operation. Without doing so, it becomes a state of operation.

Therefore, by properly setting the spring force of the elastic member, manual operation is performed below the set torque, power steering is automatically switched over when the set torque is exceeded, and an abnormality occurs in the drive system including the motor and the like. Even when it is done, the manual operation of the steering wheel does not become excessive, and the steering wheel can be returned smoothly without giving a feeling of discomfort when the vehicle recovers from a curve.

Also in the second invention, when the rotational torque of the input shaft exceeds the set torque of the elastic member, the engaging member engages with the outer peripheral surface of the drive shaft and the inner peripheral surface of the output shaft, and the input shaft and the drive shaft are driven. The rotation of the shaft can be transmitted to the output shaft.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. As shown in FIGS. 1 and 2, an input shaft 13 is connected to a handle shaft 12 having a handle 11.

The input shaft 13 has a cylindrical retainer 14 at its end, and the angular shaft 16 provided at the end of the output shaft 15 is inserted inside the retainer 14.

A small-diameter shaft portion 17 is provided on the end surface of the square shaft portion 16, and the small-diameter shaft portion 17 is inserted into a shaft insertion hole 18 formed at the closed end of the cage 14 and is rotatable via a bearing 19. Supported by.

As shown in FIGS. 3 and 4, the angular shaft portion 16
A pin 20 facing the outer diameter direction is provided on the outer periphery of the pin 20, and the pin 20 is inserted into a pin hole 21 formed in the cage 14. The pin hole 21 is a long hole extending in the circumferential direction of the cage 12, and a rotational clearance A is provided between both ends of the pin hole 21 and the pin 20.

Further, elastic members 22 made of springs are incorporated on both sides of the pin 20 in the pin hole 21, and the elastic member 22 holds the pin 20 at the neutral position of the clearance A in the rotational direction.

Here, the spring force of the elastic member 22 is elastically deformed until the clearance A in the rotational direction is eliminated when the input shaft 13 is subjected to a rotational force of a certain amount or more, and the retainer 14 and the output shaft 15 are then deformed. And are determined to engage via pin 20.

As shown in FIG. 1, a pinion shaft 23 is connected to the output shaft 15, and a pinion 24 as a wheel steering gear provided on the pinion shaft 23 meshes with a rack 25.

The handle shaft 12 is provided with a sensor 26 for detecting the rotational torque applied to the output shaft 15, and the output of the sensor 26 is input to the controller 27. Control device 27
Controls the motor 28. The rotation of the motor 28 is transmitted to the output shaft 15 via the gear reduction mechanism 29 and the clutch 30.

As shown in FIGS. 2 and 3, the clutch 3
Reference numeral 0 includes a cylindrical drive shaft 31 rotated by the gear reduction mechanism 29, and a pair of engagement members 32 a and 32 b that engage the drive shaft 31 and the output shaft 15. The drive shaft 31 is
It is provided on the outside of the cage 14 and is rotatably supported by the input shaft 13 and the output shaft 15 via two bearings 33, 33.

The pair of engaging members 32a and 32b are housed in a pocket 34 formed in the cage 14. The pair of engaging members 32a and 32b are pressed by the elastic body 35 and are pressed against the wall surfaces 34a of the pocket 34 that face each other in the circumferential direction. Each of the engaging members 32a and 32b is provided on either the flat surface 16a of the angular shaft portion 16 or the cylindrical inner surface 31a of the outer ring 31 when the pin 20 shown in FIG. 4 is located at the neutral position of the clearance A in the rotational direction. Is also not engaged.

The electric power steering apparatus shown in the embodiment has the above structure, and its operation will be described below.

Now, when the handle 11 is rotated and a rotational force in the direction shown by the arrow in FIG. 4 is applied to the input shaft 12, if the handle operating force is equal to or less than the set torque of the elastic member 22, the elastic member 22 will be described. Of the engaging member 32 because the input shaft 13 does not rotate much with respect to the output shaft 15.
a and 32b do not engage with the flat surface 16a of the angular shaft portion 16 of the output shaft 15 and the cylindrical inner surface 31a of the drive shaft 31, and the clutch 30 does not operate.

Therefore, when the steering wheel operating force is small, the rotational force of the output shaft 15 is not transmitted from the outer ring 31, and the steering wheel is operated manually.

The handle operating force is increased, and the elastic member 2
When the set torque of 2 is exceeded, as shown in FIG. 5, the cage 14 of the input shaft 13 elastically deforms the elastic member 22 and relatively rotates with respect to the output shaft 15 until the clearance A in the rotational direction disappears. The operating force is transmitted from 14 to the wheels via the pin 20, the output shaft 15, the pinion shaft 23, the pinion 24, and the rack 25.

At the same time, the cage 14 is rotated relative to the output shaft 15 so that the left engagement member 32a of the pair of engagement members 32a and 32b housed in the pocket 34 is rotated by the elastic force of the elastic body 35. The flat surface 16a of the portion 16 and the cylindrical inner surface 31a of the drive shaft 31 are brought into contact with each other to form a wedge state.

On the other hand, when the operating force is transmitted to the wheels, a torque is generated on the handle shaft 12 due to the resistance from the wheels. This torque is detected by the sensor 26 provided on the handle shaft 12, and the motor 28 is driven through the control device 27. Let The rotation of the motor 28 is transmitted to the drive shaft 31 via the gear reduction mechanism 29. At this time, since the clutch is already in operation, the rotation of the motor 28 is transmitted from the drive shaft 31 to the output shaft 15 via the engaging member 32a, and the pinion shaft 2
3, transmitted to the wheels via the pinion 24 and the rack 25.

As described above, when the steering wheel operating force exceeds the set torque, the steering mode is switched to the power steering, and the wheels can be steered with a very slight steering wheel operating force.

In the unlikely event that an abnormality occurs in the drive system including the control device 27 and the motor 28 and they do not operate, when the handle 11 is operated, the input shaft 13 connected to the handle shaft 12 is rotated. . When the input shaft 13 is rotated relative to the output shaft 15 in the leftward direction in FIG. 4, for example, the engagement member 32a is pushed in the circumferential direction to enter the state shown in FIG.
Since the elastic member 22 is elastically deformed and the retainer 14 and the output shaft 15 are engaged with each other via the pin 20, the output shaft 15 also manually rotates relative to the left, and the clutch does not operate,
The engaging member 32a moves in the circumferential direction while sliding on the cylindrical inner surface 31a of the drive shaft 31.

Therefore, from the input shaft 13 to the pin 20, the output shaft 15, the pinion shaft 23, the pinion 24, and the rack 25.
The manual operation force is transmitted to the wheels via the vehicle and is disconnected from the drive system, so that the manual handle operation force does not become excessive.

Further, the operation when the steering wheel is returned from the wheel side when the drive system does not operate will be described.

At the time of recovery from the curve, the force is transmitted from the wheels to the rack 25, the pinion 24, the pinion shaft 23, and the output shaft 15. Since the driver applies only a torque to the extent that the steering wheel is lightly slipped by the steering wheel returning force, the torque is less than the set torque of the elastic member 22. In this case, since the input shaft 13 does not rotate relatively relative to the output shaft 15, the engaging members 32a and 32b housed in the pockets 34 of the cage 14 have the cylindrical inner surface 31a of the drive shaft 31 and the angular shaft portion 16 respectively. It does not engage with the flat surface 16a. Therefore, the clutch 30 does not operate, and the input shaft 13 and the handle 11 connected to the input shaft 13 are returned with the output shaft 15 being disconnected from the drive shaft 31 (non-rotatable).

Therefore, at the time of recovering from the curve, the steering wheel can be smoothly returned without giving the driver a feeling of strangeness.

In the embodiment shown in FIGS. 2 to 5, the input shaft 1
A spring is used as the elastic member 22 that transmits the rotation of 3 to the output shaft 15, but the elastic member 22 is not limited to this. For example, as shown in FIGS. 6 and 7, an elastic member 22 composed of a torsion bar may be used.

When the elastic member 22 composed of a torsion bar is used, the input shaft 13 and the output shaft 15 are provided with holes 3 in the axial direction.
6 is formed, the elastic member 22 formed of a torsion bar is inserted into the hole 36, and each shaft 13, 1 is inserted through the holder 37.
Fix at 5. Instead of such an elastic member 22 made of a torsion bar, an elastic member 22 made of a leaf spring may be used as shown in FIG.

FIG. 9 shows another embodiment of the electric power steering device. In this embodiment, the output shaft 15 connected to the pinion shaft 23 of FIG. 1 has a tubular shape, and the output shaft 15 is provided outside the cage 14 of the input shaft 13.

The drive shaft 31 forming the clutch 30
Is inserted inside the cage 14, and the rotation of the motor 28 shown in FIG. 1 is transmitted to its drive shaft 31.

Further, a pair of engaging members 32a, 32b inserted in the pocket 34 of the cage 14 are formed on the inner peripheral surface of the output shaft 15 when the input shaft 13 and the output shaft 15 rotate relative to each other. And the outer peripheral surface 31b of the drive shaft 31.

In the embodiment, a pair of engaging members 32 are used.
Although a coil spring is used as the elastic body 35 that presses a and 32b in opposite directions, a leaf spring may be used as shown in FIGS. 10 and 11. In this leaf spring, inclined piece portions b are provided at both end portions of a first pressing piece portion a that presses one of the pair of engaging members 32a and 32b, and both end portions of the inclined piece portion b are provided. A second pressing piece portion c for pressing the other engaging member 32b is formed on the.

As shown in FIGS. 12 and 13, a bent piece d that engages with both end surfaces of the other engaging member 32b is provided at the end of the second pressing piece c, and the first pressing piece a is provided. , The inclined pieces b and the second pressing pieces c respectively, the engaging members 32a, 3
If a leaf spring formed with a slit e into which a part of 2b fits can be used, the cage 14 and the output shaft 15 can be rotated relatively greatly, so that the clutch using the leaf spring shown in FIG. In comparison, the operating angle of the clutch can be increased.

When the operating angles are the same, the outer diameters of the engaging members 32a and 32b can be increased, and the capacity of the clutch can be increased.

[0043]

As described above, in the electric power steering apparatus according to the present invention, when the steering wheel operating force is less than the set torque of the elastic member, the manual operation is performed, and when the set torque exceeds the set torque, the power steering is automatically switched. In addition, when an abnormality occurs in the drive system that drives the drive shaft, the steering wheel operating force can be transmitted to the steering gear in a state where the drive system is disconnected from the drive system. The safety of the electric power steering device can be improved.

Further, since the input shaft and the output shaft are connected by the mechanical engagement structure and the rotation of the motor is transmitted to the outer ring through the gear reduction mechanism, the reliability of the transmission can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an electric power steering device according to the present invention.

FIG. 2 is a cross-sectional view showing the torque transmitting portion of the above.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is an enlarged sectional view of the above.

FIG. 5 is a sectional view showing an operating state of the above.

FIG. 6 is a cross-sectional view showing another example of the above torque transmitting portion.

7 is a sectional view taken along line VII-VII of FIG.

FIG. 8 is a cross-sectional view showing still another example of the torque transmission unit of the above.

FIG. 9 is a sectional view showing another embodiment of the electric power steering apparatus according to the present invention.

FIG. 10 is a plan view showing another example of an elastic body that presses the engaging member.

11 is a sectional view taken along line XI-XI of FIG.

FIG. 12 is a plan view showing still another example of the elastic body.

13 is a sectional view taken along line XIII-XIII in FIG.

FIG. 14 is a schematic view showing a conventional electric power steering device.

[Explanation of symbols]

 11 Handle 13 Input Shaft 15 Output Shaft 22 Elastic Member 26 Sensor 28 Motor 29 Gear Reduction Mechanism 30 Clutch 31 Drive Shaft 32a, 32b Engaging Member

Claims (2)

[Claims] 1. An input shaft connected to a steering wheel, an output shaft connected to a wheel steering gear, a sensor for detecting a rotational torque to the output shaft, and a motor controlled by an output from the sensor. In an electric power steering device including a clutch for intermittently transmitting rotation transmission from the motor to the output shaft, the rotation of the input shaft is transmitted to the output shaft between the input shaft and the output shaft, and the transmission torque produces a set torque. An elastic member that elastically deforms when the clutch is crossed is provided, and the clutch is
A cylindrical drive shaft concentric with the output shaft on the outside of the output shaft, and between the drive shaft and the output shaft, the drive shaft is operated in conjunction with the relative displacement of the input shaft with respect to the output shaft. An electric power steering device comprising an engagement member that engages a shaft and an output shaft, and a gear reduction mechanism that transmits rotation of the motor to the outer wheel is provided between the motor and the outer wheel. 2. An input shaft connected to a steering wheel, an output shaft connected to a wheel steering gear, a sensor for detecting a rotational torque to the output shaft, and a motor controlled by an output from the sensor. In an electric power steering device including a clutch for intermittently transmitting rotation transmission from the motor to the output shaft, the output shaft is cylindrical and is provided concentrically outside the input shaft, and between the output shaft and the input shaft. An elastic member that transmits the rotation of the input shaft to the output shaft and elastically deforms when the transmitted torque exceeds a set torque is provided, and the clutch is provided inside the output shaft and concentric with the output shaft. A drive shaft rotated by the drive shaft, and an engagement member that operates in association with the relative displacement of the input shaft with respect to the output shaft to engage the drive shaft and the output shaft. Rotation An electric power steering device comprising a gear reduction mechanism for transmitting to an outer wheel.