JPH01218973A - Electric motor-driven power steering device - Google Patents

Abstract

PURPOSE:To improve the reliability of a device preventing a motor from transmitting its drive power to an output shaft by disconnecting a clutch, when the motor is in trouble, by transmitting rotation of the electric driven motor to the output shaft through the clutch. CONSTITUTION:Three holes 11d are provided in a position with an equal space in an angular part 11c formed in a large contour part 11b of an input shaft 11. A column-shaped roll 22 is fitted into the hole 11d in a manner wherein the axial center of the roll agrees with the axial direction of input and output shafts 11, 12, and a spring 33 is mounted interposing between the paired rolls 22. The roll 22 is pressed to an end face of the hole 11d in its peripheral direction while adapted to one end face of a hexagonal part 12b, and a clutch is constituted of the angular part 11c, hexagonal part 12b, rolls 22 and an outer sleeve 23. The clutch is formed so as to transmit rotation from the outer sleeve 23 to the output shaft 12 only when relative rotation of the input shaft 11 is in a value not less than a certain preset value further with a direction of the relative rotation agreeing with a direction of rotation of the outer sleeve 23.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an electric power steering for a vehicle that uses an electric motor as a power source in order to reduce the steering force of the steering wheel of the vehicle. More specifically, the present invention relates to an electric power steering device equipped with a clutch device for ensuring fail-safety in the event of an abnormality such as a failure of the electric motor.

(Prior art) As the above-mentioned conventional device, for example,
There was something shown in No. 853.

This device drives an electric motor using a control circuit in response to a signal from a torque detector that detects steering torque generated between an input shaft and an output shaft or a signal from a vehicle speed detector, and transfers the driving force of the electric motor to a clutch. The power is transmitted to the output shaft via the speed reducer and reduces the steering force of the steering wheel connected to the input shaft. In addition, this device uses an electromagnetic clutch that is controlled by the same control circuit as the clutch that is interposed between the electric motor and the reducer.
The electromagnetic clutch is controlled to 0N by a control circuit according to the vehicle speed.
The steering feeling is improved by -OFF control, and by turning OFF when an abnormality occurs, manual steering is possible and fail-safe.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional device, an electromagnetic clutch that is controlled ON-OFF by a control circuit is used as a clutch interposed between the electric motor and the reduction gear. There is a possibility that the electromagnetic clutch may become inoperable due to factors other than the clutch itself, such as malfunction of the control circuit, and the steering feeling may deteriorate significantly. In other words, for example, when the electric motor malfunctions and becomes unable to rotate, the electromagnetic clutch may not be turned off due to factors other than the electromagnetic clutch itself as described above, and steering becomes impossible. Even if the electric motor is rotated in a direction opposite to the direction of rotation input to the input shaft, the clutch may not be turned off and steering may become impossible.

In addition, in the conventional device described above, when the electric motor becomes unable to rotate due to foreign matter getting caught, etc., it is not possible to immediately detect the abnormality, so the electromagnetic clutch is not turned off and steering becomes impossible. turn into. As described above, the conventional devices have a problem in that the safety and reliability of the electric power steering device cannot be sufficiently ensured.

Therefore, in view of the above-mentioned conventional problems, the present invention aims to improve the safety and reliability of an electric power steering device when an electric motor is abnormal, etc., and to improve the steering feeling of the electric power steering device.
This is a technical issue.

[Structure of the invention]

(Means for Solving the Problems) The measures taken to solve the above technical problems are the steering torque applied between the input shaft connected to the steering wheel of the vehicle and the output shaft connected to the steering gear. a steering torque detector that detects a steering torque detector; an electric motor whose rotation is controlled by a control signal from a control means in response to a detection signal from the steering torque detector, and whose rotation is transmitted to an output shaft; In an electric power steering device equipped with a clutch that is interposed between the shafts and controls the transmission of the rotation of the electric motor to the output shaft on and off, the elasticity of the elastic body that connects the steering torque detector to the input shaft and the output shaft is The steering torque is detected in accordance with the deformation, and the engagement and disengagement of the clutch is controlled by the elastic deformation of the elastic body. This is made smaller than the elastic deformation of the elastic body when the motor starts rotating.

(Function) According to the above configuration, even if the electric motor is rotated in the opposite direction to the rotation according to the steering torque detected by the steering torque detector due to malfunction of the control means, etc., the clutch is rotated by the elastic body. The on/off is controlled by elastic deformation, and only when the direction of rotation of the electric motor and the direction of elastic deformation of the elastic body match, the electric motor engages to transmit the rotation of the electric motor to the output shaft. When the two do not match, the clutch is always disengaged and no force is transmitted between the electric motor and the output shaft, so manual steering is possible and the steering operation is not disabled.

Furthermore, according to the above configuration, when the direction of rotation of the electric motor and the direction of elastic deformation of the elastic body match, the electric motor starts rotating after the clutch has been engaged in advance, and the rotation of the electric motor is controlled via the clutch. Since the power is transmitted to the output shaft, shocks and the like are not transmitted to the steering wheel via the input shaft, resulting in a smooth steering feel.

(Example) Hereinafter, an example of an electric power steering device according to the present invention will be described based on the drawings.

In FIGS. 1 and 2, the input shaft 11, which has one end connected to the steering wheel 10, has a hollow stepped cylindrical shape, and the other end is one end of the torsion bar 13, which is connected to the output shaft 12 by a pin 15b. are connected to each other by a bottle 15a. As a result, the input shaft 11 is connected to an output shaft 12 connected to a steering gear (not shown) of the vehicle via the torsion bar 13, and one end of the output shaft 12 is allowed to play freely within the large diameter portion 11b of the input shaft 11. The steering force applied to the input shaft 11 is transmitted to the output shaft 12 via the torsion bar 13. Note that the torsion bar 13 constitutes an elastic body in the present invention.

The input shaft 11 is rotatably supported on the steering wheel 10 side by a bearing 16 press-fitted into the upper housing 14a, and the output shaft 12 is rotatably supported by a bearing 17 press-fitted into the lower housing 14b. has been done.

A dust cover 36 is fitted on the outer periphery of the small diameter portion 11a of the input shaft 11 on the outside of the upper housing 14a, and a finger-like portion of a cylindrical slider 18 as shown in FIG. 4 is fitted inside the upper housing 14a. 18b is loosely fitted, and the output shafts 1 and 2 are loosely fitted on the output shaft 12 side of the slider.
A radial hole 18a is provided in which a ball 19 is fitted to be engaged with a spiral groove 12a formed on the outer peripheral surface of the radial hole 18a. Three finger-like portions 18b are formed at equal intervals, and each finger-like portion 18b is loosely fitted into a through hole lie formed in a stepped portion of the input shaft 11.

A ring 20 having flanges at both ends and forming an annular groove 20a between the two flanges is fixed to the outer periphery of the finger-like portion 18b of the slider 18 so as to be integral with the slider 18. Furthermore, an elongated hole 18c in the axial direction into which a bottle 21 fixedly attached to the input shaft 11 is inserted is formed on the outer periphery of one of the finger-like portions 18b of the slider 18. It is integrally rotatable and can freely move in the axial direction.

The outer circumferential surface of the output shaft 12 is provided with the aforementioned spiral groove 12a.
is engraved, and a hexagonal hexagonal portion 12b is formed. The large diameter portion 11b of the input shaft 11 is the output shaft 12
It extends to the hexagonal part 12b of the large diameter part 11b, and the fitting surface with the hexagonal part 12b of the large diameter part 11b has a hexagonal part corresponding to the hexagonal part 12b.
A corner portion 11c having a square shape is formed, and the corner portion 1
A predetermined gap is formed between 1c and the hexagonal portion 12b.

A corner portion 11C formed in the large diameter portion 11b of the input shaft 11 is provided with three holes lid at equally spaced positions. Each hole
A pair of cylindrical rollers 22 are inserted into the id so that their axes coincide with the axial direction of the output shafts 11 and 12, respectively, as shown in an enlarged view of one part in FIG. 3a. A plate-shaped spring 33 is interposed between each pair of rollers 22. As a result, each roller 22 has a hole 11
The hexagonal portion 12b is pressed against the circumferential end surface of d.
The corner portion 11c, the hexagonal portion 12b,
The rollers 22 and the outer sleeve 23 constitute a clutch in the present invention.

Further, on the outside of the large diameter portion 11b of the input shaft 11, an outer sleeve 23 is press-fitted into the upper housing 14a so that a predetermined gap l is formed between the outer sleeve 23 and the output shaft 12. It is rotatably supported by a bearing 32 fixedly attached to the bearing 32 . A gear 23a is formed on the outer peripheral surface of the outer sleeve 23, and meshes with a worm gear 25 fixed to the output shaft 24a of the electric motor 24.
The worm gear 25 and the gear 23a constitute the reduction gear of the present invention. Note that in FIG. 1, 30° 31 is a bearing that supports the large diameter portion 11b of the input shaft 11 and the outer sleeve 23, respectively.

Further, a case 26 is attached to the upper housing 14a, and a ball 27 is provided at one end of the case 26.
A lever 2 consisting of a leaf spring-like metal plate holding a
The other end of 8 is fixed.

The ball 27 held at one end of the lever 28 is connected to the ring 20
The lever 28 is fitted into an annular groove 20a, and a strain gauge (not shown) forming a resistance bridge is attached to the side surface of the lever 28, which is coated with an insulating layer. The strain gauge constitutes a well-known strain detection circuit consisting of a bridge circuit, and the electrical signal from the strain gauge is input to the control circuit 29, which controls the electric motor 24 in accordance with the electrical signal. Control the supply current.

The operation of this embodiment having the above configuration will be explained.

When the steering wheel 10 is rotated, the input shaft 11
The torsion bar 13 is twisted with respect to the output shaft 12 connected to the steering gear, which rotates and is subjected to a load such as a road reaction force, and a relative rotation occurs between the output shaft 12 and the input shaft 11.

As a result, the relative rotation of this input shaft 11, that is, the output shaft 1
2, the slider 18 rotates relative to the spiral groove 12a, and this rotation applies a thrust in the axial direction of the input shaft 11 to the slider 18 via the ball 19.
The slider 18 is rotated in the rotation direction of the input shaft 11 and
axially displaced according to the relative rotation of the Slider 18
The axial displacement of the ring 20 is determined by bending the lever 28 that holds the ring 20 via the ball 27 that engages with the annular groove 20a of the ring 20, and applying electricity to the strain gauge according to the amount of relative rotation between the input shaft 11 and the output shaft 12. generate a signal. This electric signal is input to the control circuit 29, and the control circuit 29 sends a supply current according to this electric signal to the electric motor 24, rotates the electric motor 24 in a direction corresponding to the rotation direction of the input shaft 11, and The rotation of the motor 24 is decelerated by the worm gear 25 and the gear 23a, and is transmitted to the outer sleeve 23.

At this time, in the present invention, the relationship between the relative rotation between the input shaft 11 and the output shaft 12 (elastic deformation of the torsion bar 13 - steering torque T) and the supply current I of the electric motor 24 is as shown in FIG. It has become.

That is, as shown in FIG. 3b, the gap l between the rollers 22 and the outer sleeve 23 on the rotational direction side disappears, and the relative rotation between the input shaft 11 and the output shaft 12 (the elasticity of the torsion bar 130) occurs when the clutch is activated. Deformation - steering torque TI)
However, when the lever 28 is bent due to the axial displacement of the slider 18 and the electric motor 24 starts rotating due to the supplied current controlled by the control circuit 29 according to the signal from the strain gauge, the input shaft 11 and the output shaft 12 (elastic deformation of the torsion bar 13 - steering torque T3), as shown in FIG. 3b, the input shaft 11
After the rollers 22 on the rotation direction side are crimped to the inner circumferential surface of the outer sleeve 23 and the end surface of the hexagonal portion 12b due to the relative rotation of the communicated. As a result, the roller 22 on the rotation direction side is connected to the inner circumferential surface of the outer sleeve 23.
In a state where the outer sleeve 23 is crimped to the end surface of the corner portion 12b, the rotation of the outer sleeve 23 is smoothly transmitted to the output shaft 12 via the rollers 22, thereby assisting the steering force applied by the steering wheel 10. Here, the rotation direction of the outer sleeve 23 is determined by the control circuit 29 controlling the rotation of the electric motor 24 at a rotation speed and in a rotation direction according to the relative rotation of the input shaft 11. The direction of relative rotation of the matched input shafts 11 is made to match. As a result, the rollers 22 are strongly pressed against the hexagonal portion 12b by the frictional force thereof, and rotational force is reliably transmitted. Note that the relative rotation between the input shaft 11 and the output shaft 12 (
The relationship between the elastic deformation of the torsion bar 13 (steering torque T) and the supply current I of the electric motor 24 is as shown in FIG. The steering torque T2 at the time of stopping has hysteresis to prevent fluctuations in the rotation of the electric motor 24 due to disturbances such as noise. Furthermore, the relative rotation (steering torque Tl) between the input shaft 11 and the output shaft 12 when the gap l between the rollers 22 on the rotation direction side and the outer sleeve 23 disappears and the clutch becomes operable is the outer sleeve 23 inner diameter dimensions,
Outer diameter of roller 22.

It can be arbitrarily set by various combinations of the two dimensions of the hexagonal portion 12b of the output shaft 12, the hole 11d of the input shaft 11, the spring constant and dimensions of the spring 33, etc.

In this way, the clutch operates when the relative rotation of the input shaft 11 (steering torque T) is equal to or greater than a certain set value (steering torque T1), and
The rotation from the outer sleeve 23 is transmitted to the output shaft 12 only when the direction of relative rotation matches the direction of rotation of the outer sleeve 23. Therefore, even if the electric motor 24 is rotated in the opposite direction to the rotation direction according to the relative rotation of the input shaft 11 due to a malfunction of the control circuit 29, the rollers 22 on the rotation direction side in FIG. 23 and the end surface of the hexagonal portion 12b, the outer sleeve 23 vibrates and rotates within the hole lid due to the frictional force with the outer sleeve 23, and the rotation of the outer sleeve 23 is not transmitted to the input shaft 11. (The rotation of the input shaft 11 is transmitted to the output shaft 12 via the rollers 22 and the torsion bar 13, and manual steering is possible.In addition, the electric motor 24 may catch a foreign object and become unable to rotate. Even if 23 becomes unable to rotate,
In FIG. 3b, the rollers 22 on the rotational direction side vibrate against the spring 33 due to the frictional force with the outer sleeve 23, or rotate, so that the rotation of the input shaft 11 is transferred to the output shaft 12 via the rollers 22. transmission and manual steering.

Furthermore, when the steering wheel 10 is held and the outer sleeve 23 is locked, the clutch operates to maintain the held state of the steering wheel 10, and the steering wheel 10 is in a free state (when the steering wheel 10 is turned in and released). When the outer sleeve 23 rotates in the forward and reverse directions, the clutch operates to prevent the steering wheel 10 from being obstructed from returning. Further, when the steering wheel 10 is further turned in and the outer sleeve 23 is rotating in the forward direction, if the rotational torque of the electric motor 24 suddenly increases due to a malfunction of the control circuit 29, etc., the input shaft 11 side As a result, the elastic deformation of the torsion bar 13 is reversed, and the clutch operates to cut off the rotational transmission from the outer sleeve 23 to the output shaft 12. Also, when the vehicle is traveling straight, the control circuit 29 is activated. Even if the electric motor 24 rotates due to a malfunction or the like, the clutch will prevent the relative rotation of the input shaft 11 and output shaft 12 (elastic deformation of the torsion bar 13) from the road reaction force.
Unless the steering torque T) exceeds the set value (steering torque Tl), no force is transmitted between the outer sleeve 23 and the output shaft 12, so the steering wheel 10 is not suddenly turned.

As described above, according to the present embodiment, the clutch operates to connect and disconnect rotation transmission between the electric motor 24 and the reduction gear by utilizing the elastic deformation of the torsion bar 13 for detecting the relative rotation of the input shaft 11. By controlling the electric power steering, the safety and reliability of the electric power steering can be improved, and the device can be downsized. Moreover, the steering feeling of the electric power steering device can be improved.

FIG. 6 shows a modification of the electric power steering device according to the present invention. In this embodiment, relative rotation occurring between the input shaft and the output shaft in the embodiment shown in FIG. The only difference is that the relative rotation is directly detected, whereas the axial direction conversion mechanism is provided, and the other configuration 5 functions are the same as the embodiment shown in FIG. 2, so the details will be explained here. Further explanation will be omitted.

In FIG. 6, a flange portion 111e is formed at the end of the large diameter portion 111b of the input shaft 111, and the output shaft 11
A flange portion 112C is formed on the outer circumferential surface of 2. A brush 1 is installed between the end faces of both flanges 1lle and 112c.
A slip ring is configured with 34 in between, so that an electric signal corresponding to the relative rotation between the two is detected. In this embodiment, the configuration for detecting relative rotation is simple, and since the number of parts is small, there is little backlash between each member, and highly accurate detection is possible. In addition,
In FIG. 6, the same configuration as the embodiment shown in FIG.
The numbers are given by adding 100 to the numbers shown in the figures.

In the above two embodiments, examples were explained in which a cantilever type using a strain gauge and a slip ring type were used as detectors for extracting the relative rotation of the input shaft as an electric signal. It is also possible to employ a detector or the like in the present invention.

〔Effect of the invention〕

According to the present invention, the steering torque detector detects the steering torque in accordance with the elastic deformation of the elastic body that connects the input shaft and the output shaft, and the engagement and disengagement of the clutch is determined based on the steering torque detected by the steering torque detector. It is controlled by the rotation of the electric motor and the elastic deformation of the elastic body.

Therefore, even if the electric motor is rotated in the opposite direction to the rotation according to the steering torque detected by the steering torque detector due to a malfunction of the control means, the clutch will rotate according to the steering torque detected by the steering torque detector. The connection is controlled by the corresponding rotation and the elastic deformation of the elastic body, and the rotation of the electric motor is transmitted to the output shaft only when the direction of rotation of the reducer by the electric motor and the direction of elastic deformation of the elastic body match. When the two match, the clutch always disengages and no force is transmitted between the electric motor and the output shaft.
Manual steering becomes possible and the steering operation is not disabled. Therefore, the safety and reliability of the electric power steering device can be improved.

Furthermore, since the steering torque detector and the clutch in the present invention share an elastic body that requires a large space,
Electric power steering can be made more compact.

Furthermore, according to the present invention, the elastic deformation of the elastic body when the clutch is activated is greater than the elastic deformation of the elastic body when the steering torque detector detects the steering torque and the electric motor starts rotating accordingly. It has also been made smaller.

Therefore, the rotation of the electric motor starts after the clutch is activated in advance, and the rotation is transmitted to the output shaft via the clutch, so that no impact is transmitted to the steering wheel during the transmission. , it is possible to obtain a smooth steering feeling, thereby improving the steering feeling of the electric power steering device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an electric power steering device according to the present invention, and FIG.
3a and 3b are diagrams for explaining the operation of the clutch in the embodiment shown in FIG. 2, FIG. 4 is a diagram showing the slider in FIG. 1, and FIG.
The figure is a characteristic diagram showing the relationship between the steering torque T (elastic deformation of the elastic body) and the supply current I of the electric motor in the embodiment shown in Fig. 2, and Fig. 6 is a longitudinal sectional view showing a modified embodiment of the present invention. It is. 10... Steering wheel, 11,111...
Input shaft, llc, 1llc... corner, lid, 111
d -- Hole, 111e Flange part, 12, 112
...output shaft, 12a...groove, 12b, 112b,...
・Hexagonal part, 112c...flange part, 13,113・
...Torsion bar, 18...Slider, 19...
Ball, 20...Ring, 22,122...Colo,
23.123...Outer sleeve, 23a. 123a... Gear, 24, 124... Electric motor,
25,125... Worm gear, 27... Ball,
28...Lever, 29...Control circuit, 33...Spring, 134...Brush.

Claims (1)

[Claims] A steering torque detector that detects a steering torque applied between an input shaft connected to a steering wheel of a vehicle and an output shaft connected to a steering gear, and a control means responsive to a detection signal from the steering torque detector. an electric motor whose rotation is controlled by a control signal and whose rotation is transmitted to the output shaft; and an electric motor which is interposed between the electric motor and the output shaft and controls intermittently the transmission of the rotation of the electric motor to the output shaft. In the electric power steering device, the steering torque detector detects steering torque according to elastic deformation of an elastic body that connects the input shaft and the output shaft, and the clutch detects steering torque according to elastic deformation of an elastic body that connects the input shaft and the output shaft. The connection and disconnection of the output shaft and the electric motor are controlled by elastic deformation, and the elastic deformation of the elastic body, which controls the connection and disconnection of the clutch, causes the steering torque detector to detect the steering torque and the electric motor to be connected. An electric power steering device characterized in that the elastic deformation is smaller than the elastic deformation of the elastic body when rotation is started.