JPS61220968A - Torque limiting mechanism for power steering - Google Patents

Abstract

PURPOSE:To make a transmission auxiliary member and a final step reduction gear easily separable at the time of trouble happening in a driving source, by inserting a shear pin into an interval between a pin hole installed in the final step reduction gear of a reduction gear mechanism to be combinedly connected to the driving source in a power steering and another pin hole installed in the steering force transmission auxiliary member. CONSTITUTION:At the time of normal steering, when a steering wheel is rotated, a power assist corresponding to detecting output of a torque sensor detecting the torque given to a steering shaft is given to this steering shaft from a motor 21 via a pinion gear 32, a reduction gear 25, a final step reduction gear 26 and a yoke 30 of a universal joint. On the other hand, when a burnout in the motor 21 or an engagement failure in gears, etc., is produced and manual steering force increases, shearing force to be added to a shear pin 28 grows larger. And, when this shearing force becomes more than the specified value, this shear pin 28 is cut off, whereby mechanical transmission between a steering force transmission auxiliary member 27 and the final step reduction gear 26 is intercepted, thus the steering shaft is made rotatable by hand.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a steering cylinder of an automobile. This relates to power steering that applies rotational force to the steering wheel using electric or hydraulic means, and is particularly useful when the torque on the steering wheel side becomes large due to a failure of the electric or hydraulic means for applying rotational force. The present invention relates to a torque limiting mechanism that releases this.

[Prior Art] As a conventional torque limiting mechanism for this type of power steering, there is a technique disclosed in Japanese Patent Laid-Open No. 137255/1983.

FIG. 3 is an overall configuration diagram of a conventional power steering torque limiting mechanism.

A torque limiter 3 that slips at a constant torque is attached to the drive shaft 2 of the motor 1, and a gear 4 rotatably supported on the drive shaft 2 controls the drive shaft 2 only when the torque limiter 3 is in the coupled state. It is designed to transmit rotation. A gear 5 is connected to the gear 4, and a gear 6, which is integrally coaxial with the gear 5, meshes with a gear 8 pivotally supported on a steering shaft 7 to form a speed reduction device. The electromagnetic clutch 9 is attached to the steering shaft 7 and controls power transmission between the gear 8 and the steering shaft 7.

The torque sensor 10 detects the rotation direction and twist angle applied to the steering shaft 7 by the steering wheel 15. The control circuit 11 receives signals from the vehicle speed sensor 12 and the torque sensor 10 to control the motor 1 and the electromagnetic clutch 9.

That is, when the speed detected by the vehicle speed sensor 12 is below a certain speed, the signal from the torque sensor 10 determines whether the motor 1 is turned on or off and the direction of rotation, and the electromagnetic clutch 9 is turned on or off to control the rotation of the gear 8. It comes into contact with and separates from the steering shaft 7. The pinion 13 is fixed to the steering shaft 7, and the rack 14 of the rack bar
It meshes with.

From the viewpoint of imparting power to the steering shaft 7, the motor 1 as the power source and the gears 4,5,6,8 as the reduction mechanism constitute a power auxiliary mechanism.

The conventional power steering torque limiting mechanism having the above structure operates as follows.

When the vehicle speed is below a certain speed, the control circuit 11 operates,
Motor 1 and electromagnetic clutch 9 are turned on. Since the motor 1 has a characteristic that the load torque and the motor rotation speed are inversely proportional, when the steering wheel 15 is rotated, the torque of the motor 1 corresponding to the rotation speed is applied to the steering shaft 7. Become. That is, when the torque is within a range in which the torque limiter 3 does not slip, the gear 4.5
．． 6.8, the power is transmitted to the electromagnetic clutch 9, which is turned on, and the power is applied to the steering shirt l-7, thereby providing power assistance.

When the steering wheel 15 is restored and torque is no longer applied to the steering shaft 7, the torque sensor 1
0, the rotation of the motor 1 is stopped and the electromagnetic clutch 9 is turned off, so that normal manual steering can be restored.

Further, when the vehicle speed exceeds a certain value, the control circuit 11 turns off the motor 1 and the electromagnetic clutch 9, resulting in normal manual steering.

When the steering speed of the steering wheel 15 is very fast and exceeds the maximum motor rotation speed, that is, when the motor 1 becomes a human power load on the steering wheel 15, the torque limiter 3 prevents the motor from sliding at a certain torque or more. Therefore, power assistance is no longer provided to the steering shaft 7. When the torque becomes less than a certain level, the torque limiter 3 is restored to the connected state, and the motor 1 can provide power assistance to the steering shaft 7.

In this way, the torque limiter 3 is activated when the motor 1 seizes up, for example, and the steering wheel 1 is activated.
Manual steering becomes possible by the human power added to 5.

[Problems to be Solved by the Invention] However, since the torque limiter 3 is disposed on the drive shaft 2 of the motor 1, the gear 4.5.6.8 between the torque limiter 3 and the steering shaft 7 The meshing of etc. is bad (
It was not possible to deal with situations such as when the machine became unable to rotate.

Furthermore, even if the torque limiter 3 is activated, the gears 4, 5, 6, 8 for deceleration are
This becomes a burden on the human power required to steer the vehicle, and the manual steering at this time requires a larger amount of human power than a vehicle without a power assist mechanism.

Further, since the torque limiter 3 has a restoring function, its structure is complicated and the unit cost of parts is high.

Furthermore, due to the current strengthening of quality control, failures of this type of power steering power assist mechanism have become extremely rare, and the need for a restorable torque limiter has become obsolete.

Therefore, in order to solve the above-mentioned problems, the present invention aims to
The object of the present invention is to provide a torque limiting mechanism for power steering that allows manual steering by separating the auxiliary mechanism from the steering shaft.

[Means for Solving the Problems] A power steering torque limiting mechanism according to the present invention includes a torque sensor that detects torque applied to a steering shaft, a drive source that applies rotational force to the steering shaft, A power steering system comprising a control circuit that controls a drive source according to the output of the torque sensor includes a transmission auxiliary member that rotates integrally with the steering shaft, a deceleration mechanism that decelerates the rotation of the drive source, and a deceleration mechanism. It consists of a pin insertion hole drilled in the final stage reduction gear corresponding to the output gear, a pin insertion hole drilled in the transmission auxiliary member, and a shear pin press-fitted between both pin insertion holes.

[Function] In the present invention, the transmission auxiliary member 27 that is fixed to the steering shaft and rotates, and the final reduction gear 26 that corresponds to the output gear that constitutes the reduction mechanism that decelerates the rotation of the motor 1 as the drive source, respectively. Pin insertion holes 26a and 27a
A pin insertion hole 26 is drilled in the final stage reduction gear 26.
a, the pin insertion hole 27a drilled in the transmission auxiliary member, and the shear pin 28 press-fitted between both pin insertion holes, so there was an increase in load equivalent to the shear stress of the shear pin 28. At this time, the shear pin 28 can cut off the energy transmission between the two.

Normally, when the steering wheel 60 is rotated, a torque sensor detects the torque applied to the steering shaft, and the motor 21, the pinion gear 22, the reduction gear 25, and the final reduction gear provide power assistance according to the detected output. The gear 26 can be attached to the steering shaft via the yoke 30 of the universal joint. However, if the drive source motor 21 is burnt out or the gears are malmeshed, the load required to rotate the steering wheel 60 increases, and the increase in load acts to stop the final reduction gear 26. Therefore, when the shearing force applied to the shearing pin 28 increases and exceeds the shearing stress of the shearing pin 28, the shearing pin 28 breaks and mechanical transmission between the transmission auxiliary member 27 and the final reduction gear 26 is interrupted. Therefore, since the steering wheel can separate the speed reduction mechanism from its load, even if an abnormality occurs in the drive source or speed reduction mechanism, the steering wheel can be steered with the same rotational force as in manual steering.

[Embodiment] FIG. 1 is a sectional view of a main part showing an embodiment of a torque limiting mechanism for power steering according to the present invention.

A pinion gear 22 is attached to the rotating shaft of the motor 21. A case of the motor 21 is fixed to an upper housing 23. The binion gear 22 meshes with a reduction gear 25 that is pivotally supported between a bearing 41 of the upper housing 23 and a bearing 42 of the lower housing 24.

The reduction gear 25 meshes with a final reduction gear 26 that is fitted into a yoke 30 of a universal joint that is pivotally supported between a bearing 43 of the upper housing 23 and a bearing 44 of the outer housing 24.

A transmission auxiliary member 27 is fixed to the yoke 30 of the universal joint by a key 29, and the auxiliary member 27 and the final reduction gear 26 are connected by a pin 28.

The shear pin 28 is inserted into the pin insertion hole 2 of the transmission auxiliary member 27.
7a and the pin insertion hole 26a of the final stage reduction gear 26. Yoke 301 of the universal joint
．． : The fitted final stage reduction gear 26 is fixed to the spacer 51, the transmission auxiliary member 27 fixed to the yoke 30 is fixed to the yoke 30 by the snap ring 52, and the spacer 53 is used to stop the yoke 30 from moving in the axial direction. and the lower housing 24 is restricted in the axial direction.

Inside the yoke 30 of the universal joint,
The transmission shaft to which the steering gearbox binion gear is attached is joined by the serrations. and,
Steering cylinder cylinder 1 to which the steering wheel 60 is attached via the remaining universal joint components such as the joint ball, centerpiece, and yoke connected to the coupling hole 30a of the yoke 30 of the universal joint! The other end of the foot (not shown) is connected to the other end of the foot (not shown). A dustproof seal member 54 is attached to the yoke 30 of the universal joint where the tip of the transmission shaft is located.

Note that the snap ring 55 is used for mounting the bearing 43, and the snap ring 56 is used for mounting the bearing 41. Further, the seal member 57 is for dustproofing the bearing 41 side. Dust cover 58 protects the bearing 43 from dust.

The power steering torque limiting mechanism of this embodiment configured as described above can operate as follows.

When the steering wheel 60 is rotated, the control circuit rotates the motor 21 according to the rotation direction and torque obtained by the torque sensor, and the rotational force is transmitted to the pinion gear 22, reduction gear 25, and final reduction gear 26. . The rotational force transmitted to the final stage reduction gear 26 is transmitted via the shear pin 28 to the transmission auxiliary member 27 fixed to the yoke 30 of the universal joint.

Therefore, normally, when the steering wheel 60 is rotated, the torque sensor detects the torque applied to the steering shaft, and provides power assistance to the motor 21, pinion gear 22, reduction gear 2, etc. according to the detected output.
5. It can be attached to the steering shaft via the final stage reduction gear 26 and the yoke 30 of the universal joint.

However, if the motor 21 burns out or the gears become misaligned, the load required to rotate the steering wheel 60 increases. Since the increase in load acts to stop the final reduction gear 26, the shear pin 28
When the shearing force applied to becomes large and exceeds the shearing stress of the shearing pin 28, the shearing pin 28 breaks and mechanical transmission between the transmission auxiliary member 27 and the final reduction gear 26 is cut off.

Therefore, even if the load on the steering wheel 60 increases due to poor meshing of the motor 21 or gears, the rotational force is transmitted between the transmission auxiliary member 27 and the final reduction gear 26 due to the cutting of the shear pin 28, and the transmission force is cut off. The steering wheel 6 after cutting the shear pin 28
A load of 0 can be used with a load similar to that of a normal manual steering operation.

In the first embodiment described above, the yoke 30 of the universal joint and the transmission auxiliary member 27 were connected in order to reduce the number of parts between the steering shaft and the steering gear box, but when implementing the present invention, However, this configuration is not necessarily required. For example, the second
It can be configured as shown in the main part sectional view of the power steering torque limiting mechanism of the present invention shown in the figure.

In the figure, the final stage reduction gear 126 is integrally formed with a protrusion 126b protruding in the axial direction, and the transmission auxiliary member 12
7 is fitted. The steering shaft 100 extends through the axial center of the transmission auxiliary member 127, and the steering shaft 100 and the transmission auxiliary member 127 are fixed to each other so as to be able to transmit rotational force to each other. The final stage reduction gear 126 has a pin insertion hole 126a, and the transmission auxiliary member 127 has a pin insertion hole 127a. The pin insertion hole 126a has a diameter large enough to press the shear pin 28 into it, and the pin insertion hole 127a is an elliptical hole extending in the axial direction, and its short diameter is large enough to press the shear pin 28 into it. The long diameter is about 1.5 to 2 times the diameter of the shear pin 28. That is, the structure is such that when the shear pin 28 breaks, it is easy to take out the broken shear pin 28.

Therefore, in this case as well, if a force greater than the shear stress of the shear pin 28 is applied between the transmission auxiliary member 127 and the final reduction gear 126, the shear pin 28 will break and the rotational force between them will be cut off.

As described above, the power steering torque limiting mechanism of the present invention includes the transmission auxiliary member 27 or 127 that is fixed to the steering cylinder 1 shift and rotates, the pinion gear 22 that decelerates the rotation of the motor 1, and the reduction gear. The shear pin 28 is provided between the shear pin 28 and the final reduction gear 26 or the final reduction gear 126 corresponding to the output gear constituting the motor rotation speed reduction mechanism consisting of the shear pin 25 and the final reduction gear 26. When there is an increase in load equivalent to the shear stress of , the energy transfer between the two can be cut off. Therefore, since the steering wheel can separate the speed reduction mechanism from its load, the same rotational force as in manual wheel steering can be used for steering.

When a torque exceeding a predetermined value is applied between the power assisting mechanism of the power steering and the steering shaft,
A with only Sharpin 28! Since the structure is simple and the unit cost of parts is low.

Particularly, as is now the case, when quality control of power steering components has become more advanced and their failures have become extremely rare, it is possible to maintain safety using only the seat 11 and pin 28. Effective.

[Effects of the Invention] As described above, the present invention provides a transmission auxiliary member that rotates integrally with the steering shaft, a speed reduction mechanism that decelerates the rotation of the drive source, and a final stage corresponding to the output gear that constitutes the speed reduction mechanism. Since the shear pin is press-fitted between the pin insertion hole drilled in the reduction gear and the pin insertion hole drilled in the transmission auxiliary member, when there is an increase in load equivalent to the shear stress of the shear pin. , it is possible to cut off the energy transmission between the two using a shear pin. therefore,
Since the drive source and deceleration mechanism can be cut off from the load on the steering wheel rotated by human power, even if an abnormality occurs in the drive source or deceleration mechanism, the vehicle can be steered with the same rotational force as with manual steering. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing one embodiment of a power steering torque limiting mechanism of the present invention, and FIG. 2 is a sectional view of a main part showing another embodiment of a power steering torque limiting mechanism of the present invention. FIG. 3 is an overall configuration diagram showing the entire conventional power steering torque limiting mechanism. In the figure, 10... Torque sensor, 11... Control circuit, 1.21... Motor, 28... Shear pin, 100... Steering shaft, 26. 126... Final stage reduction gear, 27 .127...Transmission auxiliary member, 26a, 27a, 126a, 127a...Pin insertion hole. In addition, in the figures, the same reference numerals and the same symbols indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A torque sensor that detects torque applied to a steering shaft, a drive source that applies rotational force to the steering shaft, and a control circuit that controls the drive source according to the output of the torque sensor. In power steering, there is a transmission auxiliary member that rotates together with the steering shaft, a reduction mechanism that decelerates the rotation of the drive source, and a pin drilled in the final reduction gear that corresponds to the output gear that makes up the reduction mechanism. A torque limiting mechanism for power steering, comprising an insertion hole, a pin insertion hole drilled in a transmission auxiliary member, and a shear pin press-fitted between both pin insertion holes.