JP5131449B2 - Rack stroke end impact mitigation device - Google Patents

Description

  The present invention relates to an impact mitigation device for a rack stroke end in a rack mechanism of a vehicle rack and pinion type steering device.

As a steering apparatus for an automobile, there is a rack and pinion type steering apparatus that converts a rotational movement from a steering wheel into an axial movement of a rack shaft by a rack and pinion mechanism.
In this rack and pinion type steering device, an elastic body is interposed between a ball joint fixed to the end of the rack shaft and a rack housing with which the ball joint abuts, thereby providing a rack shaft. There is provided an impact mitigation device that absorbs an impact at the stroke end (see, for example, Patent Documents 1 and 2).
JP 2006-1510 A JP 2005-88777 A

By the way, as the size of the vehicle increases, the output of the assist device that assists the input at the steering wheel also increases, so the load and impact on the rack stroke end in the rack and pinion type steering device tends to increase. is there. For this reason, it is necessary to increase the strength at the rack stroke end, but this increases the size of the rack mechanism.
In recent years, many assist devices equipped with an electric power steering device are used in the column, but in this assist device, the output is maximized when the tire turning angle is maximized, A large load continues to be applied to the connecting portion of the shaft that connects the column and the rack and pinion portion, and there is a possibility that deterioration or breakage may occur at an early stage.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rack stroke end impact mitigation device capable of further enhancing the impact absorption capability without causing an increase in size.

  In order to achieve the above object, a rack stroke end impact mitigation device of the present invention is supported such that a rack shaft can reciprocate within a rack housing, and an end of the rack housing and an end of the rack shaft are A stroke end impact mitigation device in a rack mechanism that is brought into contact with each other to restrict movement of the rack shaft, and a rack end to which a tie rod is connected via a ball joint is provided at an end of the rack shaft. A rack cushioning member and a housing cushioning member made of an elastic material are provided at the end of the rack shaft and the end of the rack housing that protrude from the end of the rack housing and come into contact with each other, and project from the rack housing. When the rack end reaches a predetermined position in the protruding direction, the rack cushioning member is It said housing cushioning member with slidably close contact with the inner peripheral surface of Ujingu is characterized in that slidably contact the outer peripheral surface of the rack end.

With this configuration, when the rack end reaches a predetermined position in the protruding direction, the rack cushioning member is slidably adhered to the inner peripheral surface of the rack housing and the housing cushioning member slides on the outer peripheral surface of the rack end. Since it closely adheres, a compression space surrounded by the rack cushioning member, the housing cushioning member, the rack housing and the rack end is formed at the rack stroke end, and a good cushioning effect can be obtained by the compressive force of air in this compression space. it can.
Thereafter, when the rack cushioning member and the housing cushioning member come into contact with each other, an impact force from the rack shaft can be absorbed by the rack cushioning member and the housing cushioning member made of an elastic material.
In this way, excellent shock absorption capability can be obtained. For example, even if a column-type electric power steering device with the maximum output when the tire turning angle is maximized is installed, the column and rack・ It is possible to reduce the load on the connecting part of the shaft connecting the and pinion part and to extend the service life.

  In this case, it may have an accommodation space for accommodating air between the rack cushioning member and the housing cushioning member that are compressed when the rack cushioning member and the housing cushioning member are close to each other.

  With such a configuration, the air in the compression space surrounded by the rack cushioning member, the housing cushioning member, the rack housing and the rack end can be accommodated in the accommodating space, and without disturbing the smooth movement of the rack shaft, Good shock absorbing ability can be exhibited.

  Further, it may have a flow path for guiding the air between the rack cushioning member and the housing cushioning member which are compressed when the rack cushioning member and the housing cushioning member come close to each other.

  With such a configuration, air in the compression space can be appropriately released, generation of excessive repulsive force at the rack stroke end can be suppressed, and a smooth stroke operation can be obtained while absorbing impact well.

  According to the impact mitigation device at the rack stroke end of the present invention, it is possible to further increase the impact absorbing capacity without causing an increase in size.

Hereinafter, an impact mitigation device at a rack stroke end according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a rack stroke end impact mitigating device according to an embodiment of the present invention. 1B corresponds to the BB cross section of FIG. 1A, and FIG. 1C corresponds to the CC cross section of FIG. 1A.
As shown in FIG. 1A, in a rack-and-pinion type steering apparatus, a rack shaft 2 on which a rack 1 is formed is meshed with a pinion (not shown) and is placed in a cylindrical rack housing 3. The shock mitigation device is configured at the rack stroke ends at both ends (only one end is shown in FIG. 1 (A)) of the rack mechanism configured as described above. Yes.

At the rack stroke end constituting the impact mitigating device, a rod-shaped rack end 4 is fixed to the end of the rack shaft 2, and this rack end 4 is inserted from an insertion hole 5 a formed in the end surface 5 of the rack housing 3. It is protruding.
The rack housing 3 has a large inner diameter portion 3a on the center side, a small inner diameter portion 3b near the end, and a tapered inner diameter portion 3c between the large inner diameter portion 3a and the small inner diameter portion 3b. The small inner diameter portion 3b has a smaller diameter than the large inner diameter portion 3a, and the tapered inner diameter portion 3c gradually narrows from the large inner diameter portion 3a toward the small inner diameter portion 3b. If these diameters are D3a, D3b, and D3c, respectively, it can be expressed as D3a>D3c> D3b.

  The end of the rack end 4 is provided with a socket 6 constituting a ball joint, and a tie rod ball (not shown) is slidably held in the socket 6. The rack end 4 has a large outer diameter portion 4a, a small outer diameter portion 4b, and a tapered outer diameter portion 4c between the large outer diameter portion 4a and the small outer diameter portion 4b. The large outer diameter portion 4a is arranged to be inserted through the insertion hole 5a on the connection side with the rack shaft 2, and the small outer diameter portion 4b is arranged closer to the socket 6 than the large outer diameter portion 4a. The diameter is smaller than the diameter portion 4a. Further, the tapered outer diameter portion 4c gradually narrows from the large outer diameter portion 4a toward the small outer diameter portion 4b. If these diameters (outer diameters) are D4a, D4b, and D4c, respectively, it can be expressed as D4a> D4c> D4b.

  An annular rack cushioning member 11 made of an elastic material such as rubber is attached to the rack end 4 at the end on the rack shaft 2 side of the large outer diameter portion 4a. Has an outer diameter (D11) smaller than the small inner diameter portion 3b of the rack housing 3, and is disposed in contact with the end surface 2a of the rack shaft 2. A groove 11a is formed on the outer periphery of the rack cushioning member 11 along the circumferential direction. An annular O-ring 12 made of an elastic material such as rubber is attached to the groove 11a. ing. The O-ring 12 protrudes from the buffer member 11, and the outer diameter dimension (D12) of the O-ring 12 is smaller than the large inner diameter portion 3a of the rack housing 3 and larger than the small inner diameter portion 3b. It is said that. That is, D3b> D11, D11 <D12, D3b <D12 <D3a.

  An annular housing cushioning member 13 made of, for example, an elastic material such as rubber is attached to the rack housing 3 on the end surface 5 side of the small inner diameter portion 3b. It has an inner diameter (D13) larger than that of the large outer diameter portion 4a and is disposed in contact with the end face 5. A groove 13a is formed on the inner periphery of the housing cushioning member 13 along the circumferential direction. An annular O-ring 14 made of an elastic material such as rubber is attached to the groove 13a. Has been. The O-ring 14 protrudes inward from the buffer member 13, and the inner diameter dimension (D 14) of the O-ring 14 is smaller than the large outer diameter portion 4 a of the rack end 4 and smaller than the small outer diameter portion 4 b. The diameter is also large. That is, D13> D4a, D13> D14, and D4b <D14 <D4a.

Next, the impact mitigating function of the rack stroke end impact mitigating device will be described with reference to FIG.
A steering wheel (not shown) is rotated, and the rotational motion is converted into the axial motion of the rack shaft 2 by the rack and pinion mechanism. When the rack shaft 2 is moved to one side, the rack stroke end on the moving side is converted. Then, as shown in FIG. 2A, the rack end 4 protrudes from the insertion hole 5 a of the end surface 5 of the rack housing 3.

Accordingly, the O-ring 12 attached to the rack cushioning member 11 reaches the small inner diameter portion 3b from the large inner diameter portion 3a of the rack housing 3 beyond the tapered inner diameter portion 3c, and reaches the inner peripheral surface of the small inner diameter portion 3b. Adheres slidably. Further, with respect to the O-ring 14 attached to the housing cushioning member 13, the rack end 4 has a tapered outer diameter portion 4c passing from a small outer diameter portion 4b thereof, and a large outer diameter portion 4a is disposed. The O-ring 14 is slidably adhered to the outer peripheral surface of the portion 4a.
As a result, a compression space S surrounded by the rack buffer member 11, the housing buffer member 13, the small inner diameter portion 3 b of the rack housing 3 and the large outer diameter portion 4 a of the rack end 4 is formed at the rack stroke end.

Further, when the rack shaft 2 is slid, as shown in FIG. 2B, the compression space S gradually narrows, and accordingly, the rack shaft 2 is compressed by the air pressure compressed in the compression space S. A pressing force toward the direction opposite to the moving direction is gradually generated.
Thereafter, as shown in FIG. 2C, the air (compressed air) in the compressed space S is between the outer periphery of the rack buffer member 11 and the inner peripheral surface of the small inner diameter portion 3b of the rack housing 3 and the housing buffer member. 13 is accommodated in a gap G formed between the inner periphery of the rack end 4 and the large outer diameter portion 4a of the rack end 4, and the rack cushioning member 11 and the housing cushioning member 13 made of an elastic material are brought into contact with each other and elastically deformed. By doing so, the impact force from the rack shaft 2 is absorbed.

  Thus, according to the impact mitigation device at the rack stroke end according to the above embodiment, the rack cushioning member 11 slides on the inner peripheral surface of the rack housing 3 when the rack end 4 reaches a predetermined position in the protruding direction. Since the housing shock-absorbing member 13 is slidably in close contact with the outer peripheral surface of the rack end 4, the compression space S surrounded by the rack shock-absorbing member 11, the housing shock-absorbing member 13, the rack housing 3, and the rack end 4 is formed. A good cushioning effect can be obtained by the compression force of the air in the compression space S formed at the rack stroke end.

  Thereafter, when the rack cushioning member 11 and the housing cushioning member 13 come into contact with each other, an impact force from the rack shaft 2 can be absorbed by the rack cushioning member 11 and the housing cushioning member 13 made of an elastic material. Thereby, it is possible to further increase the shock absorbing capacity without causing an increase in size.

Thus, since the above-mentioned impact mitigation device can obtain an excellent shock absorption capability, for example, a column-type electric power steering device that has the maximum output when the tire turning angle is maximized is mounted. Even so, it is possible to reduce the load on the connecting portion of the shaft connecting the column and the rack and pinion portion, thereby extending the life.
Further, the air in the compression space S surrounded by the rack buffer member 11, the housing buffer member 13, the rack housing 3, and the rack end 4 flows between the rack buffer member 11 and the rack housing 3 and between the housing buffer member 13 and the rack end. Since it is accommodated in the accommodation space formed by the gap G between the rack 4 and the rack shaft 2, it is possible to exhibit a good shock absorbing ability without hindering the smooth movement of the rack shaft 2.

  In the above embodiment, the grooves 11a and 13a are formed on the outer periphery of the rack buffer member 11 and the inner periphery of the housing buffer member 13, and the O-rings 12 and 14 are attached to these grooves 11a and 13a. As shown in the figure, instead of the O-rings 12 and 14, on the outer periphery of the rack buffer member 11, on the protrusion (protrusion) 11 b that can be in close contact with the small inner diameter portion 3 b of the rack housing 3, and on the inner periphery of the housing buffer member 13. The protrusions (convex portions) 13b that can be in close contact with the large outer diameter portion 4a of the rack end 4 may be integrally formed. Also in this case, the outer diameter (D11b) of the ridge 11b is set to satisfy D3b <D11b <D3a. Further, the inner diameter (D13b) of the ridge 13b is set to satisfy D4b <D13b <D4a.

  And according to this structure, it becomes unnecessary to mount | wear with the O-rings 12 and 14 separately, and it can aim at reduction of the cost by reduction of a number of parts and omission of mounting work.

Further, in this case, as shown in FIG. 4, a communication groove (flow path) 21 communicating in the axial direction may be formed on the outer periphery of the protrusion 11 b of the rack cushioning member 11. For example, a notch (concave portion) may be provided as a communication groove (flow path) 21 on a part of the outer periphery of the ridge 11b. Air (or a part thereof) compressed in the compression space S can escape to the rack shaft 2 side through the communication groove 21.
Further, as shown in FIG. 5, the rack buffer member 11 itself is formed with a communication hole (flow path) 22 communicating in the axial direction, and the air (or a part thereof) compressed in the compression space S is You may make it escape to the rack axis | shaft 2 side via these communication grooves 21 or the communication hole 22. FIG.

By forming the communication groove 21 or the communication hole 22 in this manner, the air in the compression space S is appropriately released to the outside, the generation of excessive repulsive force at the rack stroke end is suppressed, and the shock is absorbed well. Smooth stroke operation can be obtained.
In particular, by using the impact reducing device at the rack stroke end described above for a rack and pinion type steering device, the load on the connecting portion of the shaft connecting the column and the rack and pinion portion is reduced, Long life can be achieved.

5 is provided with a pressure adjusting portion such as a valve structure in the communication hole 22 of the apparatus shown in FIG. 5, and the flow of fluid is reversed during reverse steering (steering in the direction of expanding the volume of the compression space S) as compared to during steering in the compression direction. The road passage resistance may be reduced so as not to cause a steering resistance force.
For example, during the reduction operation of the space S (steering toward the left or right stroke end of the steering wheel), the inner diameter becomes small, and the exhaust is performed to an extent that suppresses excessive repulsion at the rack stroke end. When the steering wheel is steered in the center direction, a control valve may be provided in the communication hole 22 to reduce the steering resistance by increasing the inner diameter and smoothly performing intake. According to such a configuration, a smooth stroke operation can be performed even during the expansion operation of the space S (during intake).
Note that the above countermeasures for intake may be applied to the device shown in FIG. 1, FIG. 3, or FIG. For example, a communication hole (flow channel) 22 is provided in the rack cushioning member 11 of the apparatus shown in FIG. 1, FIG. 3, or FIG. 4, and a simple valve that performs intake but not exhaustion is provided in the communication hole 22. Thus, the intake may be performed smoothly.
Thus, the present invention is not limited to the above-described embodiment, and can be variously modified.

It is sectional drawing of the impact mitigation apparatus of the rack stroke end which concerns on embodiment of this invention. It is operation | movement sectional drawing explaining a motion of an impact mitigation apparatus. It is sectional drawing which shows the modification of an impact relaxation apparatus. It is sectional drawing which shows the other modification of an impact relaxation apparatus. It is sectional drawing which shows the other modification of an impact relaxation apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Rack shaft, 3 ... Rack housing, 4 ... Rack end, 11 ... Rack buffer member, 13 ... Housing buffer member, 21 ... Communication groove (flow path), 22 ... Communication hole (flow path), G ... Gap (accommodation) space).

Claims (3)

A rack stroke end in a rack mechanism in which a rack shaft is supported so as to be reciprocally movable in the rack housing, and the end of the rack housing and the end of the rack shaft are in contact with each other to restrict the movement of the rack shaft. Shock absorber of
A rack end to which a tie rod is connected via a ball joint is provided at an end of the rack shaft and protrudes from an end of the rack housing,
A rack cushioning member and a housing cushioning member made of an elastic material are respectively provided at the end of the rack shaft and the end of the rack housing that are in contact with each other,
When the rack end protruding from the rack housing reaches a predetermined position in the protruding direction, the rack buffer member is slidably adhered to the inner peripheral surface of the rack housing, and the housing buffer member is mounted on the rack end. An impact mitigation device at the rack stroke end, which is slidably adhered to the outer peripheral surface of the rack stroke end.   2. The rack stroke according to claim 1, further comprising: an accommodating space that accommodates air between the rack cushioning member and the housing cushioning member that are compressed when the rack cushioning member and the housing cushioning member are close to each other. End impact mitigation device.   3. A flow path for guiding the air between the rack cushioning member and the housing cushioning member, which are compressed by the proximity of the rack cushioning member and the housing cushioning member, to the outside. The shock mitigation device at the rack stroke end described in 1.

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