JP2008001158A - Center take-off type steering device - Google Patents

Abstract

A center take-off type steering device that absorbs a twisting force from a steered bar side in a stable and reliable manner and does not directly transmit the twisting force to a rack bar.
In a center take-off type steering apparatus, a connecting member (16) for engaging a rack bar (14) and a steered bar (18) together with the rack bar (14) in the axial direction of the rack bar (14) in an opening (24) of the rack housing (22). It is slidable. The bar case 32 of the connecting member 16 is rotatable with respect to the rack bar 14 and allows the steered bar 18 to rotate relatively around the axis of the rack bar 14. As a result, even if a twisting force is generated in the steered bar 18, the twisting force can be canceled by the relative rotational operation of the steered bar 18 and the rack bar 14. And it is prevented that a twisting force is transmitted to the rack bar 14, and generation | occurrence | production of abnormal noise and a meshing failure in a rack and pinion mechanism can be suppressed.
[Selection] Figure 2

Description

  The present invention relates to a center take-off type steering device, and in particular, even when a turning force is generated on a steered bar due to tire side bounce / rebound, the turning force is canceled so that the operation of the rack and pinion mechanism is not affected. The present invention relates to an improvement of a center take-off type steering device that can be used.

  In general, the operation of the steering wheel by the driver is transmitted to the rack bar via the steering shaft and the rack and pinion mechanism. By moving the rack bar in the left-right direction of the vehicle, the wheels can be steered via steered bars (for example, tie rods) connected to both ends of the rack bar. As another steering device, there is a center take-off type steering device. In this center take-off type steering apparatus, a steered bar (sometimes called a tie rod or a rack end) is offset by a predetermined distance in parallel to the rack bar. By disposing the steered bar at a position offset from the rack bar, the length of the steered bar can be made longer than when the steered bar is connected to both ends of the rack bar. When the steered bar is long, for example, it is possible to reduce a change in toe angle that occurs when the tire bounces / rebounds, compared to when the steered bar is short, which is advantageous in terms of suspension characteristics.

However, since the steered bar is offset with respect to the rack bar, the steered bar is displaced in the vehicle vertical direction when the tire bounces / rebounds, and a rotational moment is generated with respect to the rack bar. That is, the steered bar is in a state of applying a twisting force to the rack bar. When the twisting force is transmitted to the rack bar, the meshing state of the rack gear and the pinion gear changes, which may cause abnormal noise and may reduce the durability of the rack and pinion mechanism. Therefore, for example, in the center take-off type power steering device of Patent Document 1, a guide shoe including a member for connecting a tie rod and a rack bar is formed of a wear-resistant resin material. A rotational moment is absorbed by pressure-deforming the guide shoe.
Japanese Patent Application No. 2000-62628

  However, in the case of a conventional configuration that relies on deformation of the resin member, there is a limit to the ability to absorb the rotational moment, and a sufficient effect may not be obtained. Further, since the resin member is repeatedly deformed each time a twisting force is input from the tie rod, there is a problem that durability of the resin member is lowered. Furthermore, since the resin member functions as a guide shoe, there is also a problem that the pressure contact state changes each time the slider slides, and the stability of absorbing the twisting force tends to vary.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a center take-off type steering device that absorbs a twisting force from the steered bar side stably and reliably and does not directly transmit the twisting force to the rack bar. It is to provide.

  In order to solve the above-mentioned problems, the present invention is directed to the rack housing through the opening formed at the substantially center of the rack housing with each inner end of the steered bar connected to the pair of left and right knuckle arms. In a center take-off type steering device connected to a rack bar included so as to be slidable in the axial direction, the rack bar and the steered bar are engaged with each other, and the opening is in the axial direction of the rack bar. A slidable connecting member is provided together with the rack bar, and the connecting member is configured to relatively rotate the steered bar around the axis of the rack bar.

  According to this aspect, since the steered bar rotates relative to the rack bar, for example, even when the tire is bound / rebounded and a turning force (rotational moment) is generated in the steered bar, the steered bar is steered. The twisting force can be canceled by the relative rotation of the bar and the rack bar. As a result, it is possible to prevent the twisting force from being transmitted to the rack bar, and to suppress the generation of abnormal noise. Further, the load on the rack bar in the rotational direction is eliminated, and the load on the rack bar and the pinion gear can be reduced. Further, wear of the gear portion can be reduced. Furthermore, since an extra load burden is not applied to the rack bar or its gear portion, the strength and support rigidity of the gear portion can be lowered. As a result, the gear portion of the rack and pinion mechanism can be reduced in size, and the overall center take-off type steering apparatus can be reduced in size.

  In the above aspect, the connecting member includes a bar case that is rotatably provided around an axis of the rack bar, and a bracket that supports the steered bar and is fixed to the bar case. May be. Since the bar case is rotatably provided around the rack bar, the relative rotation of the steered bar with respect to the rack bar can be performed smoothly and stably with a simple configuration. Further, since the bar case is only provided around the rack bar so as to be rotatable, a large rotation range can be secured. As a result, the load load in the rotation direction on the rack bar can be canceled reliably.

  Moreover, the said aspect WHEREIN: The said bar case may interpose a low friction member in the connection surface with the said rack bar. As the low friction member, for example, a thin metal plate having high wear resistance can be used. Further, it is preferable to improve the sliding property by coating the surface of the metal thin plate with a fluororesin or the like. According to this aspect, the relative rotation of the steered bar with respect to the rack bar becomes smoother, and the ability to absorb the twisting force is improved.

  Further, in the above configuration, the connecting member may be restricted from moving in the axial direction of the rack bar by a fixing member fixed to the rack bar. The fixing member can have any shape as long as the connecting member does not hinder the relative rotation between the steered bar and the rack bar. For example, it may be a ring-shaped member that is retrofitted to the shaft portion of the rack bar, or may be a protrusion that projects from the surface of the rack bar. According to this aspect, only the relative rotational motion of the steered bar and the rack bar is allowed, and the twisting force input from the steered bar side is absorbed. On the other hand, the reciprocating motion of the rack bar can be smoothly transmitted to the steered bar.

  According to the center take-off type steering apparatus of the present invention, since the steered bar rotates relative to the rack bar, it is possible to prevent the twisting force generated on the steered bar side from being transmitted to the rack bar.

  Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

  In the center take-off type steering apparatus of the present embodiment, the connecting member that engages the rack bar and the steered bar is slidable together with the rack bar in the axial direction of the rack bar at the opening of the rack housing. The connecting member allows the steered bar to relatively rotate about the axis of the rack bar. As a result, for example, even when the tire bounces / rebounds and a twisting force is generated in the steered bar, the twisting force can be canceled by the relative rotational operation of the steered bar and the rack bar. And it is prevented that a twisting force is transmitted to a rack bar, and the generation | occurrence | production of abnormal noise and a meshing defect in a rack and pinion mechanism can be suppressed.

  FIG. 1 is an external conceptual diagram illustrating the configuration of a center take-off type steering apparatus 10 according to the present embodiment. The center take-off type steering device 10 includes an input shaft 12, a rack bar 14, a connecting member 16, and a steered bar 18. The input shaft 12 transmits a rotational motion force based on a driver's turning operation input via a steering wheel (not shown). The tip of the input shaft 12 is connected to the output shaft. A pinion gear is formed at the tip of the output shaft, and meshes with a rack gear formed at one end of the rack bar 14 in the gear box 20. Therefore, the rack bar 14 linearly moves in the vehicle width direction according to the rotational momentum of the input shaft 12. A steering assist force from a motor (not shown) is input to the output shaft to realize a power steering device.

  In the case of a right-hand drive vehicle, for example, in the case of a right-hand drive vehicle, the rack bar 14 is loosely inserted in a cylindrical rack housing 22 formed on the left side of the gear box 20 so as to be slidable in the axial direction. An opening 24 having a predetermined length and an axial length is formed in a part of the circumference of the substantially central portion of the rack housing 22. On the other hand, a connecting member 16 is connected to a substantially central portion of the rack bar 14 and is exposed to the side surface of the rack housing 22 through the opening 24. The connecting member 16 includes a bracket 26, and each inner end of the steered bar 18 connected to a pair of left and right knuckle arms is connected to a connection hole 28 formed in the bracket 26. That is, the steered bar 18 is connected with a predetermined amount offset from the rack bar 14. In the case of FIG. 1, a state in which only one of the steered bars 18 is connected is shown in the connection hole 28 of the bracket 26, and the steered bar extending in the reverse direction is not shown.

  The opening 24 of the rack housing 22 has an opening length that allows at least the sliding of the connecting member 16 corresponding to the maximum turning amount of the steering wheel. Therefore, the rack bar 14 slides in the rack housing 22 according to the rotation amount of the input shaft 12. Accordingly, the connecting member 16 moves together with the rack bar 14, and the steered bar 18 engaged with the connecting member 16 is moved in the sliding direction of the rack bar 14. As a result, steering can be performed according to the amount of rotation of the steering wheel. Since the connecting member 16 functions as a slider with respect to the rack housing 22 as described above, a plate-like guide shoe 30 is interposed at a sliding portion with the opening 24. The guide shoe 30 is sandwiched between a bracket 26 and a bar case 32 connected to the rack bar 14 and fixed by a bolt inserted into the bolt hole 34. Although not shown in FIG. 1, a dust boot that covers at least the opening 24 in order to prevent foreign matter or the like from entering the rack housing 22 from the opening 24 to the outer periphery of the rack housing 22. Is covered in the axial direction (see FIG. 2). The dust boot has, for example, a bellows shape, and allows the connecting member 16 to slide in the axial direction of the rack bar 14.

  The center take-off type steering device 10 configured as described above is fixed to the vehicle body by a fastening member such as a bolt inserted into a fixing hole portion 38 of a fixing stay 36 formed in the gear box 20, for example.

  FIG. 2 is a detailed cross-sectional view centering on the connecting member 16 which is a main part of the present embodiment. In the case of the normal center take-off type steering apparatus 10, the connecting member 16 that connects the rack bar 14 and the steered bar 18 is fixed to the rack bar 14. That is, the rack bar 14 and the steered bar 18 are substantially integrated. As a result, when the steering bar 18 is displaced in the vertical direction of the vehicle, such as when the suspension is bound / rebounded, a rotational moment is generated, and the twisting force is directly transmitted to the rack bar 14. If the twisting force is transmitted to the rack bar 14, the meshing state of the rack gear of the rack bar 14 and the pinion gear on the output shaft side changes, which may cause abnormal noise during meshing and inhibit smooth meshing operation. Or the durability of the rack gear and pinion gear may be reduced. Therefore, in the present embodiment, the connection of the connecting member 16 to the rack bar 14 is made rotatable so that the twisting force generated on the steered bar 18 side is not transmitted to the rack bar 14 side.

  As shown in FIG. 2, the connecting member 16 includes a bracket 26 to which the steered bar 18 is connected, and a bar case 32 that engages with the rack bar 14. The bar case 32 can be formed into a cylindrical shape with, for example, a hard metal material, and is rotatably provided around the columnar rack bar 14. Although the bar case 32 and the rack bar 14 may be in direct contact with each other, in order to smoothly rotate the bar case 32 with respect to the rack bar 14, a low friction member is provided on the connection surface between the bar case 32 and the rack bar 14. As an alternative, the bush 40 may be interposed. The bush 40 can be an annular member formed of a thin metal plate, for example. The bush 40 can smoothly rotate the bar case 32 with respect to the rack bar 14 only by being interposed in the connection surface between the bar case 32 and the rack bar 14, but in the case of FIG. Is sandwiched between the bar case 32 and the snap ring 42. By sandwiching the bush 40 in this manner, the bar case 32 can be smoothly rotated with respect to the snap ring 42, and the bar case 32 can be rotated with respect to the rack bar 14 more smoothly. . Further, by coating the surface of the metal thin plate constituting the bush 40 with a fluororesin or the like, the slidability can be easily improved. A bearing can also be used as the low friction member.

  The bar case 32 configured in this manner is rotatable with respect to the rack bar 14, while transmitting a linear motion based on the rotation of the output shaft to the steered bar 18 in the axial direction of the rack bar 14. In order to achieve this, movement in the axial direction needs to be restricted. Therefore, in the present embodiment, fixing members fixed to the rack bar 14 are used at both ends of the bush 40. For example, a snap ring 42 can be used as the fixing member. When the snap ring 42 is used, it may be attached to both ends of the bar case 32, or one side may be used as a fixed protrusion and the snap ring 42 may be attached to the other.

  As described with reference to FIG. 1, the connecting member 16 is configured to move in the axial direction along the opening 24 formed in the rack housing 22. In the case of the present embodiment, the guide shoe 30 formed of a material such as a resin having good slidability is opened so that the connecting member 16 can be smoothly slid along the opening 24 formed in a substantially long hole shape. It is attached to the bar case 32 so as to contact the portion 24. The guide shoe 30 is clamped and fixed between the bar case 32 and the bracket 26 by a bolt 46 together with the dust boot 44. Therefore, the bar case 32 is rotatable with respect to the rack bar 14, but the movement in the rotational direction is restricted to some extent by the opening 24 of the rack housing 22.

  A ball joint 48 is provided at each inner end of the steered bar 18 connected to the pair of left and right knuckle arms, and the steered bar 18 is connected to the bracket 26 via the ball joint 48. The ball joint 48 allows the operation of the steering bar 18 in a direction parallel to the paper surface of FIG. 2, the movement of the connecting member 16 accompanying the movement of the rack bar 14 in the axial direction, and the axial direction of the steering bar 18. It is configured so that it can be moved smoothly. A joint boot 50 is mounted around the ball joint 48 to prevent malfunction of the ball joint 48 due to foreign matter.

  The operation of the center take-off type steering apparatus 10 configured as described above will be described.

  First, the basic operation of the center take-off type steering device 10 will be described. When the driver steers the steering wheel, the input shaft 12 rotates to rotate the pinion gear at the tip of the output shaft. As the pinion gear rotates, the rack gear meshing with it operates to move the rack bar 14 in the axial direction, that is, in the vehicle width direction. Since the rack bar 14 is connected to the connecting member 16 that is restricted from moving in the axial direction, the axial movement of the rack bar 14 is directly transmitted to the pair of steered bars 18 engaged with the connecting member 16. The When the steered bar 18 moves to the right or left of the vehicle, the knuckle arm operates and the wheels are steered in the steering direction of the steering wheel.

  Next, the operation of the center take-off type steering device 10 when an external force in the vertical direction of the vehicle is input to the steered bar 18 due to the wheels bouncing / rebounding will be described.

  When the wheels bounce / rebound, the steering bar 18 receives an external force that moves in the vehicle vertical direction via the knuckle arm. As described above, in the center take-off type steering apparatus 10, the steered bar 18 is offset from the axis of the rack bar 14 so that the steered bar 18 receives an external force in the vertical direction. On the other hand, a rotational moment is generated. Here, a part of the connecting member 16 that engages with the steered bar 18 is in contact with the opening 24 of the rack housing 22 via the guide shoe 30. Therefore, the rotational moment due to the vertical displacement on the side of the steered bar 18 is such that the rack housing 22 functions as a receiving member and can receive a part of the rotational moment, that is, the rotational force. However, since the connecting member 16 is slidably disposed with respect to the opening 24 of the rack housing 22, there is a gap between the connecting member 16 and the opening 24. Therefore, a part of the rotational moment due to the vertical displacement on the steered bar 18 side remains. That is, it remains as a squeezing force that squeezes the rack bar 14. However, in the present embodiment, the bar case 32 constituting the connecting member 16 has a structure that is rotatable with respect to the rack bar 14. In other words, since the steered bar 18 is structured to be relatively rotatable about the axis of the rack bar 14, the rotational moment due to the vertical displacement on the steered bar 18 side is transmitted to the rack bar 14. It is prevented.

  Thus, by configuring the steered bar 18 so as to be relatively rotatable about the axis of the rack bar 14, the load load in the rotational direction on the rack bar 14 of the center take-off type steering device 10 is eliminated, and the rack The load on the bar and pinion gears can be reduced. Further, wear of the gear portion can be reduced. Furthermore, the strength and support rigidity of the gear portion can be reduced. As a result, the entire gear portion can be reduced in size. Further, since no twisting force acts between the rack bar 14 and the pinion gear, the generation of abnormal noise can be suppressed.

  The configuration of the center take-off type steering device 10 shown in the present embodiment is an example, and if the steering bar 18 can be relatively rotated around the axis of the rack bar 14 by the operation of the connecting member 16, the structure is appropriately configured. It can be changed, and the same effect as this embodiment can be obtained. For example, in the description of FIG. 2, the bar case 32 is rotatably provided around the rack bar 14, but the other part of the connecting member 16 is a movable structure, and the steered bar 18 is attached to the rack bar 14. It may be configured to be able to rotate relative to the axis so as to prevent the twisting force from being transmitted to the rack bar 14.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The configuration shown in each figure is for explaining an example, and any configuration that can achieve the same function can be changed as appropriate, and the same effect can be obtained.

It is an external appearance conceptual diagram explaining the composition of the center take-off type steering device concerning this embodiment. It is a detailed sectional view centering on a connecting member of the center take-off type steering apparatus according to the present embodiment.

Explanation of symbols

  10 center take-off type steering device, 12 input shaft, 14 rack bar, 16 connecting member, 18 steered bar, 20 gear box, 22 rack housing, 24 opening, 26 bracket, 28 connection hole, 30 guide shoe, 32 bar Case, 34 bolt hole, 36 fixed stay, 38 fixed hole, 40 bush, 42 snap ring, 44 dust boot, 46 bolt, 48 ball joint, 50 joint boot.

Claims (4)

A rack bar including inner ends of each of the steered bars respectively connected to the pair of left and right knuckle arms so as to be slidable in the axial direction with respect to the rack housing through an opening formed substantially at the center of the rack housing; In the connected center take-off type steering device,
The rack bar and the steered bar are engaged with each other, and a connecting member that is slidable together with the rack bar in the axial direction of the rack bar at the opening is provided, and the connecting member includes the steered bar as described above. A center take-off type steering device configured to be relatively rotatable about an axis of a rack bar.   The connecting member includes a bar case that is rotatably provided around an axis of the rack bar, and a bracket that supports the steered bar and is fixed to the bar case. The center take-off type steering apparatus according to claim 1, wherein   The center take-off type steering device according to claim 2, wherein the bar case has a low friction member interposed on a connection surface with the rack bar.   The center take-off type according to any one of claims 1 to 3, wherein the connecting member is restricted from moving in the axial direction of the rack bar by a fixing member fixed to the rack bar. Steering device.

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