JP2013010389A - Vehicle steering device - Google Patents

Abstract

The present invention provides a vehicle steering apparatus capable of suppressing variations in distance between a first rotating body and a second rotating body.
An electric power steering apparatus includes a drive pulley 60 supported by an output shaft 19a of a motor 19 so as to be integrally rotatable, a driven pulley 61 for transmitting power to a steered shaft 14, and rotation of the drive pulley 60. A belt 62 for transmitting a force to the driven pulley 61, a ball screw mechanism 21 for converting the rotational force of the driven pulley 61 into a force for moving the steered shaft 14 in the axial direction, and the pulleys 60 and 61 are rotatable. And a housing 16 which supports the inter-core support member 50 and accommodates the pulleys 60 and 61, the belt 62, and the ball screw mechanism 21 therein.
[Selection] Figure 2

Description

  The present invention relates to a vehicle steering apparatus that transmits a driving force generated by a motor to a steering shaft, thereby moving the steering shaft in an axial direction and changing a steering angle of a wheel.

  Conventionally, as this type of vehicle steering device, a so-called rack parallel type electric power steering device has been proposed in which a motor is arranged so that an output shaft is substantially parallel to a rack shaft as a steering shaft (patent). Reference 1). A reduction mechanism provided in the electric power steering apparatus includes a drive pulley (first rotating body) supported so as to be integrally rotatable with an output shaft of a motor, and a driven pulley (second rotation) provided so as to be able to transmit power to the rack shaft. A rotating body) and an endless belt (transmission member) that is hung on both pulleys. Also, a conversion mechanism is provided between the driven pulley and the rack shaft in the power transmission path to convert the rotational force of the driven pulley into a force that moves the rack shaft in the axial direction.

  The electric power steering apparatus includes a housing configured by combining a plurality of divided housings. In the housing, most of the rack shaft, the speed reduction mechanism, and the conversion mechanism are accommodated. Both pulleys constituting the speed reduction mechanism are rotatably supported by different divided housings.

JP 2010-184599 A JP 2005-29145 A

  By the way, the divided housing that supports the drive pulley is different from the divided housing that supports the driven pulley. Therefore, the distance between both pulleys (hereinafter, also referred to as “inter-center distance”) varies due to the assembly error of each divided housing. For example, if the distance between the cores is shorter than the lower limit value of the predetermined design range, the belt tension applied to both pulleys becomes too weak, and the noise generated during driving may increase. On the other hand, if the inter-center distance is longer than the upper limit value of the predetermined design range, the belt tension becomes too strong, and the product life of the belt may be shortened.

  In addition, as a rack parallel type electric power steering device, between the first gear on the motor side (first rotating body) and the second gear on the rack shaft side (second rotating body) in the power transmission path. Moreover, an apparatus provided with an intermediate gear (transmission member) is also known (see Patent Document 2). Even in such an electric power steering device, if the distance between the first and second gears varies, the transmission efficiency of the driving force generated by the motor may be reduced, and the life of each gear may be shortened.

Accordingly, there has been a demand for a technique for suppressing variation in the distance between the cores of the rack parallel type electric power steering apparatus.
The present invention has been made in view of such circumstances. An object of the present invention is to provide a vehicle steering apparatus that can suppress variations in distance between the first rotating body and the second rotating body.

  In order to achieve the above object, the invention according to claim 1 relating to a vehicle steering apparatus is configured to move the steering shaft in the axial direction by transmitting the driving force generated by the motor to the steering shaft, thereby steering the wheel. In the vehicle steering apparatus for changing the angle, a first rotating body supported so as to be integrally rotatable with the output shaft of the motor, a second rotating body for transmitting power to the steering shaft, and the first A transmission member for transmitting the rotational force of the rotating body to the second rotating body, and converting the rotational force of the second rotating body into a force for moving the steering shaft in the axial direction. A conversion mechanism that transmits to the shaft, a rotating body support member that rotatably supports each of the first and second rotating bodies, and the first and second rotating bodies that support the rotating body support member. A housing in which the transmission member and the conversion mechanism are housed; And summarized in that it comprises a.

  According to the said structure, each 1st and 2nd rotary body is each supported by the rotary body support member supported by a housing in the state which can rotate freely. Therefore, although the dispersion | variation in the distance between the 1st and 2nd each rotary body resulting from the processing precision of a rotary body support member arises, the 1st and 2nd resulting from the assembly precision of each component at the time of assembling a steering device. There is almost no variation in the distance between the rotating bodies. Therefore, it is possible to suppress variations in the distance between the first and second rotating bodies as compared with the case where the first and second rotating bodies are supported by separate members.

  According to a second aspect of the present invention, in the vehicle steering apparatus according to the first aspect, the rotating body support member is made of a material having a linear thermal expansion coefficient lower than a linear thermal expansion coefficient of a material constituting the housing. It is a summary.

  Each rotating body constituting the steering apparatus may be disposed in the vicinity of the engine in the engine room of the vehicle. In this case, the housing constituting the steering device receives a large amount of heat generated from the engine and thermally expands. In this regard, in the present invention, the rotating body support member that supports the first and second rotating bodies is less likely to thermally expand than the housing. Therefore, compared with the case where the first and second rotating bodies are supported by the housing, the distance between the first and second rotating bodies is prevented from gradually changing during traveling of the vehicle. be able to.

  According to a third aspect of the present invention, in the vehicle steering apparatus according to the first or second aspect, the transmission member is an endless belt that is hung on the first and second rotating bodies. It is a summary.

  According to the above configuration, since variations in the distance between the first and second rotating bodies are suppressed, variations in the tension of the belts hung on the first and second rotating bodies can be suppressed. As a result, the product life of the belt can be extended and noise generated from the steering device can be reduced.

The schematic diagram explaining one Embodiment of the electric power steering apparatus as a steering apparatus of the vehicle of this invention. Sectional drawing which illustrates typically the principal part of the electric power steering apparatus of this embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. It is assumed that the “left-right direction” in FIGS. 1 and 2 coincides with the “vehicle width direction”.
As shown in FIG. 1, an electric power steering device 11 as a vehicle steering device assists a steering angle transmission mechanism 13 for transmitting rotation of a steering wheel (not shown) to a wheel 12 as a steered wheel, and steering operation. And an assist device 15 that applies force (also referred to as “assist force”) to a turning shaft (also referred to as “rack shaft”) 14 as a steering shaft. The electric power steering apparatus 11 is provided with an aluminum housing 16. In the housing 16, an intermediate portion of the steered shaft 14 and a part of the assist device 15 are accommodated.

  The steering angle transmission mechanism 13 is provided with a steering shaft 17 that rotates together with the steering, and a rack and pinion mechanism 18 that converts the rotation of the steering shaft 17 into a linear motion. When the driving force output from the rack and pinion mechanism 18 is transmitted to the steered shaft 14, the steered shaft 14 moves in the axial direction that is also the width direction of the vehicle.

  The assist device 15 according to the present embodiment is a device that transmits an assist force based on a driving force generated by a motor 19 disposed outside the housing 16 to the steered shaft 14. Such an assist device 15 includes a speed reduction mechanism 20 and a ball screw mechanism 21 as a conversion mechanism, which are arranged in order from the motor 19 in the power transmission path.

Next, the housing 16 will be described with reference to FIGS. 1 and 2.
As shown in FIGS. 1 and 2, the housing 16 includes a first divided housing 30 disposed on the left side and a second divided housing 40 disposed on the right side. Between the divided housings 30 and 40, an inter-core support member 50 as a rotating body support member is disposed. Note that the left end portion 14 </ b> A and the right end portion 14 </ b> B of the steered shaft 14 protrude outside the housing 16.

  The first divided housing 30 is provided with a first main body portion 31 having a cylindrical shape and an enlarged diameter portion 32 disposed on the right side of the first main body portion 31. The inner diameter and outer diameter of the enlarged diameter portion 32 are larger than the inner diameter and outer diameter of the first main body portion 31. An inter-core support member 50 is attached to the first divided housing 30 with a bolt or the like (not shown) so as to close the opening 33 formed at the right end of the enlarged diameter portion 32.

  The second divided housing 40 is provided with a cylindrical second main body portion 41 and a large accommodating portion 42 disposed on the left side of the second main body portion 41. The opening 43 formed at the left end of the large accommodating portion 42 is formed to have a cross-sectional area (that is, an area of a plane orthogonal to the axial direction) larger than the opening 33 of the first divided housing 30. An inter-core support member 50 is attached to the second divided housing 40 with a bolt or the like (not shown) so that the opening 43 is closed.

The inter-core support member 50 is obtained by integrally forming a flat support member main body 51 and a substantially cylindrical tubular portion 52 provided on the right side of the support member main body 51. The inter-core support member 50 of the present embodiment is made of a material (for example, carbon steel such as S45C) that satisfies the following two conditions. And the support member 50 between cores is comprised by performing press work, cutting, etc. with respect to the material which satisfy | filled each following conditions.
(First condition) A material having a lower linear thermal expansion coefficient than the material (aluminum in this embodiment) constituting each of the divided housings 30 and 40.
(Second condition) A material having a specific gravity larger than that of each of the divided housings 30 and 40.

  The support member main body 51 of the inter-core support member 50 is a part for closing the opening 43 formed at the left end of the second divided housing 40. A support portion 53 for supporting the motor 19 is provided in a portion of the support member main body 51 that does not face the opening 33 of the first divided housing 30. The support portion 53 is a portion formed integrally with the support member main body 51 and is formed in an annular shape so as to protrude leftward from the support member main body 51. In the support portion 53, a bearing 54 for rotatably supporting the output shaft 19a of the motor 19 is provided. Thus, the tip (right end in FIG. 2) of the output shaft 19a of the motor 19 supported by the support 53 via the bearing 54 is inserted into the housing 16 through the through hole 55 provided in the support member main body 51. Has been.

Further, an insertion hole 56 through which the steered shaft 14 is inserted is provided in a portion of the support member body 51 that faces the opening 33 of the first divided housing 30.
The cylindrical portion 52 of the inter-core support member 50 is formed so as to surround the steered shaft 14 that is inserted through the insertion hole 56 of the support member main body 51. That is, the inside of the cylindrical portion 52 communicates with the inside of the insertion hole 56, and the center line of the cylindrical portion 52 substantially coincides with the center line S <b> 1 of the steered shaft 14. Further, a portion (upper portion in FIG. 2) facing the tip of the output shaft 19 a of the motor 19 in the proximal end portion (the left end portion in FIG. 2) of the tubular portion 52 is formed inside and outside the tubular portion 52. A communication hole 57 for communication is formed.

  Further, a distal end side portion (a right end side portion in FIG. 2) 52 a of the cylindrical portion 52 is located in a connecting portion 44 located between the second main body portion 41 and the large accommodating portion 42 in the second divided housing 40. positioned. The inner diameter of the connecting portion 44 is slightly larger than the outer diameter of the cylindrical portion 52 of the inter-core support member 50.

Next, the speed reduction mechanism 20 and the ball screw mechanism 21 will be described with reference to FIG.
As shown in FIG. 2, the speed reduction mechanism 20 includes a drive pulley 60 as a first rotating body provided to be rotatable integrally with an output shaft 19 a of the motor 19, and a driving force generated by the motor 19. And a driven pulley 61 as a second rotating body for transmitting to the motor. An endless belt 62 as a transmission member is hung on these pulleys 60 and 61. The belt 62 is inserted through a communication hole 57 provided in the inter-core support member 50.

  Each pulley 60, 61 is made of a material (for example, carbon steel such as S43C) having a lower linear thermal expansion coefficient than the material (aluminum in the present embodiment) that constitutes each divided housing 30, 40. In this embodiment, the linear thermal expansion coefficient of the material constituting each pulley 60, 61 is approximately the same as the linear thermal expansion coefficient of the material constituting the inter-core support member 50. The driven pulley 61 is formed in an annular shape, and its outer diameter is larger than the outer diameter of the driving pulley 60. Such a driven pulley 61 is arranged such that the rotation center thereof substantially coincides with the center line S1 of the steered shaft 14. Specifically, the driven pulley 61 is supported by the ball screw mechanism 21 (specifically, a ball screw nut 70 described later) via an annular support member 63 so as to be integrally rotatable.

  The belt 62 includes a plurality of wires made of a material (for example, carbon steel such as S43C) having a linear thermal expansion coefficient comparable to that of the materials constituting the pulleys 60 and 61. And the belt 62 is comprised so that these each wire may be enclosed with a glass material.

  The ball screw mechanism 21 is disposed between the steered shaft 14 and the driven pulley 61 in the radial direction around the steered shaft 14. Such a ball screw mechanism 21 includes a ring-shaped ball screw nut 70 and a plurality of balls 71 disposed between the ball screw nut 70 and the steered shaft 14 in the radial direction around the steered shaft 14. ing. The ball screw nut 70 is rotatably supported by the cylindrical portion 52 of the inter-core support member 50 via a bearing 72 disposed on the right side of the driven pulley 61. In addition, although illustration is abbreviate | omitted in FIG. 2, internal thread processing is given to a part in the axial direction of the steered shaft 14.

  When the motor 19 is driven, the drive pulley 60 rotates. Then, the rotational force of the drive pulley 60 is transmitted to the driven pulley 61 via the belt 62. Such rotation of the driven pulley 61 is transmitted to the ball screw nut 70, and the ball screw mechanism 21 including the ball screw nut 70 uses the rotational force of the driven pulley 61 to move the steered shaft 14 in the axial direction, that is, Convert to assist power. As a result, the steering device 14 assists the axial movement of the steered shaft 14 based on the steering operation by the driver, whereby the steering angle of the wheel 12 is changed.

As described above, in the present embodiment, the following effects can be obtained.
(1) The pulleys 60 and 61 are supported by the inter-core support member 50 in a rotatable state. Therefore, although the distance between the pulleys 60 and 61 due to the processing accuracy of the inter-core support member 50, that is, the inter-center distance varies, the inter-core distance due to the assembling accuracy of each component when assembling the electric power steering device 11 Almost no variation in distance. Therefore, it is possible to suppress variations in the distance between the cores as compared with the case where the pulleys 60 and 61 are supported by separate members.

  (2) As a result, variations in the tension of the belts 62 hung on the pulleys 60 and 61 are suppressed. Therefore, it is possible to suppress an increase in noise generated during driving due to the tension of the belt 62 being too weak, and the product life of the belt 62 is shortened due to the tension of the belt 62 being too strong. Can be suppressed.

  (3) The electric power steering device 11 may be disposed in the vicinity of the engine (specifically, below the engine) in the engine room of the vehicle. In this case, the housing 16 receives a large amount of heat generated from the engine and thermally expands. In this regard, in the present embodiment, the inter-core support member 50 is less likely to thermally expand than the divided housings 30 and 40. Therefore, compared with the case where each pulley 60 and 61 is supported by at least one of the divided housings 30 and 40, it is possible to suppress a gradual change in the inter-center distance during traveling of the vehicle.

  (4) Since the change in the center distance while the vehicle is running is suppressed, the electric power steering device 11 may not be provided with a mechanism for adjusting the tension of the belt 62. That is, it is possible to contribute to simplification of the electric power steering device 11.

  (5) Each of the divided housings 30 and 40 is made of a material having a specific gravity smaller than the specific gravity of the material constituting the inter-core support member 50. Therefore, an increase in the weight of the entire apparatus due to the provision of the inter-core support member 50 separately from each of the divided housings 30 and 40 can be suppressed.

The embodiment may be changed to another embodiment as described below.
In the embodiment, each of the divided housings 30 and 40 may be made of a material other than aluminum (for example, an aluminum alloy) as long as the material has a specific gravity smaller than that of the material constituting the inter-core support member 50. .

  -In embodiment, if the material which comprises the support member 50 between cores has a linear thermal expansion coefficient smaller than the material which comprises each division | segmentation housings 30 and 40, linear heat will be produced rather than the material which comprises the pulleys 60 and 61. The expansion coefficient may be large. The material constituting the inter-core support member 50 may have a smaller linear thermal expansion coefficient than the material constituting the pulleys 60 and 61.

  -In embodiment, if the material which comprises the support member 50 between cores has a linear thermal expansion coefficient smaller than the material which comprises each division | segmentation housing 30 and 40, specific gravity with the material which comprises each division | segmentation housing 30 and 40 May be the same material. The material constituting the inter-core support member 50 may be a material having a specific gravity smaller than the specific gravity of the material constituting each of the divided housings 30 and 40.

  -In embodiment, you may comprise the support member 50 between cores with the material same as the material which comprises each division | segmentation housing 30 and 40. FIG. Even if comprised in this way, since each pulley 60 and 61 is supported by the same member, the dispersion | variation in the distance between cores can be suppressed.

  In the embodiment, a mechanism for adjusting the tension of the belt 62 may be provided. Even if the pulleys 60 and 61 are supported by the same member, variations in the inter-center distance cannot be completely eliminated. Therefore, by providing the above mechanism, fluctuations in the tension of the belt 62 due to variations in the inter-center distance can be suppressed.

In the embodiment, the cylindrical portion 52 of the inter-core support member 50 may also serve as the outer ring of the bearing 72.
In the embodiment, the speed reduction mechanism is a transmission arranged between the first gear as the first rotating body, the second gear as the second rotating body, and the first and second gears. The structure provided with the intermediate gear as a member may be sufficient. In this case, it is preferable that the intermediate gear is rotatably supported by the inter-core support member 50 that supports the first and second gears. Even in such an electric power steering device, the variation in the distance between the cores can be suppressed, so that it is possible to suppress the transmission efficiency of the driving force generated by the motor 19 from being reduced and the life of each gear from being shortened.

Next, the technical idea that can be grasped from the above embodiment and another embodiment will be added below.
(A) The vehicle steering apparatus, wherein the housing is made of a material having a specific gravity smaller than that of the material constituting the rotating body support member.

According to the said structure, the whole apparatus can be reduced in weight compared with the case where a housing is comprised with the material of specific gravity equal to or more than the specific gravity of the material which comprises a rotary body support member.
(B) The second rotating body has an annular shape, and the steering shaft is inserted through the second rotating body,
The vehicle steering apparatus according to claim 1, wherein the conversion mechanism is disposed between the steering shaft and the second rotating body in a radial direction about the steering shaft.

  DESCRIPTION OF SYMBOLS 11 ... Electric power steering device (vehicle steering device), 12 ... Wheel, 14 ... Steering shaft as steering shaft, 16 ... Housing, 19 ... Motor, 19a ... Output shaft, 21 ... Ball screw mechanism as conversion mechanism, DESCRIPTION OF SYMBOLS 50 ... Center support member as a rotary body support member, 60 ... Drive pulley as a 1st rotary body, 61 ... Driven pulley as a 2nd rotary body, 62 ... Belt as a transmission member

Claims (3)

In a vehicle steering apparatus that transmits a driving force generated by a motor to a steering shaft to move the steering shaft in an axial direction and change a steering angle of a wheel.
A first rotating body that is rotatably supported by the output shaft of the motor;
A second rotating body for transmitting power to the steering shaft;
A transmission member for transmitting the rotational force of the first rotating body to the second rotating body;
A conversion mechanism that converts the rotational force of the second rotating body into a force that moves the steering shaft in the axial direction;
A rotating body support member that rotatably supports each of the first and second rotating bodies;
A vehicle steering apparatus comprising: a housing that supports the rotating body support member and that houses the first and second rotating bodies, the transmission member, and the conversion mechanism.   2. The vehicle steering apparatus according to claim 1, wherein the rotating body support member is made of a material having a linear thermal expansion coefficient lower than that of the material constituting the housing.   3. The vehicle steering apparatus according to claim 1, wherein the transmission member is an endless belt that is hung on the first and second rotating bodies. 4.

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