Patent Document

RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/JP2006/322321, filed Nov. 1, 2006, which is based on Japanese Patent Application No. 2005-320364, the entire contents of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a rack and pinion type steering device for a vehicle and a method of manufacturing the steering device. 
     BACKGROUND ART 
     The rack and pinion type steering device for the vehicle is so designed as to transmit the rotation of a pinion to a rack that is meshed with the pinion to move a tie rod that is fitted to an end portion of the rack, and transmit the rotation to a steering unit that controls the direction of the tire wheels. 
     The rack and pinion type steering device of this type includes a rack guide that presses the back surface of a rack shaft in a meshing direction by the aid of an elastic body such as a spring so that the pinion and the rack are appropriately meshed with each other. 
     Also, the rack guide is of a slide type in which the rack shaft and the rack guide are brought in slide contact with each other, and of a rolling type in which the rack shaft is supported by a roller. The rolling type is so configured as to bear a pin that supports the roller by a pin insertion groove that is defined in a rack guide holder (refer to Japanese Laid Open Patent Publication No. 2004-034829). 
       FIG. 5  is a cross-sectional view for explaining an example of the configuration of a rack and pinion type steering device  100  having the above conventional rolling type rack guide,  FIG. 6(   a ) is a partially cross-sectional view taken along a line A-A,  FIG. 6(   b ) is a cross-sectional view taken along a line B-B of  FIG. 5  from which a housing is omitted. 
     A rack and pinion type steering device  100  is so configured as to arrange a pinion shaft  104  and a rack shaft  105  in the interior of a housing  101 . The pinion shaft  104  is rotationally supported by a ball bearing  102  and a needle bearing  103 . The rack shaft  105  is so arranged as to be movable in the axial direction by the aid of a rack bush not shown. An end of the rack shaft  105  is coupled with a tie rod having a link unit that changes the direction of the tire wheels through a ball joint. A rack tooth  105   a  of the rack shaft  105  is meshed with a pinion tooth  104   a  of the pinion that is integrally formed with the above pinion shaft  104 . 
     Further, a rack guide  106  is disposed at an opposite side of the pinion shaft  104  with respect to the rack shaft  105  in the interior of the housing  101 . The rack guide  106  is so configured as to press the rack shaft  105  from the back surface to appropriately maintain a meshing state of the pinion tooth  104   a  with the rack tooth  105   a.    
     The rack guide  106  is made up of a rack guide holder  107  that is totally formed in a substantially cylindrical shape, a pin  108  that is arranged in a pin support hole  107   a  which is defined in an inner space of the rack guide holder  107  in a direction orthogonal to the axial direction of the rack shaft  105 , and a roller  110  having a needle bearing  108  pressed into a center portion thereof and having an outer peripheral surface formed in a hand drum shape. 
     The roller  110  is installed on the pin  108  and rotationally disposed in the inner space of the rack guide holder  107 . The outer peripheral surface of the hand drum shape of the roller  110  is brought in rolling contact with the back surface of the rack shaft  105  (a surface at an opposite side of the meshed surface) so as to press the rack shaft  105  toward the meshed surface. 
     The housing  101  is equipped with a rack guide portion  111  having a cylindrical aperture that guides the rack guide holder  107 , and the outer peripheral surface of the rack guide holder  107  is fitted with the rack guide portion  111 . Also, a screw is formed in the inner surface of the rack guide portion  111  on a lower side (on an opposite side of the rack shaft  105 ) of the rack guide portion  111  of the housing  101 , so as to be meshed with an adjustment screw  112 . 
     The adjustment screw  112  is formed of a cylindrical member having a bottom. The adjustment screw  112  is so configured as to be meshed with the rack guide portion  111 , and press the rack guide holder  107  toward the rack shaft  105  through a disc spring  113  interposed between the adjustment screw  112  and the rack guide holder  107 . The screwing amount of the adjustment screw  112  is so adjusted as to appropriately adjust the meshing state of the rack tooth  105   a  with the pinion tooth  104   a . The rack guide holder  107  can be displaced by the amount of elastic deformation of the disc spring  113 . 
     The conventional rack guide described with reference to  FIGS. 5 ,  6 ( a ), and  6 ( b ) suffers from the problems described below. That is,  FIG. 7  is a diagram for explaining the cross-sectional configuration of the outer peripheral surface of the hand drum shape of the conventional roller  110 . In the conventional rack guide, as shown in  FIG. 7 , the cross-sectional configuration of the hand drum shaped outer peripheral surface of the roller  110  is made up of curved surfaces R 1  and R 2  (R 1  can be equal to R 2 ) consisting of two circular arcs having the radius of curvature larger than the radius of curvature RR of the outer peripheral surface of the rack shaft  105 . Therefore, the hand drum shaped outer peripheral surface of the roller  110  and the outer peripheral surface of the rack shaft  105  are brought in point contact with each other at two points A and B. 
     The reason is that the radius of curvatures R 1  and R 2  of the outer peripheral surface of the roller  110  and the radius of curvature RR of the outer peripheral surface of the rack shaft  105  cannot be manufactured in the entirely identical radius of curvature because of the tolerance (permissible error) in the manufacture. 
     However, when the roller  110  and the rack shaft  105  are brought in point contact with each other as described above, because an area of the contact portion is very small, an estrangement force that occurs when the pinion and the rack are meshed with each other is transmitted to the rack guide holder  107 . Then, the contact portion of the roller  110  with the rack shaft  105  becomes high surface pressure, and the contact portion is liable to be worn. 
     As the countermeasure against the wear of the contact portion, it is general to increase the hardness of the contact portion, and in the above structure, there is proposed that the rack shaft is made of high carbon steel, and the roller is made of high carbon chromium bearing steel, and the rack shaft and the roller are subjected to a heat treatment to increase the hardness. 
     However, even if the hardness of the roller and the rack shaft is increased, the contact portion is high surface pressure without any change, and the wear cannot be completely suppressed. Also, the roller is deformed in the heat treatment, and the fluctuation of the roller becomes large with respect to the rotation center. When the vibration exists in the roller, the amount of elastic deformation of the disc spring (refer to  FIG. 5 ) changes by the fluctuation amount due to the phase (rotational angle position) of the roller. As a result, since the movable amount of the rack guide changes, the fluctuation of the roller must be prevented as much as possible. For that reason, after the roller has been subjected to the heat treatment, the outer surface of the roller is ground so as to eliminate the fluctuation. However, the costs increase because the grinding process is conducted. 
     As described above, even if the hardness of the roller and the rack shaft is increased, the wear of the contact portion cannot be completely eliminated although the costs increase. As a result, there occur disadvantages such as an increase in the amount of elastic deformation of the disc spring or an increase in the movable amount of the rack guide. 
     Also, in the rack and pinion type steering device, when the rack guide movable amount increases, gear rattle (rattle noise) occurs. For that reason, an increase in the excessive rack guide movable amount must be avoided. 
     An object of the present invention is to solve the above disadvantages, that is, to suppress the wear of the contact portion of the roller with the rack shaft, eliminate an increase in the excessive rack guide movable amount, and prevent the rattle noise from occurring. 
     DISCLOSURE OF THE INVENTION 
     According to the present invention, there is provided a rack and pinion type steering device having a rack guide that includes a rack guide holder which is disposed to be movable toward a meshing direction of a rack and a pinion, and has a pin insertion groove formed in an interior thereof, and a roller which is rotatably installed on a pin which is disposed in the pin insertion groove of the rack guide holder, wherein an outer peripheral surface of the roller is formed around a rotating axis in a hand drum shape, and the outer peripheral surface of the hand drum shape has a configuration that comes in line contact with the outer peripheral surface on an opposite side of the meshed surface of the rack shaft and the pinion. 
     Then, the cross-sectional configuration of the hand drum shaped outer peripheral surface of the roller has a curvature identical with the curvature of the cross-sectional configuration of the outer peripheral surface on an opposite side of the meshed surface of the rack shaft with the pinion. 
     Also, according to the present invention, there is provided a method of manufacturing a rack and pinion type steering device having a rolling type rack guide which includes a rack guide holder that presses a back surface of a rack shaft toward a meshed surface of a rack and a pinion by the aid of a roller, and a roller having a hand drum shaped outer peripheral surface which is rotatably installed on a pin which is disposed in a pin insertion groove of the rack guide holder, wherein after the hand drum shaped outer peripheral surface of the roller is formed in a cross-sectional configuration of a curvature different from the curvature of the cross-sectional configuration of the outer peripheral surface on an opposite side of the meshed surface of the rack shaft with the pinion, the rack shaft is pressed toward the formed hand drum shaped outer peripheral surface to reciprocate the rack shaft in the axial direction so as to be plastically deformed while the roller rotates, and the hand drum shaped outer peripheral surface of the roller is formed in a configuration that comes in line contact with the outer peripheral surface on the opposite side of the meshed surface of the rack shaft. 
     In this case, it is possible that after the roller is formed in the hand drum shaped outer peripheral surface of a cross-sectional configuration having a curvature larger than the curvature of the cross-sectional configuration of the outer peripheral surface on an opposite side of the meshed surface of the rack shaft with the pinion, a surface hardening treatment is conducted, and the hand drum shaped outer peripheral surface is then plastically deformed into a configuration that comes in line contact with the outer peripheral surface on the opposite side of the meshed surface of the rack shaft. 
     In this case, it is possible that after the roller is formed in the hand drum shaped outer peripheral surface of a cross-sectional configuration having a curvature smaller than the curvature of the cross-sectional configuration of the outer peripheral surface on an opposite side of the meshed surface of the rack shaft with the pinion, a surface hardening treatment is conducted, and the hand drum shaped outer peripheral surface is then plastically deformed into a configuration that comes in line contact with the outer peripheral surface on the opposite side of the meshed surface of the rack shaft. 
     Also, it is possible that the plastic deformation of the hand drum shaped outer peripheral surface of the roller is conducted by pressing the rack guide toward the rack shaft. 
     Further, it is possible that the plastic deformation of the hand drum shaped outer peripheral surface of the roller is conducted by pressing the rack shaft toward the rack guide by applying a load to an end of the rack shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view for explaining the configuration of a rack and pinion type steering device having a rack guide of a rolling type according to a first embodiment of the present invention. 
         FIG. 2  is a diagram showing a cross-sectional configuration of the outer peripheral surface of a roller that is plastically deformed. 
         FIG. 3  is a diagram for explaining a cross-sectional configuration of the outer peripheral surface of the roller which has not yet been plastically deformed according to a second embodiment. 
         FIG. 4  is a diagram for explaining a method of plastically deforming the outer peripheral surface of the roller according to a third embodiment. 
         FIG. 5  is a cross-sectional view for explaining an example of the configuration of a conventional rack and pinion type steering device having a rack guide of a rolling type. 
         FIG. 6(   a ) is a cross-sectional view taken along a line A-A of  FIG. 5 . 
         FIG. 6(   b ) is across-sectional view taken along a line B-B of  FIG. 5 . 
         FIG. 7  is a diagram for explaining the cross-sectional configuration of the outer peripheral surface of the roller in the conventional art, and the cross-sectional configuration of the outer peripheral surface of the roller which has not yet been plastically deformed according to the first embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Here under, the preferred embodiments of the present invention will be described. 
     First Embodiment 
       FIG. 1  is a cross-sectional view for explaining the configuration of a rack and pinion type steering device  10  having a rack guide of a rolling type according to a first embodiment of the present invention. 
     The rack and pinion type steering device  10  is so configured as to arrange a pinion shaft  14  and a rack shaft  15  in the interior of a housing  11 . The pinion shaft  14  is rotationally supported by a ball bearing  12  and a needle bearing  13 . The rack shaft  15  is so arranged as to be movable in the axial direction by the aid of a rack bush not shown. An end of the rack shaft  15  is coupled with a tie rod having a link unit that changes the direction of the tire wheels through a ball joint not shown. A rack tooth  15   a  of the rack shaft  15  is meshed with a pinion tooth  14   a  of the pinion that is integrally formed with the above pinion shaft  14 . 
     Further, a rack guide  16  is disposed at an opposite side of the pinion shaft  14  with respect to the rack shaft  15  in the interior of the housing  11 . The rack guide  16  is so configured as to press the rack shaft  15  from the back surface to appropriately maintain a meshing state of the pinion tooth  14   a  with the rack tooth  15   a.    
     The rack guide  16  is made up of a rack guide holder  21  that is totally formed in a substantially cylindrical shape, a pin  22  that is arranged in a pin support hole  21   a  which is defined in an inner space of the rack guide holder  21  in a direction orthogonal to the axial direction of the rack shaft  15 , and a roller  24  having a needle bearing  23  pressed into a center portion thereof and having an outer peripheral surface formed in a hand drum shape. 
     The roller  24  is installed on the pin  22  and rotationally disposed in the inner space of the rack guide holder  21 . The outer peripheral surface of the hand drum shape of the roller  24  is brought in rolling contact with the back surface of the rack shaft  15  (a surface at an opposite side of the meshed surface) so as to press the rack shaft  15  toward the meshed surface. 
     The housing  11  is equipped with a rack guide portion  11   a  having a cylindrical aperture that guides the rack guide holder  21 , and the outer peripheral surface of the rack guide holder  21  is fitted with the rack guide portion  11   a . Also, a screw is formed in the inner surface of the rack guide portion  11   a  on a lower side (on an opposite side of the rack shaft  15 ) of the rack guide portion  11   a  of the housing  11 , so as to be meshed with an adjustment screw  25 . 
     The adjustment screw  25  is formed of a cylindrical member having a bottom. The adjustment screw  25  is so configured as to be meshed with the rack guide portion  11   a , and press the rack guide holder  21  toward the rack shaft  15  through a disc spring  26  interposed between the adjustment screw  25  and the rack guide holder  21 . The screwing amount of the adjustment screw  25  is so adjusted as to appropriately adjust the meshing state of the rack tooth  15   a  with the pinion tooth  14   a . The rack guide holder  21  can be displaced by the amount of the elastic deformation of the disc spring  26 . 
     A description will be given of the configuration of the outer peripheral surface of the roller  24  and a method of forming the outer peripheral portion. The cross-sectional configuration of the outer peripheral surface of the roller  24  is identical with the cross-sectional configuration of the outer peripheral surface of the roller  110  in the conventional art described with reference to  FIG. 7  in advance. That is, the cross-sectional configuration of the outer peripheral surface of the roller  24  is made up of curved surfaces consisting of two circular arcs having the radius of curvatures R 1  and R 2  (R 1  can be equal to R 2 ) which are larger than the radius of curvature RR of the cross-sectional configuration of the outer peripheral surface of the rack shaft  15 . 
     A description will be given of a method of forming the outer peripheral surface of the roller  24 . First, the configuration of the outer peripheral surface of the roller  24  is formed into an outer peripheral surface having the above cross-sectional configuration, that is, a cross-sectional configuration that consists of two circulate arcs. The outer peripheral surface is surface hardened by known appropriate means. 
     Subsequently, the pinion shaft  14 , the rack shaft  15 , and the rack guide holder  21  are assembled in the interior of the housing  11 , and the adjustment screw  25  is fastened more than usual to supply an excessive load more than that originally supplied to the rack guide holder  21 . 
     The rack shaft  15  is reciprocated in the axial direction under a state where the excessive load more than that originally supplied is supplied to the rack guide holder  21 , thereby plastically deforming the outer peripheral surface of the roller  24  into the configuration of the outer peripheral surface of the rack shaft  15  so as to follow the outer peripheral surface of the rack shaft. The plastic deformation makes the cross-sectional configurations (radii R 1  and R 2 ) of the outer peripheral surface of the roller  24  coincide with the cross-sectional configuration (radius RR) of the outer peripheral surface of the rack shaft (R 1 =R 2 =RR) As a result, the outer peripheral surface of the roller  24  comes in line contact with the outer peripheral surface of the rack shaft with a high precision. 
       FIG. 2  is a diagram showing the cross-sectional configuration of the outer peripheral surface of the roller  24  that has been plastically deformed. The outer peripheral surface of the roller  24  and the outer peripheral surface of the rack shaft  15  come in line contact with each other in areas of portions C and D. A portion E is a groove that is defined in the roller  24  in advance. 
     The face hardening treatment of the outer peripheral surface of the above roller  24  is conducted by a method such as a known carburization quenching or a nitriding treatment. In this situation, it is desirable that the thickness of the hardened layer is about 0.1 to 0.6 mm, and it is undesirable that the hardened layer is too thick because plastic deformation is difficult. 
     According to the above configuration, the outer peripheral surface of the roller and the outer peripheral surface of the rack shaft come in line contact with each other, and the contact area increases, thereby making it possible to decrease the contact surface pressure. As a result, it is possible to suppress the wear of the contact surface, prevent an increase in the excessive rack guide movable amount, and prevent rattle noise from occurring. 
     Second Embodiment 
     A second embodiment is similar in the configuration to the rack and pinion type steering device  10  having the rack guide of the rolling type according to the first embodiment, and only the configuration of the outer peripheral surface of the roller  24  is different from that in the first embodiment. Accordingly, the configuration of the rack and pinion type steering device having the rack guide is omitted from the detailed description with  FIG. 1  and its description, and only differences will be described. 
       FIG. 3  is a diagram for explaining a cross-sectional configuration of the outer peripheral surface of the roller which has not yet been plastically deformed according to a second embodiment. In the second embodiment, the cross-sectional configuration of the outer peripheral surface of the roller  24  is formed into a curved surface having a radius of curvature R 1  smaller than the radius of curvature RR which is the cross-sectional configuration of the outer peripheral surface of the rack shaft  15 . For that reason, the outer ring of the roller  24  and the outer peripheral surface of the rack shaft  15  come in contact with each other at only points A and B. 
     In the second embodiment, the configuration of the outer peripheral surface of the roller  24  is formed into the cross-sectional configuration shown in  FIG. 3 , and the outer peripheral surface is face-hardened by known appropriate means. 
     Then, the pinion shaft  14 , the rack shaft  15 , and the rack guide holder  21  are assembled in the interior of the housing  11 , and the adjustment screw  13  is fastened more than usual to supply an excessive load more than that originally supplied to the rack guide holder  21 . 
     The rack shaft  15  is reciprocated in the axial direction under a state where the excessive load more than that originally supplied is supplied to the rack guide holder  21 , thereby plastically deforming the outer peripheral surface of the roller  24  into the configuration of the outer peripheral surface of the rack shaft  15  so as to follow the outer peripheral surface of the rack shaft. The plastic deformation makes the cross-sectional configurations (radius R 1 ) of the outer peripheral surface of the roller  24  coincide with the cross-sectional configuration (radius RR) of the outer peripheral surface of the rack shaft (R 1 =RR) As a result, the outer peripheral surface of the roller  24  comes in line contact with the outer peripheral surface of the rack shaft with a high precision. 
     Similarly, in the second embodiment, the cross-sectional configuration (radius R 1 ) of the outer peripheral surface of the roller  24  that has been plastically deformed is shown in  FIG. 2 . The outer peripheral surface of the roller  24  and the outer peripheral surface of the rack shaft  15  come in line contact with each other in areas of portions C and D. A portion E is a groove that is defined in the roller  24  in advance. 
     The surface hardening treatment of the outer peripheral surface of the above roller  24  is conducted by a method such as a known carburization quenching or a nitriding treatment as in the first embodiment. It is desirable that the thickness of the hardened layer is about 0.1 to 0.6 mm, and it is undesirable that the hardened layer is too thick because plastic deformation is difficult. 
     Similarly, in the second embodiment, the contact area of the outer peripheral surface of the roller with the outer peripheral surface of the rack shaft increases, thereby making it possible to reduce the contact surface pressure. As a result, it is possible to suppress the wear of the contact surface, prevent an increase in the excessive rack guide movable amount, and prevent rattle noise from occurring. 
     Third Embodiment 
     A third embodiment is similar in the configuration to the rack and pinion type steering device  10  having the rack guide of the rolling type according to the first embodiment, and only a method of plastically deforming the configuration of the outer peripheral surface of the roller  24  is different from the methods of the first and second embodiments. Accordingly, the configuration of the rack and pinion type steering device having the rack guide is omitted from the detailed description with the first embodiment shown in  FIG. 1 , and only differences will be described. 
     The cross-sectional configuration of the outer peripheral surface of the roller  24  which has not yet been plastically deformed according to the third embodiment is identical with the conventional cross-sectional configuration shown in  FIG. 7 , and also identical with the configuration of the outer peripheral surface which has not yet been plastically deformed according to the first embodiment. That is, the cross-sectional configuration of the outer peripheral surface of the roller  11  is formed of a curved surface consisting of two circular arcs with curved surfaces R 1  and R 2  (R 1  can be equal to R 2 ) having the radius of curvatures larger than the radius of curvature RR which is the cross-sectional configuration of the outer peripheral surface of the rack shaft  15 . For that reason, the outer ring of the roller  24  and the outer peripheral surface of the rack shaft  15  come in contact with each other at only points A and B. 
     In the third embodiment, the configuration of the outer peripheral surface of the roller  24  is first formed into the cross-sectional configuration shown in  FIG. 7 , and the outer peripheral surface is surface hardened by known appropriate means. 
     Then, as shown in  FIG. 4 , a load F is applied to the end of the rack shaft  15  to press the rack shaft  15  toward the roller  24  within the rack guide holder  21 . Since  FIG. 1  shows a state in which the rack shaft  15  is disposed perpendicularly to the paper surface, the end of the rack shaft  15  is disposed on a front side from the paper surface. 
     In  FIG. 4 , a load is applied to a ball joint  31  that is a coupling portion of the end of the rack shaft  15  with the tie rod  30 . Alternatively, the load F can be applied directly to the end of rack shaft  15 . The significant matter resides in that the rack shaft  15  is pressed toward the roller  25  within the rack guide holder  21 . 
     The rack shaft  15  is reciprocated in the axial direction under a state where the excessive load more than that originally supplied is supplied to the rack guide holder  21 , thereby plastically deforming the outer peripheral surface of the roller  24  into the configuration of the outer peripheral surface of the rack shaft  15  so as to follow the outer peripheral surface of the rack shaft. The plastic deformation makes the cross-sectional configurations (radii R 1  and R 2 ) of the outer peripheral surface of the roller  24  coincide with the cross-sectional configuration (radius RR) of the outer peripheral surface of the rack shaft (R 1 =R 2 =RR). As a result, the outer peripheral surface of the roller  24  comes in line contact with the outer peripheral surface of the rack shaft with a high precision. 
     Similarly, in the third embodiment, the cross-sectional configuration (radius R 1 ) of the outer peripheral surface of the roller  24  that has been plastically deformed is shown in  FIG. 2 . The outer peripheral surface of the roller  24  and the outer peripheral surface of the rack shaft  15  come in line contact with each other in areas of portions C and D. A portion E is a groove that is defined in the roller  24  in advance. 
     The surface hardening treatment of the outer peripheral surface of the above roller  24  is conducted by a method such as a known carburization quenching or a nitriding treatment as in the first and second embodiments. It is desirable that the thickness of the hardened layer is about 0.1 to 0.6 mm, and it is undesirable that the hardened layer is too thick because plastic deformation is difficult. 
     In the above third embodiment, the cross-sectional configuration of the outer peripheral surface of the roller  24  which has not yet been plastically deformed is described as the conventional cross-sectional configuration shown in  FIG. 7 , and the cross-sectional configuration of the roller  24  according to the first embodiment which has not yet been plastically deformed shown in  FIG. 7 . Alternatively, the cross-sectional configuration can be formed in the cross-sectional configuration of the roller  24  according to the second embodiment shown in  FIG. 3  which has not yet been plastically deformed. 
     Similarly, in the third embodiment, the contact area of the outer peripheral surface of the roller with the outer peripheral surface of the rack shaft increases, thereby making it possible to reduce the contact surface pressure. As a result, it is possible to suppress the wear of the contact surface, prevent an increase in the excessive rack guide movable amount, and prevent rattle noise from occurring. 
     As has been described above, according to the rack and pinion type steering device of the present invention, the outer peripheral surface of the roller that is rotatably installed on the rack guide is formed around the rotating axis in the hand drum configuration. The outer peripheral surface of the hand drum shape has a configuration that comes in line contact with the outer peripheral surface on the opposite side of the meshed surface of the rack surface with the pinion. More specifically, the cross-sectional configuration of the hand drum shaped outer peripheral surface of the roller is formed with a curvature identical with the curvature of the cross-sectional configuration of the outer peripheral surface on the opposite side of the meshed surface of the rack shaft with the pinion. 
     With the above configuration, the contact area of the outer peripheral surface of the roller with the outer peripheral surface of the rack shaft increases, thereby making it possible to reduce the contact surface pressure. As a result, it is possible to suppress the wear of the contact surface, prevent an increase in the excessive rack guide movable amount, and prevent rattle from occurring. 
     Also, according to the method of manufacturing the rack and pinion type steering device of the present invention, after the roller that is rotatably installed on the rack guide is formed with the hand drum shaped outer peripheral surface having a curvature different from the curvature of the outer peripheral surface on an opposite side of the meshed surface of the rack shaft with the pinion, the rack shaft is reciprocated in the axial direction and plastically deformed while the rack shaft is pressed toward the hand drum shaped outer peripheral surface, and the hand drum shaped outer peripheral surface of the roller is formed in the configuration that comes in line contact with the outer peripheral surface of the rack shaft. 
     In the outer peripheral surface of the roller that has been manufactured by the manufacturing method, the hand drum shaped outer peripheral surface of the roller and the outer peripheral surface of the rack shaft come in line contact with each other with a high precision. With the above configuration, the contact area of the outer peripheral surface of the roller with the outer peripheral surface of the rack shaft increases, thereby making it possible to reduce the contact surface pressure. As a result, it is possible to suppress the wear of the contact surface, prevent an increase in the excessive rack guide movable amount, and prevent rattle from occurring. 
     Then, since the hand drum shaped outer peripheral surface of the roller is plastically deformed so as to follow the outer peripheral surface of the rack shaft, the outer peripheral surface of the roller can come in line contact with the outer peripheral surface of the rack shaft with a high precision without conducting a precise current work, and the treatment of the hand drum shaped outer peripheral surface of the roller can be easily conducted with a high precision. 
     INDUSTRIAL APPLICABILITY 
     In the rack and pinion type steering device having the rack guide which can prevent the rattle noise from occurring and the method of manufacturing the steering device, a contact state of the outer peripheral surface of the rack shaft with the outer peripheral surface of the roller of the rack guide holder changes from a point contact to a line contact to enlarge the contact area and reduce the contact surface pressure. With the above configuration, it is possible to prevent the wear of the contact surface, prevent an increase in the excessive rack guide movable amount, and prevent rattle noise from occurring. Also, the treatment of the hand drum shaped outer peripheral surface of the roller can be easily conducted with a high precision.

Technology Category: 4