Title of Invention

TENSIONER

Abstract

There is disclosed a tensioner that converts a rotary force of a rotary member (2) into an impulsive force in an axis line direction of a pressing member (3), the tensioner comprising: a case (1); the rotary member (2) being rotatably received in the case (1) in such a state that movement thereof in the axis line direction is caused to be restrained; the pressing member (3) being threadedly engaged with the rotary member (2), said pressing member being movable in the axis line direction, and rotation thereof with respect to the case (1) being caused to be restrained, and on said pressing member (3) a load (Z) from a force transmitting member (202) is adapted to act in the axis line direction; and a spring (5) being stored in an inner portion of the case (1), which imparts the rotary force to the rotary member (2), characterized in that: an end portion (22) of the rotary member (2) is rotatably supported by a bearing surface (19) of the case (1); the end portion (22) of the rotary member (2) receives the load (Z) that acts on the pressing member (3); and a precision of a contact surface (9a) of the bearing surface (19) that contacts the end portion (22) of the rotary member (2) is set such that a surface roughness Rmax is equal to or less than 4.0 S, and a levelness is equal to or less than 2 µm.

Full Text

DESCRIPTION TENSIONER Technical Field The present invention relates to a tensioner that imparts a predetermined tensile force to a force transmitting member such as a chain or a timing belt that drives a camshaft of an engine mounted in a vehicle, such as a four wheel automobile or a two wheel vehicle, for example. Background Arts A tensioner is used in order to maintain a substantially fixed tensile force on a chain or a timing belt, even if slackness develops in the chain or the timing belt due to stretching or wear during use. As shown in Fig. 10, a conventional general tensioner is provided with a case 101, a rotary member 102 having a male screw portion 102a, a pressing member 103 having a female screw portion 103a that screws together with the male screw portion 102a of the rotary member 102, a spring 104 that urges the rotary member 102 in a first rotary direction, a bearing 109 in order to restrain rotation of the pressing member 103, and the like. When the rotary member 102 is rotated in the first direction by the spring 104, the pressing member 103 moves in an axis line direction. The rotary member 102 is stored in the case 101, and an end surface 102b of the rotary member 102 is rotatably supported by a bearing surface 101b of the case 101. The tensioner urges the rotary member 102 in the first rotary direction by means of a repulsive force that accumulates when the spring 104 twists in a direction that is opposite to the first rotary direction. A rotary torque of the rotary member 102 moves the pressing member 103 in an axis line direction projecting from the case 101. A distal end of the pressing member 103 directly or indirectly pushes the force transmitting member such as the chain or the timing belt. Further, when the tensile force of the chain or the timing belt increases, a force pushing back the pressing member 103 increases. In this case, the pressing member 103 is pushed back in the axis line direction toward an inner portion of the case 101, resisting a sum total of torques mainly including an urging force of the spring 104, a frictional resistance between the male screw portion 102a and the female screw portion 103a, and a frictional resistance between the end surface 102b of the rotary member 102 and the bearing surface 101b of the case 101. The tensioner can impart a fixed tensile force to the chain or the timing belt based on those torques and the like. The frictional torque between the end surface 102b of the rotary member 102 and the bearing surface 101b of the case 101 largely fluctuates in the conventional tensioner, and large changes in performance arise. For example, the return characteristics of the pressing member 103 may become poor, and the initial characteristics may become unstable. In order to solve this type of problem, Japanese Patent No. I 2998100 proposes a tensioner that stabilizes initial characteristics and reduces changes in characteristics during operation. Conventional tensioners having stabilized performance are also preferable, but large changes in the tensile force of the force transmitting member (chain or timing belt) may also occur in those tensioners, caused by wear that develops with use over time. In view of those points, an object of the present invention is to provide a tensioner in which a bearing is provided in an end portion contact surface of a bearing surface of a case that supports an end portion of a rotary member, or in a bearing surface of the case, and in which changes in performance are prevented by setting the initial surface precision of the end portion contact surface of the bearing to the same order as the surface roughness after use, and leveling the contact surface with high precision, the tensioner of a quality having performance that is further stabilized more than a conventional tensioner. Disclosure of the Invention According to the present invention, there is provided a tensioner which converts a rotary force of a rotary member into an impulsive force in an axis line direction of a pressing member, the tensioner including: a case; the rotary member rotatably received in the case in a state where a movement in the axis line direction is restrained; the pressing member which is threadedly engaged with the rotary member, which is movable in the axis line direction, whose rotation with respect to the case is restrained, and on which a load from a force transmitting member acts in the axis line direction; and a spring which is stored in an inner portion of the case, and which imparts the rotary force to the rotary member, characterized in that: an end portion of the rotary member is rotatably supported by a bearing surface of the case; the end portion of the rotary member receives the load that acts on the pressing member; and a precision of a contact surface of the bearing surface that contacts the end portion of the rotary member is set such that a surface roughness Rmax is equal to or less than 4.0 S and a levelness is equal to or less than 2 urn. A f rictional torque between the end portion of the rotary member and the bearing surface of the case thus decreases and becomes constant, the initial characteristics stabilize, changes in characteristics over time during use become smaller, and the performance characteristics are stabilized over a long period of time. Further, the tensioner of the present invention is a tensioner which converts a rotary force of a rotary member into an impulsive force in an axis line direction of a pressing member, the tensioner including: a case; the rotary member rotatably received in the case in a state where a movement in the axis line direction is restrained; the pressing member which is threadedly engaged with the rotary member, which is movable in the axis line direction, whose rotation with respect to the case is restrained, and on which a load from a force transmitting member acts in the axis line direction; and a spring which is stored in an inner portion of the case, and which imparts the rotary force to the rotary member, characterized in that an end portion of the rotary member is rotatably supported by a bearing provided in a bearing surface of the case, the end portion of the rotary member receives the load that acts on the pressing member, and a precision of a contact surface of the bearing surface that contacts the end portion of the rotary member is set such that a surface roughness Rmax is equal to or less than 4.0 S and a levelness is equal to or less than 2 urn. Actions and effects similar to the aspect of the present invention described above are also provided by the tensioner according to the present invention. In addition, the tensioner according to the present invention is characterized in that the bearing is a closed end cylindrical member, or a bearing in which a cylindrical member and a base plate are separate members and the precision of the contact surface of the bearing surface that contacts the end portion of the rotary member is set such that the surface roughness Rmax is equal to or less than 4.0 S and the levelness is equal to or less than 2 urn. Precise polishing thus becomes easy to implement, and the precision of the surface roughness and the levelness can be increased. Thus, in the tensioner according to the present invention, by setting the precision of the contact surface of the bearing surface supporting the rotary member, which contacts the rotary member end portion such that the surface roughness is equal to or less than 4.0 S and the levelness is equal to or less than 2 urn, the initial surface precision is given to the same degree as the surface roughness resulting from wear over time with use, and changes in tensile force with use can be prevented. In addition, rotary sliding between the end surface of the rotary member and the bearing surface of the case, or the bearing, is made satisfactory. Therefore, there is little reduction in the tensile force over time with use, and characteristics can be kept stable over a long period of time. Brief Description of the Accompanying Drawings Fig. 1 is a cross sectional view of a tensioner showing an embodiment mode of the present invention. Fig. 2 is a cross sectional view of a portion of an engine that shows an example of tensioner use. Fig. 3 is a perspective view showing a closed end cylinder which is a bearing. Fig. 4 is a perspective view showing a bearing in which a cylinder and a base plate are separate. Fig. 5 is a cross sectional view showing a conventional surface shape. Fig. 6 is a cross sectional view showing a surface shape of the present invention, Fig. 7 is a graph showing experimental results for a relationship between elapsed time of use and force transmitting member (chain) tensile force. Fig. 8 is a graph showing experimental results for a relationship between surface roughness and force transmitting member (chain) tensile force. Fig. 9 is a graph showing experimental results for a relationship between levelness and force transmitting member (chain) tensile force, and Fig. 10 is a cross sectional view showing a conventional example of a tensioner. Best Mode for Carrying Out the Invention A detailed description of the present invention is made according to the appended drawings. Fig. 1 is a cross sectional view of a tensioner showing an embodiment mode of the present invention, and Fig. 2 is a cross sectional view of a portion of an engine showing a usage example of the tensioner. The tensioner is employed in a power transmission mechanism 201 of an automobile engine 200 shown in Fig,. 2, for example. The power transmission mechanism 201 transmits rotary motion of the engine 200 to a cam shaft 203 through an endless force transmitting member 202, such as a timing belt or a chain. The tensioner is therefore mounted in a predetermined location of the engine 200, 7 and pushes the force transmitting member 202 in a direction shown by an arrow V by means of an impulsive force that is described later, thus maintaining a constant tensile force. The tensioner shown in Fig. 1 is provided with a case 1, a rotary member 2, and a cylindrical pressing member 3. The rotary member 2 is stored in an inner portion of the case 1. A back end portion of the pressing member 3 is inserted into the inner portion of the case 1, and a front end portion of the pressing member 3 projects to a portion outside the case 1. A cavity portion 1a for inserting the rotary member 2 and the pressing member 3 is formed in the inner portion of the case 1. An open portion 1b is formed in the front end portion of the case 1, and the pressing member 3 moves into and out of the open portion 1b along an axis line X of the pressing member 3. An open portion 1c is also formed in the back end portion of the case 1. A stopper 14 can be inserted into the open portion lc in order to lock rotation of the rotary member 2 when necessary. A slit 23 is formed in a back end portion of the rotary member 2. Inserting a tip of the stopper 14 into the slit 23 can lock rotation of the rotary member 2. The stopper 14 is removed from the slit 23 of the rotary member 2 when using the tensioner. A male screw portion 21 is formed in a front side portion of the rotary member 2, and a female screw portion 13 is formed in a hollow inner circumference of the pressing member 3. By screwing the male screw portion 13 and the female screw portion 21 together, it becomes possible to attach the rotary member 2 and the pressing member 3 together so that the rotary member 2 and the pressing member 3 can rotate relative to each other, and can advance in the axis line X direction while rotating. The rotary member 2 and the pressing member 3 in the attached state described above are then inserted into a spring 5. The spring 5 extends in a direction along the axis line X of the rotary member 2 and the pressing member 3, and one end portion 5a of the spring 5 is inserted into the slit 23 of the rotary member 2. The slit 23 is directed along the axis line X of the rotary member 2. Another end portion 5b of the spring 5 is latched to the case 1, or is latched to a bearing 6 that is attached to the case 1. Both end portions 5a and 5b of the spring 5 are thus latched to the rotary member 2 and the case 1, respectively. When a tip of a jig used for rotation (a screwdriver, for example) is inserted into the slit 23, and the rotary member 2 is made to rotate about the axis line X, energy (torque) of the rotary member 2, which rotates the rotary member 2 in an opposite direction, accumulates due to the spring 5 twisting. The bearing 6 is provided in the front end portion of the case 1. A fixing member such as a ring spring 7, for example, fixes the bearing 6 to the case 1. A non-circular sliding hole 6a is formed in the bearing 6, and the pressing member 3 passes through the sliding hole 6a. An outer circumferential surface of the pressing member 3 is formed in a non-circular shape that corresponds to the sliding hole 6a of the bearing 6. Mating the pressing member 3 with the sliding hole 6a of the bearing 6 restricts rotation of the pressing member 3 relative to the case 1. A cap 8 is attached to the front end of the pressing member 3. The cap 8 contacts the timing belt or the chain used as the force transmitting member 202 directly, or indirectly through a relay member. When the rotary member 2 is made to rotate in a second direction and the spring 5 is twisted, elastic energy in the spring 5 causes the rotary member 2 to rotate in the first direction. This rotation is transmitted to the pressing member 3 through the screw portions 13 and 21, and the bearing 6 restricts the rotation of the pressing member 3. A rotary force of the rotary member 2 is thus converted into an impulsive force in the axis line X direction of the pressing member 3. The pressing member 3 thus advances in a direction projecting from the case 1. On the other hand, a load Z applied from the force transmitting member 2 such as a timing belt or a chain acts on the pressing member 3, and pushes the pressing member 3 in the axis line X direction. This pushing force is transmitted to the rotary member 2 through the screw portions 13 and 21, and the rotary member 2 thus resists an urging force of the spring 5 and rotates in the second direction. By the rotary member 2 rotating in this direction, the pressing member 3 is pushed back within the case 1. The tensile force of the force transmitting member can be kept nearly constant by this motion. A large diameter portion 28 having a diameter larger than that of the screw portion 21 is provided in the back end portion of the rotary member 2. A bearing surface 19 of the case 1 that is formed in the perimeter of the open portion 1c faces an end surface 22 of the large diameter portion 28. A bearing 9 is disposed between the bearing surface 19 and the end surface 22 of the rotary member 2. A closed end cylinder 9b, like that shown in Fig. 3, is used in this embodiment for the bearing 9. The end surface 22 of the rotary member 2 contacts a base surface of the cylinder 9b, that is, a contact surface 9a of the end surface 22 of the rotary member 2 . The load Z that acts on the pressing member 3 supports the bearing surface 19 of the case 1 through the end surface 22 of the rotary member 2 and the closed end cylinder 9b. The base surface of the cylinder 9b, that is, the contact surface 9a of the end surface 22 of the rotary member 2, is polished precisely so that the surface roughness Rmax is equal to or less than 4.0 S, preferably equal to or less than 2.0 S, and the levelness is equal to or less than 2 µm. This precise polishing may also be performed on an inner circumferential surface of a cylinder portion of the cylinder 9b. Further, as shown in Fig. 4, the bearing 9 may also be a bearing having a cylinder member 9c that is separate from a base plate 9d. In this case, the precise polishing is performed at least on the contact surface 9a of the base plate 9d. The bearing 9 is provided in the bearing surface 22 of the case 1 that supports the end surface 22 of the rotary member 2 in this embodiment mode. The contact surface 9a of the bearing 9 that contacts the end surface 22 of the rotary member 2 is given such that a surface roughness Rmax is equal to or less than 4 .0S, preferably equal to or less than 2.0 S, and a levelness is equal to or less than 2 urn. The end surface 22 of the rotary member 2 therefore slides smoothly when the rotary member 2 is rotated with respect to the bearing 9 of the case 1 about its axis line. There are no changes in frictional torque, and therefore the characteristics are stabilized. That is, satisfactory return characteristics can be achieved. Accordingly, rotary sliding of the end surface 22 of the rotary member 2 with respect to the bearing 9 becomes even smoother when precise polishing is also performed on the inner circumferential surfaces of the cylinders 9b and 9c. It is therefore preferable to perform precise polishing on the inner circumferential surfaces of the cylinders 9b and 9c. Note that, the precision of a conventional contact surface has a surface roughness Rmax equal to or less than 8.0 s, and a levelness equal to or less than 15 µm. Fig. 5 is a cross sectional view showing a conventional surface shape. The precision of the contact surface 9a of the present invention has a surface roughness Rmax equal to or less than 4.0 S, and a levelness equal to or less than 2 µm. Fig. 6 is a cross sectional view showing a surface state of the contact surface 9a. Fig. 7 is a graph showing experimental results for a relationship between elapsed time of use and tensile force. According to Fig. 7, it can be understood that although the tensioner of the present invention has a tensile force that is maintained nearly constant over time during use and the characteristics thereof are stable, the conventional tensioner has large changes and unstable characteristics. Further, Fig. 8 is a graph showing experimental results for a relationship between surface roughness and force transmitting member (chain) tensile force, and Fig. 9 is a graph showing experimental results for a relationship between levelness and force transmitting member (chain) tensile force. According to Fig. 8 and Fig. 9 , it can be understood that there is a tendency for the force transmitting member (chain) tensile force to decrease as the surface roughness and the levelness decrease. It can be understood that the force transmitting member (chain) tensile force is stable and satisfactory when the surface roughens Rmax is equal to or less than 4.0 S and the levelness is equal to or less than 2 µm, and that a large effect is provided in the precision of the present invention. Furthermore, the tensile force further stabilizes when the surface roughness Rmax is equal to or less than 2.0 S, which is preferable. It should be noted that the embodiment mode described above does not limit the present invention. Various changes are permitted to the present invention in a scope that does not deviate from the gist of the invention. For example, a processing method for ensuring surface precision is not limited to precise polishing. Chemical polishing, forging, precision pressing, and the like may also be used. Furthermore, the precision of the bearing surface 22 of the case 1 may also be given such that a surface roughness Rmax is equal to or less than 4.0 S and a levelness is equal to or less than 2 µm, without providing the bearing 9 in the bearing surface 22 of the case 1 that supports the end surface of the rotary member 2. Actions and effects that are similar to those of the embodiment mode described above can also be provided in this case as well. Industrial Applicability As described above, the tensioner according to the present invention is used in order to maintain a nearly constant tensile force, even if slackness develops in the chain or the timing belt due to stretching or wear during use. The tensioner is therefore effective when used with a chain, a timing belt, or the like that drives a camshaft of an engine mounted in a vehicle such as a four wheel automobile or a two wheel vehicle, for example. We claim : 1. A tensioner that converts a rotary force of a rotary member (2) into an impulsive force in an axis line direction of a pressing member (3), the tensioner comprising: a case (1); the rotary member (2) being rotatably received in the case (1) in such a state that movement thereof in the axis line direction is caused to be restrained; the pressing member (3) being threadedly engaged with the rotary member (2), said pressing member being movable in the axis line direction,and rotation thereof with respect to the case (1) being caused to be restrained, and on said pressing member (3) a load (Z) from a force transmitting member (202) is adapted to act in the axis line direction; and a spring (5) being stored in an inner portion of the case (1), which imparts the rotary force to the: rotary member (2), characterized in that: an end portion (22) of the rotary member (2) is rotatably supported by a bearing surface (19) of the case (1); the end portion (22) of the rotary member (2) receives the load (Z) that acts on the pressing member (3); and a precision of a contact surface (9a) of the bearing surface (19) that contacts the end portion (22) of the rotary member (2) is set such that a surface roughness Rmax is equal to or less than 4.0 S, and a levelness is equal to or less than 2 µm. 2. A tensioner which converts a rotary force of a rotary member (2) into an impulsive force in an axis line direction of a pressing member (3), the tensioner comprising: a case (1) ; the rotary member (2) being rotatably received in the case (1) in such a state that movement thereof in the axis line direction is caused to be restrained; the pressing member (3) being threadedly engaged with the rotary member (2), said pressing member being movable in the axis line direction, and rotation thereof with respect to the case (1) being caused to be restrained, and on said pressing member (3) a load (Z) from a force transmitting member (202) is adapted to act in the axis line direction; and a spring (5) being received in an inner portion of the case (1), which imparts the rotary force to the rotary member (2), characterized in that: an end portion (22) of the rotary member (2) is rotatably supported by a bearing provided in a bearing surface (19) of the case (1) ; the end portion (22) of the rotary member (2) receives the load (Z) that acts on the pressing member (3); and a precision of a contact surface (9a) of the bearing that contacts the end portion (22) of the rotary member (2) is set such that a surface roughness Rmax is equal to or less than 4.0 S and a levelness is equal to or less than 2 µm. 3. A tensioner as claimed in claim 2, wherein, the bearing is one of a closed end cylinder (9b) and a bearing in which a cylinder member (9c) and a base plate (9d) are separate members; and the precision of the contact surface (9a) of the bearing that contacts the end portion (22) of the rotary member (2) is set such that the surface roughness Rmax is equal to or less than 4.0 S and the levelness is equal to or less than 2 µm. There is disclosed a tensioner that converts a rotary force of a rotary member (2) into an impulsive force in an axis line direction of a pressing member (3), the tensioner comprising: a case (1); the rotary member (2) being rotatably received in the case (1) in such a state that movement thereof in the axis line direction is caused to be restrained; the pressing member (3) being threadedly engaged with the rotary member (2), said pressing member being movable in the axis line direction, and rotation thereof with respect to the case (1) being caused to be restrained, and on said pressing member (3) a load (Z) from a force transmitting member (202) is adapted to act in the axis line direction; and a spring (5) being stored in an inner portion of the case (1), which imparts the rotary force to the rotary member (2), characterized in that: an end portion (22) of the rotary member (2) is rotatably supported by a bearing surface (19) of the case (1); the end portion (22) of the rotary member (2) receives the load (Z) that acts on the pressing member (3); and a precision of a contact surface (9a) of the bearing surface (19) that contacts the end portion (22) of the rotary member (2) is set such that a surface roughness Rmax is equal to or less than 4.0 S, and a levelness is equal to or less than 2 µm.

Documents:

734-KOLNP-2005-CORRESPONDENCE.pdf

734-KOLNP-2005-FORM 27.pdf

734-KOLNP-2005-FORM-27.pdf

734-kolnp-2005-granted-abstract.pdf

734-kolnp-2005-granted-assignment.pdf

734-kolnp-2005-granted-claims.pdf

734-kolnp-2005-granted-correspondence.pdf

734-kolnp-2005-granted-description (complete).pdf

734-kolnp-2005-granted-drawings.pdf

734-kolnp-2005-granted-examination report.pdf

734-kolnp-2005-granted-form 1.pdf

734-kolnp-2005-granted-form 13.pdf

734-kolnp-2005-granted-form 18.pdf

734-kolnp-2005-granted-form 3.pdf

734-kolnp-2005-granted-form 5.pdf

734-kolnp-2005-granted-gpa.pdf

734-kolnp-2005-granted-reply to examination report.pdf

734-kolnp-2005-granted-specification.pdf