Title of Invention

TENSIONER

Abstract

In a tensioner, in which a shaft portion (10) of a rotary member (2) is rotatably supported by a support portion (11) of a case (1) to support a load that acts on a pressing member (3), the pressing member (3) being restrained from rotating by a bearing (5), among the rotary member (2), the shaft portion (10) of the rotary member (2), the support portion (11) of the case (1), lthe pressing member (3), and the bearing (5), a covering film of a three element alloy of nickel, phosphorous, and tungsten, or a covering film lof a three element alloy of nickel, phosphorous, and boron is formed at least on a surface of the shaft portion (10) of the rotary member (2).

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. Background Art 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. 6 , 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 is brought into threaded engagement 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 receiving 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 receiving 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. Large changes in a braking force of the tensioner occur with this type of conventional tensioner due to wear over time with use and changes in a lubrication state. A device in which abrasion resistant surface processing, such as Kanigen plating, is performed on a rotary member 2 and on a male screw portion 9 and a female screw portion 13 of a pressing member 3, respectively, in order to resolve these types of problems is proposed in Japanese Utility Model Registration No. 2120655. However, with the conventional Kanigen plating abrasion resistant surface process, in a state where a fluctuating load acting on the tensioner is relatively large and there are violent vibrations present, durability problems remain such as a process layer wearing due to the passage of time to cause changes in the braking force. JP 11-63125 A discloses a structure of the "tensioner comprising a case; a rotary member rotatably received in the case in a state where a motion of the rotary member in an axial direction is restrained, a pressing member that is brought into threaded engagement with the rotary member and movable in the axial direction, whose rotation with respect to the case is restrained and on which a load from a force transmitting member acts in the axial direction, and a spring which is received in an inner portion of the case and transmits a rotational force to the rotary member, the rotary member having its axial portion rotatably supported by a support portion of the case to support a load that acts on the pressing member, the pressing member being restrained from rotating by a bearing". However, JP 11-63125 A does not disclose a structure of the type in which "among the rotary member, the shaft portion of the rotary member, the support portion of the case, the pressing member, and the bearing, a covering film of a three element alloy of nickel, phosphorous, and tungsten, or a covering film of a three element alloy of nickel, phosphorous, and boron is formed at least on a surface of the shaft portion of the rotary member". JP 2001-32896 A discloses that a covering film of a solid lubricant is formed on a sliding portion of a tensioner. Disclosed, as a solid lubricant, is one of a molybdenum-based lubricant, a fluororesin-based lubricant, a graphite- based lubricant, and a phosphate-based solid lubricant or a mixture of those. However, the covering film of the solid lubricant has a minimum returning torque value in an early stage of an apparatus operation. After that, the returning torque value increases, and the covering film is then changed to a stable state. The covering film is completely different from the covering film of the present invention for preventing the wear being caused with the passage of the operating time, the changes in the braking force (frictional- force) due to the changes in the lubrication state, and the changes in the characteristics. According to JP 2001- 32896 A "in the early stage of an operation, the solid lubricants come into contact with each other, and the returning torque value exhibits the minimum value. Next, attrition of the solid lubricant proceeds. After that, when driving is continued, a base metal of each of components appears, and the state moves to a state where steel (metal) materials come into contact with each other on a sliding surface. After that, a stable returning torque value is indicated". This document does not describe the object, the structure, and the effect of the present invention. JP 2001-64005 A discloses a coated sliding member in which, on a high- hardness hard carbon film having a Knoop hardness equal to or more than 2000 and equal to or less than 8000, an upper layer coating film including a carbon film, a metal film, or a compound film having a Knoop hardness less than 2000 is stacked. There is described that as a material for used for the upper layer, one or more kinds of carbon, aluminum, silicon, titanium, chrome, iron, nickel, zinc, molybdenum, silver, tungsten, gold, sulfide such as molybdenum disulfide, boride such as titanium boride, phosphate such as manganese phosphate is used. However, JP 2001-64005 A describes the hard carbon film of the covered sliding member, and is different from the present invention. It is an object of JP 2001-64005 A to realize sliding characteristics with a small coefficient of friction and a small aggressiveness to a mating member in a case where a surface covered with the hard carbon film is rough, whereas it is the object of the present invention to provide a tensioner in which wear of a portion that exerts a largest influence on a braking force and characteristics with a passage of an operating time and the changes in the lubrication state thereof may be prevented so that the changes in the braking force and the changes in the characteristics are small, and a stable performance for a long period of time may be obtained. JP 2000-126489 A discloses a sewing machine part having a surface formed with a composite plating film obtained by substantially uniformly codepositing nickel or a nickel-based alloy with fluorine-containing composition fine particles, the sewing machine component being imparted with low wear performance and low friction performance to be in contact with thread or cloth. JP 2000-126489 A describes that the component having the surface formed with the composite plating film obtained by substantially uniformly codepositing a three element alloy of nickel, phosphorus, and tungsten or a three element alloy of nickel, boron, and tungsten, has high hardness characteristics owing to tungsten and maintains a high surface hardness even when a codeposition amount of the fluorine-containing composition fine particles is increased. Since this document is about an invention of the sewing machine component to be in contact with thread or cloth, and describes the low wear performance and the low friction performance of the sewing machine component with respect to thread or cloth, its object is completely different from that of the present invention. JP 2001-146919 A discloses that a thin covering layer is provided to an inner surface of a dynamic pressure bearing sleeve. There is described that a thin film layer is a plating of an alloy matrix of nickel, phosphorus, and boron and codeposited graphite. However, JP 2001-146919 A relates to a dynamic pressure bearing sleeve including brass or phosphor bronze as a material thereof. There is no description of the object, the structure, and the effect related to the tensioner of the present invention. The present invention has been proposed in order to solve the above problems. An object of the present invention is to provide a tensioner that displays stable performance over a long period of time with little changes in the braking force and in the characteristics of the tensioner, by preventing occurrence of wear that accompanies usage over time, and changes in the lubrication state, in portions that impart the greatest influence to the braking force and characteristics of the tensioner. Disclosure of the Invention According to the present invention, there is provided a tensioner characterized by including: a case; a rotary member rotatably stored in the case in a state where a motion of the rotary member in an axial direction is restrained; a pressing member that is brought into threaded engagement with the rotary member and movable in the axial direction, whose rotation with respect to the case is restrained, and on which a load from a force transmitting member acts in the axial direction; and a spring that is stored in an inner portion of the case and transmits a rotational force to the rotary member, the rotary member having its axial portion rotatably supported by a support portion of the case to support a load that acts on the pressing member, the pressing member being restrained from rotating by a bearing, the tensioner being characterized in that: among the rotary member, the shaft portion of the rotary member, the support portion of the case, the pressing member, and the bearing, a covering film of a three element alloy of nickel, phosphorous, and tungsten, or a covering film of a three element alloy of nickel, phosphorous, and boron is formed at least on a surface of the shaft portion of the rotary member. A rotary member for propelling a pressing member is a very important motion element. The shaft portion of the rotary member is supported in the support portion of the case. An excessive load acts on the shaft portion of the rotary member due to the rotating member rotating in the support portion of the case, or due to a return force acting on the rotating member through the pressing member. Consequently, abrasion and a frictional force develop. In the present invention, a covering film of a three element alloy of nickel, phosphorous, and tungsten is formed on at least the shaft portion of the rotary member. Therefore, there is little development of changes in wear and frictional resistance, and the performance becomes stable. According to the tensioner of the present invention, stable characteristics, in which there is little change in the braking force (frictional force) and in the characteristics of the tensioner due to wear that accompanies usage over time and due to changes in the lubrication state, can be maintained 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 of the present invention, Fig. 2 is a cross sectional view of a part of an engine showing a usage example of a tensioner. Fig. 3 is an enlarged cross sectional view of a part of a shaft portion showing a state where a three element alloy covering film is formed. Fig. 4 is a graph showing experimental results for a relationship between aging temperature and hardness. Fig. 5 is a graph showing experimental results for a relationship between passage of time and braking torque, and Fig. 6 is a cross sectional view showing a conventional example of a tensioner. Best Mode for carrying out the Invention In order to describe the present invention in more detail. 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, 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. A tensioner shown in Fig. 1 is provided with a case 1 in which a cavity portion la is formed in an axial direction, a rotary member 2 and a pressing member 3 that are inserted into the cavity portion la of the case 1 in a state where they are in threaded engagement with each other, a torsion spring 4 that imparts a rotational force to the rotary member 2, a bearing 5 which is attached to a distal end portion of the case 1 to restrain rotation of the pressing member 3, and a. bellows 6 capable of expanding and contracting which covers a space between the case 1 and the pressing member 3. A rear end portion of the pressing member 3 is inserted into an inner portion of the case 1, and a front end portion of the pressing member projects out to a portion outside of the case 1. A sealing bolt 8 is screwed onto an opening of a proximal end portion of the case 1 through a packing 7 , maintaining the airtight characteristics on the proximal end side. A male screw portion 9 is formed in a front side portion of the rotary member 2, and a female screw portion 13 is formed in an inner circumference of the hollow pressing member 3 . By bringing the female screw portion 13 into threaded engagement with the male screw portion 9, 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 the torsion spring 4. The spring 4 extends in a direction along the axis line X of the rotary member 2 and the pressing member 3, and one end portion 4a of the spring 4 is inserted into a slit 12 of the rotary member 2. The slit 12 is directed along the axis line X direction of the rotary member 2. Another end portion 4b of the spring 4 is latched to the case 1, or is latched to a bearing 5 that is attached to the case 1. Both end portions 4a and 4b of the spring 4 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 12 from outside the case 1 while the sealing bolt 8 is detached, 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 owing to the spring 4 twisting. The bearing 5 is provided in the front end portion of the case 1. A fixing member such as a ring spring 15 fixes the bearing 5 to the case 1. A non-circular sliding hole 5a is formed in the bearing 5, and the pressing member 3 passes through the sliding hole 5a. An outer circumferential surface of the pressing member 3 is formed in a non-circular shape in correspondence with the sliding hole 5a of the bearing 5. Mating the pressing member 3 with the sliding hole 5a of the bearing 5 restricts rotation of the pressing member 3 relative to the case 1. A cap 14 is attached to the front end of the pressing member 3. The cap 14 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 4 is twisted, elastic energy in the spring 4 causes the rotary member 2 to rotate in the first direction. This rotation is transmitted to the pressing member 3 through the screw portions 9 and 13, and the bearing 5 restricts the rotation of the pressing member 3 . A rotational 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 9 and 13, and the rotary member 2 thus withstands an urging force of the spring 4 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., The male screw portion 9 on the distal end portion side of the rotary member 2, and a shaft portion 10 on the proximal end portion side of the rotary member 2, are provided in a connected row arrangement. The shaft portion 10 is supported within a support portion 11 of the case 1, so as to perform rotational support. The shaft portion 10 of the rotary member 2 is formed as a large diameter portion having a larger diameter than that of the screw portion 9. A receiving surface 17 for the support portion 11 in the case 1 faces an end surface 16 of the large diameter shaft portion 10. The end surface 16 of the shaft portion 10 of the rotary member 2 contacts the receiving surface 17 of the support portion 11 of the case 1. The load Z that is input to the pressing member 3 is supported by the receiving surface 17 of the support portion 11. A covering film of a three element alloy of nickel, phosphorous , and tungsten is formed on the shaft portion 10 of the rotary member 2. The three element alloy covering film is formed by a plating made from the three element alloy of nickel, phosphorous, and tungsten. Fig. 3 is an enlarged partial cross sectional view showing a state where a three element alloy covering film 22 is formed on the shaft portion 10 of the rotary member 2. The three element alloy may also be a three element alloy of elements other than nickel, phosphorous, and tungsten. For example, a three element alloy of nickel, phosphorous, and boron can also be used. In this type of tensioner, fluctuations in frictional torque and large changes in performance develop due to wear accompanying usage over time, and due to changes in a lubrication state. It is thought that this is largely due to the following reasons. (1) Changes in wear and frictional resistance that are caused by an urging force of the spring 4, and by a frictional resistance between the male screw portion 9 and the female screw portion 13. (2) Changes in wear and frictional resistance due to the rotary member 2 rotating in the support portion 11 of the case 1 which supports the shaft portion 10 of the rotary member 2, or due to an excessive load acting on the support portion 11 which is caused by a return force acting on the rotary member 2 through the pressing member 3. (3) Wear of a contact portion between the bearing 5 and the case 1 due to a pressing contact force acting on the contact portion as a rotational force of the spring 4 is transmitted to the bearing 9 that restrains rotation of the pressing member 3. Rotation of the rotary member 2 for propelling the pressing member 3 is a very important motion element, and the shaft portion 10 of the rotary member 2 is supported by the support portion 11 of the case 1, and therefore the reason (2) above is considered to be important regarding changes in the characteristics of the tensioner. In this embodiment mode, the covering film of the three element alloy of nickel, phosphorous, and tungsten is formed on the shaft portion 10 of the rotary member 2, and therefore there is little wear, and the frictional resistance does not change. The characteristics therefore become stable over a long period of time, without large fluctuations developing in the frictional torque and in the frictional resistance, and without large changes in the characteristics. The same is also true for the covering film of the three element alloy of nickel, phosphorous, and boron. From these points, it is preferable that the three element alloy covering film be formed not only on the shaft portion 10 of the rotary member 2, but also on the support portion 11 of the case 1. It is most preferable to form the three element alloy covering film on all of the surfaces of the support portion 11 of the case 1, the rotary member 2, the shaft portion 10 of the rotary member 2, the pressing member 3, the bearing 5, and the like, which are members in which the phenomena described in the reasons (1) to (3) above develop. However, when considering points such as cost and effect, the three element alloy covering film may be performed at least on the shaft portion 10 of the rotary body 2. The three element alloy covering film of nickel, phosphorous, and tungsten, or of nickel, phosphorous and boron is used in the present invention for the following reasons. (1) It is a three element alloy, and there is no dispersion due to the dispersal state. (2) It can be manufactured under stable heat treatment conditions, and the plating hardness is stable. (3) It is stabilized by heat treatment at a relatively low temperature, and therefore there is little influence on oxidation and materials. (4) The adhesion property is high, and the film thickness is uniform. (5) The plating hardness is high, there is superior abrasion resistance, and there is little influence on the braking force (frictional resistance) due to the lubrication state over a long period of time. Fig. 4 is a graph showing experimental results for a relationship between aging temperature and hardness. According to Fig. 4, it can be understood that the hardness stabilizes in the vicinity of 350°C for the three element alloy of nickel, phosphorous , and tungsten, and that the hardness is higher than that of an alloy of nickel and phosphorous . The hardness stabilizes in the vicinity of 400°C for the alloy of nickel and phosphorous. Fig. 5 is a graph showing experimental results for a relationship between aging time and braking torque. According to Fig. 5, it can be understood that a product embodying the present invention, in which the nickel, phosphorous, and tungsten covering film is implemented, has a lower braking torque and fewer changes in the braking torque over the passage of time, than a conventional product in which a covering film of a nickel and phosphorous alloy is implemented. It should be noted that the above-mentioned embodiment of the invention is not intended to limit the present invention. Various changes may be made to the present invention without departing from the gist of the invention. 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 owing 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. WE CLAIM : 1. A tensioner comprising: a case (1); a rotary member (2) rotatably stored in the case (1) in a state where a motion of the rotary member in an axial direction is restrained; a pressing member (3) that is brought into threaded engagement with the rotary member (2) and movable in the axial direction, whose rotation with respect to the case (1) is restrained and on which a load from a force transmitting member acts in the axial direction; and a spring (4) which is stored in an inner portion of the case (1) and transmits a rotational force to the rotary member (2), the rotary member (2) having its axial portion (10) rotatably supported by a support portion (11) of the case (1) to support a load that acts on the pressing member (3), the pressing member (3) being restrained from rotating by a bearing (5), the tensioner being characterized in that: among the rotary member (2), the shaft portion (10) of the rotary member (2), the support portion (11) of the case (1), the pressing member (3), and the bearing (5), a covering film of a three element alloy of nickel, phosphorous, and tungsten, or a covering film of a three element alloy of nickel, phosphorous, and boron is formed at least on a surface of the shaft portion (10) of the rotary member (2). In a tensioner, in which a shaft portion (10) of a rotary member (2) is rotatably supported by a support portion (11) of a case (1) to support a load that acts on a pressing member (3), the pressing member (3) being restrained from rotating by a bearing (5), among the rotary member (2), the shaft portion (10) of the rotary member (2), the support portion (11) of the case (1), the pressing member (3), and the bearing (5), a covering film of a three element alloy of nickel, phosphorous, and tungsten, or a covering film of a three element alloy of nickel, phosphorous, and boron is formed at least on a surface of the shaft portion (10) of the rotary member (2).

Documents:

735-KOLNP-2005-FORM-27.pdf

735-kolnp-2005-granted-abstract.pdf

735-kolnp-2005-granted-assignment.pdf

735-kolnp-2005-granted-claims.pdf

735-kolnp-2005-granted-correspondence.pdf

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

735-kolnp-2005-granted-drawings.pdf

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

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

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

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

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

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

735-kolnp-2005-granted-gpa.pdf

735-kolnp-2005-granted-letter patent.pdf

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

735-kolnp-2005-granted-specification.pdf