JP5090863B2 - Chain tensioner - Google Patents

Description

  The present invention relates to a chain tensioner used for maintaining tension of a timing chain that drives a camshaft of an automobile engine.

  In general, an engine of an automobile transmits rotation of a crankshaft to a camshaft through a timing chain, and opens and closes a valve of a combustion chamber by the rotation of the camshaft. Here, in order to keep the tension of the chain within an appropriate range, a tension adjusting device composed of a chain guide provided so as to be swingable around a fulcrum shaft and a chain tensioner that presses the chain guide toward the chain is often used. It is done.

  As a chain tensioner incorporated in this tension adjusting device, a rod is inserted into a bottomed cylindrical housing having one end opened so as to be movable in the axial direction, and a male screw is provided on the outer periphery between the rod and the bottom of the housing. A screw rod is provided, and a nut member having an internal thread that engages with a male screw of the screw rod is provided on the inner periphery. A return spring supported by the nut member is used to urge the rod in a direction in which the rod protrudes from the housing. There is a spring in which a rod is urged toward the rod, and the screw rod is brought into contact with the rod.

  When the chain tension increases during engine operation, the chain tensioner moves in a direction in which the rod is pushed into the housing (hereinafter referred to as “push-in direction”) due to the chain tension, and absorbs the tension of the chain. At this time, the screw rod is rotated with respect to the nut member while being repeatedly advanced and retracted within the gap between the female screw and the male screw due to the vibration of the chain.

  On the other hand, when the tension of the chain is reduced during the operation of the engine, the urging force of the return spring moves the rod in the direction protruding from the housing (hereinafter referred to as “protruding direction”) to absorb the slack of the chain.

  When the engine is stopped, the chain does not vibrate even if the chain force increases depending on the cam stop position, so the male screw of the screw rod is received by the female screw of the nut member, and the position of the rod is fixed. For this reason, the chain is not easily loosened when the engine is restarted, and the engine can be started smoothly.

  By the way, in this chain tensioner, since the screw rod is in contact with the rod, when the screw rod rotates, the contact portion of the screw rod with the rod is worn. As this wear progresses, the rotational resistance of the screw rod increases due to friction with the rod, and as a result, when the chain tension increases during engine operation, the screw rod may not rotate smoothly.

  The problem to be solved by the present invention is to provide a chain tensioner in which the contact portion of the screw rod with respect to the rod is not easily worn.

  In order to solve the above-mentioned problem, the screw rod is composed of a cylindrical member having the male screw on the outer periphery, and a cap member having a hardness higher than that of the cylindrical member and fixed to one end of the cylindrical member. The member was made to contact the rod.

  The cap member may be fixed by press-fitting the cap member into one end of the cylindrical member. The cap member is fitted into one end of the cylindrical member, and the cylindrical member and the cap member are fitted together. Preferably, the cap member is fixed by solid phase welding of the surfaces.

  The cap member may be increased in hardness by performing shot peening, or may be increased in hardness by forming at least one of a hard coating and a hard layer on the surface of the cap member. Examples of the hard film include a ceramic film and a diamond-like carbon film, and examples of the hard layer include a nitride compound layer and an oxide layer.

  Further, when the hardness of the cap member is 786 HV or more, the durability of the cap member can be ensured, and when the surface roughness of the cap member is Ra 1.6 or less, the rotational resistance of the screw rod can be kept small. it can.

  In the chain tensioner of the present invention, the hardness of the cap member that contacts the rod among the members constituting the screw rod is higher than the hardness of the cylindrical member. .

  Further, the cap member is fixed to one end of the cylindrical member, and the cap member is fixed by solid-phase welding the fitting surface of the cylindrical member and the cap member. And high durability. Further, since the welding is solid phase welding performed at a temperature below the melting point, the joining accuracy between the cylindrical member and the cap member is high, and the dimensional accuracy of the screw rod is high.

  FIG. 1 shows a chain transmission device incorporating a chain tensioner 1 according to an embodiment of the present invention. In this chain transmission device, a sprocket 3 fixed to the crankshaft 2 of the engine and a sprocket 5 fixed to the camshaft 4 are connected via a chain 6, and the chain 6 rotates the crankshaft 2. This is transmitted to the camshaft 4 and the valve (not shown) of the combustion chamber is opened and closed by the rotation of the camshaft 4.

  The chain 6 is in contact with a chain guide 8 supported so as to be swingable about the fulcrum shaft 7, and the chain tensioner 1 presses the chain guide 8 toward the chain 6.

  As shown in FIG. 2, the chain tensioner 1 has a bottomed cylindrical housing 9 with one end opened, and a rod 10 inserted into the housing 9 so as to be movable in the axial direction. The housing 9 is fixed to an engine block (not shown) with bolts 11.

  The rod 10 slidably penetrates a ring-shaped oil seal 12 fixed to the inner periphery of the housing 9, and hydraulic oil is sealed in the housing 9 by the oil seal 12. In the housing 9, a screw rod 15 having a male screw 14 on the outer periphery is provided between the insertion end of the rod 10 into the housing 9 and the bottom 13 of the housing 9.

  In addition, a nut member 17 having an internal thread 16 on the inner periphery that engages with the external thread 14 of the screw rod 15 is provided in the housing 9. The female screw 16 and the male screw 14 are formed in a sawtooth shape having an asymmetrical cross section along the axis, and the flank of the pressure side flank 18 that receives pressure when a force is applied in the direction of pushing the rod 10 into the housing 9. The angle is larger than the flank angle of the play side flank 19.

  The screw rod 15 includes a cylindrical member 15A having an external thread 14 on the outer periphery, and a cap member 15B fixed to one end of the cylindrical member 15A on the rod 10 side. Here, as shown in FIG. 3, the cap member 15B is fixed by fitting the cap member 15B into one end of the cylindrical member 15A with a tightening margin in a state where an electric current flows between the cap member 15B and the cylindrical member 15A. At this time, since the impurity layer 20 on the surface of the cap member 15B is scraped off and cleaned, the fitting surface 21 of the cylindrical member 15A and the cap member 15B is solid-phase welded.

  That is, as shown in FIG. 3A, a voltage is applied between the cylinder member 15A and the cap member 15B with the cap member 15B facing one end of the cylinder member 15A, as shown in FIG. Then, the cap member 15B is brought into contact with one end of the cylindrical member 15A. Further, as shown in FIG. 3 (c), when the cap member 15B is fitted into one end of the cylindrical member 15A, the heat generation of the current flowing through the contact portion between the cap member 15B and the cylindrical member 15A, and the cap member 15B and the cylindrical member When the impurity layer 20 on the surface of the cap member 15B is scraped off and cleaned by friction of the contact portion of the member 15A, and the fitting of the cap member 15B is completed as shown in FIG. The fitting surface 21 of 15A and the cap member 15B is joined at a temperature below the melting point.

  The screw rod 15 formed in this way is urged toward the rod 10 by a rod spring 22 incorporated between the cap member 15B and the bottom 13 of the housing 9, as shown in FIG. The cap member 15 </ b> B is in contact with the insertion end of the rod 10 into the housing 9.

  The cap member 15B has a higher hardness than the cylindrical member 15A by heat treatment or the like. Further, the contact portion 23 of the cap member 15B with respect to the rod 10 is formed in a spherical shape in order to reduce the rotational resistance of the screw rod 15. Further, the contact portion 23 of the cap member 15B with respect to the rod 10 is made harder than the cylindrical member 15A by performing shot peening, and the hardness is 786 HV or more. Further, the surface roughness of the contact portion 23 with respect to the rod 10 of the cap member 15B is set to Ra 1.6 or less.

  A buffer spring 24 that supports the nut member 17 is incorporated between the nut member 17 and the bottom 13 of the housing 9. A stopper 25 that restricts the compression range of the buffer spring 24 is incorporated between the buffer spring 24 and the nut member 17.

  A wear ring 26 slidably in contact with the inner periphery of the housing 9 is fixed to the outer periphery of the rod 10, and a return spring 27 is incorporated between the wear ring 26 and the nut member 17. One end of the return spring 27 is supported by the nut member 17, and the other end presses the wear ring 26, and the pressure pushes the rod 10 in a direction protruding from the housing 9. The wear ring 26 is formed with an oil passage 28 penetrating in the axial direction.

  Next, an operation example of the chain tensioner 1 will be described.

  When the tension of the chain 6 increases during the operation of the engine, the screw rod 15 moves in the pushing direction by the tension of the chain 6 and absorbs the tension of the chain 6. At this time, the screw rod 15 rotates with respect to the nut member 17 while repeating forward and backward movements within the gap between the female screw 16 and the male screw 14 due to the vibration of the chain 6.

  On the other hand, when the tension of the chain 6 is reduced during engine operation, the screw rod 15 is moved in the protruding direction by the urging force of the return spring 27 and absorbs the slack of the chain 6.

  When the fluctuation of the rotational force of the crankshaft 2 during the combustion cycle is large, or when the fluctuation of the rotational resistance of the camshaft 4 is large, or when resonance occurs in the engine, the buffer spring 24 is compressed, so that the chain 6 prevents excessive tension.

  In addition, when the engine is stopped, the tension of the chain 6 may increase depending on the stop position of a cam (not shown) connected to the camshaft 4. In this case, the chain 6 does not vibrate, so the male screw 14 of the screw rod 15. Is received by the female screw 16 of the nut member 17, and the position of the screw rod 15 is fixed. Therefore, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  In this chain tensioner 1, the hardness of the cap member 15B that contacts the rod 10 among the members constituting the screw rod 15 is higher than the hardness of the cylindrical member 15A, so that the contact portion 23 of the screw rod 15 with respect to the rod 10 is worn. Hard and durable.

  Moreover, since this chain tensioner 1 welds the fitting surface 21 of the cylinder member 15A and the cap member 15B, the fixing strength of the cylinder member 15A is high and the durability is excellent. Further, since the welding is solid phase welding performed at a temperature below the melting point, the joining accuracy between the cylindrical member 15A and the cap member 15B is high, and the dimensional accuracy of the screw rod 15 is high.

  In the above embodiment, the cap member 15B is fixed by solid-phase welding the fitting surface 21 of the cylinder member 15A and the cap member 15B. However, the cap member 15B is fixed by press-fitting the cap member 15B into one end of the cylinder member 15A. May be performed.

  Moreover, in the said embodiment, although the hardness of the cap member 15B is raised by performing shot peening to the contact part 23 with respect to the rod 10 of the cap member 15B, in order to raise the hardness of the cap member 15B, the rod 10 of the cap member 15B. A hard film such as a ceramic film or a diamond-like carbon (DLC) film, or a hard layer such as an oxide layer or a nitride compound layer may be formed on the surface of the contact portion 23.

The front view which shows the chain transmission apparatus incorporating the chain tensioner of embodiment of this invention 1 is an enlarged cross-sectional view of the chain tensioner shown in FIG. It is a figure which shows the process which fixes a cap member to the cylinder member which comprises the screw rod shown in FIG. 2, (a) is a figure which shows the state which made the cap member oppose the end of a cylinder member, (b), The figure which shows the state which made the cap member contact the end of a cylinder member, (c) is a figure which shows the state in the middle of fitting a cap member, (d) is the figure which shows the state which the fitting of the cap member was completed

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chain tensioner 9 Housing 10 Rod 13 Bottom 14 Male screw 15 Screw rod 15A Cylindrical member 15B Cap member 16 Female screw 17 Nut member 21 Fitting surface 22 Rod spring 27 Return spring

Claims (7)

A rod (10) is inserted into a bottomed cylindrical housing (9) whose one end is open so as to be movable in the axial direction, and a male screw is interposed between the rod (10) and the bottom (13) of the housing (9). A screw rod (15) having (14) on the outer periphery is provided, and a nut member (17) having an inner screw (16) on the inner periphery that engages with the male screw (14) of the screw rod (15) is provided. The return spring (27) supported by the member (17) urges the rod (10) in a direction protruding from the housing (9), and urges the screw rod (15) toward the rod (10). In a chain tensioner (1) provided with a rod spring (22) and having its screw rod (15) rotatably contacted with the rod (10),
The screw rod (15) includes a cylindrical member (15A) having the male screw (14) on the outer periphery, and a cap member having a higher hardness than the cylindrical member (15A) and fixed to one end of the cylindrical member (15A). (15B), and the cap member (15B) having higher hardness than the cylindrical member (15A) is in contact with the rod (10).   The chain tensioner according to claim 1, wherein the cap member (15B) is fixed by press-fitting the cap member (15B) into one end of the cylindrical member (15A).   The cap member (15B) is fitted into one end of the cylindrical member (15A), and the cap member (15A) and the fitting surface (21) of the cap member (15B) are solid-phase welded, whereby the cap member The chain tensioner according to claim 1, wherein (15B) is fixed.   The chain tensioner according to any one of claims 1 to 3, wherein the cap member (15B) is shot peened to increase the hardness of the cap member (15B).   The chain tensioner according to any one of claims 1 to 3, wherein at least one of a hard coating and a hard layer is formed on a surface of the cap member (15B).   The chain tensioner according to any one of claims 1 to 5, wherein the cap member (15B) has a hardness of 786 HV or higher. The chain tensioner according to any one of claims 1 to 6, wherein a surface roughness of the cap member (15B) is Ra 1.6 or less.

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