JP2009156281A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner in which a contact part with a rod seat of a screw rod is hardly worn. <P>SOLUTION: In the chain tensioner 1, a plunger 10 is slidably inserted in a cylinder 9, a screw rod 18 having a male screw 17 screw-engaged with a female screw 16 formed in an inner circumference of the plunger 10 on its outer circumference is provided in the cylinder 9, and a projecting end from the plunger 10 of the screw rod 18 is brought into contact with a rod seat 19 provided on a bottom of the cylinder 9, the plunger 10 is urged in the projecting direction from the cylinder 9 by a return spring 24 built in between the screw rod 18 and the plunger 10, and the chain 6 is pressed by the plunger 10. The screw rod 18 comprises a cylindrical member 18A having the male screw 17 on its outer circumference, and a cap member 18B fixed to one end of the cylindrical member 18A while its hardness is higher than that of the cylindrical member 18A. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 via 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 chain tension within an appropriate range, a tension adjusting device consisting of a chain guide that can be swung 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 the tension adjusting device, a plunger is slidably inserted in a cylinder with a bottom having an opening at one end in an axial direction, and the plunger is inserted with an opening at the insertion end into the cylinder. A rod seat in which a screw rod having a male screw on its outer periphery that engages with a female screw provided on the inner periphery of the plunger is provided in the cylinder, and a protruding end of the screw rod from the plunger is provided on the bottom of the cylinder The plunger is urged in a direction protruding from the cylinder by a return spring incorporated between the screw rod and the plunger, and the chain is pressed by the plunger (Patent Document). 1).

  When the chain tension increases during engine operation, the chain tensioner moves in a direction in which the plunger is pushed into the cylinder (hereinafter referred to as “push-in direction”) due to the chain tension, and absorbs the chain tension. At this time, the screw rod rotates with respect to the plunger while repeating forward and backward movements 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 engine operation, the plunger moves in a direction protruding from the cylinder (hereinafter referred to as “protruding direction”) by the urging force of the return spring, and absorbs the slackness of the chain.

When the engine is stopped, the chain does not vibrate even if the chain force increases due to the cam stop position, so that the internal thread of the plunger is received by the external thread of the screw rod, and the position of the plunger is fixed. Therefore, when the engine is restarted, the chain is hardly slackened, and the engine can be started smoothly.
JP 2001-124159 A

  By the way, in this chain tensioner, since the protruding end of the plunger of the screw rod is in contact with the rod sheet, when the screw rod rotates, the contact portion of the screw rod with respect to the rod sheet is worn. As this wear progresses, the rotational resistance of the screw rod increases due to friction with the rod sheet. As a result, there is a risk that the screw rod will not rotate smoothly when the chain tension increases during engine operation.

  The problem to be solved by the present invention is to provide a chain tensioner in which a contact portion of a screw rod with respect to a rod sheet 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 sheet.

  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 shot peening. The cap member may be increased in hardness by forming a ceramic film, a nitride compound layer, a diamond-like carbon film, or an oxide film on the surface of the cap member. Also good.

  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.

  Since the hardness of the cap member that contacts the rod sheet is higher than the hardness of the cylindrical member among the members constituting the screw rod, the chain tensioner of the present invention is less likely to wear the contact portion of the screw rod with respect to the rod sheet. Excellent. Therefore, an increase in the rotational resistance of the screw rod due to wear of the contact portion with the rod sheet is unlikely to occur.

  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 includes a bottomed cylindrical cylinder 9 with one end opened, and a plunger 10 inserted into the cylinder 9 so as to be slidable in the axial direction. The cylinder 9 is fixed to an engine block (not shown) with bolts 11.

  An oil supply passage 13 that communicates with a pressure chamber 12 surrounded by the cylinder 9 and the plunger 10 is formed in the cylinder 9. The oil supply passage 13 is connected to an oil supply pump (not shown), and introduces hydraulic oil sent from the oil supply pump into the pressure chamber 12. A check valve 14 that allows only the flow of hydraulic oil from the outside to the inside of the pressure chamber 12 is provided at the end of the oil supply passage 13 on the pressure chamber 12 side.

  A minute leak gap 15 is formed between the sliding surfaces of the plunger 10 and the cylinder 9, and hydraulic oil in the pressure chamber 12 leaks through the leak gap 15.

  The plunger 10 is formed in a bottomed cylindrical shape whose opening end into the cylinder 9 is open, and a female screw 16 is formed on the inner periphery thereof. In addition, a screw rod 18 having a male screw 17 threadedly engaged with the female screw 16 of the plunger 10 formed on the outer periphery is incorporated in the cylinder 9, and the protruding end of the screw rod 18 from the plunger 10 is the bottom of the cylinder 9. It is in contact with the rod sheet 19 fixed to.

  The male screw 17 and the female screw 16 are formed in a sawtooth shape having an asymmetric cross section along the axis, and the flank of the pressure side flank 20 that receives pressure when a force in a direction of pushing the plunger 10 into the cylinder 9 is applied. The angle is larger than the flank angle of the play side flank 21.

  As shown in FIG. 3, the screw rod 18 includes a cylindrical member 18A having a male screw 17 on the outer periphery and a cap member 18B fixed to one end of the cylindrical member 18A. Here, as shown in FIG. 6, the cap member 18B is fixed by fitting the cap member 18B into one end of the cylindrical member 18A with a tightening margin in a state where a current flows between the cap member 18B and the cylindrical member 18A. At this time, since the impurity layer 22 on the surface of the cap member 18B is scraped and cleaned, the fitting surface 23 of the cylindrical member 18A and the cap member 18B is solid-phase welded.

  That is, as shown in FIG. 6A, a voltage is applied between the cylindrical member 18A and the cap member 18B with the cap member 18B facing one end of the cylindrical member 18A, as shown in FIG. 6B. Then, the cap member 18B is brought into contact with one end of the cylindrical member 18A. Further, as shown in FIG. 6 (c), when the cap member 18B is fitted into one end of the cylindrical member 18A, the heat generation of the current flowing through the contact portion between the cap member 18B and the cylindrical member 18A, and the cap member 18B and the cylindrical member When the impurity layer 22 on the surface of the cap member 18B is scraped off and cleaned by the friction of the contact portion of the member 18A, and the fitting of the cap member 18B is completed as shown in FIG. 18A and the fitting surface 23 of the cap member 18B will be in the state joined at the temperature below melting | fusing point.

  As shown in FIG. 2, the screw rod 18 formed in this way is assembled so that the cap member 18 </ b> B becomes a protruding end from the plunger 10, and the cap member 18 </ b> B contacts the rod sheet 19.

  The cap member 18B is harder than the cylindrical member 18A by heat treatment or the like. Furthermore, as shown in FIG. 4, the contact portion 27 of the cap member 18 </ b> B with respect to the rod sheet 19 is increased in hardness by performing shot peening, and the hardness is 786 HV or higher. In order to reduce the rotational resistance of the screw rod 18, the surface roughness of the contact portion 27 of the cap member 18B with respect to the rod sheet 19 is set to Ra 1.6 or less.

  As shown in FIG. 2, a return spring 24 is incorporated between the plunger 10 and the screw rod 18. One end of the return spring 24 is supported by the screw rod 18, and the other end presses the plunger 10 via the spring seat 25, and the pressing presses the plunger 10 in a direction in which it protrudes from the cylinder 9. Yes.

  Further, an assist spring 26 that urges the plunger 10 in a direction to protrude from the cylinder 9 is incorporated between the plunger 10 and the rod seat 19, and the spring force of the return spring 24 is assisted by the assist spring 26. Yes.

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

  When the tension of the chain 6 is reduced during the operation of the engine, the plunger 10 moves in the protruding direction by the urging force of the return spring 24 and absorbs the slack of the chain 6. At this time, the check valve 14 is opened, and the hydraulic oil is supplied into the pressure chamber 12 through the oil supply passage 13, so that the plunger 10 moves quickly.

  On the other hand, when the tension of the chain 6 increases during engine operation, the plunger 10 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 18 is rotated with respect to the plunger 10 by the urging force of the return spring 24 while repeatedly moving forward and backward within the gap between the female screw 16 and the male screw 17 due to the vibration of the chain 6.

  When the engine is stopped, the tension of the chain 6 may increase depending on the stop position of the camshaft 4. In this case, the chain 6 does not vibrate, so the pressure side flank 20 of the internal thread 16 of the plunger 10 is replaced with the external thread 17 of the screw rod 18. The pressure side flank 20 is received and the position of the plunger 10 is fixed. Therefore, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  In the chain tensioner 1, the hardness of the cap member 18 </ b> B that contacts the rod sheet 19 among the members constituting the screw rod 18 is higher than the hardness of the cylindrical member 18 </ b> A. Hard to wear and excellent in durability. Therefore, an increase in rotational resistance of the screw rod 18 due to wear of the contact portion 27 with respect to the rod sheet 19 is unlikely to occur.

  Moreover, since this chain tensioner 1 welds the fitting surface 23 of the cylinder member 18A and the cap member 18B, the fixing strength of the cylinder member 18A 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 18A and the cap member 18B is high, and the dimensional accuracy of the screw rod 18 is high.

  In the above embodiment, the cap member 18B is fixed by solid-phase welding the fitting surface 23 of the cylindrical member 18A and the cap member 18B. However, the cap member 18B is fixed by press-fitting the cap member 18B into one end of the cylindrical member 18A. May be performed.

  Moreover, in the said embodiment, although the hardness of the cap member 18B is raised by performing shot peening to the contact part 27 with respect to the rod sheet 19 of the cap member 18B, in order to raise the hardness of the cap member 18B, as shown in FIG. In addition, a film such as a ceramic film, a nitride compound layer, a diamond-like carbon (DLC) film, or an oxide film may be formed on the surface of the contact portion 27 of the cap member 18B with respect to the rod sheet 19.

The front view which shows the tension adjustment apparatus incorporating the chain tensioner of embodiment of this invention 1 is an enlarged cross-sectional view of the chain tensioner shown in FIG. FIG. 2 is an enlarged sectional view of the screw rod shown in FIG. FIG. 3 is an enlarged sectional view of the vicinity of the contact portion of the screw rod shown in FIG. 3 with respect to the rod sheet. The expanded sectional view of the contact part vicinity with respect to the rod sheet | seat which shows the modification of the screw rod 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 6 Chain 9 Cylinder 10 Plunger 16 Female thread 17 Male thread 18 Screw rod 18A Cylindrical member 18B Cap member 19 Rod seat 23 Fitting surface 24 Return spring

Claims (10)

  A plunger (10) is slidably inserted axially into a bottomed cylindrical cylinder (9) having an open end, and the plunger (10) is inserted into the cylinder (9) with an open end. A screw rod (18) having a male screw (17) on the outer periphery is provided in the cylinder (9), and has a cylindrical shape, and the screw rod (18) is engaged with a female screw (16) provided on the inner periphery of the plunger (10). The protruding end of the plunger (10) from the plunger (10) is brought into contact with the rod seat (19) provided at the bottom of the cylinder (9), and the return is assembled between the screw rod (18) and the plunger (10). A chain tensioner (1) that urges the plunger (10) in a direction protruding from the cylinder (9) by a spring (24) and presses the chain (6) by the plunger (10). The screw rod (18) has a cylindrical member (18A) having the male screw (17) on the outer periphery, and is harder than the cylindrical member (18A), and is fixed to one end of the cylindrical member (18A). A chain tensioner comprising a cap member (18B), wherein the cap member (18B) is in contact with the rod sheet (19).   The chain tensioner according to claim 1, wherein the cap member (18B) is fixed by press-fitting the cap member (18B) into one end of the cylindrical member (18A).   The cap member (18B) is fitted into one end of the cylindrical member (18A), and the cap member (18A) and the fitting surface (23) of the cap member (18B) are solid-phase welded, whereby the cap member The chain tensioner according to claim 1, wherein (18B) is fixed.   The chain tensioner according to any one of claims 1 to 3, wherein the cap member (18B) is shot peened to increase the hardness of the cap member (18B).   The chain tensioner according to any one of claims 1 to 3, wherein a ceramic film is formed on a surface of the cap member (18B) to increase the hardness of the cap member (18B).   The chain tensioner according to any one of claims 1 to 3, wherein a nitride compound layer is formed on a surface of the cap member (18B) to increase the hardness of the cap member (18B).   The chain tensioner according to any one of claims 1 to 3, wherein a diamond-like carbon film is formed on a surface of the cap member (18B) to increase the hardness of the cap member (18B).   The chain tensioner according to any one of claims 1 to 3, wherein an oxide film is formed on a surface of the cap member (18B) to increase the hardness of the cap member (18B).   The chain tensioner according to any one of claims 1 to 8, wherein the cap member (18B) has a hardness of 786 HV or higher.   The chain tensioner according to any one of claims 1 to 9, wherein a surface roughness of the cap member (18B) is Ra 1.6 or less.

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