JP5010369B2 - Auto tensioner - Google Patents

Description

  The present invention mainly relates to an auto tensioner used to maintain tension of a timing chain or timing belt that drives a camshaft of an engine.

  In general, an engine transmits rotation of a crankshaft to a camshaft via a timing chain or a timing belt (which will be described by taking a timing chain as an example) housed in an engine room in an engine cover. The combustion chamber valve is opened and closed by rotating the shaft.

  As an auto-tensioner that keeps the chain tension constant, a cylindrical plunger is slidably inserted in the axial direction into a cylinder that is open at one end, and is engaged with a female screw formed on the inner periphery of the plunger. A screw rod having a male screw on the outer periphery is provided so as to protrude from the insertion end of the plunger into the cylinder, a sheet member is provided in the cylinder for supporting the protruding end of the screw rod from the plunger, and the plunger is removed from the cylinder. A return spring that urges in a protruding direction is supported by the screw rod, and a chain or belt is pressed by a protruding end of the plunger from a cylinder (Patent Document 1).

  In the auto tensioner, during engine operation, the plunger absorbs the vibration of the chain by repeatedly moving forward and backward within the gap between the male screw and the female screw. When the chain tension changes, the plunger rotates little by little while repeating forward and backward within the range of the gap between the female screw and the male screw, and the plunger moves to a position where the urging force of the return spring balances with the chain tension.

Further, when the engine is stopped, the chain tension may be larger than the urging force of the return spring depending on the stop position of the cam. At this time, the chain does not vibrate, so the plunger does not move. Therefore, when the engine is restarted, the chain is not easily loosened, and the engine can be started smoothly.
JP 2007-32603 A

  However, the above-described auto tensioner cannot push the plunger into the cylinder beyond the range of the gap between the male screw and the female screw. When the vibration of the chain is large, such as when the resistance variation is large or when resonance occurs in the engine, the chain vibration cannot be absorbed, and the chain tension may be excessive.

  Also, the above-mentioned auto tensioner has a slow movement speed of the plunger when the chain tension changes, so if the chain travel line changes greatly due to the thermal expansion of the engine block, it absorbs the change in the chain travel line. In some cases, the chain tension was excessive.

  The problem to be solved by the present invention is to provide an auto tensioner in which the chain tension is less likely to be excessive even when the chain vibrates greatly or when the chain travel line changes greatly.

  In order to solve the above problems, a cylindrical plunger is slidably inserted in an axial direction into a cylinder whose one end is open, and has a male screw on its outer periphery that engages with a female screw formed on the inner periphery of the plunger. A screw rod is provided so as to protrude from the insertion end of the plunger into the cylinder, and a sheet member is provided in the cylinder for supporting the protruding end of the screw rod from the plunger, and the plunger is attached in a direction protruding from the cylinder. An elastic member capable of compressing the seat member in the axial direction of the cylinder in an auto tensioner in which a return spring is supported by the screw rod and the chain or belt is pressed by a protruding end of the plunger from the cylinder. Supported by.

  The elastic member can be formed of, for example, a spring, and at this time, the spring can be formed by alternately overlapping wave washers and flat washers.

  The auto tensioner is preferably configured to prevent the seat member from rotating with respect to the cylinder.

  In the auto tensioner, an oil introduction port for introducing splashed oil outside the cylinder into the cylinder is formed in the cylinder, and the oil introduced from the oil introduction port into the cylinder is lubricated between the male screw and the female screw. To be able to.

  At this time, the auto tensioner can form a film for preventing the formation of a lubricating film by an oil additive on at least one of the surface of the male screw and the surface of the female screw. A diamond-like carbon film can be used.

The auto tensioner can have the following configuration.
1) The female screw and the male screw are formed so that the flank angle of the pressure side flank receiving pressure when a force in the direction of pushing the plunger into the cylinder is larger than the flank angle of the play side flank.
2) The plunger includes a cylindrical member having both ends formed on the inner periphery and an open end, and a lid member fixed to one end of the cylindrical member. The lid member projects from the cylinder of the plunger. Place at the end.

  In the auto tensioner according to the present invention, since the seat member is supported by an elastic member that is compressible in the axial direction of the cylinder, the elastic member compresses, so that the plunger is moved into the cylinder beyond the gap between the male screw and the female screw. Can be pushed in. For this reason, even when the chain vibrates greatly or when the travel line of the chain changes greatly, the chain tension is unlikely to become excessive, and the chain life is unlikely to decrease.

  Further, in the case where the seat member is prevented from rotating with respect to the cylinder, even when the elastic member is compressed, the rotational displacement due to the torsional deformation is not transmitted to the screw rod even if the elastic member is twisted in the rotational direction. Therefore, the axial movement of the plunger due to the torsional deformation of the elastic member can be prevented.

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

  The chain 6 is pressed by the auto tensioner 1 via a chain guide 8 supported so as to be swingable about a fulcrum shaft 7. The auto tensioner 1 is fixed to an engine block (not shown) with bolts 9.

  As shown in FIG. 2, the auto tensioner 1 has a cylindrical plunger 11 inserted in a bottomed cylinder 10 having one end opened so as to be slidable in the axial direction. The plunger 11 includes a cylindrical member 12 whose both ends are open, and a lid member 13 fixed to one end of the cylindrical member 12, and the lid member 13 is disposed at a protruding end of the plunger 11 from the cylinder 10. A screw rod 14 is incorporated in the plunger 11 with one end protruding from the insertion end of the plunger 11 into the cylinder 10.

  A return spring 15 is incorporated between the lid member 13 and the screw rod 14. One end of the return spring 15 is supported by the screw rod 14, and the other end presses the lid member 13 via the spring seat 16, and the plunger 11 is biased in a direction protruding from the cylinder 10 by the pressing. ing. The plunger 11 is in contact with the chain guide 8 at the protruding end from the cylinder 10.

  A male screw 17 is formed on the outer periphery of the screw rod 14, and the male screw 17 is engaged with a female screw 18 formed on the inner periphery of the cylindrical member 12. The male screw 17 and the female screw 18 are formed in a sawtooth shape having an asymmetrical cross-sectional shape along the axis, and the pressure side flank 20 that receives pressure when a force in the direction of pushing the plunger 11 into the cylinder 10 is applied. The angle is larger than the flank angle of the play side flank 19.

  An oil introduction port 21 for introducing splashes of engine oil outside the cylinder 10 into the cylinder 10 is formed on the outer periphery of the cylinder 10. The engine oil introduced into the cylinder 10 through the oil introduction port 21 is a male screw. 17 and the internal thread 18 are lubricated.

A diamond-like carbon film (hereinafter referred to as a DLC film) 22 is formed on the surface of the male screw 17 as shown in FIG. Therefore, when engine oil added with molybdenum dithiocarbamate (MoDTC) or molybdenum dithiophosphate (MoDTP) is used, these additives decompose on the sliding surface and contain molybdenum disulfide (MoS ₂ ). Although the lubricating film is formed, the DLC film 22 prevents the formation of the lubricating film on the surface of the male screw 17.

  As shown in FIG. 3, the screw rod 14 is supported at its protruding end from the plunger 11 by a sheet member 23 inserted into the cylinder 10 so as to be slidable in the axial direction. The sheet member 23 has a tapered surface 24 that expands toward the screw rod 14, and the screw rod 14 is supported by the tapered surface 24 so that the center of the screw rod 14 coincides with the center of the cylinder 10. . Further, as shown in FIG. 4, the protrusion 25 formed on the outer periphery of the sheet member 23 is engaged with an axially extending groove 26 formed on the inner periphery of the cylinder 10. Thus, the seat member 23 is prevented from rotating around the cylinder 10.

  As shown in FIG. 3, the seat member 23 is supported by a spring 28 incorporated between the seat member 23 and the bottom 27 of the cylinder 10. The spring 28 is formed by alternately laminating a corrugated washer 29 having a corrugated shape on an annular thin plate and an annular flat washer 30 in the axial direction of the cylinder 10, and the corrugated washer 29 is deformed. Thus, compression in the axial direction of the cylinder 10 is possible.

  The auto tensioner 1 absorbs the vibration of the chain 6 by the plunger 11 repeatedly moving forward and backward within the gap between the male screw 17 and the female screw 18 during engine operation. Further, when the tension of the chain 6 changes, the plunger 11 rotates little by little while repeating forward and backward within the gap between the female screw 18 and the male screw 17, and the position where the urging force of the return spring 15 balances with the tension of the chain 6. Until the plunger 11 moves.

  At this time, when the fluctuation of the rotational force of the crankshaft 2 during one combustion cycle is large, the fluctuation of the rotational resistance of the camshaft 4 is large, or when resonance occurs in the engine, the vibration of the chain 6 is When it becomes larger than the range of the gap between the male screw 17 and the female screw 18, the spring 28 is compressed to absorb the vibration of the chain 6 and to prevent excessive tension of the chain 6.

  In addition, even when the travel line of the chain 6 changes greatly due to the thermal expansion of the engine block, the spring 28 is compressed to absorb the change in the travel line of the chain 6 and to prevent excessive tension of the chain 6.

  On the other hand, when the engine is stopped, the tension of the chain 6 may be greater than the urging force of the return spring 15 depending on the stop position of a cam (not shown) connected to the camshaft 4, but at this time, the chain 6 vibrates. Therefore, the plunger 11 does not rotate with respect to the screw rod 14. For this reason, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  Since the auto tensioner 1 supports the seat member 23 with a spring 28, the plunger 11 can be pushed into the cylinder 10 beyond the range of the gap between the male screw 17 and the female screw 18 when the spring 28 is compressed. is there. For this reason, even when the chain 6 vibrates greatly or when the travel line of the chain 6 changes greatly, the tension of the chain 6 is unlikely to become excessive, and the life of the chain 6 is unlikely to decrease.

  Further, since the seat member 23 is prevented from rotating with respect to the cylinder 10 in the auto tensioner 1, even if the spring 28 is compressed in the rotational direction when the spring 28 is compressed, the rotation is caused by the torsional deformation. The displacement is not transmitted to the screw rod 14. Therefore, the axial movement of the plunger 11 due to the torsional deformation of the spring 28 can be prevented, and the operation reliability is high.

  Further, the auto tensioner 1 introduces the splash of engine oil in the engine room into the cylinder 10 from the oil introduction port 21 at the upper outer periphery of the cylinder 10, so that the oil tension (not shown) of the engine 10 There is no need to feed engine oil into Therefore, the capacity of the oil pump can be suppressed and the cost is low.

  Further, since the auto tensioner 1 has the DLC film 22 formed on the surface of the male screw 17, when the tension of the chain 6 increases, the force in the pushing direction acting on the plunger 11 is applied to the male screw 17 and the female screw 18. It can be surely received.

  Further, in the auto tensioner 1, the male screw 17 and the female screw 18 are formed so that the flank angle of the pressure side flank 20 is larger than the flank angle of the play side flank 19. The surface pressure acting on the pressure side flank 20 when receiving the tension is small, and the durability is excellent.

  In addition, since the auto tensioner 1 forms the plunger 11 by combining the cylindrical member 12 and the lid member 13 that are easy to process, the plunger 11 can be easily formed and the cost is low.

  In the above embodiment, the DLC film 22 is formed only on the surface of the male screw 17 out of the surface of the male screw 17 and the surface of the female screw 18, but the DLC film 22 may be formed only on the surface of the female screw 18, You may form in both the surface of the external thread 17 and the surface of the internal thread 18.

The front view which shows the chain transmission apparatus incorporating the auto tensioner of embodiment of this invention 1 is an enlarged sectional view of the auto tensioner shown in FIG. FIG. 2 is an enlarged sectional view of the vicinity of the sheet member Expanded sectional view along line IV-IV in FIG. FIG. 2 is an enlarged sectional view of the vicinity of the outer periphery of the screw rod.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Auto tensioner 6 Chain 10 Cylinder 11 Plunger 12 Cylindrical member 13 Lid member 14 Screw rod 15 Return spring 17 Male screw 18 Female screw 19 Play side flank 20 Pressure side flank 21 Oil inlet 22 Diamond-like carbon film 23 Sheet member 28 Spring 29 Wave washer 30 flat washers

Claims (7)

A male screw is inserted into a cylinder (10) having an open end so as to be slidable in the axial direction and is engaged with a female screw (18) formed on the inner periphery of the plunger (11). A screw rod (14) having (17) on the outer periphery is provided so as to protrude from an insertion end of the plunger (11) into the cylinder (10), and a protruding end of the screw rod (14) from the plunger (11). And a return spring (15) for biasing the plunger (11) in a direction protruding from the cylinder (10) is supported by the screw rod (14). In the auto tensioner (1) configured to press the chain (6) or the belt with the protruding end of the plunger (11) from the cylinder (10),
The seat member (23) is slidable in the axial direction relative to the cylinder (10) and supported by a spring (28) compressible in the axial direction of the cylinder (10), and the seat member (23) An auto tensioner characterized in that it is prevented from rotating with respect to the cylinder (10) . The auto tensioner according to claim 1 , wherein the spring (28) is formed by alternately laminating wave washers (29) and flat washers (30). The cylinder (10) is formed with an oil introduction port (21) for introducing splashed oil outside the cylinder (10) into the cylinder (10), and introduced into the cylinder (10) from the oil introduction port (21). The auto tensioner according to claim 1 or 2 , wherein the oil is lubricated between the male screw (17) and the female screw (18). The auto tensioner according to claim 3 , wherein a film (22) for preventing formation of a lubricating film by an oil additive is formed on at least one of the surface of the male screw (17) and the surface of the female screw (18). The auto tensioner according to claim 4 , wherein the film for preventing the formation of the lubricating film is a diamond-like carbon film (22). The flank angle of the pressure-side flank (20) that receives pressure when the force in the direction of pushing the plunger (11) into the cylinder (10) is applied to the female screw (18) and the male screw (17) is the idle side. The auto tensioner according to any one of claims 1 to 5 , wherein the auto tensioner is formed to be larger than a flank angle of the flank (19). The plunger (11) is composed of a cylindrical member (12) having both ends opened with the female screw (18) formed on the inner periphery, and a lid member (13) fixed to one end of the cylindrical member (12). The auto tensioner according to any one of claims 1 to 6 , wherein the lid member (13) is arranged at a protruding end of the plunger (11) from the cylinder (10).

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