JP2007255578A - Auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil feeding type auto tensioner in which a hydraulic damper operates from immediately after start of an engine. <P>SOLUTION: A plunger 13, and a return spring 14 imparting outward projecting property to the plunger 13, are built in a cylinder chamber 12 of a housing 11. The housing 11 is provided with an oil feeding passage 16 communicating with a pressure chamber 15 formed behind the plunger 13. A packing 40 is provided in the pressure chamber 15 to reduce volume, and when starting the engine, the pressure chamber 15 is immediately filled with oil fed into the oil feeding passage 16. Hydraulic damper action is thereby exhibited from immediately after the start of the engine. The packing 40 is provided with a flange 41 for receiving an end of the return spring 14. The flange 41 is abutted against a closed end face of a spring storing recessed part 18 opening at a rear end of the plunger 13. A discharge passage 43 communicating the pressure chamber 15 and the outside is formed at a tip end face of the flange 41. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an auto tensioner that keeps the tension of a timing chain or timing belt for driving a camshaft constant.

  In general, in a chain transmission that uses a timing chain or timing belt (hereinafter simply referred to as a chain) to transmit the rotation of the crankshaft to the camshaft, the adjustment force of the auto tensioner is applied to the slack side of the chain to increase the chain tension. I try to keep it constant.

  As the auto tensioner, a plunger in a cylinder chamber formed in the housing and a return spring for imparting outward protrusion to the plunger are incorporated, and the housing communicates with a pressure chamber formed on the back of the plunger. 2. Description of the Related Art Conventionally, an oil supply type is known in which an oil supply passage is formed and a pushing force applied to a plunger by an engine oil supplied from the oil supply passage into a pressure chamber is buffered.

  Further, the oil supply type auto tensioner includes a spring accommodating recess that allows the end of the return spring to be accommodated in the plunger, and a valve accommodating recess that opens at the distal end surface of the plunger and communicates the spring accommodating recess with the outside. Also provided is a relief valve built into the valve housing recess, and when the pressure in the pressure chamber exceeds the set pressure of the relief valve, the relief valve is opened to release the pressure in the pressure chamber to the outside. Known from.

  By the way, in any of the above conventional oil supply type auto tensioners, when the engine stops, the oil in the pressure chamber returns to the oil pump, so that a small amount of oil remains in the pressure chamber.

  For this reason, when the engine is restarted, the oil pump discharge amount is small immediately after the engine is started, and it takes time until the oil is filled in the pressure chamber. There was a disadvantage that occurred.

  An object of the present invention is to provide an oil supply type auto tensioner that shortens the filling time of oil in a pressure chamber and exhibits a hydraulic damper action immediately after the engine is started.

  In order to solve the above problems, in the present invention, a plunger is slidably incorporated in a cylinder chamber formed in the housing, and the plunger is housed with a spring from the rear end facing the pressure chamber formed on the back thereof. A concave portion, a valve accommodating concave portion having a smaller diameter than the spring accommodating concave portion, and an oil drain passage opening at the distal end surface of the plunger are formed, and the plunger is outwardly disposed between the closed end of the spring accommodating concave portion and the closed end of the cylinder chamber. Incorporates a return spring that gives the projecting performance of the valve, and a relief valve that opens when the pressure in the pressure chamber exceeds the set pressure and releases the pressure in the pressure chamber to the outside from the oil discharge passage. An oil supply passage communicating with the pressure chamber is formed in the housing, and a push applied to the plunger by oil supplied from the oil supply passage to the pressure chamber. In an auto tensioner configured to cushion the force, a cylindrical padding for reducing the volume in the pressure chamber is inserted into the end of the return spring on the plunger side, and the spring force of the return spring is received at the end of the padding. Since a flange that is pressed against the closed end surface of the spring accommodating recess is provided, and a discharge passage that communicates the spring accommodating recess and the valve accommodating recess is formed on at least one of the front end surface of the flange and the closed end surface of the spring accommodating recess. is there.

  As described above, since the volume in the pressure chamber is reduced by filling the pressure chamber, the oil filling time in the pressure chamber can be shortened. For this reason, when the engine is started, the pressure chamber is immediately filled with oil, and the hydraulic damper action is exhibited immediately after the engine is started, thereby preventing chain flapping.

  Moreover, since the padding moves together with the plunger by pressing the padding against the closed end surface of the spring accommodating recess formed in the plunger by the return spring, it is possible to prevent the generation of noise due to the collision of the padding.

  Further, by incorporating a cylindrical stuffing into the end of the return spring, it is possible to prevent the return spring from bending in the length direction, so-called bending of the return spring. It can always be loaded in the axial direction.

  In addition, since the discharge path is formed on at least one of the flange end face of the filling and the closed end face of the spring accommodating recess, the spring accommodating recess and the valve accommodating recess can be held in communication via the discharge path. In the use where the auto tensioner is mounted in an upward position with the plunger at the top, the air accumulated in the oil in the pressure chamber when the relief valve is opened can be discharged to the outside, and the deterioration of the damper effect due to air compression is suppressed can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a chain transmission for driving a camshaft, and a chain 5 is spanned between a sprocket 2 attached to an end of a crankshaft 1 and a sprocket 4 attached to an end of a camshaft 3. .

  A chain guide 6 is provided on the slack side of the chain 5. The chain guide 6 is swingable about a shaft 7, and an auto tensioner 10 that loads an adjustment force to the chain 5 via the chain guide 6 is provided on one side thereof.

  As shown in FIG. 2, the auto tensioner 10 has a housing 11 attached to the engine cover. A cylinder chamber 12 having a closed end is formed in the housing 11, and a plunger 13 and a return spring 14 that imparts outward protrusion to the plunger 13 are incorporated in the cylinder chamber 12.

  The housing 11 is provided with an oil supply passage 16 communicating with a pressure chamber 15 formed on the back of the plunger 13, and a check valve 17 is provided at an oil outlet portion of the oil supply passage 16. The check valve 17 closes the oil supply passage 16 when the pressure of the oil in the pressure chamber 15 becomes higher than the supply pressure of the oil sent to the oil supply passage 16.

  The plunger 13 is provided with a spring accommodating recess 18, a valve accommodating recess 19 and an oil discharge passage 20 in order from the rear end side located in the cylinder chamber 12, and the spring accommodating recess 18 is a part of the pressure chamber 15. And the tip of the return spring 14 is accommodated therein. The long return spring 14 can be employed by forming the spring accommodating recess 18, and the axial length of the housing 11 can be made compact.

  The oil drain passage 20 communicates the pressure chamber 15 with the outside. The oil discharge passage 20 is opened and closed by a relief valve 21 incorporated in the valve housing recess 19.

  Here, the relief valve 21 has a cylindrical body 23 in which an opening at one end is closed by a valve seat 22 having a valve opening 22a, and an oil discharge port 23a communicating with the oil discharge passage 20 is formed at the closed end of the other end. Further, a valve body 24 for opening and closing the valve port 22a and a spring 25 for pressing the valve body 24 toward the valve port 22a are incorporated.

  The relief valve 21 closes the oil discharge passage 20 when the oil pressure in the pressure chamber 15 is equal to or lower than the set pressure, and opens the oil discharge passage 20 when the pressure exceeds the set pressure.

  Between the housing 11 and the plunger 13, there is provided a backward movement restricting means 30 for preventing the plunger 13 from moving backward toward a closed end of the cylinder chamber 12 by a predetermined amount or more.

  As shown in FIG. 3, the backward movement restricting means 30 forms a ring accommodating groove 31 in the inner periphery of the opening of the cylinder chamber 12, and accommodates a register ring 32 that is elastically deformable in the radial direction in the ring accommodating groove 31. A plurality of circumferential grooves 33 tightened by the register ring 32 are provided at equal intervals in the axial direction on the outer periphery of the plunger 13, and a tapered surface having a smaller diameter toward the tip of the plunger 13 on the inner periphery of each circumferential groove 33. 33a and an engagement surface 33b extending radially outwardly from the small diameter end of the tapered surface 33a are provided.

  In the backward movement restricting means 30 configured as described above, when the plunger 13 moves outward by the pressing force of the return spring 14, the tapered surface 33a expands the diameter of the register ring 32. The plunger 13 moves outward due to the diameter expansion, and when a pushing force is applied to the plunger 13, the register ring 32 comes into contact with the rear wall 31 a of the ring receiving groove 31 and stops. The mating surface 33b is engaged and the plunger 13 is held in a stopped state.

  As shown in FIG. 2, a padding 40 is incorporated in the spring accommodating recess 18 formed in the plunger 13. The padding 40 has a columnar shape, and a flange 41 is provided on the outer periphery of the tip portion. The padding 40 is provided with an oil passage 42 penetrating from the front end surface to the rear end surface.

  The padding 40 is inserted into the end portion of the return spring 14, and the pressing force of the return spring 14 is applied to the flange 41 and pressed against the closed end surface of the spring accommodating recess 18.

  As shown in FIG. 4, the flange 41 of the padding 40 is formed with a cross groove-shaped discharge passage 43 that communicates the spring accommodating recess 18 and the valve accommodating recess 19 on the front end surface pressed against the closed end surface of the spring accommodating recess 18. ing. Instead of the flange 41, a discharge path 43 may be provided on the closed end face of the spring accommodating recess 18. Further, the discharge path 43 can take any shape other than the cross groove.

  In the assembled state of the auto tensioner 10 as shown in FIG. 1, when the chain 5 vibrates due to a change in angular velocity during one rotation of the crankshaft 1 or a torque fluctuation of the camshaft 3, When the return spring 14 is pressed, the plunger 13 moves outward (moves forward) to absorb the slack of the chain 5.

  When the plunger 13 moves forward, the register ring 32 is pushed by the taper surface 33a to increase the diameter, and therefore does not hinder the forward movement of the plunger 13. When the movement amount of the plunger 13 becomes larger than the pitch of the circumferential groove 33, the next circumferential groove 33 corresponds to the register ring 32, and the circumferential groove 33 is tightened by the register ring 32.

  On the other hand, when the chain 5 is tensioned, a pushing force is applied to the plunger 13 via the chain guide 6. At this time, when the pressure in the pressure chamber 15 rises and the pressure becomes higher than the supply pressure of oil supplied from the oil pump to the oil supply passage 16, the check valve 17 closes the oil supply passage 16 and is enclosed in the pressure chamber 15. The pushing force applied to the plunger 13 is buffered by the hydraulic damper action of the oil.

  When the pressure in the pressure chamber 15 exceeds the set pressure of the relief valve 21, the relief valve 21 opens the oil discharge passage 20, and the oil in the pressure chamber 15 is discharged from the oil discharge passage 20 to the outside. For this reason, the chain 5 is prevented from being over-tensioned.

  When the engine is stopped, the oil pump is also stopped, so that the supply of oil to the oil supply passage 16 is interrupted.

  Immediately after the engine is stopped, the pressure in the pressure chamber 15 is high, so the check valve 17 closes the oil supply passage 16, but the oil in the pressure chamber 15 is minutely formed on the sliding surfaces of the cylinder chamber 12 and the plunger 13. Since the pressure leaks to the outside through a small gap, the pressure in the pressure chamber 15 gradually decreases, and the check valve 17 opens the oil supply passage 16 due to the decrease in pressure.

  At this time, since the retracted position of the plunger 13 is restricted by the backward movement restricting means 30, only the amount of oil is reduced while the volume of the pressure chamber 15 is constant.

  For this reason, when the engine is started, since the discharge amount of the oil pump immediately after the start is small, it takes time until the pressure chamber 15 is filled with oil.

  However, as shown in the embodiment, by providing the padding 40 in the pressure chamber 15, the volume of the pressure chamber 15 can be reduced, so that the oil filling time for the pressure chamber 15 can be shortened. Can do.

  For this reason, when the engine is started, the pressure chamber 15 is immediately filled with oil, so that the hydraulic damper action is exhibited immediately after the engine is started, and it is possible to prevent the chain 5 from fluttering. .

  Further, the stuffing 40 is provided with a flange 41, and the stuffing 40 moves integrally with the plunger 13 by applying a pressing force of the return spring 14 to the flange 41 and pressing the stuffing 40 against the plunger 13.

  Therefore, there is no inconvenience that the stuffing 40 collides with the plunger 13 to generate an abnormal noise, and the stuffing 40 is incorporated in the end of the return spring 14 to prevent the return spring 14 from bending. In addition, since an unbalanced load is not applied to the plunger 13 from the return spring 14, the function of the hydraulic auto tensioner can be sufficiently exhibited.

  Further, since the discharge path 43 is formed on the front end surface of the flange 41 of the filling 40, the spring accommodating recess 18 and the valve accommodating recess 19 can be held in communication with each other via the discharge path 43. For this reason, as shown in FIG. 5, when the auto tensioner 10 is mounted in an upward posture with the plunger 13 as an upper portion, the air accumulated in the oil in the pressure chamber 15 when the relief valve 21 is opened is discharged to the outside. It is possible to suppress a decrease in the damper effect due to air compression.

Front view of a chain transmission device using a hydraulic auto tensioner according to the present invention 1 is a longitudinal front view of the hydraulic auto tensioner shown in FIG. Enlarged sectional view showing the backward movement restricting means 2 is a perspective view of the filling shown in FIG. Sectional view showing the state of use of the auto tensioner with the plunger at the top

Explanation of symbols

11 Housing 12 Cylinder chamber 13 Plunger 14 Return spring 15 Pressure chamber 16 Oil supply passage 18 Spring housing recess 19 Valve housing recess 20 Oil drain passage 40 Stuffing 41 Flange 43 Discharge passage

Claims (1)

A plunger is slidably incorporated in the cylinder chamber formed in the housing,
The plunger is formed with a spring accommodating recess from the rear end facing the pressure chamber formed on the back, a valve accommodating recess having a smaller diameter than the spring accommodating recess, and an oil discharge passage that opens at the distal end surface of the plunger. When a return spring is provided between the closed end of the spring accommodating recess and the closed end of the cylinder chamber to provide the plunger with outward protrusion, and when the pressure in the pressure chamber exceeds the set pressure in the valve accommodating recess A relief valve that releases the pressure in the pressure chamber to the outside from the oil discharge passage is built in, and an oil supply passage that communicates with the pressure chamber is formed in the housing, and oil is supplied to the pressure chamber from the oil supply passage to the plunger. In the auto tensioner designed to buffer the applied pushing force,
A cylindrical pad for reducing the volume in the pressure chamber is inserted into the end of the return spring on the plunger side, and a flange that is pressed against the closed end surface of the spring accommodating recess by receiving the spring force of the return spring is inserted into the front end of the pad. An auto-tensioner is provided, wherein a discharge passage is formed in at least one of a front end surface of the flange and a closed end surface of the spring housing recess to communicate the spring housing recess and the valve housing recess.

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