Chain tensioner

Abstract

The present invention provides a chain tensioner that automatically adjusts flow path resistance inside an oil leak path with a simple configuration to make it possible to reduce a change in damping characteristics resulting from a change in oil temperature and reduce an increase in manufacturing cost. In the chain tensioner, a pressure oil chamber is provided with an oil leak path communicating with an outside of the chain tensioner, the oil leak path contains a movable piece which is movable with a temperature-dependent deformation member that deforms according to oil temperature, and the movable piece is formed into a shape that changes flow path resistance of the oil leak path according to a position to which the movable piece is moved.

Claims

1. A chain tensioner comprising: a tensioner body having a cylindrical plunger accommodation hole and having an opening at one end; a cylindrical plunger slidably inserted into the plunger accommodation hole; and an urging unit flexibly accommodated in a pressure oil chamber formed by the plunger accommodation hole and the plunger and urging the plunger in a forward projection direction, wherein the pressure oil chamber is provided with an oil leak path communicating with an outside of the chain tensioner, the oil leak path contains a movable piece which is movable with a temperature-dependent deformation member that deforms according to oil temperature, and the movable piece is formed into a shape that changes flow path resistance of the oil leak path according to a position to which the movable piece is moved.

2. The chain tensioner according to claim 1, wherein the movable piece is accommodated to be slidable inside a movable piece passage hole provided to cross the oil leak path, and the temperature-dependent deformation member is inserted inside the movable piece passage hole on at least one side of the movable piece.

3. The chain tensioner according to claim 1, wherein the oil leak path is provided in the tensioner body and formed to communicate with the outside of the chain tensioner from the plunger accommodation hole.

4. The chain tensioner according to claim 1, wherein the oil leak path is provided on a forward side of the plunger and formed to communicate with the outside of the chain tensioner from an inside of the plunger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a front cross-sectional view of a chain tensioner 100 according to one embodiment of the present invention;

(2) FIG. 2 is an A-part enlarged view of the chain tensioner 100 according to one embodiment of the present invention;

(3) FIG. 3 is the A-part enlarged view showing a state in which a temperature-dependent deformation member 131 of the chain tensioner 100 according to one embodiment of the present invention operates;

(4) FIG. 4 is a front cross-sectional view of a chain tensioner 200 according to one embodiment of the present invention in which a variable leak-down mechanism 230 is provided in a plunger 220;

(5) FIG. 5 is a B-part enlarged view of the chain tensioner 200 according to one embodiment of the present invention;

(6) FIG. 6 is a B-part enlarged view of the chain tensioner 200 according to one embodiment of the present invention in which a temperature-dependent deformation member 231 operates;

(7) FIG. 7 is an explanatory view of a chain tensioner 500 used in the chain guide mechanism of an engine; and

(8) FIG. 8 is a schematic explanatory view of the conventional chain tensioner 500.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) Hereinafter, a chain tensioner 100 according to an embodiment of the present invention will be described based on the drawings.

(10) As shown in FIG. 1, a chain tensioner 100 includes: a tensioner body 110 having a cylindrical plunger accommodation hole 111 with its one end open; a cylindrical plunger 120 slidably inserted into the plunger accommodation hole 111; and a coil spring 140 flexibly accommodated in a pressure oil chamber 101 formed by the plunger accommodation hole 111 and the plunger 120 and urging the plunger 120 in a forward projection direction. An oil leak path 115 communicating with the outside of the chain tensioner 100 and an oil storage chamber 121 communicating with an oil supply hole 114 for supplying oil are connected to the pressure oil chamber 101. A movable piece passage hole 116 including a variable leak-down mechanism 130 is connected to the oil leak path 115 so as to cross the oil leak path 115.

(11) Since the oil leak path 115 is provided in the tensioner body 110 as described above, it is possible to simplify the device configuration of the chain tensioner 100 and replace or adjust a movable piece 133 or a temperature-dependent deformation member 131 even after the chain tensioner 100 is attached to an engine block.

(12) Between the pressure oil chamber 101 and the oil storage chamber 121, a check valve unit 150 preventing oil flowing into the pressure oil chamber 101 from flowing back to the oil storage chamber 121 is provided.

(13) The variable leak-down mechanism 130 is constituted by the movable piece 133, a movable spring 132 urging the movable piece 133 in the opening direction of the movable piece passage hole 116, the temperature-dependent deformation member 131 urging the movable piece 133 to the side of the movable spring 132, and a plug 136 blocking the movable piece passage hole 116. On the surface of the movable piece 133, a first leak groove 134 formed into a circumferential shape and a second leak groove 135 having a groove shape different from that of the first leak groove 134 are provided.

(14) Next, the operation of the variable leak-down mechanism 130 of the chain tensioner 100 will be described using FIGS. 2 and 3.

(15) First, by the damping of the plunger 120, oil is subjected to a force in a direction in which the oil is pushed out from the oil leak path 115 to the outside of the tensioner body 110.

(16) On this occasion, since the flow path of the oil leak path 115 is narrowed down by the first leak groove 134 of the movable piece 133, it is possible to adjust the leak amount of the oil and maintain proper damping characteristics.

(17) Here, when the viscosity of the oil changes with a change in oil temperature, the proper damping characteristics may not be obtained due to the excessive leak of the oil if the flow path inside the oil leak path 115 is narrowed down in the same manner as that before the oil temperature changes. However, the temperature-dependent deformation member 131 of the variable leak-down mechanism 130 extends to its prescribed length with a change in the oil temperature to push the movable piece 133 to the side of the movable spring 132, and the second leak groove 135 having a flow path narrower than that of the first leak groove 134 is moved to communicate with the oil leak path 115. In this manner, it is possible to reduce the leak amount of the oil and obtain the proper damping characteristics the same as that before the temperature changes.

(18) Note that when the oil temperature returns to its initial temperature, the temperature-dependent deformation member 131 also contracts to its initial length. In addition, since the movable piece 133 is urged to the side of the temperature-dependent deformation member 131 by the movable spring 132, the movable piece 133 returns to its initial position to make the first leak groove 134 communicate with the oil leak path 115 again.

(19) Further, since the use of a plurality of temperature-dependent deformation members each having a different deformation temperature allows leak grooves at three or more positions to be automatically selected according to the oil temperature with a simple configuration, it is possible to further prevent a change in the damping characteristics.

(20) Next, a chain tensioner 200 according to another embodiment of the present invention will be described based on the drawings.

(21) As shown in FIG. 4, a chain tensioner 200 includes: a tensioner body 210 having a cylindrical plunger accommodation hole 211 with its one end open; a cylindrical plunger 220 slidably inserted into the plunger accommodation hole 211; and a coil spring 240 flexibly accommodated in a pressure oil chamber 201 formed by the plunger accommodation hole 211 and the plunger 220 and urging the plunger 220 in a forward projection direction. An oil leak path 215 provided on the side of the tip end of the plunger 220 and communicating with the outside of the chain tensioner 200 and an oil storage chamber 221 communicating with an oil supply hole 214 for supplying oil are connected to the pressure oil chamber 201. A movable piece passage hole 216 including a variable leak-down mechanism 230 is connected to the oil leak path 215 so as to cross the oil leak path 215.

(22) Since the oil leak path 215 is provided on the side of the tip end of the plunger 220 in the chain tensioner 200 as described above, it is possible to further miniaturize the tensioner body 210 and facilitate the provision of the chain tensioner 200 in narrow space.

(23) Between the pressure oil chamber 201 and the oil storage chamber 221, a check valve unit 250 preventing oil flowing into the pressure oil chamber 201 from flowing back to the oil storage chamber 221 is provided.

(24) The variable leak-down mechanism 230 is constituted by a movable piece 233, a movable spring 232 urging the movable piece 233 in the opening direction of a movable piece passage hole 216, a temperature-dependent deformation member 231 urging the movable piece 233 to the side of the movable spring 232, and a plug 236 blocking the movable piece passage hole 216. On the surface of the movable piece 233, a first leak groove 234 formed into a circumferential shape and a second leak groove 235 having a groove shape different from that of the first leak groove 234 are provided.

(25) Next, the operation of the variable leak-down mechanism 230 of the chain tensioner 200 will be described using FIGS. 5 and 6.

(26) First, by the damping of the plunger 220, oil is subjected to a force in a direction in which the oil is pushed out from the oil leak path 215 to the outside of the plunger 220.

(27) On this occasion, since the flow path of the oil leak path 215 is narrowed down by the first leak groove 234 of the movable piece 233, it is possible to adjust the leak amount of the oil and maintain proper damping characteristics.

(28) Here, when the viscosity of the oil changes with a change in oil temperature, the proper damping characteristics may not be obtained due to the excessive leak of the oil if the flow path inside the oil leak path 215 is narrowed down in the same manner as that before the oil temperature changes. However, the temperature-dependent deformation member 231 of the variable leak-down mechanism 230 extends to its prescribed length with a change in the oil temperature to push the movable piece 233 to the side of the movable spring 232, and that the second leak groove 235 having a flow path narrower than that of the first leak groove 234 is moved to communicate with the oil leak path 215. In this manner, it is possible to reduce the leak amount of the oil and obtain the proper damping characteristics the same as that before the temperature changes.

(29) Note that the oil leaks from the side of the tip end of the plunger 220 in the chain tensioner 200. Therefore, it is possible to directly add the oil leaking from the plunger 220 to the side of a shoe and effectively use the same to smoothen a chain.

(30) The embodiments of the present invention are described above. The present invention is not limited to the above embodiments, but various design modifications may be made without departing from the scope of the present invention described in claims.

(31) It is described in the above embodiments that the movable piece passage hole including the variable leak-down mechanism is connected to the oil leak path so as to cross the oil leak path. However, a method for providing the variable leak-down mechanism is not limited to this. For example, the variable leak-down mechanism may be provided so as to be contained in the oil leak path, or the movable leak-down mechanism may be connected to the exit of the oil leak path.

(32) Further, it is described in the above embodiments that the variable leak-down mechanism is constituted by the movable piece, the movable spring urging the movable piece in the opening direction of the movable piece passage hole, the temperature-dependent deformation member urging the movable piece to the side of the movable spring, and the plug blocking the movable piece passage hole. However, the configuration of the variable leak-down mechanism is not limited to this. For example, the temperature-dependent deformation members each having different deformation temperature may be provided on both sides in the advancing/retracting direction of the movable piece without the provision of the movable spring, or the temperature-dependent deformation member may be provided on one side besides the movable spring provided in the advancing/retracting direction of the movable piece.

(33) Further, it is described in the above embodiments that the first leak groove formed into a circumferential shape and the second leak groove having a groove shape different from that of the first leak groove are provided on the surface of the movable piece, and that the leak grooves communicating with the oil leak path are changed to adjust the leak amount of the oil when the position of the movable piece changes with a change in oil temperature. However, a method for adjusting the leak amount of the oil is not limited to this. For example, the first leak groove and the second leak groove may simultaneously communicate with the oil leak path to adjust the leak amount of the oil according to a change in oil temperature, or one wide leak groove may be provided to adjust the width of a mouth where the oil leak path and the leak groove communicate with each other according to a change in oil temperature.

(34) Further, it is described in the above embodiments that the leak grooves are formed into a circumferential shape on the surface of the movable piece. However, a method for forming the leak grooves is not limited to this. For example, an oil leak hole penetrating the movable piece may be provided, or linear leak grooves communicating with the oil leak path may be provided on both end surfaces in the advancing/retracting direction of the movable piece.