JPH0586057U - Tensioner with lock mechanism that is released by external hydraulic pressure - Google Patents

Abstract

(57) [Summary] [Purpose] In a tensioner that slidably inserts into a housing to form an oil chamber between the housing and a tensioner that causes a projection output by a spring and external oil pressure to act. When there is not, the lock mechanism that prevents the plunger from retracting is released by external hydraulic pressure without causing oil leakage or air inclusion. [Structure] The tensioner 10 includes a housing 12 and a plunger 14 that forms an oil chamber 16 between the housing 12 and the housing 12. External oil pressure generated in the engine or the like acts on the oil chamber 16. The plunger 14 receives an external hydraulic pressure and a thrust output by the spring 18. Tensioner 10
Further has a piston 22 that forms a sub oil chamber 20 with the housing 12, and a second spring 34 that urges the piston 22 toward the sub oil chamber 20. External oil pressure acts on the sub oil chamber 20. And the plunger 14
Has a rack 38 in a portion surrounded by the housing 12, and a piston 22 extends through the wall of the housing 12 and has a meshing tooth 36 at the tip thereof which can mesh with the rack 38.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a tensioner having a lock mechanism that is released by external hydraulic pressure.

[0002]

[Prior Art]

 There are various tensioners. Among tensioners, there is a tensioner that uses an external hydraulic pressure generated by an engine or the like to apply tension to a chain or belt that drives the camshaft or the like of the engine. This type of tensioner is described in Japanese Utility Model Laid-Open No. 63-57852 as shown in FIG. 4, Japanese Utility Model Laid-Open No. 11-11855 as shown in FIG. 5, and Japanese Utility Model Laid-Open No. 1-229152 as shown in FIG. There is.

Each of the tensioners 50, 60, 70 has a lock mechanism 54, 64, 74 for preventing the plungers 52, 62, 72 from retracting when the external hydraulic pressure disappears. The lock mechanisms 54, 64, 74 are configured to be forcibly released by the hydraulic pressure when the external hydraulic pressure acts on the tensioners 50, 60, 70.

[0004]

[Problems to be solved by the device]

 The tensioners 50 and 60 shown in FIGS. 4 and 5 are of a type in which rotatable ratchets 58 and 68 mesh with racks 56 and 66 formed on plungers 52 and 62, respectively. Therefore, even if the external hydraulic pressure is applied, the ratchets 58 and 68 cannot be rotated and the locking mechanisms 54 and 64 are not released until the plungers 52 and 62 have moved forward by a certain degree. In the worst case, the ratchets 58 and 68 may be damaged.

In the tensioner 70 shown in FIG. 6, the lock mechanism 74 is released even if the plunger 72 does not advance to a certain extent like the former two. Therefore, the plunger 72 can be freely moved back and forth immediately after the engine is started so as to respond to the tension of the chain or the belt, and the plunger 72 is not overloaded. However, the hydraulic pressure for operating the lock mechanism 74 and the hydraulic pressure for operating the plunger 72 are hydraulic pressures that act on the same oil chamber 76, and either of them cannot be operated independently. Further, there is a problem in that oil leakage and air suction are likely to occur at the portion where the lock mechanism 74 is provided, and the damper function of the tensioner is deteriorated.

[0006]

[Means for Solving the Problems]

 The present invention is a tensioner in which a spring and external pressure are applied to a plunger that is slidably inserted into a housing and forms an oil chamber between the housing and the plunger, which is slidable on the housing. A piston that is inserted into the auxiliary oil chamber to form an auxiliary oil chamber with the housing, an oil passage for applying the external hydraulic pressure to the auxiliary oil chamber, and a piston that biases the piston toward the auxiliary oil chamber. Two springs, the plunger has a rack in a portion surrounded by the housing, and the piston extends through a wall of the housing and has a meshing tooth at a tip end thereof capable of meshing with the rack. The above problem was solved by the tensioner.

[0007]

[Action]

 When the engine starts, external hydraulic pressure is generated, and the external hydraulic pressure acts on the oil chamber and the sub oil chamber. When the external hydraulic pressure rises, the rack and the meshing teeth are unlocked, and proper tension is applied to the chain and belt.

During operation of the tensioner, the piston receives the hydraulic pressure from the sub oil chamber, so that the meshing teeth with the rack are released. However, oil leakage may occur between the housing and the piston.

Therefore, on the opposite side of the sub oil chamber, an atmospheric chamber defined by the housing and the piston and a hole for communicating the atmospheric chamber with the outside are provided, and the external hydraulic pressure acts on the sub oil chamber. If the tensioner is configured so that the hole is closed when the piston moves against the biasing force of the second spring, even if oil leaks to the atmosphere chamber, the oil leaks from the entire tensioner. It is possible to prevent the hydraulic pressure in the oil chamber from dropping and to effectively use the external hydraulic pressure.

[0010]

【Example】

 FIG. 1 shows a sectional view of a tensioner according to the present invention. The tensioner 10 uses external hydraulic pressure. The tensioner 10 has a housing 12 and a plunger 14 slidably fitted in the housing 12. The oil chamber 16 is formed by the housing 12 and the plunger 14. The plunger 14 is provided with a thrust force by the spring 18 and the external hydraulic pressure.

The tensioner 10 has a sub oil chamber 20 formed integrally with the housing 12. The sub oil chamber 20 is defined by a housing 12 and a piston 22 slidably fitted in the housing 12. The piston 22 has a rod 24 and a bush 26. The inside of the bush 26 is the sub oil chamber 20, and the outside of the bush 26 is the atmosphere chamber 28. A cap 30 is fitted in the housing 12 in the atmosphere chamber 28. The cap 30 has a hole 32 that communicates with the outside. A second spring 34 is provided between the cap 30 and the bush 26. The second spring 34 urges the piston 22 toward the sub oil chamber 20. The sub oil chamber 20, the piston 22, and the second spring 34 described above constitute a lock mechanism.

The rod 24 can move back and forth toward the plunger 14 through a part of the wall of the housing 12. A meshing tooth 36 is formed at the tip. The plunger 14 is surrounded by the housing 12 and has a rack 38 corresponding to the meshing tooth 36 of the rod 24. The meshing teeth 36 and the rack 38 allow the plunger 14 to move forward and prevent the plunger 14 from moving backward, so that the meshing teeth 36 and the rack 38 are straight in the advancing and retracting direction of the plunger 14 and the valleys of the rack 38 to the peaks of the rack 38. The plunger 14 has a surface inclined in the backward direction.

The housing 12 has an oil sump 40. The oil sump 40 and the oil chamber 16 communicate with each other via a check valve 42. The oil sump 40 and the sub oil chamber 20 communicate with each other via an oil passage 44. The check valve 42 has a ball seat 46. The ball seat 46 has an oil passage 48 that connects the oil sump 40 and the oil chamber 16. The cross-sectional area of the oil passage 44 that connects the oil sump 40 and the sub oil chamber 20 is smaller than the cross-sectional area of the oil passage 48 of the ball seat 46.

FIG. 3 shows a mounting example of the tensioner 10. External hydraulic pressure normally occurs in the engine E to which the tensioner 10 should be equipped. The external hydraulic pressure is zero when the engine is stopped. Therefore, as shown in FIG. 1, since the meshing teeth 36 and the rack 38 are meshed with each other, the plunger 14 cannot move backward.

When the engine E is started, external hydraulic pressure is generated. Oil pressure acts on the oil chamber 16 and the sub oil chamber 20 through the oil sump 40 and the oil passages 44 and 48. Due to the difference in cross-sectional area, the external hydraulic pressure first acts on the oil chamber 16 and then on the auxiliary oil chamber 20 with a slight delay.

The tension of the chain C acts on the tip of the plunger 14 in the backward direction. When the external hydraulic pressure gradually rises, the meshing teeth 36 and the rack 38 are unlocked. The plunger 14 can freely move back and forth according to the tension of the chain C.

FIG. 2 shows the tensioner 10 when the external hydraulic pressure is operating normally. The piston 22 receives hydraulic pressure from the sub oil chamber 20, and the rod 24 closes the hole 32. In this way, the piston 22 functions as a check valve. The oil in the sub oil chamber 20 slightly leaks to the atmosphere chamber 28 through the space between the rod 24 and the wall of the housing 12. In addition, a small amount leaks to a portion where the rack 38 is formed through between the bush 26 and the housing 12.

Since the hole 32 is closed by the rod 24 in the atmosphere chamber 28, a certain amount of oil does not flow in. Therefore, no loss occurs in the external hydraulic pressure that acts on the oil chamber 16.

The oil leaked to the rack 38 through the auxiliary oil chamber 20 is supplied between the housing 12 and the plunger 14. Therefore, oil leakage and air suction between the housing 12 and the plunger 14 are prevented.

When the engine E stops and the external hydraulic pressure disappears, the oil decreases in the sub oil chamber 20 where the check valve 42 is not provided. The second spring 34 biases the piston 22 so that the meshing teeth 36 mesh with the rack 38. After that, even if the oil pressure in the oil chamber 16 drops, the plunger 14 cannot move backward.

In this embodiment, the external hydraulic pressure is supplied to the oil chamber 16 and the sub oil chamber 20 via the oil sump 40. However, the hydraulic pressure to the sub oil chamber 20 can be controlled by acting via a solenoid valve or from a separate external hydraulic source.

[0022]

[Effect of the device]

 In the present invention, the plunger is not configured to retract when there is no external hydraulic pressure, and of course, in constructing such a tensioner, oil leakage from the oil chamber and suction of air into the oil chamber are prevented. Can be prevented.

That is, in the present invention, the rack of the plunger is formed in the portion surrounded by the housing, and the meshing teeth formed at the tip of the piston penetrating the housing wall mesh with the rack. The oil in the secondary oil chamber leaks, but a part of the oil reaches the rack of the plunger through the space between the housing wall and the piston. Since oil is supplied to the sub-oil chamber where the rack is formed, it is possible to prevent oil leakage and air suction between the housing and the plunger.

Further, since the oil passage communicating with the oil chamber and the sub oil chamber is separately provided, the hydraulic pressure for releasing the lock can be adjusted separately from the hydraulic pressure acting on the oil chamber. For example, by making the cross-sectional areas of the oil passages different, it is possible to delay the propagation of the hydraulic pressure acting on the sub oil chamber and prevent the lock from being released immediately after the external hydraulic pressure is generated.

In the tensioner of the second aspect, the piston closes the hole during the normal operation, and the atmosphere chamber becomes a substantially closed chamber. Therefore, oil leakage from the sub oil chamber to the atmosphere chamber does not occur for a certain amount or more, and the external hydraulic pressure can be effectively applied to the oil chamber.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a tensioner according to the present invention, showing a state before an external hydraulic pressure is applied.

2 is a cross-sectional view of the tensioner of FIG. 1 when an external hydraulic pressure is applied.

3 is an explanatory view showing an example of mounting the tensioner of FIG.

FIG. 4 is a sectional view of a conventional tensioner.

FIG. 5 is a sectional view of a conventional tensioner.

FIG. 6 is a sectional view of a conventional tensioner.

[Explanation of symbols]

 10 Tensioner 12 Housing 14 Plunger 16 Oil Chamber 18 Spring 20 Sub Oil Chamber (Lock Mechanism) 22 Piston (Lock Mechanism) 24 Rod 26 Bush 28 Atmosphere Chamber 32 Hole 34 Second Spring (Lock Mechanism) 36 Meshing Teeth 38 Rack 44 Oil Road 48 Oilway

Claims (2)

[Scope of utility model registration request] 1. A tensioner in which a spring and external force are applied to a plunger that is slidably inserted in a housing and forms an oil chamber between the housing and the plunger, which is slidable in the housing. A piston that is inserted into the auxiliary oil chamber to form an auxiliary oil chamber with the housing, an oil passage for applying the external hydraulic pressure to the auxiliary oil chamber, and a piston that biases the piston toward the auxiliary oil chamber. Two springs, the plunger has a rack at a portion surrounded by the housing, and the piston extends through a wall of the housing and has at its tip a meshing tooth capable of meshing with the rack. Tensioner characterized by. 2. The sub-oil chamber has an atmosphere chamber defined by the housing and the piston on the side opposite to the sub-oil chamber, and a hole for communicating the atmosphere chamber with the outside. The tensioner according to claim 1, wherein the hole is closed when the piston moves and moves against the biasing force of the second spring.