JPH062067Y2 - Timing chain tension adjustment device - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention relates to a tension adjusting device for a timing chain, and more specifically, to prevent an excessive tension from being applied to the timing chain due to thermal expansion of a cylinder block or a cylinder head. The present invention relates to a tension adjusting device for a timing chain.

(Prior Art) A cam shaft for operating a valve mechanism of an engine is configured to obtain a rotational driving force from a crank shaft via a transmission means such as a chain. The cam shaft is pivotally supported by the cylinder head, and the distance from the crank shaft pivotally supported at the lower part of the cylinder block is considerably large. Therefore, when the chain is used as the transmission means, the tension adjusting device is used so that the driving force is always transmitted at an accurate timing even when the vehicle shakes or the load changes. For example, Japanese Utility Model Laid-Open No. 57-71834 discloses a tension adjusting device which applies a tension to a timing chain via a shoe by pushing a rod inserted into a hole provided in a vehicle body with a spring force. Then, a chain tensioner releasing device for an engine is described in which a ratchet that locks the rod can be released from the outside. This ratchet is arranged on the surface of the rod, engages with a lever pivotally supported by the vehicle body, locks the rod in the return direction, and the lever faces the gear cover body held by the vehicle body. The ratchet can be released by providing a screw hole and applying a screw from the outside of the cover body to rotate the lever.

(Problems to be solved by the invention) Recently, in order to reduce the weight of the engine, a metal material having a relatively large coefficient of thermal expansion such as an aluminum alloy has been used for the cylinder head and the cylinder block. . Therefore, when the engine is heated under high load or the like, due to the thermal expansion of the engine, the axial distance becomes large and the timing chain may be excessively strained. If such tension increases, the lock mechanism that adjusts the tension of the chain may be damaged. The conventional locking mechanism, as shown in the above example, can be released during maintenance and inspection, but it automatically locks in response to changes in the tension of the timing chain during engine operation. It is not something that can be released.

The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a tension adjusting device for a timing chain in which excessive tension is not applied to the timing chain due to thermal expansion of the cylinder block or the cylinder head.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the invention described in the scope of utility model registration claims is a main body in which a first cylinder is formed inside an engine, and a first cylinder of the main body. A plunger slidably inserted into one cylinder to urge the timing chain in its tension direction, an oil supply passage for supplying engine oil in the engine to a hydraulic chamber between the main body and the plunger, and a spring. It is premised that a stopper is provided by which the plunger is engaged by the urging force to prevent the plunger from moving in the direction of loosening the timing chain, and a releasing means for releasing the engagement of the stopper. In this structure, the releasing means is composed of a second cylinder formed in the main body, and a piston slidably held by the second cylinder and having a tip of a piston rod connected to the stopper. Then, the piston is arranged so as to operate in a direction in which the stopper is engaged and disengaged. In addition, the hydraulic chamber of the second cylinder, which is the chamber on the side where the piston is actuated in the stopper releasing direction by the supply of the pressure oil, communicates with the hydraulic chamber of the first cylinder and the other side of the second cylinder. The chamber is configured to communicate with the atmosphere.

(Operation) According to the above configuration, when the engine speed increases and the oil pressure of the engine oil increases and changes, the applied pressure is transmitted to the hydraulic chamber of the first cylinder through the oil supply passage. It is transmitted to the hydraulic chamber on one side of the second cylinder which is in communication. When the pressing force exceeds the engagement biasing force of the stopper, the other chamber is communicated with the atmosphere, so that the pressure oil is transferred from the hydraulic chamber of the first cylinder to the hydraulic chamber of one side of the second cylinder. Is supplied to actuate the piston and disengage the stopper from the plunger. Therefore, the plunger can be moved to the loosening side of the timing chain, the equilibrium is maintained at the position balanced with the hydraulic pressure, and the tension of the timing chain is moderately moderated and adjusted. As a result, excessive tension is prevented from being generated in the timing chain due to thermal expansion of the cylinder block or the like that constitutes the engine.

Further, when the hydraulic pressure decreases, pressure oil is discharged from the hydraulic chamber on one side of the second cylinder by the engaging biasing force of the stopper, and the piston is reversely operated, contrary to the above.
As a result, the stopper engages with the plunger, the movement of the plunger toward the loosening side of the timing chain is blocked, and the tension corresponding to the position of the plunger is applied to the timing chain.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

The tension adjusting device of the timing chain of the present invention is operated by the hydraulic pressure of the engine oil supplied from the oil pump so that excessive tension is not applied to the chain due to thermal expansion of the cylinder block or cylinder head that constitutes the engine. It is configured as follows.

As shown in FIGS. 1 to 3, the plunger 2 that strokes by the hydraulic pressure of the engine oil to apply tension to the timing chain 1 and the stopper 3 that restricts the backward stroke of the plunger 2 adjust the tension of the timing chain. It is provided in the device 4. A releasing means 5 is provided for releasing the operation of the stopper 3 when the hydraulic pressure reaches a predetermined value or more.

Crank pulley 7 provided under the cylinder block 6
And the cam pulley 9 provided on the cylinder head 8, the timing chain 1 is provided with a shoe 10 which has one end pivotally supported by the cylinder block 6 and the other end swingable with respect to the timing chain 1. Through the tension adjusting device 4
The tension is adjusted by.

The tension adjusting device 4 is fixed to the cylinder block 6. A first cylinder 11 is formed in a main body 4a of the tension adjusting device 4, and a plunger 2 is slidably fitted and inserted in the first cylinder 11.
Is in contact with the shoe 10 and moves back and forth in a direction substantially orthogonal thereto. And the plunger 2
Is the timing due to the oil pressure of the engine oil supplied into the hydraulic chamber 11b of the first cylinder 11 from the oil supply hole 11a as an oil supply passage communicating with an oil passage (not shown) in the cylinder block 6 and the urging force of the spring 12. Outward direction that gives tension to the chain 1 (first
It is designed to be biased to the right of the figure).

On the upper part of the first cylinder 11, a releasing means 5 for releasing the operation of the stopper 3 is provided. This release means 5
Is composed of a small cylinder 13 as a second cylinder and a piston 14 slidably held by the small cylinder 13. A primary chamber 15 defined as one hydraulic chamber defined by the piston 14 is communicated with the hydraulic chamber 11b of the first cylinder 11 by an oil hole 16, while a secondary chamber defined as the other hydraulic chamber is formed on the other side of the small cylinder 13. Next room 17
Is opened to the atmosphere by the through hole 18.

The piston rod 19 of the piston 14 projects outward (to the right in FIG. 1), and its tip is movably supported by the upper end of a stopper 3 that restricts the backward movement of the plunger 2, and is urged outward by a spring 21. Has been done.

At the lower end of the stopper 3, a claw 23 that engages with a retaining groove 22 formed at the upper portion of the plunger 2 is formed.
A central portion is pivotally supported by a support shaft 25 fixed to a, and the stopper 3 is rotated clockwise or counterclockwise (see FIG. 3) by pushing and pulling the rod 19. Incidentally, the claw 23 of the stopper 3 and the hooking groove 22 of the plunger 2 are formed so as to restrict the retreat of the plunger 2 at the time of engagement and allow the plunger 2 to advance. In the figure, 26 is a plug that closes the secondary chamber 17.

In the timing chain tension adjusting device 4 as described above, the tension of the timing chain 1 is given solely by the elastic force of the spring 12 when the pressure of the engine oil is low at the initial stage of engine startup. Then, at the balance position, the stopper 3 is urged clockwise by the urging force of the spring 21, so that as shown in FIG.
The claw 23 engages with the retaining groove 22 of the plunger 3, and the plunger 3 is retained at that position to restrict the backward movement. Therefore, the tension of the timing chain 1 is properly maintained without change due to fluctuations and load fluctuations, so that noise is not generated and the valve opening / closing timing is not modulated.

When the engine speed rises, the supply of engine oil becomes high, and the oil pressure in the first cylinder 11 becomes high, the oil flows into the small cylinder 13 via the oil hole 16, and the pressure in the primary chamber 15 increases. Is increased. Then, the piston 14 resists the biasing force of the spring 21 and the secondary chamber 17
Side, the stopper 3 is rotated counterclockwise, and the third
As shown in the drawing, the claw 23 has a hook groove 2 of the plunger 2.
2, the plunger 2 is allowed to retreat and advance. That is, the engagement of the stopper 3 is released by the increase variation of the oil pressure of the engine oil which exceeds the urging force of the spring 21 in the engagement direction. After that, the hydraulic pressure mainly acts on the plunger 2,
Even if the tension of the timing chain 1 fluctuates, the plunger 2 always automatically follows the balance position. Therefore, even if the distance between the crank shaft and the cam shaft increases due to the thermal expansion of the cylinder lock 6 and the cylinder head 8, the timing chain 1 is not excessively tensioned.

On the other hand, when the engine becomes low-speed and the supply amount of engine oil decreases, the hydraulic pressure in the primary chamber 15 of the small cylinder 13 decreases, and the spring 21 biases the pawls of the stopper 3 as shown in FIG. 23 engages with the hook groove 22,
Retraction of plunger 2 is restricted, timing chain 1
Tension is maintained. Then, when the temperature of the cylinder block 6 and the cylinder head 8 decreases, the axial distance between the cam shaft and the crank shaft shortens, and the tension of the timing chain 1 decreases, the plunger 2 is mainly biased to move the plunger 2 to the balanced position. Advance to. At that position, stopper 3
The claw 23 is engaged with the retaining groove 22 and returns to the original state.

As described above, according to the tension adjusting device for a timing chain of the present invention, it is possible to automatically apply an appropriate tension to the timing chain according to the operating state of the engine, so that the device is not overpowered and durable. Is improved and maintenance-free can be achieved.

(Effect of the Invention) As described above, according to the tension adjusting device for a timing chain of the present invention, when the engine speed increases and the oil pressure of the engine oil increases and fluctuates, the applied pressure is applied to the oil supply passage and the It is transmitted to the hydraulic chamber on one side of the second cylinder via the hydraulic chamber of one cylinder, and due to this pressure,
Since the piston is actuated and the stopper is disengaged from the plunger, the plunger can be moved to the loose side of the timing chain, and the thermal expansion of the cylinder block that constitutes the engine causes excessive movement of the timing chain. It is possible to prevent the tension from being generated.
Moreover, since the plunger is kept in equilibrium at a position that balances the hydraulic pressure, the tension of the timing chain can be moderately adjusted.

Moreover, when the hydraulic pressure decreases, pressure oil is discharged from the hydraulic chamber on one side of the second cylinder by the biasing force of the engagement side of the stopper and the piston is reversely operated, so that the stopper is automatically operated as the plunger. It can be engaged and a predetermined tension can be applied to the timing chain.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a tension adjusting device for a timing chain according to the present invention, FIG. 2 is a front view showing a state where the tension of the timing chain is adjusted by the tension adjusting device, and FIG. 3 is a stopper by a releasing means. It is sectional drawing which shows the state which was released. DESCRIPTION OF SYMBOLS 1 ... Timing chain, 2 ... Plunger, 3 ... Stopper, 4 ... Tension adjusting device, 5 ... Release means, 11 ... 1st cylinder, 11a ... Oil supply port (oil supply passage), 11
b ... hydraulic chamber of first cylinder, 13 ... small cylinder (second cylinder), 14 ... piston, 15 ... primary chamber (hydraulic chamber of second cylinder), 17 ... secondary chamber (chamber on the other side), 19 ... Piston rod.

Claims (1)

[Scope of utility model registration request] 1. A main body mounted on an engine and having a first cylinder formed therein, a plunger slidably inserted into the first cylinder of the main body to urge the timing chain in its tension direction, and An oil supply passage for supplying engine oil in the engine to the hydraulic chamber between the main body and the plunger, and a stopper that engages with the plunger by the urging force of the spring and prevents the plunger from moving in the direction of loosening the timing chain. And a releasing means for releasing the engagement of the stopper, the tension adjusting device for the timing chain, wherein the releasing means is slidably held by the second cylinder formed in the body and the second cylinder. And the piston rod has a tip connected to the stopper, and the piston disengages the stopper. The hydraulic chamber of the second cylinder, which is a chamber on the side of operating the piston in the stopper release actuating direction by the supply of pressure oil, while being arranged to operate in the direction described above, communicates with the hydraulic chamber of the first cylinder, and A tension adjusting device for a timing chain, wherein the chamber on the other side of the second cylinder is in communication with the atmosphere.