JP3346963B2 - Timing chain plunger mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a timing chain plunger mechanism for pressing a timing chain in an automobile engine such that the timing chain can backlash.

[0002]

2. Description of the Related Art Conventionally, in an engine using a timing chain between a crankshaft and a camshaft, an appropriate pressing force is applied to the timing chain via a tension arm, and the timing chain changes even when the timing chain is extended. A ratchet-type plunger mechanism is used to keep the expansion / contraction state of the timing chain when the distance between the crankshaft and the camshaft changes due to heat to a set constant state. In an engine employing such a timing chain, noise may be generated by colliding with the tension arm or excessive friction due to slack or excessive tension of the timing chain. In order to reduce such noise, a backlash is applied to the plunger mechanism so that the tension arm always slides on the timing chain with a predetermined pressing force.

As a plunger mechanism for such a timing chain, for example, as disclosed in Japanese Patent Application Laid-Open No. Sho. A cam having a non-return tooth and an auxiliary tooth for releasing engagement of the non-return tooth formed on a lower edge urged in a direction opposite to the above is rotatably mounted, and the non-return tooth is engaged with the rack. There has been known a configuration in which the protrusion of the piston is prohibited, and a predetermined amount of backlash occurs when the piston moves one pitch of the cam. In this case, the auxiliary teeth are lightly engaged with the rack while the check teeth are engaged with the rack.

[0004]

By the way, as described above, when the non-return teeth are engaged with the rack and the auxiliary teeth are pushed by the rack, a so-called half-back mechanism, the non-return teeth and the rack are connected to each other. In the type where the engagement of
The backlash amount is determined to be 1 to 2 times (x to 2x) the rack pitch x of the piston. here,
The amount of backlash is defined as the maximum amount of movement until the piston protrudes due to a drop in the tension of the timing chain and disengages the auxiliary teeth from the rack, and the piston is returned by backlash due to backlash, and the non-return teeth move back into the rack. It is the return amount until the engagement.

However, depending on the engine, the timing chain layout is different,
The above-mentioned x to 2x may not always be required as the backlash amount. That is, depending on the shape of the engine, the distance between the crankshaft and the camshaft, etc., the amount of backlash that can reliably suppress noise generation is, for example, x to 1.
It may be 5x. In such a case, in the above-mentioned case, the backlash amount can be set only at an integral multiple of the rack pitch x, so that it may be difficult to realize even if the rack pitch is reduced. As a result, there is a case where the tension of the timing chain is inappropriate and the noise increases.

An object of the present invention is to solve such a problem.

[0007]

In order to achieve the above object, the present invention takes the following measures. That is, the timing chain plunger mechanism according to the present invention includes a pressing member having a rack portion biased in a direction in which the tension of the timing chain for transmitting the driving force of the engine crankshaft to the camshaft is increased. A timing chain comprising a rotatable cam member urged in a direction opposite to the urging direction of the pressing member so as to engage with the rack portion and prohibit movement of the pressing member in the urging direction. A timing chain plunger mechanism that adjusts the tension of the pressing chain with a predetermined amount of backlash so that the tension of the pressing member is substantially constant. A non-return tooth that prohibits the movement of the non-return tooth, and is formed at a position separated from the non-return tooth by a predetermined distance in the urging direction and engages with the rack part when the pressing member moves in the urging direction. Engage with non-return tooth It was and a removal aid teeth, and sets the position offset in the check tooth side from the auxiliary teeth at least biasing direction the rotation center of the cam member.

With such a configuration, when the tension of the timing chain decreases from the state where the check teeth of the cam are engaged with the rack portion of the pressing member, the pressing member moves in the biasing direction, The rack pushes the auxiliary teeth in the urging direction, and the cam rotates. In this case, since the center of rotation of the cam is set at a position deviated to the check tooth side in front of the auxiliary tooth in the linear direction connecting the check tooth and the auxiliary tooth, the engagement between the auxiliary tooth and the rack portion is set. In this case, the rotation center is located just above the auxiliary teeth,
When the engagement between the auxiliary teeth and the rack portion is released and the non-return tooth newly engages with the rack portion, the amount of return of the pressing member in the counter-biasing direction increases when the non-return tooth engages with the rack portion. That is, the radius of rotation of the cam is longer than in the case where the center of rotation of the cam is located directly above the auxiliary teeth, and the auxiliary teeth start to rotate from a position behind the center of rotation, and the rotation radius is longer by the length of the rotation radius. Rotate up to. Therefore, the distance from the position where the engagement of the auxiliary teeth is released to the position where the check tooth newly engages with the rack portion, that is, the position after the backlash, is increased by the length of the turning radius.

Therefore, by setting the position of the center of rotation of the cam at a position deviated in the direction of the non-return tooth from just above the auxiliary tooth, the radius of rotation is adjusted, and the distance to the position after the backlash is set for each engine. Can be set to the required value. As a result, the timing chain does not become loose or conversely excessively strong, so that generation of friction noise and collision noise can be prevented, and such noise reduction of the engine can be realized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

An engine 100 whose main part is shown in FIG. 1 is for an automobile, and is an overhead camshaft type in which a camshaft 1 is driven to rotate by a timing chain 2. The timing chain 2 includes a camshaft 1 and a crankshaft 3
And a predetermined tension is applied by the tension arm 4 which always slides. The tension arm 4 includes a chain tensioner 5 serving as a plunger mechanism.
, So that there is no gap between the chain and the timing chain 2.

The chain tensioner 5 includes a casing 51
A piston 52 as a pressing member and a cam member 53 for controlling the movement of the piston 52 are incorporated therein. The chain tensioner 5 is the timing chain 2
Presses the tension arm 4 so as to operate with a predetermined tension. However, in the relationship between the rack portion 52a and the cam member 53 described later, the tension of the timing chain 2 fluctuates within a set range. Following this, the tension arm 4 is always pressed so as not to separate from the timing chain 2.

The piston 52 is formed of a rod, and its tip is in contact with the tension arm 4.
Biased in a direction to protrude therefrom. As a means for urging the piston 52, a compression spring or a hydraulic pressure may be employed. On the upper surface of the piston 52, a rack portion 52a that engages with a cam member 53 described later is formed. The rack portion 52a is provided with teeth at a pitch of 1 mm, for example, and its length is set according to the expected slack amount of the timing chain 2. The tooth shape of the rack part 52a is
It has the shape of an isosceles triangle. The configuration of the piston 52 may be a conventionally known configuration.

A cam member 53 engaged with the rack portion 52a of the piston 52 is urged in a direction opposite to the urging direction of the piston 52, and is rotatably attached to the casing 51. The lower edge portion of the cam member 53 includes a check tooth 53a that engages with the rack portion 52a and prohibits the piston 52 from moving in the biasing direction. And auxiliary teeth 53b for releasing the engagement between the rack portion 52a and the non-return teeth 53a when the piston 52 moves in the biasing direction.

The non-return tooth 53a has an inverted triangular shape corresponding to the tooth shape of the rack portion 52a at the front end of the lower edge of the cam member 53, and engages with substantially no gap between the teeth of the rack portion 52.
On the other hand, the auxiliary teeth 53b have teeth smaller than the check teeth 53a, that is, have small tooth heights, and are formed behind the check teeth 53a at a distance of, for example, three pitches in terms of the pitch of the rack 52b. The auxiliary teeth 53b are located in a non-contact state with the rack portion 52 with a predetermined gap therebetween when the check teeth 53a are engaged with the rack portion 52a, and are different from the check teeth 53a. It does not restrict the movement of the piston 52 by engaging with the rack 52a, but engages with the rack 52a only after the piston 52 starts to move.

As shown in FIG. 2, the cam member 53 has a rotation center CP having a check tooth 53a and an auxiliary tooth 53a.
b in the direction of the straight line connecting the auxiliary teeth 5
3b is set at a position deviated to the side of the check tooth 53a in front of 3b.
That is, the cam member 53 is rotatably supported by the rotation shaft 6 at a substantially central portion thereof. The rotation shaft center CP is located at a position offset by a predetermined distance in front of the auxiliary teeth 53b in the horizontal direction. Is set. The offset amount Off from the auxiliary teeth 53b is equal to the backlash amount B described later.
Adjust according to r.

The backlash amount Br is equal to the offset amount O
The distance of the movement of the auxiliary teeth 53b changes according to the maximum movement amount a by which the piston 52 projects by f. Cam member 53
In setting the rotation center CP, the extension of the auxiliary tooth 53b in the direction directly above is used as a reference position, and the offset amount Of is represented by a distance away from that position in the forward direction. When the offset amount Of increases, the distance from the reference position increases, so that the distance to the tip of the auxiliary tooth 53b, that is, the turning radius r of the auxiliary tooth 53b, increases as compared with the case where the rotation center CP is at the reference position. For this reason,
The trajectory of the auxiliary teeth 53b is extended in the forward direction of the rack portion 52a, and the moving distance of the auxiliary teeth 53b, that is, the moving distance of the piston 52 is increased. And the auxiliary teeth 53b
The amount of return of the cam member 53 increases by an amount corresponding to the increase in the moving distance, and the degree of freedom in setting the backlash amount Br increases.
That is, assuming that the pitch of the rack portion 52a is x and the maximum movement amount is a, the backlash amount Br is (ax) to a.
Becomes Here, the maximum movement amount a is set to be twice the pitch x, that is, larger than 2x.

Now, when the timing chain 2 is loosened and the piston 52 moves forward by the urging force, the rack 52
Since a has moved with respect to the cam member 53, the auxiliary teeth 53b move forward following the movement of the cam portion 52a. Thereby, as shown by the solid line in FIG. 3, the cam member 53 rotates, and the engagement of the check teeth 53a with the rack portion 52a is released. When the piston 52 moves further forward, the auxiliary teeth 53b are disengaged from the rack portion 52a, and the auxiliary teeth 53b engage with the tooth immediately after the tooth of the rack portion 52a which has been engaged up to that time, ie, the tooth one pitch behind. (Shown by a solid line in FIG. 4). In this state, since the non-return teeth 53a are not engaged with the rack portion 52a, the piston 52 is pushed back by the reaction of the cam member 52a. At this time, the backward moving distance, that is, the return amount is the backlash amount Br.
Is the amount obtained by subtracting x for one pitch from the maximum movement amount a, that is, (a−x).

As described above, the return amount is an amount obtained by subtracting one pitch of the teeth of the rack portion from the maximum movement amount. Therefore, the larger the maximum movement amount a is, the larger the return amount is. Since the maximum movement amount a depends on the radius of rotation of the auxiliary teeth 53b, the radius of rotation of the auxiliary teeth 53b increases if the offset amount from the reference position is increased in order to increase this. The goal can be achieved. For example, if the offset amount Of is set so that the maximum movement amount a is three times the pitch x of the rack portion 52a, that is, a = 3x, the backlash amount Br becomes 2x to 3x.
In this case, if the pitch x is 1 mm, the backlash amount Br is 2-3 mm, and the pitch x is 0.5 m
m, the backlash amount Br is 1 to 1.5 mm. Further, by changing the offset amount Of variously, the maximum movement amount a is set to an amount exceeding twice the pitch x, and the pitch x of the rack portion 52a is set as described above, so that various types of back-up are performed. It becomes possible to respond to the request for the rush amount Br.

Therefore, the timing chain 2 can be constantly pressed with the proper amount of backlash Br, so that it is possible to prevent the generation of friction noise generated when over tension occurs and collision noise generated when loose. Therefore, noise reduction in the engine employing the timing chain 2 can be achieved.

The present invention is not limited to the embodiment described above.

In addition, the configuration of each section is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view schematically showing one embodiment of the present invention.

FIG. 2 is a configuration explanatory view showing an enlarged main part of the embodiment.

FIG. 3 is an operation explanatory view showing an operation state of the embodiment.

FIG. 4 is an operation explanatory view showing an operation state of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cam shaft 2 ... Timing chain 3 ... Crank shaft 4 ... Chain tensioner 52 ... Piston 52a ... Rack part 53 ... Cam member 53a ... Non-return tooth 53b ... Auxiliary tooth CP ... Rotation center

Claims (1)

(57) [Claims] A timing chain for transmitting a driving force of a crankshaft of an engine to a camshaft is provided with a pressing member having a rack portion urged in a direction in which the tension is increased, and a timing member engaged with the rack portion. A rotatable cam member urged in a direction opposite to the urging direction of the pressing member so as to prohibit movement of the pressing member in the urging direction is provided, so that the tension of the timing chain becomes substantially constant. A timing member having a predetermined amount of backlash to adjust the timing chain, wherein a cam member engages with a rack portion on a lower edge thereof to inhibit movement of the pressing member in the biasing direction. When the pressing member moves in the biasing direction and is formed at a position separated from the non-return tooth by a predetermined distance in the reverse biasing direction from the non-return tooth, the tooth engages with the rack portion to engage the rack portion with the non-return tooth. And an auxiliary tooth for canceling the rotation of the cam member. Timing chain plunger mechanism and setting a position offset to the check tooth side from the auxiliary teeth at least the biasing direction.