JPH0598992A - Structure for preventing timing strip from slackness in valve system for vehicle - Google Patents

Abstract

PURPOSE:To provide a stopper member for regulating a retreat position of a bracket and prevent a timing strip from slackness in the reversal of a crankshaft by energizing the bracket for supporting a press member pressing the slackness side of the timing strip to adjust the tension of the strip. CONSTITUTION:The clockwise rotation of a crankshaft 2 is transmitted from a crank pulley 6 through a timing belt 10 to cam pulleys 7a, 7b, and the belt 10 has the autotensioner 12 side as the slackness side. The slackness is absorbed by a tension rod 14 energizing a bracket 13a counterclockwise to adjust properly the tension of the belt 10. On the other hand, when a counterclockwise turning force acts on the crankshaft 2 in parking on an uphill or the like, the belt 10 has the autotensioner 12 as the tensioned side. While the bracket 13a pushes the rod 14a and retreats clockwise, the retreat is stopped by the bracket abutting against a stopper pin 15 to prevent the belt 10 from the slackness at the normal tension side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for a vehicle, in which a crankshaft is used to rotate a camshaft through a timing band such as a timing chain or a timing belt, thereby opening and closing intake and exhaust valves. More particularly, the present invention relates to a structure capable of preventing the timing band from being loosened even when a reverse rotational force acts on the crankshaft.

[0002]

2. Description of the Related Art In a four-cycle engine valve train, it is common to provide an autotensioner for automatically adjusting the tension of a timing belt or timing chain. In a valve train equipped with such an autotensioner, if a reverse rotational force acts on the crankshaft for some reason, the timing belt may jump, though it is rare. This is likely to occur, for example, when a vehicle equipped with a manual transmission has a low speed gear and is parked uphill with a weak parking brake. That is, a reverse rotational force acts on the crankshaft due to the reversal force of the tire, which causes the autotensioner side of the timing belt to become a tension side, and this tension causes the rod of the autotensioner to retract, which causes the crank pulley and the timing belt to move backward. It is conceivable that the meshing start portion of the slackens gradually, and as a result, in an extreme case, tooth skipping occurs when the crankshaft rotates forward at the start of traveling. If such timing belt tooth jumping occurs, the opening and closing timings of the intake and exhaust valves are deviated, and in some cases, the engine cannot be started or knocking occurs.

Therefore, the applicant of the present invention has proposed a tooth jump prevention structure in which tooth jumps are prevented by implanting guide pins in close proximity to the rear surface of the meshing start position of the crank pulley on the tension side of the timing band. (Japanese Patent Application 1-33
6928).

[0004]

However, in the structure according to the above-mentioned proposal, it is necessary to accurately secure the gap between the timing band and the guide pin. There is a problem that it needs to be managed.

Further, in the case of the above structure, since the loosening itself which occurs on the tension side of the timing band is not prevented, when the engine is started in the above-mentioned slope parking state, the crank shaft is straightened when the tension side of the timing band is loose. It will be rotated. Therefore, on the slack side of the timing band, a strong tension suddenly acts from a state where almost no tension acts. Such tension fluctuations cause deterioration of the durability of the timing band.

The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to prevent slackening of the timing band itself without requiring strict control of dimensional accuracy and machining accuracy, and as a result, teeth of the timing band are prevented. An object of the present invention is to provide a structure for preventing loosening of a timing band in a valve operating system for a vehicle, which is capable of preventing flying and improving durability.

[0007]

According to the present invention, a driving member is fixed to a crankshaft, the driving member and a driven member fixed to a camshaft are connected by a timing band, and a slack side portion of the timing band is pressed. Of the timing band in the valve operating device for a vehicle in which a bracket supporting a pressing member is swingably attached to the engine body and a tensioner body for adjusting the tension of the timing band by urging the bracket is attached to the engine body. In the loosening prevention structure, a stopper member for restricting the retracted position of the bracket is provided on the tensioner body or the bracket. Here, the restriction position is set by the stopper member, for example, so that the amount of retreat of the bracket is set to an amount that can absorb the tension fluctuation in the timing band caused by the normal torque fluctuation.

[0008]

According to the timing band slack prevention structure of the present invention, in the normal state, the pressing member presses the slack side of the timing band with a force corresponding to the biasing force of the tensioner body, and the timing band tension is properly maintained. To do. On the other hand, when the above-mentioned reverse rotational force acts on the crankshaft and the pressing member side of the timing band becomes the tension side, this tension becomes larger than the urging force of the tensioner body, so the bracket supporting the pressing member is attached to the tensioner. Although it will be retracted to the main body side, this retracted position is regulated by the stopper member. Therefore, even when the rotational force in the opposite direction is applied, there is almost no slack on the tight side of the timing band. as a result,
It is possible to prevent tooth skipping without providing the guide pin for preventing tooth jumping. In addition, since slack hardly occurs,
Even if the crankshaft is rotated in the forward direction, the fluctuation in tension does not increase so much, and the durability of the timing band can be improved accordingly. Here, the distance between the tensioner body and the bracket is determined by the balance between the initial tension applied by the tensioner body and the tension of the timing band. In this case, since the stopper member is provided in the tensioner body or the bracket in the present invention, the clearance between the stopper member and the tensioner body or the bracket does not change due to an error in mounting the tensioner body to the engine body. It is possible to prevent loosening of the timing band without requiring strict control of dimensional accuracy and processing accuracy.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are views for explaining a slack preventing structure for a timing belt in a vehicle valve operating system according to an embodiment of the present invention. In the present embodiment, a case where the present invention is applied to a DOHC engine will be described as an example.

In the figure, reference numeral 1 is a four-cycle engine in which the apparatus of this embodiment is adopted, and FIG. 1 shows a state in which a timing belt cover is removed. In the engine 1, a cylinder head 1b is mainly fastened to an upper surface of a cylinder block 1a, and a cylinder head cover 1c is provided above the cylinder head 1b.
It is configured to cover. The cylinder block 1a
A crankshaft 2 is rotatably inserted in the lower portion of the drawing in a direction perpendicular to the plane of FIG. 1, and the crankshaft 2 is connected to a manual transmission via a clutch (not shown). Further, two cam shafts 3a and 3b for opening and closing intake and exhaust valves are arranged in parallel with the crank shaft 2 and rotatably inserted in the mating surface of the cylinder head 1b and the head cover 1c.

A crank pulley 6 is attached to the protruding end of the crankshaft 2 and is fixed by a semicircular key.
Further, cam pulleys 7a and 7b are attached to the projecting end portions of the cam shafts 3a and 3b, and are fixed by a pin key.

A pump drive shaft 4 connected to an oil pump is rotatably supported diagonally above the crank pulley 6 of the cylinder block 1a, and a pulley 8 is fixed to the drive shaft 4. Further, a cooling water drive shaft 5 connected to a water pump is pivotally supported at an intermediate portion between the crank pulley 6 and the cam pulley 7b of the cylinder block 1a, and a pulley 9 is fixed to the drive shaft 5. There is.

The crank pulley 6, the cam pulley 7a,
A timing belt 10 is wound around 7b and the pulleys 8 and 9, and belt teeth 10b formed on the inner surface of the belt 10 are formed on the outer surfaces of the pulleys 6, 7a, 7b, 8, and 9. Meshes with the pulley teeth.

An idler pulley 11 is rotatably supported between the crank pulley 6 and the pulley 9 of the cylinder block 1a, and the pulley 11 is in rolling contact with the back surface 10a of the timing belt 19 and the timing belt 10. Is pressed inwardly, whereby the winding angle of the crank pulley 6 is secured.

An auto tensioner 12 is arranged below the cam pulley 7a. The auto tensioner 12 includes a pulley unit 13 that presses the timing belt 10 inward, and a tensioner body 14 that urges the unit 13. An engine mount bracket 18 is fixed below the tensioner body 14 of the cylinder block 1a.

The pulley unit 13 has a generally L-shaped bracket 13a whose upper end is pivotally supported on the cylinder head 1b by a bolt 13d so that the bracket 13a can be pivotally supported by a corner portion of the bracket 13a on the rear surface 10a of the timing belt 10. It has a structure in which an idler pulley 13b that rolls is pivotally supported. The pressing surface 13c formed on the lower side of the bracket 13a has the bolt 13d as the center.
Is substantially perpendicular to the rotation direction c of.

The tensioner body 14 has a structure in which a tension rod 14a is inserted into a cylinder 14c fixed to a cylinder head 1b by a bolt with a predetermined outward biasing force. The pressing surface 13c of the bracket 13a is pressed in the rotation direction c, thereby urging the bracket 13a and thus the idler pulley 13b in the tension direction.

A stopper hole 14b is formed in the cylinder 14c of the tensioner body 14 in parallel with the tension rod 14a. This stopper hole 14b
The stopper pin 15 can be retracted inside and the biasing spring 1
It is urged outward by 7 and inserted, and the stopper pin 15 is substantially perpendicular to the pressing surface 13c. A fixing bolt 16 is screwed in a direction perpendicular to the stopper hole 14b and positions the stopper pin 15 at a desired position.

Next, the function and effect of this embodiment will be described. First, the procedure for setting the stopper pin 15 of the auto tensioner 12 will be described. The tension rod 14a of the auto tensioner 12 is brought into contact with the pressing surface 13c of the bracket 13a so that the timing belt 10 is given a normal initial tension. As a result, the gap between the tensioner body 14 and the pressing surface 13c becomes a predetermined value. In this state, the stopper pin 15 is pushed all the way in and fixed with the fixing bolt 16. Then, the fixing bolt 16 is loosened while the gauge G is in contact with the pressing surface 13c. Then, the stopper pin 15 is pushed by the urging spring 17 and moves forward to come into contact with the gauge G. At this position, the fixing bolt 16
Tighten with the tool T. By the procedure described above, the distance between the pressing surface 13c and the stopper pin 15 can be easily adjusted even after the tensioner 12 is attached to the cylinder head 1b.

In the valve gear 16 of this embodiment, the rotation of the crankshaft 2 in the clockwise direction in FIG. 1 (direction of arrow a) is changed from the crank pulley 6 to the cam pulley 7 via the timing belt 10.
a and 7b, which causes the intake and exhaust valves to open and close. In this normal operating state, the timing belt 10 is slack on the auto tensioner 12 side, but this slack is absorbed by the tension rod 14a of the tensioner 12 urging the bracket 13a in the counterclockwise direction in the figure, and the timing is The tension of the belt 10 is properly adjusted.

On the other hand, when a counterclockwise (in the direction of arrow b) rotational force is applied to the crankshaft 2 for some reason, for example, when the vehicle is parked on a slope, the auto tensioner 12 side of the timing belt 10 becomes the tension side. The bracket 13a pushes in the tension rod 14a of the auto tensioner 12 and retracts clockwise in the drawing. However, the bracket 13a stops at a position where the pressing surface 13c of the bracket 13a abuts the stopper pin 15, and as a result, the slack hardly occurs on the normal tension side of the timing belt 10.

As described above, in this embodiment, the stopper pin 1
Since the rearward position of the bracket 13a is restricted by 4a, the timing belt 10 is not loosened even when a reverse rotational force acts on the crankshaft 2. Therefore, the guide pin for preventing the tooth jump unlike the conventional structure described above is unnecessary, and the tooth jump can be prevented without strictly controlling the dimensional accuracy and the like. In addition, the tensioner body 14
The gap between the pressing surface 13c of the bracket 13a and the bracket 13a is maintained at a predetermined value as described above.
Since the stopper pin 15 is provided on the tensioner body 1,
Since the mounting error of No. 4 on the engine does not affect the gap between the stopper pin 15 and the pressing surface 13c, strict control of the dimensional accuracy of these parts and the like is not required. Further, since the timing belt 10 is not loosened even when the reverse rotational force acts on the crankshaft 2, the fluctuation in tension caused by the looseness can be significantly reduced, and the durability can be improved as a result.
Furthermore, in the above-mentioned embodiment, since the stopper pin 15 is arranged at right angles to the pressing surface 13c and so as to be movable back and forth in the rotating direction of the pressing surface 13c, the stopper pin 15 and the pressing surface 1
It is possible to easily and surely adjust the clearance with respect to 3c, and hence the retracted position of the bracket 13a.

In the above embodiment, the stopper pin 15
Although the stopper pin is provided on the tensioner main body 14 side, the stopper pin may be provided anywhere as long as it can regulate the retracted position of the bracket 13a, and may be provided on the bracket 13, for example. Although the stopper pin 15 can be moved forward and backward to adjust the clearance, the stopper pin may be fixed. In the above embodiment, DOH
Although the case where the present invention is applied to the C engine has been described as an example, the present invention can also be applied to the SOHC engine having one camshaft,
Also in this case, the same effect as that of the above-mentioned embodiment can be obtained. Furthermore, although the timing belt is taken as an example in the above embodiment,
The present invention can of course be applied to the case where a timing chain is used.

[0024]

As described above, according to the slack preventing structure for the timing band in the vehicular valve operating system according to the present invention, the stopper member for restricting the retracted position of the bracket for pivotally supporting the pressing member is provided. Even when a force in the opposite direction is applied to the crankshaft, it is possible to prevent slack in the timing band, and prevent tooth skipping without requiring strict control of the dimensional accuracy of the tensioner body, bracket, etc. This has the effect of reducing tension fluctuations and improving the durability of the timing band.

[Brief description of drawings]

FIG. 1 is a side view showing a structure for preventing loosening of a timing band in a vehicle valve operating system according to an embodiment of the present invention.

FIG. 2 is a side view of an auto tensioner portion of the above embodiment.

FIG. 3 is a sectional view taken along line III-III in FIG.

[Explanation of symbols]

 1 Engine 1b Cylinder Head (Engine Main Body) 2 Crank Shafts 3a, 3b Cam Shaft 6 Crank Pulley (Drive Member) 7a, 7b Cam Pulley (Driven Member) 10 Timing Belt (Timing Band) 13b Idler Pulley (Pressing Member) 13a Bracket 14 Tensioner Main body 15 Stopper pin (Stopper member)

Claims (1)

[Claims] 1. A bracket for supporting a pressing member for fixing a driving member to a crank shaft, connecting the driving member and a driven member fixed to a cam shaft by a timing band, and pressing a slack side portion of the timing band. In a structure for preventing loosening of a timing band in a valve operating system for a vehicle in which a tensioner body for swingably attaching to an engine body and adjusting the tension of the timing zone by urging the bracket is attached to the engine body, A structure for preventing loosening of a timing band in a valve operating system for a vehicle, wherein a stopper member for restricting a retracted position is provided on the tensioner body or the bracket.