JP2980750B2 - Prevention of timing band slack in valve train for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train for a vehicle in which a camshaft is rotated by a crankshaft via a timing band such as a timing chain or a timing belt, thereby opening and closing intake and exhaust valves. In particular, the present invention relates to a structure capable of preventing the timing band from being loosened even when a reverse rotation force acts on the crankshaft.

[0002]

2. Description of the Related Art In a valve train of a four-stroke engine, an automatic tensioner for automatically adjusting the tension of a timing belt or a timing chain is generally provided. In a valve train equipped with such an automatic tensioner, when a reverse rotation force acts on the crankshaft for some reason, the tooth jump of the timing belt may occur, though very rarely. This is likely to occur, for example, when a vehicle equipped with a manual transmission is set to a low gear and the vehicle is parked on an uphill with a weak parking brake. That is, a reverse rotation force acts on the crankshaft due to the reversing force of the tire, whereby the auto-tensioner side of the timing belt becomes a tension side, and the rod of the auto-tensioner retreats due to this tension. It is considered that the engagement start portion gradually loosens, and as a result, in extreme cases, tooth skipping occurs when the crankshaft rotates forward at the start of traveling. When the timing belt jumps like this, the opening and closing timings of the intake and exhaust valves are shifted, and in some cases, the engine cannot be started or knocking occurs.

Accordingly, the present applicant has proposed a tooth skipping prevention structure in which tooth skipping is prevented by implanting a guide pin close to the back surface of the engagement start position portion with the crank pulley on the tight side of the timing band. Yes (Japanese Patent Application No. 1-33
See 6928).

[0004]

However, in the case of the structure according to the above proposal, since it is necessary to accurately secure the gap between the timing band and the guide pin, the dimensional accuracy of the parts such as the guide pin and the timing band is strictly controlled. There is a problem that needs to be managed.

Further, in the case of the above-mentioned structure, since the loosening which occurs on the tight side of the timing band is not prevented, when the engine is started in the parking state on the sloping road, the crankshaft is correctly adjusted with the tight side of the timing band loosened. Will be rotated. Therefore, a strong tension acts on the slack side of the timing band from a state where almost no tension acts. Such a change in tension causes a decrease in the durability of the timing band.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is possible to prevent the slack itself of the timing band while eliminating the need for strict control of the dimensional accuracy and the processing accuracy. It is an object of the present invention to provide a structure for preventing a timing band from being loosened in a valve train for a vehicle, which can prevent flying and improve durability.

[0007]

According to the present invention, a driving member is fixed to a crankshaft, and 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. A bracket for supporting the pressing member to be 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, the tensioner main body, a tension cylinder is fixed to the engine main body, a tension rod is inserted into the tension cylinder with a predetermined outward biasing force, and the pressing surface of the bracket is pressed by the tip of the tension rod. The tension cylinder is provided with a stopper pin hole in the tension cylinder. The stopper pin is formed so as to extend in the moving direction, and a stopper pin for regulating the retreat position of the bracket is inserted into the stopper pin hole so as to be able to advance and retreat, and an urging spring for urging the stopper pin outward is inserted into the stopper pin hole. It is characterized in that a fixing bolt is provided to fix the stopper pin at a desired position.

[0008]

According to the timing band loosening 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 urging force of the tensioner main body, and appropriately holds the tension of the timing band. I do. On the other hand, when the above-described reverse rotation force acts on the crankshaft, and the pressing member side of the timing band becomes tight, the tension becomes greater than the urging force of the tensioner main body. It will be retracted to the main body side, but this retracted position is regulated by the stopper pin. Therefore, even if the rotational force in the opposite direction acts, there is almost no slack on the tight side of the timing band. as a result,
Tooth jumping can be prevented without providing the above-described tooth jump preventing guide pin. Also, since the slack itself hardly occurs,
Even when the crankshaft is rotated forward, the fluctuation of the tension does not become so large, and the durability of the timing band can be improved accordingly. Here, the distance between the tensioner main body and the bracket is determined by the balance between the initial tension applied by the tensioner main body and the tension in the timing band. In this case, since the stopper pin is provided on the tensioner main body in the present invention, the clearance between the stopper pin and the tensioner main body does not change due to an error in mounting the tensioner main body to the engine main body. The slack of the timing band can be prevented without requiring strict control of accuracy. Further, in the present invention, the stopper pin is disposed so as to be able to advance and retreat into the stopper pin hole and to be urged outward, and further to be fixed at a desired position, so that the gap between the stopper pin and the pressing surface, and thus the retreat position of the bracket, is set. Easy and reliable adjustment.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIGS. 1 to 3 are views for explaining a timing belt slack preventing structure in a vehicle valve train according to an embodiment of the present invention. In this embodiment, a case where the present invention is applied to a DOHC engine will be described as an example.

In FIG. 1, reference numeral 1 denotes a four-stroke engine employing the apparatus of this embodiment, and FIG. 1 shows a state in which a timing belt cover is removed. The engine 1 mainly has a cylinder head 1b fastened to the upper surface of a cylinder block 1a, and a cylinder head cover 1c
Is covered. The cylinder block 1a
1, a crankshaft 2 is rotatably inserted 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). Two camshafts 3a and 3b for opening and closing intake and exhaust valves are inserted and arranged rotatably in parallel with the crankshaft 2 on the mating surface of the cylinder head 1b and the head cover 1c.

A crank pulley 6 is mounted on a protruding end of the crankshaft 2 and is fixed by a semicircular key.
Further, cam pulleys 7a, 7b are mounted on the protruding ends of the camshafts 3a, 3b, respectively, and are fixed with pin keys.

A pump drive shaft 4 connected to an oil pump is supported at an oblique upper portion of 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 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. I have.

The above-mentioned crank pulley 6, cam pulley 7a,
A timing belt 10 is wound around the pulleys 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. Meshed with the set pulley teeth.

An idler pulley 11 is pivotally supported between the crank pulley 6 and the pulley 9 of the cylinder block 1a. Is pressed inward, whereby the winding angle of the crank pulley 6 is ensured.

An auto tensioner 12 is provided below the cam pulley 7a. The auto tensioner 12 includes a pulley unit 13 that presses the timing belt 10 inward, and a tensioner main 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 pivotally supports the upper end of a substantially L-shaped bracket 13a on a cylinder head 1b with a bolt 13d so as to be swingable. The pulley unit 13 is mounted on a back surface 10a of the timing belt 10 at a corner of the bracket 13a. The idler pulley 13b to be rolled and contacted is supported. The pressing surface 13c formed on the lower side of the bracket 13a is formed around the bolt 13d.
Is substantially perpendicular to the rotation direction c.

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

A stopper pin hole 14b is formed in the cylinder 14c of the tensioner body 14 in parallel with the tension rod 14a. A stopper pin 15 is inserted into the stopper pin hole 14b so as to be able to protrude and retract and is urged outward by an urging spring 17.
The stopper pin 15 is substantially perpendicular to the pressing surface 13c. Reference numeral 16 denotes a fixing bolt which is screwed in a direction perpendicular to the stopper pin hole 14b and positions the stopper pin 15 at a desired position.

Next, the operation and effect of this embodiment will be described. First, a 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. Thereby, the gap between the tensioner main body 14 and the pressing surface 13c becomes a predetermined value. In this state, the stopper pin 15 is pushed in all the way 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 forward by the urging spring 17 and comes into contact with the gauge G. At this position, the fixing bolt 16
With a tool T. According to the above procedure, the interval 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 (in the direction of arrow a) is transmitted from the crank pulley 6 via the timing belt 10 to the cam pulley 7.
a, 7b, whereby the intake and exhaust valves open and close. In the normal operation state, the timing belt 10 has the slack side on the side of the auto tensioner 12, but the slack is absorbed by the tension rod 14a of the tensioner 12 urging the bracket 13a counterclockwise in the drawing, and 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 a tight side. Then, the bracket 13a pushes the tension rod 14a of the auto tensioner 12 and retreats clockwise in the drawing. However, the bracket 13a stops at a position where the pressing surface 13c abuts against the stopper pin 15, and as a result, the timing belt 10 hardly loosens on the normal tension side.

As described above, in this embodiment, the stopper pin 1
5, the retraction position of the bracket 13a is regulated, so that the timing belt 10 does not slack even when a reverse rotation force acts on the crankshaft 2. Therefore,
A guide pin for preventing tooth skipping as in the above-described conventional structure is unnecessary, and tooth skipping can be prevented without strictly controlling dimensional accuracy and the like. Further, the gap between the tensioner main body 14 and the pressing surface 13c of the bracket 13a is maintained at a predetermined value as described above. Since the stopper pin 15 is provided on the tensioner main body 14, the mounting error of the tensioner main body 14 to the engine is prevented. Are the stopper pin 15 and the pressing surface 13
There is no effect on the gap between the components and c, and strict control of the dimensional accuracy of these parts and the like is not required. Also, when a reverse rotation force acts on the crankshaft 2, the timing belt 10
Since the slack does not occur, the fluctuation in tension due to the slack can be significantly reduced, and as a result, the durability can be improved. Furthermore, in the above embodiment, the stopper pin 15 is
Is disposed so as to be able to advance and retreat at right angles to the pressing surface 13c in the rotating direction of the pressing surface 13c, so that the gap between the stopper pin 15 and the pressing surface 13c, and furthermore, the retreat position of the bracket 13a can be easily and reliably adjusted.

In the above embodiment, the case where the invention is applied to a DOHC engine has been described as an example. However, the present invention can be applied to an SOHC engine having a single camshaft. In this case, the same effect as that of the above embodiment can be obtained. Can be Further, in the above embodiment, the timing belt is taken as an example, but the present invention can of course be applied to a case where a timing chain is used.

[0024]

As described above, according to the structure for preventing the timing band from being loosened in the valve operating apparatus for a vehicle according to the present invention, the stopper pin for regulating the retreat position of the bracket for supporting the pressing member is provided. Even when a force is applied to the shaft in the opposite direction, it is possible to prevent the timing band from being loosened, prevent tooth jump without requiring strict control of the dimensional accuracy of the tensioner body, bracket, etc. This has the effect of reducing fluctuations and improving the durability of the timing zone. In addition, since the stopper pin is disposed so as to be able to advance and retreat into the stopper pin hole and to be urged outward and to be able to be fixed at a desired position, the gap between the stopper pin and the pressing surface and, consequently, the retreat position of the bracket can be easily and reliably. There is an effect that can be adjusted.

[Brief description of the drawings]

FIG. 1 is a side view showing a structure for preventing a timing band from being loosened in a vehicle valve train according to one embodiment of the present invention.

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

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 engine 1b cylinder head (engine body) 2 crankshaft 3a, 3b camshaft 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 Body 15 Stopper pin (stopper member)

Claims (1)

(57) [Claims] A bracket for supporting a pressing member for fixing a driving member to a crankshaft, connecting the driving member to a driven member fixed to a camshaft by a timing band, and pressing a slack side portion of the timing band. swingably attached to the engine body, the slack prevention structure of the timing belt in the vehicle valve train the tensioner body attached to the engine body for adjusting the tension of the timing belt by urging the bracket, said tensioner body To
Fix the tension cylinder to the gin body,
Even if the tension rod is set in the cylinder
And insert the bracket with the tip of the tension rod.
The structure is designed to press the pressing surface of the
Insert the stopper pin hole into the
And a stopper pin for regulating the retreat position of the bracket is inserted into the stopper pin hole so as to be able to advance and retreat.
And an urging spring for urging the stopper pin outward.
Arranged in the stopper pin hole and the stopper pin
A timing belt in a valve operating device for a vehicle, wherein a fixing bolt for fixing the valve to a desired position is provided.