JP2710148B2 - Tooth skipping prevention structure for timing band in vehicle valve gear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to rotating a camshaft by a crankshaft via 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 tooth skipping in a timing band when a crankshaft is reversely rotated by some external force.

[Conventional technology]

Conventionally, in a four-stroke engine, a valve train that opens and closes intake and exhaust valves in synchronization with reciprocating motion of a piston is provided. In this valve gear, a cam pulley or a cam sprocket is fixed to an end of a camshaft that opens and closes an intake and exhaust valve, and a crank pulley or a crank sprocket is fixed to an end of a crankshaft. An auto-tensioner for automatically adjusting the tension of the belt and the like is provided while being connected by a chain, whereby the camshaft is driven to rotate by the crankshaft.

[Problems to be solved by the invention]

By the way, in the above-described conventional valve gear provided with an auto tensioner, since the slack of the timing belt is absorbed by the auto tensioner, attention has not been paid to the problem of tooth skipping. However, it has been found that when the crankshaft receives a force in the reverse rotation direction for some reason, the timing belt may jump, though rarely. This means that a vehicle equipped with a manual transmission is connected with the transmission and the crankshaft by a low-speed gear and the vehicle is parked on an uphill with a weak parking brake, or the vehicle is transported by a carrier car in a state similar to the above-described parking on a slope. It is easy to occur when doing. In other words, the reverse rotation of the tire causes a reverse rotation force to act on the crankshaft, 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. The engagement start part gradually loosens. As a result, in an extreme case, it is considered that tooth skipping occurs when the crankshaft rotates forward at the start of traveling. If the timing belt jumps like this, the opening and closing timing of the intake and exhaust valves shifts to the advanced side, and in some cases, the engine cannot be started or knocking occurs.

An object of the present invention is to provide a timing band tooth skip prevention structure in a vehicle valve train that can prevent tooth jump of a timing belt or the like when the crankshaft receives a reverse rotation force.

[Means for solving the problem]

According to the present invention, a driving member is fixed to a crankshaft connected to a manual transmission, a driven member is fixed to a camshaft, and the driven member and the driving member are connected by a timing band, and the tension of the timing band is reduced. In the valve operating device for a vehicle in which the camshaft is driven to rotate by the crankshaft while being adjusted by a tensioner, the timing band is prevented from skipping due to the rotation of the crankshaft in the reverse rotation direction. A guide pin is provided close to the rear side of the engagement start position with the drive member on the tension side of the timing band, and the guide pin is provided close to the timing band cover. It is characterized by being attached to the side.

Here, the present invention can be applied to both the one driven by the timing belt and the one driven by the timing chain.When the guide pins are brought close to each other, the guide pins are brought close to the extent that the engagement with the drive member does not come off even if the timing band is loosened. It means that it is arranged.

[Action]

According to the structure for preventing tooth skipping of the timing band in the valve operating device for a vehicle according to the present invention, the guide is provided at the engagement start position of the timing band and the driving member, that is, the slack side (normally the tight side) when the crankshaft is reversed. Since the pin is provided, even if the timing band is slackened by the reverse rotation of the crankshaft in the state of the vehicle posture as described above, the guide pin prevents the engagement with the driving member of the timing band from being disengaged during re-running. Since this is prevented, the tooth skipping of the timing band does not occur. As a result, it is possible to avoid a shift in the opening / closing timing of the intake and exhaust valves, and to prevent the engine from being unable to start or knocking.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 to 3 are views for explaining a tooth belt jump prevention structure of a timing belt 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 double overhead camshaft (DOHC) engine will be described as an example.

In FIG. 1, reference numeral 1 denotes a four-cycle engine employing the apparatus of the present embodiment, and FIG. 1 shows a state in which a timing belt cover is removed. The engine 1 mainly includes a cylinder block 1a, a cylinder head 1b mounted thereon, and a cylinder head cover 1c mounted thereon. A crankshaft 2 is rotatably inserted in a lower part of the cylinder block 1a 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, 3b for opening and closing intake and exhaust valves are provided on the mating surface between the cylinder head 1b and the head cover 1c.
Are inserted parallel to the crankshaft 2 and rotatably.

A crank pulley 6 and an output take-out pulley 15 are sequentially mounted on the protruding end of the crankshaft 2, and a semi-cylindrical key 2a, 2
Fixed at b. Further, cam pulleys 7a, 7b are mounted on the protruding ends of the respective camshafts 3a, 3b, and are fixed by pin keys 21.

The crank pulley 6 of the cylinder block 1a
A pump drive shaft 4 connected to an oil pump is pivotally supported at an obliquely upper portion, 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 pulleys 7a and 7b, and each pulley
A timing belt 10 is wound around 8, 9 and covered with a timing belt cover, and belt teeth 10b engraved on the inner surface of the belt 10 are formed on the outer surface of each pulley 6, 7a, 7b, 8, 9. It is in mesh with the engraved pulley teeth.

An idler pulley 11 is rotatably supported between the crank pulley 6 and the pulley 9 of the cylinder block 1a. The idler pulley 11 is brought into rolling contact with a back surface 10a of the timing belt 19 so as to bring the timing belt 10 inward. The crank angle of the crank pulley 6 is secured.

Further, an auto tensioner 14 is disposed below the cam pulley 7a. The tensioner 14 pivotally supports one end of an L-shaped bracket 13a by a cylinder head 1b so as to be swingable, and pivotally supports an idler pulley 13b which is in rolling contact with the back surface 10a of the timing belt 10 at a corner portion of the bracket 13a. At the same time, the tensioner body 14 that constantly urges the other end of the bracket 13a inward is fixed to the cylinder head 1b. A tension rod 14a inserted into the cylinder of the tensioner body 14 with a predetermined outward bias contacts the other end of the bracket 13a.
Thus, the timing belt 10 is always automatically adjusted to a constant tension. Thus, the valve train 16 of the present embodiment is configured.

Then, the timing belt 10 and the cam pulley 7b
A guide bolt 18 is disposed at the engagement end position A with the guide belt 18 so as to approach the back surface 10a of the timing belt 10. The guide bolt 18 is fixed to a bracket 22 with a nut 20. Further, the clearance between the guide bolt 18 and the back surface 10a of the timing belt 10 is set to a dimension such that the engagement between the belt teeth and the pulley teeth does not come off even when the timing belt 10 is loosened, for example, about 1 to 2 mm. Further, at a position B at which the timing belt 10 engages with the crank pulley 6, a rear surface of the timing belt 10 is provided.
A guide pin 17 is provided so as to be close to 10a. The guide pin 17 is arranged inside the seal mating surface of the timing belt cover, and is fixed by inserting a bolt 17a into the collar 17b and screwing the bolt 17a into the cylinder block 1a. And this color 17b and belt 1
The clearance between the 0 and the back surface 10a is also set to a dimension that does not disengage, for example, about 1 to 2 mm.

 Next, the operation and effect of this embodiment will be described.

The valve train 16 of the present embodiment adjusts the tension of the timing belt 10 with the auto tensioner 12 while the first
The clockwise rotation (arrow a) is transmitted to the cam pulleys 7a and 7b, thereby opening and closing the intake and exhaust valves according to the reciprocating motion of the piston.

In such a valve operating device 16, for example, the vehicle is parked in a state in which the low gear of the transmission of the vehicle and the crankshaft 2 are connected to each other, and the tire of the vehicle rotates backward due to some reasons such as poor parking brake effectiveness, and the crankshaft 2 Receives rotational force in the reverse rotation direction (arrow b), in the conventional structure, the tooth jump occurs at the engagement start position B of the timing belt 10 with the crank pulley 6 or the engagement end position A of the timing belt 10 with the cam pulley 7b. There was a problem of doing. On the other hand, in the present embodiment, the guide bolts 18 and the guide pins 17 are arranged close to the back surface 10a of the timing belt 10 at the respective meshing positions A and B, so that the belt teeth 10b and the pulley Disengagement with the teeth 6a can be prevented, and the teeth do not jump. As a result,
Inability to start the engine or knocking due to a shift in the opening / closing timing of the exhaust valve can be avoided.

In the above embodiment, the guide bins are provided on both the crankshaft side and the camshaft side. However, in the present invention, it is sufficient to provide the guide pins at least on the crankshaft side.

Further, in the above embodiment, the case where the present invention is applied to a DOHC engine has been described as an example. However, the present invention can be applied to a SOHC engine having a single camshaft. In the above embodiment, the timing belt is used as an example. However, the present invention can be applied to a case where a timing chain is used.

〔The invention's effect〕

As described above, according to the structure for preventing tooth skipping of the timing band in the valve operating apparatus for a vehicle according to the present invention, the guide pin is provided close to the back surface of the engagement start position with the driving member on the tight side of the timing band. In addition, there is an effect that the tooth jump in the timing band can be reliably prevented when the crankshaft is reversely rotated by some external force.

[Brief description of the drawings]

1 to 3 are views for explaining a tooth belt jump prevention structure of a timing belt in a vehicle valve gear according to an embodiment of the present invention. FIG. 1 is a side view of the valve gear, and FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a sectional view taken along the line III-III of FIG. In the figure, 2 is a crankshaft, 3a and 3b are camshafts, 6 is a crank pulley (driving member), 7a and 7b are cam pulleys (driven members), 10 is a timing belt, 10a is the back of the timing belt, and 14 is an auto tensioner. , 16 is a valve gear, 17 is a guide pin, and B is a meshing start position.

Claims (1)

(57) [Claims] 1. A driving member is fixed to a crankshaft connected to a manual transmission, and the driving member and a driven member fixed to a camshaft are connected by a timing band.
In a valve operating device for a vehicle in which the camshaft is driven by the crankshaft while adjusting the tension of the timing band with a tensioner, the timing band is prevented from skipping due to reverse rotation of the crankshaft. A guide pin provided close to a back surface of the engagement start position portion with the drive member on the tight side of the timing band, and the guide pin is disposed inside a sealing mating surface of the timing band cover and the engine is provided. A tooth band skip prevention structure for a timing band in a valve operating device for a vehicle, wherein the structure is mounted on a side of the vehicle.