JPH0346162Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a camshaft drive structure for a V-type engine, and particularly to measures to prevent tooth skipping when the camshaft is driven by a timing belt.

(Prior art) Conventionally, as a V-type engine, for example,
As disclosed in Japanese Patent No. 90003, a so-called narrow-angle V-type engine is known in which a plurality of cylinders are arranged in a staggered manner to narrow the bank angle. In such an engine, the pitch between the cylinders can be set shorter than in an in-line type engine, so the overall length of the engine can be shortened, and the bank angle can be set shorter than in a normal V-type engine in which both banks of cylinders are arranged facing each other. Since it is narrow, the overall width of the engine can be narrowed, making the engine more compact.

(Problem that the invention aims to solve) By the way, one of the conventional methods to improve the combustion efficiency of an engine is to make the combustion chamber a conical pent-roof shape and to place the spark plug in the center of the combustion chamber. things are being done.

Therefore, when using this method for a narrow-angle V-type engine, the first camshaft is placed in the center of the bank to collectively drive the valves on the inside of the bank of multiple cylinders, and the valves on the outside of each bank are connected to each bank. It is conceivable to arrange a second driving camshaft. This idea has the advantage that one camshaft can be omitted and interference with the spark plug can be avoided.

In this case, as a method for driving the first and second camshafts, for example, as in the camshaft drive device disclosed in Japanese Utility Model Application Publication No. 60-32501,
A timing belt is wound between one end of the first camshaft and one of the second camshafts and the crankshaft, and a timing belt is wound between the other end of the first camshaft and the other second camshaft. It is conceivable to drive the camshafts by transmitting the driving force to each camshaft via a timing belt.

However, with this proposed narrow-angle V-type engine,
Due to the difference in the number of driven valves, the rotational resistance of the first camshaft is approximately twice as large as the rotational resistance of the second camshaft, so the surface pressure of the timing belt on each camshaft becomes uneven, and the surface pressure A problem arises in that the second camshaft, which has a small diameter, causes the timing belt to skip teeth.

The present invention has been made in view of the above, and its purpose is to appropriately set the drive order of the camshafts in the above-mentioned narrow-angle V-type engine so as to act on the camshafts with low rotational resistance. The purpose is to increase the tension of the timing belt and prevent the timing belt from skipping teeth.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention disposes a first camshaft in the center of the bank of a V-type engine to drive the valves on the inside of both banks, and A second camshaft for driving a valve on the outside of each bank is disposed in the bank, and the first camshaft and one of the second camshafts are driven by a timing belt wound between them and a drive shaft, The timing belt is tensioned with the direction of rotation set such that the first camshaft is on the slack side and the second camshaft is on the tight side.

(Function) With the above configuration, in the present invention, the driving force of the drive shaft is transmitted to the first camshaft and one of the second camshafts via the timing belt. In this case, the first camshaft of the timing belt is on the slack side and the second camshaft is on the tight side, so the surface pressure of the timing belt on the second camshaft is increased by the tension on the tight side, and The surface pressure of the timing belt on the first camshaft is maintained high due to the large rotational resistance of the first camshaft, and tooth skipping of the timing belt is prevented.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

1 and 2 show a V-type engine according to an embodiment of the present invention. In the figure, 1 is a cylinder block, 2 is a cylinder head disposed on the cylinder block 1, and 2 is a cylinder head disposed on the cylinder block 1.
A plurality of cylinders 3a,
3b... (four cylinders in the figure) are provided. These plurality of cylinders 3a, 3b... are arranged in half in the left bank L and right bank R of the engine, and are arranged in a staggered manner so that they are located between the cylinders of the other bank L, R. It is inclined in a V-shape with an acute narrow bank angle.

Further, the cylinder head 2 is provided with two intake ports 4a, 4b and two exhaust ports 5a, 5b for each cylinder, respectively. One end of the exhaust ports 5a, 5b is connected to each cylinder 3a to 3d.
It is opened to the outside of bank L or R, and the other end is opened to the side wall of the cylinder head on the same bank side. On the other hand, one end of the intake ports 4a, 4b is opened to the inside of the bank L or R of each cylinder 3a to 3d, and the other end is opened to the side wall of the cylinder head on the side of the other bank. 4b are communicated with each other via a communicating portion 4c midway. And each of the above-mentioned intake ports 4a, 4
Intake valves 6a and 6b are disposed at the openings to the cylinders 3a to 3d, respectively. On the other hand, exhaust valves 7a and 7b are provided at the openings of the exhaust ports 5a and 5b to the cylinders 3a to 3d, respectively. The installation angles of the intake and exhaust valves 6a, 6b, 7a, and 7b are set at approximately equal angles with respect to the center axis of each cylinder 3a to 3d, and a pent roof-type combustion chamber 8 is formed in each cylinder 3a to 3d. has been done. Further, a spark plug 9 is disposed at the center of the combustion chamber 8 of each cylinder 3a to 3d.

Furthermore, a first camshaft 10 is supported at the center of the banks L and R on the cylinder head 2 in parallel with the cylinder row, and the intake valves 6 of all the cylinders 3a to 3d are supported.
a and 6b are opened and closed. Also,
On the cylinder head 2, a second left camshaft 11 is supported on the outside of the left bank L in parallel with the cylinder row, and a second right camshaft 12 is supported on the outside of the right bank R in parallel with the cylinder row. The exhaust valves 7a and 7b of the cylinders 3a and 3c or 3b and 3d of each bank L and R are opened and closed. Note that 13 is a fuel injection valve disposed in each communication portion 4c.

Furthermore, the first and second camshafts 10
To explain the drive structure of Nos. 1 to 12, timing pulleys 14 and 15 having the same number of teeth are attached to the front end of the first camshaft 10 and the front end of the second left camshaft 11, respectively, as shown in FIG. At the same time, a timing pulley 17 having half the number of teeth of the timing pulleys 14 and 15 is attached to the front end of the drive shaft 16 of the engine, and a timing belt 18 is installed between each of the pulleys 14, 15, 17. wrapped around the drive shaft 16
by the first and left second camshafts 10,
11 are made to rotate at the same speed. Also, the rear end portion of the first camshaft 10 and the second left side
Timing pulleys 19 and 20 each having the same number of teeth are attached to the rear end of the camshaft 12, and a timing belt 21 is wound between the pulleys 19 and 20.
0 causes the second right camshaft to rotate at the same speed as the first camshaft 10.

The front timing belt 18 is
The rotation direction is the third so that the first camshaft 10 is on the slack side and the second camshaft 11 is on the tension side.
It is set and stretched in the direction of the arrow shown in the figure.

Therefore, in the above embodiment, in the camshaft drive structure of the first camshaft 10 and the second left camshaft 11, since the second left camshaft 11 is set to the tension side, the left second camshaft 11 is set to the tension side.
The surface pressure of the timing belt 18 acting on the pulley 15 of the camshaft 11 is increased by the tension on the tension side, and it is possible to effectively prevent tooth skipping of the timing belt 18 on the pulley 15 of the second right camshaft 11. can.

In addition, all cylinders 3a are controlled by the first camshaft 10.
~3d intake valves 6a and 6b are opened and closed,
Since the rotational resistance of the first camshaft 10 becomes large, both camshafts 10,
Since the tension of the timing belt 18 between the first camshaft 10 and the pulley 14 of the first camshaft 10 is increased, the surface pressure of the timing belt 18 acting on the pulley 14 of the first camshaft 10 is maintained high.
Even in this case, the timing belt 18 does not skip teeth.

(Effects of the invention) As explained above, according to the camshaft drive structure of the V-type engine of the invention, the second camshaft with low rotational resistance is placed on the tight side to increase the surface pressure of the timing belt on the second camshaft. Since the surface pressure of the timing belt on the first camshaft, which has a large rotational resistance, is maintained high by the rotational resistance, tooth skipping of the timing belt is prevented and the intake/exhaust timing of the engine is maintained accurately. It is something that can be done.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a plan view, FIG. 2 is a side view, and FIG. 3 is a longitudinal side view. 3a to 3d... cylinder, 10... first camshaft, 11, 12... second camshaft, 16...
Drive shaft, 18... Timing belt, R, L...
bank.

Claims (1)

[Scope of utility model registration request] A first camshaft is arranged in the center of the banks of the V-type engine to drive the valves on the inner side of both banks, and a second camshaft is arranged in each bank to drive the valves on the outer side of each bank. and the first camshaft and one of the second camshafts.
The camshaft is driven by a timing belt wound between these and the drive shaft, and the rotation direction of the timing belt is set so that the first camshaft is on the slack side and the second camshaft is on the tight side. V characterized by being stretched
Camshaft drive structure of type engine.