JPH05231108A - Four-cycle engine - Google Patents

Abstract

PURPOSE:To provide a 4-cycle engine where compactness of the engine can be achieved and a lifetime of transmission mechanisms interposed between camshafts ban be prolonged. CONSTITUTION:A 4-cycle engine, where the number of intake valves 10 is larger than that of exhaust valves 11, is provided with a camshaft 12 for driving the intake valves 10, and another camshaft 13 for driving the exhaust valves 11. A crankshaft of the engine is connected to the camshaft 12 having the larger number of driving valves via a pulley 19 and a first transmission mechanism consisted of a winding transmission belt, while the camshaft 12 is connected to the camshaft 13 having the smaller number of driving valves through a second transmission mechanism constituted of gears 17, 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-cycle engine provided with a cam shaft for driving an intake valve and a cam shaft for driving an exhaust valve.

[0002]

2. Description of the Related Art Conventionally, as a multi-valve type four-cycle engine, a high intake and exhaust efficiency is obtained by increasing the number of intake valves and exhaust valves provided for each cylinder. What you have done is known. In this engine, high performance can be expected when these intake and exhaust valves are driven by separate cam shafts, the intake valve being the intake cam shaft and the exhaust valve being the exhaust cam shaft.

In such a multi-valve engine, when the camshaft is driven by the crankshaft, a transmission mechanism such as a winding transmission belt is provided between the camshaft and the crankshaft, and the engine is rotated via this transmission mechanism. The driving force is transmitted to the camshaft. In this case, when transmitting from the crankshaft to the two camshafts via the respective transmission mechanisms,
Since it is necessary to reduce the rotation of the camshaft to half of that of the crankshaft, and the diameter of the transmission wheel on the camshaft side is twice that on the crankshaft side, such a large diameter transmission wheel is If it is provided on both the intake camshaft and the exhaust camshaft, the size of the engine will increase.

Therefore, of the two camshafts, only one camshaft is provided with a transmission mechanism between it and the crankshaft, and the other camshaft is driven from this camshaft via another small transmission mechanism. By doing so, it is possible to avoid the above-mentioned increase in size and make the engine compact. by the way,
When operating in the valve opening direction, the camshaft that drives the intake valve or exhaust valve receives the reaction force on the counter rotation side, but when it operates in the valve closing direction, it rotates while receiving the additional force on the forward rotation side. Therefore, there is always torque fluctuation. This torque fluctuation becomes larger as the cam shaft with the larger number of valves to be driven (the intake cam shaft in the above example). Therefore, when the other cam shaft is driven by the one cam shaft via the transmission mechanism as described above, if a large rotational fluctuation occurs due to torque fluctuation in the driven side cam shaft, this rotational fluctuation causes an inter-cam shaft The life of the power transmission mechanism will be shortened. Especially, since the heat generated in the combustion chamber is transmitted around the cam shaft and becomes high in temperature, the life of the transmission mechanism between the cam shafts tends to be further shortened. Therefore, it is strongly desired to extend the life of the transmission mechanism in such a severe environment.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-valve engine equipped with a cam shaft for driving an intake valve and a cam shaft for driving an exhaust valve, while achieving a compact engine and a space between the cam shafts. The purpose of the present invention is to provide a four-cycle engine capable of extending the life of the transmission mechanism provided in the.

[0006]

In a four-cycle engine of the present invention that achieves the above object, the number of intake valves and exhaust valves provided in a cylinder is greater than that of the other, and a cam that drives the intake valves is provided. In a four-cycle engine provided with a shaft and a camshaft for driving the exhaust valve, the crankshaft of the engine is the camshaft with the larger number of drive valves among the two camshafts via the first transmission mechanism. And the cam shaft is connected to the cam shaft having the smaller number of drive valves via the second transmission mechanism.

The structure of the four-cycle engine of the present invention will be described below with reference to the accompanying drawings. 1 to 3
Is an embodiment of the present invention applied to a diesel engine, in which 1 is a cylinder body, 2 is a cylinder head fixed to the upper part of the cylinder body 1, and 3 is a head fixed to the upper part of the cylinder head 2. It is a cover. Four cylinders 4 are provided in a row in the cylinder body 1, and a piston 5 is reciprocally fitted in each cylinder 4. On both sides of the cylinder head 2, a plurality of bolt mounting holes 6 penetrating in the vertical direction are provided at both ends in the longitudinal direction and at positions corresponding to the cylinders 4 and 4 adjacent to each other. The cylinder head 2 is fixed to the cylinder body 1 with bolts 7 through the bolt mounting holes 6.

In addition, on both sides of the cylinder head 2, intake pipes 8 and 8 and an exhaust pipe 9 that are branched into two for each cylinder 4 are provided.
And are provided. The combustion chamber 4a above the cylinder 4 is provided with two intake valves 10, 10 corresponding to the intake pipes 8, 8 and one exhaust valve 11 corresponding to the exhaust pipe 9.
Is provided. The valve rod 10a of the intake valve 10 and the valve rod 11a of the exhaust valve 11 are provided so as to be parallel to the axial direction of the cylinder 4 and slide vertically on the cylinder head 2. Reference numeral 20 is a fuel injection nozzle, and 21 is a preheating plug.

At the upper end of the valve rod 10a of the intake valve 10 and the upper end of the valve rod 11a of the exhaust valve 11, there are provided a cam shaft 12 for opening and closing the intake valve 10 and a cam shaft 13 for driving the exhaust valve 11 for opening and closing. It is provided. This allows the camshaft 12
Drives two intake valves 10, 10 per cylinder, whereas the camshaft 13 has one exhaust valve 11 per cylinder.
Is designed to drive. These two camshafts 1
The cylinders 2 and 13 are arranged above the cylinder head 2 at inner positions by the bolt mounting holes 6 and parallel to the arrangement direction of the plurality of cylinders 4. And both ends,
At a position corresponding to each other between the cylinders 4 and 4 which are adjacent to each other, they are axially supported by bearings 14 each having a half-structure.

The half bearing 14 has an upper bearing portion 14a.
And the lower bearing portion 14b are separately configured. The lower bearing portion 14b is integrated with the cylinder head 2, and the camshafts 12 and 13 are placed on the lower bearing portion 14a to cover the upper bearing portion 14a. And the central portion are integrally fixed by bolts 15, 15 and 16, respectively. Bolts 1 on both ends
Reference numerals 5 and 15 are inside the bolt mounting holes 6 for the bolts 7 for fixing the cylinder head 2 to the cylinder body 1 and are offset in the arrangement direction of the plurality of cylinders. Thus, the entire half bearing 14 is housed inside the bolt mounting holes 6 and 6 on both sides in the width direction.

The cam shafts 12, 13 pivotally supported as described above
Among them, a cam shaft 12 for simultaneously driving two intake valves 10, 10 per cylinder has a pulley 19 fixed to its shaft end, and a winding transmission band is provided between the pulley 19 and a crank shaft (not shown). By being mounted, power is input from the crankshaft. Gears 17, 18 meshing with each other are fixed to the other shaft end of the cam shaft 12 and the shaft end of the cam shaft 13 adjacent thereto by bolts 17a, 18a. Therefore, the power of the camshaft 12 is the gear 17,
18 is used as a transmission mechanism to be transmitted to the camshaft 13.

FIG. 4 shows another embodiment of the present invention. In this embodiment, from the crankshaft to the camshafts 12, 1
The transmission path of the power to 3 is the same as that of the above-mentioned embodiment. The difference is that the upper bearing portion 14a of the half bearing 14 has two bolts 15 and 1 at both ends.
It is fixed by 5 and is fixed by a total of 5 bolts together with the central bolt 16. The bolts 15, 15 are located inside the bolt holes 6 for fixing the cylinder head, and are offset in the arrangement direction of the plurality of cylinders. Further, the gears 17, 18 provided at the shaft ends of the cam shafts 12, 13
Are integrally formed with the cam shafts 12 and 13, respectively.

The engine of each of the embodiments described above is a multi-valve type four-cycle engine having two intake valves 10 and one exhaust valve 11, but the intake side camshaft 12 having a large number of driven valves is used. As a first transmission mechanism connected to the crankshaft, a pulley 19 and a winding transmission band associated with the pulley 19 are provided, and a second camshaft 13 on the exhaust side is connected to the camshaft 12.
Gears 17 and 18 are provided as a transmission mechanism of. Since only one large-diameter pulley 19 is provided to drive both camshafts 12 and 13, the engine can be made compact. Further, since the torque fluctuation of the exhaust side cam shaft 13 having a smaller number of driven valves is smaller than that of the cam shaft 12, the rotation fluctuation transmitted to the gears 17 and 18 is small and the life of the second transmission mechanism is extended. ..

Further, in the above embodiment, the valve rods 10a and 11a of the intake and exhaust valves are provided so as to be substantially perpendicular to the cylinder head 2. In this configuration, the two cam shafts 12,
13 is arranged above the cylinder head and inside the bolt mounting hole 6. By such an arrangement, the protrusion to both outsides of the bolt mounting hole 6 is suppressed,
The cylinder head 2 is made narrower and smaller.
Even if the cam shafts 12 and 13 are arranged inside the bolt mounting holes 6 as described above, if the half-divided bearing 14 supporting the cam shafts 12 and 13 is wide, the entire cylinder head is narrowed. However, in the above embodiment, the bolts at the positions where both ends of the upper bearing portion 14a of the half bearing 14 are offset from the bolt mounting holes 6 in the cylinder arrangement direction. By fixing with 15, the whole cylinder head is made narrower.

Although the above embodiment has been described with respect to the diesel engine, the present invention is also applicable to the gasoline engine. Also, 2 per cylinder
Although the three-valve system in which one intake valve and one exhaust valve are provided has been described, the present invention can be applied to a case where the number of intake valves and exhaust valves is further increased.

[0016]

As described above, according to the present invention, the number of intake valves and exhaust valves provided in the cylinder is made larger than the other, and the cam shaft for driving the intake valves and the exhaust valves are driven. In a four-cycle engine provided with a camshaft for driving, the crankshaft of the engine is connected to the camshaft having the larger number of drive valves of the two camshafts via the first transmission mechanism. Is connected to the camshaft having the smaller number of drive valves via the second transmission mechanism, the large-diameter transmission wheels forming the first transmission mechanism are reduced to one series, and the engine is made compact. Since the camshaft having the smaller number of drive valves and the smaller torque fluctuation is driven by the second transmission mechanism, the rotation fluctuation transmitted to the second transmission mechanism is reduced and the life thereof can be extended.

[Brief description of drawings]

FIG. 1 is a plan view showing a diesel engine according to an embodiment of the present invention with a head cover removed.

FIG. 2 is a sectional view taken along line BB of FIG.

3 is a sectional view taken along the line AA of FIG.

FIG. 4 is a plan view showing a diesel engine according to another embodiment of the present invention without a head cover.

[Explanation of sign]

 1 Cylinder Body 2 Cylinder Head 3 Head Cover 4 Cylinder 10 Intake Valve 11 Exhaust Valve 12,13 Cam Shaft 17,18 Gear 19 Pulley

Claims (1)

[Claims] 1. A cylinder having a greater number of intake valves and exhaust valves than the other, and a cam shaft for driving the intake valves and a cam shaft for driving the exhaust valves.
In a cycle engine, a crankshaft of the engine is connected to a camshaft having a larger number of drive valves among the two camshafts via a first transmission mechanism, and the camshaft is connected via a second transmission mechanism. A 4-cycle engine connected to the camshaft with the smaller number of drive valves.