JPH0315608A - Valve driving device for multiple cylinder engine - Google Patents

Abstract

PURPOSE:To reduce the number of timing wheels in an engine having a plurality of cylinders radially extending from a crank case by connecting a timing wheel, common in the cylinders, disposed in a crank shaft in association with a wrapping connecting means fixed in one of two cam shafts disposed in each cylinder. CONSTITUTION:In the engine 8 of a motor bicycle, a crank shaft 14 supported in a crank case 15 is disposed in a widthwise direction of the motor bicycle. Cylinder holes are lengthwise formed in two-to-one correspondence to cylinders around the crank shaft 14, each having a piston connected to the crank shaft 14 via a connecting rod. A timing wheel 41 is fixed in the crank shaft 14, and further, a cam sprocket 42 serving as a wrapping connecting means is fixingly disposed in a suction cam shaft 36, which is one of two cam shafts 36, 38 ar ranged in each top of the cylinders, so as to be connected in association with the timing wheel 41 through a cam chain 45. The cam shafts 36, 38 are con nected by a second chain 49 wound around cam sprockets 48, 43 each disposed therein.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an overhead cam type four-stroke multi-cylinder engine suitable as a vehicle engine.

In particular, V-type engines, horizontally opposed engines, etc., have at least two cylinders extending radially from the crankbox,
It also concerns the improvement of an engine in which two camshafts are installed at the head of each cylinder, and the gears installed on the crankshaft.
The purpose is to simplify the structure around the timing wheel for driving the valve train cam, such as a chain wheel, to shorten the axial length of the crankshaft, and to make the cylinder head smaller. It is.

Generally, a four-stroke engine with cylinders extending in different directions from the crankbox requires a timing wheel and a winding transmission means such as a chain or a toothed belt that meshes with the timing wheel for each direction in which each cylinder extends. However, if multiple timing wheels are installed on the crankshaft or multiple wrapped transmission means are used, the axial length of the crankshaft becomes larger, the engine becomes larger, and the weight of the vehicle increases. ,
It is often unsuitable for use in vehicles due to reduced steering performance.

[Prior art]

Conventionally, the layout of a timing chain in a ■-type engine in which two camshafts are arranged at the head of each cylinder is known, for example, from Utility Model Application No. 57-176604.
Since a plurality of timing wheels are used on the crankshaft, it is still insufficient to shorten the axial length of the crankshaft. Furthermore, in order to drive these two camshafts, each camshaft is provided with a winding transmission means having an outer diameter approximately twice that of the timing wheel. Since the distance is limited by the outer diameter of the winding transmission means and cannot be made smaller than this outer diameter, it is difficult to make the cylinder head small.

[Summary of the invention]

This invention is based on the above-mentioned object, and is an attempt to improve the conventional valve drive device, and includes a plurality of cylinders extending radially from a central crank box that pivotally supports a crankshaft, and the head of each cylinder. In a four-stroke engine with two camshafts arranged in each cylinder, a common timing wheel is provided on the crankshaft for each cylinder that drives the camshaft of each cylinder, and this timing wheel and the two camshafts of each cylinder are connected to each other. The two camshafts of each cylinder are provided with a wrap-around transmission means that connects the two camshafts, and the two camshafts of each cylinder are linked with a timing wheel. be.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments. 1 is a motorcycle, and a front wheel 4 is supported at the front of a body frame 2 via a front fork 3, and a rear wheel 6 is supported at the rear via a rear fork 5. 7 is a power unit including a horizontally opposed four-stroke engine disposed between the front wheels 4 and the rear wheels 6. This power unit 7 is composed of an engine 8 disposed above and a transmission 9 disposed below. l1
is a radiator for engine water cooling, 12 is a fuel tank, 1
3 is a seat for a passenger.

The engine 8 constituting the power unit 7 has a crankshaft 1
4 is disposed facing in a direction perpendicular to the direction of travel of the vehicle, and a crankshaft 14 is supported on the joint surface of a crank box 15 that is divided into front and rear parts.

Cylinder holes 16 each consisting of two cylinders extend in the front and back direction from the crankshaft 15.
Two pistons 17, 17 are fitted in a slidable manner. The piston 17 is connected to the crankshaft 14 by a connecting rod l8, forming a horizontally opposed four-cylinder engine. 20 is the fuel tank 1 from the top of the engine 8
2. A downward ventilation type carburetor 21 with an intake passage extending to the bottom surface.
is provided. 22 is an air purifying box, and 23 is an element. In this specification, the term "cylinder" refers to the smallest unit that functions as an engine, including the cylinder hole 16, piston 17, etc.

The output of the crankshaft l4 is shown in FIGS. 4 and 5.

The rotation of the crankshaft l4 drives the input shaft 27 of the transmission 9 via a gear 24 formed on the crank web, a reduction gear 25 meshing therewith, and a clutch 26. The human power shaft 27 drives an output shaft 28 via a known transmission gear mechanism G, and drives the rear wheel 6 via a drive chain 31 from a chain wheel 30 provided at the end of the output shaft 28 . Reference numeral 32 is a gear that is driven by the cam drum 33 to switch the meshing of the speed change gear mechanism G.

The engine 8 has two camshafts 36 and 38 at the head of each cylinder.
is installed. 35 is a combustion chamber of the engine, which includes the intake passage 20 opened and closed by an intake valve 37 driven by an intake camshaft 36, and an exhaust valve 3 driven by an exhaust camshaft 38.
An exhaust passage 40 opened and closed by 9 is connected thereto.

A timing wheel 4l consisting of a chain wheel is fixed to the crankshaft 14, and a cam, which is a transmission means, is wound around one of the two camshafts disposed at the head of each cylinder, the intake camshaft 36. Sprocket 42 is fixed.

The cam sprocket 42 of each cylinder is connected to one idle wheel 4
A single cam chain 45 is wound through the cam chain 4 and connected to a common timing wheel 41.

46 and 47 are conventionally known chain tensioning means.

Note that the number of teeth of the cam sprocket 42 is twice the number of teeth of the timing wheel 41.

Next, the intake camshaft 36 and the exhaust camshaft 38 are provided with a cam sprocket 48 which is a winding transmission means and has a smaller outer diameter than the cam sprocket 42 and has the same number of teeth.
, 43 are fixed, and a second chain 49 connects them. Reference numeral 51 is an automatic tensioning means for preventing the second chain 49 from loosening as the engine temperature rises, and includes a wax-type temperature-sensitive actuator, which itself is not particularly new.

43 are simultaneously driven at 1/2 the rotation speed of the crankshaft 14, and each camshaft 36, 38 opens and closes each intake/exhaust valve 37, 39. The outer diameter of the timing wheel 41 is determined by the number of teeth of the chain wheel required for strength and processing reasons, and is made as small as possible.
Since it is twice as large as 1, the outer diameter is also almost twice, making it larger.

On the other hand, the other cam sprockets 48 and 43 only drive one camshaft, so the load is small, and the number of teeth is not related to the timing wheel 41, so they are small, as shown in FIG. In addition, the outer diameter can be made smaller than that of the cams brocket 42. Therefore, the cam sprocket 4 is connected and interlocked with the timing wheel 41 at the same time and has an outer diameter approximately twice that of the timing wheel 41.
2 on both the camshafts 36 and 38, it is possible to shorten the distance between the two camshafts.

〔Effect of the invention〕

As described above, the present invention is directed to a four-stroke engine that is equipped with a plurality of cylinders extending radially from a central crank box that pivotally supports a crankshaft, and in which two camshafts are disposed at the heads of each cylinder. A timing wheel common to each cylinder that drives the camshaft of each cylinder is provided on the crankshaft, and this timing wheel is connected to a winding transmission means provided on one of the two camshafts of each cylinder. However, the two camshafts of each cylinder are provided with a winding transmission means that connects the two camshafts, and is interlocked with a timing wheel. Therefore, there is no need to provide several timing wheels on the crankshaft, unlike when a drive mechanism is provided for each of several cylinders arranged separately in the front and rear or in a V-shape, and the overall length of the crankshaft can be shortened. . Furthermore, the outer diameter of the winding transmission means that connects the two camshafts disposed at the head of each cylinder can be reduced, so the distance between the camshafts is shortened, and the can be made small. Therefore, the entire engine is made more compact and at the same time its weight is reduced, making it possible to obtain an engine suitable for use in vehicles.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention. Figure 1 is a side view of the main parts of the motorcycle, Figure 2 is a sectional view of the main parts of the engine, and Figure 3 shows the drive mechanism of the intake and exhaust valves. 4 is a sectional view showing the other side of the engine, and FIG. 5 is a longitudinal sectional view thereof. l4... Crankshaft, l5... Crank box, 36... Intake camshaft, 38... Exhaust camshaft, 4l... Timing wheel, 42, 43, 48...・・Cams brocket (wrapping transmission means)

Claims (1)

[Claims] In a four-stroke engine, a four-stroke engine is equipped with a plurality of cylinders extending radially from a central crank box that supports a crankshaft, and two camshafts are disposed at the head of each cylinder. A common timing wheel is provided for each cylinder that drives the camshaft, and this timing wheel is connected to a winding transmission means provided on one of the two camshafts of each cylinder. A valve drive device for a multi-cylinder engine in which the camshaft is provided with a wrap-around transmission means that connects the camshaft, and is linked to a timing wheel.