JPH0758045B2 - Camshaft drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft drive device for driving an intake camshaft and an exhaust camshaft by a crankshaft of an engine.

[0002]

2. Description of the Related Art Conventionally, an intake valve and an exhaust valve are configured to be opened and closed separately by an intake cam shaft and an exhaust cam shaft,
A so-called double-head cam type engine is known.

In such a camshaft drive device for an engine, it is known that only one of the pair of camshafts is provided with a sprocket that is connected to the crankshaft in order to reduce the diameter of the sprocket provided on the camshaft ( For example, see Japanese Utility Model Laid-Open No. 54-72209).

In the conventional camshaft driving device disclosed in this publication, the power from the crankshaft is transmitted to the midway portion of the exhaust camshaft via the first timing chain, and its first
Power is transmitted from the exhaust cam shaft to the intake cam shaft through a second timing chain that is arranged in parallel with the above timing chain.

[0005]

However, in the above-described conventional camshaft driving device, since the two timing chains are arranged side by side in the middle of the camshaft, the dimension of the engine in the camshaft direction is long. And especially,
In the exhaust cam shaft provided with the sprockets for both timing chains, since both timing chains are arranged side by side, the gap between the first timing chain and the bearing is widened, and the exhaust cam is provided via the first timing chain. The bending stress applied to the shaft becomes large, and it becomes necessary to increase the shaft diameter of the cam shaft.

It is an object of the present invention to provide a camshaft drive device that does not require a long dimension of the engine in the camshaft direction or a large camshaft diameter.

[0007]

A camshaft drive apparatus according to the present invention is a double-headed cam type engine in which a pair of camshafts are pivotally supported by an engine through cam bearings. While connecting one end with an endless transmission band,
Both cam shafts are connected to each other via a power transmission means at a position sandwiching the cam bearing and the cylinder with respect to the endless transmission band.

[0008]

Since the power transmission means is provided at a position sandwiching the cam bearing and the cylinder with respect to the endless transmission band, the endless transmission band and the power transmission means are not aligned in the middle of the cam shaft.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a plan view showing a camshaft driving device according to the present invention, which shows a state in which a cam cover of a diesel engine is removed. FIG. 2 shows II- in FIG.
II is a sectional view taken along line II, FIG. 3 is an enlarged sectional view showing a cylinder head portion of a diesel engine equipped with a camshaft driving apparatus according to the present invention, and FIG. 4 is a sectional view taken along line IV-IV in FIG.

In these drawings, reference numeral 1 denotes an engine body of a diesel engine, which is composed of a cylinder block 2 and a cylinder head 3. 4 is cylinder block 2
The crankshaft is supported by the crankshaft, and the large end of the connecting rod 5 is loosely engaged with the crankpin. 6 is a disposable type oil filter.

An intake branch pipe 7 and an exhaust branch pipe 8 are connected to the cylinder head 3. The intake branch pipe 7 has an intake distribution box 7a and a branch pipe 7b connected to the intake distribution box 7a, and the branch pipe 7b is branched into two for every two intake valves described later. 7
c is an intake air intake of the intake distribution box 7a.

Reference numeral 9 is a fuel injection pump, and 10 is a fuel injection nozzle, and the fuel is pumped from the former to the latter through the fuel pipe 11 at regular time intervals. That is, the gear 12 provided at the end of the fuel injection pump 9 is driven by the crankshaft 4 via the toothed belt 13 together with the valve camshaft described later.

As shown in FIG. 3, the engine body 1 has, at the top of the piston 15, a combustion chamber consisting of a main combustion chamber 16a and a swirl chamber 16b connected to the main combustion chamber 16a through a through hole 17. The lower surface of the cylinder head 3 is flatly cut and a part thereof forms the top surface of the main combustion chamber 16a. Two intake valves 18, 18 and one exhaust valve 19 are provided on the top surface so as to be biased to one side, and the intake ports 20, 20 and the exhaust port 21 are connected through the valves 18, 19 respectively. Are respectively guided to one side and the other side of the engine body 1, and the intake branch pipe 7
And the exhaust branch pipe 8.

A swirl chamber 16b is formed on the lower surface of the cylinder head 3 below the middle of the two intake ports 20, 20. The swirl chamber 16b is located between both intake ports 20 as viewed in the cylinder axis direction as shown in FIG.
It is arranged at a portion on the cylinder side of the intake port 20 when viewed in the camshaft direction.

The swirl chamber 16b is provided with a recess opening on the lower surface of the cylinder head 3, and the recess is provided with the recess 1.
It is formed so as to be covered with the through-hole member 22 having No. As is conventionally known, the through hole member 22 is prevented from rotating by a pin (not shown), the direction of the through hole 17 is fixed, and the cylinder block 2 holds the through hole from below.

The tip of the fuel injection nozzle 10 is opened at the top of the swirl chamber 16b, and the nozzle 10 extends from there to the outside of the engine substantially parallel to the intake ports 20 and 20, and the cylinder head 3 is narrow. It can be attached to the outer side surface.

Reference numeral 23 is a preheating plug that heats the inside of the swirl chamber 16b at the time of cold start of the engine to improve ignitability. In the main combustion chamber 16a in which the through hole 17 is oriented, as shown in FIG. 4, the intake valves 18, 18 and the exhaust valve 1 are provided on the top surface of the piston 15.
9 and a shallow circular recess 24 and 25 and a shallow long groove 26 extending from the through hole 17 toward the recesses 24 and 25 are formed.

The valve rods of the intake valve 18 and the exhaust valve 19 extend upward substantially parallel to the axial direction of the piston 15, and the intake cam shaft 27
And the exhaust cam shaft 28. 29 is double valve 1
The valve lifters 8 and 19 and the valve spring 30 are valve springs.

As shown in FIG. 1, the intake camshaft 27 has a gear 27a fixed to the end of the shaft penetrating the cylinder head 3, and is attached to the crankshaft 4 via the toothed belt 13 wound around the gear 27a. It is connected. The intake cam shaft 27 has a gear 31 fixed to the end opposite to the gear 27a, and is geared to an exhaust cam shaft 28 having a gear 32 fixed to the end of the shaft.

The intake camshaft 27 and the exhaust camshaft 2
8 is a bearing portion of the cylinder head 3 and the cylinder head 3
It is rotatably supported by a bearing member 3a screwed to the. That is, the intake cam shaft 27 and the exhaust cam shaft 28 are connected to each other via gears 31 and 32 as power transmission means at positions where the bearing portion and the cylinder are sandwiched with respect to the toothed belt 13.

In the camshaft driving device thus constructed, when the crankshaft 4 rotates, its power is transmitted to the intake camshaft 27 via the toothed belt 13. When the intake camshaft 27 rotates together with the crankshaft 4, the rotation is transmitted to the exhaust camshaft 28 via the gears 31 and 32, and the exhaust camshaft 28 is rotationally driven in the opposite direction to the intake camshaft 27. It will be.

Reference numeral 33 in FIG. 3 denotes a breather in the crank chamber.

Next, the operation of this embodiment will be described. When the engine is started, the rotation of the crankshaft 4 causes the toothed belt 1 to rotate.
3 through the fuel injection pump 10 and the two cam shafts 27, 2
8. As a result, in the intake stroke in which the piston 15 descends, the two intake valves 18 simultaneously open and close,
A large amount of air is introduced into the main combustion chamber 16a and is subsequently adiabatically compressed by the piston 15.

At this time, part of the heat reaches the inside of the swirl chamber 16b through the through hole 17, and high heat of about 1500 ° C. is generated at the end of the compression stroke. From this state, when a predetermined amount of fuel corresponding to the load is sprayed into the swirl chamber 16b through the fuel injection nozzle 10, combustion is instantly started, and the combustion gas is ejected to the main combustion chamber 16a through the through hole 17, Therefore, the combustion is completed.

[0025]

As described above, in the camshaft drive device according to the present invention, the crankshaft and one end of one camshaft are connected by the endless transmission band, and both camshafts are connected to the endless transmission band. On the other hand, since the cam bearing and the cylinder are connected to each other via the power transmission means at a position sandwiched between them, the endless transmission belt and the power transmission means do not line up in the middle of the camshaft. You can prevent it from becoming long.

Further, since the power transmission means for connecting both cam shafts is provided at the position where the cam bearing is sandwiched with respect to the endless transmission band, the interval between the cam bearing and the endless transmission band can be shortened, and the endless transmission band is interposed. As a result, the bending stress applied to one of the cam shafts can be reduced to reduce the diameter of the cam shaft.

[Brief description of drawings]

FIG. 1 is a plan view showing a drive device for a camshaft according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is an enlarged sectional view showing a cylinder head portion of a diesel engine equipped with a camshaft driving device according to the present invention.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

[Explanation of symbols]

 2 Cylinder Block 3 Cylinder Head 3a Bearing Member 4 Crank Shaft 13 Toothed Belt 18 Intake Valve 19 Exhaust Valve 27 Intake Cam Shaft 28 Exhaust Cam Shaft 31 Gear 32 Gear

Claims (1)

[Claims] 1. In a double-headed cam type engine in which a pair of cam shafts are pivotally supported by the engine via cam bearings, a crank shaft and one end of one cam shaft are connected by an endless transmission band, and both cam shafts are connected. A drive device for a camshaft, characterized in that the endless transmission belt is connected to each other through a power transmission means at a position sandwiching a cam bearing and a cylinder.