JPH10238404A - Ohc engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assuredly prevent a timing drive member from falling by providing a protruding part in one main bearing near the timing drive member of main bearings for supporting a crankshaft, extending the protruding part below the timing drive member in the crankshaft side and operating it as a falling preventing member of the timing drive member. SOLUTION: A power unit 40 comprising an engine and a transmission mounted on a motorcycle is provided with main bearings 41c to 41h provided on an upper case 41 and main bearings 42c to 42h provided on a lower case 42 in order to rotatably support a crankshaft 57 on a crank case 43. A timing sprocket 57e is provided in the intermediate part of the crankshaft 57 and a camshaft 65 is rotated through a timing chain 68 as a timing drive member wound thereon. In this case, a protruding part 42j as a falling preventing member is provided in the side of the main bearing 42f of the lower case 42 so that the timing chain 68 is prevented fron falling from the timing sprocket 57e upon assembly of the power unit 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in an OHC engine. The OHC engine is an abbreviation for an overhead camshaft engine.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a conventional OHC engine. An engine 100 has a plurality of main bearings 101a, 101b, 101c, 101d, 101 provided on a crankcase 103 composed of an upper case 101 and a lower case 102.
e, 101f, 102a, 102b, 102c, 102
d, 102e, 102f (hereinafter, when expressing the whole main bearing, it is described as "main bearings 101a-f, 102a-f")
A crankshaft 104 rotatably supported by these main bearings 101a to 101f and 102a to 102f;
4, a timing sprocket 105 provided at an intermediate portion of
Camshaft 10 rotatably mounted on cylinder head 106
7, a cam sprocket 108 provided at an intermediate portion of the cam shaft 107, a timing chain 109 extending over the cam sprocket 108 and the timing sprocket 105, and a timing chain 109 from the timing sprocket 105 when the engine 100 is assembled. In order to prevent the main bearing 10 from coming off,
An upright portion 111 is provided between 2c and 102d. The upright part 111 has the upper end of the timing sprocket 1
It is close to the timing chain 109 multiplied by 05.

[0003]

In the above prior art, when the crankcase 103 provided with the main bearings 101a-f and 102a-f is manufactured by a casting method, a portion where the upright portion 111 is formed during casting is formed. In addition, the wall thickness becomes small, distortion due to heat from the molten metal is easily generated, and the life of the mold is shortened. SUMMARY OF THE INVENTION It is an object of the present invention to provide an OHC engine capable of preventing a timing chain from falling from a timing sprocket of a crankshaft and extending a life of a mold for a crankcase.

[0004]

In order to achieve the above object, according to a first aspect of the present invention, a projection is provided on one of the main bearings supporting a crankshaft, which is close to a timing drive member.
This projection extends below the timing drive member on the crankshaft side to serve as a fall prevention member for the timing drive member. It is possible to prevent the fall of the timing drive member, not to impair the workability at the time of assembly, and to provide a fall prevention member for the timing drive member independently between the main bearings of the crankshaft. There is no thin portion in the crankcase mold, no distortion due to heat or the like occurs, and the life of the mold can be extended.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a side view of a motorcycle according to the present invention.
A front fork 4 attached to the head pipe 3 of the body frame 2, a front wheel 5 and a front fender 6 attached to the front fork 4, a handle 7 connected to the front fork 4, and an upper front portion of the body frame 2 A fuel tank 8 mounted so as to straddle the vehicle, a seat 9 (double seat having a driver's seat and a passenger seat) mounted on the rear upper portion of the body frame 2 and a cradle space surrounded by each pipe of the body frame 2 An engine 10 and a transmission 10a disposed therein, an air cleaner 11 disposed behind the cradle space and below the seat 9, a carburetor 12 connected between the air cleaner 11, an intake port of the engine 10, and an engine 10 An exhaust pipe 13, a collecting chamber 14, and a silencer 15 connected to an exhaust port of
A radiator 16 disposed in front of the engine 10, a swing arm 17 attached to a rear portion of the vehicle body frame 2 via a pivot 2a, a rear suspension 18 having a rear end of the swing arm 17 suspended on the vehicle body frame 2,
And a rear wheel 19 attached to the swing arm 17. In the figure, 21 is a step bracket, 22 is a stand, 2
3 is a rear grab rail.

FIG. 2 is a plan view of the motorcycle according to the present invention. The rear side portions of the body frame 2 shown in FIG. 1 are covered with side covers 26 and 26 and auxiliary side covers 27 and 27, A rear fender 28 is put on the rear fender 28 and a rear cowl 29 is put on the rear fender 28. In the figure, 31 is a headlamp, 32 and 32 are front turn signals, 33 and 34 are meters, 35 is a tail lamp,
36, 36 are rear turn signals, and 37, 37 are steps.

FIG. 3 is a side view of a main part of the motorcycle according to the present invention, showing a power unit 40 composed of an engine 10 and a transmission 10a. The power unit 40 includes a crankcase 43 including an upper case 41 and a lower case 42.
A cylinder block 44 attached to the upper front part of the crankcase 43, a cylinder head 45 attached to the upper part of the cylinder block 44, and a head cover 46 covering the upper part of the cylinder head 45. The front engine hanger 41a, the rear upper engine hanger 41b and the rear lower engine hanger 42a are attached to the vehicle body frame 2. 47 is a starter motor, 48 is an AC generator, 51 is a water pump, 52 is an oil filter element, and 53 is an oil pan.

FIG. 4 is a front view of a power unit according to the present invention. A breather chamber 55 for returning blow-by to the intake system is provided in the head cover 46, and the exhaust pipes 13 for each cylinder are provided in front of the cylinder head 45 for each cylinder. The same applies to the following.), Indicating that the oil filter element 52 has been attached to the front center of the crankcase 43.

FIG. 5 is a sectional view taken along line 5-5 in FIG.
The main bearings 41c, 41d, 41e, 41f, 41g, 41h provided on the upper case 41 for rotatably supporting the motor 7.
And the main bearings 42c, 42d, 42e provided in the lower case,
42f, 42g, 42h, connecting rods 58 having one ends rotatably connected to crank pins 57a, 57b, 57c, 57d of the crankshaft 57, and connecting rods 58 ...
Are connected to the other end via piston pins 61 (the other three are omitted).

The crankshaft 57 has a timing sprocket 57e for driving a camshaft described later and an oil pump drive sprocket 57f for driving an oil pump described later in an intermediate portion. Piston 62 ...
Is the cylinder liner 6 fitted to the cylinder block 44.
3 move vertically.

The power unit 40 includes an exhaust camshaft 65 provided on the cylinder head 45 and the camshaft 6.
5, the rocker arms 66 ...
An exhaust valve 67 that opens and closes through the camshaft 65
And a timing chain 68 which is a timing drive member which extends from the cam sprocket 65b and the cam sprocket of the intake camshaft shown in FIG. 6 to the timing sprocket 57e of the crankshaft 57. Consists of In addition, 69 is a balance axis. Note that the intake valve is omitted.

The lower case 42 has a projection 42j projecting laterally from the main bearing 42f. The protruding portion 42j has its upper end positioned below the timing chain 68 on the timing sprocket 57e of the crankshaft 57, and prevents the timing chain 68 from dropping from the timing sprocket 57e when the power unit 40 is assembled. Things.

Here, the engine 1 of the power unit 40
The procedure for assembling 0 will be described below in order. The cylinder block 44 is mounted on the upper case 41. Main bearings 41c, 41d, 41e, 41 of the upper case 41
The crankshaft 57 is temporarily fixed to f, 41g, and 41h. A connecting rod 58 to which a piston 62 is connected from the upper surface side of the cylinder block 44 is inserted into the inner surface of the cylinder liner 63 from the lower end, and the lower end of the connecting rod 58 is connected to the crankshaft 57.
Connect to

A cylinder head 45 to which an exhaust valve 67 and an intake valve (not shown) have been previously mounted is mounted on the upper part of the cylinder block 44. A timing chain 68 having both ends not connected to a timing sprocket 57e of the crankshaft 57 is hung.
From the outside. The lower case 42 is attached to the upper case 41.

A rocker arm 66 is attached to the cylinder head 45.
And the camshaft 65 is mounted. Both ends of the timing chain 68 are connected while the timing chain 68 is hung on the cam sprocket 65b of the cam shaft 65. The head cover 46 is mounted on the upper part of the cylinder head 45. Thus, the assembly of the engine 10 is completed.

By providing the projection 42j on the main bearing 42f of the present invention, the timing chain 68 does not come off from the timing sprocket 57e of the crankshaft 57 after the assembly of the timing chain 68 described in the above assembly procedure. In this case, the lower case 42 does not need to be attached or detached when it comes off, and the workability is not impaired. In addition, lower case 4
When casting 2 is manufactured by a casting method, compared with the case where a fall prevention member of the timing chain 68 is provided independently between the main bearings 42e and 42f of the crankshaft 57, a portion having a small thickness is not formed in the mold, and As a result, the life of the mold can be extended.

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 4, showing the cam sprocket 65b of the cam shaft 65 for exhaust, the cam sprocket 72b of the cam shaft 72 for intake, and the crank shaft 57 mounted on the cylinder head 45. The timing chain 68 is wrapped around the timing sprocket 57e, and the projection 42j provided on the lower case 42 is attached to the timing sprocket 5e.
7e, the chain guide 73 is brought close to the timing chain 68 between the cam sprocket 65b and the timing sprocket 57e, and the timing chain 68 between the cam sprocket 72b and the timing sprocket 57e.
Shows that the movable chain guide 74 is pressed by the chain tensioner 75 to bring the upper chain guide 76 close to the cam chain 68 between the cam sprockets 65b and 72b.

The crankshaft 57 rotates in the direction of the arrow shown in FIG.
Then, the camshaft 72 for intake is rotated. Crankshaft 57
When the cam sprocket 65b rotates between the cam sprocket 65b and the timing sprocket 57e,
The timing chain 68 between the cam sprockets 72b and the timing sprocket 57e
The timing chain 68 between them is on the loose side.

The chain guide 73 and the upper chain guide 76 suppress the flapping of the timing chain 68, and the movable chain guide 74 presses the rear surface thereof with the chain tensioner 75 to press the timing chain 68 at a constant pressing force. It is something to stretch.

Here, reference numeral 77 denotes a breather plate which is a partition for forming the breather chamber 55, and also functions as a member for fixing the upper chain guide 76. An oil pump 81 supplies oil to each part of the engine 10 and the transmission 10a, and an oil pump 82 extends between an oil pump drive sprocket 57f (see FIG. 5) and an oil pump driven sprocket (not shown). A drive chain 83 is an oil strainer serving as an oil suction port of an oil pump 81, 84 is a relief valve that opens when the oil passage reaches a predetermined pressure, and 85 is a main oil passage extending in the direction of the crankshaft 57. A gallery 86 is an oil path pipe which is an oil passage to the transmission 10a side, 87 is an upper oil path member for branching the oil passage, 88 and 89 are a main shaft for shifting the rotation transmitted from the crankshaft 57 and The drive shaft 91 is a fork member for moving a gear during shifting.

In the present invention, the projection 42j is connected to the main bearing 42.
f, but is not limited to this, and bridges the main bearing 42e and the main bearing 42f,
It may be formed so as to fill the space between 2e and 42f.

[0022]

According to the present invention, the following effects are exhibited by the above configuration. In the OHC engine according to the first aspect, of the main bearings supporting the crankshaft, a projection is provided on one main bearing close to the timing drive member, and the projection is extended below the timing drive member on the crankshaft side. The timing adjustment drive member has been made a fall prevention member, which prevents the timing adjustment drive member from dropping and does not impair the workability during assembly, and independently adjusts the timing between the main bearings of the crankshaft. As compared with the case where the fall prevention member of the driving member is provided, the crankcase mold has no thin portion, and does not generate distortion due to heat or the like, so that the life of the mold can be extended.

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle according to the present invention.

FIG. 2 is a plan view of the motorcycle according to the present invention.

FIG. 3 is a side view of a main part of the motorcycle according to the present invention.

FIG. 4 is a front view of a power unit according to the present invention.

FIG. 5 is a sectional view taken along line 5-5 in FIG. 3;

FIG. 6 is a sectional view taken along line 6-6 in FIG. 4;

FIG. 7 is a cross-sectional view of a conventional OHC engine.

[Explanation of symbols]

Reference numeral 10: engine, 42f: main bearing, 42j: projection, 43
... Crank case, 45 ... Cylinder head, 57 ... Crank shaft, 65, 72 ... Cam shaft, 68 ... Time drive member (timing chain).

Claims (1)

[Claims] In an OHC engine in which a timing drive member such as a timing chain is laid over a camshaft provided on a cylinder head and a crankshaft provided on a crankcase, of the main bearings supporting the crankshaft, A projection is provided on one main bearing close to the timing drive member, and the projection extends below the timing drive member on the crankshaft side to serve as a fall prevention member for the timing drive member. O
HC engine.