JPH0270908A - One overhead camshaft type engine - Google Patents

Abstract

PURPOSE:To reduce the length of a camshaft so as to increase the degree of freedom in designing bearing arrangement and increase rigidity, by allowing the cam of a locker arm to be included in the projection shape of the cam of a valve lifter and forming both cams to be superposed on the diameter of the valve lifter. CONSTITUTION:One edge of a locker are 52 makes sliding contact with an exhaust side cam 40b positioned outside the intake side cam 40a of a camshaft 40, and the other edge makes contact with the upper edge of an exhaust valve 43. The shape of the exhaust side cam 40b is determined so as to be set within the projection shape of the intake side cam 40a in the direction towards the camshaft 40. Therefore, both cams 40a and 40b can be set close to each other or can be formed into one common cam depending upon the case, and the length of the camshaft can be reduced, or the degree of freedom in the bearing arrangement of the camshaft is increased. Since, in particular, the restriction in the arrangement of a cam for locker arm can be reduced, the shape of the locker arm is made simple, and the shape which is advantageous in rigidity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a single overhead camshaft engine in which a single camshaft opens and closes a plurality of intake valves and exhaust valves per cylinder.

(Background of the Invention) A four-valve engine is known in which each cylinder has two intake valves and two exhaust valves. In this case, conventionally, two camshafts were arranged parallel to each other on both sides of the cylinder center.
This is a so-called double overhead camshaft (DOHC) system in which each camshaft directly opens and closes two intake valves and two exhaust valves. However, in this case, a problem arises in that the engine becomes larger.

In addition, there is one camshaft, and this camshaft provides two suctions (
It has also been proposed to directly open and close the exhaust (exhaust) valve and open and close the other two exhaust (intake) valves via rocker arms.

However, in this case, since the valve that is directly opened and closed by the camshaft has a valve lifter, the cam that presses the rocker arm must be placed away from the valve lifter so as not to interfere with the valve lifter.

That is, the cam for pressing the rocker arm must not overlap the diameter of the valve lifter when viewed from the sliding direction of the valve lifter. As a result, the distance between each cam becomes wider, the camshaft becomes longer, the degree of freedom in designing the camshaft bearing arrangement is reduced, and the shape of the rocker arm becomes complicated, which is disadvantageous in terms of rigidity. Ta.

(Objective of the Invention) The present invention was made in view of the above circumstances, and it is possible to shorten the camshaft, increase the degree of freedom in designing the bearing arrangement of the camshaft, and simplify the rocker arm shape to increase its rigidity. The object of the present invention is to provide a single overhead camshaft engine suitable for

(Structure of the Invention) According to the present invention, this purpose is to provide a single camshaft parallel to the crankshaft, an intake/exhaust valve that is directly opened and closed by sandwiching a valve lifter with this camshaft, and a rocker arm that is operated by this camshaft. and an exhaust/intake valve that is opened and closed through the valve lifter, and the cam that presses the rocker arm is included in the projected shape of the cam that presses the valve lifter in the cam axis direction, and both of the cams overlap the diameter of the valve lifter. This is achieved by a single overhead camshaft engine featuring the following features:

(Example) Fig. 1 is an overall schematic diagram of a type 6-cylinder engine according to an embodiment of the present invention, Fig. 2 is a plan view showing the left bank valve chamber, and Figs. 3.4.5 are III-III in Figure 2
FIG. 6 is a bottom view of the cylinder head to show the valve arrangement.

In Figure 1, the engine consists of a pair of banks 10 forming a roughly ■ shape.
．． 10, and each bank 10 has a cylinder ladder head 14 and a head cover 16 attached to a cylinder block 12 that is approximately pentagonal in front view. The cylinders 18.18 of both banks 10.10 form a 90° angle, and the pistons 20.20 of the cylinders in each bank 10.10 that form a pair with each other are connected to the crankshaft 24 with a phase difference of 30''.
a and 24b by connecting rods 26 and 26, respectively. In this figure, the crankshaft 22 rotates counterclockwise. Each bank 1O110 has both banks 10.1
The intake pipe 28 is arranged on the V-shaped valley side formed between 0 and 0.
are connected, and an exhaust pipe 30.30 is connected to the outer surface of each bank 10.10. 31 is an oil pan.

Next, the cylinder head 14 will be explained. Both banks 10.
When the ten camshafts 40 all rotate counterclockwise in FIG. 1, the invention applies to the left bank. Therefore, the cylinder head 14 of the left bank 10 will be explained below. If the camshaft 40 of the left bank rotates counterclockwise and the camshaft 40 of the right bank rotates clockwise, the present invention is of course applicable to the camshafts of both banks.

The cylinder head 14 has cylinder 1 for three cylinders.
8 are arranged in parallel to the crankshaft 22, and each cylinder has an ignition plug 32 arranged near the cylinder center axis A, and two exhaust valves 3 arranged in parallel on the crankshaft 22 with the ignition plug 32 in between.
4.34 and plane B (including these exhaust valves 34.34)
4), a pair of intake valves 36, 36 are provided at the valley sides of the V-shape. Therefore, the combustion chamber 38 is
As shown in the figure, the two exhaust valves 34 have a bathtub shape that is long in the direction of the crankshaft 22, and a large squish area C is formed on the opposite side of the intake valve 36 across the plane B.
．． 34 is approximately parallel to and close to the cylinder central axis A, and plane D (containing the two intake valves 36, 36)
Fig. 4) is largely tilted toward the valley side of the v-shape with respect to the central axis A of the shilling, and a v-shape is formed by both palm faces B and D.

A valve train that opens and closes these exhaust valves 34 and intake valves 36 is housed in a valve train chamber formed between the cylinder head 14 and the head cover 16.

40 is one camshaft parallel to the crankshaft 22, the center of which is on a plane that includes the intake valve 36.36, and directly presses the valve lifter 42.42 of the intake valve 36.36 to lift the intake valve. 36.36 are opened and closed in the same phase. 44 is a rocker shaft located between the side planes B and D and parallel to the camshaft 40.

The split plane between the head cover 16 and the cylinder head 14 is parallel to the split plane between the cylinder head 14 and the cylinder block 12, and the cam shaft 40 and rocker shaft 44 are parallel to the split plane between the head cover 16 and the cylinder head 14. located on the surface. Both ends of the camshaft 40 and the rocker shaft 44 are held between the split surfaces of the cylinder head 14 and the head cover 16, and are held between the cylinder head 14 and the cap 46 above the center of each cylinder. This cap 46 is attached to the cylinder head by a pair of bolts 48 and 48 that sandwich the camshaft 40 and a bolt 50 that passes through the rocker shaft 44.
It is fixed at 4. A pair of rocker arms 52 and 52 are held on the rocker shaft 44 with a cap 46 in between, and one end of these rocker arms 52 is attached to the intake side cam 40a of the camshaft 40.
, 40a, and the other end contacts the upper end of the exhaust valve 34, 34. Note that the cam shape of the exhaust side cam 40b is determined so that it fits within the projected shape of the intake side cam 40a in the direction of the camshaft 40. For example, when both cams 40a and 40b are installed in the same phase, the camshaft 40 is rotated counterclockwise in FIG. The angle θ made with respect to
Set to . Further, both cams 40a and 40b are close to each other as shown in FIG. 2, and are positioned so as to overlap the diameter of the valve lifter 42.

Reference numeral 54 designates an attachment/detachment hole for the ignition plug 32. The lower end of the metal pipe is press-fitted into the cylinder head 14, and the upper end is inserted into the head cover 1.
6, and the plug cord is connected to the spark plug 32 by inserting the plug cap 56 into the opening formed in the head cover 16. An O-ring is attached to the outer periphery of the upper end of the attachment/detachment hole 54, and this O-ring is in close contact with the inner circumferential surface of the fitting hole on the head cover 16 side to ensure liquid tightness of the valve chamber. Reference numeral 58 designates an electromagnetic fuel injection valve, which is connected to each intake valve 36 .
Gasoline fuel is injected toward the vicinity of the branch to 36. A clip 6 made of metal or resin is attached to the rocker shaft 44 to restrict movement of the rocker arm 52 in the axial direction.
2 is installed. That is, this clip 62 is located between both ends of the rocker shaft 44 and each cylinder.

The cylinder head 14 with the valve mechanism preassembled in this manner is fixed to the cylinder block 12 by a plurality of head bolts 64 and 66. These head bolts 64
．． 66 is a hexagon socket bolt, which is attached to the cylinder head 1.
4 and between each cylinder. The head bolt 64 passes through a flange portion 14a that protrudes outward from the exhaust valve 34 side of the cylinder head 14, and is screwed onto the cylinder head 14. The head bolt 66 is attached to the camshaft 40 and the rocker shaft 44.
Located below between. In this embodiment, this bolt 6
6 interferes with the rocker shaft 44 when it is attached or detached, so a notch 44a shown in FIG. 2.5 is formed in the rocker shaft 44. Therefore, once the clip 62 is removed, the bolt 66 can be installed or removed using an Allen key driver.

As mentioned above, the present invention can be applied to the right bank if the camshaft 40 is rotated clockwise, but the present invention cannot be applied to the right bank when the camshaft 40 is rotated counterclockwise. It can be of conventional construction.

In this embodiment, since the spark plug 32 is located between the exhaust valves 34, 34, the exhaust valves 34, 34 are separated from each other, and the cooling performance of the cylinder head 14 is improved. Also exhaust valve 3
The heat around squish area C is evenly transmitted to squish area C, which moderately warms the air-fuel mixture sandwiched therein, increases its combustion speed, and suppresses the occurrence of knocking due to abnormal combustion.

FIG. 7 is a diagram showing the valve arrangement of another embodiment, in which the ignition plug 3
Intake valves 36A and 36A are arranged with 2 in between. According to this embodiment, since the intake valves 36A and 36A are separated from each other, a decrease in intake efficiency due to interference between intakes in the combustion chamber is less likely to occur, and the diameter of the intake valve 36A is reasonably larger than that of the exhaust valve 34A. Can be set, cylinder 1
8 circular spaces can be used effectively.

FIG. 8 is a plan view of a cylinder head of still another embodiment. This embodiment is different from the cams 40a and 4 in the previous embodiment.
A camshaft 140 with one 0b is used. In other words, the cam 140a in this case is the exhaust/intake valve 34.36.
This cam 140a presses the valve lifter 42 and also presses the rocker arm 52. Here, by setting θ=120° as in the case shown in FIG.
It can be opened and closed with a phase delay of 20 degrees, making it possible to obtain ideal opening and closing timing. In FIG. 8, the same parts as in FIG. 2 are given the same reference numerals, so their description will not be repeated.

According to this embodiment, since the cam 140a is common to the intake and exhaust valves, the number of man-hours required for machining the camshaft 140 is reduced, and the camshaft can also be made shorter, thereby increasing the degree of freedom in bearing arrangement.

In each of the above embodiments, the present invention is applied to a four-valve engine having two intake valves and two exhaust valves, but the present invention is not limited to this, and the present invention is applied to a four-valve engine having two intake valves and one exhaust valve. It is also applicable to a three-valve engine, a two-valve engine, a five-valve engine, etc., each having two exhaust valves, and the present invention includes these.

Further, the present invention can be applied not only to type 1 engines, but also to in-line multi-cylinder engines, and includes these.

(Effects of the Invention) As described above, the present invention is such that the projected shape of the cam that presses the valve lifter in the cam axis direction includes the cam that presses the rocker arm, so that both cams overlap the diameter of the valve lifter. Because of this, it is possible to have both cams close to each other, or in some cases to use a single cam in common, which shortens the camshaft and increases the degree of freedom in arranging the bearings of the camshaft.

In addition, since there are fewer restrictions on the arrangement of the rocker arm cam, it is possible to simplify the shape of the rocker arm and make it advantageous in terms of its rigidity.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram of a type 6-cylinder engine according to an embodiment of the present invention, Fig. 2 is a plan view showing the left bank valve chamber, and Figs. III-III
FIG. 6 is a bottom view of the cylinder head showing the valve arrangement. FIG. 7 is a diagram showing the valve arrangement of another embodiment, and FIG. 8 is a plan view of a cylinder head of still another embodiment. 14... Cylinder head, 16... Head cover 32... Spark plug, 34. 34A... Exhaust valve, 36.
36A... Intake valve, 40.140... Camshaft, 40a, 40b, 140 a-cam, 42... Valve lifter, 44... Rocker shaft, 52... Rocker arm. Patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Claims] It is equipped with one camshaft parallel to the crankshaft, an intake/exhaust valve that is opened and closed directly by this camshaft by sandwiching a valve lifter, and an exhaust/intake valve that is opened and closed by this camshaft via a rocker arm. A single overhead camshaft engine, characterized in that the projected shape of the cam that presses the valve lifter in the camshaft direction includes the cam that presses the rocker arm, and that both of the cams overlap the diameter of the valve lifter.