JPH02221613A - Valve system of four-cycle engine - Google Patents

Abstract

PURPOSE:To enhance the engine output within a broad rotating speed region by rotating a rocker shaft provided with an eccentric large-diameter portion through predetermined degrees so as to put a second rocker arm in a vertical movement to select a cam profile from two kinds of cams. CONSTITUTION:Two rocker arms 5, 6 capable of oscillating about a rocker shaft 7 are arranged beneath a cam shaft 4 having a low-speed rotation cam 2 and a high-speed rotation cam 3 formed thereon. The first rocker arm 5 is arranged beneath the low speed rotation cam 2, and its ends 5b, 5c fork into two branches which are made to abut to the respective head portions of valve stems 8, 9. The second rocker arm 6 is arranged beneath the high-speed rotation cam 3 and its end 6b is coupled to the upper end face 5d of the rocker arm 5. An eccentric large-diameter portion 10 is formed on the rocker shaft 7 and the rocker shaft 7 is rotated through predetermined degrees by rotating means so that the high-speed rotation cam 3 and the second rocker arm 6 are put in or released from abutting state to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a valve train for driving intake and exhaust valves of a four-stroke engine.

[Conventional technology]

Generally, in a four-stroke engine installed in vehicles such as automobiles and motorcycles, intake and exhaust valves are arranged above the combustion chamber, and the valve train is equipped with a camshaft to operate the intake and exhaust valves. There is. When this camshaft is rotated by the power of the engine, the intake and exhaust valves are moved up and down at a predetermined timing by a cam having a unique cam profile formed on the camshaft to suck in moisture and exhaust combustion gas.

Note that in the conventional valve train described above, each of the intake and exhaust valves is always operated by a cam with the same cam profile, so the opening and closing of each valve is set according to the engine speed. The lift ω of the valve, which is moved up and down by the timing and rotation of the cam, remains constant without fluctuation.

[Problem to be solved by the invention]

By the way, the above-mentioned 4 devices installed in vehicles such as motorcycles
Cycle engines are required to obtain high output within a wide rotation speed range from low rotation speeds to medium and high rotation speed regions, that is, to obtain a wide power band.

However, in the conventional valve train described above, each of the intake and exhaust valves is always operated by a cam having the same cam profile, so the opening/closing timing of each valve and the lift amount of the valve are always constant without fluctuation. Therefore, the output characteristics of the engine are generally limited by the cam profile of the cam that operates the valve, and the output characteristics have a peak value in a specific engine speed range. It was not possible to obtain even higher output over a wide rotation speed range.

In view of the above-mentioned circumstances, it is an object of the present invention to provide a valve operating system for a four-cycle engine that improves output within a wide rotation speed range from a low rotation speed range to a medium/high rotation speed range.

[Means to solve the problem]

In order to achieve the above-mentioned problems, the present invention provides a camshaft in which two types of cams having different cam profiles are formed adjacent to each other, and the cam lift amount of one cam is larger than that of the other cam; A first rocker arm is disposed on the side of the cam with a smaller cam lift among the cams formed on the camshaft, and directly contacts the valve head that opens and closes the combustion chamber; Among them, the first rocker arm is disposed on the cam side with a larger cam lift and is located further away from the position where the first rocker arm directly contacts the valve head, with the rocker shaft supporting the rocker arm at least as the center. a second rocker arm that engages with the upper surface of the first rocker arm; a second rocker arm that is rotatably supported and is fitted into each support portion of the first and second rocker arms; The rocker shaft is provided with an eccentric large-diameter portion having a larger diameter than other portions and whose axis is offset from the axis of the other portions in a portion to be inserted into the support portion of the arm, and the rocker shaft By rotating a predetermined angle, the eccentric large-diameter portion moves the support portion of the second rocker arm downward relative to the support portion of the first rocker arm, and the cam lift amount is large. The contact between the cam and the second rocker arm is released, the cam with the small cam lift amount is brought into contact with the first rocker arm, and the valve is made to follow the cam profile of the cam with the small cam lift i. and by rotating the rocker shaft by a predetermined angle, the eccentric large diameter portion raises the support portion of the second rocker arm to a position equivalent to the support portion of the first rocker arm; The contact between the cam with a small cam lift amount and the first rocker arm is released, the cam with a large cam lift amount is brought into contact with the second rocker arm, and the valve is connected to the cam with a large cam lift amount. It operates by following the cam profile.

[Effect]

According to the above-mentioned valve train, the cam profile of the cam that operates the valves can be selected from two types according to each rotation range of the engine, so the opening/closing timing of each valve and the lift amount of the valve can be adjusted depending on the engine rotation. It can be set to the optimal value depending on the number range.

〔Example〕

Hereinafter, one embodiment of a valve train according to the present invention will be described in detail.

FIG. 1 is a conceptual perspective view of a main part showing a valve train 8 and a valve train 1 according to the present invention. Note that this valve gear [1] is provided at two locations for each cylinder, one on the intake valve side and one on the exhaust valve side.

This valve train 1 includes a camshaft 4 in which two types of cams 2.3 having different cam profiles are formed adjacent to each other, and first and second rocker arms 5.6 disposed below the camshaft 4. and a rocker shaft 7 which is fitted into each support portion 5a, 5a of each rocker arm 5.6 and rotatably supported by a bearing portion (not shown).

Among these, the cam 2 formed on the camshaft 4 has a cam profile suitable for improving engine output in the so-called low-speed rotation range, where the cam lift amount is small and the valve opening/closing period is set short. On the other hand, the cam 3 formed adjacent to the cam 2 has a larger cam lift and a longer valve opening/closing period than the cam 2 over the entire circumference, and is symmetrical to the cam 2. In addition, it is a cam (hereinafter referred to as a high-speed rotation cam) that has a cam profile suitable for improving the output of the engine at so-called medium and high speed rotations.

on the other hand. Of the first and second rocker arms 5.6, the first rocker arm 5 is disposed below the low-speed rotation cam 2 formed on the camshaft 4, and its tips 5b and 5c are bifurcated. , is arranged so as to directly contact the head of a valve stem 8.9 of a valve that opens and closes a combustion chamber of an engine (not shown). Also, the adjacent second rocker arm 6
is disposed below the high-speed rotation cam 3 formed on the camshaft 4, and the tip 6b is at least at a distance L1 from the center of the rocker shaft 7 where the first rocker arm 5 directly contacts the valve head. Also far away distance L2
It is disposed so as to engage with the top surface 5d of the tip of the first rocker arm 5, which is located at (11<12).

On the other hand, the rocker shirt l-7, which rotatably supports the first and second rocker arms 5.6, has a diameter larger than that of the other parts of the rocker shaft 7, and has an axis other than the other part. An eccentric large diameter portion 10 is formed eccentrically from the axis of the portion, and this eccentric large diameter portion 10 is fitted into the support portion 6a of the second rocker arm 6. And this eccentric large diameter part 1
゜ indicates the eccentric bush 11 fitted into the rocker shaft 7 and the eccentric bush 11.
and a pin 12 fixed to the rocker shaft 7. As shown in FIG. 2, which is a cutaway plan view of the main part of FIG. Small diameter holes 11a, 7
a is formed, and by driving the pin 12 into this hole 11a17a, the eccentric bush 1
1 and the rocker shaft 7 are fixed to each other.

In FIG. 1, reference numeral 13 indicates a threaded portion for adjusting valve clearance, and reference numeral 14 indicates a valve spring.

Next, the operation of the above-mentioned valve train 1 will be explained, and the configuration will also be explained in more detail.

When the rocker shaft 7 is rotated by a predetermined angle in the low rotation speed range of a four-stroke engine by a rotating means such as a servo motor or a rack/binion (not shown) and stopped at the position shown in FIG. Surface 1 of the eccentric bush 11 furthest from the axis
1b is located at the lowest end, only the support portion 6a of the second rocker arm 6 moves downward relative to the support portion 5a of the first rocker arm 5 and stops there.

According to such a stop position of the rocker shaft 7, only the support part 6a of the second rocker arm 6 moves downward relative to the support part 5a of the first rocker arm 5, so that the position shown in FIG. As shown in Figure 3, which is a sectional view of the main part,
A gap t is formed between the circumferential surface of the 9-speed rotation cam 3 formed on the camshaft 4 and the second rocker arm 6, so that the high-speed rotation cam 3 and the second The contact with the peripheral surface of the rocker arm 6 is released, and the high-speed rotation cam 3 rotates without swinging.

It goes without saying that the outer diameter and eccentricity of the eccentric bush 11 are set to form the above-mentioned gap t.

On the other hand, according to the stop position of the rocker shaft 7 shown in FIG. The first rocker arm 5 and the circumferential surface of the low-speed rotation cam 2 are always in contact with each other, so that when the camshaft 4 rotates at the stop position of the rocker shaft 7 shown in FIG. The stem 8.9 is the cam 2 for low speed rotation.
Since the valve moves up and down following the cam profile, the combustion chamber can be opened and closed at low speed while ensuring suitable valve opening/closing timing and valve lift amount.

On the other hand, the rocker shaft 7 is rotated by a predetermined angle from the position shown in FIG. 1 in the middle/high speed range of the four-cycle engine by the above-mentioned rotation means such as a servo motor (not shown), and the same portion as shown in FIG. When the eccentric bushing 11 is stopped at the position shown in FIG. Only B the support portion 5 of the first rocker arm 5
It ascends to a position equivalent to a and stops there.

According to such a stop position of the rocker shaft 7, only the support portion 6a of the second rocker arm 6 moves upward relative to the support portion 5a of the first rocker arm 5, so that the position shown in FIG. As shown in FIG. 5, which is a side sectional view of a main part, the circumferential surface of the high-speed rotation cam 3 formed on the camshaft 4 comes into contact with the second rocker arm 6.

On the other hand, when the peripheral surface of the high-speed rotation cam 3 formed on the camshaft 4 shown in FIG. 4 comes into contact with the second rocker arm 6, the high-speed rotation cam 3 becomes the low-speed rotation cam The rocker arm 6 is formed to ensure a larger cam lift than the second rocker arm 6, and the tip 6 of the second rocker arm 6
b is disposed to engage with the top surface 5d of the tip of the first rocker arm 5, so when the cam shirt +-4 rotates at the stop position of the rocker shaft 7 shown in FIG. 4, it rotates at a low speed. The cam 2 rotates in an idle state, and the first rocker arm 5 is pushed by the tip 6b of the second rocker arm 6 to operate, so the valve stem 8.9 of the valve that opens and closes the combustion chamber is rotated at the high speed. Rotating cam 3
It will move up and down following the cam profile of
Therefore, the valve opens and closes the combustion chamber while ensuring suitable valve opening/closing timing and valve lift amount at high speed.

Note that when the high-speed rotation cam 3 shown in FIG. It gets blown away due to factors such as collision with the tip 5d,
For this reason, there is a risk that light may become a source of noise, but in that case, as shown in Fig. 6, where the same parts as in Fig.
When a coil spring 20 is interposed between the tip 6b of the rocker arm 6 and the tip 5d of the first rocker arm 5 to connect them to each other, the second rocker arm 6 synchronizes with the movement of the first rocker arm 5. Therefore, the second rocker arm 6 can be moved up and down, thereby eliminating such fraying of the second rocker arm 6.

Note that in order to eliminate fraying of the second rocker arm 6 when the high-speed rotation cam 3 is not operating, a coil whose tips 21a and 21b are bent in opposite directions as shown in the conceptual perspective view of FIG. Using a spring 21, this coil spring 21 is fitted onto the rocker shaft 7 between the first rocker arm 5 and the second rocker arm 6, as shown in FIG. 8, where the same parts as in FIG. Alternatively, the ribs of the second rocker arm 6 may be synchronized with the movement of the first rocker arm 5 by inserting the first and second rocker arms 5.6 between the tip portions 21a and 21b. good.

In the above embodiment, in constructing the eccentric large-diameter portion 1o, as shown in FIG. Although the eccentric bushing 11 and the rocker shaft 7 are made to be in trouble by being driven in and press-fitted, the present invention is not limited to the above embodiment, and the same parts as in FIG. 2 are designated by the same reference numerals. As shown in FIG. 9, the eccentric bush 11 and the rocker shaft 7 have a
The holes 11a and 7a are formed into so-called stupid holes with loose dimensional tolerances, and after the bottle 12 is slidably inserted into the holes 11a and 17a, the eccentric push 11 is
are fitted into the support portion 6a of the second rocker arm 6, and furthermore, a coil-shaped coil is attached to the rocker shaft 7 on one of the bearing portions 31 and 31 that rotatably supports the rocker shaft 7. A thrust spring 32 is disposed, and the urging force of the thrust spring 32 moves the entire first and second rocker arms 5.6 to the other side (the second rocker arm 6
side) to the bearing portion 30 side, thereby positioning the bottle 12 with the inner circumferential wall of the support portion 6a of the second rocker arm 6.
Eccentric shaft 11
The locker shirts 1 to 7 may be connected to each other.

In addition, as in the embodiment shown in FIG. 9, eight holes 11 formed in the eccentric bush 11 and the rocker shaft 7
a, 7a are formed into so-called stupid holes whose dimensional tolerances are loosely controlled, and after the bottle 12 is slidably inserted into the holes 11a and 17a, the eccentric push 11 is
are all fitted into the support part 6a of the second rocker arm 6, and the thrust spring 32 is used to position the bottle 12, and the inner peripheral wall of the support part 6a is used to prevent the bottle 12 from slipping out. Assembling and disassembling the valve gear e11 can be carried out by a simple operation, and since the eight holes 11a and 7a can be so-called stupid holes, which allow for loose management of dimensional tolerances, the dimensional tolerances can be easily managed. Therefore, the manufacturing process of the valve train becomes even simpler.

In each of the above embodiments, the valve train 1 according to the present invention is applied to a so-called 4-valve engine having two valves on the intake and exhaust sides, but the present invention is applicable to the above embodiments. Without limitation, the valve operating device 1 according to the present invention may be applied to the intake and exhaust sides of a so-called two-valve engine having one valve each on the intake and exhaust sides.

Further, in the above embodiment, the eccentric large diameter portion 10 was constituted by the eccentric bush 11 and the bottle 12, but the present invention is not limited to the above embodiment.
The eccentric large diameter portion 10 may be formed integrally with the rocker shaft 7.

Further, in the above embodiment, the present invention is applied to a type of valve mechanism in which a camshaft is disposed above a rocker arm. However, the present invention is of course limited to the above embodiment. Instead, it may be applied to a type of valve mechanism in which a locking arm is further extended in the opposite direction from the side where the valve is installed, and a camshaft is installed below the rocker arm on the extended side. .

In addition to the valve train according to the present invention, there is also a second rocker arm as shown in FIG. 10, in which the same parts as in FIG. 6' end 6't) of the first rocker arm 5'
is closer to the center of the rocker shaft 7 than the distance 111 where it directly contacts the valve head (Ll > L-2)
) The upper end surface 5-d of the first rocker arm 5 located at
It is also conceivable to engage the

By the way, the operational difference between such a valve train and the valve train according to the present application can be explained by the first diagram conceptually showing the arrangement of the first and second rocker arms 5' and 6- shown in FIG.
This can be easily understood by comparing FIG. 1 with FIG. 12, which conceptually shows the arrangement of the first and second rocker arms 5.6 shown in FIG. 4 of the present application.

That is, in the case shown in FIG. 11, the distance L-3 from the center S of the camshaft to the surface of the second rocker arm 6' is narrow, so that the high speed rotation that drives this rocker arm 6' is small. When selecting the shape of the cam for crystal rotation, there are restrictions on the amount of cam lift and cam timing, and for this reason, it is necessary to use the cam 3- for crystal speed rotation, which has a small cam lift and a small cam timing.

On the other hand, for those related to the claimed invention, the 12th
As shown in the figure, since the distance L3 from the center S of the cam shirt 1- to the surface of the second rocker arm 6 can be secured widely, the cam lift is higher than that of the high-speed rotation cam 3' shown in FIG. It is possible to use a high-speed rotation cam 3 with a large color and cam timing, and therefore, in the case of the present invention, it is possible to widen the range of selection of the cam lift amount and cam timing of the high-speed rotation cam to be used. It happens.

In addition, in FIG. 11 and FIG. 12, the symbol R is the axial center of the rocker shaft 7.

Further, in FIGS. 11 and 12, the valve clearances H are set to the same length.

〔Effect of the invention〕

As explained above, in the valve train of the present invention, the cam profile of the cam that operates the valve according to each rotation range of the engine is selected from two types of cams according to the engine rotation speed, and each valve is opened and closed. Since the timing and valve lift amount can be changed to the optimal value according to the engine speed range, the output of the 4-cycle engine is improved within a wide speed range from low speeds to medium and high speeds. I can do it.

Further, in the valve train of the present invention, since the rotational motion of the rocker shaft at the time of cam selection is converted into the vertical motion of the second rocker arm by the eccentric large diameter portion, a large stress is applied to each part when the cam is selected. Therefore, cam selection is performed smoothly.

Furthermore, since the valve train of the present invention is constructed without making any major changes to conventional valve trains, it can be installed on a conventionally shaped cylinder head with minimal machining. Another advantageous effect of implementing the present invention is that the increase in production costs can be kept to a minimum.

Further, in the valve train of the present invention, the position where the second rocker arm engages with the first rocker arm is located further away from the center of the rocker shaft than the position where the first rocker arm directly contacts the valve head. Since the cam is positioned at , it is possible to widen the range of selection of the cam lift amount and cam timing of the cam for high-speed rotation.

[Brief explanation of the drawing]

FIG. 1 is a conceptual perspective view of a valve train according to the present invention, and FIG.
3 is a sectional side view of the main part of FIG. 1, FIG. 4 is a conceptual perspective view showing the operation of the valve train according to the present invention, and FIG. 5 is a cross-sectional view of the main part of FIG. 4 is a sectional side view of the main part, FIG. 6 is a sectional side view of the main part showing a spring that connects the first and second rocker arms, and FIG. 7 is a sectional side view of the main part that shows the spring that connects the first and second rocker arms. A conceptual perspective view showing another embodiment of the spring, FIG. 8 is a fragmentary plan view of the main part showing the state in which the spring shown in FIG. 7 is installed, and FIG. 9 is another embodiment of the valve train according to the present invention. FIG. 10 is a fragmentary plan view of essential parts showing an example, and FIG.
1 and 12 are conceptual diagrams illustrating the difference between the valve train shown in FIG. 4 and the valve train shown in FIG. 10. DESCRIPTION OF SYMBOLS 1... Valve gear, 2.3... Cam, 4... Camshaft, 5... First rocker arm, 6... Second
rocker arm, 5a, 5a... support part, 7...
Rocker shaft, 8.9... Valve (valve stem), 10... Eccentric large diameter section, 11... Eccentric bush, 12... Pin. Applicant Suzuki Motor Co., Ltd. Figure 2 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Scope of Claims] A camshaft in which two types of cams having different cam profiles are formed adjacent to each other, and the cam lift amount of one cam is larger than the cam lift amount of the other cam; A first rocker arm that is disposed on the side of the cam with a smaller cam lift among the cams formed on the camshaft and directly contacts the valve head that opens and closes the combustion chamber, and a cam with a larger cam lift among the cams formed on the camshaft. Centering around the rocker shaft that is arranged on the side and supports at least the rocker arm,
a second rocker arm that engages with an upper surface of the first rocker arm located further away from a position where the first rocker arm directly contacts the valve head; and a second rocker arm that is rotatably supported; In addition to being fitted into each of the support parts of the first and second rocker arms, the part to be fitted into the support part of the second rocker arm has a diameter larger than that of the other parts, and whose axis is different from that of the other parts. a rocker shaft having an eccentric large-diameter portion eccentric from the axis of the second rocker arm; and by rotating the rocker shaft by a predetermined angle, the support portion of the second rocker arm is supported by the eccentric large-diameter portion. The first rocker arm is moved downward relative to the support portion of the first rocker arm, and the cam with a large cam lift amount is released from contact with the second rocker arm, so that the cam with a small cam lift amount and the second rocker arm are moved relative to each other. The second rocker arm is brought into contact with the second rocker arm, the valve is operated by following the cam profile of the cam having a smaller cam lift, and the rocker shaft is rotated by a predetermined angle, so that the second rocker arm is brought into contact with the second rocker arm by the eccentric large diameter portion. The supporting part of the rocker arm is raised to a position equivalent to the supporting part of the first rocker arm, and the cam with the small cam lift amount is released from contact with the first rocker arm, so that the cam with the small cam lift amount is released from the first rocker arm. A valve train for a four-cycle engine, characterized in that a cam and the second rocker arm are brought into contact with each other, and the valve is operated by following the cam profile of the cam having a large cam lift.