JPH06117209A - Valve system for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a valve system of internal combustion engine capable of obtaining the spring constant of a valve spring corresponding to the rotating speed of an engine stably with small force by reducing a friction loss in high speed rotation and also eliminating the necessity of extra energy. CONSTITUTION:A valve spring 15 is located in series through a middle spring seat 17 provided reciprocatedly along a valve stem 5a so that a first spring 15a of larger spring constant is located at the end of a valve stem 5a on the opposite side to a valve head 5b and a second spring 15b of smaller spring constant is located at the valve head 5b side. Also a restriction means 20 to restrict the movement of the middle spring seat 17 to the valve head 5b side when the number of revolutions of an internal combustion engine reaches a specified value is located at the side of the middle spring seat 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for an internal combustion engine, and more particularly to a valve operating system for an internal combustion engine capable of obtaining a spring constant of a valve spring in accordance with the rotational speed of the engine. is there.

[0002]

2. Description of the Related Art Conventionally, as a valve operating system for an internal combustion engine, for example, the one described in Japanese Utility Model Laid-Open No. 57-61103 is generally known. This valve operating device changes the elastic force of a valve spring that constantly urges the valve stem in a direction in which the intake and exhaust valves are closed in accordance with the engine speed. The lower valve spring receiver is moved up and down by the lubricating oil pressure.

Further, Japanese Patent Laid-Open No. 60-209613 discloses a valve operating device in which a lower spring seat for receiving a valve spring is configured to be movable in a valve width direction by a cam so that the elastic force of the valve spring is variable. Is disclosed.

[0004]

However, in all of the above-described valve trains for internal combustion engines, the elastic force of the valve spring is made variable by raising the lower end of the valve spring. There was a problem that a very large amount of force was required to support the bottom from below.

Further, since the set load required to close the valve is increased by raising the lower end of the valve spring having a constant spring constant, the friction loss during high speed rotation is increased and the set load is increased. For that reason, there was a problem that extra energy was required to operate the valve stem downward to open the valve.

[0006] Furthermore, in the former case, the actual exploitation of Shokai 57-61103
The valve operating system for an internal combustion engine described in the publication has a problem that the hydraulic pressure and the valve spring force partially balance each other while the rotational speed changes from a low speed to a high speed, resulting in a very unstable state. The present invention has been devised by focusing on such a conventional problem, and has a small friction loss during high-speed rotation, eliminates the need for extra energy, and reduces the spring constant of the valve spring corresponding to the rotational speed of the engine. An object of the present invention is to provide a valve operating device for an internal combustion engine that can be stably obtained by force.

[0007]

In order to achieve the above object, the present invention opens and closes a valve for intake and exhaust having a valve head on the combustion chamber side by a cam, and the valve is closed by a valve spring. In a valve operating device of an internal combustion engine that is constantly energized, a valve spring is provided with a first spring having a larger spring constant through an intermediate spring seat provided so as to be capable of reciprocating along a stem of the valve. A second spring having a smaller spring constant is arranged in series on the end side of the valve stem opposite to the head so as to be on the valve head side, and the internal combustion engine is rotated to the side of the intermediate spring seat. The gist of the present invention is to provide a regulation means for regulating the movement of the intermediate spring seat toward the valve head when the number of rotations reaches a predetermined number. That.

[0008]

[Operation] According to the present invention, the reciprocating movement of the intermediate spring seat is not restricted by the restricting means when the engine speed is lower than the predetermined speed, and the valve springs have different spring constants. It consists of individual springs. When the engine speed reaches a predetermined speed,
The movement of the intermediate spring seat toward the valve head side is regulated by the regulation means, so that the second spring having a smaller spring constant does not act, and the valve spring has only the first spring having a larger spring constant acting. . Therefore, the spring constant of the valve spring according to the engine speed can be easily obtained, and the initial set load at high speed is the same as at low speed, so the valve stem moves downward at high speed. Friction losses are reduced, as well as lower energy consumption to operate and open the valve.

Further, since the regulating means regulates the movement of the intermediate spring seat toward the valve head to change the spring constant of the valve spring, the set load does not increase, and the intermediate spring seat is regulated with a small operating force. It becomes possible. Furthermore, since the spring constant of the valve spring is changed in two steps, an unstable state where the hydraulic pressure and the valve spring force are partially balanced does not occur while the rotational speed changes from low speed to high speed.

[0010]

EXAMPLES Examples of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a cross-sectional explanatory view of a main part of a valve operating system for an internal combustion engine according to the present invention.
Is provided with a valve 5 for opening and closing a port 3 for intake (or exhaust) with a cam 2. Valve 5
It is inserted into a stepped through hole 7 provided in the cylinder head 1 and is slidably disposed in the small diameter portion 7a of the stepped through hole 7 through a valve guide 9 along its axial direction. The valve stem 5a is composed of a valve stem 5a and a valve head 5b which is provided at one end side (combustion chamber side) of the valve stem 5a to open and close the outlet 3a (or inlet) of the port 3.

A cotter 11 is provided on the other end of the valve stem 5a.
The upper spring seat 13 is fixed through the upper spring seat 13 and the valve 5 is interposed between the upper spring seat 13 and the lower spring seat 14 provided on the bottom portion 7c of the large diameter portion 7b of the stepped through hole 7. A valve spring 15 is attached to constantly urge the other end side (the side opposite to the combustion chamber) to close the valve head 5b.

The valve spring 15 includes a first spring 15a having a larger spring constant and a second spring 15b having a smaller spring constant. The first spring 15a and the second spring 15b are the same as the valve stem 5
The first spring 15a having a larger spring constant, which is arranged in series with the intermediate spring seat 17 slidable along the large-diameter portion 7b of the through hole 7 formed along a.
Is provided on the terminal side of the valve stem 5a opposite to the valve head 5b so that the second spring 15b having a smaller spring constant is on the valve head 5b side.

A regulating means 20 for regulating the movement of the intermediate spring seat 17 to the valve head 5b side is provided beside the intermediate spring seat 17 when the rotational speed of the internal combustion engine reaches a predetermined rotational speed. ing. The regulating means 20 includes a chamber portion 21 formed in the cylinder head 1 located on the side of the large diameter portion 7b of the through hole 7, and the chamber portion 21 is provided.
A piston 22 that is movable in a direction in which it approaches and separates from the through hole 7 is provided inside. The piston 22 is constantly urged by a spring 23 provided on the side of the through hole 7 of the chamber 21 in a direction away from the through hole 7.

On the side of the through hole 7 of the chamber 21, the chamber 21
A hole portion 24 reaching from the through hole 7 to the large diameter portion 7b of the through hole 7 is formed, and the stopper 25 fixed to the through hole 7 side of the piston 22 and capable of restricting the movement of the intermediate spring seat 17 toward the valve head 5b side is provided in the hole. It is arranged so that it can project from and retract into the large diameter portion 7b from the portion 23. The side of the chamber 21 opposite to the through hole 7 side communicates with a hydraulic circuit 26 having a hydraulic pump P.

Therefore, when the engine is running at low speed, the hydraulic circuit 26
When the hydraulic pressure is low, the piston 22 is pressed by the spring 23 to the right in FIG.
The intermediate spring seat 17 is retracted from the large diameter portion 7b of the through hole 7 in accordance with the operation of the cam 2.
You can move freely along b. When the engine speed becomes high and the hydraulic pressure of the hydraulic circuit 26 becomes high, the piston 22 is pressed to the left in FIG. 1 by the hydraulic pressure, and the stopper 25 comes out to the large diameter portion 7b of the through hole 7 and the intermediate spring. The movement of the seat 17 to the valve head 5b side can be restricted. Reference numeral 19 is a valve lifter fixed to the other end of the valve stem 5a and in contact with the cam 2.

Next, the operation of the above-described embodiment of the present invention will be described. When the engine rotates at a low rotational speed and the hydraulic pressure in the hydraulic circuit 26 is low, the piston 22 moves to the spring 23.
Is pressed to the right in FIG. The stopper 25 is retracted from the large diameter portion 7b of the through hole 7, and the intermediate spring seat 17 freely moves along the large diameter portion 7b of the through hole 7 according to the operation of the cam 2. Therefore, at this time, the spring constant of the first spring 15a of the valve spring 15 is Ka and the spring constant of the second spring 15b is Kb.
Then, the spring constant of the valve spring 15 is Ka · K.
It becomes b / (Ka + Kb).

When the engine becomes higher than a predetermined number of revolutions, the hydraulic pressure of the hydraulic circuit 26 becomes higher and the hydraulic pressure becomes higher than the force of the spring 23, the piston 22 is pressed leftward in FIG. 1 by the hydraulic pressure. To move. When the cam 2 is not lifted (the state of FIG. 1), the stopper 2
The tip end of 5 is projected to the large diameter portion 7b of the through hole 7, and the intermediate spring seat 17 is restricted from moving toward the valve head 5b side from the position of the stopper 25. Therefore, the valve 5 is biased toward the cam 2 only by the first spring 15a, and the spring constant of the valve spring 15 becomes the spring constant Ka of the first spring 15a.

When the number of revolutions of the engine becomes lower than a predetermined value again, the hydraulic pressure of the hydraulic circuit 26 also decreases and the piston 2
The spring 2 is pressed by the spring 23 to the right in FIG. The stopper 25 is retracted again from the large diameter portion 7b of the through hole 7, and the intermediate spring seat 17 freely moves along the large diameter portion 7b of the through hole 7 in accordance with the operation of the cam 2 and the valve spring 15 The spring constant is Ka
It becomes Kb / (Ka + Kb).

Therefore, in the present invention, assuming that the lift amount of the cam 2 is x, the load F1 = Ka ·
Kb · x / (Ka + Kb) + Fs, cam 2 at high speed rotation
The load F2 is Ka = x.multidot.Fs, resulting in a straight line graph as shown in FIG. However, Fs is an initial set load of the cam 2 (load required to close the valve 5), F _{max in} the graph is a valve load that can avoid valve jump, surging, etc. even at high speed rotation, and x _max is It is the maximum lift amount of the cam 2. On the other hand, in the conventional case, since the spring constant is constant and only the set load is changed, the load F1 ′ applied to the cam during low speed rotation and the load F2 ′ applied to the cam during high speed rotation are (b) in FIG. ) Is a straight line graph. However, Fs' is the initial set load of the cam during high speed rotation. When the spring constant at low speed rotation, that is, the set load Fs is the same as that of the present invention and the conventional one, as shown in FIG. 3 (c), the work amount of the present invention is reduced by the shaded portion at high speed rotation. Therefore,
Friction loss during high speed rotation is also small.

Further, in order to change the spring constant of the valve spring 15, the stopper 25 may be pushed out to the lower side of the intermediate spring seat 17 via the piston 22, so that a large force for supporting the load of the valve spring 15 from below is applied. The spring constant of the valve spring 15 can be changed with a small operating force without the need. Further, since the spring constant of the valve spring 15 is changed in two steps, an unstable state where the hydraulic pressure and the valve spring force are partially balanced is not generated while the rotational speed changes from low speed to high speed. Therefore, the spring constant of the valve spring 15 can be stably changed.

FIG. 3 shows another embodiment of the present invention, in which two restricting means 20 for restricting the movement of the intermediate spring seat 17 toward the valve head 5b are provided at two lateral sides of the intermediate spring seat 17. It was installed in. By thus providing the regulating means 20 at two places, the intermediate spring seat 17 can be regulated more stably.

FIG. 4 shows another example of the hydraulic circuit 26 used in the regulating means 20 of the present invention, in which the operation of the piston 22 is controlled by a rotation signal from a sensor such as a crank angle sensor or a cam angle sensor. This is what you do. 31
Is a first solenoid valve on the side that supplies oil to the chamber 21, 32 is a second solenoid valve on the side that discharges oil from the chamber 21, 33 and 34 are check valves, and 35 is an oil passage. Reference numeral 36 is a control device for controlling the opening and closing of the solenoid valve by a rotation signal from a sensor such as a crank angle sensor or a cam angle sensor (not shown).

When the engine speed is low, the first electromagnetic valve 31 is closed and the second electromagnetic valve 32 is opened by a signal from the control device 36. Therefore, the piston 22 is pressed rightward in FIG. 4 by the spring 23, the stopper 25 is retracted from the large-diameter portion 7b of the through hole 7, and the intermediate spring seat 17 moves in accordance with the operation of the cam 2. It is free to move along the large diameter portion 7b.

When the number of revolutions of the engine becomes higher than a predetermined number of revolutions, the second electromagnetic valve 32 is closed and the first electromagnetic valve 31 is opened by a signal from the control device 36. Therefore, the piston 22 moves by being pressed to the left in FIG. 4 by the oil pressure of the oil sent from the hydraulic pump P, the tip of the stopper 25 comes out to the large diameter portion 7b of the through hole 7, and the intermediate spring seat 17 Is restricted to the valve head 5b side.

When the engine speed becomes lower than a predetermined set value again, the signal from the controller 36 closes the first solenoid valve 31 and opens the second solenoid valve 32.
The pressure oil is discharged from the chamber portion 21, the piston 22 is pressed by the spring 23 in the right direction in FIG.
Is retracted from the large diameter portion 7b of the through hole 7, and the intermediate spring seat 17 freely moves along the large diameter portion 7b of the through hole 7 in accordance with the operation of the cam 2.

FIG. 5 is a time chart showing the open / closed states of the first solenoid valve 31 and the second solenoid valve 32 described above. N is the engine speed (rpm), and T is time (seconds).
The spring 23 sets the timing at which the piston 22 operates and the stopper 25 regulates the intermediate spring seat 17. By adjusting the elastic force of the spring 23, the operation timing of the piston 22 can be adjusted.

Further, the present invention is not limited to the above-described embodiment, but the piston 22 of the regulating means 20 can be operated by compressed air, and may be operated by an electric device. The present invention can be implemented even in an embodiment.

[0028]

The present invention is configured as described above, and when the engine speed is lower than a predetermined engine speed, the reciprocating movement of the intermediate spring seat is not restricted by the restricting means, and the valve springs have different spring constants. When the number of rotations of the engine reaches a predetermined number of rotations and the engine rotates at a high rotation speed, the intermediate spring seat is restricted from moving toward the valve head side by the restriction means, and the second spring with the smaller spring constant is used. The spring does not act and only the first spring having the larger spring constant acts on the valve spring, so that the spring constant of the valve spring according to the rotational speed of the engine can be easily obtained. Also, at high speed rotation, the initial set load is the same as at low speed rotation, so it is possible to reduce the energy consumption required to open the valve by operating the valve stem downward at high speed rotation, and to reduce friction. It is possible to reduce loss.

Further, since the regulating means regulates the movement of the intermediate spring seat toward the valve head side to change the spring constant of the valve spring, the set load does not increase and the intermediate spring seat is regulated with a small operating force. You can Furthermore, since the spring constant of the valve spring is changed in two steps, an unstable state where the hydraulic pressure and the valve spring force are partially balanced does not occur while the rotational speed changes from low speed to high speed. The spring constant of the valve spring can be changed stably.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of essential parts in a valve train for an internal combustion engine according to the present invention.

FIG. 2A is a graph showing the load of the cam at low rotation and high rotation of the present invention. (B) is a graph showing the load of the cam during low rotation and high rotation of the conventional example. (C) is a graph showing a comparison between the present invention and a conventional example at the time of high rotation.

FIG. 3 is an explanatory cross-sectional view of a main part showing another embodiment of the present invention.

FIG. 4 is a cross-sectional explanatory view of main parts showing another example of the regulating means in the embodiment of FIG.

5 is a time chart of the regulating means of the embodiment of FIG.

[Explanation of symbols]

1 cylinder head 2 cam 5 valve 5a valve stem 5b valve head 15 valve spring 15a first spring 15b second spring 17 intermediate spring seat 20 regulating means

Claims (1)

[Claims] 1. A valve train for an internal combustion engine, comprising a cam for opening and closing a valve for intake and exhaust having a valve head on the combustion chamber side, and the valve being constantly urged in a direction of being closed by a valve spring. The first spring having the larger spring constant is connected to the terminal side of the valve stem opposite to the valve head via the intermediate spring seat provided so as to reciprocate along the stem of the valve. The second spring having the smaller size is arranged in series so as to be on the valve head side, and the intermediate spring seat is provided on the side of the intermediate spring seat when the rotational speed of the internal combustion engine reaches a predetermined rotational speed. A valve operating device for an internal combustion engine, characterized in that a regulating means for regulating the movement of the valve to the valve head side is provided.