JPH02221618A - Valve system of internal combustion engine - Google Patents

Abstract

PURPOSE:To exclude the use of a big valve spring so as to reduce the overall height of an engine by providing a load device capable of adjusting the effective spring constant by means of hydraulic pressure, independently from a valve spring, as auxiliary spring means for energizing a low-speed rocker arm in valve closing direction. CONSTITUTION:A pair of inlet valves 1a, 1b are switched by first to third rocker arms 5 to 7 which oscillate while in engagement with low-speed cams 3a, 3b and a high-speed cam 4, and the rocker arms 5 to 7 are capable of being switched by a connecting device 11 from a state wherein they can be oscillated integrally with each other to a state wherein they can be displaced relative to each other. In this case, sub-arms 31, 32 are protrusively provided on respective low-speed rocker arms 5, 7 and opposite to a cam shaft 2, and their loose end portions are made to abut to the lower face of the piston 38 of a load device 35 which piston is energized by a coil spring 39. The coil spring 39 has its upper end received and supported by a switching piston 41 to control hydraulic pressure for a hydrolytic room 42 located above the switching piston 41, thus making the spring constant of the coil spring 39 variable.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a valve mechanism that opens and closes an intake valve or an exhaust valve in synchronization with the rotation of an internal combustion engine. The present invention relates to a valve mechanism for an internal combustion engine that can switch operating states.

<Prior Art> Generally, in an internal combustion engine, the intake valve and exhaust valve, which feed a mixture to a combustion chamber and exhaust combustion gas in a predetermined cycle, are always held in the closed direction by a valve spring made of a compression coil spring. Forced. Both valves are forcibly pushed open against the biasing force of the valve spring by a cam connected to and driven by the crankshaft of the engine and a cam provided on the shaft. Therefore, as is well known, if the biasing force of the valve spring is too large, the friction loss will increase especially in the medium and low speed range, and if it is too small, the followability of the cam follower will decrease due to the inertia of the valve train in the high speed range. .

On the other hand, conventionally, for example, Japanese Patent Application Laid-open No. 61-1 by the applicant of the present application
In Publication No. 9911, etc., two low-speed cams and a single high-speed cam with shapes corresponding to low-speed and high-speed operation of the engine are integrated into a camshaft that rotates in synchronization with the rotation of the engine. , three rocker arms that slide in contact with each cam are adjacently supported on a rocker shaft, and each rocker arm is equipped with a connecting means that can be switched between a state in which the rocker arms are displaced relative to each other and a state in which they are integrally connected, allowing a wide operating range. Various valve mechanisms for internal combustion engines have been proposed that can optimize intake and exhaust efficiency. In this type of valve operating mechanism, each rocker arm has a built-in connecting means, so the equivalent weight of the rocker arm per valve is larger than usual. Moreover, when three rocker arms are connected, the equivalent weight increases further.

If the lift load of the valve spring is set large to absorb this increase in the equivalent weight of the rocker arm, the valve spring will inevitably become larger and its set length will become longer, the cylinder head will become taller, and the overall height of the engine will increase. This causes an inconvenience. Actual public school 60-30437
The publication discloses a technique for compressing a valve spring using fluid pressure in order to make the valve-opening force variable, thereby increasing the reaction force of the valve spring, but this is for an exhaust brake. However, it does not change the spring constant, and is not necessarily suitable for compensating the inertial mass of the valve train at high speeds. In view of this, the applicant of the present application has proposed in Japanese Patent Application Laid-Open No. 62-243904 a valve operating mechanism that is elastically supported using an auxiliary spring means.

<Problems to be Solved by the Invention> The main purpose of the present invention is to improve the prior art described above, reduce the load on the valve springs, eliminate the use of large valve springs, and reduce the overall height of the engine. An object of the present invention is to provide a valve operating mechanism for an internal combustion engine that can switch the valve operating state.

<Means for Solving the Problems> According to the present invention, such an object is achieved by providing a plurality of cam followers arranged adjacent to each other by a cam that is always biased in the valve closing direction by a spring means and rotates in synchronization with the crankshaft. an intake valve or an exhaust valve that is driven to open via the cam follower, a connection switching means that selectively switches the cam follower between a state where the cam follower is integrally connected and a state where the cam follower is disconnected and capable of relative displacement; A valve operating mechanism for an internal combustion engine, comprising an auxiliary spring means for biasing the valve in the valve closing direction, wherein an effective spring constant of the auxiliary spring means is adjustable according to the operating state of the engine. This is achieved by providing a valve mechanism for the engine.

<Operation> By doing this, the auxiliary spring means whose biasing force is adjusted according to the operating conditions of the engine such as the speed range compensates for the increase in the equivalent weight of the cam follower, thereby effectively reducing the burden on the valve spring. It can be reduced.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG.
The pair of intake valves la and lb are connected to one of the crankshafts (not shown).
A pair of low speed cams 3a are integrally provided on the camshaft 2 which is driven synchronously at a speed of /2.

3b and a single high-speed cam 4, and these cams 3a, 3b
The opening/closing operation is performed by the first to thirtieth claw arms 5 to 7 as cam followers that engage with the cam follower 14 and swing. Further, this internal combustion engine is equipped with a pair of exhaust valves (not shown), which are driven to open and close in the same manner as the above-mentioned intake valves 1a and 1b.

The first to thirtieth lever arms 5 to 7 are rotatably supported adjacent to each other by a rocker shaft 8 that is fixed in parallel below the camshaft 2 . 1st and 30th lever arms 5.
7 has basically the same shape, its base is pivotally supported by the rocker shaft 8, and its free end extends to three sides of both intake valves 1a and 1b. At the free end of the double-ended hook arm 5.7, there is a tappet screw 9 that abuts the upper end of each intake valve 1a, 1b.
a, 9b are lock nuts 10a, 1. It is screwed into place so that it can move forward and backward without loosening. Also, the first
And on the upper surface of the 30th lever arm 5.7 is a low speed cam 3a.
, 3b are formed, respectively.

Furthermore, the first and thirtieth claw arms 5.7 each have sub-arms 31.7 extending in the opposite direction to the intake valves 1a, 1b.
32. Free end 33.3 of sub-arm 31.32
The lower ends of loading devices 35, which will be described later, are in contact with the upper ends of the four.

The base of the 20th claw arm 6 is pivotally supported by the rocker shaft 8 between the first and 30th claw arms 5.7.

The free end of the 20th lever arm 6 slightly extends from the rocker shaft 8 toward the middle of the intake valves 1a, 1b, and has a cam slipper 6 on its upper surface that slides into contact with the high-speed cam 4.
a is formed, and the lower surface is fixed to the cylinder head side or is in contact with the upper end surface of a lid (not shown). This lifter uses a built-in coil spring as a lost motion spring to urge the 20th lever arm 6 upward so that the cam slipper 6a is always in sliding contact with the high-speed cam 4.

The camshaft 2 is rotatably supported above the engine body, and has low speed cams 3a corresponding to the first and 30th lever arms 5.7.
, 3b and a high-speed cam 4 corresponding to the 20th claw arm 6 are integrally connected.

As best shown in FIG. 2, the low-speed cams 3a, 3b have a relatively small lift and are formed with an oval cross-section cam profile suitable for low-speed operation of the engine. The high-speed cam 4 has a larger lift over a wider angle than the low-speed cam 3a13b, and is formed into a cam profile with an oval cross section suitable for high-speed operation.

The first to thirtieth lever arms 5 to 7 can be switched between a state in which they can swing integrally and a state in which they can be relatively displaced by a connecting device 11 built in their central portions. In addition, retainers 12a and 12b are provided in the two parts of both intake valves 1a and 1b, respectively, and retainers 12a and 12b are provided between the two intake valves 1a and 1b.
Valve springs 13a and 13b, which are interposed so as to surround the stem portions of valves a and 1b, bias both valves 1a and 1b upward in the valve-closing direction, that is, in FIG.

As clearly shown in FIG. 2, a loading device 35 is attached to both intake valves 1a on a cylindrical portion 36 fixed to the cylinder head side.
, a guide hole 37 is bored approximately parallel to the sliding axis of 1b,
A piston 38 is slid into the interior thereof. piston 38
is constantly urged downward by a compression coil spring 39,
In addition, the free end portion 34 of the sub-arm 32 is located at the lowest position where it is locked to the step portion 40 at the lower end of the guide hole 37, and whose lower end is at a rest position where the cam slipper 7a slides on the base circle of the cam 3b.
” is in contact with one end.

A switching piston 41 is sandwiched between the upper end of the coil spring 39 and the upper surface of the guide hole 37. The switching piston 41 is
It slides fluid-tightly into the enlarged diameter portion 37a at the upper part of the guide hole 37, and forms a hydraulic chamber 42 between it and the upper surface of the guide hole 37. Then, the switching piston 4 is operated by the action of hydraulic pressure supplied via the oil passage 43 from a hydraulic pressure supply source (not shown).
0 can be displaced downward to the stepped portion 44 along the inner circumferential surface of the enlarged diameter portion 37a.

As clearly shown in FIGS. 3 and 4, a first guide hole 14 is formed in the tenth claw arm 5 in parallel with the rocker shaft 8 and opens toward the twentieth claw arm 6 side. A second guide hole 17 that communicates with the first guide hole 14 of the tenth claw arm 5 is provided through the twentieth claw arm 6 . The 30th hook arm 7 has a second guide hole 17.
A third guide hole 18 communicating with is bored. A stepped portion 19 is formed in the third guide hole 18, and a small diameter through hole 20 is bored in the bottom wall thereof concentrically with the third guide hole 18.

Inside these first to third guide holes 14.17.18, there is a first piston 2 that can move between a position where the first and twentieth hook arms 5.6 are connected and a position where the connection is released.
1, a second piston 22 that is movable between a position where the second and thirtieth hook arms 6.7 are connected and a position where the connections are released, and a stopper 23 that restricts the movement of both pistons 21.22. ing. A coil spring 24 is mounted on the stopper 23 to bias both pistons 21 and 22 toward the disconnection position.

The first piston 21 has an axial dimension such that its other end does not protrude from the first guide hole 14 at a position where one end abuts a step 16 formed on the bottom side of the first guide hole 14 . The second piston 22 has an axial dimension equal to the entire length of the second guide hole 17 . The stopper 23 includes a guide rod 23a that is inserted through the through hole 20.

Inside the first guide hole 14, there is a bottom surface thereof and a first piston 2.
A hydraulic chamber 25 is defined between the first end surface and the first end surface. Further, a hydraulic oil supply passage 26 is bored in the rocker shaft 8 and communicates with a hydraulic pressure supply device (not shown). and,
The 10th lug
Regardless of the swinging state of the hook arm 5, the hydraulic oil supplied from the hydraulic oil supply passage 26 can always be introduced into the hydraulic chamber 25. The hydraulic oil supply passage 26 is supplied with lubricating oil, which is pressure-fed from, for example, an oil pump connected to and driven by the crankshaft of the engine, and is switched and supplied to the hydraulic oil supply passage 26 by, for example, an electromagnetic switching valve depending on the rotational speed of the engine.

Next, the operation procedure of the above-mentioned embodiment will be explained.

In the medium and low speed range of the engine, the solenoid valve is closed and no hydraulic pressure is supplied from the hydraulic oil supply passage 26 to the hydraulic chamber 25 of the coupling device 11, and each piston 21, 22 is operated by the biasing force of the coil spring 24. j According to each guide hole 14 as shown in FIG.
Matches within 20. Therefore, each of the rocker arms 5 to 7 can be angularly displaced relative to each other, and when the camshaft 2 rotates, the first and 30th rocker arms 5.7 move toward the low speed cams 3a and 3b.
The intake valves 1a and 1b swing in sliding contact with each other to open and close both intake valves 1a and 1b. At this time, the 20th claw arm 6 slides into contact with the high-speed cam 4 and swings, but its operation has no effect on the operations of both intake valves 1a and 1b.

On the other hand, in the loading device 35, the hydraulic pressure does not act on the hydraulic chamber 42, and the switching piston 41 is moved into the guide hole 3 by the biasing force of the coil spring 39.
7 is in contact with the top surface. Therefore, since the initial deflection amount of the coil spring 39 is relatively small, the first and 30th lever arms 5.7 swing by the low-speed cams 3a and 3b, and the sub-arms 31.32 push up the piston 38, causing the coil spring 39 to oscillate. Even if the valve is urged in the valve closing direction by the reaction force, the friction against the camshaft 2 is suppressed to a relatively small range.

When the engine is operated at high speed, the solenoid valve is opened and hydraulic pressure is supplied from the hydraulic oil supply passage 26 to the hydraulic chamber 25 through the communication hole 29 of the rocker shaft 8 and the oil passage 28 . As a result, as shown in FIG. 4, the first piston 2
1 moves toward the 20th lever arm 6 against the biasing force of the coil spring 24, and the second piston 22 is pushed by the first piston 21 and moves toward the 30th lever arm 7. As a result,
The first and second pistons 21.22 move together until the stopper 23 abuts against the step 20, the first piston 21 connects the first and 20th lever arms 5.6, and the second piston 22 connects the 26th are connected, and the second and thirtieth claw arms 6.7 are connected by the second piston 22.

In this connected state of the first to 30th claw arms 5 to 7, the amount of swing of the 20th claw arm 6 that is in sliding contact with the high-speed cam 4 is the largest. oscillate. Therefore, both intake valves 1a and 1b are driven to open and close according to the cam profile of the high-speed cam 4, with their closing timings being earlier and later, and the lift amount being increased.

In the low speed range, the movement speed of the valve and rocker arm is relatively low, and the valve closing force may be relatively small. However, as the engine speed increases, the 1st to 30th
When the lever arms 5 to 7 are connected, the movement speed of the valve and rocker arm increases, and the inertial mass of the valve train as a whole increases. As a result, in the high speed range, both intake valves 1a and 1b are closed, and at the same time the first to third intake valves are closed.
It becomes necessary to increase the acting force for pushing the zero tension arms 5 to 7 upward.

In this embodiment, the oil passage 43 communicates with a hydraulic pressure generation source at a speed higher than a set speed, which is formed by, for example, an electromagnetic switching valve that is opened and closed in response to a speed signal. When hydraulic pressure is introduced into the hydraulic chamber 42, the switching screw 40 is pushed down until it comes into contact with the stepped portion 44, and the coil spring 39 is compressed accordingly, increasing its effective spring constant. , the downward biasing force on the sub-arms 31, 32 increases.

In the above embodiment, the hydraulic pressure was switched according to the preset engine speed and supplied to the hydraulic chamber 42 from the oil passage 43, but the hydraulic pressure that increases according to the engine speed is constantly supplied to the hydraulic chamber 42. Acting switching piston 4
1, the effective spring constant of the coil spring 39 can be gradually increased to increase the downward biasing force against the sub-arms 31 and 32. Further, as a driving source for the switching piston 41, electromagnetic means or the like can be used instead of hydraulic pressure. Further, the switching timing of the loading device 35 and the coupling device 11 is appropriately determined depending on the characteristics of the engine.

Another embodiment of the invention is shown in FIG. In this second embodiment, a loading device 51 that applies a biasing force in the valve closing direction to the sub-arms 3L and 32 of the first and 30th lever arms 5.7 is installed in the guide hole 52 with its upper surface and the coil spring 53.
A hydraulic chamber 55 is defined between the piston 54 and the piston 54, which is urged downward by the piston 54. The hydraulic chamber 55 communicates with an oil passage 57 from a port 56, and the oil passage 57 communicates with an accumulator 58.
and is connected to an oil pump 60 via a check valve 59. Therefore, a predetermined hydraulic pressure that is adjusted to be substantially constant by the accumulator 58 is always introduced into the hydraulic chamber 55. A hydraulic sensor 61 is disposed in the oil passage 57 to constantly detect changes in pressure.

Further, FIG. 5 shows a case where the second embodiment described above is applied to a valve mechanism of a four-cylinder engine, and shows one hydraulic circuit in which the hydraulic chamber 55 of the loading device 51 of each cylinder communicates with the oil passage 57. is configured. When the first and 30th hook arms 5.7 swing due to the rotation of the camshaft 2, the screws of the loading device 51! - The sub arm 3 is pushed up by the action of the hydraulic pressure supplied to the hydraulic chamber 55 in addition to the coil spring 53.
1. Apply a biasing force in the valve closing direction to 32.

When the piston 54 is pushed up, the oil pressure P in the oil passage 57 increases due to its pump action. Since the intake valves 1a and 1b of each cylinder are sequentially opened according to a predetermined cycle, the pistons 54 of each loading device 51 are pushed up sequentially, and the oil pressure P in the oil passage 57 continues as shown in FIG. Changes into a mountain shape.

When the engine is operating at low speed, the 1st and 30th
Since the lever arm 5.7 is driven by the low-speed cam 3a13b and has a relatively small lift amount, the lift amount of the piston 54 is also small and the amount of increase in the oil pressure in the oil passage 57 is small. During high-speed operation of the engine, the first to thirtieth lever arms 5 to 7 are connected and driven by the high-speed cam 4 to increase the lift amount, so the lift amount of the piston 54 also increases and the oil passage 5
The hydraulic pressure rise width in 7 also becomes larger.

Therefore, the high-speed or low-speed operating state is determined from the height difference between the maximum oil pressure P1 during low-speed operation and the maximum oil pressure P2 during high-speed operation detected by the oil pressure sensor 61. In the case of a four-cylinder engine like the one in this example, four peaks are normally formed in succession during one cycle as shown in Figure 6, so the height of the maximum value of the winter peak can be determined for each cylinder. The normal operation of the coupling device 11 can be confirmed. Furthermore, if a crank angle sensor is also used, it is possible to specify the cylinder in which the coupling device is malfunctioning. Furthermore, in the case of an oil pressure sensor, even if the maximum oil pressure changes due to a rise in oil temperature, it is possible to easily compare and judge the level of oil pressure.

In another embodiment, instead of the oil pressure sensor 61, an oil pressure switch is used that operates with an appropriate oil pressure PO set between the maximum oil pressure P1 during low-speed operation and the maximum oil pressure P2 during high-speed operation as a threshold. can do. This oil pressure switch outputs an on signal when the oil pressure P in the oil passage 57 exceeds a threshold value PO, and outputs an off signal when it is smaller than PO. When the metal cylinder coupling device 11 operates normally and switches from low-speed operation to high-speed operation, 4
On signals are generated continuously. Therefore,
By counting these ON signals, it is possible to confirm the normal operation of the coupling device 11 of each cylinder, and if a crank angle sensor is also used in the same way, it is possible to identify the cylinder in which the coupling device is malfunctioning. .

<Effects of the Invention> As described above, according to the present invention, by providing a loading device whose effective spring constant can be adjusted hydraulically as an auxiliary spring means for biasing the low-speed rocker arm in the valve closing direction separately from the valve spring, It is possible to reduce the load on the valve springs due to the increase in rocker arm equivalent load due to the connection means, thereby eliminating the use of large valve springs and reducing the overall height of the engine. By setting it to increase as the speed increases, it is possible to reduce friction in medium and low speed ranges and improve valve train followability in high speed ranges. Furthermore, since the hydraulic pressure that acts as the spring force of the loading device changes as the rocker arm swings, there are advantages such as the fact that it is relatively easy to determine the switching of the valve operating state across the cylinders based on the degree of change. be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cut-away top view of a valve train system to which a loading device according to the present invention is applied. FIG. 2 is a cutaway view of the main part of the loading device in the direction of arrow 2 in FIG. 1. FIG. FIG. 3 is a sectional view taken along the line ■-■ in FIG. 2 during low-speed operation. FIG. 4 is a sectional view similar to FIG. 3 during high-speed operation. FIG. 5 is an explanatory diagram schematically showing a second embodiment of the present invention and a valve operating state detection structure using the second embodiment. FIG. 6 is a diagram showing changes in the oil pressure acting on the loading device in the second embodiment. la, lb...Intake valve 2...Camshaft 3a, 3b.
...Low speed cam 4...High speed cam 5...10th lever arm 6
...20th Tsuka Arm 7...30th Tsuka Arm 5a
, 6a, 7a...Cam slipper 8...Rocker shaft 9a, 9b...Tappet screw 10a, 10b...Lock nut 11...Connection device 12a, 12b...Retainer 13a, 13b...Valve Spring 14...First guide hole 15...Small diameter part 16...Step part
17...Second guide hole 18...Third guide hole 1
One...Step part 20...Through hole 21...First
Screw!・N22...Second piston 23...Stopper 23a...Guide rod 24...Coil spring 25
...Hydraulic chamber 26...Hydraulic oil supply passage 28.
...Oil passage 29...Communication hole 31.32...
sub arm

Claims (3)

[Claims] (1) The cam follower is integrated with an intake valve or an exhaust valve which is always biased in the valve closing direction by a spring means and which is driven to open via a plurality of adjacent cam followers arranged by a cam that rotates in synchronization with the crankshaft. A valve train for an internal combustion engine, comprising a connection switching means for selectively switching between a state in which the cam follower is coupled and driven and a state in which the cam follower is disconnected and capable of relative displacement, and an auxiliary spring means for biasing the cam follower in the valve closing direction. A valve train mechanism for an internal combustion engine, characterized in that an effective spring constant of the auxiliary spring means is adjustable according to the operating state of the engine. (2) The internal combustion engine according to claim 1, wherein the effective spring constant of the auxiliary spring means is adjusted so that its biasing force increases in accordance with the rotational speed of the engine. Valve mechanism. (3) The cam follower is integrated with an intake valve or an exhaust valve that is always biased in the valve closing direction by a spring means and is driven to open via a plurality of cam followers arranged adjacently by a cam that rotates in synchronization with the crankshaft. A valve train for an internal combustion engine, comprising a connection switching means for selectively switching between a state in which the cam follower is coupled and driven and a state in which the cam follower is disconnected and capable of relative displacement, and an auxiliary spring means for biasing the cam follower in the valve closing direction. The auxiliary spring means includes a combination of a coil spring that biases the cam follower in the valve closing direction and a fluid spring that acts in the same direction, and wherein the auxiliary spring means is configured to have a coil spring that biases the cam follower in the valve closing direction, and a fluid spring that acts in the same direction. A valve mechanism for an internal combustion engine, comprising a sensor means for detecting a change in fluid pressure.