JPH0571322A - Valve lift controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To change the quantity of valve lift over to two stages and to see that the shock absorbing action can be gotten at the outset of opening of a valve and at the seating even in middle lift condition. CONSTITUTION:A tappet body 9 is arranged capably of up and down motion coaxially with an intake valve 1, and this is pressed with a cam 10. The tappet body 9 has a selector pin 17 being slid by hydraulic pressure, and a plunger 10, which presses the intake valve 1 at full lift, is supported by the side face under the selector pin 17. Moreover, to get middle lift, a middle supporting face 21 is cut and made at the top of the selector pin 17. Lamp parts are made corresponding to the full lift and the middle lift, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an intake valve for an internal combustion engine,
The present invention relates to a valve lift control device capable of switching the lift amount of an exhaust valve in two stages, and more particularly to a direct-acting type valve lift control device having no rocker arm.

[0002]

2. Description of the Related Art For example, in JP-A-61-118518, a bottomed cylindrical tappet body is disposed coaxially with an intake / exhaust valve, and is disposed slidably in the radial direction within the tappet body. A valve operating device is disclosed in which opening / closing of an intake / exhaust valve can be stopped by advancing / retreating a selector pin. That is, a plunger is slidably arranged at the center of a tappet body that moves up and down by a cam, the lower end of the plunger presses the valve stem end, and the upper end of the plunger is the tip of the selector pin. It is supported by the side of the part. Therefore,
When the selector pin is located near the center of the tappet body so as to cover the upper end of the plunger, the vertical movement of the tappet body is transmitted to the valve stem via the plunger, while the selector pin retracts to the outer circumference of the tappet body. In this state, the support of the plunger is released and the plunger and tappet body can move relative to each other, so that only the tappet body moves up and down following the cam, and the intake and exhaust valves do not open and close.

[0003]

However, in the above-mentioned conventional configuration, only two types of intake / exhaust valves, which are opened / closed or stopped, can be selected, and variable control of the lift amount cannot be realized. Therefore, it has been impossible to improve the output and the fuel consumption by controlling the lift amount.

[0004]

A valve lift control device for an internal combustion engine according to the present invention is provided with a guide hole formed coaxially with an intake / exhaust valve of the internal combustion engine and slidably disposed in the guide hole. And a bottomed cylindrical tappet body in which a valve stem or a plunger connected to the valve stem is inserted in the center, and the end face of the tappet body is slidably in contact with the full lift and the intermediate lift respectively. A cam having a cam profile in which a first ramp portion and a second ramp portion are formed, a return spring for urging the tappet body toward the cam, and a slidable radially arranged inside the tappet body. While supporting the end of the valve stem or the end of the plunger at the position projecting to the inner peripheral side, the tip end has an intermediate position corresponding to an intermediate lift. A selector pin lifting surface is notched formed, is constituted by a hydraulic mechanism for advancing and retracting the selector pin.

[0005]

In the position where the selector pin protrudes toward the inner peripheral side, the end of the valve stem or the end of the plunger connected to the valve stem is supported by the side surface of the selector pin, so that the top and bottom of the tappet body pressed by the cam are moved upward and downward. The motion is immediately transmitted to the valve stem, and the intake / exhaust valve opens and closes.
That is, the intake and exhaust valves are driven by the cam and fully lifted. At this time, the first ramp portion in the cam profile is used.

On the other hand, at the position where the selector pin is retracted to the outer peripheral side, the end of the valve stem or the end of the plunger is supported by the intermediate support surface of the selector pin. In other words, until the valve stem end or the plunger end abuts on the intermediate support surface, only the tappet body moves freely downward, and the intake / exhaust valve opens and closes with the cam lift after the contact with the intermediate support surface. To do. Therefore, an intermediate lift state in which the lift amount is small is obtained. Also,
At this time, the second ramp portion in the cam profile is used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to an intake valve 1 of an internal combustion engine, for example. The intake valve 1 has its face portion 1a seated on the valve seat 2 to open and close the intake port 3, and the valve stem 1b is slidably inserted into the valve guide 5 press-fitted into the cylinder head 4. Further, the valve spring 7 is disposed between the spring seat 6 and the upper surface of the cylinder head 4 in a compressed state, and is constantly urged in the valve closing direction.

Above the intake valve 1, the cylinder head 4 is formed with a guide hole 8 having a cylindrical surface coaxial with the intake valve 1. The guide hole 8 has a slightly larger diameter than the spring seat 6 and the valve spring 7, and a bottomed cylindrical tappet body 9 is slidably fitted therein. A cam 10 is located above the tappet body 9, and the cam 10 is in sliding contact with the end surface of the tappet body 9.

As shown in FIG. 2, the tappet body 9 has a pair of pin fitting holes 11 extending in the radial direction. More specifically, the pair of pin fitting holes 11 are continuous along the diametrical direction of the tappet body 9. The pin fitting holes 11 are formed by machining so that the openings at both ends are closed by press fitting the caps 12. Yes (see Figure 2). Further, spring insertion holes 13 are recessed from the bottom side along the axial direction of the tappet body 9 at four locations that do not interfere with the pin fitting holes 11, and the return springs 14 are arranged in the spring insertion holes 13, respectively. Has been done. The return spring 14 is arranged in a compressed state between the return spring 14 and the spring seat 6, and thereby the tappet body 9 is biased toward the cam 10. The spring force of the entire return spring 14 is set smaller than the spring force of the valve spring 7. A plunger insertion hole 15 is formed in the center of the tappet body 9 so as to intersect with the pin fitting hole 11 from the bottom side along the axial direction of the tappet body 9, and a cylindrical plunger 16 slides therein. Fitting is possible. This plunger 16
The lower end of the valve contacts the end of the valve stem 1b.

Selector pins 17 as shown in detail in FIGS. 3 to 6 are slidably and symmetrically arranged in the pair of pin fitting holes 11. The selector pin 17 has a cylindrical shape with a bottom that is open at the tip side, that is, the center side of the tappet body 9, and has a long hole 18 along the axial direction on the side surface. It projects into the storage portion 17b. A return spring 20 is arranged in a compressed state between the bottom portion 17a of the selector pin 17 and the spring stopper 19, and the spring force of the return spring 20 urges the selector pin 17 toward the outer peripheral side of the tappet body 9. The spring stopper 19 has a base end fixed to the tappet body 9.

The total length of the selector pins 17 is set to a length that does not interfere with the plunger 16 when both selector pins 17 are positioned on the outer peripheral side of the tappet body 9 by the spring force. Then, as shown in FIGS. 4 and 5, an intermediate support surface 21 corresponding to the intermediate lift is cut out at the tip portion thereof. In addition, oil holes 22 are formed at both ends of the pin fitting hole 11 so as to press the bottom portion 17a of the selector pin 17 by hydraulic pressure against the spring force of the return spring 20. This oil hole 22 is
It communicates with a hydraulic passage 24 of the cylinder head 4 via an oil groove 23 on the outer peripheral surface of the tappet body 9.

Further, in the cam 10 for pressing the tappet body 9, the cam profile is formed as shown in FIG. That is, the first ascending ramp portion 31 and the first descending ramp portion 32 are provided in the range of θ ₁ and θ ₈ connected to the base circle, and the rising portion θ ₃ and the falling portion θ ₆ during the intermediate lift are provided.
In addition, the second up-ramp section 33 and the second down-ramp section 34
Is provided. The second up-ramp portion 33 and the second down-ramp portion 34 are adapted to be smoothly connected to the line on the outer peripheral side by t ₁ from the base circle. The t ₁ is the selector as shown in FIG. It is equal to the height from the lower side surface of the pin 17 to the intermediate support surface 21. The diameter (t ₁ + t ₂ ) of the entire selector pin 17 is set to be equal to the maximum lift amount of the cam 10. The height and inclination of the first rising ramp portion 31 are L _1U and α _1U , the height and inclination of the first descending ramp portion 32 are L _1D and α _1D , and the height and inclination of the second rising ramp portion 33 are L _2U and α _2U , second
When the height and inclination of the descending ramp section 34 are L _2D and α _2D , the respective sections have the following relationship.

L _1U > L _2U , L _1D > L _2D L _1D > L _1U , L _2D > L _2U α _1U <α _2U , α _1D <α _2D α _1D <α _1U , α _2D <α _2U In the configuration of the example, the lift amount of the intake valve 1 is changed stepwise by controlling the hydraulic pressure supplied from the oil hole 22 via the hydraulic passage 24 by a hydraulic control valve or the like (not shown). First, in the state where the hydraulic pressure is released, the selector pin 17 is retracted to the outer peripheral side of the tappet body 9 as shown in FIG. 1, and does not interfere with the plunger 16. Therefore, the tappet body 9 and the plunger 16 can move relative to each other, and even if the cam 10 presses the tappet body 9, only the tappet body 9 moves up and down, and the intake valve 1 does not lift. That is, the opening and closing of the intake valve 1 is stopped.

On the other hand, when a large hydraulic pressure is supplied through the oil hole 22, as shown in FIG. 8, the pair of selector pins 17 slide on the central portion of the tappet body 9 and the tip of the plunger 16 moves toward the selector pin 17. It comes to support on the lower side. Therefore, the vertical movement of the tappet body 9 driven by the cam 10 is directly transmitted to the intake valve 1 via the plunger 16, and the intake valve 1 is fully lifted along the cam lift. Further, at this time, when the intake valve 1 starts to open and is seated, a cushioning action is obtained by the first rising ramp portion 31 and the first falling ramp portion 32 in the cam profile.

On the other hand, if the oil pressure supplied through the oil hole 22 is set to a predetermined intermediate value, the selector pin 17 will be slightly moved toward the center of the tappet body 9 as shown in FIG. When the tappet body 9 moves up and down in this state, the plunger 16 comes into contact with the intermediate support surface 21 of the selector pin 17 and is supported by the intermediate support surface 21. That is, only the tappet body 9 freely moves up and down up to the cam lift corresponding to the height t ₁ of the intermediate support surface 21, but the cam lift after that is the plunger 1.
6 is transmitted to the intake valve 1 through t 6, so that t ₂ shown in FIG.
An intermediate lift state equivalent to is obtained. Further, at this time, when the intake valve 1 starts to open and is seated, the second ascending ramp portion 33 and the second descending ramp portion 34 in the cam profile provide a cushioning action.

In the above embodiment, the valve stem 1b of the intake valve 1 is pressed through the plunger 16, but the end of the valve stem 1b is extended and directly abuts on the selector pin 17. It may be configured.

[0018]

As is apparent from the above description, according to the valve lift control device for an internal combustion engine according to the present invention, not only the opening and closing of the intake and exhaust valves are simply stopped, but also the lift amount thereof is controlled stepwise. Therefore, it is possible to improve the output and fuel efficiency by controlling the lift amount according to the driving conditions. In addition, since the ramp portion is formed on the cam profile corresponding to the full lift and the intermediate lift, a cushioning effect is obtained even during the intermediate lift, preventing a strong collision between the cam and the tappet body and a sudden seating of the intake and exhaust valves. To be done.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a valve lift control device according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a plan view of a selector pin according to this embodiment.

FIG. 4 is a front view of a selector pin of the same.

FIG. 5 is a side view of the selector pin.

FIG. 6 is a sectional view showing a state in which a selector pin and a return spring are combined.

FIG. 7 is a cam lift characteristic diagram showing a cam profile in this embodiment.

FIG. 8 is an operation explanatory view in a state where the selector pin is located at the center of the tappet body.

FIG. 9 is an operation explanatory diagram in a state where the selector pin is moving to an intermediate position.

[Explanation of symbols]

 1 ... Intake valve 8 ... Guide hole 9 ... Tappet body 10 ... Cam 14 ... Return spring 16 ... Plunger 17 ... Selector pin 21 ... Intermediate support surface 24 ... Hydraulic passage

Claims (1)

[Claims] 1. A guide hole formed coaxially with an intake / exhaust valve of an internal combustion engine, and slidably disposed in the guide hole,
Further, a bottomed cylindrical tappet body having a valve stem or a plunger connected to the valve stem inserted in the central portion, and a first ramp corresponding to a full lift and an intermediate lift, respectively, in sliding contact with the end surface of the tappet body. A cam having a cam profile in which the first portion and the second ramp portion are formed, a return spring for urging the tappet body toward the cam, and a return spring that is slidably disposed in the tappet body, A selector pin, which supports the end of the valve stem or the end of the plunger at a position projecting to the circumferential side, and has a notch at the tip end, which has an intermediate support surface corresponding to an intermediate lift, and a hydraulic pressure for moving the selector pin forward and backward. And a valve lift control device for an internal combustion engine.