JPH0110403Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an intake/exhaust valve drive device for an internal combustion engine that variably controls the opening/closing timing and valve lift amount of intake/exhaust valves according to operating conditions.

Various intake and exhaust valve drive devices have been proposed in the past, which variably control the opening/closing timing of the intake and exhaust valves and the amount of valve lift according to the engine operating conditions so that valve overlap, fresh air filling efficiency, etc. are always optimally achieved. One example is the U.S. Patent No. 1 shown in Figure 1.
No. 3413965 is known.

In this valve drive device, the back surface 4 of a rocker arm 3 whose one end abuts the valve drive cam 1 and whose other end is fitted and supported by the stem end of the intake/exhaust valve 2 is curved. By swinging the left and right sides of the rocker arm 3 while contacting the fulcrum,
The lift of the cam 1 is transmitted to the intake and exhaust valves 2, and in particular, the lever 5 is pivotably supported at one end thereof, and its inclination is regulated by a control cam 6. ing. The control cam 6 is rotationally driven in an appropriate phase according to engine operating conditions by a drive mechanism such as a hydraulic actuator, thereby variably controlling the opening/closing timing and lift amount of the intake/exhaust valve 2. That is, for example, if the lever 5 is pushed down by a large amount by the control cam 6, the free end of the lever 5 and the rocker arm 3 are close to each other in the base circle state of the valve drive cam 1, and therefore the intake and exhaust valves 2 are pushed down by a large amount. As the valve opening timing becomes earlier, the valve lift amount increases, and if the amount of depression by the control cam 6 is small, the free end of the lever 5 and the rocker arm 3 will move even if the valve drive cam 1 is in the same base circle state.
Therefore, the opening timing of the intake and exhaust valves is delayed and the amount of valve lift becomes small.

However, in such a conventional valve drive device, when applied to a multi-cylinder engine with four or more cylinders, one of the intake and exhaust valves 2 is always lifted, so the valve spring 7 is not strong enough. A large torque acts on the shaft 6a of the control cam 6 due to the reaction force, and in order to resist this force and rotate the shaft 6a, a large and powerful actuator is required. Therefore, for example, in an automobile engine, it is difficult to arrange a large actuator within a limited space, and there is also a problem in terms of responsiveness of control of the control cam 6. Moreover, the power loss and wear on the cam surface caused by driving the control cam 6 become large.

In view of these conventional drawbacks, this invention solves the above-mentioned conventional drawbacks by configuring the lever inclination to be individually controlled by a hydraulic actuator whose expansion and contraction are regulated according to the rotational position of the control sleeve. The purpose is to

That is, in this invention, one end of the lever on the cam side is supported by a hydraulic actuator that is telescopically operated, and the hydraulic actuator is fitted in a bracket and rotated according to engine operating conditions. a sleeve, an outer cylindrical part that is slidably disposed within the control sleeve and whose tip is linked to the lever, and an inner cylindrical part that is slidably disposed within the outer cylindrical part and has an oil reservoir therein. A cylindrical portion;
A hydraulic chamber defined between the inner cylinder part and the outer cylinder part, a coil spring compressed and arranged in the hydraulic chamber, and an inner cylinder which fits into the base end of the inner cylinder part and positions its axial center. a cylindrical portion guide, an outer cylindrical portion guide that fits into the tip of the outer cylindrical portion and positions the axial center thereof, a check valve interposed between the hydraulic chamber and the oil reservoir chamber, and a check valve that is interposed between the hydraulic chamber and the oil reservoir chamber; an oil hole that opens in a side wall of the cylindrical portion and constantly communicates with the oil reservoir chamber; and an oil hole that is formed along the circumferential direction of the control sleeve to communicate the oil hole with the oil gear gallery of the bracket, and that is formed in the outer cylindrical portion. The control sleeve is constructed of a hydraulic pressure supply passage in which the position of the passage edge, which is the limit of communication with the oil hole, changes along the circumferential direction of the control sleeve.

Hereinafter, a specific embodiment of this invention will be described in detail based on the drawings.

FIG. 2 is a sectional view showing an embodiment of this invention, in which 11 is a valve drive cam that rotates in synchronization with engine rotation, 12 is an intake and exhaust valve, 13 is a valve spring, and 14 is a bolt attached to a cylinder head 15. The bracket is shown secured at 16. 17 is
One end 17a is connected to the valve drive cam 11, the other end 17b
a rocker arm 20 that abuts the stem ends 12b of the valve stem 12a, has a support shaft 18 rotatably inserted through the substantially center thereof, and has a back surface 19 curved to a predetermined profile;
is a lever provided with a rocker arm support surface 21 that is disposed approximately along the back surface 19 of the rocker arm 17 and that the back surface 19 comes into contact with as a fulcrum, and this lever 20 has bifurcated rocker guide portions on both sides of its approximately central portion. 22, into which the support shaft 18 of the rocker arm 17 is slidably fitted, and between the support shaft 18 and the lever 20, a lever 20 is attached to the bracket 14 side. A coil spring 23 is provided for compression. Further, one end 20a of the lever 20 on the valve side is attached to an adjusting screw 24 for adjusting valve clearance at the distal end edge of the bracket 14.
The one end 2 on the cam side is supported in contact with the
0b is supported by a hydraulic actuator 25 embedded in the bracket 14, and the inclination of the lever 20 is controlled by the expansion and contraction of the hydraulic actuator 25.

The hydraulic actuator 25 expands and contracts in its overall length in conjunction with a control rack 26 that operates according to engine operating conditions, and as shown in detail in FIG. A control sleeve 28 is rotatably fitted into the large diameter portion 27a of the control sleeve 28 and has a pinion portion 28a meshed with the control rack 26; An outer cylinder part 29 having a cylindrical shape with a bottom, an inner cylinder part 31 that is slidably disposed on the outer cylinder part 29 and has an oil reservoir chamber 30 therein, and the outer cylinder part 29 and the inner cylinder part 31. and a coil spring 32 that is compressed and disposed between the outer cylinder part 29 and biases the outer cylinder part 29 in the projecting direction, and a hydraulic chamber 33 is defined within the outer cylinder part 29 by the inner cylinder part 31. At the same time, this hydraulic chamber 33 communicates with the oil reservoir chamber 30 via a check valve 34. A semi-disc-shaped pivot portion 29a is formed at the top of the outer cylindrical portion 29, and the pivot portion 29a is pivotally fitted to one end 20b of the lever 20. Further, the inner cylindrical portion 31 has a plug 3 fitted at the base end thereof.
5 is formed into a tapered surface 35a at a predetermined angle, and by matching with the concave tapered surface 36a of the inner cylinder guide 36 fitted into the bottom surface of the small diameter portion 27b of the cylinder barrel 27, Inner cylinder part 31
The axial center of the proximal end is precisely positioned. Furthermore, the tip of the outer cylinder 29 that protrudes from the control sleeve 28 fits relatively tightly into the outer cylinder guide 37 fixed to the bracket 14, and the axial center of the outer cylinder part 29 is also precisely positioned. In other words, the force acting in the direction perpendicular to the axis from the lever 20 on the outer cylinder portion 29 during valve lift is reduced to both guides 36, 3.
7, thereby maintaining the floating state of the control sleeve 28 to ensure smooth rotation at all times. On the other hand, the oil reservoir chamber 30 has oil holes 38 and 3 opened in the side walls of the inner cylinder part 31 and the outer cylinder part 29, respectively.
9 and a hydraulic pressure supply passage 40 formed in the control sleeve 28 in the circumferential direction to communicate with an oil gear rally 41 of the bracket 14, and the oil holes 38 and 39 are in constant communication with each other. , and the state of communication between the oil hole 39 of the outer cylindrical portion 29 and the oil gear rally 41 is regulated by the hydraulic pressure supply passage 40. That is, as shown in FIG. 4, the hydraulic pressure supply passage 40 is opened in the shape of a slit along the circumferential direction, and
This is formed in a shape that is inclined to one side, for example, depending on the desired characteristics, and the oil gear rally 41
A state of communication is always ensured between the oil hole 39 and the oil hole 39, but on the inner circumferential side, the passage edge 40a on the distal end side does not connect with the oil hole 39 against the protruding movement of the outer cylinder portion 29. This is the limit for communication. Since the axial position of the passage edge 40a changes along the circumferential direction, the protrusion of the outer cylindrical portion 29 depends on the rotational position of the control sleeve 28 regulated by the control rack 26. The possible stroke l changes. Note that the outer cylindrical portion 29 has a fifth
As shown in the figure, rotation is prevented by the fitting between the pivot portion 29a and the fitting portion 20c of the lever 20.

As shown in FIG. 6, the control rack 26 is configured to operate the sleeves 28 of a plurality of cylinders in series, and is connected to an appropriate actuator 51 such as a linear motor or hydraulic cylinder disposed at one end. As well as being driven back and forth,
The amount of movement is determined by a displacement detector 5 such as a potentiometer.
2, and feedback control is performed to the target value. That is, suction negative pressure,
Based on various data 53 such as engine speed and cooling water temperature, a calculation circuit 54 and a control value determination output conversion circuit 55 output a control target signal according to engine operating conditions, and a comparison circuit 56 outputs a control target signal and a control value determination output conversion circuit 55. , displacement detector 5 via transducer 57
The detection signal from 2 is compared, and a signal corresponding to the deviation between the two is output from the deviation detection circuit 58. The actuator 51 is driven by this deviation signal via the output circuit 59, and the forward and backward positions of the control rack 26 are controlled to be in accordance with the engine operating conditions.

Next, the operation of the above configuration will be explained.

First, in FIG. 4, when the control rack 26 is controlled to move to the left in the figure, the relative rotation between the control sleeve 28 and the outer cylindrical portion 29 opens the limit of communication with the oil hole 39, that is, the passage. The axial position of the end edge 40a moves upward in the figure, and the protrusive stroke l of the outer cylindrical portion 29 is reduced as l ₁ shown in FIG. 4. That is, the outer cylindrical portion 29 protrudes under the urging force of the coil spring 32, and accordingly, lubricating oil is supplied into the hydraulic chamber 33 from the oil gear rally 41. Since the supply stops when the passage edge 40a is closed, the outer cylindrical part 29 does not protrude any further, and the total length of the hydraulic actuator 25 is ultimately equal to the gap between the outer cylindrical part 29 and the inner cylindrical part 31, etc. As the oil in the hydraulic chamber 33 leaks, the stroke _l1 becomes shorter. As a result, one end 20a
The lever 20 supported by the adjusting screw 24 swings relatively upward, and the valve drive cam 11
At the base circle of ROTSUKA arm 17
The back side 19 of the lever 20 and the locking arm support surface 2 of the lever 20
It will be in a state separated from 1. Therefore, when the valve drive cam 11 starts to lift from this state, the valve opening timing is delayed by a certain period from the rise of the valve drive cam 11, and the valve closing timing is similarly delayed by the valve drive cam 11, as shown in FIG. 7a. 11, and the maximum lift amount obtained at the peak lift of the valve drive cam 11 also becomes smaller.

Here, as the rocker arm 17 lifts, a rotational force acts on the lever 20 in the clockwise direction in the drawing, but in the hydraulic actuator 25, the hydraulic pressure in the hydraulic chamber 33 is maintained by the action of the check valve 34. , the overall length of the hydraulic actuator 25 hardly changes, and the inclination of the lever 20 remains unchanged. More specifically, during engine operation, the hydraulic actuator 25 leaks a small amount of oil in the hydraulic chamber 33 from the gap with the control sleeve 28 every time the valve drive cam 11 lifts. At the end of the process, the necessary amount of oil is replenished from the oil gear gallery 41 to the hydraulic chamber 33 via the oil reservoir chamber 30, which is repeated, and as a result, macroscopically, the upper edge of the oil hole 39 is always connected to the hydraulic pressure supply passage. The outer cylindrical portion 2 is in a state where the amount of oil leaked and the amount of oil to be refilled are balanced.
The amount of protrusion of the control sleeve 9 is determined, and as a result, the total length can always be accurately obtained in accordance with the rotational position of the control sleeve 28 along the shape of the passage edge 40a.

Next, when the control rack 26 moves to the right in FIG. 4 depending on the engine operating conditions, the hydraulic actuator 25 has a stroke at which the outer cylinder portion 29 can protrude, which is determined by the positional relationship between the oil pressure supply passage 40 and the oil hole 39. Since l expands as l ₂ , during the period when the reaction force of the valve spring 13 is not acting on the lever 20, that is, during the period when the rocker arm 17 is in contact with the base circle of the valve drive cam 11, its total length is equal to the above-mentioned stroke l ₂ Stretch accordingly. Therefore, the lever 20 swings counterclockwise, and the back surface 19 of the rocker arm 17 and the rocker arm support surface 21 of the lever 20 become close to each other. Therefore, when the valve driving cam 11 starts to lift from this state, the intake and exhaust valves 12 move as shown in FIG.
As shown in FIG. 2, the valve drive cam 11 is opened and closed at substantially the same timing as the rise and fall of the valve drive cam 11, and its maximum lift amount is also large. Further, as described above, the inclination of the lever 20 is maintained by the action of the check valve 34 during this lift.

Furthermore, when the control rack 26 is moved again to the left in the figure from the state in which the hydraulic actuator 25 is extended as described above, the length is gradually shortened due to oil leakage with each cam lift, as described above.
By setting the leakage amount appropriately, even if there is a sudden change, it can actually be adequately followed up with several cam lifts.

According to the configuration in which the hydraulic actuator 25 is used for each lever 20 in this way, the inclination of the lever 20 can be quickly controlled during the period when the reaction force of the valve spring 13 does not act. The driving force required for the actuator 51 is extremely small.
Unlike the conventional system, there is no need to provide a large and powerful hydraulic system, and power loss can be significantly reduced, and the lever 20 has good responsiveness to changes in operating conditions. Further, there is no risk of premature wear on the lever 20 as in the conventional case. Moreover, the amount of protrusion of the hydraulic actuator 25 can be controlled with high precision by the rotational position of the control sleeve 28 that is linked to the control rack 26, and is not affected by changes in oil viscosity, etc., and even in multi-cylinder engines, the hydraulic actuator 25 can be There will be no variation from time to time.

As mentioned above, in a multi-cylinder engine with four or more cylinders, the intake and exhaust valves 12 of one of the cylinders are always lifted, and when the control rack 26 is controlled, the hydraulic actuator 25 during the lift period is activated by the valve spring 13. Although the lever 20 is subjected to a force in the longitudinal direction due to the reaction force of It can be done.

Although one embodiment of this invention has been described above, this invention is of course not limited to these embodiments. For example, as means for driving the control sleeve of the hydraulic actuator, in addition to the above-described engagement mechanism between the pinion portion and the control rack, a link mechanism, a rope or belt wrapping mechanism, or the like may be used. Furthermore, instead of simply increasing or decreasing the total length of the hydraulic actuator in response to rotation of the control sleeve in one direction, it is also possible to configure the hydraulic actuator to increase or decrease in accordance with a predetermined characteristic.

As is clear from the above explanation, according to this invention, the inclination position of the lever can be controlled for each valve by using the rest period when the intake and exhaust valves are not lifted, so the control driving force is small. This eliminates the need to use a large actuator, eliminates problems of power loss and wear of levers, etc., and improves transient response of control. In addition, since the extension and retraction position of the hydraulic actuator is forcibly regulated by oil supply regulation according to the rotational position of the control sleeve, control errors do not occur due to changes in oil viscosity, etc. This also has the effect of preventing variations among cylinders and enabling highly accurate control.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional intake/exhaust valve drive device, FIG. 2 is a sectional view of an intake/exhaust valve drive device according to this invention, and FIG. 3 is a sectional view of its hydraulic actuator.
Fig. 4 is a side view of the main parts of the hydraulic actuator, Fig. 5 is a perspective view of the main parts of the hydraulic actuator, Fig. 6 is a block diagram showing the control circuit of the control rack, and Fig. 7 is the valve lift characteristic of this invention. It is a lift characteristic diagram showing an example. 11... Valve drive cam, 12... Intake and exhaust valve,
14... Bracket, 17... Locker arm, 2
0... Lever, 21... Rotsuka arm support surface, 2
6... Control rack, 28... Control sleeve, 29... Outer cylinder section, 30... Oil sump chamber, 31...
Inner cylinder part, 32...Coil spring, 33...Hydraulic chamber, 36...Inner cylinder guide, 37...Outer cylinder guide, 38, 39...Oil hole, 40...Hydraulic pressure supply passage, 41... Oil gear.

Claims (1)

[Scope of utility model registration request] A valve drive cam that rotates in synchronization with engine rotation; a rocker arm that has one end in contact with the valve drive cam and the other end that is linked to the valve stem; A lever having a rocker arm support surface that comes into supporting contact with the lever, a bracket that supports one end of the lever on the valve side, and a hydraulic actuator that supports one end of the lever on the cam side and controls the inclination of the lever by expanding and contracting the lever. and the hydraulic actuator is fitted in the bracket,
and a control sleeve that is rotated according to engine operating conditions; an outer cylindrical part that is slidably disposed within the control sleeve and whose tip is linked to the lever; and a control sleeve that is slidably disposed within the outer cylindrical part. an inner cylindrical portion having an oil reservoir chamber therein; a hydraulic chamber partitioned between the inner cylindrical portion and the outer cylindrical portion; a coil spring compressed within the hydraulic chamber; and the inner cylindrical portion. an inner cylinder guide that fits with the base end of the outer cylinder to position its axial center, an outer cylinder guide that fits with the tip of the outer cylinder and positions its axis, and the hydraulic chamber and oil reservoir. A check valve interposed between the oil chamber and the oil hole, which is open in the side wall of the outer cylinder part and is constantly in communication with the oil reservoir chamber, and the control unit so as to communicate the oil hole with the oil gear gallery of the bracket. A hydraulic pressure supply passage formed in the sleeve along the circumferential direction, and in which the position of the passage edge that is the limit of communication with the oil hole with respect to the protrusion of the outer cylinder portion changes along the circumferential direction of the control sleeve; An intake and exhaust valve drive device for an internal combustion engine.