JPH059449Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an intake/exhaust valve lift control device for an internal combustion engine that variably controls the lift characteristics of the intake/exhaust valves according to engine operating conditions.

(Prior Art) As a conventional intake/exhaust valve lift control device, for example, one described in Japanese Patent Application Laid-open No. 185916/1983 is known.

This involves connecting a pair of mutually rotatable sleeves, one to the crankshaft side and the other to the camshaft side, and the pair of sleeves have slits that intersect with each other. A bearing is provided in the slit, and the bearing is carried by a slider that moves linearly in the direction of the camshaft, and a rotary drive motor is connected to the slider via a rotational motion-linear motion conversion means. It has a means (slit sensor) for generating a pulse signal according to the rotation speed of the output shaft of the rotary drive motor, and controls the rotary drive motor to switch from one timing to another based on the pulse signal from this means. Controlled by circuit.

(Problem to be solved by this invention) However, such a conventional intake/exhaust valve lift control device has a slit sensor that generates a pulse signal according to the rotation speed of the output shaft of the rotary drive motor. However, in order to switch the valve timing based on the input of this pulse signal, the drive motor was controlled in forward and reverse directions by the control circuit, so it was essential to have a slit sensor and a drive motor, and also to move the drive motor to the target position. Since the control circuit for controlling forward and reverse rotation becomes complicated, there is a problem in that the cost increases. Furthermore, since the drive motor has brushes, there is a problem in that the durability is limited due to wear of the brushes.

(Means for solving the problem) This invention was made to solve the above problem, and as shown in Figure 1,
An intake/exhaust valve lift variable mechanism (a) that varies the lift characteristics of the intake/exhaust valves in accordance with stepwise changes of a lift control cam having a plurality of cam surfaces, and a plurality of intake/exhaust valve lift variable mechanisms a to which negative pressure or atmospheric pressure is introduced. A multi-stage cam control shaft having a plurality of diaphragms defining a pressure chamber, and rotating a cam control shaft rotatably supporting the lift control cam to a target cam surface in accordance with changes in pressure within the pressure chamber. diaphragm actuator b;
a switching means c for operating the multi-stage diaphragm actuator in stages by switching between introducing negative pressure or atmospheric pressure into the pressure chamber; an operating state detecting means d for detecting the operating state of the engine; control means e for switching and controlling the switching means so that the lift control cam becomes the target cam surface;
It is equipped with the following.

(Function) In this device having such a configuration,
The multi-stage diaphragm actuator is operated by switching and controlling the switching means via the control means in accordance with the operating conditions of the engine, and the lift control cam is selected and controlled to have a predetermined cam surface. Therefore, predetermined valve timing can be obtained depending on the operating conditions. Furthermore, there is no need to provide a slit sensor or a rotary drive motor, and the configuration of the control circuit is simple, so durability can be improved and costs can be significantly reduced.

(Example) Hereinafter, an example of this invention will be described based on the drawings. FIGS. 2 to 9 are diagrams showing an embodiment of this invention. First, to explain the configuration, the variable intake/exhaust valve lift mechanism consists of an intake/exhaust valve drive cam (hereinafter referred to as a drive cam) 11 that rotates in synchronization with engine rotation, and an intake/exhaust valve drive cam 11 that rotates in synchronization with engine rotation. A rocker arm 13 is provided with both ends of the valve (hereinafter referred to as an intake valve) in contact with the stem end of the valve (hereinafter referred to as an intake valve).
3 is brought into fulcrum contact with the curved rear surface 13a of the rocker arm 13, and the shaft 13b protruding from both side walls of the rocker arm 13 is inserted into the groove 15 through the holding member 14.
A lever 15 is provided for holding in a. Between the spring seat 15b formed on the lever 15 and the holding member 14, there is a spring 16 with a small spring constant that biases the rocker arm 13 downward in FIG.
is inserted.

Further, the spherical lower end surface of the hydraulic pivot 19, which is fitted and held in a bracket 18 inserted into the cylinder head 17, is connected to a concave portion 15c formed on the top wall of the other end of the lever 15 on the stem end side of the intake valve 12. The lift control cam 20, which is fitted into the bracket 18 to freely swing and support the lever 15 around the fitting part, and which is rotatably attached to the bracket 18 as described later, is attached to the drive cam 11 side of the lever 15. The pivoting position of the lever 15 is regulated by contacting the end top wall of the lever 15.

The lower end surface of the hydraulic pivot 19 is connected to the lever 1.
The outer cylinder 19a is fitted into the concave portion 15c of No. 5 and whose peripheral surface is slidably inserted into the mounting hole 18a formed in the bracket 18, and the inner cylinder 19b is fitted into the outer cylinder 19a. In addition, a check valve 19d is provided in a hydraulic chamber 19c formed between the two. Then, the inner cylinder 19b is connected from the hydraulic pressure supply passage 18b formed inside the bracket 18.
Hydraulic pressure is supplied to the hydraulic chamber 19c internally and via the check valve 19d to maintain the valve clearance at zero.

The lift control cam 20 has the intake valve 1 on its outer peripheral surface.
Almost flat 5 to change the lift amount of 2 step by step
An insertion hole 2 having two cam surfaces 20a to 20e, and a cam control shaft 23 (to be described later) inserted through the center thereof.
It has 0g. Further, the outer peripheral surface of the cylindrical portion 20h formed to protrude from both sides of the lift control cam 20 is connected to a lower circular groove 18c formed in the bracket 18 and a bolt on the bracket 18, as shown in FIGS. 3 and 4. It is rotatably held between the upper arcuate grooves 22a formed in the pair of caps 22 fastened together at 21.

Then, one cam control shaft 23 is passed through a hole 20g formed through the center of the lift control cams 20 provided in several cylinders, and the cam control shaft 23 is fitted into both sides of each lift control cam 20. One end of the inserted coil spring 24 is locked to a set screw 23a screwed into the outer wall of the cam control shaft 23, and the other end of the coil spring 24 is connected to the lift control cam 2.
It is fitted into a hole formed in the side wall of the cylindrical portion 20h of No. 0 and locked.

One end of the cam control shaft 23 is connected to a drive shaft 26a of the drum 26 via a joint 25.
The drum 26 is connected to a multistage diaphragm actuator 27 via a wire 26b, and the actuator 27 receives a drive signal from a control circuit 28.
The cam control shaft 23 is driven by the SK to rotate the cam control shaft 23. A return spring 29 urges the drum 26 to rotate in a direction opposite to the direction in which the wire 26b is pulled. In addition, in FIG. 2, 10 is a valve spring.

Next, the multi-stage diaphragm actuator 27 will be explained based on FIG.

In the same figure, the wire 26b is connected to the coupling 3
0 to a diaphragm 32a housed in the casing 31. The diaphragm 32a is fixed to its inner peripheral portion so that a movable member 33a abuts thereon, and its peripheral portion is caulked and fixed to a fixed member 34a. A negative pressure chamber (pressure chamber) 35a is defined by the fixed member 34a and the diaphragm 32a, and negative pressure is introduced into the negative pressure chamber 35a through a negative pressure passage 36a formed in the fixed member 34a. . Then, when negative pressure is introduced into the negative pressure chamber 35a, the diaphragm 32a is pressed rightward in the figure by the atmospheric pressure, and the movable member 33a moves until it comes into contact with the fixed member 34a. is pulled against the urging force of the return spring 29. Along with this, the drum 26, the drive shaft 26a and the joint 2
5, the lift control cam 20 connects to the lift control shaft 2.
It rotates with 3. Conversely, when the negative pressure chamber 35a is released to atmospheric pressure, the lift control cam 20 returns to its original position due to the biasing force of the return spring 29. Note that a notch 37 is formed at the introduction end of the negative pressure passage 36a to the negative pressure chamber 35a, and when the movable member 33a abuts the fixed member 34a, a gap is formed and the pressure in the negative pressure chamber 35a is reduced. We are working to ensure a smooth implementation. Further, the fixing member 3
Fixed member 34b and movable member 33b adjacent to 4a
A negative pressure chamber 35b is defined between the fixing member 34b and the diaphragm 32b that is in contact with the fixing member 34b.
The negative pressure chamber 35 is
Negative pressure is introduced into b. Furthermore, although not shown, on the right side of the diaphragm 32b in FIG.
Movable members 33a, 33b, fixed members 34a, 34
b, negative pressure chambers 35a, 35b, and negative pressure passage 36
Each pair of diaphragms 32c, 32d and movable members 33c, 33 have the same configuration as a, 36b.
d, fixing members 34c, 34d, negative pressure chambers 35c, 3
5d, and negative pressure passages 36c, 36d are provided in the casing 31, the former diaphragm 32b being coupled to the latter diaphragm 32c,
The latter diaphragm 32d is connected to the right end of the casing 31. For this reason, as mentioned above,
When negative pressure is introduced into the negative pressure chamber 35b, the diaphragm 32a, fixing members 34a, 34
b is pressed rightward in the figure, the fixed member 34b moves until it comes into contact with the movable member 33b, and the wire 26
By further pulling b, in Fig. 3,
The amount of rotation of the lift control cam 20 is increased. Next, when negative pressure is introduced into the negative pressure chamber 35c (not shown), the diaphragm 32c moves to the right, and since the diaphragm 32b is coupled to the diaphragm 32c, the wire 26b is further pulled, causing the lift control cam 20 to rotate. The amount of movement increases, and the negative pressure chamber 3
When negative pressure is introduced to 5d, diaphragm 32d
are coupled to the casing 31, so the diaphragm 32c and the fixing members 34c and 34d are connected to the diaphragm 32a and 32b and the fixing members 34a and 34b.
At the same time, the lift control cam 20 moves to the right, the wire 26b is pulled, and the amount of rotation of the lift control cam 20 becomes maximum. That is, the multi-stage diaphragm actuator 27
By introducing negative pressure or atmospheric pressure into the negative pressure chambers 35a to 35d (pressure chambers), the negative pressure chamber 35
The lift control cam 20 is rotated according to the change in the pressure within a to 35d, and the cam surface 2 of the lift control cam 20 is rotated.
The target cam surface can be selected from 0a to 20g. On the other hand, negative pressure passages 36a to 36 communicating with each negative pressure chamber 35a to 35d
d (only 36a and 36b are shown) are connected to four 3-port switching valves 38a to 38d (switching means), respectively. 3 port switching valves 38a to 38d
is the negative pressure passage 36a due to energization from the control circuit 28.
Negative pressure is introduced into the negative pressure chambers 35a to 35d through the negative pressure chambers 35a to 36d, respectively, and the atmosphere is introduced to each of the negative pressure chambers 35a to 35d when electricity is not supplied. Reference numeral 39 is an accumulator that stores negative pressure, and when the negative pressure is set by the negative pressure switch 40, the negative pressure pump 41 is operated, and when the set negative pressure is reached, the negative pressure pump 41 is stopped. A predetermined negative pressure is stored in the accumulator 39. This negative pressure causes the 3-port switching valves 38a to 38
d into the negative pressure chambers 35a to 35d, and the multistage diaphragm actuator 27 is operated in stages as described above. Note that it is possible to use not only the negative pressure generated by the negative pressure pump 41 but also the negative pressure in the intake pipe of the engine.

Next, the configuration of the control circuit 28 will be explained based on FIG. The control circuit 28 has a function as a control means, and mainly controls the central processing unit CPU50,
It is composed of a read-only memory ROM 51, a random access memory RAM 52, and an I/O port (input/output signal processing device) 53.
The CPU 50 is regularly operated by a clock 54, takes in necessary external data from the I/O port 53 according to the program written in the ROM 51, and sends and receives data to and from the RAM 52 via a bus line 55. performs calculation processing while passing through the
Output to O port 53. The RAM 52 temporarily stores external data.

Here, the engine rotational speed NE is detected by a rotational speed sensor 56 consisting of, for example, a crank angle sensor, and is used as a rotational speed signal and the opening degree of the throttle valve.
CV is detected by the throttle valve opening sensor 57 and A/
After being converted into a digital signal by the D converter 58, each signal is output to the I/O port 53 as a throttle valve opening signal. The rotation speed sensor 56 and the throttle valve opening sensor 57 collectively constitute engine operating state detection means, and the control circuit 28 calculates a control value based on each signal from the operating state detection means. Drive signal SK is applied to each 3-port switching valve 38 so that cam surfaces 20a to 20e become predetermined cam surfaces.
Output to a to 38d.

Next, the action will be explained.

FIG. 7 is a flowchart showing a control program for switching and controlling the 3-port switching valves 38a to 38d written in the ROM ₅₁ .
~ _P24 shows each step of the flowchart. This program is repeatedly executed, for example, once every rotation of the engine.

Here, as shown in Fig. 8, the operating conditions indicate operating ranges (A to E) determined from the relationship between engine speed NE and throttle valve opening CV, where A is the idling range and B is the low speed range. A low load range, C a low speed high load range or a start/acceleration state range, D a normal driving range, and E a high speed driving range, respectively.
Then, predetermined cam surfaces 20a to 20e of the lift control cam 20 are selected depending on the operating conditions A to E, respectively. In addition, A', B', C' and
D' indicates an intermediate range due to hysteresis, and for example, even if it changes to E after it changes to D', the cam surface maintains the cam surface 20e corresponding to E. In Fig. 7, first, it is determined whether the operating condition is E at _P1 , and if it is E,
Proceed to _P2 . At _P2 , flag COND is set to E. Here, the flags COND (A to E) are determined corresponding to the operating conditions A to E, respectively. Therefore, if the operating conditions are E, D, C, B or A at P ₁ , P ₃ , P ₅ , P ₇ , P ₉ , then P ₂ , P ₄ , P ₆ , P ₈ , P ₁₀ In the flag
COND is set to E, D, C, B or A, respectively. When the flag COND is set to E, D, C or B, 38a to 3 of the 3 port switching valves 38a to 38d are selected at _P11 to _P14 .
8d, 38a to 38c, 38a to 38b, or 38a are excited and activated, and the flag is set.
When COND is set to A, all 3-port switching valves 38a to 38d are de-energized and inoperable at _P15 . Also, in _P16 to _P19 , it is determined whether the flag COND is E, D, C or B, respectively,
If it is E, D, C, or B, proceed to P ₂₀ to P ₂₃ , respectively; if it is not E, D, C, or B, proceed to P ₃ ,
Proceed to P ₅ , P ₇ , and P ₉ respectively. Here, P ₂₀ ~ _{P 23}
, when D′, C′, B′ or A′,
Proceed to P ₁₁ to P ₁₄ respectively and select D′, C′, B′, or
If not A′, proceed to P ₃ , P ₅ , P ₇ or P ₂₄ , respectively. At _P24 , the flag COND is cleared, and at _P15 , all the 3-port switching valves 38a to 38e are deactivated.

Here, for example, to explain in detail the case where the engine operating condition is C, it is determined that the operating condition is C at _P5 , the flag COND is set to C at _P6 , and the 3-port switching valve is set at _P13. 38a and 38b are excited. Therefore, since negative pressure is introduced into each negative pressure chamber 35a, 35b via each negative pressure passage 36a, 36b, the actuator 27 pulls the wire 26b by two steps. As a result, the drum 26 rotates, and the lift control cam 2 causes the cam control shaft 23 to come into contact with the lever 15 at a predetermined cam surface 20c.
Rotate 0. Therefore, a lift characteristic exhibiting a medium lift amount as shown by curve c in FIG. 9 is obtained.

When the operating conditions of the engine change to low speed and shift to B' shown in Fig. 8, proceed from P ₁₈ to P ₂₂ ,
At P ₂₂ , the operating condition is determined to be B', and at P ₁₃ , it is determined that the operating condition is 3.
The port switching valves 38a and 38b remain energized, the lift control cam 20 does not rotate, and the predetermined cam surface c is maintained.

Next, the engine operating conditions are B as shown in FIG.
In this case, the flag COND is set to B at P ₈ , only the 3-port switching valve 38a is energized at P ₁₄ , and the 3-port switching valve 38b directs the atmosphere to the negative pressure chamber 3.
5b. Therefore, the return control cam 20 rotates clockwise in FIG. 2 due to the action of the return spring 29, and the return control cam 20 comes into contact with the lever 15 with the cam surface 20a. As a result, as shown by curve b in FIG. 9, the lift amount is small, and the valve opening timing is delayed and the valve closing timing is advanced.

Further, when the operating condition changes to A, D, or E, lift characteristics as shown by curves a, d, and e in FIG. 9 are exhibited. In this way, the lift control cam 20 is rotated according to the operating conditions to control the cam surfaces 20a~
By bringing each of the valves 20e into contact with the lever 15, the lift characteristics of the intake valve 11 can be changed stepwise. Furthermore, in this embodiment, there is no need to provide a slit sensor or a rotary drive motor, and the configuration of the control circuit 28 is simple, so the overall configuration of the device can be simplified and its durability can be improved. This also makes it possible to reduce costs. In this embodiment, a case has been described in which the actuator 27 is operated by introducing negative pressure, but the same effect can be obtained even if positive pressure is introduced.

(Effects) As explained above, according to this invention,
By switching and controlling the introduction of negative pressure or atmospheric pressure into the pressure chamber of the multi-stage diaphragm actuator according to engine operating conditions, the lift control cam can be rotated and valve timing can be variably controlled. Optimal filling efficiency can be obtained depending on the operating conditions. In addition, there is no need to provide a slit sensor or a rotary drive motor, and the configuration of the control circuit is simple.
The configuration of the entire device can be simplified, durability can be improved, and costs can be significantly reduced.

[Brief description of the drawings]

Figure 1 is an overall configuration diagram showing the intake/exhaust valve lift control device for an internal combustion engine according to this invention, and Figures 2 to 9
The figure shows an embodiment of this invention; Fig. 2 is a vertical sectional view of the variable lift mechanism, Fig. 3 is a plan view of the main part thereof, and Fig. 4 shows the mounting part of the lift control cam. An exploded perspective view, FIG. 5 is a partial sectional view showing the multi-stage diaphragm actuator, FIG. 6 is a diagram showing the configuration of its control circuit, FIG. 7 is a flowchart showing the control program, and FIG. 8 is a diagram showing the engine rotation speed. FIG. 9 is an explanatory diagram illustrating each operating range from the relationship between the throttle valve opening degree and the throttle valve opening degree, and FIG. 9 is a graph showing the valve lift characteristics. 12... Suction/exhaust valve, 20... Lift control cam, 20a-20e... Cam surface, 23... Cam control shaft, 27... Multi-stage diaphragm actuator, 28... Control circuit (control means), 32a- 3
2d...Diaphragm, 35a-35d...Negative pressure chamber (pressure chamber), 38a-38d...3 port switching valve (switching means), 56, 57... Operating state detection means.

Claims (1)

[Scope of utility model registration request] A variable intake/exhaust valve lift mechanism that changes the lift characteristics of the intake/exhaust valves in response to stepwise changes in a lift control cam that has multiple cam surfaces, and multiple pressure points that introduce negative pressure or atmospheric pressure. A multi-stage diaphragm that has a plurality of diaphragms defining a chamber, and rotates a cam control shaft that rotatably supports the lift control cam so that it becomes a target cam surface in response to changes in pressure within the pressure chamber. a switching means for operating the multi-stage diaphragm actuator in stages by switching between introducing negative pressure or atmospheric pressure into the pressure chamber, an operating state detecting means for detecting an operating state of the engine, An intake/exhaust valve lift control device for an internal combustion engine, comprising: control means for switching and controlling the switching means so that the lift control cam becomes a target cam surface.