JPH0116979B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a variable compression ratio internal combustion engine that changes the compression ratio with good responsiveness in accordance with operating conditions such as engine load. It is.

[Conventional technology]

In an internal combustion engine, in order to increase its output and reduce fuel consumption, it is sufficient to increase the compression ratio, but increasing the compression ratio causes knocking in the high load range and low rotation range. For this reason, in conventional internal combustion engines with a constant compression ratio, the compression ratio is
Since the value must be set to a value that does not cause knocking in the low rotation range, it is not possible to produce sufficient output and sufficient fuel efficiency in the low load and high rotation ranges.

Therefore, Japanese Patent Application Laid-open No. 54-20220 as a prior art discloses that a sub-piston for increasing or decreasing the volume of the combustion chamber is slidably inserted into a sub-cylinder that opens into the combustion chamber, and the sub-piston is It is proposed that the compression ratio be changed by moving the sub-piston back and forth by supplying and discharging hydraulic oil to and from a hydraulic chamber formed on the back surface of the sub-piston.

In this prior art variable compression ratio internal combustion engine, a hollow stem is integrally connected from the back of the auxiliary piston, and the hollow stem is provided with hydraulic oil in the hydraulic chamber to a portion inside the hydraulic chamber. A spill port is bored into the hollow stem, and a control rod having an oil passage communicating with the atmosphere is slidably inserted into the hollow stem. This is because the secondary piston is configured to move back and forth through an actuator in accordance with the negative fluid in the internal combustion engine, thereby displacing the opening/closing position of the spill port in the axial direction of the stem. Although it has the advantage of being able to automatically change and control the compression ratio according to the load, it also has the following problems.

[Problem that the invention seeks to solve]

That is, in the prior art, the opening/closing position of a spill port in a hollow stem is displaced in the axial direction of the stem by a control rod slidably inserted into the hollow stem, and the control rod is moved back and forth. In order to move the control rods back and forth according to the load of the internal combustion engine, the hydraulic pressure in the hydraulic chamber acts to prevent the control rods from moving back and forth, and a large force is required to move the control rods back and forth. Therefore, the actuator must be made larger.

Moreover, the spill port, which is opened and closed by the control rod, is provided inside the hydraulic chamber. In other words, the sliding part between the hollow stem and the control rod is located at the inner part of the hollow stem. Therefore, it is extremely difficult to mechanically finish the sliding part between the hollow stem and the control rod with high precision so that there is no leakage of hydraulic oil from the sliding part. The cost required for this mechanical processing increases significantly, and maintenance and
Inspection was difficult.

Furthermore, the secondary piston in the prior art is moved forward by the supply of hydraulic oil to the hydraulic chamber and retreated by the pressure in the combustion chamber, and when the internal combustion engine is stopped, combustion is stopped. When the pressure in the chamber decreases,
Immediately before engine operation is stopped, the secondary piston remains at a position corresponding to the load. Therefore, when the internal combustion engine is stopped after a low load,
The auxiliary piston remains in the position advanced into the combustion chamber, and the next time the internal combustion engine is started, it will start from a state of high compression ratio, which increases cranking torque and makes starting difficult. At the same time, the starting motor had to be made larger and the required voltage at the spark plug had to be increased.

Moreover, in the prior art, the forward movement of the sub-piston is performed by the pressure in the hydraulic chamber, and the backward movement of the sub-piston is performed by the pressure in the combustion chamber. When the pressure becomes negative, it moves forward due to the pressure in the hydraulic chamber, and when it becomes high during the explosion stroke, it retreats to its original position.This reciprocating motion is repeated once in one cycle, so the relationship between the sub-cylinder and sub-piston is The sliding part between the stem and the control rod suffers a lot of wear, resulting in low durability.

In addition, since the forward movement of the secondary piston is performed by stopping the flow of hydraulic oil from the hydraulic chamber, the responsiveness when moving the secondary piston forward in response to a decrease in the load of the internal combustion engine is good; moves forward as described above during the intake stroke, and this forward movement causes hydraulic oil to flow into the hydraulic chamber. Therefore, when the sub piston retreats in response to an increase in the load of the internal combustion engine, the load increases. The backward movement of the auxiliary piston following this is delayed by the amount of forward movement during the intake stroke.In other words, the responsiveness to a low compression ratio in response to an increase in load is low, causing knocking. Ta.

An object of the present invention is to provide a variable compression ratio internal combustion engine that solves these problems. The aim is to reduce the

[Means for solving problems]

In order to achieve this object, the first invention provides a cylinder head with an auxiliary cylinder that opens into the combustion chamber, a auxiliary piston that is slidably inserted into the auxiliary cylinder, and a hydraulic oil on the back surface of the auxiliary piston. A hydraulic chamber equipped with a supply port is formed, and a stem extending in the axial direction of the sub-cylinder is connected, the tip of the stem protrudes into the upper chamber of the cylinder head, and the protruding end of the stem is connected to a stem extending in the axial direction of the sub-cylinder. A spill port is bored through which hydraulic oil flows out, and the spill port is closed on the outer periphery of the protruding end of the stem when the stem moves backward, and the spill port opens when the stem moves forward. A spill body configured as shown in FIG. spring means is provided to move the spill body to the internal combustion engine, and when the load on the internal combustion engine increases, the opening/closing position of the spill port by the spill body moves backward in proportion to the load;
When the rotational speed of the internal combustion engine is lower than the rotational speed during idling, the opening/closing position of the spill port by the spill body is configured to move backward by a large amount through an actuator.

Further, a second invention is a second invention, in which a spill body is attached to an internal combustion engine in such a manner that the opening/closing position of a spill port by the spill body is moved backward by a large amount when the internal combustion engine decelerates. Added configuration related to.

[Action/effect of the invention]

In such a configuration, when the spill body is moved to close the spill port, the flow of hydraulic oil from the spill port is stopped or reduced, and the sub-piston is moved into the hydraulic chamber. The hydraulic oil supplied to the chamber moves forward toward the combustion chamber, and this forward movement causes the spill to reach a position where the amount of hydraulic oil flowing out from the spill port and the amount of hydraulic oil supplied to the hydraulic chamber are approximately equal. It will stop when the port opens, and if the spill body is moved to open the spill port widely, the amount of hydraulic oil flowing out from the spill port will increase. According to
The auxiliary piston moves backward from the combustion chamber due to the pressure within the combustion chamber and the spring means, and this backward movement occurs at a position where the amount of hydraulic oil flowing out from the spill port and the amount of hydraulic oil supplied to the hydraulic chamber are approximately equal. Since it will stop when the spill port is closed to the extent that the spill port is closed, the sub piston can be moved forward or backward by moving the spill body.

Therefore, by relating the stem to the internal combustion engine via an actuator so that when the load on the internal combustion engine increases, the opening/closing position of the spill port by the spill body moves backward in proportion to the load, the compression ratio can be adjusted. can be automatically changed and controlled according to changes in the load on the internal combustion engine.

In this case, the present invention has the spill body for opening and closing the spill port in the stem fitted onto the outer periphery of the stem, so that the hydraulic pressure in the hydraulic chamber acts to prevent the back and forth movement of the spill body. Since the spill body can be moved back and forth with a light force, the actuator for moving the spill body back and forth in accordance with the load can be made smaller and lighter.

Furthermore, by protruding the stem into the upper chamber of the cylinder head and providing a spill port and a spill body at this protruding end, the sliding portion between the stem and the spill body can be completely closed by the spill port. Since the high-precision mechanical processing to achieve this can be performed much more easily than in the case of the prior art, the cost required for mechanical processing can be reduced and the processing accuracy can be improved. Moreover, maintenance and inspection to maintain a good sliding condition between the stem and the spill body can be performed extremely easily.

Furthermore, by providing a spring means for the sub-piston, the distance when the sub-piston moves forward during the intake stroke can be reduced, so that the sliding portion between the sub-piston and the sub-cylinder and the sliding portion between the stem and the spill body can be reduced. Wear of the moving parts can be reduced and durability can be improved, and the spring means not only reduces the distance that the secondary piston moves forward during the intake stroke, but also accelerates the backward movement of the secondary piston. This improves the responsiveness of the secondary piston's backward movement in response to an increase in load, and as a result, it reliably prevents knocking caused by a delay in controlling the compression ratio to a low level in response to an increase in load. It can be done.

In addition to providing the auxiliary piston with a spring means for biasing it in the backward direction, the present invention also provides a spill body for the internal combustion engine to prevent the spill from occurring when the rotational speed of the internal combustion engine is lower than the rotational speed at idling. The opening/closing position of the spill port caused by the spill body moves backward significantly, so when the internal combustion engine is stopped, the opening/closing position of the spill port caused by the spill body moves backward significantly, and the spill port becomes fully open. As a result, the secondary piston moves backward by the spring means while the operation in the hydraulic chamber flows out from the spill port, and the compression ratio automatically becomes low. Next, when starting the internal combustion engine, the internal combustion engine Since the compression ratio can be maintained at a low state until the engine speed reaches idle speed, the cranking torque when starting the internal combustion engine can be reduced, improving starting performance and making the starting motor smaller and lighter. In addition, the required voltage at the spark plug can be lowered.

On the other hand, when the internal combustion engine decelerates, the sub piston moves forward the most due to the decrease in load, resulting in a high compression ratio, which increases the intake negative pressure toward the vacuum side, and therefore increases the intake air-fuel mixture amount. . On the other hand, when configured as in the second aspect of the invention, when the internal combustion engine is decelerated, the auxiliary piston is moved greatly by fully opening the spill port by moving the opening/closing position of the spill port backward by the spill body and by the spring means. In addition, it is possible to quickly retreat, in other words, the compression ratio can be lowered quickly with priority given to the load, and the intake negative pressure can be lowered, so as the intake negative pressure increases, the intake mixture It is possible to reliably prevent an increase in fuel consumption due to an increase in the amount of fuel.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 is a cylinder block, reference numeral 2 is a cylinder head, reference numeral 3 is a main piston that reciprocates within the cylinder bore 4 of the cylinder block 1, and reference numeral 5 is the cylinder head of the cylinder block 1. Each combustion chamber 5 is formed by recessing the lower surface of the cylinder head 2 into a spherical or polyspherical shape, and the combustion chamber 5 includes an ignition plug 6 at approximately the center thereof, and an intake port and an exhaust port (not shown). It's open.

Reference numeral 7 denotes a sub-cylinder bored in the cylinder head 2, and the sub-cylinder 7 has a lower side facing the combustion chamber 5.
The upper side opens into the upper chamber of the cylinder head 2, respectively, and
A cover plate 8 is provided at the opening of the sub-cylinder 7 to the upper chamber of the cylinder head to close the opening.

Reference numeral 9 denotes a sub-piston that is slidably inserted into the sub-cylinder 7, and a piston ring 9' is provided on the outer periphery of the sub-piston 9, so that the sub-piston 9 moves forward in the direction of the combustion chamber 5. Then, the volume of the combustion chamber decreases, the compression ratio increases, and the secondary piston 9
When the sub-piston 9 moves backward away from the combustion chamber 5, the volume of the combustion chamber increases and the compression ratio decreases.
0, and the sub-piston 9 is so arranged that, when the sub-piston 9 advances to the maximum toward the combustion chamber 5, it comes into contact with the cylinder head 2 side so as not to advance any further. Stepped section 11
is provided to define the position of the highest compression ratio due to the advance of the sub-piston 9. In this case, the top surface 12 of the sub-piston 9 looking into the combustion chamber 5
is formed into a concave spherical shape with the same curvature as the spherical inner wall surface 13 of the combustion chamber 5, and the concave spherical top surface 12 is formed such that the sub-piston 9 reaches the maximum compression specified by the stepped portion 11. It is configured to be continuous with the inner wall surface 13 of the combustion chamber 5 without any difference in level when it advances to the position of the ratio.

A stem 14 extending in the axial direction from the center of the sub-piston 9 is integrally provided on the back surface of the sub-piston 9, and the stem 14 is slidably passed through the cover plate 8 to open the upper chamber of the cylinder head. A hydraulic chamber 15 is formed between the back surface of the sub-piston 9 and the cover plate 8, and hydraulic oil from a hydraulic source is supplied to the hydraulic chamber 15 through a port 17 with a check valve 16. . Further, the stem 14 is provided with a passage 18 communicating with the hydraulic chamber 15, and a portion of the stem 14 protruding outward from the cover plate 8 is provided with a passage 18 communicating with the hydraulic chamber 15.
A spill port 19 is bored to allow the hydraulic oil in the cylinder head to flow out into the upper chamber of the cylinder head.

Reference numeral 20 denotes a spill ring, which is an embodiment of the spill body, and the spill ring 20 is slidably fitted onto the stem 14, and the spill ring 20 is moved forward in the direction of the combustion chamber 5. The spill port 19 is configured to close when the spill ring 20 moves, and to open when the spill ring 20 is moved backward in a direction away from the combustion chamber 5. Further, reference numeral 21 is a lever provided in the upper chamber of the cylinder head with its midway portion pivotally connected to a shaft 23. One end of the lever 21 is engaged with the spill ring 19, while the lever 21 is An actuator 22 operated by a control circuit 24 is connected to the other end, and a signal from a load detector 25 of the engine is inputted to the control circuit 24, so that the spill ring 20 is activated in proportion to an increase in the engine load. It is configured to move in the backward direction using an actuator 22.
Furthermore, the control circuit 24 inputs signals from the engine rotation speed detector 26 and the throttle valve opening detector 27 for adjusting intake air amount, and receives signals from the engine rotation speed detector 26 and the intake air amount adjustment throttle valve opening degree detector 27 when the engine start switch is ON and the engine rotation speed is ON. When the rotational speed does not reach a certain rotational speed lower than the rotational speed at idling, the spill ring 20 is moved largely backward by the actuator 22, and when the opening degree of the throttle valve is at the idle position and the rotational speed is at the rotational speed at idle. The spill ring 20 is connected to the actuator 2
2, when the opening of the throttle valve is at the idle position and the rotational speed is above a certain rotational speed higher than the rotational speed at idle,
The spill ring 20 is configured to be moved largely backward by an actuator 22, giving priority to control by the load.

In this configuration, the spill ring 20 is
When moving in the forward direction from the position shown by the solid line to the position shown by the two-dot chain line in the figure, the spill port 19 is closed and the flow of hydraulic oil from the spill port 19 is stopped, and from the port 17 with the check valve 16. As the pressure in the hydraulic chamber 15 to which hydraulic oil is supplied increases, the sub piston 9 moves forward toward the combustion chamber 5. When this forward movement progresses to the point where the spill port 19 is opened, hydraulic oil is discharged from the spill port 19. begins to flow out, and when this outflow amount and the amount of supply to the hydraulic chamber 15 are balanced, the advance of the sub-piston 9 is stopped.
Furthermore, when the spill ring 20 is moved in the backward direction from the position indicated by the two-dot chain line to the position indicated by the solid line, the spill port 19 is fully opened, the amount of flow from the spill port increases, and the pressure in the hydraulic chamber 15 decreases. ,
The secondary piston 9 retreats away from the combustion chamber due to the pressure of the combustion chamber 5 and the spring 10, and when this retreat progresses to the point where the spill port 19 is closed by the spill ring 20, the amount of outflow from the spill port 19 decreases. decreases and the outflow amount is balanced with the supply amount, the backward movement of the sub-piston 9 stops, and the position of the sub-piston 9 can be changed arbitrarily by moving the spill ring 20, and as a result, The compression ratio can be changed arbitrarily, and in this case, the spill ring 20 is connected to the lever 21 and the actuator 2.
2. Furthermore, by being related to the engine load via the control circuit 24 so as to move backward as the load increases, the compression ratio gradually becomes lower as the engine load increases, and the engine load increases. It is possible to smoothly and automatically control the load so that it gradually increases as the load decreases.

In addition, knocking in an engine becomes less likely to occur as the atmospheric pressure or the temperature of the intake air decreases, and as the humidity of the intake air increases. Since it is related to the temperature of the engine such that it is unlikely to occur, the control circuit 24
Signals from the intake air condition detector 28, such as atmospheric pressure, intake air temperature and humidity, and signals from the engine temperature detector 29 are input, and the compression ratio value is automatically controlled in relation to the engine load. It is also possible to appropriately modify the intake air condition according to the intake air condition such as the intake air temperature and humidity, and the engine temperature.

Next, when starting the engine, the spill ring 20 is in the most retracted position until the engine speed reaches a certain speed lower than the engine speed when idling, and therefore the sub-piston 9 is also supported by the spring 10. Since it is in the most retracted position and is held at the lowest compression ratio, the required voltage at the spark plug can be lower than when starting with a high compression ratio, and the crankshaft can be rotated when starting the engine. During so-called cranking, the rotational torque of the crankshaft can be reduced.

Also, when the engine throttle valve is in the idle position,
During idling when the rotational speed is at the idle speed, the spill ring 20 is at its most advanced position, and therefore the sub-piston 9 is also at its most advanced position and maintained at the highest compression ratio.
Ignition combustion during idling is significantly improved due to the rise in temperature due to the high compression ratio, which makes idling operation more stable and allows the rotation speed to be set lower accordingly.
The amount of unburned harmful components in the exhaust gas is reduced, and the top surface 12 of the sub-piston 9 is continuous with the spherical inner wall surface 13 of the combustion chamber 5 without any step at the highest compression ratio during idling. If a spherical depression is formed in the combustion chamber 5,
The flow of the air-fuel mixture inside the engine is extremely smooth and there are no blind spots, making it more effective.

On the other hand, when the engine is in operation and the throttle valve is suddenly closed to the idle position during deceleration, the spill ring 20 moves back greatly, and the sub piston 9 also moves back quickly and greatly by the spring 10 for compression. ratio becomes lower.

In this case, when the compression ratio is related to the load, when the engine decelerates, the volume of the combustion chamber is minimized, so the pressure in the combustion chamber during the intake stroke increases toward the vacuum side, and the intake air-fuel mixture amount increases. In the present invention, when the engine is decelerated, the compression ratio is lowered in priority to the load as described above, and the volume of the combustion chamber 5 is increased, so that the pressure in the combustion chamber 5 is lowered to the vacuum side during the intake stroke. This makes it possible to prevent the intake air from becoming significantly large, thereby reducing the intake air-fuel mixture amount.

In addition, during the engine's explosion stroke, the secondary piston 9
When the sub-piston 9 receives a large explosive force, the secondary piston 9 moves back slightly due to the explosive force, and the spill port 19 closes, while the hydraulic fluid in the hydraulic chamber 15 becomes trapped within the hydraulic chamber 15. Therefore, this supports a large explosive force against the sub-piston 9. In this case, the outflow of the hydraulic oil until the spill port 19 closes and the subsequent increase in pressure of the hydraulic oil act as a cushion and cause combustion. This absorbs and alleviates the impact on the auxiliary piston 9 due to the explosive combustion of the air-fuel mixture within the chamber 5.

In the above embodiment, the hydraulic oil supplied to the hydraulic chamber 15 may be lubricating oil in an engine, hydraulic oil in a power steering mechanism of an automobile, or hydraulic oil in an automatic transmission of an automobile. In the embodiment, the spill ring 17 is used as an embodiment of the spill body, but as shown in FIGS. 3 and 4, the spill port in the stem 14a is inclined with respect to the axis of the stem 14a. While forming an inclined spill port 19a, the stem 14
A gear-type spill ring 20a is rotatably and slidably fitted on the outer periphery of a.
is pivotally supported on the cylinder head 2 by a bearing (not shown), and the spill ring 20a has one relief port 3 that matches the inclined spill port 19a when the stem 14a slides back and forth.
At the same time, this spill ring 20a is engaged with a gear 31 on the outer periphery of a rack rod 32 having a stem 14a disposed in a perpendicular direction, and the rack rod 32 is moved in the longitudinal direction by an actuator 24 related to the load of the engine. The compression ratio is automatically controlled by rotating the spill ring 20a and shifting the relief port 30 to or from the inclined spill port 19a of the stem 14a. (In this case, stem 1
4a is held slidably but not rotatably, and the mechanism for rotating the spill ring 20a is not limited to the rack and pinion of the embodiment, but other means may also be used).

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 is a longitudinal sectional front view of the main engine parts, FIG. 2 is a sectional view taken from the side of FIG. 1, and FIG.
FIG. 4 is a plan view of FIG. 3. DESCRIPTION OF SYMBOLS 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 6... Spark plug, 7... Sub cylinder, 9... Sub piston, 10... Spring, 15...
...Hydraulic chamber, 14, 14a...Stem, 19, 19
a... Spill port, 20, 20a... Spill body, 22... Actuator, 24... Control circuit,
25...Load detector, 27...Throttle valve opening detector, 26...Rotation speed detector.

Claims (1)

[Claims] 1. The cylinder head is provided with an auxiliary cylinder that opens into the combustion chamber, a auxiliary piston is slidably inserted into the auxiliary cylinder, and a hydraulic oil supply port is provided on the back surface of the auxiliary piston. forming a hydraulic chamber and connecting a stem extending in the axial direction of the sub-cylinder, the tip of the stem protruding into the upper chamber of the cylinder head;
A spill port is provided at the protruding end of the stem to allow the hydraulic oil in the hydraulic chamber to flow out, and
A spill body is disposed on the outer periphery of the protruding end of the stem so that the spill port is closed by the backward movement of the stem and opened by the forward movement of the stem, and the spill port is opened and closed by the spill body. is fitted so as to be relatively movable so that it can be displaced in the axial direction of the stem, and the sub-piston is provided with a spring means for biasing the sub-piston in the backward direction, and the spill body is attached to the internal combustion engine in the internal combustion engine. When the load on the engine increases, the opening/closing position of the spill port by the spill body moves backward in proportion to the load, and when the rotational speed of the internal combustion engine is lower than the rotational speed at idling, the opening/closing position of the spill port by the spill body increases. A variable compression ratio internal combustion engine, characterized in that it is associated with an actuator for backward movement. 2. A sub-cylinder opening into the combustion chamber is provided in the cylinder head, a sub-piston is slidably inserted into the sub-cylinder, and a hydraulic chamber equipped with a hydraulic oil supply port is formed on the back surface of the sub-piston. , connecting a stem extending in the axial direction of the sub-cylinder, the tip of the stem protruding into the upper chamber of the cylinder head,
A spill port is provided at the protruding end of the stem to allow the hydraulic oil in the hydraulic chamber to flow out, and
A spill body is disposed on the outer periphery of the protruding end of the stem so that the spill port is closed by the backward movement of the stem and opened by the forward movement of the stem, and the spill port is opened and closed by the spill body. is fitted so as to be relatively movable so that it can be displaced in the axial direction of the stem, and the sub-piston is provided with a spring means for biasing the sub-piston in the backward direction, and the spill body is attached to the internal combustion engine in the internal combustion engine. When the load on the engine increases, the opening/closing position of the spill port by the spill body moves backward in proportion to the load, and the spill body A variable compression ratio internal combustion engine characterized in that the opening/closing position of a spill port is related via an actuator so that the opening/closing position of the spill port can be moved significantly backward.