JPH0116974B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a variable compression ratio type that automatically and responsively changes the compression ratio of an internal combustion engine in accordance with the operating conditions of the internal combustion engine. This relates to internal combustion engines.

[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.

This prior art compression ratio internal combustion engine is
A hollow stem is integrally connected from the back side of the sub-piston, and the hollow stem is provided with a spill port at a portion within the hydraulic chamber so that the hydraulic oil in the hydraulic chamber flows out into the hollow stem. While drilling, a control rod having an oil passage communicating with the atmosphere is slidably inserted into the hollow stem, and the control rod is connected to an actuator related to intake negative pressure in an internal combustion engine. , it moves forward when the intake negative pressure increases toward the vacuum side, and moves backward when the intake negative pressure becomes less than atmospheric pressure, so the compression ratio in the internal combustion engine can be adjusted according to changes in the load on the internal combustion engine. Although it has the advantage of being able to be changed automatically and steplessly according to the requirements, it also has the following problems.

[Problem that the invention seeks to solve]

That is, in the prior art, the opening/closing position of the spill port in the hollow stem is displaced in the axial direction of the stem by the back and forth movement of a control rod slidably inserted into the hollow stem. When the control rod moves back and forth, the hydraulic pressure of the hydraulic oil in the hydraulic chamber acts to prevent the control rod from moving back and forth.In other words, a large force is required to move the control rod back and forth. Therefore, the actuator for moving the control rod back and forth by the intake negative pressure must be made large, and
The responsiveness of changing the compression ratio in accordance with the load of the internal combustion engine is low.

Moreover, in the prior art, the spill port, which is opened and closed by the control rod, is provided inside the hydraulic chamber. In other words, the sliding portion between the hollow stem and the control rod is hollow. Because it is located at the back of the hollow stem, it is 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. Machining is extremely difficult, and the cost required for this mechanical processing increases significantly.
Maintenance and inspection to maintain a good sliding condition between the hollow stem and the control rod was difficult.

Moreover, the secondary piston in this prior art is
It moves forward due to the supply of hydraulic oil to the hydraulic chamber on the rear side and moves backward due to the pressure in the combustion chamber.When the internal combustion engine stops operating and the pressure in the combustion chamber decreases, the The piston remains at the position corresponding to the load immediately before the internal combustion engine stops operating, and therefore, when the internal combustion engine stops operating after a low load, the piston remains at the position that is most advanced toward the combustion chamber. It stays in place and the compression ratio is high.
Next, when starting an internal combustion engine, it must be started from a high compression ratio state, which increases cranking torque and makes starting difficult, and the starting motor becomes larger. First, the required voltage at the spark plug had to be increased.

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

[Means for solving problems]

To achieve this object, the present invention provides a cylinder head with an auxiliary cylinder opening into the combustion chamber, a auxiliary piston slidably inserted into the auxiliary cylinder,
A hydraulic chamber is formed on the back surface of the sub-piston, and a port for supplying hydraulic oil is connected to the hydraulic chamber, while a stem extending in the axial direction of the sub-cylinder is connected to the back surface of the sub-piston. The tip of the stem protrudes into the upper chamber of the cylinder head, a spill port is bored at the protruding end of the stem through which the hydraulic oil in the hydraulic chamber flows out, and the outer periphery of the protruding end of the stem includes: A spill body is configured such that the spill port is closed by the backward movement of the stem and opened by the forward movement of the stem, and the opening/closing position of the spill port by the spill body is displaceable in the axial direction of the stem. The spill body is slidably fitted into a pressure-operated actuator related to the intake negative pressure to the internal combustion engine, and when the intake negative pressure increases toward the vacuum side, the spill body is advanced, and the intake negative pressure becomes atmospheric pressure. The pressure-operated actuator is provided with a spring that urges the spill body in a backward direction, and the tip of the stem further includes a spring that urges the spill body in a backward direction. A stopper means is provided to prevent the spill port from moving toward the distal end of the stem from the fully open position.

[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 oil pressure 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 is approximately equal to the amount of hydraulic oil supplied to the hydraulic chamber. 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 this backward movement causes the spill port to reach a position where the amount of hydraulic oil flowing out from the spill port is approximately equal to the amount of hydraulic oil supplied to the hydraulic chamber. Since the piston stops when the piston is closed, the sub-piston can be moved forward or backward by moving the spill body.

Therefore, this spill body is connected to a pressure-operated actuator related to the intake negative pressure to the internal combustion engine, and when the intake negative pressure increases toward the vacuum side, the spill body is advanced, and when the intake negative pressure becomes smaller than atmospheric pressure, the spill body is activated. The compression ratio can be varied automatically and steplessly in response to changes in the load on the internal combustion engine.

In this case, the present invention, as described above,
Since the spill body for opening and closing the spill port in the stem is fitted so as to be movable relative to the outer periphery of the stem, the back and forth movement of this spill body is achieved by using hydraulic oil in the hydraulic chamber as in the prior art. Since the hydraulic pressure does not act to impede the back and forth movement of the spill body, the spill body can be moved back and forth with extremely light force, regardless of the hydraulic pressure of the hydraulic fluid in the hydraulic chamber.

In other words, since the spill body can be moved back and forth with extremely light force, the actuator that moves this spill body back and forth in response to the negative pressure of the intake air to the internal combustion engine can be made smaller and lighter, and the actuator can be made smaller and lighter. This makes it possible to improve the responsiveness of changing the compression ratio in accordance with the change in compression ratio.

Moreover, in the present invention, the stem protrudes into the upper chamber of the cylinder head, and a spill port and a spill body are provided at this protruding end, so that the sliding portion between the stem and the spill body is changed from the spill port to the spill body. High-precision mechanical processing for completely closing can be performed much more easily than in the case of the prior art, so the cost required for mechanical processing can be reduced and processing accuracy can be improved. Furthermore, maintenance and inspection to maintain a good sliding condition between the stem and the spill body can be carried out extremely easily.

Furthermore, when the operation of the internal combustion engine is stopped, the intake negative pressure to the internal combustion engine becomes atmospheric pressure, and the spring provided in the actuator moves the spill body backward.
Since the spill body contacts the stopper means at the tip of the stem with the spill port in the stem fully open, the secondary piston is moved back while discharging the hydraulic fluid in the hydraulic chamber from the spill port by the spring provided in the actuator. It moves you.

As a result, when the internal combustion engine is stopped, the secondary piston is automatically retracted from the combustion chamber to a low compression ratio position, and the next time the internal combustion engine is started, it can be started from a low compression ratio state. This makes it possible to reduce the cranking torque during starting, improve starting performance in variable compression ratio internal combustion engines, make the starting motor smaller and lighter, and further reduce the required voltage at the spark plug. This is possible.

The present invention automatically retracts the auxiliary piston when the internal combustion engine is stopped, using the spring in the actuator and the stopper means provided at the tip of the stem, as described above. The structure of automatically retracting the auxiliary piston when the internal combustion engine stops operating is extremely simple, and this does not result in an increase in size or weight. Automatic retraction of the piston can be achieved without increasing the complexity, size, and weight of the structure.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 indicates a cylinder block, reference numeral 2 indicates a cylinder head, and reference numeral 3 indicates a piston that reciprocates within the cylinder bore 4 of the cylinder block 1. Reference numeral 5 indicates a combustion chamber formed by recessing the lower surface of the cylinder head 2, and the combustion chamber 5 has the cylinder head 2 located approximately in the center thereof.
An ignition plug 6 screwed onto the ignition plug 6 is visible, and an intake port and an exhaust port (not shown) are open.

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

Reference numeral 9 indicates a sub-piston slidably inserted into the sub-cylinder 7, and when the sub-piston 9 moves forward in the direction of the combustion chamber 5, the volume of the combustion chamber 5 decreases and the compression ratio increases; When the secondary piston 9 retreats in a direction away from the combustion chamber 5, the volume of the combustion chamber 5 increases and the compression ratio decreases.
A stem 10 extending axially from the center of the sub-piston 9 is connected to the sub-piston 9. The stem 10 extends slidably through the cover plate 8 and protrudes into the upper chamber of the cylinder head. A hydraulic chamber 11 is formed between the back surface and the general plate 8, and hydraulic oil from a hydraulic source (not shown) is supplied to the hydraulic chamber 11 via a port 13 with a check valve 12.

Further, the stem 10 is provided with a passage 14 communicating with the hydraulic chamber 11, and a portion of the stem 10 protruding outward from the cover plate 8 is provided with a passage 14 communicating with the hydraulic chamber 11.
A spill port 15 is bored to allow the hydraulic oil in the cylinder head to flow out into the upper chamber of the cylinder head.

Reference numeral 16 indicates a spill ring which is one embodiment of the spill body, and the spill ring 16
is slidably fitted onto the stem 10, and when the spill ring 16 is moved forward in the direction of the combustion chamber 5, the spill port 1 is opened by the spill ring 16.
5 is closed and the spill port 15 is configured to open when the spill ring 16 is moved backward in a direction away from the combustion chamber 5. On the other hand, at the upper end of the stem 10,
A snap ring 17 is provided as one embodiment of a stopper means for preventing the spill ring 16 from coming off toward the upper end of the stem 10 from the fully open position of the spill port 15.

Reference numeral 18 designates a lever that is pivotally mounted at its midpoint on the upper surface of the cylinder head 2 with a shaft 19, and one end of the lever 18 is attached to the spill ring 16 so as to allow the lever 18 to swing. spill ring 16 is slidably engaged, while the other end is connected to a diaphragm mechanism 20, which is one embodiment of a pressure actuator.

This diaphragm mechanism 20 includes the lever 18
A diaphragm 22 connected to the other end via a rod 21 is built in, and a pressure chamber 23 defined by the diaphragm 22 has a pressure chamber 23 in which the other end of the lever 18 is pushed downward in the figure, that is, the spill ring 16 Spring 2 that biases in the direction of sliding backwards
4, the pressure chamber 23 is connected to the intake manifold (not shown) of the engine via the negative pressure transmission passage 25, and intake pipe negative pressure is introduced into the pressure chamber 23, thereby reducing the engine load. As the intake pipe negative pressure increases toward the vacuum side as the engine load decreases, the spill ring 16 slides forward in proportion to this, and as the engine load increases, the intake pipe negative pressure becomes smaller than atmospheric pressure. While the spill ring 16 is configured to slide backward in proportion to inner spring 24
The spill ring 16 is configured so that it can be slid back a large distance.

In this configuration, the spill ring 16 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 15 is closed and the flow of hydraulic oil from the spill port 15 is stopped, and from the port 13 with the check valve 12. As the pressure in the hydraulic chamber 11 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 15 is opened, hydraulic oil is discharged from the spill port 15. begins to flow out, and when this outflow amount and the amount of supply to the hydraulic chamber 11 are balanced, the advance of the sub-piston 9 is stopped.

Furthermore, when the spill ring 16 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 15 is fully opened, the amount of flow from the spill port increases, and the pressure in the hydraulic chamber 11 decreases.
The secondary piston 9 retreats away from the combustion chamber 5 due to the pressure within the combustion chamber 5, and when this retreat progresses to the point where the spill port 15 is closed by the spill ring 16, the amount of flow out from the spill port 15 decreases. However, when the outflow amount is balanced with the supply amount, the backward movement of the sub-piston 9 is stopped, and the sub-piston 9 can be moved back and forth in a stepless manner by moving the spill ring 16 back and forth. can.

By connecting this spill ring 16 to the diaphragm mechanism 20 operated by intake pipe negative pressure via the lever 18, when the intake pipe negative pressure gradually increases toward the vacuum side as the engine load decreases, This negative pressure causes the spill ring 16 to advance from the solid line position to the two-dot chain line position, so the compression ratio automatically increases as the engine load decreases, and the intake air increases as the engine load increases. When the tube negative pressure gradually becomes lower than atmospheric pressure, the spill ring 16
is moved back from the position indicated by the two-dot chain line to the position indicated by the solid line by the spring 24 in the pressure chamber 23. Therefore, the compression ratio gradually decreases as the engine load increases. It can be automatically changed according to changes in

Then, when the engine's ignition key switch (not shown) is turned off to stop engine operation,
Since the inside of the intake manifold becomes atmospheric pressure and the negative pressure in the intake pipe disappears, the spring 24 in the pressure chamber 23 causes the spill ring 16 to move back greatly. The stem 10 and, in turn, the secondary piston 9 are brought into contact with the spring 2 by contacting the snap spring 17.
Because it moves backward away from the combustion chamber at step 4,
The compression ratio is automatically reduced to a low value as soon as the internal combustion engine is stopped. Therefore, the next time you start the internal combustion engine, the compression ratio will be held at a low value until the internal combustion engine is completely started and the intake pipe negative pressure increases toward the vacuum side, so it will start at a high compression ratio. There is no need to increase the required voltage at the spark plug, as is the case when starting the engine, and the rotational torque of the crankshaft can be reduced during cranking when starting the engine.

The hydraulic oil supplied to the hydraulic chamber 11 may be lubricating oil in the engine, but it is also possible to use hydraulic oil in the power steering mechanism or automatic transmission of an automobile.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a vertical sectional front view of the main engine part showing the first embodiment, and FIG. 2 is a sectional view taken along the line in FIG. 1. 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 7... Sub cylinder, 9... Sub piston, 10... Stem, 11... Hydraulic chamber, 1
5... Spill port, 16... Spill body, 20...
...Diaphragm mechanism as actuator, 24
... Spring, 17 ... Snap spring as a stopper means.

Claims (1)

[Claims] 1. A sub-cylinder opening into the combustion chamber is provided in the cylinder head, a sub-piston is slidably inserted into the sub-cylinder, a hydraulic chamber is formed on the back surface of the sub-piston, and hydraulic oil is supplied to the hydraulic chamber. At the same time, a stem extending in the axial direction of the sub-cylinder is connected to the back surface of the sub-piston, the tip of the stem projects into the upper chamber of the cylinder head, and the protruding end of the stem includes: A spill port is bored through which the hydraulic oil in the hydraulic chamber flows out, and the spill port is closed on the outer periphery of the protruding end of the stem by the backward movement of the stem, and no spill is caused by the forward movement of the stem. A spill body with an open port is slidably fitted so that the opening/closing position of the spill port by the spill body can be displaced in the axial direction of the stem, and the spill body is connected to the intake negative pressure to the internal combustion engine. The pressure-operated actuator is associated with a pressure-operated actuator that advances the spill body when the intake negative pressure increases toward the vacuum side, and retracts the spill body when the intake negative pressure becomes smaller than atmospheric pressure. is provided with a spring that urges the spill body in the backward direction, and further includes a stopper at the tip of the stem to prevent the spill body from moving toward the tip of the stem from the fully open position of the spill port. A variable compression ratio internal combustion engine characterized by being provided with means.