JPS6358252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a compression ratio variable device that allows the compression ratio of an internal combustion engine to be changed during operation of the internal combustion engine.

[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 device, a hollow stem is integrally connected from the back side of the sub-piston, and the hollow stem is configured to supply hydraulic oil in the hydraulic chamber to a portion within the hydraulic chamber. While drilling a spill port that allows the flow to flow into the shaped stem,
A control rod having an oil passage communicating with the atmosphere is slidably inserted into the hollow stem, and by sliding the control rod, the opening/closing position of the spill port is adjusted in the axial direction of the stem. Since the auxiliary piston is configured to move back and forth by being displaced, it has the advantage of being able to change the compression ratio steplessly, but has the following problems.

[Problems to be Solved by the Invention] In the prior art, the spill port that is opened and closed by the control rod is provided in a portion inside the hydraulic chamber. Since the sliding part is located at the inner part of the hollow stem, the sliding part between the hollow stem and the control rod is finished with high precision so that there is no leakage of hydraulic oil from the sliding part. When processing, mechanical processing is extremely difficult, the cost required for this mechanical processing increases significantly, and maintenance and inspection to maintain a good sliding condition between the hollow stem and the control rod is difficult. be.

In the prior art, the forward movement of the auxiliary piston is performed by the pressure of hydraulic oil in the hydraulic chamber, and the backward movement of the auxiliary piston is performed by the pressure in the combustion chamber. When the pressure reaches atmospheric pressure (below atmospheric pressure), the pressure in the hydraulic chamber moves it forward, and when the pressure in the combustion chamber increases during the compression stroke, it retreats to its original position. Since the reciprocating movement is repeated, wear increases on the sliding surfaces between the sub-cylinder and the sub-piston, and the sliding surfaces between the stem and the control rod, resulting in low durability.

Moreover, in the compression stroke, when the auxiliary piston moves backward while pushing out the hydraulic oil in the hydraulic chamber from the spill port, the amount of hydraulic oil flowing out from the spill port increases. The amount of hydraulic oil that flows out when the secondary piston retreats to its original position increases as described above, which means that the secondary piston moves backward to follow the backward movement of the control rod. Since there is a delay, the compression ratio of the combustion chamber does not match the control value by the control rods, and becomes a value higher than the control value by the control rods.

In the prior art, the pressure in the hydraulic chamber is equal to the pressure in the combustion chamber by configuring the inner diameter of the hydraulic chamber to be the same as the inner diameter of the sub-cylinder, and therefore,
When the pressure in the combustion chamber reaches the combustion explosion pressure, the pressure in the hydraulic chamber also reaches the combustion explosion pressure, and the amount of hydraulic oil leaking into the combustion chamber from the sliding surface of the sub-cylinder and sub-piston increases. This results in increased consumption and deterioration of exhaust gas, and the supply pressure of hydraulic fluid to the hydraulic chamber must also be increased.

The present invention provides a variable compression ratio device that solves these problems without increasing the size of the device or causing other 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, and the stem extends in the axial direction of the sub-cylinder. The tip of the stem protrudes into the upper chamber of the cylinder head, the protruding end of the stem is provided with a spill port through which the hydraulic oil in the hydraulic chamber flows out, and the protruding end of the stem is provided with a spill port for allowing the hydraulic oil in the hydraulic chamber to flow out. A spill body in which a spill port is closed by a backward motion and opened by a forward motion of a stem is relatively movable so that the opening/closing position of the spill port by the spill body can be displaced in the axial direction of the stem. The sub-piston is provided with a small diameter portion for the combustion chamber and a large diameter portion for the hydraulic chamber, and a large-diameter portion of the sub-piston is slidably fitted into the inner surface of the sub-cylinder. A housing is formed, and a coil spring is provided in the housing, and the coil spring contacts the lower side of the large diameter portion of the sub-piston to bias the sub-piston in the backward direction. It is configured to be connected to a blow-by gas processing unit such as an air cleaner.

[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 secondary piston moves backward from the combustion chamber due to the pressure within the combustion chamber, and this backward movement causes the spill port to move back until 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 sub-piston is stopped when closed, the sub-piston can be moved forward or backward by moving the spill body.

In this case, the present invention protrudes the stem into the upper chamber of the cylinder head and provides the spill port and the spill body at the protruding end. 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.

Moreover, in the present invention, by providing the sub-piston with a coil spring for urging the sub-piston in the backward direction, the sub-piston is moved by the negative pressure of the combustion chamber during the intake stroke of the internal combustion engine. Since the stroke when moving forward can be shortened, wear of the sliding surfaces between the sub-cylinder and the sub-piston, and the sliding surfaces between the stem and the spill body is reduced, and a decrease in durability can be prevented. In addition, being able to shorten the stroke when the sub-piston moves forward during the intake stroke reduces the stroke when the sub-piston retreats to its original position during the compression stroke, which in turn reduces the amount of hydraulic fluid flowing out. At the same time, since the leaf spring accelerates the backward movement of the secondary piston, the delay in the backward movement of the secondary piston following the backward movement of the spill body is reduced, and the compression ratio is higher than the control value of the spill body. It is possible to reduce the occurrence of

Furthermore, in the present invention, the part of the auxiliary piston that corresponds to the combustion chamber is formed to have a small diameter, and the part that corresponds to the hydraulic chamber has a large diameter, so that the pressure in the hydraulic chamber is lower than the pressure in the combustion chamber. The amount of hydraulic oil in the hydraulic chamber leaking from the sliding part between the sub-cylinder and sub-piston to the combustion chamber side can be reduced, reducing the consumption of hydraulic oil and preventing deterioration of exhaust gas. This allows the supply pressure of hydraulic oil to the chamber to be lowered.

However, on the other hand, as the pressure in the hydraulic chamber becomes lower than the pressure in the combustion chamber, the combustion gas in the combustion chamber flows into the hydraulic chamber from the sliding part between the sub-cylinder and the sub-piston. Not only does this accelerate the deterioration of the hydraulic oil, but the combustion gas accumulates in the form of bubbles within the hydraulic chamber, causing a problem in which the back and forth movement of the sub piston is obstructed.

In contrast, in the present invention, a housing that communicates with a blow-by gas processing unit such as an air cleaner in an internal combustion engine is provided on the inner surface of the sub-cylinder so as to surround the circumference of the sub-piston. Combustion gas from the sliding part of the hydraulic chamber to the hydraulic chamber passes through the housing and is extracted to the blow-by gas processing section, which prevents combustion gas from flowing into the hydraulic chamber, thereby preventing deterioration of the hydraulic oil due to mixing of combustion gas. , and the inhibition of the longitudinal movement of the sub piston can be reliably reduced.

Further, in the present invention, the housing is formed such that the part of the sub-piston that is connected to the combustion chamber has a small diameter and the part that is connected to the hydraulic chamber has a large diameter, and the sub-piston is arranged in the housing in a backward direction. By providing a biasing coil spring, it is possible to prevent the structure from becoming complicated and increasing in size, which would otherwise be caused by separately providing a housing for the combustion gas and a housing for the spring.

〔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 piston that reciprocates within the cylinder bore 4 of the cylinder block 1, and reference numeral 5 is the cylinder. Each shows a combustion chamber formed by recessing the lower surface of the head 2, and the combustion chamber 5 has an ignition plug 6 at approximately the center thereof, and
An intake port and an exhaust port (not shown) are 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 on the upper surface of the cylinder head 2, and the opening to the upper chamber of the auxiliary cylinder head is provided with a cover plate 8 for closing the opening.

Reference numeral 9 denotes a sub-piston that is slidably inserted into the sub-cylinder 7. A plurality of piston rings 10 are provided on the outer periphery of the sub-piston 9 in a portion close to the combustion chamber 5, and the sub-piston When the secondary 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, and when the sub piston 9 moves back away from the combustion chamber 5, the volume of the combustion chamber 5 increases and the compression ratio decreases. A stem 11 extending in the axial direction from the center of the sub-piston 9 is connected to the back surface of the sub-piston 9.
The piston extends slidably through the cover plate 8 and protrudes into the upper chamber of the cylinder head, while forming a hydraulic chamber 12 between the back surface of the sub-piston 9 and the cover plate 8. Check valve 1 prevents hydraulic fluid from coming from a hydraulic source.
3 through the port 14.

A portion 9a of the sub-piston 9 corresponding to the combustion chamber 5 is formed to have a small diameter, and a portion 9b corresponding to the hydraulic chamber 12 is formed to have a large diameter. A housing 19 that can be fitted freely is formed, and the housing 1
A coil spring 23 for biasing the sub-piston 9 in the backward direction is provided in the sub-piston 9 so as to come into contact with the lower side of the large diameter portion 9a of the sub-piston 9.
Further, the housing 19 is communicated with a blow-by gas processing section 22 such as an air cleaner (not shown) in an internal combustion engine or an intake passage (not shown) of an internal combustion engine through a through hole 20 and a passage 21 connected thereto. do. A chamfer 24 is provided at the corner of the housing 19 and the sub-cylinder 7 to facilitate insertion of the sub-piston 9.

On the other hand, the stem 11 is provided with a passage 15 communicating with the hydraulic chamber 12, and a portion of the stem 11 protruding outward from the cover plate 8 is provided with a passage 15 communicating with the hydraulic chamber 12.
A spill port 16 is provided to allow the hydraulic oil in the cylinder head 2 to flow out into the upper chamber of the cylinder head.

Reference numeral 17 designates a spill ring, which is an embodiment of the spill body, and the spill ring 17 is slidably fitted onto the end of the stem 11 that projects into the upper chamber of the cylinder head, thereby preventing the backward movement of the stem 11. The spill port 16 is closed by the spill ring 17 when the stem 11 moves forward, and the spill port 16 is opened when the stem 11 moves forward. It is configured to adjust the movement of the stem 11 in the axial direction by rotation.

In this configuration, the spill ring 17 is
If the movement is performed in the direction of the combustion chamber 5, that is, in the direction of closing the spill port 16 as shown by the two-dot chain line in the figure, the flow of hydraulic oil from the spill port 16 will be stopped by closing the spill port 16, and the flow will be reversed. Stop valve 13
Since the pressure in the hydraulic chamber 12 to which hydraulic oil is supplied from the attached port 16 increases, the sub-piston 9
It moves forward toward the combustion chamber 5 against the coil spring 20, and when this forward movement progresses to the point where the spill port 16 opens, hydraulic oil starts flowing out from the spill port 16, and the amount of this outflow and the flow into the hydraulic chamber 12 are The forward movement of the sub piston 9 stops when the supply amount is balanced. Furthermore, when the spill ring 17 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 16 is fully opened, the amount of flow from the spill port 16 increases, and the pressure in the hydraulic chamber 12 decreases. Therefore, the secondary piston 9 retreats away from the combustion chamber 5 due to the pressure in the combustion chamber 5 and the coil spring 20, and when this retreat progresses to the point where the spill port 16 is closed by the spill ring 17, the spill port is closed. When the outflow amount from 16 decreases and the outflow amount is balanced with the supply amount, the backward movement of the sub piston 9 is stopped, and by moving the spill ring 17, the sub piston 9 is moved.
It can be moved back and forth steplessly.

Therefore, an actuator 25 related to the engine load is connected to the other end of the lever 18 that engages with the spill ring 17, and the actuator 25 moves the spill ring 17 in proportion to the increase in engine load. If the compression ratio is moved backward from the position of It can also be automatically controlled so that it gradually increases as the engine speed increases, and
The actuator 25 can also be automatically controlled in conjunction with a knocking sensor provided in the engine so that the compression ratio is high when there is no knocking and is lowered accordingly when knocking occurs.

During the engine's explosion stroke, when the secondary piston 9 receives a large explosive force, the secondary piston 9 moves back slightly due to this explosive force, closing the spill port 16, while the pressure inside the hydraulic chamber 12 momentarily increases. When the check valve 13 closes, the hydraulic fluid in the hydraulic chamber 12 becomes confined within the hydraulic chamber 12.
This supports a large explosive force against the secondary piston 9, and in this case, the outflow of hydraulic oil and its pressure rise until the spill port 16 closes is caused by the explosion and combustion of the air-fuel mixture in the combustion chamber 5. This absorbs and softens the impact on the sub-piston 9.

In the above embodiment, the coil spring 23 urges the sub-piston 9 in the backward direction.
is not provided, when negative pressure (below atmospheric pressure) is generated in the combustion chamber 5 during the intake stroke of the engine, the sub piston 9 absorbs this negative pressure and the pressure chamber 1.
It moves forward toward the combustion chamber 5 due to the pressure in the combustion chamber 2, and retreats to its original position during the next compression/explosion stroke, thus reciprocating once per cycle depending on the pressure change in the combustion chamber 5. It turns out.

In contrast, in the present invention, the sub-piston 9 is provided with a coil spring 23 that biases it in the backward direction.
Even if negative pressure is generated in the combustion chamber 5 during the intake stroke of the engine, the auxiliary piston 9 is prevented from moving forward in the direction of the combustion chamber 5 by the coil spring 23 provided for the auxiliary piston 9. The stroke when the sub-piston 9 reciprocates in each cycle can be reduced.

Further, by forming the portion 9a of the sub-piston 9 that is connected to the combustion chamber 5 to have a small diameter, and the portion 9b that is connected to the hydraulic chamber 12 to have a large diameter, the pressure in the hydraulic chamber 12 is lower than the pressure in the combustion chamber 5.

However, on the other hand, since the pressure in the hydraulic chamber 12 becomes lower than the pressure in the combustion chamber 5, combustion gas in the combustion chamber 5 is leaked from the sliding portion between the sub cylinder 7 and the sub piston 9 into the hydraulic chamber 12. The flow will flow towards the sub cylinder 7 and sub piston 9.
Since the combustion gas flowing toward the hydraulic chamber 12 through the sliding portion between the housing 19 and the blow-by gas processing section 22 is sequentially extracted from the housing 19, the combustion gas flowing into the hydraulic chamber 12 can be reduced.

Note that as the hydraulic oil supplied to the hydraulic chamber 12, 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 can be used. The hydraulic oil tends to leak toward the combustion chamber 5 through the sliding portion between the large diameter portion 9b of the sub-piston 9 and the sub-cylinder 7 during the intake stroke when the pressure in the combustion chamber 5 is low. The combustion gas extracted from the housing 19 may be contaminated with hydraulic oil. However, in most common engines, the valve mechanism for the intake and exhaust valves is installed in the upper chamber of the cylinder head, and the lubricating oil for this valve mechanism is dropped from the upper chamber of the cylinder head to the oil pan at the bottom of the crankcase.
Blowby gas leaking from the sliding parts of the intake and exhaust valves and the main piston 3 is collected in the upper chamber of the cylinder head, where oil is separated and the blowby gas is introduced into the intake air cleaner or intake passage. When using engine lubricating oil as the hydraulic oil for the hydraulic chamber 12, it is sufficient to connect the housing 19 for the sub-piston 9 to the upper chamber of the cylinder head, and as the hydraulic oil for the hydraulic chamber 12, When hydraulic oil is used in the power steering mechanism or automatic transmission of an automobile, a passage 26 branching from these hydraulic oil pumps is connected to the hydraulic chamber 12 with a check valve 13, as shown in FIGS. 3 and 4. A cover 27 is connected to the port 14 and covers the spill ring 17 and the stem 11 on the outside of the cover plate 8.
6 is returned to the oil pan of the power steering mechanism or automatic transmission through a passage 28 connected to the cover 27. At a location close to the hydraulic chamber 12,
If an annular groove 29 surrounding the circumference of the sub-piston 9 is provided and the annular groove 29 is configured to communicate with the inside of the cover 27 through a through hole 30 bored in the stem 11, the sub-piston can be removed from the hydraulic chamber 12. The pressure of the hydraulic oil leaking toward the combustion chamber 5 through the sliding part between the large-diameter portion 9b and the sub-cylinder 7 in the annular groove 29 decreases, and from there it flows into the through hole 30.
Since the hydraulic oil is guided into the cover 27 through the housing 19, it is possible to reliably prevent the hydraulic oil from leaking into the housing 19. In this case,
It is more effective if an O-ring 31 is provided below the annular groove 29. In addition, the structure in which the annular groove 29 is provided in the sliding contact portion between the sub-piston 9 and the sub-cylinder 7 in order to prevent the hydraulic oil in the hydraulic chamber from leaking into the housing 19 allows the hydraulic oil to flow into the hydraulic chamber. Needless to say, this method can also be applied when using engine lubricating oil.

Further, in the above embodiment, a spill ring 17 was used as an embodiment of the spill body, but
As shown in FIG. 5, a stem 11a is formed into a hollow shaft, a spill rod 17a is slidably inserted into the stem 11a, and the spill port 16a is opened by slidingly operating the spill rod 17a. The opening/closing position may be configured to be displaced along the axial direction of the stem 11a, and as shown in FIGS. While forming the inclined spill port 16b, the stem 11b
A gear-type spill ring 17b is rotatably and slidably fitted on the outer periphery of the spill ring 17.
b is pivotally supported on the cylinder head 2 by a bearing (not shown), and the stem 1 is attached to this spill ring 17b.
One escape port 32 is bored to match the inclined spill port 16b when the spill ring 1b slides back and forth, and the spill ring 17b
A rack rod 33 disposed perpendicularly to the stem 11b is engaged with teeth on the outer periphery, and the rack rod 33 is slid in the longitudinal direction of the actuator 25 to rotate the spill ring 17b, thereby tilting the stem 11b. The relief port 32 is connected to the shaped spill port 16b.
By shifting the opening and closing position of the spill port 16b to the position of the stem 11
It may be configured to be displaced along the axial direction of b. (In this case, the stem 11b is held slidably but not rotatably, and the mechanism for rotating the spill ring 17b here is not limited to the rack and pinion shown in the embodiment diagram, but other means may be used. Yes, it goes without saying). Furthermore, it goes without saying that the positions of the inclined spill port provided on the stem and the relief port provided on the spill ring may be reversed.
As for the material of the sub-piston 9, aluminum alloy may be used like the main piston 3, but a part or all of it may be made of ceramic.

In this case, if the material of the part of the sub-piston 9 on the combustion chamber side is made of ceramic, the amount of heat released from the combustion chamber will decrease because ceramic has low thermal conductivity.
The increased insulation effect reduces heat loss and improves fuel efficiency. Furthermore, since the amount of heat transferred from the combustion chamber to the back surface of the sub-piston is reduced, the temperature rise of the liquid that slides the compression ratio changing sub-piston is reduced, so deterioration of the hydraulic oil is reduced.

In addition, if ceramic is used for the sliding surface of the secondary piston against the secondary cylinder, it has high wear resistance and a low coefficient of friction, so less liquid (lubricating oil) is required to lubricate the sliding surface, so it is possible to use less oil. The amount of oil drop is also reduced, which prevents deterioration of exhaust gas and increase in oil consumption.

Furthermore, the port shapes provided in the stem and the spill ring may be combined in any desired shape as shown by the two-dot chain line in FIG. 6, if necessary.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a longitudinal sectional front view of the main engine parts showing the first embodiment, FIG. 2 is a sectional view taken from the side of FIG. 1, and FIG. FIG. 4 is an enlarged view of the main part of FIG. 3, FIG. 5 and FIG. 6 are views of another embodiment of the spill port and spill body, and FIG. FIG. 6 is a plan view of FIG. 6; DESCRIPTION OF SYMBOLS 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 7... Sub cylinder, 9... Sub piston, 9a... Small diameter part of sub piston, 9b...
...Large diameter part of sub-piston, 12...Hydraulic chamber, 11...
...Stem, 16, 16a, 16b... Spill port, 13... Check valve, 17, 17a, 17b...
Spill body, 19...Housing, 20...Through hole,
22...Blowby gas processing section.

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. On the other hand, 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 provided at the protruding end of the stem to allow the hydraulic oil in the hydraulic chamber to flow out, and the spill port is closed by the backward movement of the stem and opened by the forward movement of the stem. A spill body configured as shown in FIG. is formed to have a large diameter, and a housing is formed on the inner surface of the sub-cylinder, into which the large-diameter portion of the sub-piston is slidably fitted; A coil spring is provided which contacts the sub-piston and urges it in the backward direction, and further,
A variable compression ratio device for an internal combustion engine, characterized in that the housing is connected to a blow-by gas processing unit such as an air cleaner in the internal combustion engine.