JPH0116969B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a compression ratio variable device that can change the compression ratio of an internal combustion engine with a simple structure and responsiveness during operation. It is something.

[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 low value that does not cause knocking in the low and high speed ranges, it is not possible to produce sufficient output and sufficient fuel efficiency in the low load range.

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 in a stepless manner, but has the following problems.

[Problem that the invention seeks to solve]

That is, 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. In other words, the sliding portion between the hollow stem and the control rod is Because it is located at the back of the shaft, mechanical processing is required when finishing 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. This is extremely difficult, and 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.

Moreover, in the prior art variable compression ratio device, the inner diameter of the hydraulic chamber formed on the back surface of the sub-piston is configured to have the same dimensions as the inner diameter of the sub-cylinder, so that the pressure of the hydraulic oil in the hydraulic chamber is controlled by combustion. Therefore, when the combustion chamber reaches the combustion explosion pressure, the pressure of the hydraulic oil in the hydraulic chamber becomes extremely high, the same as the combustion explosion pressure, and the hydraulic oil in the hydraulic chamber reaches the combustion explosion pressure. As more leaks from the sliding part between the inner surface and the auxiliary piston into the combustion chamber, the amount of hydraulic oil consumed increases.
This leads to deterioration of exhaust gas. Furthermore, in order to move the auxiliary piston forward against the pressure of the combustion chamber by supplying hydraulic oil to the hydraulic chamber, the pressure of hydraulic oil supplied to the hydraulic chamber must be increased. In order to increase the supply pressure of hydraulic oil to the hydraulic chamber, the discharge pressure of the hydraulic pump for the hydraulic oil must be increased. When driven by an engine, the power loss of the internal combustion engine increases, and in some cases, lubricating oil in the internal combustion engine or power steering in a car may be used as the hydraulic oil for the hydraulic chamber. It may not be possible to use hydraulic fluid in the mechanism or a hydraulic pump in an automatic transmission mechanism.

Moreover, in the prior art, when the pressure in the combustion chamber becomes negative pressure (below atmospheric pressure) during the intake stroke, there is a large pressure between the hydraulic pressure of the hydraulic oil constantly supplied in the hydraulic chamber and the combustion chamber. Once per cycle, the secondary piston moves forward toward the combustion chamber due to the difference, and then moves back to its original position when the pressure in the combustion chamber increases during the next compression stroke. Since the reciprocating motion is repeated, the sliding parts between the auxiliary piston and the auxiliary cylinder, and the sliding parts between the hollow stem and the control rod are subject to large wear, resulting in low durability.

Furthermore, since the forward movement of the secondary piston is performed by stopping the flow of hydraulic oil from the hydraulic chamber at the back of the secondary piston, the responsiveness when moving the secondary piston forward by forward operation of the control rod is good. On the other hand, the secondary piston moves forward toward the combustion chamber during the intake stroke as described above, and this forward movement causes hydraulic oil to flow into the hydraulic chamber. When retracting the secondary piston by increasing the amount of oil flowing out,
The backward movement of the secondary piston is delayed by the amount of forward movement during the intake stroke. In other words, the responsiveness of the backward movement of the secondary piston to the backward movement of the control rod is reduced, and the compression ratio of the combustion chamber is The value tends to be higher than the set value by the control rod, and in particular, the tendency for these tilting movements, that is, the tendency for the response of the backward movement of the auxiliary piston to decrease, and the tendency for the compression ratio to increase, are caused by the rotation speed of the internal combustion engine. It became more noticeable as the time progressed.

An object of the present invention is to provide a variable compression ratio device that solves these problems of the prior art without complicating the structure or increasing the size.

[Means for solving problems]

In order to achieve this object, the present invention forms an auxiliary cylinder opening into the combustion chamber in the cylinder head, a auxiliary piston is slidably inserted into the auxiliary cylinder, and a hydraulic chamber is formed on the back surface of the auxiliary piston. form,
A hydraulic oil supply port is connected to the hydraulic chamber, and the sub-piston is provided with a spring means for biasing the sub-piston in a backward direction, while a spring means is provided on the back surface of the sub-piston and extends in the axial direction of the sub-cylinder. The stems are connected so that the tip of the stem projects into the upper chamber of the cylinder head, and the projecting end of the stem is provided with a spill port through which the hydraulic oil in the hydraulic chamber flows out. At the protruding end, a spill body is arranged 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 in the axial direction of the stem. The secondary piston is provided relatively movably so as to be able to be displaced, and furthermore, the sub piston is configured such that a portion of the auxiliary piston that corresponds to the combustion chamber has a small diameter, and a portion of the sub piston that corresponds to the hydraulic chamber has a large diameter.

[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 hydraulic 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 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.

In this case, the present invention, as described above,
The part of the sub-piston facing the combustion chamber is made smaller in diameter.
By forming the part corresponding to the hydraulic chamber with a large diameter, the pressure of the hydraulic oil in the hydraulic chamber is equal to the pressure in the combustion chamber multiplied by the square of the diameter ratio of the small diameter to the large diameter in the sub piston. This means that the pressure will be lower than the pressure in the combustion chamber, so the amount of hydraulic oil in the hydraulic chamber leaking into the combustion chamber from the sliding part between the inner surface of the sub-cylinder and the sub-piston can be reduced.
Not only can the consumption of hydraulic oil be reduced, but also the deterioration of exhaust gas can be prevented. Also, since the hydraulic pressure of the hydraulic oil supplied to the hydraulic chamber can be lowered, the hydraulic pump for the hydraulic oil can be made smaller and lighter. In addition, when the hydraulic pump for hydraulic oil is driven by an internal combustion engine, the power loss of the internal combustion engine can be reduced. The hydraulic oil or the hydraulic oil in the automatic transmission mechanism of an automobile can be used as it is as the hydraulic oil for the hydraulic chamber.

Moreover, in the present invention, the stem projects into the upper chamber of the cylinder head, and the spill port and the spill body are provided at the projecting end, so that the sliding portion between the stem and the spill body is replaced by the spill port. Since high-precision mechanical processing for completely closing can be performed much more easily than in the case of the prior art, the cost required for mechanical processing can be reduced and 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.

Moreover, the present invention provides for the secondary piston,
By providing a spring means that biases the secondary piston in the backward direction, when a large pressure difference occurs between the combustion chamber and the hydraulic chamber during the intake stroke, the secondary piston moves forward due to this pressure difference. Since the distance between the sliding parts of the sub-piston and the sub-cylinder can be reduced by the spring means,
The wear of the sliding parts between the stem and the spill body, as well as their durability, can be improved without complicating the structure, increasing the size, and increasing the weight.

Furthermore, the spring means provided for the secondary piston is
As mentioned above, by reducing the distance that the auxiliary piston moves forward during the intake stroke, the amount of hydraulic oil that flows into the hydraulic chamber during this forward movement is reduced, and the backward movement of the auxiliary piston is accelerated, thereby reducing spills. When the secondary piston is retracted by increasing the amount of hydraulic oil flowing out from the spill port in the hydraulic chamber by retracting the body, the delay in the backward movement of the secondary piston can be reduced. The responsiveness of the backward movement of the auxiliary piston to the operation can be improved, and the tendency for the compression ratio to become higher than the set value due to the spill body can be reliably reduced.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings (FIG. 1). In the drawing, reference numeral 1 is a cylinder block, reference numeral 2 is a cylinder head, and reference numeral 3 is 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 an ignition plug 6 screwed onto the cylinder head 2 at approximately the center thereof, and an intake air (not shown). Port and exhaust port are open.

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

Reference numeral 9 denotes a sub-piston that is slidably inserted into the sub-cylinder 7, and the sub-piston 9 is inserted into the combustion chamber 5.
When the secondary piston 9 moves forward in the direction of , the volume of the combustion chamber 5 decreases and the compression ratio becomes high, and when the sub piston 9 moves backward away from the combustion chamber 5, the volume of the combustion chamber 5 increases and the compression ratio becomes low. Further, this sub-piston 9 is provided with a spring 10 for urging the sub-piston 9 in the backward direction.

Further, 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 surface on the back side with respect to the combustion chamber 5).
1 slidably penetrates the cover plate 8 and projects 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,
Hydraulic oil from a hydraulic source (not shown) is continuously supplied to the hydraulic type 12 through a port 14 with a check valve 13.

A portion 9a of the auxiliary piston 9 facing the combustion chamber 5 is configured to have a small diameter d, and a portion 9b facing the hydraulic chamber 12 is configured to have a large diameter D.

On the other hand, the stem 11 is provided with a passage 15 that communicates with the hydraulic chamber 12, and the protruding end of the stem 11 that protrudes into the upper chamber of the cylinder head is provided with a passage 15 that communicates with the hydraulic chamber 12. A spill port 16 is drilled for discharging into the chamber.

Further, reference numeral 17 indicates a spill ring which is one embodiment of the spill body, and the spill ring 17
is slidably fitted around the outer periphery of the protruding end of the stem 11, so that when the stem 11 moves backward, its spill port 16 is closed by the spill ring 17, and when the stem 11 moves forward, its spill port 16 is closed by the spill ring 17. While the port 16 is configured to open, the spill ring 17 is configured to be moved in the axial direction of the stem 11 by rotation of a lever 18 engaged therewith.

In this configuration, the spill ring 17 is
As shown by the two-dot chain line in the figure, if the forward movement operation is performed in the direction of the combustion chamber 5, that is, in the direction of closing the spill port 16, the flow of hydraulic oil from the spill port 16 will be stopped by closing the spill port 16. As the pressure in the hydraulic chamber 12, which is constantly supplied with hydraulic oil from the port 14 with the check valve 13, increases, the sub-piston 9 moves forward toward the combustion chamber, and this forward movement reaches the point where the spill port 16 opens. As you progress,
Hydraulic oil begins to flow out from the spill port 16, and when the amount of this outflow and the amount of supply to the hydraulic chamber 12 are balanced, the advance of the sub-piston 9 is stopped.

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 outflow amount increases, and the pressure in the hydraulic chamber 12 decreases. teeth,
The pressure in the combustion chamber 5 and/or the spring 10 causes the combustion chamber 5 to retreat away from the combustion chamber 5, and when this retreat progresses to the point where the spill port 16 is closed by the spill ring 17, the amount of flow out from the spill port 16 increases. When the flow rate 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 back and forth in a stepless manner. be able to.

Therefore, by rotating the lever 18 that engages with the spill ring 17 using an actuator 22 or the like connected to the other end, the compression ratio can be freely changed.

In addition, during the engine's explosion stroke, the secondary piston 9
When a large explosive force is applied to the secondary piston 9, this explosive force causes the secondary piston 9 to retreat slightly and close the spill port 16, while the pressure inside the hydraulic chamber 12 momentarily increases and the check valve 13 closes. Since the hydraulic fluid in the hydraulic chamber 12 is confined within the hydraulic chamber 12, it bears a large explosive force against the secondary piston, and in this case, the operation until the spill port 16 closes. The oil spill and the subsequent pressure increase of the hydraulic oil cause the combustion chamber 5
This absorbs and alleviates the impact on the auxiliary piston 9 due to the explosive combustion of the air-fuel mixture within the piston.

In this case, the part 9a of the sub-piston 9 facing the combustion chamber 5 has a small diameter of d, and the part 9b of the sub-piston 9 facing the hydraulic chamber 12 has a large diameter of D. The pressure P is the value obtained by multiplying the pressure p in the combustion chamber by the square of the diameter ratio of the small diameter part 9b and the large diameter part 9b in the sub-piston 9, that is, P=p(d/D) ² . be.

In this way, the pressure of the hydraulic oil in the hydraulic chamber 12 can be lowered, so that the hydraulic oil supplied to the hydraulic chamber 12 may be lubricating oil in the engine, hydraulic oil in the power steering mechanism of the automobile, or hydraulic oil in the automatic transmission mechanism of the automobile. Hydraulic oil in the Chick transmission can be used as is.

When lubricating oil is used in the engine, the lubricating oil from the lubricating oil pump is guided from the main gear rally, which distributes it to various rotating or sliding parts of the engine, to the port 14 with a check valve 13 to the hydraulic chamber 12. On the other hand, the spilled oil from the spill port 16 in the stem 11 is discharged into the upper chamber of the cylinder head, and generally speaking, it is discharged together with the lubricating oil for the valve mechanism (not shown) provided in the upper chamber of the cylinder head. This structure is simple because it can be returned to the oil pan (not shown) at the bottom of the cylinder block 1. Hydraulic chamber 12
When using the hydraulic oil in the power steering mechanism of an automobile or the hydraulic oil in the automatic transmission of an automobile as the hydraulic oil for the
As shown in the figure, a passage 23 branching from a hydraulic pump in a power steering mechanism or an automatic transmission is connected to port 1 to the hydraulic chamber 12.
A cover 24 is provided on the outside of the lid plate 8 to cover the spill ring 17 and the stem 11.
The hydraulic oil flowing out of the spill port 16 can be returned to an oil reservoir (not shown) in the power steering mechanism or automatic transmission via a passage 25 connected to the cover 24. Since the hydraulic oil in the power steering mechanism has a high pressure due to the characteristics of the hydraulic pump, the operational response of the sub-piston can be improved, and the sub-piston can be made smaller in diameter. In addition, the hydraulic fluid in an automatic transmission has a relatively high pressure as a characteristic of the hydraulic pump, and its viscosity changes little with respect to temperature changes, so even when the engine temperature is low, This has the advantage that the sub-piston can be operated with good responsiveness.

Furthermore, in the embodiment described above, 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 rod 17a is slidably operated. The opening/closing position of the port 16a may be configured to be displaced along the axial direction of the stem 11a, and as shown in FIGS. 6 and 7, the spill port in the stem 11b while forming an inclined spill port 16b inclined with respect to the axis of the
A gear-type spill ring 17b is rotatably and slidably fitted on the outer periphery of the stem 11b, and the spill ring 17b is pivotally supported to the cylinder head 2 by a bearing (not shown). This spill ring 17b is provided with one escape port 23 that matches the inclined spill port 16b when the stem 11b slides back and forth, and the stem 1 is provided in teeth on the outer periphery of this spill ring 17b.
The spill ring 17b is rotated by engaging the rack rod 26 disposed perpendicularly to the shaft 1b and reciprocating the rack rod 26 in the longitudinal direction by the actuator 22, thereby changing the inclined shape of the stem 11b. The escape port 23 is connected to the spill port 16b,
The opening/closing position of the spill port 16b may be displaced along the axial direction of the stem 11b by shifting the opening or closing position of the spill port 16b. It goes without saying that the mechanism for rotating the spill ring 17b is not limited to the rack and pinion shown in the embodiment drawings, but other means may be used. Nor). Furthermore, the positions of the inclined spill port 16b provided on the stem 11b and the relief port 23 provided on the spill ring 17b are reversed, that is, the relief port 23 is provided on the stem 11b, and the relief port 23 is provided on the stem 11b.
is used as a spill port, while spill ring 17b
By providing an inclined spill port 16b in the stem, the opening/closing position of the spill port may be displaced in the axial direction of the stem by rotation of the spill ring 17b. (In this case, the shape of the inclined spill port provided on the stem 11b or the spill ring 17b may be shaped as shown by the two-dot chain line in FIG. 6, if necessary.)

Furthermore, as shown in the figure, an annular groove 19 is carved on the outer peripheral surface of the large diameter portion 9b of the sub-piston 9, and the annular groove 19 is connected to the stems 11, 11a, 11.
It opens to the upper chamber of the cylinder head through a through hole 20 drilled in b, while the large diameter portion 9 of the sub piston 9
If an O-ring 21 is provided on the outer circumferential surface of b at a portion closer to the combustion chamber 5 than the annular groove 19,
The hydraulic oil leaking from the hydraulic chamber 12 to the combustion chamber 5 side is
Since the hydraulic oil flows out from the annular groove 19 into the upper chamber of the cylinder head, the amount of hydraulic oil in the hydraulic chamber 12 leaking into the combustion chamber 5 can be further reduced.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG. 1 is a longitudinal sectional front view of the main engine parts showing the first embodiment, FIG. 2 is a cross-sectional view taken from FIG. 1, and FIG. 4 is a longitudinal sectional front view of the main part of the engine showing the second embodiment, FIGS. 5 and 6 are views of another embodiment of the spill body and spill port, and FIG. 7 is the 6th embodiment. FIG. 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, 14...
...Hydraulic oil supply port, 11, 11a, 11b...
Stem, 16, 16a, 16b... Spill port, 17, 17b... Spill ring as an example of a spill body, 17a... Spill rod as an example of a spill body.

Claims (1)

[Scope of Claims] 1. A sub-cylinder opening into the combustion chamber is formed in the cylinder head, a sub-piston is slidably inserted into the sub-cylinder, and a hydraulic chamber is formed on the back surface of the sub-piston. , a port for supplying hydraulic oil is connected to the hydraulic chamber, a spring means is provided on the sub-piston for biasing the sub-piston in the backward direction, and a spring means is provided on the back surface of the sub-piston in the axial direction of the sub-cylinder. Extending stems are connected, the tip of the stem projects into the upper chamber of the cylinder head, the projecting end of the stem is provided with a spill port through which hydraulic oil in the hydraulic chamber flows out, and A spill body is attached to 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. A compression ratio variable device for an internal combustion engine, characterized in that the auxiliary piston is provided relatively movably so as to be able to be displaced in the direction, and further, the sub piston has a small diameter in a portion corresponding to the combustion chamber and a large diameter in a portion corresponding to the hydraulic chamber. . 2. The variable compression ratio device for an internal combustion engine according to claim 1, wherein lubricating oil for the internal combustion engine is used as the hydraulic oil supplied to the hydraulic chamber. 3. The variable compression ratio device for an internal combustion engine according to claim 1, wherein hydraulic oil in a power steering mechanism of an automobile is used as the hydraulic oil supplied to the hydraulic chamber. 4. The variable compression ratio device for an internal combustion engine as set forth in claim 1, wherein hydraulic oil in an automatic transmission mechanism of an automobile is used as the hydraulic oil supplied to the hydraulic chamber.