JPH0116977B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a variable compression ratio system that automatically changes and controls the compression ratio in an internal combustion engine with good responsiveness depending on the operating condition of the internal combustion engine. This relates to an internal combustion engine of the type.

[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. is moved back and forth by a negative pressure operated actuator related to intake negative pressure in the internal combustion engine, thereby displacing the opening/closing position of the spill port in the axial direction of the stem and moving the sub piston back and forth. Although it has the advantage of being able to change the compression ratio steplessly, 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 this case, 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 control rods are moved back and forth by the intake negative pressure of the internal combustion engine. Therefore, the negative pressure actuator for this purpose becomes large.

Moreover, 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 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 the maintenance and maintenance required to maintain good sliding conditions between the hollow stem and control rod
Inspection was difficult.

Furthermore, 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 reaches a certain level, it moves forward due to the pressure in the hydraulic chamber, and when it reaches a high level during the explosion stroke, it retreats to its original position.This is because the reciprocating movement is repeated once in one cycle.
The sliding parts between the auxiliary piston and the auxiliary cylinder, and the sliding parts between the stem and the control rod suffer from 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; When the auxiliary piston moves backward to follow the increase in the load of the internal combustion engine by moving forward as described above in the intake stroke, the backward movement of the auxiliary piston to follow the increase in load causes the intake This results in a delay corresponding to the forward movement during the process.In other words, knocking occurs because the responsiveness to a low compression ratio in response to an increase in load is low.

On the other hand, knocking in an internal combustion engine is affected by the atmospheric pressure, and the higher the atmospheric pressure, the more likely it is to occur.However, in the prior art, the compression ratio is only related to the load on the internal combustion engine. If the compression ratio value is automatically controlled according to the load and set according to the atmospheric pressure at a low altitude, the compression ratio will reach the limit for knocking when operating at a high altitude and low atmospheric pressure. There was too much leeway and it was not possible to produce sufficient output, and if the settings were set to match the atmospheric pressure at a location high above sea level, knocking could occur when driving at a location low at sea level and high atmospheric pressure. .

An object of the present invention is to provide a variable compression ratio device 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 equipped with a hydraulic oil supply port is formed on the back surface of the sub-piston, and a spring means is provided on the sub-piston for biasing the sub-piston in a backward direction. stems extending in the direction are connected, the tips of the stems protrude into the upper chamber of the cylinder head, and the protruding ends of the stems are provided with spill ports through which hydraulic oil in the hydraulic chamber flows out; Further, on the outer periphery of the protruding end of the stem, a spill body is provided so that the spill port is closed by the backward movement of the stem and opened by the forward movement of the stem, so that the spill port is opened by the spill body. The spill body is fitted in a relatively slidable manner so that the opening/closing position can be displaced in the axial direction of the stem, and the spill body is provided with a pressure chamber on which the intake negative pressure of the internal combustion engine acts. A negative pressure operated actuator drive device is connected to the negative pressure operated actuator drive device, which moves the spill body forward when the pressure increases toward the vacuum side, and moves the spill body backward when the intake negative pressure decreases, and the negative pressure operated actuator has the following features: The structure is such that an atmospheric pressure correction means is provided which introduces atmospheric air into the pressure chamber of the negative pressure actuator when the atmospheric pressure becomes high.

[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.

Therefore, a negative pressure operated actuator is connected to this spill body, which moves the spill body forward when the intake negative pressure in the internal combustion engine increases toward the vacuum side, and moves the spill body backward when the intake negative pressure decreases. Therefore, the compression ratio can be automatically and steplessly changed and controlled 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 slidable relative to the outer periphery of the stem, the back-and-forth sliding of this spill body can be achieved by moving the spill body in the hydraulic chamber as in the prior art. Since the oil pressure of the hydraulic oil does not act to prevent the sliding of the spill body and the spill body can be slid with a light force, the spill body can be slid back and forth by the intake negative pressure. By reducing the diameter of the negative pressure operated actuator, it is possible to reduce the size and weight of the actuator, and improve the responsiveness when automatically controlling the compression ratio according to changes in the load of the internal combustion engine. can be improved.

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. Furthermore, maintenance and inspection to maintain a good sliding condition between the stem and the spill body can be carried out 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 part between the sub-piston and the sub-cylinder and the stem and spill body can be reduced. This reduces wear on the sliding parts of the piston and improves its durability.In addition, 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 when moving the auxiliary piston backward in response to an increase in load, and as a result, 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 prevented.

Further, by providing the negative pressure actuator with a pressure correction means that introduces atmospheric air into the pressure chamber of the negative pressure actuator when the atmospheric pressure increases, the compression ratio according to the load can be adjusted. During the automatic control, when the atmospheric pressure increases, the intake negative pressure with respect to the pressure chamber in the negative pressure actuator becomes smaller due to the introduction of atmospheric air,
Since the spill body can be moved back by this amount, it is possible to automatically correct the compression ratio to lower it.
As a result, it is possible to prevent knotting when the atmospheric pressure is high or the compression ratio to have too much margin for knotting when the atmospheric pressure is low. Even in this case, it is possible to always maintain the optimum compression ratio and obtain high output.

In particular, during the automatic control of the compression ratio related to the load, the compression ratio is corrected according to the atmospheric pressure by controlling the introduction of atmospheric air into the negative pressure actuator. Compared to the correction control performed by increasing or decreasing the amount of hydraulic fluid in the hydraulic chamber on the back surface of the sub-piston, the correction control can be performed with a simpler structure, and can be controlled finely and with high precision. It has the advantage of good stability of correction control.

〔Example〕

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, reference numeral 3 indicates a main piston that reciprocates within the cylinder bore 4 of the cylinder block 1, and reference numeral 5 indicates the cylinder head. Each shows a combustion chamber formed by recessing the lower surface of the cylinder head 2, and the combustion chamber 5 includes an ignition plug 6 at approximately the center thereof.
An intake port and an exhaust port (not shown) are open.

Reference numeral 7 denotes an auxiliary cylinder bored in the cylinder head 2, and the auxiliary cylinder 2 has a lower side facing the combustion chamber 5.
The upper sides thereof each open into the upper chamber of the cylinder head 2, and the opening of the sub-cylinder 7 to the upper chamber of the 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, and a piston ring 9' is provided on the outer periphery of the sub-piston 9.
When the auxiliary piston 9 moves forward in the direction of the combustion chamber 5, the volume of the combustion chamber 5 decreases and the compression ratio becomes high, and when the auxiliary piston 9 retreats in the direction away from the combustion chamber 5, the volume of the combustion chamber 5 increases and the compression ratio becomes low. It is becoming more and more
Moreover, this sub-piston 9 is urged in the backward direction by a spring 10, and on the back surface of the sub-piston 9 (the surface on the back side with respect to the combustion chamber 5), there is an axis extending from the center of the sub-piston 9 to the axis of the sub-cylinder 7. A stem 11 extending in the direction is connected, and the stem 11 slidably penetrates the cover plate 8 and protrudes into the upper chamber of the cylinder head. A chamber 12 is formed, and hydraulic oil from a hydraulic source is supplied to the hydraulic chamber 12 via a port 14 with a check valve 3.

Further, the stem 11 is provided with a passage 15 that communicates with the hydraulic chamber 12, and a portion of the stem 11 that protrudes into the upper chamber of the cylinder head is provided with a passage 15 for communicating the hydraulic oil in the hydraulic chamber 12 to the upper chamber of the cylinder head. A spill port 16 for outflow is bored.

Reference numeral 17 indicates a spill ring which is one embodiment of the spill body, and the spill ring 17
When the spill ring 17 is slidably fitted onto the stem 11 and moved forward in the direction of the combustion chamber 5, the spill port 16 is closed by the spill ring 17, and the spill ring 17 is inserted into the combustion chamber 5. The spill port 16 is configured to open when the vehicle moves backward in a direction away from the vehicle.

Further, reference numeral 18 denotes a lever which is provided in the upper chamber of the cylinder head with its midway portion pivotally connected to the shaft 19 so as to be able to freely swing.One end of the lever 18 is engaged with the spill ring 17, while the other end is The diaphragm mechanism 20 is an example of a negative pressure actuator.
Contact.

This diaphragm mechanism 20 includes the lever 18
A diaphragm 22 is built in and connected to the other end via a rod 21, 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 17 Spring 2 that biases in the direction of sliding backwards
4, the pressure chamber 23 is connected to the engine's intake manifold (not shown) via the negative pressure transmission passage 25, and the intake negative pressure is introduced into the pressure chamber 23, thereby reducing the engine load. When the intake negative pressure increases toward vacuum as the engine load decreases, the spill ring 17 slides forward in proportion to this, and when the intake negative pressure becomes smaller than atmospheric pressure as the engine load increases, the spill ring 17 moves forward. 17 is configured to slide backward.

Reference numeral 26 indicates an atmospheric pressure correction means, and one embodiment of the atmospheric pressure correction means 26 includes an atmospheric air introduction passage 27 connected to the negative pressure transmission passage 25;
Atmospheric pressure correction valve 2 provided in the atmospheric air introduction passage 27
8, the valve body 29 of the atmospheric pressure correction valve 28 is connected to a bellows-type pressure sensitive system 30 whose length (l) changes according to the atmospheric pressure, and the atmospheric air introduction passage 27 is The area of the passage increases as the atmospheric pressure increases, and decreases as the atmospheric pressure decreases.

In this configuration, the spill ring 17 is
When moving in the forward direction from the position shown by the solid line in the figure to the position shown by the two-dot chain line, the spill port 16 is closed and the flow of hydraulic oil from the spill port 16 is stopped, and from the port 14 with the check valve 13. Since the pressure in the hydraulic chamber 12 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 16 is opened, hydraulic oil starts to flow out from the spill port 16, and when the amount of this flow out and the amount of supply to the hydraulic chamber 12 are balanced, the advance of the sub piston 9 stops. do. 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 increases, and the pressure in the hydraulic chamber 12 decreases. , the secondary piston 9 is connected to the pressure in the combustion chamber 5 and the spring 1
0, and when this retreat progresses to the point where the spill port 16 is closed by the spill ring 17, the spill port 16
When the outflow amount decreases and the outflow amount is balanced with the supply amount, the backward movement of the sub-piston 9 is stopped, and the sub-piston 9 is moved back and forth by the sliding movement of the spill ring 17. can do.

In this case, by relating the spill ring 17 to the diaphragm mechanism 20, which is an example of a negative pressure actuator, via the lever 18, when the intake negative pressure gradually increases toward vacuum as the engine load decreases, Since the spill ring 17 moves forward, the compression ratio gradually increases as the engine load decreases, and when the intake negative pressure becomes lower than atmospheric pressure as the engine load increases, the spill ring 17 moves back. Therefore, the compression ratio can be automatically and steplessly controlled in accordance with the engine load, such that the compression ratio gradually decreases as the engine load increases.

When the atmospheric pressure increases during the automatic control, the valve body 29 of the atmospheric pressure correction valve 28 opens and the amount of atmospheric air introduced into the negative pressure transmission passage 25 increases, thereby increasing the negative pressure acting on the pressure chamber 23. As the air pressure becomes smaller than the air pressure, the spill ring 17 is corrected and moved in the backward direction by the spring 24 from its position before the air pressure became high, so the compression ratio with respect to the intake negative pressure is corrected to be lower. This is because
Furthermore, when the atmospheric pressure decreases, the valve element 29 of the atmospheric pressure correction valve 28 closes, reducing the amount of atmospheric air introduced into the negative pressure transmission passage 25, and as a result, the negative pressure acting on the pressure chamber 23 becomes greater than vacuum. As a result, the spill ring 17 is corrected and moved in the forward direction from its position before the atmospheric pressure became low, so that the compression ratio with respect to the intake negative pressure is corrected to become higher.

In addition, during the engine's explosion stroke, the secondary piston 9
When the piston receives a large explosive force, 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 9, and in this case, until the spill port 16 closes. The outflow of the hydraulic oil during this period and the subsequent increase in the pressure of the hydraulic oil act as a cushion, which absorbs and alleviates the impact on the auxiliary piston 9 caused by the explosive combustion of the air-fuel mixture within the combustion chamber 5.

In the above embodiment, the hydraulic oil supplied to the hydraulic chamber 12 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 the spill body, but as shown in FIGS. 3 and 4, the spill port in the stem 11a is
Inclined spill port 1 inclined with respect to the axis of a
6a, and on the outer periphery of the stem 11a,
A gear-type spill ring 17a is rotatably and slidably fitted, and the spill ring 17a is pivotally supported on the cylinder head 2 by a bearing (not shown), and the stem 11a is slidable back and forth on this spill ring 17a. At this time, one relief port 34 is bored to match the inclined spill port 16a, and a rack rod 36 disposed perpendicular to the stem 11a is engaged with the gear 35 on the outer periphery of the spill ring 17a. Then, the rack rod 36 is reciprocated in the longitudinal direction by the diaphragm mechanism 20 related to the intake negative pressure of the engine to rotate the spill ring 17a, thereby opening the inclined spill port 16a of the stem 11a.
The relief port 34 is placed in the () position or ().
The compression ratio may be automatically controlled by moving the stem 11a to the desired position (in this case, the stem 11a is held slidably but not rotatably, and the spill ring 17a here is rotated). The mechanism is not limited to the rack and pinion of the embodiment, but other means may also be used). 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, and the shapes of the ports provided on the stem and spill ring may be changed depending on the requirements. Depending on this, a combination of arbitrary shapes as shown by the two-dot chain line in FIG. 3 can be considered.

[Brief explanation of drawings]

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 cross-sectional view taken from the side in FIG. 1, and FIG. Another example of the port, FIG. 4 is a plan view of FIG. 3. 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 7... Sub cylinder, 9... Sub piston, 11, 11a... Stem, 12... Hydraulic chamber, 16, 16a... Spill port ,17,1
7a... Spill body, 20... Diaphragm mechanism,
26...Atmospheric pressure correction means.

Claims (1)

[Claims] 1. A 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 chamber equipped with a hydraulic oil supply port is formed on the back surface of the auxiliary piston, The sub-piston is provided with spring means for biasing the sub-piston in the backward direction, and a stem extending in the axial direction of the sub-cylinder is connected to the sub-piston, and the tip of the stem is placed in the upper chamber of the cylinder head. A spill port is provided at the protruding end of the stem to allow the hydraulic fluid in the hydraulic chamber to flow out, and a spill port is provided on the outer periphery of the protruding end of the stem by the backward movement of the stem. A spill body in which the spill port is closed and the spill port is opened by the forward movement of the stem is fitted so as to be relatively slidable so that the opening/closing position of the spill port by the spill body can be displaced in the axial direction of the stem. On the other hand, in the spill body,
The engine is equipped with a pressure chamber on which the negative intake pressure of an internal combustion engine acts, and when the negative intake pressure acting on this pressure chamber increases toward the vacuum side, the spill body is moved forward, and when the intake negative pressure decreases, the spill body is moved backward. The negative pressure actuator is connected to the negative pressure actuator, and the negative pressure actuator is provided with an atmospheric pressure correction means that introduces atmospheric air into the pressure chamber of the negative pressure actuator when the atmospheric pressure increases. A variable compression ratio internal combustion engine featuring: