JPH0116968B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a variable compression ratio internal combustion engine in which the compression ratio of the internal combustion engine is automatically changed according to the operating conditions of the internal combustion engine. 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 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 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 to change the compression ratio according to the operating state of the internal combustion engine 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 equipped with an oil passage communicating with the atmosphere is slidably inserted into the hollow stem, and the control rod is
Since it is configured to slide in response to the load on the internal combustion engine via an actuator, the compression ratio in the internal combustion engine can be automatically and steplessly changed in response to changes in the load on the internal combustion engine. However, 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 the sliding operation of a control rod slidably inserted into the hollow stem. During the sliding operation of the control rod, the hydraulic pressure of the hydraulic oil in the hydraulic chamber acts to prevent the sliding operation of the control rod. In other words, a large force is required for the sliding operation of the control rod. Since it is not possible to slide the control rod with a light force, the control rod is
The actuator that slides in response to the load of the internal combustion engine becomes larger.

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. It is extremely difficult to process, and the cost required for this mechanical processing increases significantly.
Another problem was that it was difficult to perform maintenance and inspection to maintain a good sliding condition between the hollow stem and the control rod.

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 and 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 several times, the sliding parts between the sub-cylinder and the sub-piston and the sliding parts between the hollow stem and the control rod are subject to large wear, resulting in low durability.

Furthermore, 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, so the responsiveness when moving the secondary piston forward in accordance with the decrease in the load of the internal combustion engine is improved. 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, so it cannot follow the increase in load of the internal combustion engine. When the secondary piston moves backward by increasing the amount of hydraulic oil flowing out of the hydraulic chamber, the backward movement of the secondary piston to follow the increase in load will be delayed by the amount of forward movement during the intake stroke. In other words, the responsiveness to a low compression ratio in response to an increase in load decreases, and the compression ratio corresponding to the load tends to become higher than the appropriate value corresponding to the load, causing noise. In particular, the occurrence of knocking due to this delay in response increases as the rotational speed of the internal combustion engine increases.

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

[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 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 tip of the stem projects into the upper chamber of the cylinder head; A spill port is provided at the protruding end of the stem to allow the hydraulic oil in the hydraulic chamber to flow out, and a spill port is provided on the outer periphery of the protruding end of the stem so that the spill port closes when the stem moves backward. A spill body whose spill port is opened by the forward movement of the spill body is fitted so that the spill body can be relatively movably moved such 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 A spring means is connected to the internal combustion engine via an actuator so as to be moved and operated according to a load in the internal combustion engine, or a load and a rotational speed, and further includes a spring means on the secondary piston for biasing the secondary piston in a backward direction. The configuration was set up so that

[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, by connecting this spill body to the internal combustion engine via an actuator so as to move and operate it according to the load on the internal combustion engine, or the load and the rotation speed, the compression ratio can be adjusted according to the load on the internal combustion engine, or the load and the rotational speed. It can be automatically and steplessly changed according to changes in the rotational speed.

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, it is possible to avoid increasing the size of the actuator for moving the spill body back and forth in response to changes in engine load, etc. It is possible to achieve smaller size and lighter weight.

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.

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, the distance that the auxiliary piston moves forward during the intake stroke is reduced, reducing the amount of hydraulic oil that flows into the hydraulic chamber during this forward movement, and accelerating the backward movement of the auxiliary piston, thereby reducing internal combustion. When the secondary piston is moved backward by increasing the amount of hydraulic oil flowing out from the spill port in the hydraulic chamber in response to an increase in engine load or an increase in load and a decrease in rotational speed, the backward movement of the secondary piston is In other words, it is possible to improve the responsiveness of lowering the compression ratio in response to an increase in load, or an increase in load and a decrease in rotational speed, and to ensure that the compression ratio is appropriate for the load, etc. As a result, it is possible to reliably control the occurrence of knocking when the compression ratio is lowered in response to an increase in load, or an increase in load and a decrease in rotational speed.

〔Example〕

Embodiments of the present invention are shown below in the drawings (Figs. 1 and 2).
In the figure, numeral 1 is a cylinder block, numeral 2 is a cylinder head, numeral 3 is a piston that reciprocates within the cylinder bore 4 of the cylinder block 1, and numeral 5 is a piston that recesses the lower surface of the cylinder head 2. The combustion chambers 5 each have an ignition plug 6 screwed onto the cylinder head 2 located approximately at the center thereof, and an intake port and an exhaust port (not shown) are open therein.

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 chamber 12 via a port 14 with a check valve 13.

Furthermore, 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.

Reference numeral 17 indicates a spill ring which is an embodiment of the spill body, and the spill ring 17 is slidably fitted on the outer periphery of the protruding end of the stem 11 so that the stem 11 is retracted. When the stem 11 moves forward, the spill port 16 is closed by the spill ring 17, and when the stem 11 moves forward, the spill port 16 opens.

Further, reference numeral 18 indicates a lever whose midway portion is slidably pivoted on the upper surface of the cylinder head 2 by a shaft 19. One end of the lever 18 is engaged with the spill ring 17, while the other The end is connected to a diaphragm mechanism 20, which is one embodiment of an actuator.

This diaphragm mechanism 20 has the lever 28
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 17 A spring 24 is provided to bias the pressure chamber 23 in the backward direction, and the pressure chamber 23 is connected to the negative pressure transmission passage 25.
By connecting to an intake manifold (not shown) in an internal combustion engine through a When the pressure increases toward the atmospheric pressure side, the spill ring 17 moves forward in proportion to this, and as the load on the internal combustion engine increases, the intake negative pressure decreases toward the atmospheric pressure side.
The spill ring 17 is configured to move backward in proportion to this.

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.

By relating this spill ring 17 to the actuator 20 operated by the intake negative pressure via the lever 18, when the intake negative pressure increases toward the vacuum side as the load in the internal combustion engine decreases, the diaphragm mechanism 20 Since the spill ring 17 moves forward from the position indicated by the solid line to the position indicated by the two-dot chain line due to the intake negative pressure acting on the pressure chamber 23, the compression ratio automatically increases in accordance with the decrease in the load of the internal combustion engine. Additionally, when the intake negative pressure decreases toward atmospheric pressure as the load on the internal combustion engine increases, the pressure chamber 23
The spring 24 inside moves the spill ring 17 backward from the position indicated by the two-dot chain line to the position indicated by the solid line.
The compression ratio can be automatically changed and controlled in response to changes in the load on the internal combustion engine, such that the compression ratio automatically decreases as the load on the internal combustion engine increases.

The actuator for moving the spill ring 17 back and forth is not limited to the diaphragm type actuator of the above embodiment, but other types of actuators such as electric type or hydraulic type may of course be used. As shown in FIG. 3, a control circuit 27 for an actuator 26 for moving the spill ring.
The signals from the load detector 28 in the internal combustion engine and the rotation speed detector 29 in the internal combustion engine are input to the engine, and the spill ring 17 is moved forward as the load decreases and as the load increases. By configuring the engine to move backward as the rotation speed increases, and move backward as the rotation speed decreases, the intake negative pressure becomes a vacuum in the low load range. By increasing the compression ratio, it is possible to prevent a decrease in the actual compression ratio due to a larger side, and at the same time, in a high rotation range, a decrease in output due to a decrease in charging efficiency can be prevented.

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 sub-piston 9 due to the explosive combustion of the air-fuel mixture within the piston.

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. When used, the lubricating oil from the lubricating oil pump is guided from the main gear rally to the hydraulic chamber 12 to the port 14 with the check valve 13, which distributes the lubricating oil to various rotating or sliding parts in the engine, while the stem 11 The spilled oil from the spill port 16 in the cylinder head is discharged into the upper chamber of the cylinder head, and is generally combined with lubricating oil for the valve mechanism (not shown) provided in the upper chamber of the cylinder head, and is then pumped into the cylinder block. This structure is simple because it can be returned to the oil pan (not shown) in the lower part of No. 1. In addition, 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 fluid, as shown in Fig. The passage 30 is connected to the port 14 to the hydraulic chamber 12, and a cover 31 is provided on the outside of the cover plate 8 to cover the spill ring 17 and the stem 11, so that the hydraulic oil flowing out from the spill port 16 is directed to the cover 31. It may be returned to the oil sump (not shown) in the power steering mechanism or automatic transmission via the connected passageway 32.

Furthermore, in the embodiment, the spill body is a spill ring 17, and this spill ring 17 is attached to the stem 1.
Although the case of sliding movement in the axial direction of the first axis is shown, the fifth axis
As shown in FIG. 6, the spill port in the stem 11a is formed into an inclined spill port 16a that is inclined with respect to the axis of the stem 11a, and a gear-type spill ring 17a is formed on the outer periphery of the stem 11a. The 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). When this occurs, one escape port 23 is bored to match the inclined spill port 16a, and a lock rod 24 disposed perpendicularly to the stem 11a is engaged with the teeth on the outer periphery of the spill ring 17a. The rack rod 24 is actuated by an actuator 26 that is dependent on the engine load or load and speed.
By reciprocating in the longitudinal direction, the spill ring 17a is rotated to open the escape port 23 with respect to the inclined spill port 16a of the stem 11a.
, thereby shifting the opening/closing position of the spill port 16a to the position of the stem 11.
The stem 11a may be configured to be displaced along the axial direction of the cylinder head 2 (in this case, the stem 11a is held slidably but non-rotatably relative to the cylinder head 2, and the stem 11a is held non-rotatably with respect to the cylinder head 2, ring 1
It goes without saying that the mechanism for rotating 7a is not limited to the rack and pinion shown in the embodiment drawings, but other means may be used. Furthermore, this stem 11
The positions of the inclined spill port 16a provided in the stem 11a and the relief port 23 provided in the spill ring 17a are reversed.
A is provided with a relief port 23, and this relief port 23 is used as a spill port.By providing an inclined spill port 16a on the spill ring 17a, the opening/closing position of the spill port can be changed by rotation of the spill ring 17a. It may also be configured to be displaced in the axial direction.

Furthermore, the stem 11a or the spill ring 17a
If necessary, the shape of the inclined spill port provided in FIG.

[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 sectional view taken from the side of FIG. 1, and FIG. Example circuit diagram, FIG. 4 is a longitudinal sectional front view of the engine main part showing the third embodiment, FIG. 5 is another embodiment diagram of the spill body and spill port, and FIG. 6 is a plan view of FIG. 5. It is a diagram. 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 7... Sub cylinder, 9... Sub piston, 12... Hydraulic chamber, 14... Hydraulic oil supply port, 11, 11a... Stem , 16, 16a
... Spill port, 17, 17a... Spill ring as an embodiment of a spill body, 20... Diaphragm mechanism as an embodiment of an actuator, 26...
...actuator.

Claims (1)

[Claims] 1 A sub-cylinder that opens into the combustion chamber is formed 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 a hydraulic chamber is actuated into the hydraulic chamber. While connecting an oil supply port, 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, and the protruding end of the stem is connected to the sub-piston. is provided with a spill port through which the hydraulic oil in the hydraulic chamber flows out, and a spill port is provided on the outer periphery of the protruding end of the stem so that the spill port closes when the stem moves backward and moves forward when the stem moves forward. A spill body with which the spill port can be opened is fitted so that the spill body can move relatively freely 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 attached to the internal combustion engine. The sub-piston is connected via an actuator so as to be moved according to the load in the internal combustion engine or the load and rotational speed, and the sub-piston is further provided with a spring means for biasing the sub-piston in a backward direction. A variable compression ratio internal combustion engine featuring: