JPS6331655B2 - - 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 is changed and controlled in accordance with the engine load.

[Conventional technology]

In an internal combustion engine, increasing the compression ratio can improve output and reduce fuel consumption, but increasing the compression ratio causes knocking in high load ranges.

For this reason, the compression ratio in conventional internal combustion engines with a constant compression ratio must be set to a value that does not cause knocking in the high load range, making it impossible to produce sufficient output in the low load range and reducing fuel consumption sufficiently. Can not do it.

Therefore, Japanese Patent Application Laid-open No. 56-88926 as a prior art proposes setting the compression ratio high in a low load range and low in a high load range.

When changing the compression ratio by moving the sub-piston inserted into the sub-cylinder communicating with the combustion chamber back and forth, the tip of the rod protruding from the sub-piston to the outside of the sub-cylinder is
It contacts a plunger in a hydraulic cylinder installed on the same axis as this, and when the intake negative pressure in the engine is in a low load range greater than a certain value, hydraulic oil is sent to the hydraulic cylinder and the sub-piston is advanced to increase the compression ratio. When the intake negative pressure is lower than a certain value and is in a high load range, the hydraulic oil in the hydraulic cylinder is released and the auxiliary piston is retracted to lower the compression ratio.

[Problem that the invention seeks to solve]

However, the compression ratio changing control according to the prior art is an ON-OFF type control in which the compression ratio is suddenly changed from high to low or from low to high after a certain load value, so the compression ratio is not proportional to the load. It is not possible to smoothly change the compression ratio, and when the compression ratio is suddenly changed, engine torque fluctuations become large and drivability deteriorates.

Moreover, providing a hydraulic cylinder for variable compression ratio outside the sub-cylinder not only complicates the structure, but also in the case of a multi-cylinder internal combustion engine, it is necessary to install a hydraulic cylinder for variable compression ratio for each cylinder. As a result, the internal combustion engine becomes significantly larger and weighs more due to the increased installation space.

In addition to solving this problem, the present invention
The purpose is to reduce fuel consumption during deceleration of the internal combustion engine.

[Means for solving problems]

Therefore, in the present invention, a sub-piston is slidably inserted into a sub-cylinder communicating with a combustion chamber, a hydraulic chamber is formed on the back surface of the sub-piston in the sub-cylinder, and a hydraulic oil supply passage is provided in the hydraulic chamber. At the same time, a stem is provided in the axial direction of the sub-piston so as to protrude from the sub-piston to the outside of the sub-cylinder, and a spill port is provided at the protruding end of the stem so that the hydraulic oil in the hydraulic chamber flows out. A spill body is provided at the protruding end of the stem, and the spill port is closed by the backward movement of the stem, and the spill port is opened by the forward movement of the stem. The spill body is provided to be relatively movable so that its position can be displaced in the axial direction of the stem, and the spill body is configured to be movable in relation to the load of the engine so that the spill body is moved in accordance with the load of the engine, and the spill port is opened and closed by the spill body. This configuration includes means for displacing the position in the backward direction when the engine is decelerated.

[Action/effect of the invention]

In such a configuration, when the spill body is moved so as 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.

Therefore, by moving and operating this spill body in relation to the engine load, the compression ratio can be controlled to change steplessly in accordance with the engine load. .

As described above, according to the present invention, the compression ratio can be smoothly and steplessly controlled to change according to the engine load, thereby reliably reducing the deterioration of drivability due to the control to change the compression ratio. On the other hand, in the invention of the sub-piston, by moving the sub-piston back and forth when supplying and discharging hydraulic oil to the hydraulic chamber, it is necessary to provide a hydraulic cylinder for variable compression ratio outside the sub-piston as in the prior art. There is no
Not only can the structure be simplified, but the internal combustion engine can also be made smaller and lighter.

Further, the spill body retreats when the engine decelerates, and as the spill body retreats, the auxiliary piston follows and retreats, increasing the internal volume of the combustion chamber.

Increasing the internal volume of the combustion chamber when the engine decelerates can prevent the pressure within the combustion chamber from increasing significantly toward the vacuum side during the intake stroke. Since it is possible to prevent the intake amount of the air-fuel mixture from increasing due to a significant increase in the side, it is possible to reduce fuel consumption during deceleration, and the amount of fuel consumed by the engine can be reduced. Furthermore, in some cases, the fuel cut means provided in general internal combustion engines during deceleration can be omitted.

〔Example〕

Hereinafter, an embodiment of the present invention will be explained with reference to the drawings. In the drawing, 1 is a cylinder block, 2 is a cylinder head, 3 is a piston that reciprocates within the cylinder bore 4 of the cylinder block 1, and 5 is a concave part on the lower surface of the cylinder head 2. The combustion chambers 5 each have an ignition plug 6 screwed onto the cylinder head 2 extending 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 has its lower side open to the combustion chamber 5 and its upper side open to the upper surface of the cylinder head 2, and the sub-cylinder 7 is connected to the upper chamber of the cylinder head. A lid plate 8 is provided at the opening to close it.

Reference numeral 9 denotes a sub-piston that is slidably inserted into the sub-cylinder 7. A piston ring 9' is provided on the outer periphery of the sub-piston 9, and when the sub-piston 9 moves forward in the direction of the combustion chamber 5, combustion occurs. The internal volume of the combustion chamber 5 decreases and the compression ratio increases, and when the auxiliary piston 9 retreats in a direction away from the combustion chamber 5, the internal volume of the combustion chamber 5 increases and the compression ratio decreases. , this sub-piston 9 is urged in the backward direction by a spring 10, and the back surface of the sub-piston 9 (combustion chamber 5
A stem 11 extending in the axial direction from the center of the sub-piston 9 is connected to the rear surface), and the stem 11 is slidably penetrated through the cover plate 8 and protrudes outward. , a hydraulic chamber 12 is formed between the back surface of the sub-piston 9 and the cover plate 8;
Then, hydraulic oil from a hydraulic source (not shown) is supplied to the check valve 13.
The hydraulic oil is continuously supplied through the hydraulic oil supply passage 14.

Further, 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 one embodiment of the spill body. When the spill ring 17 moves forward in the direction, the spill port 16 is closed by the spill ring 17, and when the spill ring 17 moves backward in the direction away from the combustion chamber 5, the spill port 16 opens.

Further, reference numeral 18 denotes a lever provided in the upper chamber of the cylinder head with its midway portion pivotally attached to the shaft 19, and one end of the lever 18 is connected to the spill ring 17.
On the other hand, an actuator 21 operated by a control circuit 20 is connected to the other end of the lever 18, and a signal from an engine load detector 22 is inputted to the control circuit 20, thereby increasing the engine load. The actuator 21 is configured to move the spill ring 17 in the backward direction in proportion to.

Further, the control circuit 20 inputs a signal from an engine deceleration (engine brake) detection means 23, and when the engine is decelerating, the control circuit 20 causes the spill link 17 to be significantly retracted by an actuator 21, giving priority to control by the load. Equipped with means for moving. .

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. Since the pressure in the hydraulic chamber 12 to which is supplied increases, the auxiliary piston 9 advances toward the combustion chamber 5,
When this forward movement progresses to the point where the spill port 16 is opened, the hydraulic oil starts to flow out from the spill port 16, and when this outflow amount and the amount of hydraulic oil supplied to the hydraulic chamber 12 are balanced, the sub piston 9 is opened. Advancement stops.

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 hydraulic oil flowing out from the spill port 16 increases, and the pressure in the hydraulic chamber 12 increases. decreases, the secondary piston 9 retreats away from the combustion chamber 5 due to the pressure in the combustion chamber 5 and/or the spring 10, and this retreat causes the spill port 16
When the flow progresses to the point where it is closed by the spill ring 17, the amount of outflow from the spill port 16 decreases, and when the amount of outflow is balanced with the amount of supply to the hydraulic chamber 12, the backward movement of the sub piston 9 stops. By moving the spill ring 17, the position of the sub-piston 9 can be arbitrarily changed, and thus the compression ratio can be arbitrarily changed.

In this case, by relating the spill ring 17 to move backward as the engine load increases via the lever 18 and actuator 21 as well as the control circuit 20, the compression ratio increases as the engine load increases. Accordingly, it is possible to control the change automatically and smoothly in a stepless manner so that the value gradually decreases.

In addition to being related to the engine load, the spill ring 17 is also related to the engine rotation speed.
It is also possible to automatically control the compression ratio so that it gradually increases as the rotational speed increases.

When the engine is in operation and the throttle valve is suddenly closed to decelerate, the control circuit 20 gives priority to the signal from the load detector 22 and causes the actuator 21 to move the spill ring 17 largely backwards, thereby increasing the combustion chamber 5. Since the internal volume increases, it is possible to prevent the pressure within the combustion chamber 5 from increasing significantly toward the vacuum side when the engine is decelerated.

In this case, the engine feed reduction detection means 23 is as follows:
Although it may be based on changes in the intake pipe negative pressure after the throttle valve, the opening degree of the throttle valve and the rotational speed of the engine can be detected simultaneously, and when the throttle valve is closed and the rotational speed is the same as when the engine is idling. It may also be possible to determine that the engine is decelerating when the rotational speed is slightly higher than the engine speed.

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 sub-piston, and in this case, the operation until the spill port 16 closes. The outflow of oil and the subsequent rise in pressure of the hydraulic oil act as a cushion that 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 constantly 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 addition, although the above-mentioned embodiment shows the case where the spill ring 17 is used as an example of the spill body, as shown in FIG. A spill rod 17a of another embodiment is slidably inserted,
The spill rod 17a may be constructed so as to open and close the spill port 16a by sliding movement using an actuator related to the load of the engine. In this case, the opening/closing position of the spill port due to movement was performed by sliding the spill body in the axial direction with respect to the stem, but the displacement of the opening/closing position of the spill port due to relative movement of the spill body with respect to the stem Instead of sliding in the axial direction, rotation of the spill body can also be used as described below.

That is, FIGS. 4 and 5 show an embodiment in this case, and a spill ring 17b having a gear 25 on the outer periphery is used as another embodiment of the spill body,
This is rotatably and slidably fitted into the stem 11b, and the spill port in the stem 11b is formed into an inclined spill port 16b that is inclined with respect to the axis of the stem 11b, and the gear type spill ring 17b is The spill ring 17 is pivotally supported on the cylinder head 2 by a bearing (not shown).
One escape port 24 is bored in b to match the inclined spill port 16b when the stem 11b slides back and forth, and this spill ring 17a is attached to the gear 25 on the outer periphery in a direction perpendicular to the stem 11b. The provided rack rods 26 are engaged with each other, and the rack rods 26 are slid in the longitudinal direction by an actuator 21 related to the load of the engine to generate a spill ring 17b.
The spill ring 1
The opening/closing position of the spill port 16b by the spill port 7b is configured to be displaced along the axial direction of the stem 11b (in this case, the opening/closing position of the spill port 16b
The spill ring 17b is held slidably and non-rotatably, and the mechanism for rotating the spill ring 17b is not limited to the rack and pinion of the embodiment, but other means may also be used.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a longitudinal sectional front view of the main engine parts, FIG. 2 is a cross-sectional view taken from the side of FIG. 1, and FIGS. Another example, FIG. 5, is a plan view of FIG. 4. 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 6... Spark plug, 7... Sub cylinder, 9... Sub piston, 12... Hydraulic chamber, 1
1, 11a, 11b... Stem, 14... Hydraulic oil supply passage, 16, 16a, 16b... Spill port, 17, 17a, 17b... Spill body, 21...
... actuator, 20 ... control circuit, 22 ... load detector, 23 ... deceleration detection means.

Claims (1)

[Claims] 1. A sub-piston is slidably inserted into a sub-cylinder communicating with the combustion chamber, a hydraulic chamber is formed on the back surface of the sub-piston in the sub-cylinder, and a hydraulic oil supply passage is connected to the hydraulic chamber; A stem is provided in the axial direction of the sub-piston so as to protrude from the sub-piston to the outside of the sub-cylinder, and a spill port is provided at the protruding end of the stem to allow the hydraulic oil in the hydraulic chamber to flow out; 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. The spill body is provided so as to be relatively movable so as to be able to be displaced in the direction, and the spill body is arranged so as to be relatively movable in relation to the load of the engine so as to be moved in accordance with the load of the engine, and furthermore, the opening/closing position of the spill port by the spill body is controlled according to the load of the engine. A variable compression ratio internal combustion engine characterized by being provided with means for displacing in the backward direction during deceleration.