JPS6390632A - Compression ratio variable type internal combustion engine - Google Patents

Abstract

PURPOSE:To make the responsiveness of control over a subpiston securable so favor ably, by installing a hydraulic control valve, regulating a hydraulic fluid supply at both low and high load areas of an engine, in a hydraulic fluid supply passage to be interconnected to a hydraulic chamber at the back of the subpiston installed in a subcylinder to be interconnected to a combustion chamber. CONSTITUTION:A subpiston 9, advancing or retreating by feed or discharge control over a hydraulic fluid to a hydraulic chamber 10 and controlling volume of a combus tion chamber 5, namely, a compression ratio, is fitly installed in the subcylinder 7 made to open to the combustion chamber 5 and formed in a cylinder head 2. A control valve (check valve) 12, to be closed when a pressure rise occurs in the hydraulic cham ber 10, is installed in a supply passage feeding the hydraulic fluid to the hydraulic chamber 10. And, a spill body 18, opening or closing the spill port 17 formed in a hollow system 13, is externally fitted in this hollow system 13 unitized with the subpiston so as to control an outflow of the hydraulic fluid, freely slidably. And, in this constitution, furthermore a hydraulic control valve 24, regulating the hydraulic fluid supply at both low and high load speed areas of an engine, is installed in a part at the upstream side of the control valve 12 of the supply passage 11.

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 during operation.

[Conventional technology]

The applicant has filed an earlier patent application (Japanese Patent Application No. 57-48295).
In Japanese Unexamined Patent Publication No. 165541/1983, 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, and an engine is connected to the hydraulic chamber. A hydraulic oil supply passage from a hydraulic pump such as a lubricating oil pump driven by A hollow stem is provided in the axial direction of the sub-piston so as to protrude from the piston to the outside of the sub-cylinder, and a spill port is bored at the protruding end of the stem to allow the hydraulic oil in the hydraulic chamber to flow out. At the protruding end of the

A spill body having an opening/closing end surface that closes the spill port when the stem moves backward and opens the spill port when the stem moves forward is provided so as to be movable relative to the stem, and the spill body includes: A variable compression ratio internal combustion engine has been proposed which is provided with means for moving the spill body backward in response to an increase in the load on the engine.

In this variable compression ratio internal combustion engine, when the spill body moves forward as the load on the engine decreases, the spill port is fully closed, the pressure in the hydraulic chamber increases, and the auxiliary piston spills due to the pressure in the hydraulic chamber. The compression ratio increases by moving forward toward the combustion chamber until the port is approximately half open relative to the spill body, and when the spill body moves backward as the engine load increases, the spill port becomes fully open. The pressure in the hydraulic chamber decreases, and the pressure in the combustion chamber causes the auxiliary piston to move back away from the combustion chamber until the spill port is approximately half open relative to the spill body, thereby lowering the compression ratio. can do.

In addition, in this variable compression ratio internal combustion engine, the auxiliary piston moves back and forth following the back and forth movement of the spill body, and the amount of hydraulic oil supplied to the hydraulic chamber and the amount of hydraulic oil flowing out from the spill port are balanced. Movement stops at this position, and hydraulic oil is supplied to the hydraulic chamber when no pressure rise occurs in the hydraulic chamber, while when no pressure rise occurs in the hydraulic chamber, the engine's intake stroke Therefore, the sub-piston tends to temporarily move forward toward the combustion chamber during this period.

[Problem that the invention seeks to solve]

However, the pressure in the combustion chamber during the intake stroke increases as the engine load becomes lower, while the pressure and amount of hydraulic oil in a hydraulic pump such as a lubricating oil pump driven by the engine increases. , increases in proportion to the engine rotation speed, and therefore, the supply amount and pressure of hydraulic oil to the hydraulic chamber also increase in proportion to the engine rotation speed. The tendency for the engine to move forward toward the combustion chamber during this period increases in the engine's low-load, high-speed range, resulting in loss of control and a significant delay in the response of the sub-piston to the load. There was a problem.

Therefore, it is an object of the present invention to solve the above-mentioned problems in the variable compression ratio internal combustion engine of the prior application.

Means for Solving Problem C] In order to achieve this object, the present invention includes a method in which a sub-piston is slidably inserted into a sub-cylinder communicating with a combustion chamber, and a hydraulic chamber is formed on the back surface of the sub-piston. a hydraulic oil supply passage from a hydraulic pump driven by an engine is connected to the hydraulic chamber, and a control valve is provided in the hydraulic oil supply passage, the control valve being closed when a pressure rise occurs in the hydraulic chamber; A hollow 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 for allowing the hydraulic oil in the hydraulic chamber to flow out; A spill body having an opening/closing end surface that closes the spill port when the stem moves backward and opens the spill port when the stem moves forward is fitted onto the protruding end of the stem so that it can move freely relative to the stem. and provide
In a variable compression ratio internal combustion engine, the spill body is provided with a means for moving the spill body backward in accordance with an increase in the load on the engine, in which a variable compression ratio internal combustion engine is provided in the hydraulic oil supply passage, which The upstream part is equipped with a hydraulic control valve that regulates the hydraulic fluid supplied to the hydraulic chamber in the engine's low-load, high-speed range in relation to the engine's load and rotational speed. be.

[For production]

With this configuration, the supply of hydraulic oil to the hydraulic chamber on the back of the auxiliary piston can be regulated to a small amount in the low-load and high-load regions of the engine, so that the pressure in the combustion chamber during the intake stroke This makes it possible to reliably reduce the tendency of the auxiliary piston to move forward toward the combustion chamber even if the vacuum side increases during loading.

Moreover, the hydraulic fluid supplied to the hydraulic chamber is regulated only in the low load/high rotation range of the engine, and the hydraulic fluid supplied to the hydraulic chamber is not regulated in operating ranges other than the low load/high rotation range. Therefore, the responsiveness of the auxiliary piston in operating ranges other than the low load/high rotation range is not impaired.

〔Effect of the invention〕

Therefore, according to the present invention, it is possible to prevent the auxiliary piston for changing the compression ratio from becoming uncontrollable or having a significant delay in its response in the low-load, high-speed range of the engine. This has the effect of reliably controlling the back-and-forth movement of the auxiliary piston and, by extension, the compression ratio in accordance with the load of the engine.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, reference numeral 1 is a cylinder block, 2 is a cylinder head,
Reference numeral 3 indicates a piston that slides back and forth within the cylinder bore 4, and 5 indicates a combustion chamber formed by recessing the lower surface of the rod 2 into the cylinder. The ignition plug 6 is visible, and an intake port and an exhaust port (not shown) are open.

Reference numeral 7 denotes a sub-cylinder bored in the cylinder head 2. The sub-cylinder 7 opens at its lower side into the combustion chamber 5 and at its upper side into the cylinder head upper chamber on the upper surface of the cylinder head 2. A cover plate 8 is provided at the opening to the upper chamber of the cylinder head to close the opening. Further, reference numeral 9 denotes a sub-piston that is slidably inserted into the sub-cylinder 7, and a piston ring 9 is attached to the outer periphery of the sub-piston 9.
When the sub-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 sub-piston 9 retreats away from the combustion chamber 5, the As the volume increases, the compression ratio decreases, and the sub-piston 9 is provided with a spring 21 for biasing it in the backward direction.

A hydraulic chamber 10 is formed between the back surface of the sub-piston 9 and the cover plate 8, and a hydraulic oil supply passage 11 is provided to supply hydraulic oil from a hydraulic pump 28 such as a lubricating oil pump driven by an engine to the hydraulic chamber 10. When the pressure in the combustion chamber 5 is high, in other words, during the compression stroke and the explosion stroke, there is a passage in the hydraulic oil supply passage 11 that closes the hydraulic oil supply passage 11 during the compression stroke and the explosion stroke. A check valve 12, which is an example of a control valve according to the present invention, is provided. (You can also use a rotary type that closes.)

Further, a stem 13 extending parallel to the axis of the sub-cylinder 7 is connected to the back surface of the sub-piston 9, and the stem 13 extends slidably through the cover plate 8 and projects out of the sub-cylinder 7. , this stem 13 is hollow and has a passage 14 extending in the axial direction therein, and one end of the passage 14 communicates with the hydraulic chamber 10 via a chamber 15 and a hole 16 in the sub-piston 9, A spill port 17 for discharging the hydraulic oil in the hydraulic chamber 10 to the upper chamber of the cylinder head is provided at the end of the stem 13 that projects out of the sub-cylinder 7.

A ring-shaped spill body 18 is slidably fitted onto the end of the stem 13 that protrudes outward from the sub-cylinder 7.
When the person leaves work, the spill port 17 becomes the spill body 18.
Closed by an opening/closing end surface 19 on the lower surface of the stem 1
3 moves forward, the spill port 17 opens from the opening/closing end surface 19 of the spill body 18.

Further, a lever 20 is provided on the upper surface of the cylinder head 2, with the middle part of the lever 20 rotatably supported by a shaft 20a, and one end of the lever 20 is engaged with the spill body 18. On the other hand, the other end is connected to an actuator 22 so that the actuator 22 moves the spill body 18 in the axial direction of the stem 13 υj.

The hydraulic oil supply passage II includes the check valve 12.
An electromagnetic hydraulic control valve 24 is provided at an upstream side of the hydraulic pump to release a part of the hydraulic oil from the hydraulic pump to a return passage 23 to a hydraulic oil reservoir 29 such as an oil pan in the engine. .

Further, reference numeral 25 denotes a load sensor 26 that detects the engine load based on the intake pressure in the intake manifold of the engine.
and the actuator 2 for moving the spill body 18 in response to a signal from a rotation sensor 27 that detects the rotation speed of the engine.
2, and a control circuit that operates an electromagnetic hydraulic control valve 24, and the control circuit 25 moves the spill body 18 from the state indicated by the two-dot chain line in the figure in proportion to the increase in the load on the engine. The electromagnetic hydraulic control valve 24 moves to the state shown by the solid line, and from the state shown by the solid line to the state shown by the two-dot chain line in proportion to the decrease in the engine load, while the electromagnetic hydraulic control valve 24 moves to the state shown by the two-dot chain line in proportion to the decrease in the engine load. , so that a part of the hydraulic oil from the hydraulic pump is released into the return passage 23.

In this configuration, the check valve 12 in the hydraulic oil supply passage 11
is opened by the pressure measured by the hydraulic pump when the pressure in the hydraulic chamber 10 and therefore the pressure in the combustion chamber 5 is low.
Hydraulic oil is supplied to 0.

At this time, when the spill body 18 is moved in the forward direction from the position shown by the solid line in FIG. When the pressure in the combustion chamber 5 is low, such as during the exhaust stroke, the force that pushes the auxiliary piston 9 toward the combustion chamber 5 due to the pressure in the hydraulic chamber 10 to which hydraulic oil is supplied is generated by the combustion pressure in the combustion chamber and the spring 21. Since the force is stronger than the force pushing the secondary piston 9 in the direction of retreating from the combustion chamber 5, the secondary piston 9 moves forward toward the combustion chamber 5 against the spring 21 and closes the spill port 17 from the opening/closing end surface 19 of the spill body 18. When the hydraulic fluid in the hydraulic chamber 10 advances to the open position, the hydraulic fluid in the hydraulic chamber 10 starts to flow out from the spill port 17, and when the amount of this flow out and the amount supplied to the hydraulic chamber 10 are balanced, that is, the hydraulic fluid in the hydraulic chamber 10 causes the sub-piston to open. When the force pushing the sub piston 9 toward the combustion chamber, the combustion pressure within the combustion chamber 5, and the force of the spring 21 balance the force pushing the sub piston 9 in the direction of retreating from the combustion chamber 5, the sub piston 9 stops moving forward. .

Furthermore, when the spill body 18 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 17 is fully opened, the amount of flow from the spill port 17 increases, and the pressure in the hydraulic chamber 10 decreases. Therefore, the sub piston 9 is located in the combustion chamber 5.
When the spill port 17 retreats away from the combustion chamber 5 due to the combustion pressure and the force of the spring 21, and the spill port 17 retreats to the position where it closes at the opening/closing end surface 19 of the spill body 18, when the outflow amount is balanced with the supply amount, The backward movement of the auxiliary piston 9 is stopped, and by adjusting the movement of the spill body 18, the position of the auxiliary piston 9 can be arbitrarily changed, and thus the compression ratio can be arbitrarily changed during engine operation.

Therefore, the spill body 18 changes from the state shown by the two-dot chain line to the state shown by the solid line in proportion to the increase in the load on the engine, and from the state shown by the solid line to the state shown by the two-dot chain line in proportion to the decrease in the engine load. By shifting the compression ratio to , it is possible to automatically control the compression ratio so that it is high in the low load range of the engine and gradually decreases as the load increases.

When the engine is in a low load/high rotation range, the electromagnetic hydraulic control valve 24 is switched to release some of the hydraulic oil from the hydraulic pump to the return passage 23, and the hydraulic chamber 1
Since the supply of hydraulic oil can be regulated to a small amount with respect to This can reduce the tendency for the vehicle to move forward.

Note that when the load is rapidly increased from the low load/high speed state, that is, when starting suddenly, etc., the electromagnetic hydraulic control valve 24 does not immediately return the control valve 24 and the electromagnetic hydraulic control valve 24 performs regulation. By maintaining this state only for a certain period of time, it is possible to prevent a delay in the retraction of the sub-piston 9 following a rapid increase in load.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional front view of the main parts of the engine, and FIG. 2 is a sectional view taken along line n-1r in FIG. 1. 1...Cylinder block, 2...Cylinder head, 5...Combustion chamber, 7...Sub-cylinder, 9...
... Sub-piston, 10... Hydraulic chamber, 11... Hydraulic oil supply passage, 12... Check valve, 13... Stem, 17... Spill port, 18... ... Spill body, 19... Opening/closing end face, 21... Spring, 20...
... Lever, 22 ... Actuator for spill body movement, 23 ... Return passage, 24 ... Hydraulic pressure control valve, 25 ... Control circuit, 26 ... Load sensor, 27 ...Rotation sensor, 28...Hydraulic pump.

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 of the sub-piston, and hydraulic oil from a hydraulic pump driven by the engine is supplied to the hydraulic chamber. A supply passage is connected to the hydraulic oil supply passage, and a control valve is provided in the hydraulic oil supply passage, and the control valve is closed when pressure rises in the hydraulic chamber, and a hollow stem is provided so as to protrude from the auxiliary piston to the outside of the auxiliary cylinder. A spill port is provided in the axial direction of the piston, and a spill port is bored at the protruding end of the stem to allow the hydraulic oil in the hydraulic chamber to flow out. A spill body having an opening/closing end face such that the spill port is opened by the forward movement of the stem is fitted to the stem so as to be movable relative to the stem. In a variable compression ratio internal combustion engine, which is provided with means for moving backward according to the increase in compression ratio,
In the hydraulic oil supply passage, in a region upstream of the control valve, hydraulic oil to be supplied to the hydraulic chamber is regulated in a low load/high rotation range of the engine in relation to the load and rotation speed of the engine. A variable compression ratio internal combustion engine characterized by being equipped with a hydraulic control valve.