JPS6331658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a compression ratio variable device that can change the compression ratio of an internal combustion engine during operation.

[Conventional technology]

In an internal combustion engine, it is preferable to increase the compression ratio in order to improve output and reduce fuel consumption, but increasing the compression ratio causes knocking in the high load/low rotation range.

For this reason, Japanese Patent Application Laid-Open No. 1988-88926 as a prior art discloses that the compression ratio is made variable according to the rotational speed and load of the internal combustion engine, and that
Publication No. 79639 proposes making the compression ratio variable in response to knocking in the internal combustion engine.

In each of these prior art compression ratio variable devices, an auxiliary piston for varying the compression ratio is inserted into an auxiliary cylinder communicating with a fuel chamber, and the compression ratio is adjusted by moving the auxiliary piston back and forth with respect to the combustion chamber. In order to make the rotation speed of the internal combustion engine variable, the tip of the rod protruding from the sub-piston to the outside of the sub-cylinder is connected to a hydraulic cylinder provided on the same axis as the rod, so that the hydraulic cylinder controls the sub-piston at the rotational speed of the internal combustion engine. And it moves back and forth depending on the load or knocking.

[Problem that the invention seeks to solve]

However, providing a hydraulic cylinder for variable compression ratio outside the auxiliary cylinder not only complicates the structure, but also in the case of a multi-cylinder internal combustion engine, it is necessary to provide a hydraulic cylinder for variable compression ratio for each cylinder. As a result, the increased installation space significantly increases the size of the internal combustion engine, and the weight of the internal combustion engine also increases considerably.

The present invention aims to solve this problem.

[Means for solving problems]

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 the back surface of the sub-piston in the sub-cylinder is closed with a cover plate to form a hydraulic chamber. , a hydraulic oil supply passage is connected to the hydraulic chamber, and a stem is provided in the axial direction of the sub-piston so as to pass through the cover plate from the sub-piston and protrude outside the sub-cylinder, and a protruding end of the stem is provided with a stem. 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 the spill port is closed by the rear end movement of the stem, and the spill is prevented by the forward movement of the stem. A spill body with an opening port is provided so as to be relatively movable 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 stem is further arranged such that the stem is auxiliary with respect to the auxiliary piston. The pistons are connected so that they can shift in a direction perpendicular to the axis of the piston.

[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 to the hydraulic pressure. The hydraulic oil supplied into 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 is 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 secondary piston moves backward from the combustion chamber due to the pressure within the combustion chamber, and this backward movement occurs until the spill port reaches a position where the amount of hydraulic oil flowing out from the spill port is equal to the amount of hydraulic oil supplied to the hydraulic chamber. Since the piston stops when it is closed, the sub-piston can be moved forward or backward by moving the spill body.

In other words, the compression ratio can be freely and steplessly varied by the extremely simple operation of moving the spill body, while the back of the sub-piston is formed into a hydraulic chamber, and hydraulic oil is supplied and discharged to and from this hydraulic chamber. Since the compression ratio is made variable by moving the sub-piston back and forth, there is no need to provide a hydraulic cylinder outside the sub-cylinder, unlike the conventional variable compression ratio device mentioned above, which simplifies the structure. The space can be reduced, and the internal combustion engine can therefore be made smaller and lighter.

However, in the case of the above structure, the stem extending from the sub-piston moves back and forth together with the sub-piston while penetrating the cover plate, so it is necessary to drill a hole in the cover body so that the stem passes through it. If there is even a slight dimensional error in the axial direction between the center position of the hole and the center position of the stem, the sub-piston will not be able to move back and forth smoothly, so make sure that the sub-piston can move back and forth smoothly. In order to do this, the center position of the through hole must be precisely aligned with the center position of the stem, and this process requires an extremely high degree of precision.

In view of this, the present invention provides that when connecting a stem that protrudes through the lid plate forming the hydraulic chamber to the sub-piston, the stem is aligned with the axis of the sub-piston relative to the sub-piston. The structure is such that they are connected so that they can shift in the right angle direction, and with this structure, even if there is a shift between the center position of the through hole in the lid plate and the center position of the stem, this shift can be prevented. Since this can be absorbed by the displacement movement of the stem relative to the sub-piston, the back-and-forth movement of the sub-piston and stem can be extremely smooth, and processing accuracy can be significantly relaxed, leading to a reduction in manufacturing costs. Moreover, the sliding clearance between the stem and the through hole in the cover plate and the sliding clearance between the sub-piston and the sub-cylinder can be reduced to improve the sealing performance therebetween.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a cylinder block, 2 a cylinder head, 3 a main piston that slides back and forth within a cylinder bore 4 of the cylinder block 1, and 5 a cylinder. Each shows a combustion chamber formed by recessing the lower surface of the head 2, and inside the combustion chamber 5,
An ignition plug 6 screwed onto the cylinder head 2 is visible at approximately the center thereof, and an intake port and an exhaust port (not shown) are open.

Reference numeral 7 designates a sub-cylinder bored in the cylinder head 2. The sub-cylinder 7 has its lower side opened into the combustion chamber 5 and its upper side opened into the upper chamber of the cylinder head on the upper surface of the cylinder head 2. A lid plate 8 is provided at the opening to the chamber to close it. In this case, the cover plate 8 is attached to the cylinder head 2.
It may be configured integrally with

Reference numeral 9 denotes a sub-piston that is slidably inserted into the sub-cylinder 7. A plurality of piston rings 10 are provided on the outer periphery of the sub-piston 9 near the combustion chamber 5. 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 increases, and when the secondary piston 9 moves back away from the combustion chamber 5, the volume of the combustion chamber increases and the compression ratio decreases. The sub-piston 9 is urged in the backward direction by a spring 11.

Further, a stepped recess 13 for connecting a stem 12, which will be described later, is provided on the back surface of the sub-piston 9 (the surface on the back side with respect to the combustion chamber 5). By fitting the integrally formed disk 14 into the lower end of the stem 12 extending from the bottom, and then fitting the snap spring 15,
In connecting the stem 12 to the sub-piston 9, the inner diameter of the stepped recess 13 is made slightly larger than the outer diameter of the disc 14 to form a gap 16 on the outer periphery of the disc 14, so that the stem 12 can be connected to the sub-piston. It is constructed so that it can shift only in a direction perpendicular to the axis of the reference numeral 9.

Further, the stem 12 is slidably inserted into a through hole 17 formed in the cover plate 8 and protrudes outward, while a hydraulic chamber 18 is formed between the back surface of the sub-piston 9 and the cover plate 8. Then, hydraulic oil from a hydraulic power source (not shown) is continuously supplied to the hydraulic chamber 18 via a hydraulic oil supply passage 20 with a check valve 19. Further, the stem 12 has a passage 21 communicating with the hydraulic chamber 18.
In addition, a spill port 22 is provided in a portion where the stem 12 projects outward from the cover plate 8 to allow the hydraulic oil in the hydraulic chamber 18 to flow out to the upper chamber of the cylinder head.

The number 23 indicates a spill ring which is one embodiment of the spill body, and the spill ring 23
is slidably fitted onto the end of the stem 12 that projects outward from the hydraulic chamber 18, so that when the stem 12 moves backward, the spill port 22 is closed by the spill ring 23, and when the stem 12 moves forward, the spill port 22 is closed by the spill ring 23. While the spill port 22 is configured to open, the spill ring 23 is configured to be moved in the axial direction of the stem 12 by rotation of a lever 24 whose tip end is engaged with the spill ring 23.

In this configuration, if the spill ring 23 is moved in the direction of the combustion chamber 5, that is, in the direction of closing the spill port 22, as shown by the two-dot chain line in FIG. The flow of hydraulic oil from port 19 has stopped.
Since the pressure inside the hydraulic chamber 18, which is constantly supplied with hydraulic oil from the attached hydraulic oil supply passage 20, increases,
The auxiliary piston 9 moves forward toward the combustion chamber, and when this movement progresses to the point where the spill port 22 is opened, hydraulic oil starts flowing out from the spill port 22, and the amount of this outflow and the amount of supply to the hydraulic chamber 18 are equal to each other. When the balance is achieved, the forward movement of the sub-piston 9 is stopped.

Furthermore, when the spill ring 23 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 22 is fully opened, the amount of flow from the spill port 22 increases, and the pressure in the hydraulic chamber 18 decreases. Therefore, the sub-piston 9 retreats away from the combustion chamber 5 due to the pressure of the combustion chamber 5 and/or the spring 11, and when this retreat progresses to the point where the spill port 22 is closed by the spill ring 23, the spill port When the outflow amount from 22 decreases and the outflow amount is balanced with the supply amount, the backward movement of the sub piston 9 will stop, and by moving the spill ring 23, the sub piston 9 can be moved forward or backward. The compression ratio can be changed arbitrarily.

Therefore, an actuator 25 related to the load on the internal combustion engine is connected to the other end of the lever 24 that engages with the spill ring 23, and the actuator 25 moves the spill ring 23 in proportion to the increase in the load on the internal combustion engine. By moving backward from the position indicated by the two-dot chain line, the compression ratio can be automatically controlled so that it gradually decreases as the engine load increases and gradually increases as the load decreases. In addition, it is possible to automatically control the compression ratio to gradually increase as the rotational speed of the internal combustion engine increases.Furthermore, by connecting the actuator 25 to a knocking sensor provided in the internal combustion engine, the compression ratio can be increased. It is also possible to control so that it is high when there is no knocking, and lowered accordingly when knocking occurs.

When the sub-piston 9 receives a large explosive force during the engine's explosion stroke, the sub-piston 9 moves back slightly due to this explosive force, closing the spill port 22, while the pressure inside the hydraulic chamber 18 momentarily increases. Since the check valve 19 closes and the hydraulic oil in the hydraulic chamber 18 is confined within the hydraulic chamber 18, the sub-piston 9 receives a large explosive force against the sub-piston 9 without moving backward. In this case, the outflow of the hydraulic oil until the spill port 22 closes and the subsequent rise in pressure of the hydraulic oil absorb the impact on the sub-piston 9 due to explosive combustion of the air-fuel mixture in the combustion chamber 5.・It's alleviation.

When the compression ratio is varied, the sub-piston 9 and the stem 12 slide back and forth at the same time.
Since the stem 12 is connected to the sub-piston 9 which is slidably fitted into the sub-cylinder 7 so as to be able to shift in a direction perpendicular to the axis of the sub-piston 9, the through-hole 17 and/or Even if there is a dimensional error in the center position of the stem 12 that would cause it to shift in a direction perpendicular to the axis, this dimensional error will cause the stem 1 to
This is absorbed by the displacement movement in the direction perpendicular to the axis of the secondary piston 9 of No. 2.

Therefore, due to the above-mentioned dimensional error, the secondary piston 9
Moreover, no twisting occurs in the forward and backward sliding movement of the stem 12, and both sliding movements become extremely smooth, and the machining accuracy can be significantly reduced.

In this case, the means for connecting the stem 12 to the auxiliary piston 9 so as to be able to freely shift is not limited to the one in the embodiment described above, and as shown in FIG.
Alternatively, the integrated disk 14a may be made large in diameter and provided with a recess 13a on its lower surface, and the sub-piston 9a may be fitted into the recess 13a with a gap 16a around its outer periphery, and then locked with a snap ring 15a. Other means may be used, such as directly connecting the stem to the sub-piston in a slidable manner without using the disk 14 or 14a, or without forming the stem and the sub-piston into an integral structure. By using the above-mentioned connected structure, it is possible to replace each part individually, and the stem and sub-piston can be made of different materials.
For example, it is possible to make the secondary piston made of ceramic for a stem made of metal.

The hydraulic oil that is continuously supplied to the hydraulic chamber 18 may be lubricating oil in the engine, but it is also possible to use hydraulic oil in the power steering mechanism or automatic transmission of an automobile.

Furthermore, in the embodiment described above, the spill ring 23 is used as an embodiment of the spill body, and the spill ring 23 is fitted onto the stem 12 so as to be slidable in the axial direction thereof, but as shown in FIG. The stem 12b is formed into a hollow shaft, and a spill rod 23b, which is another embodiment of the spill body, is inserted into the stem 12b so as to be slidable in the axial direction, and the spill rod 23b is slidably operated. In particular, the opening/closing position of the spill port 22b by the spill rod 23b may be configured to be displaced along the axial direction of the stem 12b. In this case, the opening/closing position of the spill port due to relative movement was performed by sliding the spill body in the axial direction with respect to the stem. Instead of sliding the body axially relative to the stem, this can also be done by rotating the spill body, as described below.

That is, FIGS. 5 and 6 show an embodiment in this case, in which a spill ring 23a having a gear on the outer periphery is used as an embodiment of the spill body, and this is attached to the stem 12c so as to be rotatable and slidable. On the other hand, the spill port in the stem 12c is formed into an inclined spill port 22c that is inclined with respect to the axis of the stem 12c, and the gear type spill ring 23c is rotated with respect to the cylinder head 2 by a bearing (not shown). A release port 26 is provided in the spill ring 23c, which is freely pivoted, and matches the inclined spill port 22c when the stem 12c slides back and forth. A rack rod 27 disposed perpendicularly to the stem 12c is engaged with the gear, and the spill ring 23c is rotated by sliding in the longitudinal direction of the rack rod 27, whereby the stem 12c is rotated.
By shifting the relief port 26 to the position or position relative to the inclined spill port 22c, the spill port 2 is removed by the spill ring 23a.
The opening/closing position of the stem 12c is configured to be displaced along the axial direction of the stem 12c (in this case, the stem 12c is held slidably but not rotatably, and the spill ring 23c here
The mechanism for rotating the stem 1 is not limited to the rack rod and gears in the embodiment, but other means may be used.
It goes without saying that the shapes of the ports 22c or 26 provided in the spill ring 23c or the spill ring 23c may be combined in any shape as required, as shown by the two-dot chain line in FIG.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 is a longitudinal sectional front view of the main parts of the engine, FIG. 2 is a sectional view taken from the side of FIG. 1, and FIG. 3 is a sectional view showing another embodiment of the sub-piston. , FIG. 4 and FIG. 5 are sectional views showing another embodiment of the spill body, and FIG. 6 is a plan view of FIG. 5. 1... Cylinder block, 2... Cylinder head, 3... Piston, 5... Combustion chamber, 7... Sub cylinder, 9... Sub piston, 8... Lid plate, 12,
12a, 12b, 12c... Stem, 18... Hydraulic chamber, 22, 22b, 22c... Spill port,
23, 23b, 23c... Spill body.

Claims (1)

[Claims] 1. A sub-piston is slidably inserted into a sub-cylinder communicating with a combustion chamber, the back surface of the sub-piston in the sub-cylinder is closed with a cover plate to form a hydraulic chamber, 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 pass through the cover plate from the sub-piston and protrude outside the sub-cylinder, and the hydraulic oil in the hydraulic chamber flows out from the protruding end of the stem. A spill port is provided at the protruding end of the stem, and a spill body is provided at 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 port is relatively movable 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 stem is further arranged so that the stem can be displaced relative to the sub-piston in a direction perpendicular to the axis of the sub-piston. A variable compression ratio device for an internal combustion engine, characterized in that the device is connected to a compression ratio variable device for an internal combustion engine.