JPH0116971B2 - - 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 with good responsiveness during operation of the internal combustion engine.

[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 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 having an oil passage communicating with the atmosphere is slidably inserted into the hollow stem, and by sliding the control rod, the opening/closing position of the spill port is adjusted in the axial direction of the stem. Since the auxiliary piston is configured to move back and forth by being displaced, it has the advantage of being able to change the compression ratio steplessly, but has the following problems.

[Problem that the invention seeks to solve]

That is, in the prior art, the opening/closing position of the spill port in the 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 the control rods cannot be slid with a light force, the response of changing the compression ratio is low and the mechanism for sliding the control rods becomes large.

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.
Maintenance and inspection to maintain a good sliding condition between the hollow stem and the control rod was difficult.

Moreover, in this prior art variable compression ratio device, the forward movement of the sub-piston is performed by the pressure of the hydraulic oil in the hydraulic chamber, and the backward movement of the sub-piston is performed by the pressure in the combustion chamber. When the pressure becomes negative (atmospheric pressure) during the intake stroke, the secondary piston moves forward due to the pressure in the hydraulic chamber, and when the pressure in the combustion chamber increases during the compression stroke, it retreats to its original position. Since one reciprocating motion is repeated for each cycle of the engine, wear increases on the sliding surfaces between the sub-cylinder and the sub-piston, and the sliding surfaces between the stem and the control rod, resulting in low durability. In particular, this decrease in durability increases in proportion to the rotational speed of the internal combustion engine.

Furthermore, in this prior art, the forward movement of the secondary piston is achieved by stopping the flow of hydraulic oil from the hydraulic chamber at the rear surface of the secondary piston, by moving the secondary piston forward by forward operation of the control rod. On the other hand, the secondary piston moves forward toward the combustion chamber during the intake stroke, and this forward movement causes hydraulic fluid to flow into the hydraulic chamber, making it difficult to operate the control rods backward. When the secondary piston is retracted by increasing the amount of hydraulic oil flowing out in the hydraulic chamber, the backward movement of the secondary piston is
This results in a delay corresponding to the amount of forward movement during the intake stroke.In other words, the responsiveness of the sub piston's backward movement to the control rod's retracting operation becomes significantly lower than that of the sub piston's forward movement, and the compression ratio is increased. In this case, the compression ratio tends to be higher than the value corresponding to the position of the control rod.

An object of the present invention is to provide a variable compression ratio device that solves these problems without increasing the size of the device.

[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 is formed on the back surface of the sub-piston, and 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 stem extends in the axial direction of the sub-cylinder. The tip of the stem protrudes into the upper chamber of the cylinder head, the protruding end of the stem is provided with a spill port for allowing the hydraulic oil in the hydraulic chamber to flow out, and the outer periphery of the protruding end of the stem is provided with a spill port. A spill body that closes the spill port when the stem moves backward and opens the spill port when the stem moves forward is moved relative to the spill body so that the opening/closing position of the spill port by the spill body can be displaced in the axial direction of the stem. A plate spring is movably fitted and is further mounted between the tip of the stem and the upper surface of the cylinder head to bias the sub-piston in the backward direction.

[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 leaf spring, 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.

In this case, as described above, 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. Unlike the prior art, the oil pressure of the hydraulic oil in the hydraulic chamber does not act to prevent the spill body from moving back and forth, so the spill body can be moved with a light force regardless of the hydraulic oil pressure in the hydraulic chamber. The spill body can be moved back and forth, and the mechanism for moving the spill body back and forth can be made smaller.

Moreover, in the present invention, the stem protrudes into the upper chamber of the cylinder head, and a spill port and a spill body are provided at this protruding end, so that the sliding portion between the stem and the spill body is changed from the spill port to the spill body. High-precision mechanical processing for completely closing can be performed much more easily than in the case of the prior art, so 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 leaf spring that biases the secondary piston in the backward direction, it is possible to shorten the distance that the secondary piston moves forward due to the negative pressure in the combustion chamber during the intake stroke of the internal combustion engine. Wear of the sliding surfaces between the head and the sub-piston and between the stem and the spill body is reduced, and a decrease in durability can be prevented.

Furthermore, the leaf spring provided for the sub-piston is,
As mentioned above, by reducing the distance that the auxiliary piston moves forward during the intake stroke, the amount of hydraulic oil that flows into the hydraulic chamber during this forward movement is reduced, and the backward movement of the auxiliary piston is accelerated, thereby reducing spills. When the secondary piston is retracted by increasing the amount of hydraulic oil flowing out from the spill port in the hydraulic chamber by retracting the body, the delay in the backward movement of the secondary piston can be reduced. The responsiveness of the sub-piston's backward movement to the operation can be greatly improved, together with the fact that the spill body can be slid with a light force. This makes it possible to reliably reduce the tendency for the value to be higher than the corresponding value.

Furthermore, by configuring the means for biasing the sub-piston in the backward direction as a leaf spring mounted between the upper surface of the cylinder head and the tip of the stem, this biasing means can be applied to the stem. There is no need to increase the length of the stem as in the case of a fitted coil spring, and the length of the stem can be shortened to achieve miniaturization.

〔Example〕

Embodiments of the present invention are shown below in the drawings (Figs. 1 to 3).
In the figure, reference numeral 1 is a cylinder block, reference numeral 2 is a cylinder head, reference numeral 3 is a main piston that slides back and forth within the cylinder bore 4 of the cylinder block 1, and reference numeral 5 is a concave portion 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, 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, and the sub-cylinder 7 has a lower side facing the combustion chamber 5.
The upper side opens into the upper chamber of the cylinder head on the upper surface of the cylinder head 2, and the opening to the upper chamber of the auxiliary 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. A plurality of piston rings 10 are provided on the outer periphery of the sub-piston 9 in a portion close to the combustion chamber 5. When the auxiliary piston 9 moves forward toward the combustion chamber 5, the volume of the combustion chamber decreases and the compression ratio increases, and when the auxiliary piston 9 retreats away from the combustion chamber 5, the volume of the combustion chamber increases and the compression ratio decreases. 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.
, extends slidably through the cover plate 8 and protrudes 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 supplied through a port 14 with a check valve 13. 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 from the cover plate 8 is provided with a passageway 15 that allows the hydraulic oil in the hydraulic chamber 12 to flow out to the upper chamber of the cylinder head. A spill port 16 is drilled to allow the liquid to flow.

Reference numeral 17 designates a spill ring, which is an embodiment of the spill body, and the spill ring 17 is slidably fitted onto the end of the stem 11 that projects into the upper chamber of the cylinder head, thereby preventing the backward movement of the stem 11. The spill port 16 is closed by the spill ring 17 when the stem 11 moves forward, and the spill port 16 is opened when the stem 11 moves forward. It is configured to adjust the movement of the stem 11 in the axial direction by rotation.

One end of the leaf spring 21a is fixed to the upper surface of the cylinder head 2 with a bolt 28 or the like, and the tip of the leaf spring 21a is attached to the lower surface of the nut 29 fixed to the tip of the stem 11. A spring 21a is configured to lock the sub-piston 9 so as to bias it in the backward direction.

The other end of the lever 18 engaged with the spill ring 17 is connected to a diaphragm mechanism 22, which is one embodiment of an actuator. This diaphragm mechanism 22 has a built-in diaphragm 24 connected to the other end of the lever 18 via a rod 23, and has a pressure chamber 2 partitioned by the diaphragm 24.
5 is provided with a spring 26 that pushes the other end of the lever 18 downward in the figure, that is, urges the spin ring 17 in the backward direction, and connects the pressure chamber 25 to the engine via a negative pressure transmission passage 27. By connecting to an intake manifold (not shown) and introducing intake pipe negative pressure into the pressure chamber 25, when the intake pipe negative pressure increases (becomes closer to vacuum) as the engine load decreases, this The spin ring 17 is configured to slide forward in proportion.

In this configuration, the spin ring 17 is
If the movement operation is performed in the direction of the combustion chamber 5, that is, in the direction of closing the spill port 16 as shown by the two-dot chain line in the figure, the flow of hydraulic oil from the spill port 16 will be stopped by closing the spill port 16, and the flow will be reversed. Stop valve 13
As the pressure in the hydraulic chamber 12, which is constantly supplied with hydraulic oil from the attached port 14, increases, the auxiliary piston 9 moves forward toward the combustion chamber 5, and when this forward movement reaches the point where the spill port 16 is opened, the spill Hydraulic oil starts flowing out from the port 16, and when the amount of this outflow and the amount of supply to the hydraulic chamber 12 are balanced, the forward movement 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 and the amount of outflow from the spill port 16 increases.
Since the pressure in the hydraulic chamber 12 decreases, the secondary piston 9
is retreated away from the combustion chamber 5 due to the pressure of the combustion chamber 5 and the leaf spring 21a, and when this retreat progresses to the point where the spill port 16 is closed by the spill ring 17, the amount of outflow from the spill port 16 decreases. When 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 can be moved back and forth in a stepless manner. can.

In this case, since the spill ring 17 is connected to the diaphragm mechanism 22, which is an example of an actuator, via the lever 18, when the intake pipe negative pressure gradually increases (becomes closer to vacuum) as the engine load decreases, the diaphragm Since the spill ring 17 moves forward from the solid line position to the two-dot chain line position by the mechanism 22, the compression ratio is automatically controlled so that it gradually increases as the engine load decreases and gradually decreases as the load increases. become. Also, spill ring 1
In addition to being related to the load of the engine, the actuator represented by the diaphragm mechanism 22 for moving the engine 7 is also related to the engine speed, so that the compression ratio is gradually increased as the engine speed increases. The compression ratio is automatically controlled when there is no knocking, or the engine is equipped with an actuator for moving the spill ring.
When knocking occurs, it can be automatically controlled to lower the level accordingly.

During the engine's explosion stroke, when the secondary piston 9 receives a large explosive force, the secondary piston 9 moves back slightly due to this explosive force, closing the spill port 16, while the pressure inside the hydraulic chamber 12 momentarily increases. The check valve 13 closes and the hydraulic fluid in the hydraulic chamber 12 becomes confined within the hydraulic chamber 12.
This supports a large explosive force against the secondary piston, and in this case, the outflow of the hydraulic oil until the spill port 16 closes and the subsequent pressure increase of the hydraulic oil cause the air-fuel mixture in the combustion chamber 5 to This absorbs and alleviates the impact on the sub-piston 9 due to explosive combustion.

In the embodiment described above, when the leaf spring 21a that biases the sub-piston 9 in the backward direction is not provided, negative pressure (below atmospheric pressure) is generated in the combustion chamber 5 during the intake stroke of the engine. When this happens, the sub piston 9 absorbs this negative pressure and pressure chamber 12.
It moves back and forth once per cycle depending on the pressure change inside the combustion chamber 5, such as moving forward toward the combustion chamber 5 due to the internal pressure and retreating to the original position during the next compression ratio/explosion stroke. It turns out.

On the other hand, in the present invention, for the sub-piston 9,
A leaf spring 2 that urges the sub-piston 9 in the backward direction
1a, even if negative pressure is generated in the combustion chamber 5 during the intake stroke of the engine, the sub-piston 9 is prevented from moving in the direction of the combustion chamber 5 by the leaf spring 21a provided for the sub-piston 9. Since the forward movement is prevented, the stroke when the sub piston 9 reciprocates in each cycle can be reduced.

In this case, when two cylinders are adjacent to each other, the leaf spring is a top type leaf spring 21b whose approximately central portion is fixed to the cylinder head with a bolt 28a or the like, as shown in FIG. This makes it possible to urge the sub pistons 9, 9 in the two cylinders at the same time in the backward direction at both ends, which is preferable for multi-cylinder engines.

The hydraulic oil supplied to the hydraulic chamber 12 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.
Further, in the above embodiment, the spill ring 17 was used as one embodiment of the spill body, but the fifth embodiment
As shown in FIG. 6 and 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 provided on the outer periphery of the stem 11a. The spill ring 17a is slidably fitted onto the cylinder head 2 by a bearing (not shown), and the spin ring 17a is supported by a bearing (not shown).
, a relief port 30 is provided so as to match the inclined spill port 16a when the stem 11a slides back and forth, and a relief port 30 is provided on the teeth on the outer periphery of the spill ring 17a in a direction perpendicular to the stem 11a. The rack rods 31 are engaged, and the rack rods 3
Spill ring 17a by sliding in the longitudinal direction of 1
The opening/closing position of the spill port 16a is displaced along the axial direction of the stem 11a by rotating the escape port 32 and shifting it to or from the inclined spill port 16a of the stem 11a. (In this case, the stem 11a is held slidably but not rotatably, and the mechanism for rotating the spill ring 17a is not limited to the rack and pinion of the embodiment. (Other means may be used)
In this case, the inclined spill port may be provided on the spill ring side and the escape port may be provided on the stem side,
Furthermore, the port shapes provided on the stem or spill ring may be combined with arbitrary shapes as shown by the two-dot chain line in FIG. 5, if necessary.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and 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 FIG. 1, and FIG. −
4 is a sectional view showing another embodiment, FIG. 5 is a diagram of another embodiment of a spill body and a spill port, and FIG. 6 is a plan view of FIG. 5. 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 7... Sub cylinder, 9... Sub piston, 12... Hydraulic chamber, 11... Stem, 1
6, 16a... Spill port, 17, 17a...
Spill body, 13...Check valve, 21a, 21b...
Leaf spring.

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, a hydraulic chamber is formed on the back surface of the auxiliary piston, and a hydraulic chamber is formed on the back surface of the auxiliary piston. A port for supplying hydraulic oil is connected to the hydraulic chamber, and 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 stem is connected to the rear surface of the sub-piston. 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 and the stem moves forward. A spill body in which the spill port is opened by movement is fitted so that the spill body can move relative to the tip of the stem so that the opening/closing position of the spill port by the spill body can be displaced in the axial direction of the stem. A variable compression ratio device for an internal combustion engine, characterized in that a leaf spring is installed between the cylinder head and the upper surface of the cylinder head to bias the sub-piston in a backward direction. 2. A patent characterized in that the leaf springs that bias the sub-pistons in two adjacent cylinders in the backward direction are configured into a single leaf spring, and the substantially central portion of the leaf spring is fixed to the upper surface of the cylinder head. A variable compression ratio device for an internal combustion engine according to claim 1.