JPH0116970B2 - - 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 in a stepless manner, but has the following problems.

[Problem that the invention seeks to solve]

That is, 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. Machining is extremely difficult, the cost required for this mechanical processing increases significantly, and maintenance and inspection to maintain a good sliding condition between the hollow stem and the control rod is difficult.

In addition, the prior art does not take into consideration the cooling of the auxiliary piston for variable compression ratio,
Since the temperature of this sub-piston rises considerably, not only will it cause seizures and lower durability, but overheating of the sub-piston will cause it to become a heat point, causing premature ignition. There were times when it happened.

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 difference between the hydraulic pressure of the hydraulic oil that is constantly supplied in the hydraulic chamber and the combustion chamber. occurs, the auxiliary piston moves forward toward the combustion chamber, and when the pressure in the combustion chamber increases in the next compression stroke, it moves back to its original position. As this is repeated, the sliding parts between the auxiliary piston and the auxiliary cylinder, 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 by forward operation of the control rod is low. 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 fluid to flow into the hydraulic chamber. When the sub-piston is moved backward by increasing the amount of hydraulic oil flowing out, the backward movement of the sub-piston is delayed by the amount of the forward movement during the intake stroke.In other words,
The responsiveness of the backward movement of the secondary piston to the backward movement of the control rod is significantly lower than that of the forward movement of the secondary piston, and the compression ratio when increasing the compression ratio is lower than the value corresponding to the position of the control rod. In particular, these trends,
In other words, the tendency for the responsiveness of the backward motion of the auxiliary piston to decrease and the tendency for the compression ratio to increase increase as the rotational speed of the internal combustion engine increases.

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

[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, a port for supplying hydraulic oil is connected to the hydraulic chamber, and the sub-piston is provided with a spring means for biasing the sub-piston in a backward direction, and A hollow cooling chamber that communicates with the hydraulic chamber through a through hole is formed in the sub-piston, and 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 is connected to the rear surface of the sub-piston. protrudes into the upper chamber of the cylinder head, the protruding end of the stem is provided with a spill port through which the hydraulic oil in the hydraulic chamber flows out through the cooling chamber, and the protruding end of the stem includes:
A spill body is configured such that the spill port is closed by the backward movement of the stem and opened by the forward movement of the stem, and the opening/closing position of the spill port by the spill body is displaceable in the axial direction of the stem. The cooling chamber is provided so as to be relatively movable, and furthermore, a through hole communicating the hydraulic chamber and the cooling chamber is provided at a portion through which hydraulic oil flows into the cooling chamber along the inner wall surface of the cooling chamber.

[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.

In this case, the present invention protrudes the stem into the upper chamber of the cylinder head and provides the spill port and the spill body at the protruding end. 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 performed extremely easily.

On the other hand, the hydraulic oil supplied to the hydraulic chamber flows through the cooling chamber in the sub-piston and then flows out from the spill port, so that the hydraulic oil can
The secondary piston can be forcibly cooled. In this case, by providing a passage for hydraulic oil from the hydraulic chamber to the cooling chamber at a location where the hydraulic oil flows from the hole into the cooling chamber along the inner wall surface of the cooling chamber, Since the low-temperature hydraulic oil flows at a relatively high flow rate along the inner wall surface of the cooling chamber in the sub-piston where the temperature is high, the cooling performance for the sub-piston can be made to a high value.

Moreover, the flow rate of the hydraulic oil when it flows out from the oil pressure chamber, through the cooling chamber, and from the spill port is the same when the sub-piston is moved forward and when the sub-piston is moved backward. Since the flow rate of the hydraulic oil flowing through the cooling chamber of the sub-piston is the same regardless of whether the compression ratio is high or low, the above-mentioned high cooling performance of the sub-piston by the hydraulic oil can be achieved independently of changes in the compression ratio. In other words, the compression ratio can be maintained at all times under any state of compression ratio, so it is possible to reliably prevent a decrease in durability due to seizure of the sub-piston, and also to ensure that there is no risk of premature ignition caused by the sub-piston. It can be reduced.

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 when the auxiliary piston and the auxiliary cylinder move can be reduced by the spring means, the sliding parts between the auxiliary piston and the auxiliary cylinder, and the sliding parts between the stem and the spill body can be worn out, and their durability can be reduced. The performance can be improved without complicating the structure, increasing the size, or increasing the weight.

Furthermore, the spring means provided for the secondary 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 backward movement of the sub-piston to the operation can be greatly improved, and the tendency for the compression ratio to become higher than the value corresponding to the position of the spill body when increasing the compression ratio can be reliably reduced. .

〔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, 3 is a main piston that slides back and forth 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 indicates a sub-cylinder bored in the cylinder head 2. The sub-cylinder 7 opens into the combustion chamber 5 on the lower side and into the upper chamber of the cylinder head on the upper surface of the cylinder head 2 on the upper side.
A cover plate 8 is provided at the opening to the upper chamber of the cylinder head to close the opening.

Reference numeral 9 indicates a sub-piston slidably inserted into the sub-cylinder 7, and a plurality of piston rings 10 are provided on the outer periphery of the sub-cylinder 9 in a portion close to the combustion chamber 5. When the 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 auxiliary piston 9 moves back away from the combustion chamber 5, the volume of the combustion chamber 5 increases and the compression ratio increases. The sub-piston 9 is provided with a spring 10 that biases the sub-piston 9 in the backward direction, and a hollow cooling chamber 12 is provided inside the sub-piston 9. The sub piston 9 is formed with a recess so as to close the cooling chamber 12.
A stem 14 extending from the center of the sub-piston 9 in the axial direction of the sub-cylinder 7 is attached to the disk 13 fixed to the disk 13 .
The stem 14 slidably penetrates the cover plate 8 and projects into the upper chamber of the cylinder head. A chamber 15 is formed, and the hydraulic chamber 15 and the cooling chamber 12 are connected to each other through a through hole 16 bored in the axial direction of the sub-piston 9 in a portion of the disk 13 close to the inner wall surface of the cooling chamber 12. Further, hydraulic oil from a hydraulic source (not shown) is supplied to the hydraulic chamber 15 via a port 18 with a check valve 17.

The stem 14 is provided with a passage 15 that opens into the cooling chamber 12, and the stem 14 is connected to the lid plate 8.
A spill port 20 is provided at the projecting end that projects further into the upper chamber of the cylinder head to allow the hydraulic oil in the hydraulic chamber 15 to flow out into the upper chamber of the cylinder head after passing through the cooling chamber 12.

Further, reference numeral 21 indicates a spill ring which is one embodiment of the spill body, and the spill ring 21
is slidably fitted into the protruding end of the stem 14 into the upper chamber of the cylinder head, so that when the stem 14 moves backward, its spill port 20 is closed by the spill ring 21, and the stem 14 moves forward. While the spill port 20 is configured to open when the engine is in motion,
The spill ring 21 is configured to be moved in the axial direction of the stem 14 by rotation of a lever 22 whose tip end is engaged with the spill ring 21.

In this configuration, the spill ring 21 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 20, as shown by the two-dot chain line in the figure, the flow of hydraulic oil from the spill port 20 will be stopped by closing the spill port 20, and the flow will be reversed. Stop valve 17
As the pressure in the hydraulic chamber 15 to which hydraulic oil is supplied from the attached port 18 and the cooling chamber 12 communicating therewith increases, the sub-piston 9 advances toward the combustion chamber, and this advancement causes the spill port 20 to open. When the hydraulic oil reaches this point, the hydraulic oil starts flowing out from the spill port 20, and when the amount of this outflow and the amount of supply to the hydraulic chamber 15 are balanced, the advance of the sub-piston 9 is stopped.

Furthermore, when the spill ring 21 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 20 is fully opened.
Since the pressure in the hydraulic chamber 15 decreases due to the increase in the amount of flow from the oil pressure chamber 15, the secondary piston 9 retreats away from the combustion chamber 5 due to the pressure in the combustion chamber 5 and the spring 11, and this retreat causes the pressure in the oil pressure chamber 15 to decrease. When the flow progresses to the point where it is closed by the spill ring 21, the amount of outflow from the spill port 20 decreases, and when the amount of outflow is balanced with the amount of supply, the backward movement of the sub piston 9 is stopped, and the spill ring By the movement operation 21, the sub piston 9 can be moved back and forth in a stepless manner.

Therefore, an actuator 23 related to the load of the engine is connected to the other end of the lever 22 that engages with the spill ring 21, and the actuator 23 moves the spill ring 21 in proportion to the increase in the engine load. By moving backward from the position of , the compression ratio can be automatically controlled so that it becomes progressively lower as the engine load increases and becomes gradually higher as the load decreases.In addition to this relationship to the load, It is also possible to automatically control the compression ratio so that it gradually increases as the engine speed increases.Furthermore, the actuator 23 can be connected to a knocking sensor provided in the engine to increase the compression ratio when there is no knocking. , it is also possible to automatically control to lower the level when knocking occurs.

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 20, while the pressure inside the hydraulic chamber 15 momentarily increases. When the check valve 17 closes, the hydraulic chamber 15 and the cooling chamber 12 are closed.
Since the hydraulic oil in the hydraulic chamber 15 and the cooling chamber 12 are confined, the sub piston 9
The piston bears a large explosive force against the auxiliary piston without retreating, and in this case, the outflow of the hydraulic oil until the spill port 20 closes and the subsequent increase in pressure of the hydraulic oil are caused by the pressure inside the combustion chamber 5. This absorbs and alleviates the impact on the auxiliary piston 9 caused by the explosive combustion of the air-fuel mixture.

The hydraulic oil supplied to the hydraulic chamber 15 from the port 18 with the check valve 17 enters the cooling chamber 12 from the hydraulic chamber 15 through the through hole 16, and enters the cooling chamber 12 from the hydraulic chamber 15 to the sub piston 9.
After cooling, the hydraulic oil flows out from the spill port 20, and when the hydraulic oil flows from the oil pressure chamber 15 through the cooling chamber 15 and out of the spill port 20, the flow rate of the hydraulic oil is as follows: The flow rate of the hydraulic oil flowing through the cooling chamber 12 in the sub piston 9 is the same regardless of whether the compression ratio is high or low. Therefore, cooling of the auxiliary piston 9 by the hydraulic oil can be always ensured regardless of changes in the compression ratio, in other words, under any compression ratio state.

Furthermore, by configuring the through hole 16, which is the inlet of hydraulic fluid from the hydraulic chamber 15 to the cooling chamber 12, to be bored in the axial direction of the sub-piston 9 at a portion close to the inner wall surface of the cooling chamber 12, Since the hydraulic oil flowing into the cooling chamber 12 from the through hole 16 flows along the inner wall surface of the cooling chamber 12, the flow velocity of the hydraulic oil along the inner wall surface of the cooling chamber 12 increases, improving the cooling performance for the sub-piston 9. It can be improved.

Cooling the sub-piston 9 in this manner can prevent the sub-piston 9 from seizing, and can also contribute to preventing premature ignition caused by the combustion chamber side surface of the sub-piston becoming hot.

In this case, in order to further improve the cooling performance of the sub-piston 9, as shown in FIGS. 3 and 5, a Alternatively, the inner surface area of the cooling chamber 12 may be increased by providing a plurality of fins 24 extending to the inner surface of the cooling chamber 12, or, as shown in FIG. The extension part 25 is provided so that the hydraulic oil in the cooling chamber 12 flows out from the tip of the extension part 25, in other words, from the inner bottom surface of the cooling chamber 12, so that the temperature is the highest in the sub piston 9. The flow velocity of the hydraulic oil in the vicinity of the center of the head where the height is increased can be increased, and by slanting the through hole 16 in the disk 13 with respect to the axis of the secondary piston 9, the hydraulic oil in the cooling chamber 12 can be A swirl flow around the axis of the piston may be generated.

Note that as the hydraulic oil supplied to the hydraulic chamber 15, 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 that distributes it to various rotating or sliding parts to the port 18 with a check valve 17 to the hydraulic chamber 15, while the oil flowing out from the spill port 20 is guided to the port 18 with a check valve 17. It is discharged into the upper chamber of the cylinder head and generally returned to the oil pan (not shown) at the bottom of the cylinder block 1 together with lubricating oil for the valve mechanism (not shown) provided in the upper chamber. The structure is simple because it can be done as follows.

When using hydraulic oil in an automobile's power steering mechanism or automatic transmission as hydraulic oil for the hydraulic chamber 15, a passage 2 branched from these hydraulic oil pumps 26 is used as shown in FIG.
7 to port 1 with check valve 17 to the hydraulic chamber 15
8, a cover 28 is provided on the outside of the lid plate 8 to cover the spill ring 21 and the stem 14,
The oil flowing out from the spill port 20 can be returned to the oil reservoir 31 in the power steering mechanism or automatic transmission through a passage 29 connected to the cover 28, through an oil cooler 30 provided in the passage 29.

Further, in the above embodiment, a spill ring 21 was used as an embodiment of the spill body, but
As shown in FIG. 7, a stem 14a is formed into a hollow shaft, a spill rod 21a is slidably inserted into the stem 14a, and the spill port 20a is opened and closed by slidingly operating the spill rod 21a. Alternatively, the spill port in the stem 11b may be tilted with respect to the axis of the stem 14 as shown in FIGS. 8 and 9. While forming an inclined spill port 20b, a gear type spill ring 21b is rotatably and slidably fitted on the outer periphery of the stem 14, and the spill ring 21b is connected to the cylinder head 2 by a bearing (not shown). A relief port 32 is provided in this spill ring 21b so that it matches the inclined spill port 20b when the stem 14 slides back and forth, and a relief port 32 is provided in the teeth on the outer periphery of this spill ring 21b. A rack rod 22 disposed perpendicularly to the stem 14 is engaged, and by sliding the rack rod 33 in the longitudinal direction, the spill ring 21b is rotated, and the stem 14b is rotated.
It is also possible to configure the opening/closing position of the spill port 20b to be displaced along the axial direction of the stem 14b by shifting the relief port 32 to or from the inclined spill port 20b. (At this time, stem 14
b is held slidably but not rotatable, and the mechanism for rotating the spill ring 21b here is not limited to the rack and pinion of the embodiment, but other means may also be used), in which case the inclined spill port A relief port may be provided on the spill ring side, and a relief port may be provided on the stem side, and the ports provided on the stem or spill ring may be combined in any shape as required, as shown by the two-dot chain line in Figure 8. It will be done.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG. 1 is a vertical sectional front view of the main engine parts showing the first embodiment, FIG. 2 is a cross-sectional view taken from FIG. 1, and FIGS. FIG. 5 is a sectional view showing another example of the sub-piston, FIG. 5 is a cross-sectional view taken from the side of FIG. Another embodiment of the spill body and spill port, FIG. 9 is a plan view of FIG. 8. 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 7... Sub cylinder, 9... Sub piston, 15... Hydraulic chamber, 12... Cooling chamber, 1
4...Stem, 16...Through hole, 20, 20a, 2
0b... Spill port, 17... Check valve, 21,
21a, 21b... Spill body.

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, a spring means is provided in the sub-piston for biasing the sub-piston in a backward direction, and a spring means is provided in the sub-piston to connect to the hydraulic chamber through a through hole. While forming a communicating hollow cooling chamber, 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 protrudes into the upper chamber of the cylinder head. A spill port is provided at the end so that the hydraulic oil in the hydraulic chamber flows out through the cooling chamber, and the spill port is closed at the protruding end of the stem by the backward movement of the stem. A spill body whose spill port is opened by forward motion 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 further, the spill body is configured to be movable relative to each other 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 through hole communicating with the cooling chamber is provided at a portion through which hydraulic oil flows into the cooling chamber along an inner wall surface of the cooling chamber. 2. The variable compression ratio device for an internal combustion engine according to claim 1, wherein a fin extending in the direction of flow of hydraulic oil from the through hole is provided on the inner surface of the cooling chamber of the sub-piston. 3. The variable compression ratio device for an internal combustion engine according to claim 1, wherein the outlet of the hydraulic oil from the cooling chamber to the spill port in the auxiliary piston is located on the inner bottom surface of the cooling chamber. . 4. The internal combustion engine according to claim 1, wherein the through hole is configured to impart swirl along the inner wall surface of the cooling chamber to the hydraulic oil flowing from the through hole into the cooling chamber. A variable compression ratio device in an engine.