JPH0116973B2 - - 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.

[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 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 responsiveness 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 that is opened and closed by the control rod is provided in a portion inside the hydraulic chamber. In other words, the sliding portion between the hollow stem and the control rod is Because it is located at the back of the shaft, mechanical processing is required when finishing 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. This is extremely difficult, and the cost required for this mechanical processing increases considerably, and maintenance and inspection to maintain a good sliding condition between the hollow stem and the control rod is difficult.

Furthermore, this prior art variable compression ratio device does not take into account the positional relationship between the top surface of the tip of the sub-piston and the inner wall surface of the combustion chamber when the sub-piston is moved most forward under low load conditions. Not yet,
When the load is low, even though the combustion state of the air-fuel mixture in the combustion chamber is originally poor, when the sub-piston is moved forward the most, the top surface of the tip of the sub-piston is recessed from the inner wall surface of the combustion chamber. As a result, the combustion condition at low loads becomes increasingly worse, the occurrence of knocking increases, and the amount of harmful components in the exhaust gas increases.

Furthermore, in the prior art, when the pressure in the combustion chamber becomes negative pressure (below atmospheric pressure) during the intake stroke, a large pressure is created between the hydraulic pressure of the hydraulic oil that is constantly supplied in the hydraulic chamber and the combustion chamber. When a difference occurs, the secondary 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. Since the movement is repeated, the sliding parts between the auxiliary piston and the auxiliary cylinder, and the sliding parts between the stem and the control rod are subject to large wear, resulting in low durability.

In addition, in the 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 sub-piston is moved backward by increasing the amount of hydraulic oil flowing out in the hydraulic chamber, the backward movement of the sub-piston is delayed by the amount of forward movement during the intake stroke.In other words, the control rod The responsiveness of the backward movement of the secondary piston to the backward movement is significantly lower than that of the forward movement of the secondary piston, and the compression ratio when increasing the compression ratio is higher than the value corresponding to the position of the control rod. This was the case.

An object of the present invention is to provide a variable compression ratio device that eliminates these problems.

[Means for solving problems]

In order to achieve this object, the present invention provides a cylinder head with a sub-cylinder opening into a combustion chamber whose inner wall surface is formed into a spherical shape, a sub-piston is slidably inserted into the sub-cylinder, and the sub-piston is slidably inserted into the sub-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 spring means for biasing the sub-piston in the backward direction. A stem extending in the axial direction of the auxiliary cylinder is connected to the rear surface, and the tip of the stem projects into the upper chamber of the cylinder head, and the protruding end of the stem is configured to allow hydraulic oil in the hydraulic chamber to flow out. A spill port is provided on the outer periphery of the protruding end of the stem, and a spill body is provided on the outer periphery of 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 auxiliary piston is provided so that the opening/closing position of the spill port by the body can be moved in the axial direction of the stem, and further, the secondary piston is provided with an opening/closing position of the spill port by the spill body at a position closest to the combustion chamber. A regulating means is provided for regulating the forward movement of the sub-piston to a position where the top surface of the tip of the sub-piston substantially coincides with the inner wall surface of the combustion chamber, and the top surface of the tip of the sub-piston is aligned with the inner wall surface of the combustion chamber. The structure is such that a concavity is formed in a substantially continuous spherical shape.

[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, as described above,
Since 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, the operation of moving the spill body back and forth requires the operation in the hydraulic chamber as in the prior art. Since the hydraulic pressure of the oil does not act to prevent the spill body from moving back and forth, the spill body can be moved back and forth in the hydraulic chamber with a light force regardless of the hydraulic pressure of the hydraulic oil, and the spill body can be moved back and forth. The mechanism for operation 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 the 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 performed extremely easily.

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, wear of the sliding parts between the auxiliary piston and the auxiliary cylinder, and the sliding parts between the stem and the spill body, as well as the durability of these parts, 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 sub-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 sub-piston is accelerated.
When retracting the secondary piston by increasing the amount of hydraulic oil flowing out from the spill port in the hydraulic chamber by retracting the spill body, the delay in the backward movement of the secondary piston can be reduced. Combined with the fact that the spill body can be moved back and forth with a light force, the responsiveness of the sub piston's backward movement to the backward operation can be significantly improved, and the compression ratio when increasing the compression ratio corresponds to the position of the spill body. This can reliably reduce the tendency for the value to be higher than the specified value.

Further, the present invention allows the forward movement of the secondary piston to be caused by the forward movement of the secondary piston when the opening/closing position of the spill port by the spill body is set to the position closest to the combustion chamber. While a regulating means is provided to regulate the position to approximately coincide with the wall surface, the top surface of the tip of the sub-piston is recessed into a spherical shape that is substantially continuous with the inner wall surface of the combustion chamber, thereby improving the shape of the combustion chamber at low loads. can be made into a nearly perfect spherical shape, so even though the combustion chamber is provided with an auxiliary piston for varying the compression ratio, the combustion condition deteriorates at low loads when the compression ratio is at its highest. This makes it possible to reliably prevent frequent knocking and deterioration of exhaust gas due to the auxiliary piston for varying the compression ratio.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 is a cylinder block, reference numeral 2 is a cylinder head, reference numeral 3 is a piston that reciprocates within the cylinder bore 4 of the cylinder block 1, and reference numeral 5 is the cylinder. Each shows a roughly spherical combustion chamber formed by recessing the lower surface of the head 2, and the combustion chamber 5 has an ignition plug 6 screwed onto the cylinder head 2 at approximately the center thereof, and an intake port (not shown) and Exhaust port is open.

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 denotes a sub-piston that is slidably inserted into the sub-cylinder 7, and the sub-piston 9 is inserted into the combustion chamber 5.
When the secondary piston 9 moves forward in the direction of , the volume of the combustion chamber 5 decreases and the compression ratio becomes high, and when the sub piston 9 moves backward away from the combustion chamber 5, the volume of the combustion chamber 5 increases and the compression ratio becomes low. The secondary piston 9 is provided with a spring 10 for urging the secondary piston 9 in the backward direction, and the secondary piston 9 is provided with a spring 10 for urging the secondary piston 9 toward the combustion chamber. A regulating stepped portion 11 is provided which comes into contact with the piston so that it does not advance any further when the tip top surface 12 of the sub-piston 9 reaches its maximum level and substantially coincides with the inner wall surface 13 of the combustion chamber 5. A recess is formed in a spherical shape having the same curvature as the curvature of the spherical wall surface 13 of the combustion chamber 5.

A stem 14 extending in the axial direction from the center of the sub-piston 9 is connected to the back surface of the sub-piston 9 (the surface on the back side with respect to the combustion chamber 5).
is slidably penetrated through the cover plate 8 and protrudes into the upper chamber of the cylinder head, while a hydraulic chamber 15 is formed between the back surface of the sub-piston 9 and the cover plate 8, and the hydraulic chamber 1
5, the hydraulic oil from the hydraulic source (not shown) is supplied to the check valve 1.
6 through port 17. The stem 14 also includes a passage 18 that communicates with the hydraulic chamber 15.
In addition, a spill port 19 is provided in a portion where the stem 14 projects outward from the cover plate 8 for allowing the hydraulic oil in the hydraulic chamber 15 to flow out to the upper chamber of the cylinder head.

The reference numeral 20 indicates a spill ring which is one embodiment of the spill body, and the spill ring 20
is slidably fitted into the protruding end of the upper chamber of the cylinder head of the stem 14, so that when the stem 14 moves backward, the spill port 19 is closed by the spill ring 20, and when the stem 14 moves forward, the spill port 19 is closed by the spill ring 20. While the spill port 19 is configured to open, the spill ring 20 is configured to be moved in the axial direction of the stem 14 by rotation of a lever 21 whose tip end is engaged with the spill ring 20.

In this configuration, the spill ring 20 is
As shown by the two-dot chain line in the figure, if the movement is performed in the direction of the combustion chamber 5, that is, in the direction of closing the spill port 19, the flow of hydraulic oil from the spill port 19 will be stopped by closing the spill port 19. As the pressure in the hydraulic chamber 15 to which hydraulic oil is supplied from the port 17 with the check valve 16 increases, the auxiliary piston 9 moves forward toward the combustion chamber 5, and this movement continues until the spill port 19 opens. As the hydraulic oil advances, the hydraulic oil starts flowing out from the spill port 19, 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 20 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 19 is fully opened, the outflow amount increases, and the pressure in the hydraulic chamber 15 decreases. 9
is retreated away from the combustion chamber 5 due to the pressure of the combustion chamber 5 and the spring 10, and when this retreat progresses to the point where the spill port 19 is closed by the spill ring 20, the amount of outflow from the spill port 19 decreases. However, when this outflow amount is balanced with the supply amount, the backward movement of the sub-piston 9 is stopped, and by moving the spill ring 20, the sub-piston 9 can be moved back and forth in a stepless manner. Can be done.

Therefore, an actuator 22 related to the engine load is connected to the other end of the lever 21 that engages with the spill ring 20, and the actuator 22 moves the spill ring 20 at two points in proportion to the increase in engine load. By moving backward from the position indicated by the chain line, the compression ratio can be automatically controlled so that it gradually decreases as the engine load increases, gradually increases as the load decreases, and reaches the highest compression ratio in the low load range.
In addition to being related to this load, the compression ratio can also be automatically controlled so as to gradually increase as the engine speed increases, and the actuator 22 can also be related to a knocking sensor provided in the engine, The compression ratio can also be automatically controlled so that it is high when there is no knocking and is lowered accordingly when knocking occurs.

In addition, during the engine's explosion stroke, the secondary piston 9
When the piston receives a large explosive force, this explosive force causes the secondary piston 9 to retreat slightly and close the spill port 19, while the pressure inside the hydraulic chamber 15 momentarily increases and the check valve 16 closes. Since the hydraulic fluid in the hydraulic chamber 15 is confined within the hydraulic chamber 15, the sub-piston receives a large explosive force against the sub-piston without retreating.
In this case, the outflow of the hydraulic oil until the spill port 19 closes and the subsequent rise in pressure of the hydraulic oil absorbs and alleviates the impact on the sub-piston 9 due to explosive combustion of the air-fuel mixture within the combustion chamber 5. .

When the load is low, the spill ring 20
is located at the position closest to the combustion chamber 5, as shown by the two-dot chain line, and as a result, the sub-piston 9 moves forward and the regulating step 1 provided on the sub-piston 9 moves forward.
1, when the forward movement of the sub-piston 9 is stopped, the spherical tip top surface 12 of the sub-piston 9 approximately touches the spherical inner wall surface 13 of the combustion chamber 5, as shown in FIG. As a result, the shape of the combustion chamber 5 can be maintained in a nearly perfect spherical shape at low loads, and the flow within the combustion chamber is extremely smooth to every corner. It is possible to avoid deterioration of combustion at times.

Furthermore, by forming the top surface 12 of the sub-piston 9 into a spherical concave shape, when the sub-piston 9 is retracted from the position of the highest compression ratio, the sub-cylinder 7
The internal flow becomes smoother than when the top surface 12 of the sub-piston 9 is made flat or convex, and there is less residual gas accumulation, which prevents an increase in unburned components such as HC in the exhaust gas. be.

The hydraulic oil supplied to the hydraulic chamber 15 may be lubricating oil in an engine, or hydraulic oil in an automobile's power steering mechanism or automatic transmission.

Further, in the above embodiment, a spill ring 20 was used as an embodiment of the spill body, but
As shown in FIGS. 4 and 5, the spill port in the stem 14a is formed into an inclined spill port 19a that is inclined with respect to the axis of the stem 14a, and a gear-type spill ring 20a is rotated around the outer periphery of the stem 14a. and is slidably fitted to support the spill ring 20a with respect to the cylinder head 2 with a bearing (not shown).
A is provided with one relief port 33 that matches the inclined spill port 19a when the stem 14a slides back and forth. By engaging the provided rack rods 34 and reciprocating the rack rods 34 in the longitudinal direction by the actuator 22, the spill link 20a is rotated, and a relief port is opened with respect to the inclined spill port 19a of the stem 14a. 33, the opening/closing position of the spill port 19a can be displaced along the axial direction of the stem 14a (at this time, the stem 14a is not slidable). The mechanism for rotating the spill ring 20a is not limited to the rack and pinion of the embodiment, but other means may also be used), and the slant provided on the stem 14a shaped spill port 19a
and relief port 3 provided in the spill ring 20a.
The positions of 3 and 3 are reversed, that is,
An escape port 33 is provided in the stem 14a, and this escape port 33 is used as a spill port, while
Inclined spill port 19a on spill ring 20a
By providing this, the opening/closing position of the spill port may be displaced in the axial direction of the stem by rotation of the spill ring 20a (in this case, the stem 14a or the spill ring 20
The shape of the port provided in a can be adjusted as needed.
(It can be shaped as shown in the two-dot chain line in the figure).

[Brief explanation of drawings]

The drawings show embodiments of the present invention; 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 the side of FIG. 1, and FIG. FIG. 4 is a cross-sectional view when the compression ratio is maximized in the example, FIG. 4 is a view of another embodiment of a spill port and a spill body, and FIG. 5 is a plan view of FIG. 4. 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 7... Sub cylinder, 9... Sub piston, 10... Spring, 15... Hydraulic chamber, 1
4, 14a... Stem, 19, 19a... Spill port, 20, 20a... Spill body, 11... Regulation step, 13... Inner wall surface of the combustion chamber, 12... Tip top surface of sub-piston.

Claims (1)

[Claims] 1. A sub-cylinder having a spherical inner wall and opening into a combustion chamber is provided in the cylinder head, a sub-piston is slidably inserted into the sub-cylinder, and 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, a spring means is provided on the sub-piston for biasing the sub-piston in the backward direction, and a spring means is provided on the back surface of the sub-piston in the axial direction of the sub-cylinder. By connecting the stems extending to
The tip of the stem projects into the upper chamber of the cylinder head, and the protruding end of the stem is provided with a spill port that allows hydraulic oil in the hydraulic chamber to flow out.
Further, on the outer periphery of the protruding end of the stem, a spill body is provided so that the spill port is closed by the backward movement of the stem and opened by the forward movement of the stem, and the spill port is opened and closed by the spill body. The secondary piston is fitted into the secondary piston so as to be relatively movable so that its position can be displaced in the axial direction of the stem. A regulating means is provided for regulating the forward movement of the sub-piston to a position where the top surface of the tip of the sub-piston substantially coincides with the inner wall surface of the combustion chamber, and the top surface of the tip of the sub-piston is substantially continuous with the inner wall surface of the combustion chamber. A compression ratio variable device for an internal combustion engine, characterized by having a spherical concavity.