JPS6361498B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a variable compression ratio system that changes the compression ratio in an internal combustion engine according to either or both of the load and rotational speed of the internal combustion engine. This relates to an internal combustion engine of the type.

[Conventional technology]

In order to improve output and reduce fuel consumption in an internal combustion engine, it is sufficient to increase the compression ratio, but if the compression ratio is increased, knocking will occur in a high load range, a low rotation range, or a high load/low rotation range.

For this reason, the compression ratio in a conventional internal combustion engine with a constant compression ratio is
Since it must be set to a low value to prevent knocking in the low rotation range, it cannot be used in other operating ranges, that is, low load or high rotation range or low load/low rotation range.
In a high rotation range, sufficient output cannot be produced and fuel consumption cannot be sufficiently reduced.

Therefore, Japanese Patent Application Laid-Open No. 1988-88926, which is a prior art, proposes to set the compression ratio high in the low rotation/low load range, lower in the low rotation/high load range, and increase it in the high rotation range. ing.

When changing the compression ratio by moving the sub-piston inserted into the sub-cylinder communicating with the combustion chamber back and forth, the tip of the rod protruding from the sub-piston to the outside of the sub-cylinder is
This contacts a plunger in a hydraulic cylinder installed on the same axis as this, and the intake negative pressure in the internal combustion engine is
In a low load range greater than a certain value and at high rotation speed greater than a certain value, hydraulic oil is sent to the hydraulic cylinder to advance the sub-piston to increase the compression ratio;
In a high load range where the intake negative pressure is smaller than a certain value, and
When the rotation speed is lower than a certain value, the hydraulic oil in the hydraulic cylinder is released and the sub-piston is moved back to lower the compression ratio.

[Problem that the invention seeks to solve]

However, the compression ratio changing control according to the prior art is an ON-OFF type control in which the compression ratio suddenly changes from high to low or from low to high after a certain load value and rotation speed. Moreover, it is not possible to smoothly control the compression ratio in proportion to the rotation speed, and when the compression ratio suddenly changes, engine torque fluctuation becomes large and drivability deteriorates.

Moreover, 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 install a hydraulic cylinder for variable compression ratio for each cylinder. As the installation space increases, the internal combustion engine becomes significantly larger, and
The weight also increased.

In addition to solving this problem, the present invention
The purpose is to avoid deterioration of combustion when changing and controlling the compression ratio in an internal combustion engine.

[Means for solving problems]

Therefore, in the present invention, a sub-piston is slidably inserted into a sub-cylinder communicating with a combustion chamber in a cylinder of an internal combustion engine, a hydraulic chamber is formed on the back surface of the sub-piston in the sub-cylinder, and a hydraulic chamber is formed in the hydraulic chamber. While connecting the hydraulic oil supply passage, a stem is provided in the axial direction of the sub-piston so as to protrude from the sub-piston to the outside of the sub-cylinder, and a protruding end of the stem is provided so that the hydraulic oil in the hydraulic chamber flows out. 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 can be displaced in the axial direction of the stem, and the spill body is moved to the internal combustion engine according to either or both of the load and rotation speed of the internal combustion engine. Further, the hydraulic chamber is provided with means for increasing the amount of hydraulic fluid supplied into the hydraulic chamber when the internal combustion engine is decelerated.

[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 supplied hydraulic oil moves the spill port forward toward the combustion chamber, and this forward movement causes the spill port to reach 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. 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. , the auxiliary piston moves backward from the combustion chamber due to the pressure inside the combustion chamber, and this backward movement causes the spill to reach 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 the piston stops when the port closes, the sub-piston can be moved forward or backward by moving the spill body.

Therefore, by relating this spill body to the internal combustion engine so as to move and operate in response to either or both of the load and rotation speed in the internal combustion engine, the compression ratio change control can be performed in accordance with the load and rotation speed in the internal combustion engine. It is possible to perform stepless smoothness according to changes in either or both of the rotational speeds.

According to the present invention, the compression ratio can be smoothly and steplessly automatically controlled in accordance with either or both of the load and rotation speed of the internal combustion engine. While it is possible to reliably reduce the deterioration of drivability due to control, by moving the sub piston back and forth by supplying and discharging hydraulic oil to the hydraulic chamber on the back of the sub piston, it is possible to reduce the deterioration of drivability due to the control. There is no need to provide a hydraulic cylinder for variable compression ratio outside the cylinder, and the structure can be simplified, and the internal combustion engine can be made smaller and lighter.

In this device, if the responsiveness of the control to change the compression ratio to a high level is delayed when the internal combustion engine is decelerated, during this delay period, the auxiliary piston in the auxiliary cylinder is in the retracted position from the combustion chamber, and the ignition is delayed. Since the flame propagation distance from the stopper to the back of the sub-cylinder becomes long, the pressure inside the combustion chamber increases toward the vacuum side when the internal combustion engine decelerates, which worsens combustion even further. As a result, the amount of unburned harmful gas components in the exhaust gas increases.

In order to solve this problem, it is thought that the forward movement of the auxiliary piston is achieved by supplying hydraulic oil to the hydraulic chamber, thereby increasing the amount of hydraulic oil supplied to the hydraulic chamber. However, since the backward movement of the sub-piston is achieved by causing the hydraulic oil in the hydraulic chamber to flow out from the spill port, increasing the amount of hydraulic oil supplied to the hydraulic chamber will cause the sub-piston to move backward, i.e. This will cause a delay in controlling the change to a low compression ratio.

Therefore, as described above, the present invention has a structure in which a means for increasing the amount of hydraulic oil supplied into the hydraulic chamber when the internal combustion engine is decelerated is provided in the passage for supplying hydraulic oil to the hydraulic chamber. As a result, the amount of hydraulic oil supplied to the hydraulic chamber can be increased only when the internal combustion engine is decelerating, which reduces the responsiveness of controlling the sub piston to move backward, that is, change the compression ratio to a low one. This allows the auxiliary piston to quickly move forward when the internal combustion engine is decelerating.

Therefore, according to the present invention, the compression ratio can be quickly controlled to change to a high compression ratio during deceleration of the internal combustion engine without reducing the responsiveness of the control to change the compression ratio to a low one. Deterioration of combustion due to delay in changing control to high compression ratio,
This has the effect of reliably preventing deterioration of exhaust gas.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, 1 is a cylinder block, 2 is a cylinder head, 3 is a piston that reciprocates within the cylinder bore 4 of the cylinder block 1, and 5 is a piston that recesses the lower surface of the cylinder 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 designates a sub-cylinder bored in the cylinder head 2. The sub-cylinder 7 opens at its lower side into the combustion chamber 5 and at its upper side into the upper chamber of the cylinder head 2. The sub-cylinder 7 opens into the upper chamber of the cylinder head of the sub-cylinder 7. A cover plate 8 is provided at the opening to close the opening.

Reference numeral 9 denotes a sub-piston that is slidably inserted into the sub-cylinder 7. A piston ring 9' is provided on the outer periphery of the sub-piston 9, and when the sub-piston 9 moves forward in the direction of the combustion chamber 5, combustion occurs. The volume of the chamber 5 decreases and the compression ratio increases, and when the sub piston 9 retreats in the direction away from the combustion chamber 5, the volume of the combustion chamber 5 increases and the compression ratio decreases. The sub-piston 9 is urged in the backward direction by a spring 10, and 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 (the surface on the back side with respect to the combustion chamber 5). , the stem 11 slidably penetrates the lid plate 8 and protrudes outward, while a hydraulic chamber 12 is formed between the back surface of the sub-piston 9 and the lid plate 8; , hydraulic oil from a hydraulic source is continuously supplied through a port 14 with a check valve 13.

Further, the stem 11 is provided with a passage 15 communicating with the hydraulic chamber 12, and a portion of the stem 11 protruding outward from the cover plate 8 is provided with a passage 15 communicating with the hydraulic chamber 12.
A spill port 16 is bored to allow the hydraulic oil in the cylinder head 2 to flow out into the upper chamber of the cylinder head.

Reference numeral 17 indicates a spill ring, which is an embodiment of the spill body, and the spill ring 17 is slidably fitted onto the stem 11, and the spill ring 17 is advanced in the direction of the combustion chamber 5. When moving, the spill port 16 is closed by the spill ring 17, and when the spill ring 17 is moved backward in a direction away from the combustion chamber 5, the spill port 16 opens more than the spill ring 17.

Further, reference numeral 18 denotes a lever provided in the upper chamber of the cylinder head with its midway portion pivotally and slidably connected to the shaft 19, and one end of the lever 18 is connected to the spill ring 17.
while the other end is connected to a diaphragm mechanism 20, which is one embodiment of an actuator.

This diaphragm mechanism 20 includes the lever 18
A diaphragm 22 is built in and connected to the other end via a rod 21, and a diaphragm chamber 23 partitioned by the diaphragm 22 has a direction in which the other end of the lever 18 is pushed down in the figure, that is, a spill ring 17. A spring 24 is provided to bias the diaphragm chamber 23 in the direction of backward sliding.
is connected to an intake manifold (not shown) in an internal combustion engine via a negative pressure transmission passage 25 to introduce intake negative pressure into the diaphragm chamber 23.
When the intake negative pressure becomes higher than vacuum as the load on the internal combustion engine decreases, the spill ring 17 is configured to slide forward in proportion to this.

In the hydraulic fluid supply passage 26 to the port 14 with a check valve for the hydraulic chamber 12, a constant opening is maintained when the solenoid 27 is de-energized, and when the solenoid 27 is energized, the opening is increased. While the control valve 28 is provided to open more widely from the
When the internal combustion engine is decelerating, a switch 30 in the power circuit 29 to the solenoid 27 of the control valve 28 is connected to the negative pressure transmission passage 25 for an appropriate period of time.
A deceleration sensing mechanism 31 that is turned on is provided.

This deceleration sensing mechanism 31 includes two diaphragm chambers 34 and 35 defined by a diaphragm 33 with a rod 32.
A spring 36 is provided to resist the movement of the rod 32 in the protruding direction, and the rod 32 is connected to the switch 30 when the rod 32 is retracted.
On the other hand, the diaphragms 34 and 35 are connected to the negative pressure transmission passage 25 through passages 37 and 38, respectively, and one spring 36
When the intake negative pressure suddenly changes in the passage 37 from the inlet diaphragm chamber 34, both diaphragm chambers 34,
A restrictor orifice 39 is provided so that a pressure difference occurs only during a certain period of time.

In this configuration, when the spill ring 17 is moved in the forward direction from the position shown by the solid line in FIG. Since the pressure in the hydraulic chamber 12, which is constantly supplied with hydraulic oil from the port 14 with the stop check valve 13, increases, the secondary piston 9 moves forward toward the combustion chamber 5, and this forward movement causes the spill port 16 to open. When the hydraulic oil advances to this point, the hydraulic oil starts to flow out from the spill port 16, and when the amount of this outflow and the amount of supply to the hydraulic chamber 12 are balanced, the advance of the sub-piston 9 is stopped.

Furthermore, when the spill ring 17 is moved in the backward direction from the position shown by the two-dot chain line to the position shown by the solid line, the spill port 16 is fully opened, the amount of flow from the spill port increases, and the pressure in the hydraulic chamber 12 decreases. The auxiliary piston 9 is connected to the pressure in the combustion chamber 5 and the spring 1
Combustion chamber 5 by either one or both of 0
When this backward movement progresses to the point where the spill port 16 is closed by the spill ring 17, the amount of fluid flowing out from the spill port 16 decreases, and the amount of fluid flowing out from the spill port 16 decreases. When the supply amount is balanced with the supply amount, the backward movement of the sub-piston 9 will stop, and by moving the spill ring 17, the position of the sub-piston 9 can be changed arbitrarily, and the compression ratio can be changed arbitrarily. be.

In this case, since the spill ring 17 is connected to the diaphragm mechanism 20, which is an example of an actuator, through the lever 18, when the intake negative pressure gradually becomes larger than the vacuum as the load of the internal combustion engine decreases, the spill ring 17 As the engine moves forward, the compression ratio gradually increases as the load on the internal combustion engine decreases, and when the intake negative pressure becomes lower than atmospheric pressure as the load on the internal combustion engine increases, the spill ring 17 retreats. The compression ratio can be controlled to change steplessly and smoothly in accordance with the load on the internal combustion engine, such that the compression ratio gradually decreases as the load on the internal combustion engine increases.

It should be noted that the actuator for moving the spill ring 17 is not limited to the diaphragm type, and other types of actuators such as an electric type may be used, but this actuator may be used in an internal combustion engine. In relation to the rotation speed or rotation speed and load, the compression ratio can be changed and controlled so that it becomes gradually higher as the rotation speed increases, or the compression ratio can be lowered as the load increases and increased as the rotation speed increases. It is also possible to control the changes as follows.

During acceleration when the throttle valve is rapidly opened from a certain opening degree, the intake negative pressure rapidly decreases from a large value close to vacuum to less than atmospheric pressure. , a pressure difference is generated for the time set by the restrictor orifice 39, but this pressure difference causes the rod 32 to protrude, so the switch 30 remains OFF and the control valve 28 does not operate.
However, during deceleration when the throttle valve is suddenly closed from a certain opening degree, the intake negative pressure suddenly increases toward the vacuum side, so that the rod 32 moves back between the two diaphragm chambers 34 and 35 in the deceleration sensing mechanism 31. When a pressure difference occurs, the rod 32 turns on the switch 30 until the pressures of both diaphragms 34 and 35 reach equilibrium, and the control valve 28 opens and operates, increasing the amount of hydraulic oil supplied to the hydraulic chamber 12. do.

In this way, when the internal combustion engine is decelerated, the amount of hydraulic fluid supplied to the hydraulic chamber 12 increases,
Since the forward movement of the auxiliary piston 9 by the hydraulic oil applied to the hydraulic pressure 12 can be performed quickly without any time delay, problems caused by a delay in the forward movement of the auxiliary piston during deceleration of the internal combustion engine, that is, the combustion condition becomes worse. This can definitely be prevented.

In this case, the control valve may be directly connected to the deceleration sensing mechanism 31. FIG. 3 is a diagram showing an embodiment in this case. Rod 32
The passage area of the control valve 28a is increased during deceleration of the internal combustion engine.

In addition, when the secondary piston 9 receives a large explosive force during the explosion stroke in an internal combustion engine, 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 decreases. , the check valve 13 closes, and the hydraulic chamber 1
Since the hydraulic oil in the hydraulic chamber 12 is confined within the hydraulic chamber 12, it bears a large explosive force against the secondary piston. The outflow and the subsequent pressure increase of the hydraulic oil act as a cushion, which absorbs and alleviates the impact on the auxiliary piston 9 caused by the explosive combustion of the air-fuel mixture within the combustion chamber 5.

In the above embodiment, the hydraulic oil constantly supplied to the hydraulic chamber 12 may be lubricating oil in an internal combustion engine, hydraulic oil in a power steering mechanism of an automobile, or hydraulic oil in an automatic transmission of an automobile.

Further, in the above embodiment, a spill ring 17 is used as an embodiment of the spill body, and this is attached to the stem 11.
The stem 11a is formed into a hollow shaft as shown in FIG. The spill port 16a is created by the spill rod 17a by slidably inserting the rod 17a and sliding the spill rod 17a using an actuator related to either or both of the load and rotation speed in the internal combustion engine. The opening/closing position of the spill port may be configured to be displaced along the axial direction of the stem 11a.Furthermore, in each of the above embodiments, the displacement of the opening/closing position of the spill port due to the relative movement of the spill body with respect to the stem is In the previous case, this was done by sliding the spill body in the axial direction with respect to the stem, but the displacement of the opening/closing position of the spill port due to the relative movement of the spill body with respect to the stem is performed as follows instead of sliding in the axial direction with respect to the stem. As described above, this can also be done by rotating the spill body.

That is, FIG. 5 and FIG. 6 show an embodiment in this case, and as one embodiment of the spill body, a spill ring 17b having a gear 41 on the outer periphery is used.
is rotatably and slidably fitted to the stem 11b, while forming a spill port in the stem 11b into an inclined spill port 16b that is inclined with respect to the axis of the stem 11b,
The gear-type spill ring 17b is pivotally supported on the cylinder head 2 by a bearing (not shown), and the spill ring 17b has a hole that matches the inclined spill port 16b when the stem 11b slides back and forth. At the same time, a gear 41 on the outer periphery of this spill ring 17b is engaged with a rack rod 42 arranged perpendicularly to the stem 11b, and the rack rod 42 is connected to the gear 41 on the outer periphery of the spill ring 17b. An actuator 43 associated with one or both of them slides in the longitudinal direction to rotate the spill ring 17b, and shifts the relief port 40 to or from the inclined spill port 16b of the stem 11b. By doing so, the opening/closing position of the spill port 16b by the spill ring 17b is configured to be displaced in the axial direction of the stem 11b (in this case, the stem 11b is held slidably but not rotatably). , Also, the spill ring 17 here
The mechanism for rotating b is not limited to the rack rod and gears of the embodiment, but other means may be used, and the stem 11b is provided with a relief port 40 and the spill ring 17b is provided with an inclined spill port 16b. Furthermore, the ports 16b and 40 provided in the stem 11b and the spill ring 17b may be
As for the shape, a combination of arbitrary shapes as shown by the two-dot chain line in FIG. 5 can be considered as necessary).

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional front view of the main parts of the internal combustion engine, FIG. 2 is a cross-sectional view of FIG. 1, FIG. 3 is another example of the control valve, and FIG. 4 and Fig. 5 is another example of the spill body and spill port, Fig. 6
The figure is a plan view of FIG. 5. 1... Cylinder block, 2... Cylinder head, 5... Combustion chamber, 6... Spark plug, 7... Sub cylinder, 9... Sub piston, 12... Hydraulic chamber, 1
1, 11a, 11b... stem, 16, 16a,
16b... Spill port, 17, 17a, 17b
... Spill body, 28, 28a ... Control valve, 31...
...Deceleration sensing mechanism.

Claims (1)

[Claims] 1. A sub-piston is slidably inserted into a sub-cylinder communicating with a combustion chamber in a cylinder of an internal combustion engine, a hydraulic chamber is formed on the back surface of the sub-piston in the sub-cylinder, 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 protrude from the sub-piston to the outside of the sub-cylinder, and a spill port is provided at the protruding end of the stem to allow the hydraulic oil in the hydraulic chamber to flow out. A spill body is provided at the protruding end of the stem, and the spill port is closed by the backward movement of the stem, and the spill port is opened by the forward movement of the stem. The spill body is provided so as to be relatively movable so that its position can be displaced in the axial direction of the stem, and the spill body is connected to the internal combustion engine so as to be moved and operated in response to either or both of the load and rotation speed of the internal combustion engine. The variable compression ratio internal combustion engine is further characterized in that the hydraulic chamber is provided with means for increasing the amount of hydraulic fluid supplied into the hydraulic chamber during deceleration of the internal combustion engine.