JPH0826792B2 - Variable compression ratio device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a compression ratio variable device for an internal combustion engine.

2. Description of the Related Art As a conventional compression ratio varying device for an internal combustion engine of this type, for example, one shown in FIG. 4 is known (see Japanese Utility Model Laid-Open No. 58-25637). In brief, an inner piston 3 is fixed to a piston pin 2 connected to a connecting rod 1, and an outer piston 4 slidable in the axial direction is provided on the outer side of the inner piston 3.
Is arranged. An upper liquid chamber 5 is provided between the outer piston 4 and the upper portion of the inner piston 3, and a lower liquid chamber 5 is provided between the annular portion 7 screwed to the inner periphery of the lower portion of the outer piston 4 and the inner piston 3. The chambers 8 are respectively formed, and the liquid chambers 5 and 8 are arranged in the middle of the hydraulic circuit 9 and the hydraulic pressure switching valve 10 is provided.
Also, pressure oil is supplied through the check valves 11 and 12 biased in the closing direction by the springs 11a and 12a, and the outer piston 4 is moved up and down in accordance with the mutual change in volume. Further, the hydraulic pressure switching valve 10 is controlled by the sensors 13, 13 that detect the operating conditions of the engine, the control circuit 15 that issues a command to the pressurizing means 14 from the signal thereof, and the like.

When the compression ratio is increased when the engine has a low load or at a low speed, the pressure of the pressure means 14 is increased so that the pressure oil in the oil pan 16 reaches the oil passages 9a → 9b → 9c, where the spring The check valve 11 is pushed up against the pressure of 11a and flows into the upper liquid chamber 5, while the pressure oil is transferred through the oil passage 9b to the switching valve 10
Is pressed rightward against the spring 10a. Therefore, the oil passage 9b is closed, and the pressure oil in the lower liquid chamber 8 flows out to the outside through the oil passages 9e and 9f. Therefore, as the amount of pressure oil in the upper liquid chamber 5 increases, the outer piston 4 moves. It is lifted up and the compression ratio is increased.

On the other hand, when the compression ratio is reduced under high engine load or high engine speed, the pressure of the pressurizing means 14 is weakened to reduce the oil passages 9b, 9c.
The check valve 11 closes the oil passage 9c by the urging force of the spring 11a, the switching valve 10 moves leftward to close the oil passage 9f, and the oil passages 9d and 9e are connected. Therefore, almost all of the pressure oil in the upper liquid chamber 5 flows into the lower liquid chamber 8 without backflow by the check valve 12, and the outer piston 4 is lowered to obtain the low compression ratio state.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-mentioned conventional compression ratio variable device, in the low compression ratio state as described above, the oil passage 9c is closed by the check valve 11, and the oil passage 9d is also closed. Since it is closed by the check valve 12, the inflow and outflow of the pressure oil in the upper liquid chamber 5 is completely blocked, and therefore the pressure oil remaining in the upper liquid chamber 5 is exposed to the combustion heat when the engine is rotating. Not only is it deteriorated, but it also becomes tar and sticks or adheres to the upper surface of the inner piston 3 and the lower surface of the crown of the outer piston 4. As a result, it becomes difficult for the outer piston 4 to slide,
There is a problem that a smooth compression ratio variable control action cannot be obtained.

Means for Solving the Problems The present invention has been devised in view of the problems of the above-mentioned conventional compression ratio variable device, and includes an outer piston slidably fitted on the outer circumference of an inner piston, and the outer piston. And an inner piston, an upper liquid chamber, pressurizing means for supplying pressurized oil to the upper liquid chamber according to the operating state of the engine, and the pressurizing means and the upper liquid chamber communicating with each other. A plurality of supply passages each having a check valve therein, a discharge passage communicating between the upper liquid chamber and the outside, and a discharge passage formed between the lower surface of the crown of the outer piston and the upper surface of the inner piston. A passage groove that connects the supply passage and the discharge passage,
Further, it is characterized in that at least one supply passage of the plurality of supply passages is formed at a position where the pressurizing means and the upper liquid chamber always communicate with each other.

Effect According to the present invention having the above-described configuration, in order to obtain a high compression ratio or a low compression ratio depending on the operating state of the engine, the pressure oil is supplied from the pressurizing means to the upper liquid chamber via the plurality of supply passages. By the pressure oil discharged from the upper liquid chamber through the discharge passage, the outer piston slides vertically with respect to the inner piston. Then, in the low compression ratio state in which the pressure oil in the upper liquid chamber is discharged, the pressure oil always flows into the passage groove from the supply passage that is in communication and is discharged to the outside from the discharge passage. It is effectively cooled and deterioration of the pressure oil is prevented.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which 21 is an outer piston which forms the outer shell of the piston, and an annular portion 22 is screwed on the inner circumference of the lower portion, and 23 is connected to a connecting rod 24. This piston pin 23
The inside is provided with a cylindrical hydraulic fluid chamber 25 having a small diameter on the right side in the drawing, and a spool valve 26, which will be described later, which slides left and right in the hydraulic fluid chamber 25, and at both ends thereof. The annular stoppers 27, 28 having through holes 27a, 28a in the center are fixed. In addition, 29 in the figure indicates that the boss 30, 30 is attached to the piston pin 23.
The inner piston is fixed via 0, and the outer piston 21 is arranged on the outer side of the inner piston 29 so as to be slidable in the axial direction while slidingly contacting the inner and outer peripheral surfaces 21a and 29a thereof. Further, with the upward movement of the outer piston 21, while the upper liquid chamber 31 is formed between the lower surface 21b of the crown portion of the outer piston 21 and the upper surface 29b of the inner piston 29,
An annular lower liquid chamber 32 is formed between the side surface of the outer piston 21 with the downward movement and the upper surface of the annular portion 22 for restricting the maximum upward movement of the outer piston 21 and the lower surface of the inner piston 29. The pressure oil is supplied to and discharged from each of the liquid chambers 31 and 32 through the hydraulic circuit 33 to change the volume, and the outer piston 21 is moved up and down.

The hydraulic circuit 33 is formed in the inner axial direction of the connecting rod 24 and communicates with the hydraulic fluid chamber 25.
And is formed to penetrate through the piston pin 23 and the inner piston 29 in the up-down direction to transfer the pressure oil from the hydraulic fluid chamber 25 to the upper fluid chamber 31.
And a first oil passage 35, which is a supply passage for supplying to
The hydraulic fluid chamber is formed so as to penetrate from 35 to the left side position in the figure in substantially parallel.
A second oil passage 36 for supplying pressure oil from 25 to the upper liquid chamber 31 regardless of the movement of the spool valve 26;
A third oil passage 37, which is formed to penetrate through the oil passage 36 in a position facing the oil passage 36 and supplies pressure oil from the hydraulic fluid chamber 25 to the lower liquid chamber 32, is formed in parallel with the first oil passage 35 in the vicinity of the right side in the drawing. And a fourth oil passage 38 which is a discharge passage for discharging pressure oil from the upper liquid chamber 31 to the outside through the through hole 28a and the discharge port 21c on the outer piston 21 side.

Furthermore, inside the first oil passage 35 and the second oil passage 36,
Check valves 39 and 40, respectively, which allow the pressure oil to flow only from the hydraulic fluid chamber 25 toward the upper fluid chamber 31, are provided. Further, inside the third oil passage 37, there is also provided a check valve 41 which allows the pressure oil to flow only from the hydraulic fluid chamber 23 toward the lower fluid chamber 32. Each of the check valves 39, 40, 41 is opened and closed mainly by hydraulic pressure in the front and rear direction, a check ball 42a, a ring-shaped passage forming portion 42b having a cutout path, and a comparison that biases the check ball 42a in the closing direction. Return spring 42c with low dynamic spring pressure
….

Furthermore, on the upper surface 29b of the inner piston 29, as shown in FIG. 2, a substantially annular shape that connects the upper end opening 36a of the second oil passage 36 and the upper end opening 38a of the fourth oil passage 38 is communicated. A passage groove 50 is formed. The passage groove 50 is formed so as to widen inward in the vicinity of the upper end openings 36a, 38a of the second oil passage 36 and the fourth oil passage 38, and the fourth oil passage 38 side is
The upper end opening 35a of the first oil passage 35 is wide.

Further, in the spool valve 26, a first slide valve body 26b having a substantially U-shaped cross section is formed at a left end portion of the shaft portion 26a in the drawing, and a first slide valve body 26b is formed at a right end portion of the drawing in comparison with the first slide valve body 26b. A small-diameter columnar second slide valve body 26c is formed, and is urged rightward in the figure by a spring 43 mounted between the first slide valve body 26b and the stopper 27. That is, when a large hydraulic pressure does not act on the hydraulic fluid chamber 25, the spring force of the spring 43 causes the first oil passage 35 to move.
When the large hydraulic pressure is applied to the open position, the spring moves to the left against the spring force of the spring 43 to close the first oil passage 35 and open the third and fourth oil passages 37, 38. It is designed to work. The second oil passage 36 always communicates the hydraulic fluid chamber 25 with the upper fluid chamber 31 regardless of the lateral movement of the spool valve 26. In addition, the annular portion 22 and the inner piston 29
There is no seal member or the like between and, so that the pressure oil supplied into the lower liquid chamber 32 leaks slightly from the sliding portion.

Further, the pressure oil supplied to the main passage 34 is pressure-fed from an oil pan 44 of the engine by a general oil pump 45 as a pressurizing means. Further, the pressure of the pressure oil delivered by the oil pump 45 is controlled by a pressure adjusting valve 47 arranged in the relief passage 46.
Is controlled by a control circuit 48 that receives an output signal from an engine rotation and throttle opening sensor (not shown) or the like to detect an engine operating state.

The operation of this embodiment will be described below. First, in order to obtain a high compression ratio at the time of starting the engine or at a low load, the opening degree of the pressure adjusting valve 47 which receives a signal from the control circuit 48 becomes large, and the low pressure oil is shown in FIG. As shown, it is sent from the main passage 34 to the hydraulic fluid chamber 25, and from there, the first oil passage 35
Then, the oil is supplied to the upper liquid chamber 31 through the second oil passage 36 and the check valves 39 and 40 opened by this hydraulic pressure. At this point, the slide valve bodies 26b and 26c of the spool valve 26 have their respective third and fourth oil passages 3
Since 7, 38 are closed, the volume of the upper liquid chamber 31 is rapidly increased by the large amount of pressure oil supplied from both the first and second oil passages 35, 36, and the outer piston 21 is quickly To a high compression ratio state. Even if compression pressure or combustion pressure is applied to the outer piston 21 during the compression or expansion stroke, the check valves 39 and 40 prevent backflow of the pressure oil, and the outer piston 21 and the inner piston 29 are slightly slid. It just leaks from the moving parts. This is also because when the outer piston 21 rises due to inertial force during the exhaust stroke, the first oil passage
Since it is replenished into the upper liquid chamber 31 from the 35 and the second oil passage 36, the high compression ratio state is maintained. In addition, the upper liquid chamber 31
Needless to say, the load on the oil pump 45 can be small because it is not necessary to operate the spool valve 26 by hydraulic pressure when supplying pressure oil to.

On the other hand, in the case of obtaining a low compression ratio at the time of high load, etc., the opening degree of the pressure adjusting valve 47 which receives a signal from the control circuit 48 becomes small, and the high pressure oil flows from the main passage 34 to the hydraulic fluid chamber 25. Sent
This pressure oil causes the spool valve 26 to move to the left in the drawing as shown in FIG. 1 to open the third and fourth oil passages 37 and 38, and at the same time close the first oil passage 35. Therefore the outer piston
When 21 receives the combustion pressure, the pressure oil in the upper liquid chamber 31 is promptly discharged to the outside from the fourth oil passage 38, and passes through the third oil passage 37 to open the check valve 41 and lower the lower portion. It is supplied into the liquid chamber 32. Therefore, in particular, the volume of the upper liquid chamber 31 is rapidly reduced by the action of discharging the pressure oil from the fourth oil passage 38, the outer piston 21 is lowered, and the low compression ratio state can be secured with good responsiveness.

Further, in this low compression ratio state, the pressure oil in the lower liquid chamber 32 prevents interference between the inner piston 29 and the annular portion 22 due to the upper inertial force of the outer piston 21 during the exhaust stroke.

Further, in this low compression ratio state, the pressure oil in the hydraulic fluid chamber 25 always flows into the passage groove 50 from the second oil passage 36, and is discharged from the fourth oil passage 38 as it is while flowing in the passage groove 50. This allows rapid circulation between the lower surface 21b of the crown portion of the outer piston 21 and the upper surface 29b of the inner piston 29.
Therefore, the piston crown is effectively cooled, and
Deterioration of pressure oil is prevented. During the exhaust stroke, if the outer piston 21 rises slightly, the passage groove 50
Since the pressure oil inside is diffused throughout the upper liquid chamber 31 and spreads to every corner, the cooling effect on the crown portion of the piston is further increased. Next, during the expansion stroke, the pressure oil in the upper liquid chamber 31 is pressed by the lower surface 21b of the crown portion of the outer piston 21, and the passage groove 5
Collected in 0 and discharged from the fourth oil passage 38.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the compression ratio variable device for an internal combustion engine of the present invention, a pressure oil supply passage and a discharge passage are provided between the lower surface of the crown of the outer piston and the upper surface of the inner piston. A passage groove communicating with the passage is formed, and in the low compression ratio state, since the pressure oil can be actively circulated to the upper liquid chamber by the passage groove, deterioration of the pressure oil can be prevented and the crown of the piston can be prevented. The part can be cooled effectively.

Moreover, since oil is constantly supplied to the upper liquid chamber through either of the supply passages regardless of whether the compression ratio is high or low, the oil may be temporarily heated to cause coking or the like. Absent.

Further, knocking can be sufficiently suppressed by such a cooling effect, so that the compression ratio can be made as high as possible, and in combination with the high compression ratio achieved by the variable compression ratio control, engine startability and output can be improved. Can be improved.

Further, according to the present invention, when the high compression ratio is obtained, the oil is supplied to the upper liquid chamber through the plurality of supply passages, so that the transition response to the high compression ratio state becomes extremely good due to the possible increase of the supply amount. It can quickly respond to changes in driving.

Further, since the pressure oil in the upper liquid chamber can be efficiently discharged by the passage groove, the response from a high compression ratio to a low compression ratio becomes extremely good and the weight of the piston crown can be reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention, and FIG.
FIG. 3 is a plan view of an inner piston used in this embodiment, FIG. 3 is a sectional view showing a high compression ratio state of this embodiment, and FIG. 4 is an overall configuration diagram showing a conventional compression ratio varying device. 21 ... Outer piston, 21b ... Crown lower surface, 29 ... Inner piston, 29b ... Upper surface, 31 ... Upper liquid chamber, 35 ... First oil passage (supply passage), 36 ... Second oil passage (Supply passage), 38 ... Fourth oil passage (discharge passage), 39, 40 ... Check valve, 45 ... Oil pump (pressurizing means), 50 ... Passage groove.

Front page continued (72) Inventor Takehisa Kondo 1370 Atsugi, Atsugi City, Kanagawa Prefecture, Atsugi Automotive Parts Co., Ltd. Seki Seiji Atsugi City, Kanagawa Prefecture, 1370 Onna, Atsugi Motor Parts Co., Ltd. (56) References JP-A-63-186926 (JP, A) JP-B-48-8047 (JP, B1)

Claims (1)

[Claims] 1. An outer piston slidably fitted on the outer periphery of an inner piston, an upper liquid chamber formed between the outer piston and the inner piston, and the upper liquid chamber adapted to the operating condition of the engine. And a plurality of supply passages each having a check valve therein and the upper liquid chamber and the outside. A discharge passage, and a passage groove formed between the lower surface of the crown of the outer piston and the upper surface of the inner piston to connect the supply passage and the discharge passage, and at least one of the plurality of supply passages. A compression ratio variable device for an internal combustion engine, characterized in that one supply passage is formed at a position where the pressurizing means and the upper liquid chamber are always in communication with each other.