JP2517728B2 - Variable compression ratio device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the responsiveness in switching to a low compression ratio state by supplying the pressurized oil into the upper and lower liquid chambers formed between an outer piston and an inner piston through a check valve opened and closed by the hydraulic pressure before and behind the liquid chambers and discharging the pressurized oil in the upper liquid chamber outside when switching to the low compression ratio state is performed. CONSTITUTION:An inner piston 29 connected with a connecting rod 24 through a piston pin 23 is inserted in free sliding into an outer piston 21 having an annular part 22 screwed onto the lower part inner periphery, and the upper and lower liquid chambers 31 and 32 are formed in the upper and lower parts between the both. A working liquid chamber 25 is formed inside the piston pin 23, and the pressurized oil in the working liquid chamber 25 is supplied into an upper part liquid chamber 31 through a check valve 41, and the pressurized oil in the liquid chamber 31 can be discharged outside from a discharge part 27a through an opening/ closing valve 26 operated according to the variation of the oil pressure in the liquid chamber 31. Further, the upper liquid chamber 31 is allowed to communicate to the lower liquid chamber 31 through a check valve 42, and the pressurized oil in the liquid chamber 31 can be discharged outside through the oil passages 38a and 38b which are opened and closed by the opening/closing valve 26.

Description

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

As is well known in the prior art, increasing the compression ratio in the cylinder of an internal combustion engine improves thermal efficiency and is an effective means for improving engine startability, output, fuel consumption, and exhaust emission. However, if the compression ratio is increased to a high rate regardless of the operating conditions, for example, in a gasoline engine, knocking or the like is likely to occur when the load is high. On the other hand, in a diesel engine, the friction becomes large especially in the high load range, and the output decreases due to mechanical loss.

Therefore, for example, as shown in FIG. 6, there is provided a device that makes the compression ratio variable according to the operating state of the engine (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 an axial direction is arranged outside the inner piston 3. There is. An upper liquid chamber 5 is provided between the outer piston 4 and the upper portion of the inner piston 3, and an annular portion 7 and an inner piston 3 screwed to the inner circumference of the lower portion of the outer piston 4.
Lower liquid chambers 8 are formed between the respective liquid chambers.
The pressure oil is supplied to the valves 5 and 8 via the oil pressure switching valve 10 and the check valves 11 and 12 which are urged in the closing direction by the springs 11a and 12a, which are arranged in the middle of the hydraulic circuit 9, so that their mutual volumes are increased. The outer piston 4 is moved up and down according to the change. 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 device 14 from the signal thereof, and the like.

When increasing the compression ratio at low engine load or low engine speed, the pressure of the pressure device 14 is increased so that the pressure oil in the oil pan 16 reaches the oil passages 9a → 9b → 9c. 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
Against the spring 10a and hydraulically move it to the right to the position shown in FIG. Therefore, the oil passage 9d 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 lowered at the time of high engine load or high engine speed, the pressure of the pressure device 14 is weakened and the oil passages 9b, 9c are reduced.
The check valve 11 closes the oil passage 9c by the urging force of the spring 11a, the switching valve 10 moves leftward as shown in FIG. 7 to close the oil passage 9f, and closes the oil passage 9d. , 9e are connected. Therefore, almost all 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 maintain 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, since the pressurizing force of the pressurizing device 14 is increased against the spring 11a pressure at the time of low engine speed, However, it is impossible to use a general lubricating oil pump whose pressure increases as the engine speed increases. Therefore, there is a problem that a different pressurizing device having high pressurizing performance must be used or the pressurizing performance of the oil pump must be improved.

Further, when switching from the high compression ratio state to the low compression ratio state, as described above, substantially all of the pressure oil in the upper liquid chamber 5 is supplied to the oil passage.
The pressure oil in the lower liquid chamber 8 is returned to the inside of the lower liquid chamber 8 via 9d and 9e, and the leakage of the pressure oil in the lower liquid chamber 8 is blocked by the seal member 6, so that the responsiveness of the switching control is poor. Because the cross-sectional area of the lower liquid chamber 8 is smaller than the cross-sectional area of the upper liquid chamber 5, the volume of the lower liquid chamber 8 that increases increases more than the volume of the upper liquid chamber 5 that decreases due to the downward movement of the outer piston 4. Is small. Therefore, even if the pressure oil tries to flow from the upper liquid chamber 5 to the lower liquid chamber 8 when the outer piston 4 moves downward, leakage from the lower liquid chamber 8 to the outside is blocked by the seal member 6 and cannot flow into the outside. The response of the switching control from the compression ratio state to the low compression ratio state deteriorates.

Moreover, at this low compression ratio, the oil passage 9c is closed by the check valve 11c.
Since it is blocked by the pressure of the spring 11a, pressure oil remains in the upper liquid chamber 5, which is not only deteriorated by being exposed to high heat such as combustion heat at high rotation, but also tars and sticks to the upper surface of the inner piston 3 etc. However, there are various problems that a smooth compression ratio control action cannot be obtained.

Means for Solving the Problems The present invention has been devised in view of the above-mentioned conventional problems, and an inner piston supported on both ends of a piston pin and an outer periphery of the inner piston are slidable in the axial direction. An outer piston that is fitted as much as possible, and an upper liquid chamber and a lower liquid chamber that are formed between the outer piston and the inner piston,
The hydraulic fluid chamber, which is formed at a predetermined position inside the piston pin or the inner piston, and into which pressure oil is introduced from the outside, and the check valve that opens and closes the pressure fluid in the hydraulic fluid chamber by the front and rear hydraulic pressures, A first oil passage for supplying to the liquid chamber, a second oil passage for discharging the pressure oil of the upper liquid chamber to the outside through a discharge port, and a second oil passage communicating with the second oil passage, and a pressure of the upper liquid chamber. A third oil passage for supplying oil to the lower liquid chamber through a check valve that opens and closes by hydraulic pressure between the front and rear, a fourth oil passage for discharging pressure oil in the lower liquid chamber, and a slide on the hydraulic fluid chamber. Stored as much as possible,
It is characterized by comprising an opening / closing valve for opening / closing the discharge port and the fourth oil passage according to a change in the hydraulic pressure in the upper liquid chamber based on the combustion pressure of the engine.

According to the present invention having the above-described structure, first, when a high compression ratio is obtained at the time of low engine load or low engine speed, the pressure oil having a relatively low pressure is introduced into the hydraulic fluid chamber by the predetermined pressurizing means. From here, it is supplied to the upper liquid chamber through the first oil passage and the check valve opened by the pressure oil. At this point in time, the on-off valve closes the discharge port, so the volume of the upper liquid chamber rapidly increases, and with this, the outer piston rises and enters a high compression ratio state.

On the other hand, when the engine has a high load, a high combustion pressure due to the high load acts on the crown surface of the outer piston, so that the hydraulic pressure in the upper liquid chamber rises. This hydraulic pressure is transmitted from the second oil passage, the on-off valve instantaneously moves in one direction, opens the discharge port, and closes the fourth oil passage. Therefore, a part of the pressure oil in the upper liquid chamber is quickly discharged to the outside from the second oil passage through the discharge port, and at the same time, other pressure oil opens the check valve from the second oil passage to open the lower liquid chamber. Will be promptly supplied to. Therefore, switching control of the compression ratio is performed with good responsiveness.

Further, in this low compression ratio state, when the outer piston slightly rises due to inertial force during the exhaust stroke, the pressure oil is supplied to the upper liquid chamber through the first oil passage and is discharged from the discharge port through the second oil passage. Since it is discharged and circulates in the upper liquid chamber,
The piston crown is cooled, and the pressure oil is prevented from being deteriorated.

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

1 and 2 show a first embodiment of the present invention, in which reference numeral 21 forms an outer shell of a piston, and an annular portion is formed on the inner circumference of the lower portion.
22 is an outer piston threadedly attached, 23 is a piston pin connected to a connecting rod 24, and this piston pin 23 has a cylindrical working fluid chamber 25 formed inside and a left end portion in the figure. An annular stopper 27 having a discharge port 27a in the center is fixed to it, while a substantially disk-shaped closing plate 28 for sealing one end of the working fluid chamber 25 is fitted and fixed to the right end. Further, the working fluid chamber 25 has a substantially disk-shaped partition wall 50 disposed inside the left side in the figure perpendicularly to the axial direction, and is relatively small on the left side in the figure defined by the partition wall 50. A pressure chamber 51 having a volume is formed, and an opening / closing valve 26 having a substantially U-shaped cross section is provided in the pressure chamber 51 so as to be slidable in the left-right direction. Further, reference numeral 29 in the drawing denotes an inner piston fixed to the piston pin 23 through boss portions 30, 30 as shown in FIG. 2, and the outer piston 21 is provided outside the inner piston 29. The inner and outer peripheral surfaces 21a and 29a are slidably arranged and slidable in the axial direction. Further, as the outer piston 21 moves upward relative to the inner piston 29, an upper liquid chamber 31 is formed between the crown lower surface 21b of the outer piston 21 and the upper surface 29b of the inner piston 29, while An annular lower liquid chamber 32 is formed between the upper surface of the annular portion 22 and the lower surface of the inner piston 29 that regulates the maximum upward movement of the outer piston 21 with the movement. Pressure oil is supplied to and discharged from the hydraulic circuit 32 through the hydraulic circuit 33 to change the volume, and the outer piston 21 is moved vertically with respect to the inner piston 29.

The hydraulic circuit 33 is formed in the inner axial direction of the connecting rod 24 and is formed so as to penetrate the main passage 34 communicating with the right chamber 52 of the hydraulic fluid chamber 25 and the piston pin 23 and the inner piston 29 in the vertical direction. A first oil passage 35 for supplying pressure oil from the hydraulic fluid chamber 25 to the upper liquid chamber 31, and a first oil passage 35 penetratingly formed substantially parallel to the left side position of the first oil passage 35 in the drawing. 51, the outlet 27a, and the opening 21c on the side of the outer piston 21
A second oil passage 36 for discharging pressure oil to the outside via the
A third oil passage 37 that connects the oil passage 36 and the lower liquid chamber 32 to each other through the pressure chamber 51, and supplies the pressure oil of the upper liquid chamber 31 to the lower liquid chamber 32.
And two fourth oil passages 38a, 38b which are formed substantially parallel to the boss portion 30 along the vertical direction and discharge the pressure oil in the lower liquid chamber 32 to the outside via the hydraulic fluid chamber 25. Has been done. Further, each of the first oil passage 35 and the third oil passage 37 has a check valve composed of check balls 39, 39 which are opened and closed by front and rear hydraulic pressure, and annular passage constituting portions 40, 40 having cutout passages. 41,
42 are provided.

Further, the on-off valve 26 has the discharge port 27a on the left end face in the figure.
A convex first valve body 26a for opening and closing is formed on the outer peripheral surface, and a protruding annular second valve body 26b for opening and closing the fourth oil passage 38a is integrally formed on the outer peripheral surface. 2 The first valve body 2 facing the opening edge 36a of the oil passage 36, that is, the pressure chamber 51
The stepped outer peripheral surface between the 6a and the second valve body 26b is the second oil passage 36.
It is a pressure receiving portion 53 to which the hydraulic pressure from the upper liquid chamber 31 is transmitted via. Further, the opening / closing valve 26 is the first valve body 26a.
Spring mounted between the inner end surface of the base of the and the partition wall 50
It is urged to the left in the figure by 43. That is, when the large hydraulic pressure does not act on the pressure portion 51, the spring 43
When the outlet 27a is closed by the pressure and a large hydraulic pressure acts, it moves to the right against the pressure of the spring 43 to open the outlet 27a, and at the same time, the switching operation is performed to close the fourth oil passage 38a. ing. In the figure, 54 is the annular portion 22.
Is a seal ring provided between the outer periphery of the inner piston 29 and the inner piston 29 and prevents the pressure oil in the lower liquid chamber 32 from leaking from the sliding portion to the outside. In the figure, 55 and 55 are stopper rings that support both ends of the piston pin 23, and 56
Is an annular passage groove formed on the upper surface 29b of the inner piston 29 and connecting the first oil passage 35 and the second oil passage 36.

Further, the engine lubricating oil in the oil pan is fed under pressure to the main passage 34 by a general mechanical oil pump (not shown) synchronized with the engine rotation.

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 the time of low load, the pressure oil of a relatively low pressure is set by the oil pump.
As shown in the figure, the check valve is sent from the main passage 34 to the right chamber 52 of the hydraulic fluid chamber 25, and from there, the first oil passage 35 and the check valve opened by this hydraulic pressure.
It is supplied to the upper liquid chamber 31 via 41. At this point, the first and second valve bodies 26a and 26b of the opening / closing valve 26 close the discharge port 27a and open the fourth oil passages 38a and 38b, so that the volume of the upper liquid chamber 31 is quickly increased. At the same time, the pressure oil in the lower liquid chamber 32 is quickly discharged. Along with this, the outer piston 21
Is relatively elevated from the inner piston 29 and enters a high compression ratio state. It should be noted that even if the compression pressure or the combustion pressure acts on the outer piston 21 during the compression or expansion stroke, the check valve 41
The reverse flow of pressure oil is prevented by the outer piston.
It only leaks from the clearance of the sliding portion between 21 and the inner piston 29. This is also because when the outer piston 21 rises due to inertial force during the exhaust stroke, it is replenished from the first oil passage 35 into the upper liquid chamber 31 and the check valve 41 prevents a reverse flow of compression, so that a high compression ratio is achieved. The state is maintained. still,
Needless to say, the load on the oil pump can be small because it is not necessary to operate the on-off valve 26 by hydraulic pressure when supplying pressure oil to the upper liquid chamber 31.

On the other hand, when a low compression ratio is obtained at the time of high load, the high combustion pressure at the time of high load acts on the crown surface of the outer piston 21, so that the pressure in the upper liquid chamber 31 becomes high and this hydraulic pressure becomes the second oil pressure. The pressure in the pressure chamber 51 is increased by being sent from the passage 36 to the pressure chamber 51. Therefore, this hydraulic pressure acts on the pressure receiving portion 53 to open / close the valve.
As shown in FIG. 2, 26 moves rightward in the figure against the spring pressure of the spring 43, opens the discharge port 27a, and simultaneously closes the fourth oil passages 38a, 38b. Therefore, the outer piston 21
When the combustion pressure is received, the pressure oil in the upper liquid chamber 31
The liquid is rapidly discharged to the outside from the discharge port 27a through the oil passage 36 and the pressure chamber 51, and at the same time, the lower liquid is passed through the third oil passage 37 while opening the check valve 42 through the second oil passage 36 and the pressure chamber 51. Chamber 32
Will be promptly supplied. In particular, the volume of the upper liquid chamber 31 is rapidly reduced by the action of the pressure oil discharged from the discharge port 27a, 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. On the other hand, the pressure oil passes through the first oil passage 35 and the upper liquid chamber 31.
Is supplied to the passage groove 56 of the discharge port 27 through the second oil passage 36.
Since it is discharged from a and circulates in the upper liquid chamber 31, the cooling action of the crown portion of the piston is obtained and the deterioration of the pressure oil is prevented.

Here, the on-off valve 26 immediately closes the discharge port 27a by the spring pressure of the spring 43 when the combustion pressure does not act on the crown surface of the outer piston 21, that is, during the engine cycle other than the expansion stroke, and the pressure chamber from the outside. 51 and the second oil passage 36,
Air is prevented from entering the upper liquid chamber 31 and the lower liquid chamber 32 through the third oil passage 37. That is, the upper and lower liquid chambers 31,3
When air is mixed into 2, the vertical movement of the outer piston 21 with respect to the inner piston 29 becomes unstable due to engine cycle fluctuations, making it impossible to stabilize the low compression ratio state. Therefore, by appropriately closing the outlet 27a with the opening / closing valve 26 as described above, it is possible to sufficiently prevent air from entering the hydraulic pressures 31 and 32.

3 to 5 show a second embodiment of the present invention, in which the construction of the on-off valve and the fourth oil passage is different from that of the first embodiment. More specifically, one end of the fourth oil passage 58 is formed in the lower liquid chamber 32, and the other end is formed in the right chamber 52 of the hydraulic liquid chamber 25. Further, on the right side of the first oil passage 35 in the drawing,
A pressure passage 59 for supplying pressure oil from the upper liquid chamber 31 to the right chamber 52 is formed so as to penetrate therethrough. In the middle of each of the pressure passage 59 and the fourth oil passage 58, orifices 57, 57 for adjusting the front and rear hydraulic pressure are provided. On the other hand, in the opening / closing valve 26, a discharge valve 60 and a spool valve 61 are separately arranged in a pressure chamber 51 and a right chamber 52 defined by a partition wall 50. That is, the discharge valve 60 has a generally U-shaped vertical cross section, and the pressure chamber 51
A step-shaped outer periphery facing to is formed as a pressure receiving portion 60a, and a disc-shaped valve body 60b whose outer peripheral edge is chamfered is configured to open and close the discharge port 27a formed with a relatively large diameter. A first spring 63 mounted between the inner surface and the partition wall 50 urges the discharge port 27a to a closed position. Further, the spool valve 61 includes a sliding portion 61b having a substantially U-shaped vertical cross section, which is connected to both ends of the shaft portion 61a, and a substantially cylindrical valve body 61c for opening and closing the one end opening 58a of the fourth oil passage 58. The valve body 61c has a pressure receiving surface 61d formed on the outer end surface thereof for receiving the hydraulic pressure from the upper liquid chamber 31 via the pressure passage 59. Also, spool valve 6
1 is urged by a second spring 64 mounted between the sliding portion 61b and the partition wall 50 to the right side in the figure, that is, a position where the fourth oil passage 58 is opened.

Furthermore, the set load of the first and second springs 63, 64 is determined by the relative relationship with the combustion pressure acting on the crown surface of the outer piston 21 during the expansion stroke, and both 63, 64 at the time of high load. It is set to be shortened only when a high combustion pressure is applied.

Since the other configurations are the same as those in the first embodiment, the same reference numerals are given and the detailed description will be omitted.

The operation of the second embodiment will be described below. When the engine is started or the load is low, relatively low pressure oil is sent from the main passage 34 to the right chamber 52 of the hydraulic fluid chamber 25, as shown in FIG.
From here, it is supplied to the upper liquid chamber 31 via the first oil passage 35 and the check valve 41 opened by this hydraulic pressure. And at this point,
Since the discharge valve 60 closes the discharge port 27a and the spool valve 61 opens the fourth oil passage 58,
While the volume of the upper liquid chamber 31 increases rapidly, the lower liquid chamber 32
Pressure oil is discharged into the right chamber 52 through the fourth oil passage 58, and is supplied to the upper liquid chamber 31 as it is along with the pressure oil from the main passage 34. Therefore, the outer piston 21 quickly rises with respect to the inner piston 29, so that a high compression ratio state can be secured with good responsiveness. Especially in the low compression ratio state (5th
When the engine is shifted from the high load region to the low load region shown in FIG. 4), the spool valve 61 is moved to the second spring 64 during the engine cycle other than the expansion stroke as shown in FIG. The opening 58 of the fourth oil passage 58 is caused by the spring pressure.
It is urged to the position where a is opened, that is, the pressure oil from the lower liquid chamber 32 stands by so that it can be discharged into the right chamber 52. Therefore, when the low load region is reached, the pressure oil is immediately discharged from the lower liquid chamber 32, the volume of the lower liquid chamber 32 is rapidly reduced, and the volume of the upper liquid chamber 31 is rapidly increased. Therefore, the responsiveness of switching from the low compression ratio state to the high compression ratio is further improved.

On the other hand, when the load is high, the high combustion pressure during the expansion stroke acts on the crown surface of the outer piston 21 and the pressure in the upper liquid chamber 31 increases, and as shown in FIG. When the discharge valve 60 is introduced into the pressure chamber 51 and acts on the pressure receiving portion 60a of the discharge valve 60,
It moves to the right in the figure against the spring pressure of the spring 63 to open the discharge port 27a. At the same time, the spool valve 61 moves to the left in the drawing against the spring pressure of the second spring 64 due to the oil pressure from the pressure passage 59 acting on the pressure receiving surface 61d, and closes the fourth oil passage 58. Therefore, the pressure oil in the upper liquid chamber 31 is transferred to the second oil passage 36.
And is quickly discharged from the discharge port 27a to the outside through the pressure chamber 51, and at the same time, a part of the pressure chamber 51 is rapidly supplied to the lower liquid chamber 32 through the third oil passage 37 while opening the check valve 42. It Therefore, the volume of the upper liquid chamber 31 immediately decreases, the outer piston 21 descends with respect to the inner piston 29, and a low compression ratio state can be secured with good responsiveness. Further, as described above, since the pressure oil is rapidly supplied into the lower liquid chamber 32 as the outer piston 21 rapidly descends, it is of course possible to promote the switching response to the low compression ratio. No negative pressure is generated in the chamber 32, and therefore air is prevented from entering from the outside. Here, the fourth oil passage 58 is controlled to be in a closed state and is opened by the spring pressure of the second spring 64 during a cycle other than the expansion stroke, but the opening time is short, so that the lower liquid chamber 32 to the right chamber is opened.
There is very little leakage of pressure oil to 52. Therefore, a stable low compression ratio state is achieved without affecting the maintenance of the low compression ratio state. The discharge valve 60 closes the discharge port 27a by the first spring 63 during the cycle other than the expansion stroke as in the case of the first embodiment, so that the air from the discharge port 27a to the upper and lower liquid chambers 31 and 32 is discharged. It goes without saying that the backflow of is prevented.

In addition, in such a low compression ratio state, a small amount of pressure oil in the right chamber 52 passes through the first oil passage 35 and the second oil passage 36 to the upper liquid chamber.
The effect of circulating the passage groove 56 of 31 to cool the piston crown is the same as that of the first embodiment.

EFFECTS OF THE INVENTION As is clear from the above description, according to the compression ratio variable device for an internal combustion engine according to the present invention, it is possible to reverse the pressure oil supplied to the upper liquid chamber and the lower liquid chamber by the front and rear hydraulic pressures. In addition to supplying through the stop valve, when switching from the high compression ratio state to the low compression ratio state, the pressure oil in the upper liquid chamber is discharged to the outside, so switching from the high compression ratio state to the low compression ratio state Good responsiveness. Moreover, since the on-off valve for discharging the pressure oil in the upper liquid chamber is operated in accordance with the combustion pressure due to the change in engine operation, the switching response from the high compression ratio state to the low compression ratio is further improved. Further, when a high compression ratio state is obtained, the check valve can be opened with only a small hydraulic pressure, unlike the conventional case, so that a general lubricating oil pump can be used.

Further, since the pressure oil circulates in the upper liquid chamber in the low compression ratio state, it is possible to effectively cool the crown portion of the piston and prevent deterioration of the pressure oil.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part showing a high compression ratio state in a first embodiment of the present invention, FIG. 2 is a cross-sectional view of an essential part showing a low compression ratio state of this embodiment, and FIG. FIG. 4 is a sectional view of an essential part showing a high compression ratio state in the second embodiment, FIG. 4 is a sectional view of an essential part showing a process of switching from a low compression ratio state to a high compression ratio state of this embodiment, and FIG. FIG. 6 is a cross-sectional view of an essential part showing an example low compression ratio state, FIG. 6 is an overall configuration diagram showing a conventional compression ratio variable device, and FIG. 7 is a cross-sectional view showing a part of the conventional device. 21 …… Outer piston, 23 …… Piston pin, 24 …… Operating fluid chamber, 26 …… Spool valve (open / close valve), 27a …… Discharge port, 29 …… Inner piston, 31 …… Upper fluid chamber, 32… … Lower liquid chamber, 35 …… First oil passage, 36 …… Second oil passage, 37 ……
3rd oil passage, 38a, 38b, 58 ... 4th oil passage, 41, 42 ... Check valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seinosuke Hara Atsugi City Kanagawa Prefecture 1370 Onna Motor Parts Co., Ltd. (72) Inventor Tatsuyuki Matsuya 1370 Atsugi City Kanagawa Prefecture Atsugi Motor Parts Co., Ltd. (72) Inventor Yasuo Takashima 1370, Onna, Atsugi City, Kanagawa Prefecture Atsugi Auto Parts Co., Ltd. (56) Reference JP 64-24130 (JP, A) JP 63-202749 (JP, U) Actual development Sho 58-25637 (JP, U)

Claims (1)

(57) [Claims] 1. An inner piston supported at both ends of a piston pin, an outer piston axially slidably fitted on an outer circumference of the inner piston, and formed between the outer piston and the inner piston. Upper and lower liquid chambers, a working fluid chamber formed at a predetermined position inside the piston pin or the inner piston, and into which pressure oil is introduced from the outside, and pressure oil in the working fluid chamber before and after the hydraulic fluid. A first oil passage for supplying to the upper liquid chamber via a check valve that opens and closes with a second oil passage for discharging pressure oil in the upper liquid chamber to the outside through a discharge port, and a second oil passage And a fourth oil passage for discharging the pressure oil in the lower liquid chamber, and a third oil passage for communicating the pressure oil in the upper liquid chamber to the lower liquid chamber via a check valve that opens and closes by front and rear hydraulic pressure. It is slidably housed in the oil passage and the hydraulic fluid chamber, and Variable compression ratio device for an internal combustion engine, characterized in that a closing valve for opening and closing a fourth oil passage and the discharge port in response to pressure changes in the upper liquid chamber based on the pressure.