JPH063167Y2 - Variable compression ratio device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to improvement of 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 arranged outside the inner piston 3. An upper liquid chamber 5 is provided between the outer piston 4 and the upper portion of the inner piston 3 and
Lower liquid chambers 8 are formed between an annular portion 7 and an inner piston 3, which are screwed to the inner circumference of the lower portion of the oil tank, respectively, and a hydraulic pressure for supplying pressure oil as working oil to the upper and lower liquid chambers 5, 8. A spool valve 10 slidably accommodated in the hydraulic fluid chamber 17 and check valves 11 and 12 biased in the closing direction by springs 11a and 12a are provided in the middle of the circuit 9. Further, the spool valve 10 includes a cylindrical valve body 10b and a sliding body 10c which are connected to each other via a shaft portion 10a. It is controlled by the control circuit 15 which issues a command.

When the compression ratio is increased when the engine is started or when the load is low, the pressurization of the pressurizer 14 is strengthened so that the pressure oil in the oil pan 16 reaches the oil passages 9a → 9b → 9c, where
The check valve 11 is pushed up against the pressure of the spring 11a and flows into the upper liquid chamber 5, while the pressure oil resists the spool valve 10 against the spring pressure of the spring 18 through the oil passage 9b and the hydraulic liquid chamber 17. And push it to the right. Therefore, the spool valve 1
No. 0 valve element 10b closes the oil passage 9d, and the oil passages 9e, 9f
As a result, the pressure oil in the lower liquid chamber 8 is discharged to the outside, and at the same time, a large amount of pressure oil is supplied into the upper liquid chamber 5 via the oil passage 9b to raise the outer piston 4 and raise the high compression ratio. The state is obtained.

On the other hand, when lowering the compression ratio 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 hydraulic pressure in the inside is reduced, the check valve 11 closes the oil passage 9c by the urging force of the spring 11a, and the spool valve 10 moves leftward as shown in FIG. 5 to close the oil passage 9f and close the oil passage 9d. Opened 9e. 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 descends to obtain the low compression ratio state. . Incidentally, reference numeral 6 in the figure denotes a seal member for the lower liquid chamber 8.

Problems to be Solved by the Invention However, in the above conventional compression ratio variable device,
When switching from the high compression ratio state to the low compression ratio state as described above, the oil pressure in the hydraulic fluid chamber 17 is reduced to open the oil passages 9d and 9e by the spool valve 10, and this continuous one oil passage is opened. Pressure oil is supplied to the lower liquid chamber 8 from 9d and 9e. That is, in the lower liquid chamber 8, the lower liquid chamber 8
The pressure oil in the upper liquid chamber 5 sufficiently separated from the one oil passage 9d, 9
It is designed to be supplied only from e. Therefore, the pressure oil cannot be quickly supplied to the lower liquid chamber 8 due to the conduit length and conduit resistance of the oil passages 9d and 9e. As a result, the switching response from the high compression ratio state to the low compression ratio state deteriorates.

Further, since the supply speed of the pressure oil to the lower liquid chamber 8 becomes slow, for example, the combustion pressure under high load acts on the crown surface of the outer piston 4, and the outer piston 4 causes the inner piston 3 to move.
Negative pressure is generated in the lower liquid chamber 8 when it rapidly descends from
There is a risk that air may enter from the sliding parts of the outer piston 4 and the inner piston 3 or the like. Therefore, especially when the compression ratio is low, vertical fluctuation of the outer piston 4 with respect to the inner piston 3 is likely to occur due to engine cycle fluctuation,
The low compression ratio state cannot be stabilized.

Means for Solving the Problems The present invention has been devised in view of the problems of the above-mentioned conventional device, and in particular, the hydraulic circuit includes a first oil passage for supplying pressure oil from the hydraulic fluid chamber to the lower fluid chamber. And a second oil passage for supplying the pressure oil in the upper liquid chamber to the lower liquid chamber in accordance with the combustion pressure applied to the outer piston.

According to the present invention having the above-mentioned configuration, when the high compression ratio state is switched to the low compression ratio state, the pressure oil in the hydraulic fluid chamber is supplied from the first oil passage to the lower fluid chamber, and at the time of the expansion stroke. When a high combustion pressure acts on the outer piston to raise the pressure in the upper liquid chamber, pressure oil in the upper liquid chamber is also supplied to the lower liquid chamber via the second oil passage. Therefore, a large amount of pressure oil is rapidly supplied to the lower liquid chamber in accordance with changes in the operating state.

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 a compression ratio variable device according to the present invention, in which 21 denotes an outer shell of a piston,
Also, an outer piston having an annular portion 22 screwed to the inner periphery of the lower portion, and 23 is a piston pin connected to a small end portion of the connecting rod 24. The piston pin 23 has a stepped columnar hydraulic fluid chamber inside. 25 is formed along the axial direction, a disk-shaped closing plate 26 for sealing one end of the hydraulic fluid chamber 25 is provided at the left end in the drawing, and a passage forming part having a discharge port 27a at the center at the right end. 27 is fitted and fixed. The hydraulic fluid chamber 25 is divided into a closed oil introduction chamber 29 on the left side and a pressure chamber 30 on the right side via a substantially bowl-shaped partition wall 28 fixed to the right side from the center. A spool valve 31 that opens and closes the discharge port 27a is provided in the pressure chamber 30 so as to be slidable in the left and right axial directions.

Reference numeral 32 in the drawing denotes an inner piston fixed to both ends of the piston pin 23 via boss portions 33, 33, and the outer piston 21 can slide vertically on the outer side of the inner piston 32. Has been fitted into. Also,
The lower surface 21a of the crown portion of the outer piston 21 and the inner piston 3
The upper liquid chamber 34 is formed between the upper surface 32a of the second piston 2 and the upper surface 32a of the inner piston 32, and the lower portion of the annular shape is formed between the upper surface of the annular portion 22 and the lower surface of the inner piston 32 that regulates the maximum upward movement of the outer piston 21. Liquid chambers 35 are respectively formed, and pressure oil is supplied to and discharged from the liquid chambers 34, 35 via a hydraulic circuit 36 to relatively change the volumes thereof, respectively.
1 is vertically moved relative to the inner piston 32.

The hydraulic circuit 36 is formed in the inner axial direction of the connecting rod 24 and extends along the main passage 37 for introducing pressure oil from the outside, which will be described later, into the oil introducing chamber 29, and the piston pin 23 and the inner piston 32 along the vertical direction. A supply passage 38 that is formed so as to penetrate therethrough to supply pressure oil from the oil introduction chamber 29 to the upper liquid chamber 34;
The supply passage 38 is formed so as to penetrate substantially in parallel with the connecting rod 24 at the right-side symmetrical position so that the pressure oil in the upper liquid chamber 34 passes through the pressure chamber 30, the discharge port 27a, and the through hole 21b on the side of the outer piston 21. And a first oil passage 40 that is formed at a lower position sandwiching the piston pin 23 of the supply passage 38 and that supplies the pressure oil of the oil introduction chamber 29 to the lower liquid chamber 35. A second oil passage 41 that is formed on the right end side of the piston 32 in the vertical direction to supply pressure oil to the upper liquid chamber 34 to the lower liquid chamber 35, and a vertical direction to the left end side of the inner piston 32 in the drawing. A third oil passage 42 formed along the discharge passage 39 to discharge the pressure oil in the lower liquid chamber 35 to the upper liquid chamber 34, and a hydraulic pressure in the upper liquid chamber 34 formed in parallel with the left side of the discharge passage 39. A signal for transmitting a signal to the spool valve 31 in the pressure chamber 30. And a pressure passage 43. Then, in the supply passage 38 and the first oil passage 40, first and second check valves 44, which allow the flow of pressure oil only from the oil introduction chamber 29 toward the upper liquid chamber 34 or the lower liquid chamber 35, respectively. In the discharge passage 39 and the second oil passage 41, the third and fourth check valves 46, 4 allow the pressure oil to flow only from the upper liquid chamber 34 toward the discharge port 27a or the lower liquid chamber 35, respectively.
7 are provided respectively, and the first to fourth check valves 44 to 4 are provided.
In FIG. 7, check balls 44a, 45a, 46a, 47a are opened and closed by the hydraulic pressure in the front and rear. The third oil passage 42 having no check valve is formed to have a smaller passage sectional area than the other oil passages.

Further, the spool valve 31 includes a flange-shaped sliding portion 31a on the left end side that slides in the pressure chamber 30, and a cylindrical valve body 31b on the right end side that opens and closes one end of the discharge passage 39 and has a relatively small diameter.
Located between the valve body 31b and the sliding portion 31a, the signal pressure passage 4
And a pressure-receiving portion 31c having a stepped annular shape for transmitting and receiving the hydraulic signal from the control unit 3. Further, the spool valve 31 is urged by a compression spring 48 mounted between the end face of the opening on the sliding portion 31a side and the partition wall 28 to the right in the drawing, that is, a position where the discharge passage 39 is closed. The maximum movement position to the right is restricted by the passage forming portion 27.

The set load of the compression spring 48 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 is reduced only when the high combustion pressure at high load acts on the pressure receiving portion 31c. Is set.

In addition, on the upper outer periphery and the lower outer periphery of the inner piston 32,
Sealing rings 49 and 50 are provided to prevent pressure oil from leaking to the outside through the clearance at the sliding portion between the inner piston 32 and the outer piston 21 or the annular portion 22. In the figure, 51 and 51 are stopper rings for restricting the movement of the piston pin 23 in the axial direction.

The engine lubricating oil in the oil pan is fed under pressure to the main passage 37 by a general mechanical oil pump (not shown) that is synchronized with the engine rotation.

The operation of this embodiment will be described below. First, when the engine is started or when the load is low, a pressure oil having a relatively high pressure is sent from the main passage 37 to the oil introduction chamber 29 by the oil pump, and from there, the supply passage 38 and the first check valve 44 opened by this hydraulic pressure.
And is supplied to the upper liquid chamber 34. At this time point, the combustion pressure acting on the crown surface of the outer piston 21 is relatively small, and the signal oil pressure transmitted to the pressure receiving portion 31c of the spool valve 31 via the signal pressure passage 43 is also small. Since 31b closes the discharge passage 39 by the spring force of the compression spring 48 as shown in FIG. 1, the volume of the upper liquid chamber 34 increases rapidly, while the lower liquid chamber 35 is entrained in the volume. The pressure oil inside is the third oil passage 42.
And is discharged into the upper liquid chamber 34 via. As a result, the outer piston 21 quickly rises from the inner piston 32, and a high compression ratio state can be secured with good responsiveness.

Here, even if the compression pressure or the combustion pressure acts on the crown surface of the outer piston 21 during the compression stroke or the expansion stroke, the first check valve 44 prevents the backflow of the pressure oil.
On the other hand, since the third oil passage 42 does not have a check valve, the pressure oil of the upper liquid chamber 34 slightly flows back to the lower liquid chamber 35 through this, but this also causes the inertia of the outer piston 21 during the exhaust stroke. When the pressure rises, the liquid is replenished from the supply passage 38 into the upper liquid chamber 34, so that the high compression ratio state can be sufficiently maintained. In addition, as described above, even if a small amount of pressure oil is supplied to and discharged from the lower liquid chamber 35 via the third oil passage 42 as the engine cycle changes, the third oil passage 42 does not communicate with the outside. ,
Since it is directly communicated with the upper liquid chamber 34, air is reliably prevented from entering the lower liquid chamber 35. As a result, the unstable behavior of the outer piston 21 due to the engine cycle fluctuation can be sufficiently prevented even in the low compression ratio state described later.

Incidentally, here, when supplying the pressure oil to the upper liquid chamber 34, it is not necessary to operate the spool valve by hydraulic pressure as in the conventional case, and the check ball 44a of the first check valve 44 is simply opened by a small hydraulic pressure. Therefore, a general oil pump can be used together, which is advantageous in terms of cost.

On the other hand, at the time of high load, when the high combustion pressure at the beginning of the expansion stroke acts on the crown surface of the outer piston 21 and the pressure in the upper liquid chamber 34 increases, the hydraulic pressure becomes the signal pressure as shown in FIG. The pressure is transmitted from the passage 43 to the pressure receiving portion 31c of the spool valve 31 via the pressure chamber 30. Therefore, the spool valve 31 instantaneously moves to the left in the drawing against the spring pressure of the compression spring 48, and opens the discharge passage 39. Therefore, the pressure oil in the upper liquid chamber 34 is quickly discharged to the outside from the through hole 21b through the discharge passage 39 and the discharge port 27a. Therefore,
The volume of the upper liquid chamber 34 is rapidly reduced, the outer piston 21 is lowered, and a low compression ratio state can be secured with good responsiveness.
Moreover, in the lower liquid chamber 35, the pressure oil in the oil introduction chamber 29 and the upper liquid chamber 34 is first discharged at the same time when the pressure oil in the upper liquid chamber 34 is discharged.
Since the oil is rapidly supplied while opening the second and fourth check valves 45 and 47 through the two oil passages of the oil passage 40 and the second oil passage 41, the above high compression ratio state changes to the low compression ratio state. Switching responsiveness is further improved. Further, since the pressure oil is supplied to the lower liquid chamber 35 at a high speed, a negative pressure is not generated in the lower liquid chamber 35, and therefore air is prevented from entering from the outside air.

Further, in this embodiment, since the oil introduction chamber 29 and the pressure chamber 30 are separated from each other by the partition wall 28 to be in a separated and independent state, the spool valve 31 is particularly when switching from the high compression ratio state to the low compression ratio state. Mobility is improved. That is, in the above-mentioned conventional device, the spool valve for switching between the high compression ratio and the low compression ratio depends on the hydraulic pressure passing through the oil passage formed in the connecting rod and the piston pin, and the hydraulic pressure reciprocates the piston and the connecting rod. It fluctuates constantly due to the swinging motion of. Therefore, the spool valve
Since it constantly vibrates in the axial direction due to the influence of the fluctuation of the hydraulic pressure, the mobility at the time of switching the compression ratio deteriorates, and it becomes difficult to perform the quick switching. So, in this example,
As described above, the chambers 29 and 30 are separated, and the hydraulic pressure supply system for the oil introduction chamber 29 and the signal pressure supply system for the spool valve 31 are separated. Therefore, the spool valve 31 is not affected by the hydraulic pressure fluctuation of the hydraulic pressure supply system. It disappears, rapid mobility corresponding to the combustion pressure is obtained, and the switching of the compression ratio becomes smooth.

FIG. 3 shows a second embodiment of the present invention, which is different from the first embodiment mainly in the structure of the spool valve. That is,
The spool valve 61 is disposed along the axial direction in the hydraulic fluid chamber 25 in which the partition wall is abolished, and has a large-diameter substantially U-shaped sliding portion 61a at both ends of the shaft portion 61d and the sliding portion 61a. It has a cylindrical valve body 61b having a small pressure receiving area, and has a stepped shape to which the hydraulic pressure from the signal pressure passage 43 whose position is different from that of the first embodiment is transmitted to the outer periphery of the sliding portion 61a. The pressure receiving portion 61c is formed. Further, the third oil passage for discharging the pressure oil from the lower liquid chamber 35 to the upper liquid chamber 34 is eliminated, and the lower liquid chamber 3
The pressure oil in 5 is the inner piston 3 without the seal ring.
2 is leaked from the clearance of the sliding portion between 2 and the annular portion 22.

Further, the main passage 37 formed in the connecting rod 24 is provided at the upper end thereof with a fifth check valve 62 which allows only the flow of pressure oil from the main passage 37 in the direction of the hydraulic fluid chamber 25.

Further, as in the first embodiment, the hydraulic fluid chamber 25 and the upper fluid chamber 34 are
It has a first oil passage 40 and a second oil passage 41 for simultaneously supplying the respective pressure oils to the lower liquid chamber 35. Other configurations are first
Since it is similar to the embodiment, the same reference numerals are given and the description is omitted.

The operation of this embodiment is substantially the same as that of the first embodiment, but when combustion pressure or compression pressure acts on the crown surface of the outer piston 21 in the high compression ratio state shown in FIG.
Since the check valve 44 prevents the backflow of the pressure oil from the upper liquid chamber 34 to the working liquid chamber 25, the fifth check valve 62 also prevents the backflow from the working liquid chamber 25 to the main passage 37. The high compression ratio state can be sufficiently maintained. At this point, the pressure oil in the upper liquid chamber 34 is supplied into the working liquid chamber 25 via the signal pressure passage 43, and further supplied from the working liquid chamber 25 to the lower liquid chamber 35 through the first oil passage 40. Upper liquid chamber 34
However, since the outer piston 21 is lifted from the inner piston 32 by the upper inertia force during the exhaust stroke, it is replenished from the supply passage 38, so that the high compression ratio state is not significantly affected. . Further, the pressure oil in the lower liquid chamber 35 at the time of switching to such a high compression ratio state leaks from the clearance at the sliding portion between the inner piston 32 and the annular portion 22. Other functions and effects are similar to those of the first embodiment.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the compression ratio variable device for an internal combustion engine according to the present invention, particularly in the first oil passage for supplying pressure oil from the hydraulic fluid chamber to the lower fluid chamber, and the outer piston. Since the second oil passage for supplying the pressure oil in the upper liquid chamber to the lower liquid chamber in accordance with the applied combustion pressure is provided, the pressure oil is changed between the above two when the high compression ratio state is switched to the low compression ratio state. It is quickly supplied from the oil passage to the lower liquid chamber at the same time. As a result, the response to switching to the low compression ratio state becomes extremely good, and air is prevented from entering the lower liquid chamber,
Vertical fluctuation of the outer piston with respect to the inner piston due to engine cycle fluctuation is suppressed, and a stable high and low compression ratio state is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part showing a high compression ratio state in a first embodiment of the present invention, FIG. 2 is a sectional view of a main part showing a low compression ratio state of this embodiment, and FIG. FIG. 4 is a sectional view of a main part showing a high compression ratio state in the second embodiment, FIG. 4 is an overall configuration diagram showing a conventional compression ratio variable device, and FIG. 5 is a partial sectional view of the conventional device. 21 ... Outer piston, 23 ... Piston pin, 24 ... Connecting rod, 25 ... Hydraulic fluid chamber, 32 ... Inner piston, 3
4 ... Upper liquid chamber, 35 ... Lower liquid chamber, 36 ... Hydraulic circuit, 40
... first oil passage, 41 ... second oil passage.

Front page continuation (72) Inventor Yasuo Takashima 1370, Onna Atsugi, Kanagawa Pref., Atsugi Auto Parts Co., Ltd. (72) Inventor, Seinosuke Hara 1370, Onna, Atsugi, Kanagawa Pref. Tatsuyuki Matsuya 1370 Onna, Atsugi City, Kanagawa Prefecture Atsugi Auto Parts Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. An inner piston connected to a connecting rod via a piston pin, an outer piston axially slidably fitted on the outer circumference of the inner piston, and between the outer piston and the inner piston. It has an upper liquid chamber and a lower liquid chamber that are formed, and supplies hydraulic pressure to each of the upper and lower liquid chambers via a working liquid chamber and a hydraulic circuit to move the outer piston vertically relative to the inner piston. In the variable compression ratio device configured as described above, the hydraulic circuit includes a first oil passage for supplying pressure oil from the hydraulic fluid chamber to the lower fluid chamber, and the upper fluid chamber in the upper fluid chamber in accordance with a combustion pressure applied to the outer piston. A compression ratio variable device for an internal combustion engine, comprising: a second oil passage for supplying pressure oil to the lower liquid chamber.