JPH063166Y2 - Variable compression ratio device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to improvement of a compression ratio variable device for an internal combustion engine.

(Prior Art) In an internal combustion engine for an automobile or the like, there is a device that makes a compression ratio of the engine variable in order to prevent knocking that occurs due to high supercharging of intake air.

As such a device, as shown in FIG. 3 for example, there is a device in which a slidable inner piston 2 is provided on a piston body 1 and the inner piston 2 is swingably connected to a connecting rod 4. A seal ring 21 is interposed between the piston body 1 and the inner piston 2 to seal the oil chamber 5, and pressurized oil from an oil pump 22 is introduced into the oil chamber 5 via an inlet side passage 23. The piston body 1 is pushed up against the inner piston 2 in accordance with the hydraulic pressure, and the volume of the combustion chamber 19 is changed to increase the compression ratio. In the figure, reference numeral 24 is an outlet side passage for discharging the oil in the oil chamber 5, and 25 and 26 are control valves for controlling the hydraulic pressure (see Japanese Utility Model Laid-Open No. 57-57237).

(Problems to be Solved by the Invention) However, in such a conventional compression ratio variable device, air bubbles may be mixed in the oil guided through the inlet side passage 23, and the oil supply to the oil chamber 5 may be increased. Since the discharge is performed through the inlet and outlet side passages 23, 24, the bubbles once flowing into the oil chamber 5 are difficult to be discharged, and the oil chamber 5 becomes compressible even in the high compression ratio state in which the pressurized oil is supplied. As a result, the piston body 1 is displaced, which makes it difficult to maintain an appropriate compression ratio.

The present invention aims to solve the above problems.

(Means for Solving Problems) The present invention provides an inner piston slidably fitted to a piston body, and swingably connects the inner piston to a connecting rod via a piston pin, In the compression ratio variable device of the internal combustion engine, which forms an oil chamber between the bottom surface of the inner piston and the top surface of the inner piston, and connects an oil passage for supplying pressurized oil to the oil chamber, While forming a drain passage connecting the outer peripheral surface, a drain hole connecting the inner peripheral surface of the piston body and the oil ring groove is formed in the piston body, and two drain holes are formed between the outer peripheral surface of the inner piston and the inner peripheral surface of the piston body. With the seal ring interposed, the drain passage and the drain hole are both opened between the respective seal rings in the low compression ratio state, and at the same time, the drain passage and the drain hole are opened in the high compression ratio state. It is arranged so that the drain passage or the drain hole is closed by a reel ring.

(Operation) Based on the above configuration, when air bubbles enter the oil chamber, the drain passage communicates with the oil ring groove through the drain hole when switching from the low compression ratio state to the high compression ratio state. Moreover, the bubbles retained in the oil chamber are discharged to the oil ring groove together with the oil to promote the discharge of the bubbles, so that an appropriate compression ratio can be always maintained.

(Embodiment) An embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the inner piston 2 is slidably fitted inside the piston body 1, and the inner piston 2
Is swingably connected to a connecting rod 4 via a piston pin 3.

The bottom surface 1a of the piston body 1 and the top surface 2a of the inner piston 2
An oil chamber 5 is formed between the inner piston 2 and the connecting rod 4, and an inlet-side passage 14 for supplying high-pressure oil to the oil chamber 5 via a control valve (not shown) according to operating conditions; The outlet side passages 15 for discharging the oil in 5 are respectively formed. Thereby, the oil pressure in the oil chamber 5 is adjusted to push the piston body 1 up against the inner piston 2 to increase the compression ratio.

The top surface 2a of the inner piston 2 is raised in a spherical shape (dome shape), while the bottom surface 1a of the piston body 1 is recessed in a spherical shape so that the gap between the top surface 2a and the top surface 2a becomes gradually smaller toward the center.

The inner piston 2 has an uppermost portion and an outer peripheral portion on the top surface 2a.
A drain passage 9 connecting 2b is formed. The drain passage 9 has a through hole 9a opening at the center of the top surface 2a and a plurality of through holes radially branching from the other end of the through hole 9a and opening at the outer peripheral surface 2b.
Formed by 9b.

The passage diameter of the through hole 9a is smaller than that of the inlet passage 14 at a predetermined ratio.

A predetermined gap is formed between the inner peripheral surface 1b of the piston body 1 and the outer peripheral surface 2b of the inner piston 2.
The seal rings 7 and 8 are fitted into the ring grooves 7a and 8a formed on the outer peripheral surface 2b so as to sandwich the open ends of the through holes 9b.

On the piston body 1, the inner peripheral surface 1b and the oil ring groove 13 are provided.
A plurality of drain holes 6 connecting the bottom surfaces 13a of the above are formed at predetermined intervals. The drain hole 6 is opened between the seal rings 7 and 8 in the low compression ratio state as shown in FIG. 1, while it is in the combustion chamber side as shown in FIG. It is arranged so as to be closed by the seal ring 7 of.

Based on the above configuration, in the low compression ratio state, the oil supply from the inlet side passage 14 to the oil chamber 5 is stopped, and the piston body 1 is seated on the outer peripheral portion of the top surface 2a of the inner piston 2 as shown in FIG. Let

When the high compression ratio state is set, the outlet side passage 15 is closed through a control valve (not shown), while high pressure oil is supplied from the inlet side passage 14 to move the piston body 1 to the inner piston 2 as shown in FIG. Push up.

In the process of pushing up the piston body 1 in this way, when the lift amount of the piston body 1 is small to some extent, the drain passage 9 communicates with the oil ring groove 13 through the drain hole 6 and the inside of the oil chamber 5 is closed. The oil is discharged to the oil ring groove 13, but the amount of this discharge causes the passage 1 on the inlet side to
Since the flow rate supplied from 4 is higher, the piston body 1 is pushed up, and when the lift amount reaches a certain degree, the drain hole 6 is closed by the seal ring 7.

If air bubbles flow into the oil chamber 5 from the inlet side passage 14,
When the drain passage 9 communicates with the oil ring groove 13 through the drain hole 6 in the process of pushing up the piston body 1, the bubbles in the oil chamber 5 are discharged into the oil ring groove 13 together with the oil. Since the drain passage 9 is opened to the spherically-topped top surface 1a, bubbles collected in the upper part of the oil chamber 5 can be effectively discharged. As a result, in the high compression ratio state in which the drain hole 6 is closed by the seal ring 7, the rattling of the piston body 1 due to the contraction of the bubbles is prevented.

Even in the low compression ratio state, since the drain passage 9 communicates with the oil ring groove 13 through the drain hole 6, there is oil circulation in the oil chamber 5, and as a result, the piston body 1 is operated under high load operating conditions. It is possible to prevent the oil in the oil chamber 5 from being carbonized by the heat transfer from the, and to maintain good operability.

In this embodiment, the seal rings 7 and 8 are fixed to the outer peripheral surface 2b of the inner piston 2. However, the seal rings 7 and 8 are fixed to the inner peripheral surface 1b of the piston body 1 with the drain hole 6 interposed therebetween, and the drain passage 9 is formed in a high compression ratio state. It may be closed by one seal ring 7.

(Effect of the Invention) As described above, according to the present invention, the drain passage opening on the top surface of the inner piston is connected to the oil ring groove of the piston body through the two seal rings, and the drain passage is connected to the oil passage at a low compression ratio. In addition to communicating the oil ring groove, the seal ring on one side shuts off the communication between the drain passage and the oil ring groove in the high compression ratio state, so that when the bubbles entering the oil chamber can be switched to the high compression ratio, the oil ring Discharge to the groove to prevent fluctuations in the compression ratio, enabling precise compression ratio control.

[Brief description of drawings]

FIG. 1 is a sectional view showing a low compression ratio state in an embodiment of the present invention,
FIG. 2 is a sectional view showing a high compression ratio state. Third
The figure is a cross-sectional view showing a conventional example. 1 ... Piston body, 2 ... Inner piston, 3 ... Piston pin, 4 ... Connecting rod, 5 ... Oil chamber, 6 ... Drain hole, 7,
8 ... Seal ring, 9 ... Drain passage, 13 ... Oil ring groove, 14 ... Inlet side passage, 15 ... Outlet side passage

Claims (1)

[Scope of utility model registration request] An inner piston slidably fitted to a piston body is provided, and the inner piston is swingably connected to a connecting rod via a piston pin,
In a compression ratio variable device for an internal combustion engine in which an oil chamber is formed between the bottom surface of the piston body and the top surface of the inner piston, and an oil passage for supplying pressurized oil to this oil chamber is connected, While forming a drain passage connecting the surface and the outer peripheral surface, the piston body is formed with a drain hole connecting the inner peripheral surface and the oil ring groove, and between the outer peripheral surface of the inner piston and the inner peripheral surface of the piston body. Two seal rings are interposed, and the drain passage and the drain hole are both opened between the seal rings in a low compression ratio state, and the drain passage or the drain hole is formed in the one seal ring in a high compression ratio state. A compression ratio variable device for an internal combustion engine, characterized in that it is arranged so as to close.