JPH0612214Y2 - 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, there is a device in which a slidable inner piston 2 is provided in a piston body 1 and the inner piston 2 is swingably connected to a connecting rod 4, as shown in FIG. 7, for example. A seal ring 33 is interposed between the piston body 1 and the inner piston 2 to seal the oil chamber 5, and the pressurized oil from the oil pump 34 is introduced into the oil chamber 5 via the inlet side passage 35. 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 39 is changed to increase the compression ratio. Reference numeral 36 in the drawing denotes an outlet side passage for discharging the oil in the oil chamber 5, and reference numerals 37 and 38 denote control valves for controlling the working 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, the protrusion 2G is formed on the inner piston 2, while the recess 1G which engages with the protrusion 2G is formed on the piston body 1. Since the lift amount of the piston main body 1 is regulated, when the upward inertial force acts on the piston main body 1 from the exhaust stroke to the intake stroke, the projection 2G collides with the step of the concave portion 1G and an impact sound is generated. There are problems that the noise is generated and the noise is increased or the piston is broken.

The present invention aims to solve the above problems.

(Means for Solving the Problems) The present invention provides a variable compression ratio device for an internal combustion engine, which is provided with an inner piston slidably fitted in a piston body and swings the inner piston to a connecting rod via a piston pin. In addition to being movably connected, a first oil chamber is formed between the bottom surface of the piston body and the top surface of the inner piston, and an oil passage is connected to the first oil chamber to supply pressurized oil according to operating conditions. On the other hand, inside the skirt portion of the piston body, a cylindrical inner sleeve having a predetermined length in the axial direction is mounted between the inner piston and the inner piston so as to wrap the piston pin, and the upper surface of the inner sleeve and the skirt of the inner piston are attached. And a second oil chamber communicating with the first oil chamber, the second oil chamber being arranged above the piston pin and below the piston pin. Installed and provided with a stopper ring that screws into the skirt of the piston body,
The inner sleeve is fastened via the stopper ring.

(Operation) Based on the above configuration, the oil pressure guided to the first oil chamber is adjusted according to the operating state, and this oil pressure pushes up the piston body against the inner piston to increase the compression ratio.

By making the oil leaked from the first oil chamber flow into the second oil chamber, the impact due to the inertial force acting on the piston body is mitigated, and the generation of impact noise is suppressed.

On the other hand, inside the skirt portion, a cylindrical inner sleeve having a predetermined length in the axial direction is attached so as to wrap the piston pin between the inner piston and the inner piston, and is positioned below the piston pin and screwed into the skirt portion. By providing a stopper ring and fastening the inner sleeve through this stopper ring, the inner sleeve is held by the skirt portion, and this inner sleeve enhances the rigidity of the piston body (the skirt portion thereof) and at the same time with respect to the inner piston. The rattling of the piston body is prevented, and smooth operability is obtained.

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

As shown in FIGS. 1, 2, and 3, the piston body 1
The inner piston 2 on the inner peripheral surface 1b of the skirt portion 1S.
The outer peripheral surface 2b is slidably inserted to form a first oil chamber 5 between the bottom surface 1a of the piston body 1 and the top surface 2a of the inner piston 2.

The piston pin 3 is fitted and inserted into each of the boss portion 2B of the inner piston 2 and the small end portion 4S of the connecting rod 4, and the inner piston 2 is swingably connected to the connecting rod 4 via the piston pin 3.

A cylindrical inner sleeve 7 is attached to the inside of the skirt portion 1S of the piston body 1, and an inner peripheral surface 7 of the inner sleeve 7 is attached.
The outer peripheral surface 2c of the inner piston 2 is slidably inserted into b, and a second oil chamber 8 is defined in an annular shape between an annular step portion 2d formed on the inner piston 2 and an upper surface 7a of the inner sleeve 7. When the upper surface 7a and the annular step portion 2d contact each other, the lift amount of the piston body 1 with respect to the inner piston 2 is regulated.

A seal ring groove 9A is formed on the outer peripheral surface 2b of the inner piston 2.
And a seal ring 9 which is in sliding contact with the inner peripheral surface 1b of the piston body 1 is interposed in the seal ring groove 9A,
The inner piston 2 is formed with a through hole 11 connecting the top surface 2a and the outer peripheral surface 2c thereof to communicate the first oil chamber 5 and the second oil chamber 8 with each other, and the orifice 110 is provided in the middle of the through hole 11. To form.

An annular step portion 1 is provided inside the skirt portion 1S of the piston body 1.
While integrally forming d, a stopper ring 6 that is screwed inside the skirt portion 1S of the piston body 1 is provided. The stopper ring 6 and the annular step portion 1d of the piston body 1 are provided.
The inner sleeve 7 is sandwiched between them. Stopper ring 6
A protruding step 6d is formed on the inner side of the inner surface of the inner sleeve 7, while an annular step 7d is formed on the inner sleeve 7 to be joined to the step 6d.

An annular step portion 1d that abuts the upper surface 7a of the inner sleeve 7 from the piston pin 3 so as to bring the second oil chamber 8 as close as possible to the first oil chamber 5. Above (combustion chamber side)
On the other hand, the stopper ring 6 is arranged below the piston pin 3 (on the crankshaft 10 side). As a result, the inner sleeve 7 is set to have a predetermined length in the axial direction so as to wrap the piston pin 3.

The screws formed on the stopper ring 6 and the piston body 1 are trapezoidal screws or square screws.

Two openings 1C are symmetrically formed in the skirt portion 1S of the piston body 1 so as to face both ends of the piston pin 3.

Two openings 7C are symmetrically formed in the inner sleeve 7 so as to face both ends of the piston pin 3.

A pin 12 protruding laterally is fitted into the lower end of the inner piston 2, while the pin 1 is provided inside the inner sleeve 7.
A guide groove 7E engaging with 2 is formed in the axial direction to prevent the piston body 1 from rotating.

An oil passage for supplying pressurized oil via the check valve 14 is provided in the first oil chamber 5. The check valve 14 is provided in the middle of a through hole 15 formed in the inner piston 2, and the through hole 15 is formed in the piston pin 3 and an annular gap 16 formed between the boss portion 2B and the piston pin 3. Through hole 17
And an annular gap 18 formed between the piston pin 3 and the small end portion 4S, and a through hole 1 penetrating the rod portion 4L of the connecting rod 4.
9, the large end 4B of the connecting rod 4 and the crankshaft 1
The annular gap 20 formed between 0 and the through hole 21 formed in the crankshaft 10, and the crankshaft 10
And the hydraulic source via an annular gap 21 formed in the main bearing portion 22 of the cylinder block.

As a hydraulic pressure source, a main oil pump 23 that is constantly mechanically driven by the engine and an electric auxiliary oil pump 24 that automatically operates when the engine is under a low load by a control circuit (not shown) are arranged in parallel. The discharge oil of the above is combined with the discharge oil of the auxiliary oil pump 24 via the check valve 25. In addition, the oil pumps 23 and 24 are provided with relief valves 26 and 2 that keep their discharge pressures below a predetermined value.
7 are provided.

The control circuit controls the intake air amount, throttle opening, intake negative pressure,
A detection signal such as a fuel injection amount is input, and the auxiliary oil pump 24 is driven only when the engine load is a low load of a predetermined value or less. Further, the control circuit may be configured to drive the auxiliary oil pump 23 only when knocking occurs in response to a signal from a knock sensor attached to each cylinder.

Based on the above configuration, when the engine load is low, the electric auxiliary oil pump 24 operates, and the check valve 14 is provided in the first oil chamber 5.
High-pressure oil flows in through the piston, and the piston body 1 is pushed up against the combustion pressure acting on the top surface 1e of the piston body 1 to increase the engine compression ratio.

At this time, part of the oil that has flowed into the first oil chamber 5 leaks into the second oil chamber 8 via the orifice 110, and an upward inertial force acts on the piston body 1 from the exhaust stroke to the intake stroke. At this time, the oil interposed between the step portion 2d of the inner piston 2 and the upper surface 7a of the inner sleeve 7 is compressed, and a part of the oil is discharged from the gap between the outer peripheral surface 2c of the inner piston 2 and the inner peripheral surface 7b of the inner sleeve 7. It leaks and is discharged to the oil pan 28. As a result, the impact caused by the inertial force acting on the piston body 1 is mitigated, the generation of impact noise between the piston body 1 and the inner piston 2 is suppressed, and the durability is enhanced.

In this way, the oil in the first oil chamber 5 is supplied to the orifice 110.
By leaking through the leak current, it is possible to arbitrarily set the leak flow rate and maintain an appropriate compression ratio.

During high-load operation, the operation of the electric auxiliary oil pump 24 is stopped, so that the oil pressure guided to the first oil chamber 5 via the check valve 14 is reduced, and the piston body 1 moves to the inner piston 2. The engine compression ratio is lowered without being pushed up, and knocking or the like is prevented.

At this time, since the main oil pump 23 continues to operate, low-pressure oil is supplied to the first oil chamber 5 via the check valve 14, and the oil that has flowed into the first oil chamber 5 is stored in the piston body 1. Inner peripheral surface 1b and outer peripheral surface 2 of the inner piston 2
It leaks from the gap b and flows into the second oil chamber 8. For this reason, the oil is always present in the second oil chamber 8 to alleviate the shock acting between the piston body 1 and the inner piston 2. Further, by continuing to supply the low oil pressure oil to the first oil chamber 5, it is possible to prevent the oil from being overheated and deteriorated.

Inside the skirt portion 1S of the piston body 1, an inner sleeve 7 having a predetermined length in the axial direction is attached between the inner piston 2 and the inner piston 2, and a stopper ring 6 for supporting the lower end of the inner sleeve 7 is attached. The skirt portion 1 of the piston body 1 is arranged below the piston pin 3.
By tightening and fixing the inner sleeve 7 with the stopper ring 6 that is screwed to the lower end of S, the rigidity of the skirt portion 1S can be increased by the inner sleeve 7, and the piston body 1 can be attached to the inner piston 2 via the inner sleeve 7. It is possible to suppress backlash and obtain smooth operability.

When the rigidity of the skirt portion 1S is increased by the inner sleeve 7, sufficient strength of the piston body 1 is ensured, and the openings 1C and 7C are formed in the skirt portion 1S and the inner sleeve 7 so as to face both ends of the piston pin 3. The piston pin 3 can be formed, the weight of the piston can be reduced, and the piston pin 3 can be easily assembled.

Next, in another embodiment shown in FIGS. 4, 5, and 6, a guide hole (opening) 1E is formed in the skirt portion 1S of the piston body 1.
While forming the guide hole 1E in the piston pin 3.
The stopper body 3F is slidably inserted into the stopper fin 3F so as to integrally prevent the piston body 1 from rotating.

A recess 2E extending in the axial direction is formed on the outer peripheral surface 2c of the inner piston 2, and a stopper key 31 is inserted into the recess 2E, while the stopper key 31 is slidable on the inner peripheral surface 7b of the inner sleeve 7. A guide groove 7F that is inserted into the piston body 1 is formed to prevent the piston body 1 from rotating.

Further, as in the above-described embodiment, the pin 12 protruding laterally is fitted into the lower end of the inner piston 2, while the guide groove 7 engaging with the pin 12 is provided inside the inner sleeve 7.
E is formed in the axial direction to prevent the piston body 1 from rotating.

As described above, the stopper fin 3F, the stopper key 31 and the pin 12 respectively prevent the piston body 1 from rotating, but it is possible to use only one of them.

(Effects of the Invention) As described above, according to the present invention, a cylindrical inner sleeve having a predetermined length in the axial direction is attached to the inner side of the skirt of the piston body so as to wrap the piston pin between the inner piston and the inner piston. A second oil chamber communicating with the first oil chamber is formed between the upper surface of the inner sleeve and the skirt portion of the inner piston, and the second oil chamber is arranged above the piston pin, By providing a stopper ring located below and screwed into the skirt of the piston body and fastening the inner sleeve through this stopper ring, the oil leaked from the first oil chamber can be guided to the second oil chamber. The impact of inertial force acting on the piston body is mitigated to suppress the generation of impact noise, while the inner sleeve increases the rigidity of the piston body and Tongue is prevented from rattling in the piston body via the inner piston, and durability is improved.

[Brief description of drawings]

1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line YY in FIG. 3, and FIG. 3 is a sectional view taken along line XX in FIG. FIG. 4 is an overall configuration diagram showing another embodiment,
FIG. 5 is a sectional view taken along the line YY in FIG. 6, and FIG.
It is sectional drawing which follows an X-ray. FIG. 7 is a sectional view showing a conventional example. 1 ... Piston body, 2 ... Inner piston, 3 ... Piston pin, 4 ... Connecting rod, 5 ... First oil chamber, 6 ... Stopper ring, 7 ... Inner sleeve, 8 ... Second oil chamber

Claims (1)

[Scope of utility model registration request] 1. An inner piston slidably fitted to a piston body is provided, the inner piston is swingably connected to a connecting rod via a piston pin, and a bottom surface of the piston body and a top surface of the inner piston are provided. A first oil chamber is formed in between, and an oil passage for supplying pressurized oil according to operating conditions is connected to the first oil chamber, while the inside of the skirt of the piston body is connected to the inner piston. A cylindrical inner sleeve having a predetermined length in the axial direction is attached so as to wrap the piston pin, and the second oil communicating with the first oil chamber is provided between the upper surface of the inner sleeve and the skirt portion of the inner piston. A chamber is formed, the second oil chamber is arranged above the piston pin, and a stopper ring that is located below the piston pin and screwed into the skirt portion of the piston body is provided. Variable compression ratio device for an internal combustion engine via the stopper ring, characterized in that the engagement of the inner sleeve.