JPH0422717A - Compression ratio varying device of internal combustion engine - Google Patents

Abstract

PURPOSE:To make stable changing-over of the compression ratio by constructing a compression ratio varying mechanism in which an eccentric sleeve is interposed between a crank shaft and a connecting rod, and furnishing this compression ratio varying mechanism with a phase control means to control the phase of the eccentric sleeve through a phase holding means. CONSTITUTION:An eccentric sleeve 2 is interposed between a crank pin 6a on a crank shaft 6 and the major dia. end of a connecting rod 7 in such a way as rotatable relatively to them, and on one of the end faces of this sleeve 2, No.1 sprocket 9 is formed consolidatedly between this and the end face of a crank arm 6b. A phase holding means 3 is composed of, besides this No.1 sprocket 9, a No.2 sprocket 10, chain 11 and shaft 12, and is connected with a phase control means 4 consisting of a No.3 sprocket 14, No.4 sprocket 15, chain 16, and revolution control device 17. This revolution control device 17 is composed of a stepping motor, controller, etc., and arranged so as to control the revolving angle of the No.4 sprocket 15 in accordance with the engine load, revolving speed, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a variable compression ratio mechanism for an internal combustion engine that can change the compression ratio depending on operating conditions.

(Prior Art) Conventionally, a crankshaft of an internal combustion engine and a connecting rod (
An eccentric sleeve is interposed between the connecting rod (hereinafter simply referred to as the connecting rod), and by changing the phase of the eccentric sleeve with respect to the connecting rod, the relative position of the piston to the cylinder can be changed, and the compression ratio of the engine can be changed. There is a compression ratio mechanism.

This variable compression ratio mechanism includes a hydraulic lock pin that is retracted from the connecting rod side toward one of a plurality of engaging portions formed at predetermined positions on the outer periphery of the eccentric sleeve. The eccentric sleeve is rotated by a rotational force generated by the eccentricity of the load from the piston and the reaction force from the crankshaft. The eccentric sleeve cannot rotate relative to the connecting rod when the lock pin is engaged with the retaining portion, and is rotatable when the lock pin is disengaged from the engaging portion. By recessing the lock pin 8, it is possible to selectively change the engaging portion with which the lock pin engages, thereby selectively changing the rotation angle, that is, the phase, of the eccentric sleeve relative to the connecting rod. Therefore, the compression ratio is selectively variable.

The compression ratio is increased in the low load range and low rotation range of the engine. This improves thermal efficiency and fuel consumption. On the other hand, the compression ratio is reduced in the high load region and high rotation region of the engine. Thereby, it is possible to prevent knocking that occurs due to relatively high temperatures and pressures during compression.

(Problem to be Solved by the Invention) However, in the conventional variable compression ratio mechanism for an internal combustion engine, when changing the engagement portion with which the lock pin engages,
Since the eccentric sleeve is rotated by the rotational force generated by the eccentricity of the load from the piston and the reaction force from the crankshaft, the frictional force of the eccentric sleeve, the reciprocating inertia of the piston, the pressure inside the cylinder, etc. This greatly affects the rotation of the sleeve, making the behavior (rotation) of the eccentric sleeve unstable when changing the compression ratio. Further, since the lock pin is moved in and out by hydraulic pressure, it is necessary to form a groove on the bearing surface of the eccentric sleeve as an oil passage for the working oil, which increases the bearing surface pressure of the eccentric sleeve and reduces lubricity. moreover,
Since the compression ratio is selected by engaging the lock pin with the engagement part, it is not possible to change the compression ratio to a value other than the preset compression ratio.
There are problems such as the inability to precisely control the compression ratio.

The present invention was made in order to solve the above-mentioned problems, and it is possible to stabilize the switching of the compression ratio, change the compression ratio continuously, and furthermore, it does not require an oil passage for the hydraulic oil. The object of the present invention is to provide a variable compression ratio mechanism for an internal combustion engine that does not require a variable compression ratio mechanism.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, there is a gap between the crank pin between each crank arm of the crankshaft and the large end of the connecting rod that connects the crank pin and the piston. In the variable compression ratio mechanism, an eccentric sleeve that can rotate relative to the crank pin and the connecting rod is interposed, and the compression ratio of the engine is changed by changing the phase of the eccentric sleeve with respect to the connecting rod. Regardless, the phase holding means includes a phase holding means for keeping the phase of the eccentric sleeve constant with respect to the connecting rod, and a phase control means for controlling the phase of the eccentric sleeve via the phase holding means, and the phase holding means , a first sprocket formed between an end surface of the eccentric sleeve and an end surface of the crank arm, the first sprocket rotating integrally with the eccentric sleeve and concentric with the fine center of the crank pin; and a crank journal of the crankshaft. a second sprocket that is meticulously arranged to be relatively rotatable on the crank journal and has the same number of teeth as the first sprocket; a chain-shaped sprocket that interlocks the first sprocket and the second sprocket; The phase control means includes a third sprocket that is disposed axially outside the crankshaft and rotates integrally with the second sprocket, and a third sprocket that rotates the third sprocket. This configuration includes a rotation control device that controls this phase.

(Operation) When the rotation control device is stopped, the third sprocket is rendered unrotatable, and therefore the second sprocket that rotates integrally therewith is also rendered unrotatable. When the crankshaft rotates, the crank pin revolves around the crankshaft, and the first sprocket also revolves around the second sprocket. The second sprocket is not rotatable, and the number of teeth on the first sprocket and the second sprocket are set to be the same, so
The first sprocket rotates once around the crank pin in a direction opposite to the direction of revolution during the - revolution. Therefore,
The eccentric sleeve, which rotates integrally with the first sprocket, maintains a constant phase with respect to the connecting rod regardless of rotation of the crankshaft, and the engine is operated at a predetermined compression ratio.

In this state, when the rotation control device rotates the third sprocket, the rotation is in the order of third sprocket → second sprocket → chain-like member → first sprocket → eccentric sleeve. This changes the phase of the eccentric sleeve, that is, the compression ratio of the engine. The eccentric sleeve then rotates once around the crank pin for each revolution around the second sprocket while maintaining this changed phase, and the engine is operated with the changed compression ratio.

The rotation control device can rotate the third sprocket by a desired rotation angle, and can continuously set the compression ratio to a desired value.

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

FIG. 1 shows an embodiment of a variable compression ratio mechanism for an internal combustion engine to which the present invention is applied. The variable compression ratio mechanism 1 is composed of an eccentric sleeve 2, a phase holding means 3, a phase control means 4, and the like. The eccentric sleeve 2 is a cylindrical bearing member formed by making the axis of the outer circumferential surface 2b eccentric with respect to the axis of the inner circumferential surface 2a. 7a, and is interposed so as to be relatively rotatable thereto. Further, a first sprocket 9, which will be described later, is integrally formed on one end surface of the eccentric sleeve 2 between it and the end surface of the crank arm 6b.

The phase holding means 3 includes a first sprocket 9, a second sprocket 10, a chain 11, a shaft 12, and the like. The first sprocket 9 is rotatably attached to the crank pin 6a, and its axis is arranged concentrically with the axis of the crank pin 6a. This sprocket 9 is integrally formed with one end surface of the eccentric sleeve 2 and rotates integrally therewith. Both ends 12a of the shaft 12.

Each of the sprockets 12b has a reduced diameter by forming a stepped portion (not shown), and the mounting position of each sprocket 9, 10 is determined as will be described later. This shaft 12 has a threaded groove carved into one end 12a, and the crankshaft 6
is inserted into the crank journal 6c of the
a extends from the end face 6d of the crankshaft 6, and the other end] and 2b extend to a position corresponding to the first sprocket 9. That is, the crank journal 6C has a hole 6e along the axis and having a larger diameter than the shaft 12.
The shaft 12 is inserted into the hole 6e and supported by a bearing (not shown) so as to be relatively rotatable. Therefore, even when the crankshaft 6 rotates, the shaft 12 can rotate relative to the crankshaft 6 and maintain a stopped state.

The second sprocket 10 is set to have the same diameter and number of teeth as the first sprocket 9. Further, the sprocket 10 has the other end 12b1 of the shaft 12.
That is, it is positioned and fixed by the stepped portion of the shirt h12 at a position facing the first sprocket 9 and having the same axis as the crank journal 6C, and rotates integrally therewith.

The sprocket 10 is interlocked with the first sprocket 9 via the chain 11. In addition, chain 11
A timing belt, wire, etc. may be used instead.

The phase control means 4 includes a third sprocket 14, a fourth sprocket 15, a chain 16, a rotation control device 17, and the like. The third sprocket 14 is arranged on the axially outer side of the crankshaft 6. That is,
The shaft 1 is inserted into one end 1, 2a of the shaft I2.
It is positioned by the stepped portion of No. 2 and fixed by screwing with a nut 19. Therefore, the third sprocket 14 rotates integrally with the shaft 12 and the second sprocket 10. The fourth sprocket 15 is attached to the engine main body side, and more specifically to the output shaft of a rotation control device 17, which will be described later. The fourth sprocket 15 is interlocked with the third sprocket 14 via a chain 16. Note that a timing belt, wire, or the like may be used instead of the chain 16.

The rotation control device 17 includes, for example, a stepping motor and a controller (both not shown), and is attached to the engine body, for example, a cylinder block. This controller supplies a control signal to the stepping motor according to the engine load, engine speed, etc., and rotates the stepping motor by a desired rotation angle in the forward or reverse direction.

The action will be explained below.

Since the eccentric sleeve 2 has an eccentric inner and outer circumferential surface, the mounting position of the connecting rod to the crank pin can be changed by changing the phase.
The relative position of the piston with respect to the cylinder, ie the amount of stroke, can be changed. Figure 2 shows the case where the thick part of the eccentric sleeve 2 (point A in the figure) is located on the lower side.
It is shown every 90 degrees of crank angle. In this case, the position of the piston relative to the cylinder at the top dead center and bottom dead center of the piston shifts downward, and as the cylinder volume at the piston bottom dead center increases, the volume of the combustion chamber at the piston top dead center also increases. The compression ratio decreases to the value ε. On the other hand, FIG. 3 shows the case where point A of the eccentric sleeve 2 is located on the upper side at every 90 degrees of crank angle.

In this case, the position of the piston relative to the cylinder at the top dead center and bottom dead center of the piston shifts upward, and as the cylinder volume at the piston bottom dead center decreases, the volume of the combustion chamber at the piston top dead center also decreases. The compression ratio increases to a value εH (ε□〉εL).

When the stepping motor is stopped, the fourth sprocket 15 of the phase control means 4 cannot rotate, and the third sprocket 1 interlocked with the fourth sprocket 15
4 is also said to be unable to rotate.

Therefore, the shaft 12, which is relatively rotatably supported by the crankshaft 6, is not rotatable regardless of the rotation of the crankshaft 6, and the second sprocket 10 is also not rotatable.

The crankshaft 6 rotates and the crank journal 6c
When the crank pin 6a revolves around the axis, the first sprocket 9 revolves around the second sprocket 10, as shown in FIG.

The number of teeth on each sprocket 9 and 10 is set to be the same, and since the second sprocket 10 is not rotatable, the first sprocket 9 rotates once in the direction of arrow C in the figure. It rotates in the direction opposite to the revolution direction (in the direction of arrow CC in the figure). Therefore, the phase of the first sprocket 9, that is, the eccentric sleeve 2, with respect to the connecting rod 7 is held constant, and the engine is operated with the compression ratio ε.

The rotation control device 17 changes the compression ratio of the engine. To be more specific, if the stepping motor rotates, for example, by 180 degrees from the state shown in FIG. -> second sprocket 10 -> first timing belt 11 -> first sprocket 9, and the first sprocket 9, that is, the eccentric sleeve 2, is rotated and its phase changes by 180 degrees (third figure). The eccentric sleeve 2 maintains the changed phase regardless of the rotation of the crankshaft 6,
The engine is operated at the compression ratio εH.

Since the stepping motor can rotate the fourth sprocket 15 by a desired angle, the phase of the eccentric sleeve 2 changes continuously to obtain a desired compression ratio between compression ratios ε□ and ε. be able to.

Furthermore, since the eccentric sleeve 2 is rotated by the phase control means 4 via the phase holding means 3 and its phase changes,
Unlike conventional variable compression ratio mechanisms, hydraulic oil is not required, and an oil groove through which the hydraulic oil passes can be omitted on the bearing surface of the eccentric sleeve.

In addition, to install a variable compression ratio mechanism on multiple cylinders,
As shown in FIG. 4, a phase holding means 3B is formed on the other end surface 2d of an eccentric sleeve 2 having a phase holding means 3A formed on one end surface 2C. What is necessary is to connect it to the phase holding means 3C formed at 2C.

Specifically, first sprockets 9A and 9B are integrally formed on both end surfaces of the eccentric sleeve 20, and second sprockets IOA and IOB are interlocked with the respective sprockets 9A and 9B by chains 11A and 11B, respectively. ing. One second sprocket IOA is connected via a shaft 12A to a third sprocket 14A, that is, the phase control device 4, and the other second sprocket IOA
B is connected to the second sprocket IOC of the phase holding means 3C formed on one end surface of the adjacent eccentric sleeve 2 via the shaft 12B.

When the eccentric sleeve 2 is rotated by the phase control device 4 via the phase holding means 3A, this rotation is performed from the first sprocket 9B to the second sprocket IOB to the shaft 12.
B → second sprocket 9B → first sprocket 9C
→The signal is transmitted to the adjacent eccentric sleeves 2 in this order, and each eccentric sleeve 2 rotates at the same time to change the phase.

(Effects of the Invention) As described above, according to the present invention, there is provided a phase holding means for keeping the phase of the eccentric sleeve with respect to the connecting rod constant regardless of the rotation of the crankshaft, and a phase holding means for keeping the phase of the eccentric sleeve constant with respect to the connecting rod; 4. The phase holding means is formed between an end face of the eccentric sleeve and an end face of the crank arm and rotates integrally with the eccentric sleeve, and a first sprocket concentric with the sprocket of the crankshaft; a second sprocket having the same number of teeth as the first sprocket; and a second sprocket, and the phase control means includes a third sprocket that is disposed on the axially outer side of the crankshaft and rotates integrally with the second sprocket. , is equipped with a rotation control device that rotates the third sprocket and controls the phase thereof, so that switching of the compression ratio can be stabilized and the compression ratio can be continuously changed, and further, This has excellent effects such as being able to omit the hydraulic oil passage, increasing the bearing surface pressure of the eccentric sleeve, and improving the lubrication performance.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a sectional view showing an embodiment of a variable compression ratio mechanism for an internal combustion engine to which the present invention is applied, and FIGS. Fig. 2 is a schematic diagram of the configuration in a low compression ratio state, Fig. 3 is a schematic diagram of the configuration in a high compression ratio state, and Fig. 4 is a diagram showing the rotation state of the variable compression ratio mechanism according to the present invention. FIG. 2 is a sectional view of main parts of a multi-cylinder engine. 1... Variable compression ratio mechanism, 2... Eccentric sleeve, 3...
... Phase holding means, 4... Phase control means, 6... Crankshaft, 7... Connecting rod, 7a... Big end, 9... First sprocket, 10... Second sprocket, 11...timing belt, 12...
Shaft, 14...Third sprocket, 17...
Rotation control device. Applicant Mitsubishi Motors Corporation Agent Patent Attorney Kanji Nagato Figure 2 Figure 3

Claims (1)

[Claims] An eccentric sleeve rotatable relative to the crank pin and the connecting rod is interposed between the crank pin between each crank arm of the crankshaft and the large end of the connecting rod connecting the crank pin and the piston. In the variable compression ratio mechanism that changes the compression ratio of the engine by changing the phase with respect to the connecting rod, a phase holding means maintains a constant phase of the eccentric sleeve with respect to the connecting rod regardless of rotation of the crankshaft. , a phase control means for controlling the phase of the eccentric sleeve via the phase holding means, the phase holding means being formed between an end surface of the eccentric sleeve and an end surface of the crank arm, rotates as one,
and a first sprocket that is concentric with the axial center of the crank pin, the axial center of the crank journal of the crankshaft is the same as that of the crank journal, and the first sprocket has the same number of teeth as the number of teeth of the first sprocket. a second sprocket of a number, the first sprocket and the second sprocket;
a third sprocket that is arranged on the axially outer side of the crankshaft and rotates integrally with the second sprocket; A variable compression ratio mechanism for an internal combustion engine, comprising a rotation control device that rotates a third sprocket and controls the phase thereof.