JPH0443829A - Variable compression ratio mechanism for internal combustion engine - Google Patents

Abstract

PURPOSE:To continuously change compression ration by constituting the mechanism so that a rotationally moving body journaled between respective the other ends of a first and a second links to be relatively rotationally movable is rotationally moved, respectively interlocking with a first and a second sprockets. CONSTITUTION:A shaft 9 holds the phase of a first sprocket 3, namely an eccentric sleeve 2 constant, and the engine is operated with compression ratio epsilonH as it is. For changing compression ratio of the engine, the stepping motor of a rotational movement control device is operated. For example, in case of rotational movement of the stepping motor by 180 degree, this rotational movement is transmitted in the order as follows: the shaft 9 a second sprocket 10 a chain 21 a fourth and a third sprockets 17,16 (a rotational moving body 15) a chain 20 the first sprocket 3 the eccentric sleeve 2, and the phase of the eccentric sleeve 2 is changed by 180 degree. The changed phase of the eccentric sleeve 2 is held regardless of displacement of a connecting rod 7 and a piston 22 accompanied with rotation of a crankshaft, and the engine is operated with compression ratio epsilonL as it is.

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, an eccentric sleeve is interposed between a piston pin that pivotally supports a piston of an internal combustion engine and a connecting rod (hereinafter simply referred to as a connecting rod) that connects the piston pin to a crankshaft. A variable compression ratio mechanism is known that can change the compression ratio of an engine by changing the relative position of the piston in the stroke direction by changing the phase with respect to the connecting rod.

This variable compression ratio mechanism includes a hydraulic lock pin that is retracted from the hook 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 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 engaging portion, and is rotatable when the lock pin is disengaged from the engaging portion.

By moving the lock pin in and out, the engaging portion with which the lock pin engages can be selectively changed, and the rotation angle, that is, the phase, of the eccentric sleeve relative to the connecting rod can be selectively changed. 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. Furthermore, since the compression ratio is selected by engaging the lock pin with the engaging part, it is not possible to change the compression ratio to a value other than the preset compression ratio, and it depends on the engine load, engine speed, etc. hand,
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, between the piston pin that pivotally supports the piston and the small end of the connecting rod that connects the piston pin and the crankshaft,
In a variable compression ratio mechanism in which an eccentric sleeve that is relatively rotatable is interposed between the piston pin and the connecting rod and the compression ratio of the engine is changed by changing the phase of the eccentric sleeve, the end face of the eccentric sleeve and the peripheral wall of the piston A first sprocket that is concentric with the axis of the shaft hole of the small end of the connecting rod and rotates integrally with the eccentric sleeve is disposed between the sprockets, and
A support shaft means is provided radially outward of the crankshaft, and the support shaft means is formed on a shaft arranged parallel to the axis of the crankshaft and rotatably supported on the engine body side, and on the shaft. a second sprocket, a rotation control device that rotates the shaft to control the phase of the shaft; and further, the piston pin and the support shaft means are connected by a link means, the link means: a first link having one end relatively rotatably connected to the piston pin; a second link having one end relatively rotatably attached to the shaft; a relative link between the other ends of the first and second links; The rotating body is rotatably supported, and the rotating body is configured to rotate in conjunction with the first and second sprockets, respectively.

(Operation) The rotation control device in the stopped state makes the shaft of the support means unrotatable and the second sprocket unrotatable. The first link and the second link of the link means are connected to the piston pin and the shaft so as to be relatively rotatable, respectively, and the first link and the second link are displaced so as to be bent at the rotating body part. Therefore, the link means moves the rotating body between the first sprocket and the second sprocket without interfering with the vertical movement (stroke) of the piston.

Since the first sprocket is interlocked with the second sprocket via this rotating body, the rotation angle, that is, the phase, of the first sprocket with respect to the stroke direction of the piston is as follows:
It is determined by the rotation angle of the shaft, regardless of the displacement of the connecting rod and piston due to the rotation of the crankshaft. Therefore, even if the crankshaft rotates and the connecting rod and piston are displaced, the phase of the first sprocket is maintained. Since the eccentric sleeve rotates integrally with the first sprocket, the phase of the piston relative to the strobe is kept constant regardless of the displacement of the connecting rod and piston due to rotation of the crankshaft, and therefore the engine maintains a predetermined compression ratio. It is operated as it is.

From this state, when the rotation control device rotates the shaft, the 20 rotations are from the second sprocket to the rotating body to the first sprocket.
It is transmitted in the order of sprocket → eccentric sleeve, and the phase of the eccentric sleeve, that is, the compression ratio of the engine changes. The eccentric sleeve is then maintained in this changed phase, and the engine is operated with the changed compression ratio.

The rotation control device can rotate the shaft 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.

FIGS. 1 and 2 show an embodiment of a variable compression ratio mechanism for an internal combustion engine to which the present invention is applied, and the variable compression ratio mechanism l is
It is composed of an eccentric sleeve 2, a first sprocket 3, a support shaft means 4, a link means 5, and the like. Eccentric sleeve 2
is a cylindrical bearing member formed by eccentrically centering the axis of the outer circumferential surface 2b with respect to the axis of the inner circumferential surface 2a;
The connecting rod 7 is interposed between a piston pin 23 that pivotally supports the connecting rod 7 and the small end 7a of the connecting rod 7 so as to be able to rotate relative thereto. Further, a first sprocket 3 is integrally formed on one end surface of the eccentric sleeve 2 between it and the peripheral wall 22a of the piston 22. The first sprocket 3 is rotatably attached to the piston pin 23, and its axis is arranged to be concentric with the axis of the shaft hole of the small end 7a of the connecting rod 7.

The support shaft means 4 is composed of a shaft 9, a second sprocket lO, a rotation control device (not shown), etc., and is arranged radially outward of the crankshaft (not shown) so as not to interfere with the rotation of the crankshaft. It is set up. The shaft 9 is disposed parallel to the axis of the crankshaft, is rotatably supported on the engine body side, for example, a cylinder block, and is rotated and its phase is controlled by a rotation control device, which will be described later.

The second sprocket 10 is formed at a predetermined position on the shaft 9, specifically at approximately the same position in the axial direction of the crankshaft as the first sprocket 3, and rotates together with the shaft 9.

The rotation control device 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 control signals to the stepping motor according to engine load, engine speed, etc.
The shaft 9 is rotated by a desired rotation angle in the forward or reverse direction via the stepping motor.

The link means 5 includes a first link 13 and a second link 14.
and a rotating body 15, etc., and are arranged so as not to interfere with the crankshaft and the connecting rod 7. Rotating body 15
consists of a third sprocket 16 and a fourth sprocket 17 that are integrally formed, and these sprockets 16.
17 is link 13. which will be described later. l4 swinging ends 13b, 14
The frame is rotatably supported by a pin 18 that is passed between b.

The third sprocket 16 is set to have the same number of teeth and diameter as the first sprocket 3. This third sprocket 16 interlocks the first sprocket 3 via a chain 20. Further, the fourth sprocket 17 is set to have the same number of teeth and diameter as the second sprocket IO. and,
This fourth sprocket 17 is interlocked with the second sprocket 10 via a chain 21.

Note that a timing belt, wire, or the like may be used in place of the chains 20 and 21 described above. Also, each link 13
．． A gear may be rotatably disposed in the middle of the sprocket 14, and the third sprocket 16 and the first sprocket 3 and the fourth sprocket 17 and the second sprocket 10 may be linked by the gear, respectively.

The first link 13 has a so-called I-arm shape, and bearing holes are formed at both ends thereof. One end 13a of the link 13 is connected to the piston pin 23 so as to be relatively rotatable. The second link 14, as shown in FIG.
Two proximal ends 14a are formed by bifurcating along the axial direction of the shaft 9.

14a, and each base end 14a is externally fitted onto the shaft 9 so as to be relatively rotatable.

The action will be explained below.

Since the inner peripheral surface 2a and outer peripheral surface 2b of the eccentric sleeve 2 are eccentric, the mounting position of the piston pin 23, that is, the piston 22 to the connecting rod 7 can be changed by changing the phase, and the position of the piston pin 23, that is, the piston 22 can be changed in the stroke direction. The relative position of the piston, that is, the stroke amount of the piston can be changed. Specifically, as shown in FIG. 2, when the thick inner portion of the eccentric sleeve 2 (triangle A in the figure) is positioned on the lower side, the piston pin 23 is positioned upward relative to the small end 7a of the connecting rod 7. bias towards For this reason,
Piston 22 at top dead center and bottom dead center of piston 22
The position of the piston 22 relative to the cylinder is biased upward, and the piston 22
As the cylinder volume at the bottom dead center of the piston 22 decreases, the combustion chamber volume at the top dead center of the piston 22 also decreases, and the compression ratio increases to a value εH.

On the other hand, as shown in FIG.
When the small end 7 of the connecting rod 7 is positioned on the upper side,
The crank bin 23 is biased downward with respect to a. Therefore, the position of the piston 22 relative to the cylinder at the top dead center and the bottom dead center of the piston 22 shifts downward, and as the cylinder volume at the bottom dead center of the piston 22 increases, the combustion chamber at the top dead center of the piston 22 increases. The volume also increases and the compression ratio decreases to the value εL (ε1 minus ε8).

The first link 13 of the link means 5 is connected to the piston pin 23 and the rotating body 15, and the second link 14 is connected to the rotating body 15 and the shaft 9 so as to be relatively rotatable. FIGS. 2 to 5 sequentially show the rotational states of the variable compression ratio mechanism 1 at every 90 degrees of crank angle, in which the crankshaft rotates and the piston 22 (a piston pin 23 is shown instead) moves during the stroke. In this case, the crank pin 6a to which the large end 7b of the connecting rod 7 is connected is aligned with the axis of the crankshaft (0 in the figure).
point), and the locus of the center of the crank bin 6a becomes circle B in the figure. The link means 5 is displaced so that the first link 13 and the second link 14 are bent at the rotating body 15, and allows the rotation of the shaft 9 without interfering with the rotation of the crankshaft and the stroke of the piston 22. It can be transmitted to the first sprocket 3. That is, the first sprocket 3 connects to the third sprocket 16 via the chain 20, and the fourth sprocket 17, which rotates together with the third sprocket 13, connects to the second sprocket 16 via the chain 2.
The sprockets 10 are interlocked with each other.

At this time, the fourth sprocket 17 is set to have the same number of teeth and diameter as the second sprocket 10, and the rotation angle of the second sprocket 10 remains the same as that of the fourth sprocket 17. The rotation angle is . Further, the third sprocket 16 is set to have the same number of teeth and diameter as the first sprocket 3, and the rotation angle of the third sprocket 16 remains the same as the rotation angle of the first sprocket 3. The angle of movement. Therefore, the phase of the first sprocket 5 with respect to the stroke direction of the piston is determined by the rotation angle of the shaft 9, regardless of the rotation of the crankshaft and the stroke of the piston 22. When the stepping motor is stopped, the shaft 9 of the support shaft means 4 cannot rotate. Therefore, this shaft 9
The phase of the first sprocket 3, that is, the eccentric sleeve 2, is held constant, and the engine is operated with the compression ratio ε unchanged.

In this state, to change the compression ratio of the engine, the stepping motor of the rotation control device is operated.

For example, if the stepping motor rotates by 180 degrees, this rotation will move from shaft 9 to second sprocket 10 to
Chain 21 → 4th and 3rd sprocket 17.16
(Rotating body 15) → Chain 20 → First sprocket 3
→The signal is transmitted to the eccentric sleeve 2, and the phase of the eccentric sleeve 2 changes by 180 degrees (Fig. 6). The eccentric sleeve 2 maintains the changed phase regardless of the displacement of the connecting rod 7 and piston 22 due to rotation of the crankshaft, and the engine is operated at the compression ratio ε.

Since the stepping motor can rotate the shaft 9 by a desired angle, the phase of the eccentric sleeve 2 changes continuously, and a desired compression ratio can be obtained between compression ratios εH and εL.

In addition, since the phase of the eccentric sleeve 2 is changed by the support shaft means 4 via the link means 5, there is no need for working oil as in conventional variable compression ratio mechanisms. The oil groove through which the oil passes can be omitted.

In this embodiment, the axial center of the first sprocket 3 was set to be concentric with the axial center of the shaft hole of the small end 7a of the connecting rod 7, but the invention is not limited to this. It may also be set to be concentric with the axis. In this case, when the thick portion of the eccentric sleeve is positioned upward, the compression ratio of the engine increases, and when the inner thick portion of the eccentric sleeve is positioned downward, the compression ratio of the engine decreases.

In addition, to install a variable compression ratio mechanism on multiple cylinders,
A link means 5 may be provided for each cylinder, and each link means 5 may be connected to the support shaft means 4, respectively.

(Effects of the Invention) As explained above, according to the present invention, there is a space between the end face of the eccentric sleeve and the circumferential wall of the piston, which is concentric with the axis of the shaft hole of the small end of the connecting rod and integral with the eccentric sleeve. A first sprocket that rotates is disposed, and a spindle means is provided radially outward of the crankshaft, and the spindle means is disposed parallel to the axis of the crankshaft and rotates toward the engine body. A movably supported shaft, a second sprocket formed on the shaft, a rotation control device for rotating the shaft to control the phase of the shaft, and further linking the piston pin and the supporting shaft means. The link means includes a first link whose one end is relatively rotatably connected to the piston pin, a second link whose one end is relatively rotatably attached to the shaft, and the first and second links. A rotating body is rotatably supported between each other end of the link, and this rotating body rotates in conjunction with the first and second sprockets, so that switching of the compression ratio is possible. In addition to stabilization, the compression ratio can be changed continuously, and the oil passage for hydraulic oil can be omitted, increasing the bearing surface pressure of the eccentric sleeve and improving lubrication performance. It has a positive effect.

[Brief explanation of the drawing]

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. 2 to 5 are crank angles of 90 in a high compression ratio state as seen from the side of FIG. FIG. 6 is a schematic diagram showing the rotation state at each degree, and FIG. 6 is a schematic diagram showing the configuration in a low compression ratio state as viewed from the side of FIG. 1. l... variable compression ratio mechanism, 2... eccentric sleeve, 3...
...First sprocket, 4... Support shaft means, 5...
Link means, 7... connecting rod, 7a... small end,
9...Shaft, lO...Second sprocket, 1
3...First link, 14...Second link, 15
... Rotating body, 22 ... Piston, 22a ... Peripheral wall, 23 ... Piston pin. Figure 2! Figure 4 Figure 5

Claims (1)

[Claims] An eccentric sleeve rotatable relative to the piston pin and the connecting rod is interposed between a piston pin that pivotally supports the piston and a small end of a connecting rod that connects the piston pin and the crankshaft, and the phase of the eccentric sleeve is adjusted. In the variable compression ratio mechanism that changes the compression ratio of the engine by changing the compression ratio of the engine, the compression ratio is located between the end surface of the eccentric sleeve and the circumferential wall of the piston, and is concentric with the axis of the shaft hole of the small end of the connecting rod. A first sprocket that rotates integrally with the eccentric sleeve is provided, and a supporting shaft means is provided radially outward of the crankshaft, and the supporting shaft means is arranged parallel to the axis of the crankshaft. and a shaft rotatably supported on the engine main body side, a second sprocket formed on the shaft, a rotation control device for rotating the shaft to control the phase of the shaft, and further comprising: , the piston pin and the support shaft means are connected by a link means, the link means including a first link having one end relatively rotatably connected to the piston pin, and a first link having one end relatively rotatably attached to the shaft. 2 links, and a rotating body that is rotatably supported between the other ends of the first and second links, and the rotating body is interlocked with the first and second sprockets, respectively. A variable compression ratio mechanism for an internal combustion engine, which is characterized by rotating.