JPH0426669Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable compression ratio mechanism for a reciprocating piston type internal combustion engine.

[Prior Art] A variable compression ratio mechanism for a reciprocating piston internal combustion engine is already known, which improves output and fuel efficiency and prevents knocking by varying the compression ratio according to engine operating conditions. ing. Conventionally known variable compression ratio mechanisms include an eccentric bearing provided on the shaft support between the connecting rod and the crankshaft or between the connecting rod and the piston pin, and this eccentric bearing is locked. The eccentric bearing is provided with a means to lock the eccentric bearing in two stages: a locked position (high compression ratio) and a freely rotating position (low compression ratio), or it can be locked in two positions. have been proposed (Japanese Patent Application Laid-Open No. 58-38343, JP-A No. 58-172431).

[Problem that the invention attempts to solve]

In the conventional variable compression ratio mechanism described above, only two levels of compression ratio can be obtained, namely the locked position and the unlocked position of the eccentric bearing.In the present invention, the eccentric bearing can be locked in two or more positions, and the engine speed is improved. The purpose of the present invention is to enable the compression ratio to be controlled in three or more stages in order to more precisely adapt to various operating conditions.

[Means for solving problems]

According to the present invention, at least one of the shaft supports at both ends of a connecting rod of an internal combustion engine is provided with an eccentric bearing that makes the bearing hole of the connecting rod and the support shaft inserted through the bearing hole eccentric to each other. A hydraulic lock mechanism capable of fixing the eccentricity of the bearing at at least two positions in the rotational direction of the eccentric bearing is provided, and the hydraulic lock mechanism includes at least two locks provided on one of the connecting rod and the eccentric bearing. One to one hole and the lock hole provided on the other side.
each pair of lock holes and lock pins are arranged at intervals in the axial direction of the eccentric bearing;
At least one of the lock hole and the lock pin is arranged at intervals in the circumferential direction, and a guide groove in the circumferential direction is provided on the side where the lock hole is provided, corresponding to each lock pin, and the guide groove is deep. The variable compression ratio of an internal combustion engine is characterized in that the compression ratio is gradually increased and connected to the lock hole, and the compression ratio is changed in at least three stages by selectively inserting and fixing each pair of the lock hole and the lock pin. A mechanism is provided.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, 1 is an engine cylinder, 2 is a combustion chamber, 3 is a piston, 4 is a piston pin, 5 is a retaining ring for attaching the piston pin to the piston, and 6 is a connecting rod. An eccentric bearing 7 is inserted and fitted into the bearing hole 6a at the small end of the connecting rod 6, and the piston pin 4 is inserted into the eccentric bearing 7.
Insert into the inner diameter of the The eccentric bearing 7 is arranged in two directions in the circumferential direction by lock pins 11 and 21, as will be described in detail below.
Bearing hole 6a of connecting rod 6 in one position
It has become locked against the

2 and 4 are sectional views taken along line AA in FIG. 1, and FIGS. 3 and 5 are sectional views taken along line BB in FIG. 1. At the small end of the connecting rod 6, hydraulic chambers 12 and 22 for sliding the lock pins 11 and 21 are formed so as to open into the bearing hole 6a in the radial direction of the eccentric bearing 7. Lock pins 11 and 21 are slidably fitted into chambers 12 and 22, respectively. Although the two lock pins 11 and 21 are shown at the same position in the circumferential direction in FIG. 1 for convenience, in reality they are spaced apart at a predetermined angle as shown in FIGS. It is located.
The lock pins 11 and 21 are also spaced apart from each other in the axial direction XX, as shown in FIGS. 1 and 6.

On the outer periphery of the eccentric bearing 7, circumferential guide grooves 13 are provided at axial positions corresponding to the lock pins 11 and 21.
23 is provided. These guide grooves 13 and 23 gradually become deeper in the circumferential direction, and the lock hole 1
It ends at the 4,24 position. These grooves 1
3 and 23 are out of phase with each other in the circumferential direction,
Therefore, the positions of the lock holes 14, 24 are also shifted from each other in the circumferential direction. In addition, these guide grooves 13, 2
Reference numeral 3 also serves as an oil passage, and is communicated with oil passages 15 and 25 formed longitudinally inside the connecting rod 6, respectively. Further, the lower end portions of the hydraulic chambers 12 and 22 communicate with oil passages 16 and 26 inside the connecting rod 6, respectively.

Each oil passage 1 inside the connecting rod 6
5, 16 and 25, 26 are connected to appropriate hydraulic control valves (not shown), oil pumps (not shown), and oil reservoirs (not shown) through oil passages provided in the crankshaft (not shown). It is connected to the. Such an oil system can be constructed, for example, by providing a plurality of oil systems as shown in the above-mentioned Japanese Patent Application Laid-Open No. 172431/1983.

When a high compression ratio is to be set depending on the operating conditions of the engine, hydraulic pressure is supplied from the oil passage 16 to the hydraulic chamber 12, the lock pin 11 is raised, and the lock pin 11 is inserted into the guide groove 13. Since the eccentric bearing 7 tends to rotate due to the force generated between the piston pin 4 and the connecting rod 6 due to the movement of the piston 3, the lock pin 11 is rotated by the force generated between the piston pin 4 and the connecting rod 6.
3 and moves relatively toward the lock hole 14, and finally fits into the lock hole 14. This results in
The eccentric bearing 7 is located in the bearing hole 6 of the connecting rod 6.
A is locked in the position shown in FIG. In this position, as is clear from FIG. 2, the thick side of the eccentric bearing 7 is located on the lower side, and the piston pin 4 and crankshaft (crank pin part) (not shown)
Fix it to the state that maximizes the distance between the axes.
Therefore, a constant high compression ratio can be obtained. Note that the oil in the guide groove 13 is returned through the oil passage 15. Further, in this state, the lock pin 21 is retracted into the hydraulic chamber 22, as shown in FIG.

If you are trying to set a medium compression ratio depending on other operating conditions of the engine, oil passage 1
5 to the guide groove 13 to lock the lock pin 1.
1 is returned to the hydraulic chamber 12 side to release the lock, and at the same time, hydraulic pressure is supplied from the oil passage 26 to the hydraulic chamber 22, and the lock pin 21 is raised and placed into the guide groove 23. The lock pin 21 is connected to the guide groove 23 as described above.
is guided into the lock hole 24, and the eccentric bearing 7
Lock it in the position shown in FIG. In this position, as shown in FIG. 5, the thick and thin parts of the eccentric bearing 7 are on the lateral sides. That is, the axes of the inner diameter and outer diameter of the eccentric bearing 7 are located at substantially the same position in the vertical direction. A moderately constant compression ratio is thus obtained.

Next, when setting a low compression ratio, hydraulic pressure is supplied from the oil passage 25 to the guide groove 23, and the lock pin 21 is returned to the hydraulic chamber 22 side to release the lock. At this time, both the lock pins 11 and 21 are retracted into their respective hydraulic chambers 12 and 22,
The eccentric bearing 7 can freely rotate within the bearing hole 6a at the small end of the connecting rod 6. During the compression stroke of the engine, a strong force is applied to push the piston 3 downward, so that the thin walled portion of the eccentric bearing 7 is positioned downward. Therefore, the piston pin and crankshaft (crank pin part)
(not shown). Therefore,
A constant low compression ratio is obtained.

In the above-described embodiment, it is also possible to change the compression ratio in four or more stages by increasing the number of lock pins and associated hydraulic chambers, oil passages, etc. Further, in the above embodiment, the eccentric bearing 7 is provided on the small end side of the connecting rod 6, that is, on the shaft support of the piston pin 4, but on the large end side, that is, on the shaft of the crankshaft (not shown). It may be provided that the eccentric bearing can be locked in at least two circumferential positions relative to the branch. Furthermore, eccentric bearings are provided on the shaft supports at both ends of the connecting rod, and by appropriately selecting the locking positions of these eccentric bearings, the compression ratio can be varied in multiple stages. In this case, it is convenient that the amounts of eccentricity of both eccentric bearings are different from each other.

Although the locking pins 11 and 21 are hydraulically actuated, the retraction of these locking pins from their respective locking holes may be effected by suitable springs (not shown). Further, in the above embodiment, the lock pins 11 and 21 and the lock hole 1
Although both of Nos. 4 and 24 are arranged at intervals in the circumferential direction, either one may be arranged at the same position and only the other is arranged at intervals in the circumferential direction.

[Effect of idea]

As described above, according to the present invention, the compression ratio can be changed in multiple stages with a simple lock structure. In addition, since the locking position of the eccentric bearing 7 can be freely selected, one or more compression ratios intermediate between the high compression ratio and the low compression ratio can be arbitrarily set to suit the usage conditions of a specific engine. can be determined. Further, in the present invention, each set of lock holes and lock pins is arranged at intervals in the axial direction of the eccentric bearing, and at least one of the lock holes and lock pins is arranged at intervals in the circumferential direction. Therefore, by selectively inserting any one lock pin into the corresponding lock hole, or by not inserting any lock pin into the lock hole, not only more stages of compression ratio can be obtained. Since each set of locking hole and locking pin is independent, the locking action can be reliably performed, and there is an advantage that the timing of the locking action can be performed regardless of the stroke of the engine.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the variable compression ratio mechanism of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 1 and shows the locked state of one lock pin, and FIG. -B sectional view, the eccentric bearing is at the same position in the circumferential direction as in Fig. 2, and shows the other lock pin in the unlocked state, and Fig. 4 is the 2nd view when one lock pin is in the unlocked position. Figure 1A corresponds to
-A sectional view, Figure 5 is Figure 1 B-B corresponding to Figure 3 when the other lock pin is in the locked position
The sectional view, FIG. 6, is a sectional view taken along line CC in FIG. 4... Piston pin, 6... Connecting rod, 7... Eccentric bearing, 11, 12... Lock pin, 12, 22... Hydraulic chamber, 13, 23... Guide groove, 14, 24... Lock hole , 15, 16, 2
5, 26...Oil passage.

Claims (1)

[Scope of utility model registration request] An eccentric bearing is provided on at least one of the shaft supports at both ends of a connecting rod of an internal combustion engine to make the bearing hole of the connecting rod and the support shaft inserted through the bearing hole eccentric with respect to each other, and the amount of eccentricity of the eccentric bearing is adjusted to A hydraulic locking mechanism capable of fixing the eccentric bearing in at least two positions in the rotational direction is provided, and the hydraulic locking mechanism includes at least two locking holes provided in one of the connecting rod and the eccentric bearing, and in the other. and lock pins that correspond one-to-one to the lock holes and are insertable into each set, and each pair of lock holes and lock pins are arranged at intervals in the axial direction of the eccentric bearing, and the lock holes and lock pins of each set are arranged at intervals in the axial direction of the eccentric bearing. At least one of the lock pins is arranged at intervals in the circumferential direction, and a guide groove in the circumferential direction is provided corresponding to each lock pin on the side where the lock hole is provided, and the guide groove has a depth that gradually increases. A variable compression ratio mechanism for an internal combustion engine, wherein the variable compression ratio mechanism is enlarged and connected to the lock hole, and selectively inserts and fixes each pair of the lock hole and the lock pin to change the compression ratio in at least three stages.