JPH048273Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable compression ratio mechanism for an internal combustion engine using an eccentric bearing, and particularly relates to a hydraulic passage structure for switching the compression ratio.

[Conventional technology]

One mechanism for varying the compression ratio in an internal combustion engine is to interpose an eccentric bearing between the piston pin and the connecting rod, and angularly displace the eccentric bearing to raise or lower the relative position of the piston to the connecting rod. There is a variable compression ratio mechanism that allows for variable settings.

As shown in FIGS. 2 and 3, a conventional variable compression ratio device using an eccentric bearing has an eccentric bearing 1 provided with a lock pin engagement hole 2, and a connecting rod 3 provided with a lock pin storage hole 4. Store the lock pin 5 in the lock pin storage hole 4,
By applying hydraulic pressure to the lock pin 5, the lock pin 5 is driven to advance and retreat in the direction of the engagement hole 2, thereby engaging and disengaging the lock pin 5 with the lock pin engagement hole 2. Ta.

The lock pin storage hole 4 includes a hydraulic passage 6 for locking the lock pin and a hydraulic passage 7 for unlocking the lock pin.
When the load is light, oil is forced into the lock pin lock hydraulic passage 6, the eccentric bearing 1 is locked, and a high compression ratio state is created. Also, during medium and high loads,
Oil is forced into the lock pin unlocking hydraulic passage 7, and the eccentric bearing 4 is unlocked.
A low compression ratio state is beginning to appear.

The hydraulic passage for locking the lock pin and the hydraulic passage for unlocking the lock pin are disclosed in, for example, Japanese Patent Application Laid-Open No. 58-91340.
As disclosed in the publication, it is connected to two independent oil grooves formed on the circumference of the crank pin bearing portion of the connecting rod. These two oil grooves are connected to the two oil grooves formed on the circumference of the bearing part of the crank journal via oil holes in the crankshaft.
Connected to two independent oil grooves. The two oil grooves of this bearing are connected to a low compression ratio control hydraulic passage and a high compression ratio control hydraulic passage formed in the cylinder block, respectively.

In the hydraulic passage of the variable compression ratio mechanism configured in this way, the oil holes in the crankshaft are connected to each oil groove in the bearing part of the crank journal and each oil groove in the crank pin bearing part in a half rotation range of the crankshaft. It has become possible to communicate with each other. The oil pumped into the oil groove of the crankpin bearing also acts as lubricating oil for the crankpin bearing.

[Problem that the invention attempts to solve]

However, with the above-mentioned hydraulic passage configuration, as the engine speed increases, the communication time between the oil groove and the oil hole in the crankshaft becomes shorter, resulting in an insufficient amount of lubricating oil supplied to the crankpin bearing. There was a risk of damage to the bearing. Therefore, there is a problem in that it is difficult to maintain a desired oil film on the upper and lower surfaces of the crank pin bearing, which are subject to particularly severe loads. Note that if oil grooves for lubricating oil are provided on the upper and lower surfaces of this crankpin bearing portion, the surface pressure in these portions will conversely increase, making it even more difficult to secure a desired oil film.

The present invention focuses on the above-mentioned problems, and aims to provide sufficient lubricating oil to the crank pin bearing of the connecting rod even when the engine is running at high speed. It is an object of the present invention to provide a hydraulic passage for a variable compression ratio mechanism that can maintain a desired value of compression ratio.

[Means for solving problems]

The hydraulic passages of the variable compression ratio mechanism of the present invention, which meet this purpose, include a hydraulic passage for low compression ratio control and a hydraulic passage for high compression ratio control, which are formed independently in the cylinder block, around the bearing part of the crank journal. The two oil grooves on the circumference of the bearing are connected to the eccentric bearing formed in the connecting rod through the oil hole in the crankshaft. In the hydraulic passages of the variable compression ratio mechanism connected to the two lock pin driving oil passages for hydraulically driving the engageable lock pins, a portion in the vertical direction on the circumference of the crank pin bearing portion of the connecting rod is In the position excluding
An oil groove connected to the lock pin driving oil passage is disposed on the circumference of the bearing portion of the crank journal, and the oil groove is connected to the upper and lower surfaces of the crank pin bearing portion of the connecting rod through the oil hole in the crankshaft. It consists of a lubricating oil groove for pumping lubricating oil.

[Effect]

In the hydraulic passage of the variable compression ratio mechanism configured in this way, oil is supplied to the crank pin bearing of the connecting rod from two systems: an oil groove for variable compression ratio and an oil groove exclusively for lubrication. Therefore, the amount of oil supplied to the crank pin bearing is significantly increased when the engine rotates at high speeds.

Since there are no oil grooves connected to the lock pin driving oil passage located in the vertical direction of the crank pin bearing of the connecting rod, the surface pressure on the upper and lower surfaces of the crank pin bearing, which is subject to severe loads, is kept at a moderate level. will be maintained. The oil pumped into the lubricating oil groove is then pumped through the oil hole in the crankshaft to the upper and lower surfaces of the crank pin bearing, so lubrication in this area is significantly improved and the oil film is maintained at the desired level. Ru.

Therefore, the crank pin bearing is always well lubricated, and damage caused by insufficient lubrication is reliably prevented.

〔Example〕

Hereinafter, preferred embodiments of the hydraulic passage of the variable compression ratio mechanism according to the present invention will be described with reference to the drawings.

FIG. 1 shows a hydraulic passage structure of a variable compression ratio mechanism according to an embodiment of the present invention. In the figure,
A piston 11 is slidably inserted into a cylinder 12, and the reciprocating motion of the piston 11 is converted into rotational motion of a crankshaft 15 via a piston pin 13 and a connecting rod 14.

Connecting rod 14 and piston pin 13
An eccentric bearing 16 whose inner and outer circumferences are mutually eccentric is interposed between the eccentric bearing 1 and
The compression ratio is changed according to the amount of rotation of 6. A lock pin engagement hole 17 extending in the radial direction is bored in the eccentric bearing 16, and a lock pin 18 is disposed on the connecting rod 14 side. The lock pin 18 is slidably housed in a lock pin housing hole 19, and is moved by the differential pressure between two hydraulic passages 20 and 21 formed in the connecting rod 14 for driving the lock pin. One hydraulic passage 20 is a hydraulic passage for locking a lock pin 18 to drive the lock pin 18 in the direction of the eccentric bearing 16, and the other passage 21
is a hydraulic passage for unlocking the lock pin that drives the lock pin 18 in a direction away from the eccentric bearing 16.

The lock pin locking hydraulic passage 20 and the lock pin unlocking hydraulic passage 21 communicate with mutually independent oil grooves 22 and 23 formed in the crank pin bearing portion 26 of the connecting rod 14, respectively. The oil grooves 22 and 23 can communicate with mutually independent oil grooves 28 and 29 formed on the circumference of the bearing portion 27 of the crank journal 25 via an oil hole 24 formed in the crankshaft 15. .

The oil hole 24 communicates the oil groove 22 and the oil groove 28 in the half rotation range of the crankshaft 15, and communicates the oil groove 23 and the oil groove 29 in the other half rotation range of the crankshaft 15. It's getting old.

The oil grooves 22 and 23 formed in the crank pin bearing portion 26 of the connecting rod 14 are not arranged in the vertical direction where the load is severe, but are arranged in the left and right direction where the load condition is relatively gentle. Also,
The oil grooves 28 and 29 formed in the bearing portion 27 of the crank journal 25 are also not arranged in the vertical direction, but are arranged in the left-right direction like the oil grooves 22 and 23.

On the circumference of the bearing part 27 of the crank journal 25, lubricating oil is pumped to the upper surface 26a and lower surface 26b of the crank pin bearing part 26 of the connecting rod 14 through the oil hole 24 in the crankshaft 15. Grooves 32, 33 are provided. That is, the upper surface 26a and the lower surface 26b of the crank pin bearing portion 26 are connected to the lubricating oil groove 3 through the oil hole 24.
It is possible to communicate with 2 and 33. Lubrication oil groove 3
2 is located at the upper part of the bearing part 27 of the crank journal 25, and the lubricating oil groove 33 is located at the upper part of the bearing part 27 of the crank journal 25.
It is located at the bottom of 7.

One of the oil grooves 28 for variable compression ratio
is connected to a high compression ratio control hydraulic passage 35 formed in the cylinder block 30, and the other oil groove 29 is connected to a low compression ratio control hydraulic passage 37 similarly formed in the cylinder block 30. ing. Oil pumped up from an oil pan 40 by an oil pump 41 is forced into the high compression ratio control hydraulic passage 35 and the low compression ratio control hydraulic passage 37 via a hydraulic switching valve 42. .

The lubricating oil grooves 32 and 33 are located in the cylinder block 3.
The lubricating oil passages 43 and 44 are connected to the hydraulic switching valve 42.
connected to the upstream side of the Thereby, the oil pumped by the oil pump 41 is always supplied to the lubricating oil grooves 32 and 33.

Next, the operation of the hydraulic passage of the variable compression ratio mechanism configured as described above will be explained.

Not shown when the engine is under light load
An activation signal is output from the ECU (electronic control unit) to the hydraulic switching valve 42, and the hydraulic switching valve 42 is switched to one side. As a result, the oil pumped up from the oil pump 41 is sent under pressure to the oil groove 28 via the hydraulic switching valve 42 and the high compression ratio control hydraulic passage 35.
Furthermore, pressure oil is intermittently sent from the oil groove 28 to the lock pin lock hydraulic passage 20 via the oil hole 24 of the crankshaft and the oil groove 22. Therefore, the lock pin 18 is engaged with the eccentric bearing 16 and a high compression ratio condition is created. Further, the pressure oil in the lock pin unlocking hydraulic passage 21 is supplied to the oil pan 4 through an oil groove 23, an oil hole 24, an oil groove 29, a low compression ratio control hydraulic passage 37, and an oil pressure switching valve 42.
Returned to 0.

When the engine is in a high load state, the hydraulic switching valve 42 is switched to the other side, and the oil flows through the hydraulic switching valve 42, the low compression ratio control hydraulic passage 37, the oil groove 29, the crankshaft oil hole 24, and the oil groove 23. The oil is then pressure-fed to the lock pin unlocking hydraulic passage 21. Therefore, the engagement between the lock pin 18 and the eccentric bearing 16 is released, and a low compression ratio state is created.

In this case, a portion of the oil discharged from the oil pump 41 is forced into the lubricating oil grooves 32 and 33 of the bearing portion 27 of the crank journal 25 through the lubricating oil passages 43 and 44. That is, while the oil pump 41 is in operation, oil is always being pumped into the lubricating oil grooves 32 and 33. Lubrication oil grooves 32, 33
can communicate intermittently with the upper surface 26a and lower surface 26b of the crankpin bearing section 26 through the oil hole 24 in the crankshaft 15, so that the oil pumped into the lubricating oil groove 33 is transferred to the upper surface 26a. The oil supplied and forced into the lubricating oil groove 32 is supplied to the lower surface 26b.

In this way, since both the variable compression ratio oil and the lubricating oil are supplied to the crankpin bearing portion 26, insufficient lubrication during high rotations is reliably prevented. Further, since the oil is directly pumped to the upper surface 26a and lower surface 26b, which have severe load conditions, it is possible to maintain the desired amount of oil film on these parts.

[Effect of idea]

As explained above, when using the hydraulic passage of the variable compression ratio mechanism of the present invention, the oil passage for driving the lock pin is connected to a position on the circumference of the crank pin bearing of the connecting rod except for the vertical part. A lubricating oil groove is provided on the periphery of the bearing part of the crank journal to pump lubricating oil to the upper and lower surfaces of the crank pin bearing part of the connecting rod through the oil hole in the crankshaft. As a result, a sufficient amount of lubricating oil is always ensured in the crank pin bearing portion, and a desired oil film on the upper and lower surfaces, which is subject to severe loads, can be maintained.

Therefore, even at high engine speeds,
The lubrication of the crank pin bearing is maintained well, and damage caused by insufficient lubrication of the bearing can be reliably prevented.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a hydraulic passage of a variable compression ratio mechanism according to an embodiment of the present invention, Fig. 2 is a cross-sectional view showing an example of a conventional variable compression ratio mechanism, and Fig. 3 is a line taken along the - line in Fig. 2. FIG. 14...Connecting rod, 15...Crankshaft, 16...Eccentric bearing, 20...
...Hydraulic passage for lock pin locking, 21...Hydraulic passage for lock pin unlocking, 24...Oil hole, 26
...Crank pin bearing part, 26a... Upper surface of crank pin bearing part, 26b... Lower surface of crank pin bearing part, 27... Bearing part of crank journal,
32, 33... Lubricating oil groove, 42... Hydraulic switching valve.

Claims (1)

[Claims for Utility Model Registration] (1) Hydraulic passages for low compression ratio control and hydraulic passages for high compression ratio control, which are formed independently of each other in the cylinder block, are formed on the circumference of the bearing part of the crank journal. A lock pin that is separately connected to two independent oil grooves and that is formed in the connecting rod through an oil hole in the crankshaft and can engage the two oil grooves on the circumference of the bearing part with the eccentric bearing. In the hydraulic passage of the variable compression ratio mechanism connected to the two lock pin drive oil passages for hydraulically driving the An oil groove connected to the lock pin driving oil passage is arranged on the circumference of the bearing portion of the crank journal and on the upper and lower surfaces of the crank pin bearing portion of the connecting rod through the oil hole in the crankshaft. A hydraulic passage of a variable compression ratio mechanism characterized by having a lubricating oil groove for pumping lubricating oil. (2) The hydraulic passage of the variable compression ratio mechanism according to claim 1, wherein the lubricating oil groove is connected to the upstream side of a hydraulic switching valve that switches the compression ratio.