JPH048270Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a variable compression ratio mechanism for a multi-cylinder engine, and particularly relates to a hydraulic passage of a variable mechanism that changes the compression ratio using hydraulic pressure.

[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 compression ratio variable mechanism that allows for variable settings (for example, Japanese Patent Application Laid-Open No. 58-91340
(Japanese Patent Application Laid-Open No. 172431/1983).

In a variable compression ratio mechanism using an eccentric bearing, a lock pin engagement hole is provided in the eccentric bearing,
A lock pin storage hole is provided in the connecting rod, and the lock pin is stored in the lock pin storage hole.
By applying hydraulic pressure to the lock pin, the lock pin is driven to advance and retreat in the direction of the engagement hole, thereby engaging and disengaging the lock pin with the lock pin engagement hole.

A hydraulic passage for locking the lock pin and a hydraulic passage for unlocking the lock pin are connected to the lock pin storage hole, and when the load is light, oil is forced into the hydraulic passage for locking the lock pin, locking the eccentric bearing and creating a high compression ratio state. It is becoming more and more common. Also, under medium or high load conditions, oil is forced into the lock pin unlocking hydraulic passage to release the lock on the eccentric bearing, causing the eccentric bearing to rotate and create a low compression ratio state.

As shown in FIG. 9, the lock pin locking hydraulic passage 1 and the lock pin unlocking hydraulic passage 2 are as follows:
It is connected to two independent oil grooves 5 and 6 formed on the circumference of the crank pin bearing 4 of the connecting rod 3. These two oil grooves 5, 6 are connected via oil holes 7 in the crankshaft to two independent oil grooves 9, 10 formed on the circumference of the bearing 8 of the crank journal. One side of the oil hole 7 opens on the outer peripheral surface of the crank pin, and the other side opens on the outer peripheral surface of the crank journal. Oil hole 7
The openings on each side are chamfered, and the diameter of the opening on the crank pin side is _B1 , and the diameter of the opening on the crank journal side is _B2 . The two oil grooves 9 and 10 on the crank journal side are connected to a low compression ratio control hydraulic passage 12 and a high compression ratio control hydraulic passage 13 formed in the cylinder block 11, respectively.

The switching of the hydraulic pressure between the hydraulic passage 13 for high compression ratio control and the hydraulic passage 12 for low compression ratio control is performed by a switching valve (not shown), and from each hydraulic passage 12, 13, a passage is provided for each cylinder. is branched and pressure oil is sent to the lock pin side.

In such a variable compression ratio mechanism, the hydraulic actuation timing of the lock pin is the timing at which the connecting portion of the hydraulic passage is communicated, and the timing at which the hydraulic passage is connected is determined by the rotation angle of the crankshaft. That is, the timing of hydraulic operation of the lock pin is determined by the timing of connection between the oil hole of the crankshaft and the oil groove facing the oil hole.

[Problem that the invention attempts to solve]

However, in a multi-cylinder engine with a variable compression ratio mechanism in which a single switching valve drives the lock pins of all cylinders, there is a problem in that the lock pin operating oil pressure decreases particularly in cylinders located far from the oil pressure source. This is due to pressure loss due to the length of the hydraulic passage and oil leakage from each cylinder. Therefore, the operation of the lock pin in a specific cylinder is much delayed compared to other cylinders, and there is a risk that the engine as a whole will be subject to unbalanced compression ratio switching control.

In order to solve the above problem, this invention minimizes the variation in lock pin operation caused by unbalanced hydraulic pressure by changing the timing of hydraulic operation of the lock pin, thereby making the switching of the compression ratio quick and smooth. The purpose is to

[Means for solving problems]

The hydraulic passage of the variable compression ratio mechanism in the multi-cylinder engine of the present invention, which meets this purpose, connects the hydraulic passage for low compression ratio control and the hydraulic passage for high compression ratio control, which are formed independently in the cylinder block, to the hydraulic passage in the crank journal. The eccentric bearing is connected separately to two independent oil grooves formed on the circumference of the bearing, and the two oil grooves on the circumference of the bearing are connected to the connecting rod through an oil hole in the crankshaft. A hydraulic passage of a variable compression ratio mechanism in a multi-cylinder engine, which is connected to two oil passages for hydraulically driving a lock pin that can be engaged with the hydraulic pressure of a cylinder in which the lock pin is activated later than other cylinders. A correcting means for correcting the delay in actuation of the lock pin is formed at the connecting portion of the passage.

[Effect]

In the hydraulic passage of the variable compression ratio mechanism in a multi-cylinder engine configured as described above, a correction means for correcting the delay in lock pin operation is formed at the connection part of the hydraulic passage of the cylinder whose lock pin operation is delayed compared to other cylinders. Therefore, this correction means corrects the delayed timing of connection between the oil hole and the oil groove of the cylinder, and changes the timing of oil flow. That is, the correcting means advances the delayed lock pin hydraulic operation timing of the cylinders, thereby eliminating variations in the lock pin switching operations caused by oil pressure imbalance or the like.

〔Example〕

Hereinafter, preferred embodiments of the hydraulic passage of the variable compression ratio mechanism in the multi-cylinder engine of the present invention will be described with reference to the drawings. In each of the embodiments to be described later, the description will be given by comparing cylinder A, which has a correction means, and cylinder B, which does not have a correction means, among the multiple cylinders. Since the configuration is similar to that of the hydraulic passage shown in FIG. 9, the explanation will be omitted.

First Embodiment FIGS. 1 to 4 show a hydraulic passage of a variable compression ratio mechanism in a multi-cylinder engine according to a first embodiment of the present invention.

In FIGS. 3 and 4, a piston 21 is slidably inserted into a cylinder 22, and the reciprocating movement of the piston 21 is transmitted to the crankshaft 2 via a piston pin 23 and a connecting rod 24.
5 rotational motion.

Connecting rod 24 and piston pin 23
An eccentric bearing 26 whose inner and outer circumferences are mutually eccentric is interposed between the eccentric bearing 2 and
The compression ratio is changed according to the amount of rotation of 6. A lock pin engagement hole 27 extending in the radial direction is bored in the eccentric bearing 26, and a lock pin 28 is provided on the connecting rod 24 side. The lock pin 28 is slidably housed in a lock pin housing hole 29, and is moved by the differential pressure between two hydraulic passages 30 and 31 formed in the connecting rod 24 for driving the lock pin. One hydraulic passage 30 is a hydraulic passage for a lock pin lock that drives the lock pin 28 toward the eccentric bearing 26, and the other passage 31
is a hydraulic passage for unlocking the lock pin that drives the lock pin 28 in a direction away from the eccentric bearing 26.

As shown in FIG. 1, the lock pin locking hydraulic passage 30 and the lock pin unlocking hydraulic passage 31 communicate with mutually independent oil grooves 32 and 33 formed in the large end of the connecting rod, respectively. The oil grooves 32 and 33 communicate with mutually independent oil grooves 38 and 39 formed on the circumference of the bearing 36 of the crank journal 35 via an oil hole 34 formed in the crankshaft 25.

The oil hole 34 communicates the oil groove 32 and the oil groove 38 in the half rotation range of the crankshaft 25, and communicates the oil groove 33 and the oil groove 39 in the other half rotation range of the crankshaft 25. It's getting old.

The oil groove 38 is connected to a high compression ratio control hydraulic passage 41 formed in the cylinder block 40, and the oil groove 39 is connected to a low compression ratio control hydraulic passage 42 similarly formed in the cylinder block 40. ing. The hydraulic passage 41 for high compression ratio control and the hydraulic passage 42 for low compression ratio control include an oil pan (not shown).
Oil is pumped up from the engine by an oil pump (not shown) and set at a predetermined pressure, and then pumped through a switching valve (not shown).

One side of the oil hole 34 is open to the outer peripheral surface of the crank pin 43, and the other side is opened to the crank journal 35.
It is open on the outer circumferential surface of. The opening of the oil hole 34 on the side of the crank pin 43 has a chamfer 4 as a correction means.
4, and the diameter of the chamfer 44 is _A1 . The opening of the oil hole 34 on the side of the crank journal 35 is similarly chamfered 45 as a correction means, and its diameter is _A2 . Diameter of chamfers 44 and 45 of this oil hole 34
A ₁ and A ₂ are formed larger than the chamfered diameters B ₁ and B ₂ of the oil hole 7 of the B cylinder shown in FIG.

In this embodiment, the circumferential length of each oil groove is the same as that of the B cylinder.

In the first embodiment configured in this way,
When the engine is in a light load state, an actuation signal is output from an electronic control device (not shown) to a switching valve (not shown), and the switching valve is switched to one side. As a result, the pressure oil is sent under pressure to the oil groove 38 via the switching valve and the high compression ratio control hydraulic passage 41, and further the pressure oil is sent from the oil groove 38 to the oil hole 3 of the crankshaft.
4. The oil is intermittently sent to the lock pin lock hydraulic passage 30 via the oil groove 32.

In this case, the diameter of the chamfer of the oil hole 34 of cylinder A
A ₁ and A ₂ are the diameter B ₁ of the chamfer of the oil hole 7 of the B cylinder,
Since it is formed larger than B ₂ , the connection timing between the oil hole 34 and the oil grooves 32 and 38 is brought forward, and the A
The cylinder's hydraulic activation timing is advanced. That is, in this embodiment, as shown in FIG. 2, the hydraulic actuation timing Hi ₁ for switching to the high compression ratio of the A cylinder is greater than the oil pressure actuation timing Hi ₂ of the B cylinder, and the operation of the lock pin 28 is accordingly reduced. As a result, variations in the switching operation of the lock pin 28 are suppressed to a small level as a whole. Similarly, the hydraulic operation timing Lo ₁ for switching to a low compression ratio is also B.
This is larger than the cylinder hydraulic operation timing Lo ₂ , and variations in the switching operation of the lock pin 28 can be suppressed to a small level. In this way, in this embodiment, by chamfering the oil hole 34, it is possible to easily increase or decrease the hydraulic operation timing.

The size of the chamfer of the opening of the oil hole 34 is set to an appropriate size for each cylinder, taking into consideration the degree of delay in the operation of the lock pin 28 of each cylinder.

Second Embodiment FIG. 5 shows a hydraulic passage of a variable compression ratio mechanism in a multi-cylinder engine according to a second embodiment of the present invention. The second embodiment differs from the first embodiment in the size of the chamfer at the opening of the oil hole and the angle at which the oil hole is formed. That is, the chamfered size of the opening of the oil hole 34 in this embodiment is formed to be the same size as the oil hole 7 of the B cylinder shown in FIG. Further, the drilling angle of the oil hole 34 is set so that it advances clockwise by an angle C from the position of the oil hole 7 in FIG. This angle C serves as a correction means for changing the connection timing of the hydraulic passage and correcting the delay in the operation of the lock pin 28.

In the second embodiment configured in this way, as shown in FIG. 6, the hydraulic actuation timing Hi 3 for switching to a high compression ratio and the hydraulic actuation timing Lo ₃ for switching to a low compression _ratio .
However, the hydraulic operation timing of the B cylinder is generally advanced compared to Hi ₂ and Lo ₂ . Therefore, the hydraulic pressure acts on the lock pin 28 of the A cylinder earlier than that of the B cylinder.
The delay in the operation of the lock pin 28 in the A cylinder is eliminated.

Furthermore, the method of changing the drilling angle of the oil hole 34 as in this embodiment allows for a wide range of changes in the hydraulic action timing, and also eliminates the need to change the oil groove in the crankshaft bearing.

Third Embodiment FIG. 7 shows a hydraulic passage of a variable compression ratio mechanism in a multi-cylinder engine according to a third embodiment of the present invention. The third embodiment differs from the first embodiment in the size of the oil hole chamfer and the length of the oil groove. That is, the size of the chamfer of the oil hole 34 of this embodiment is the same as that of the second embodiment, and the size of the chamfer of the oil hole 7 of the B cylinder shown in FIG.
The cylinder has the same size as the cylinder B, and differs from cylinder B only in the circumferential length of the oil grooves 32 and 38 communicating with the high compression ratio control hydraulic passage 41. Oil groove 3
2 and 38 are formed to extend by a distance D in a direction opposite to the rotational direction of the crankshaft 25, and this extended distance D serves as a correction means.

In the third embodiment configured in this way,
As shown in FIG. 8, the hydraulic operating timing Hi ₄ at the time of switching to a high compression ratio is greater than the hydraulic operating timing Hi ₂ of the B cylinder. That is, as the oil grooves 32 and 38 are extended, the hydraulic operating angle increases, and when switching to a high compression ratio, the hydraulic pressure acts on the lock pin 28 earlier than on the B cylinder, and the lock pin 28 in the A cylinder
8 is eliminated.

Furthermore, when switching to a low compression ratio, the hydraulic pressure operating timing Lo ₄ of the A cylinder is the same as the hydraulic operating timing Lo ₂ of the B cylinder, but this is to release the lock of the eccentric bearing 26, so the hydraulic pressure is slightly lowered. Lock pin 2 even if it is low
8 is surely removed from the lock pin engagement hole 27,
In particular, there is no need to correct the timing of hydraulic action when switching to a low compression ratio. Therefore, by changing the length of the oil groove as described above, it is possible to independently vary each hydraulic pressure application timing.

In this way, by appropriately varying the length of the oil groove in the square cylinder, the drilling angle of the oil hole 34 in the crankshaft, and the size of the chamfer of the oil hole 34, the hydraulic pressure for driving the lock pin of each cylinder can be adjusted. It becomes possible to minimize variations in the operation of the lock pin due to balance, and the switching of the compression ratio is performed smoothly.

In each of the above-described embodiments, a single correction means is provided, but two or more correction means may be combined.

[Effect of idea]

As explained above, when using the hydraulic passage of the variable compression ratio mechanism in the multi-cylinder engine of the present invention, the lock pin activation delay is corrected at the connection part of the hydraulic passage of the cylinder where the lock pin activation is delayed compared to other cylinders. Since the correcting means is formed, the timing of the hydraulic pressure action of the lock pin in the delayed cylinder is brought forward, and variations in the operation of the lock pin can be minimized for the engine as a whole. Therefore, it is possible to quickly and smoothly switch the compression ratio.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the hydraulic passage of the variable compression ratio mechanism in the vicinity of the crankshaft in a multi-cylinder engine according to the first embodiment of the present invention, and FIG. 3 is an overall view of the variable compression ratio mechanism shown in FIG. 1, FIG. 4 is a sectional view taken along the - line in FIG. 3, and FIG. Fig. 5 is a sectional view of the hydraulic passage of the variable compression ratio mechanism in the vicinity of the crankshaft in a multi-cylinder engine according to the second embodiment of the present invention, and Fig. 6 shows the formation of the hydraulic pressure operation timing and correction means in the hydraulic passage of Fig. 5. FIG. 7 is a cross-sectional view near the crankshaft of a hydraulic passage of a variable compression ratio mechanism in a multi-cylinder engine according to a third embodiment of the present invention. Fig. 8 is a relational diagram showing the relationship between the hydraulic action timing in the hydraulic passage in Fig. 7 and the hydraulic action timing of other cylinders in which no correction means are formed, and Fig. 9 is a cross section of the conventional hydraulic passage and in which no correction means is formed. Figure. 24...Connecting rod, 25...Crankshaft, 26...Eccentric bearing, 27...
... Lock pin engagement hole, 28 ... Lock pin, 29
...Lock pin storage hole, 30...Hydraulic passage for lock pin locking, 31...Hydraulic passage for lock pin unlocking, 32, 33...Oil groove on connecting rod side, 34...Oil hole, 38, 39...Crank Oil groove on journal bearing side, 41...Hydraulic passage for high compression ratio control, 42...Hydraulic passage for low compression ratio control, 44, 45...Chamfering of oil hole as correction means, C...As correction means Drilling angle of oil hole, D
...The extension distance of the oil groove as a correction means.

Claims (1)

[Scope of utility model registration request] A low compression ratio control hydraulic passage and a high compression ratio control hydraulic passage formed independently in the cylinder block are separately connected to two independent oil grooves formed on the circumference of the bearing of the crank journal, The two oil grooves on the circumference of the bearing were connected to two oil passages formed in the connecting rod through oil holes in the crankshaft for hydraulically driving a lock pin that was engageable with the eccentric bearing. In a hydraulic passage of a variable compression ratio mechanism in a multi-cylinder engine, a correction means for correcting the delay in the activation of the lock pin is formed at a connecting portion of the hydraulic passage of a cylinder in which the activation of the lock pin is delayed relative to other cylinders. Hydraulic passage of a variable compression ratio mechanism in a multi-cylinder engine.