JPH0826790B2 - Hydraulic control method for variable compression ratio mechanism - Google Patents

Description

The present invention relates to a hydraulic control method for a lock pin in a variable compression ratio mechanism of an internal combustion engine using an eccentric bearing.

[Conventional technology]

An eccentric bearing is interposed between the connecting rod and the piston pin, and the relative position of the piston with respect to the connecting rod is changed by the rotation of the eccentric bearing,
A variable compression ratio mechanism that makes the compression ratio variable has been previously proposed (for example, JP-A-58-172431).

5 to 6 show an example of a conventional variable compression ratio mechanism. In the figure, reference numeral 1 denotes a piston, which is slidably fitted in a cylinder, and the reciprocating motion of the piston 1 is transmitted to a crankshaft 4 via a connecting rod 3. Between the piston pin 2 and the connecting rod 3, an eccentric bearing 5 made of a cylindrical body whose inner and outer circumferences are eccentric to each other is interposed, and the relative position of the piston with respect to the connecting rod 3 is determined by the rotation amount of the eccentric bearing 5. Instead, the compression ratio is made variable.

The eccentric bearing 5 is provided with a lock pin engaging hole 6 formed of a hole extending in the radial direction, the connecting rod 3 is provided with a lock pin receiving hole 7, and the lock pin receiving hole 7 is provided with the lock pin 8. Is slidably inserted.
The lock pin 8 moves in and out of the lock pin engaging hole 6 to lock or free the rotation of the eccentric bearing 5.

A lock pin lock hydraulic passage 9 is connected to the lock pin housing hole 7 at a position where the lock pin 8 can be driven in the direction of the eccentric bearing 5, and the lock pin unlocks at a position to drive the lock pin 8 in a direction away from the eccentric bearing 5. The hydraulic passage 10 for use is connected. The lock pin lock hydraulic passage 9 and the lock pin unlock hydraulic passage 10 are designed so that the hydraulic pressure is switched by a switching valve (not shown), and the switching valve passes through an oil pump (not shown). Pressure oil is sent. The pressure oil from the oil pump is switched in a predetermined direction by a switching valve, and oil grooves 15, 16 formed in the crank journal bearing, an oil passage 18 in the crankshaft 4, an oil groove in the large end bearing of the connecting rod 3 are formed. It is sent to the lock pin lock hydraulic passage 9 and the lock pin unlock hydraulic passage 10 via 17 and 19.

When the load is high, pressure oil is sent to the lock pin unlocking hydraulic passage 10 to disengage the lock pin 8 from the lock pin engaging hole 6, and the eccentric bearing 5 is unlocked and becomes free. At this time, the piston receives the compressed gas pressure and the explosive force in the vicinity of the compression top dead center and automatically rotates the eccentric bearing 5 to keep the relative position with respect to the connecting rod 3 at a low position, and a low compression ratio is obtained.

Further, when the load is light or medium, pressure oil is sent to the lock pin lock hydraulic passage 9, the eccentric bearing 5 rotates, and the lock pin engagement hole 6 comes to a position corresponding to the lock pin 8, the lock is performed. The pin 8 enters the lock pin engagement hole 6 and locks the rotation of the eccentric bearing 5. At this time, the piston 1 is locked at a high position relative to the connecting rod 3, so that the compression ratio is high.

In order for the eccentric bearing to be locked and unlocked smoothly, the lock pin must be hydraulically driven smoothly. When the engine speed increases, the hydraulic pressure does not increase sufficiently with the conventional technology.In the conventional technology, the inertial force acting on the lock pin may be as large as the hydraulic pressure in the high engine speed range, and the lock pin control is sufficient. However, the switching of the compression ratio may become uncertain.
Further, when the engine oil temperature is low, the oil viscosity is high, the operation of the lock pin becomes slow, and switching of the compression ratio may be uncertain.

Therefore, in order to ensure the operation of the lock pin,
Various hydraulic control devices have been proposed in which the hydraulic pressure is temporarily increased at a compression ratio (for example, Japanese Utility Model Application No. 60-95149).
issue).

[Problems to be solved by the invention]

However, in the conventional hydraulic control device, although the means for increasing the hydraulic pressure is disclosed, there is still no disclosure as to how long the high hydraulic pressure should be maintained. That is, holding the high hydraulic pressure for a long time unnecessarily increases the work of the oil pump and promotes oil leakage. Therefore, it is necessary to set the holding time of the high hydraulic pressure when switching the compression ratio to an appropriate value.

It is an object of the present invention to provide a hydraulic control method which pays attention to the above points, operates the lock pin reliably in all operating ranges, and has less work loss.

[Means for solving problems]

According to the hydraulic control method of the variable compression ratio mechanism of the present invention which meets this object, an eccentric bearing is rotatably interposed between a piston pin and a connecting rod, and the compression ratio is changed in accordance with the rotation of the eccentric bearing, and the eccentric A bearing is provided with a lock pin engagement hole, and a lock pin is provided on the connecting rod side to move in and out of the lock pin engagement hole, and the lock pin is driven to hydraulically engage or unlock the lock pin engagement hole. A hydraulic pressure control method for a variable compression ratio mechanism in which the hydraulic pressure is controlled to be temporarily increased at the time of switching the compression ratio, wherein a holding time of high hydraulic pressure generated at the time of switching the compression ratio is changed based on operating conditions of the engine. It consists of the set.

[Action]

In such a hydraulic control method of the variable compression ratio mechanism, the holding time of the high hydraulic pressure with respect to the operating conditions of the engine (for example, the engine speed etc.) is predetermined. This holding time is set to a time that allows the lock pin to reliably engage or unlock the eccentric bearing, and is not set longer than necessary.

Therefore, in any operation range, the lock pin operates reliably to smoothly switch the compression ratio, and moreover, the loss of work is suppressed to a small extent by the reduction of the high load time of the oil pump.

〔Example〕

A preferred embodiment of a hydraulic control method for a variable compression ratio mechanism according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows an example of a lock pin hydraulic control device to which the hydraulic control method of the present invention is applied. The conventional structure shown in FIGS. 5 and 6 is applied correspondingly to the embodiment of the present invention.

In FIG. 3, the oil 21 in the oil pan 20 is sent to the switching valve 24 via the oil filter 22 and the oil pump 23. Two passages 25 and 26 from the switching valve 24 are connected to a lock pin lock hydraulic passage and a lock pin unlock hydraulic passage, respectively.

Between the oil pump 23 and the switching valve 24, a relief valve 27 for setting the pressure of the lock pin drive passages 25, 26 is provided. A passage 28 for guiding oil to the valve train is branched from a passage from the oil pump 23 to the switching valve 24, and an electromagnetic valve 29 for opening and closing the passage 28 is provided in the branch passage 28. By closing the solenoid valve 29, the pressure in the lock pin driving passage is raised for a certain period of time, and by opening it, the pressure in the passage is restored.

In response to a command from the ECU 30 (electronic control unit), the switching valve 24 sends pressure oil to the passage 26 connected to the lock pin unlock hydraulic passage when the load is high, and to the passage 25 connected to the lock pin lock hydraulic passage when the load is light or medium. Switched to send pressure oil.

In the lock pin hydraulic control device having the above configuration, the ECU 3
When a switching signal from 0 to a high compression ratio is output, the switching valve 24 operates, and the flow of oil is switched from the passage 26 leading to the lock pin unlocking hydraulic passage to the passage 25 leading to the lock pin locking hydraulic passage. At the same time as 26 is drained, the solenoid valve 29 operates for a certain period of time to increase the hydraulic pressure. The oil pressure is returned to the normal oil pressure by the oil pump 23.

Next, when a switching signal to the low compression ratio is issued, the switching valve 24 is activated, and the oil flow moves from the passage 25 leading to the lock pin locking hydraulic passage to the passage 26 leading to the lock pin unlocking hydraulic passage, and the passage 25 Is connected to the drain, and at the same time, the solenoid valve 29 operates in the same way as described above to increase the hydraulic pressure,
After that, the hydraulic pressure drops to normal.

As described above, when the switching signal is output, the solenoid valve 29 always operates at the same time for a certain period of time, that is, based on the high hydraulic pressure holding time map shown in FIG. 2, to ensure the operation of the lock pin under any operating condition. The hydraulic pressure is increased so that the switching of the compression ratio is surely completed.

The ECU 30 is connected with an engine speed sensor 31 that detects the engine speed and an air flow meter 32 that measures the intake air amount.

FIG. 1 shows a block diagram of a hydraulic control method for a compression ratio variable mechanism according to an embodiment of the present invention.

As shown in Fig. 1, first, the CPU in the ECU 30
Is interrupted, the engine speed NE and the intake air amount Q as engine operating conditions are input in step 41, and the compression ratio is determined in step 42. That is, in step 42, the engine speed NE, the intake air amount Q, and the engine speed NE
The compression ratio corresponding to the operating state is read from the map created in relation to the ratio Q / NE. The compression ratio map is
As shown in the figure, the horizontal axis shows the engine speed NE, and the vertical axis shows the ratio Q / NE of the intake air amount Q and the engine speed NE. The high compression ratio region A and the low compression ratio region are shown in the graph. It has a boundary value C that separates B and B. Then, the engine speed sensor 31 and the air flow meter provided in the engine
When the signal from 32 is input, the output of whether to take a high compression ratio or a low compression ratio depending on whether the intersection of the corresponding map is in the high compression ratio region or the low compression ratio region It is designed to output.

When the high compression ratio is selected in step 42, the process proceeds to step 43, it is judged whether the previously determined compression ratio is the high compression ratio or the low compression ratio, and if the result is the low compression ratio, step 44 Next, the high hydraulic pressure holding time for switching the high compression ratio is set from the map for engine operating conditions such as engine speed NE or water temperature. In this embodiment, as shown in FIG. 2, the optimum holding time T ₁ is set for the engine speed NE, and in this map, the holding time T ₁ decreases as the engine speed NE increases. It is supposed to do. When the holding time T ₁ is set, the process proceeds to step 45, the timer is reset and the timer is started, and the hydraulic pressure is held for the holding time in step 46.
It is temporarily increased by T ₁ . That is, an operation signal is output from the ECU 30 to the solenoid valve 29 at the same time when the timer starts,
The passage 28 is closed by the solenoid valve 29 for the holding time T ₁ , and the hydraulic pressure in the lock pin actuating hydraulic passage 25 is temporarily increased.
This reveals a high compression ratio condition in which the lock pin is positively engaged with the eccentric bearing. Then, when the high compression ratio state is reached, the ignition timing is adjusted to one adapted to the high compression ratio in step 47, and then in step 48 the compression ratio flag is set to FC = 1 and the high compression ratio high hydraulic control flag is set to FH = 1. Then, the process returns to step 49.

If the compression ratio previously determined in step 43 is a high compression ratio, the process proceeds to step 50 and the high hydraulic control flag for high compression ratio is FH =
If it is 0, the process directly returns to step 49. Process 50 is FH
If = 1, the process proceeds to step 51 and it is determined whether the timer has timed out. As a result, if the time is not up, the process returns to step 49, and if the time is up,
Proceed to step 52 to reduce the hydraulic pressure to normal pressure,
= 0 and the process returns to step 49.

When the low compression ratio is selected in step 42, the process proceeds to step 54, it is determined whether the previously determined compression ratio was a high compression ratio or a low compression ratio, and if the result is high compression, Proceeding to step 55, the high hydraulic pressure holding time T ₂ for switching the low compression ratio is set from the engine speed NE. Retention time T ₂
Is set shorter than the holding time T ₁ as shown in FIG. When the holding time T ₂ is set, the process proceeds to step 56, the timer is reset and the timer is started, and the hydraulic pressure is temporarily increased by the holding time T _{2 in} step 57. That is, as described above, the passage 28 is closed by the solenoid valve 29, and the hydraulic pressure in the lock pin actuating hydraulic passage is temporarily increased. This ensures that the lock pin is disengaged from the eccentric bearing and a low compression ratio condition is revealed. Step 58 when low compression ratio
Then, the ignition timing is also adjusted to one suitable for the low compression ratio, and thereafter, in step 59, the compression ratio flag is set to FC = 0, and the low compression ratio high hydraulic control flag is set to FL = 1, and the process returns to step 49.

If the compression ratio previously determined in step 54 is a low compression ratio, the process proceeds to step 60 and the high oil pressure control flag for low compression ratio FL =
If it is 0, the process directly returns to step 49. FL in step 60
If = 1, the process proceeds to step 61 and it is determined whether the timer has timed out. As a result, if the time is not up, the process returns to step 49. If the time is up, the process proceeds to step 62, the hydraulic pressure is reduced to the normal pressure, and the process 63
Then, FL = 0 is set and the process returns to step 49.

In this way, when the compression ratio is switched, the hydraulic pressure in the lock pin driving hydraulic passages 25 and 26 is temporarily increased, so that the lock pin operates smoothly and the compression ratio is switched quickly and reliably. The high pressure oil holding time T ₂
Is set shorter than the holding time T ₁ because unlocking is easier than locking the eccentric bearing.

〔The invention's effect〕

As described above, according to the hydraulic control method of the variable compression ratio mechanism of the present invention, the holding time of the high hydraulic pressure generated at the time of switching the compression ratio is changed based on the operating condition of the engine, so any operation Even under the conditions, the lock pin can be surely engaged or unlocked with the eccentric bearing, and the optimum holding time with less loss can be obtained. As a result, the work of the oil pump and the oil leakage can be suppressed to a small level, and the compression ratio can be reliably switched.

[Brief description of drawings]

FIG. 1 is a block diagram showing a flow of hydraulic control of a variable compression ratio mechanism according to an embodiment of the present invention, FIG. 2 is a high hydraulic control map, and FIG. 3 is a lock pin hydraulic control to which the present invention is applied. A schematic diagram of the apparatus, FIG. 4 is a compression ratio map diagram, FIG. 5 is a sectional view of a conventional variable compression ratio mechanism using an eccentric bearing, and FIG. 6 is a sectional view taken along line VI-VI of FIG. Is. 23 …… oil pump 25,26 …… hydraulic passage for lock pin drive 29 …… solenoid valve 30 …… ECU (electronic control unit) 31 …… engine speed sensor 32 …… air flow meter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-91340 (JP, A) JP-A-60-142020 (JP, A) Actual opening 62-3952 (JP, U) Actual opening 62- 114149 (JP, U) Actual Kohei Hei 4-30354 (JP, Y2)

Claims (1)

[Claims] 1. An eccentric bearing is rotatably interposed between a piston pin and a connecting rod to make a compression ratio variable according to the rotation of the eccentric bearing, and to provide a lock pin engaging hole in the eccentric bearing and to connect the eccentric bearing. A lock pin that moves in and out of the lock pin engagement hole is provided on the rod side, and the lock pin is driven so as to be engaged or unlocked in the lock pin engagement hole by hydraulic pressure, and the hydraulic pressure is temporarily increased when the compression ratio is switched. In the hydraulic control method of the variable compression ratio mechanism controlled as described above, the holding time of the high hydraulic pressure generated when the compression ratio is switched is variably set based on the operating condition of the engine. Method.