JPH0415964Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention aims to reduce the compression ratio switching shock for each cylinder in a multi-cylinder internal combustion engine that has a mechanism for changing the compression ratio in stages. The present invention relates to a control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism, in which the switching engine operating range is slightly changed so that switching is performed sequentially instead of all cylinders at once.

[Prior Art] In an automatic cycle internal combustion engine, increasing the compression ratio improves combustion efficiency, improves fuel efficiency, and improves shaft torque, so it is desirable to increase the compression ratio. However, when the compression ratio is increased, the gas is adiabatically compressed in the combustion chamber, and when the temperature rises, it becomes easier to ignite and cause knocking, which limits the increase in the compression ratio. Knocking tends to occur at high loads when a large amount of air is sucked into the combustion chamber, and is less likely to occur at light loads when the amount of air sucked in is small and the actual degree of compression in the combustion chamber is small. Therefore, the compression ratio should be adjusted according to the load. It is desirable that the compression ratio be made variable so that the compression ratio, which is set to be appropriate for medium to high loads, is increased during light loads. In this sense, many variable compression ratio mechanisms for internal combustion engines have been proposed.

Proposals related to variable compression ratio mechanisms are divided into mechanisms that calculate the optimal compression ratio according to engine operating conditions and mechanisms that change the compression ratio according to these calculated compression ratios. , Japanese Patent Publication No. 1983-
There are proposals such as Japanese Unexamined Utility Model Publication No. 188056 and Japanese Utility Model Application No. 59-196532, and the latter includes proposals such as Japanese Unexamined Utility Model Publication No. 59-40537. The present invention belongs to the former category.

The conventional mechanism for determining the optimal compression ratio was based on feedback control, which introduced the load and rotation speed into the control circuit, determined the optimal compression ratio based on the same map, and controlled the compression ratio using this output. .

[Problems to be solved by the invention] However, in the conventional variable compression ratio mechanism, when switching the compression ratio in an engine with a two-stage or multi-stage variable compression ratio mechanism, the compression ratio is switched simultaneously for all cylinders. Therefore, there was a risk that discontinuous changes in torque etc. would occur, resulting in an uncomfortable shock for the occupants.

The object of the present invention is to reduce the shock when switching the compression ratio in a multi-cylinder engine and to lower it to a level that is perceptible to the occupants, thereby enabling comfortable driving.

[Means for Solving the Problems] A control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism according to the present invention to achieve this object includes the following device. In other words, each cylinder has a compression ratio map that defines a low compression ratio region and a high compression ratio region for engine operating conditions including engine speed and engine load, and the map has a compression ratio map that defines a low compression ratio region and a high compression ratio region for engine operating conditions including engine speed and engine load. In a control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism, the CPU determines the compression ratio of each cylinder from moment to moment based on the compression ratio map according to engine operating conditions. A control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism, characterized in that a compression ratio switching line between a low compression ratio region and a high compression ratio region of a compression ratio map is made different between cylinders.

[Function] In the control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism configured as described above, signals of engine operating conditions such as intake pipe negative pressure and engine speed read by each sensor are sent to the CPU. Then, a compression ratio is determined for each cylinder from a compression ratio map provided for each cylinder, and each cylinder is controlled to the determined compression ratio. In this case, the engine operating range for switching the compression ratio is changed little by little for each cylinder, and switching is not performed for all cylinders at the same time, so a large switching shock does not occur.

[Embodiments] Hereinafter, preferred embodiments of a control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism according to the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention. In the figure, signals from sensors that detect engine operating conditions, such as intake pipe negative pressure sensor 1 that detects engine load, engine rotation speed sensor 2, etc., are sent to CPU 3. The optimum compression ratio and optimum ignition timing for each cylinder are calculated from the ratio map 4 and the ignition map 5.

As shown in FIG. 2, the compression ratio map 4 shows whether the engine should be in the high compression ratio region 12 or in the low compression ratio region 13 under the input conditions with respect to the engine speed and intake pipe negative pressure. is determined independently for each cylinder and not the same for all cylinders. That is, the compression ratio switching line, which is the boundary between the high compression ratio region and the low compression ratio region, is different between cylinders. In the illustrated example, the compression ratio switching lines for the #1 and #4 cylinders are different from the compression ratio switching lines for the #2 and #3 cylinders, for example. However, FIG. 2 shows an example of two-stage switching of high compression ratio and low compression ratio.

As shown in Fig. 3, the ignition map 5 is such that the ignition advance angle 14 is determined in conjunction with the compression ratio determined for the engine speed and intake pipe negative pressure, and is set for each cylinder. The optimum ignition advance angle is now determined.

The optimum compression ratio and optimum ignition timing determined by the CPU 3 are determined by a compression ratio control mechanism 41 (switching valve 41 to be described later) that can control the compression ratio for each cylinder and an ignition timing that can control the ignition timing for each cylinder. The signals are sent to a control mechanism 49 to control each of them.

The CPU 3 relates the operations of each mechanism as shown in the block diagram of FIG. In other words, at a certain moment when the engine is running, CPU3 is activated in step 6.
Then, in step 7, the intake pipe negative pressure and engine speed are read from each sensor 1, 2, in step 8, the compression ratio for each cylinder is determined from the compression ratio map 4, and in step 9. Then, the ignition timing is determined from the ignition map associated with the compression ratio determined for each cylinder, and in step 10, each cylinder is controlled to the determined compression ratio and ignition timing, and in step 11, the process returns. Compression ratio control and ignition timing control are performed by applying the above routine to any period of engine operating conditions.

In the above control, the determination of the compression ratio and the determination of the ignition timing in the compression ratio map 4 and the ignition map 5 are
Since compression ratio switching is performed independently for each cylinder, and the compression ratio switching conditions are slightly different for each cylinder, compression ratio switching is automatically performed differently between cylinders, and all cylinders are compressed at the same time. The ratio cannot be changed.

The output of the CPU 3 is sent to the mechanisms shown in FIGS. 5 to 7 to control the compression ratio.

5 to 7, a piston 16 is slidably fitted into a cylinder 15 of an internal combustion engine, and the piston 16 is connected to a connecting rod 17 via a piston pin 18. The piston pin 18 is supported in a piston pin hole of the piston 16.

An eccentric bearing is formed in which the wall thickness changes in the circumferential direction between the piston pin insertion hole 19 at the small end of the connecting rod 17 and the outer circumference of the piston pin 18, and the inner circumference circle and the outer circumference circle are eccentric from each other. 20 is rotatably interposed.

An eccentric bearing 20 is located on the connecting rod 17 at a position corresponding to the eccentric bearing 20.
A lock pin storage hole 21 extending in the radial direction is formed, and a lock pin 22 is accommodated in the hole 21 so as to be slidable and retractable from the eccentric bearing 20 from the hole 21. On the other hand, in the eccentric bearing 20, a lock pin engagement hole 23 having a diameter that allows the lock pin 22 to move in and out is formed in a thicker portion in the radial direction. When the lock pin 22 engages with the lock pin engagement hole 23, the piston 16
Keep the lock pin 22 at a high position to achieve a high compression ratio.
When the engagement is released, the eccentric bearing 20 rotates freely, and the piston is in a low position at compression top dead center, making it possible to achieve a low compression ratio state.

Next, to describe the drive structure of the lock pin 22, the lock pin locking hydraulic passage 24 and the lock pin unlocking hydraulic passage 25 are connected to the lock pin housing hole 21 with the lock pin 22 in between. It is opened at a position that urges the eccentric bearing in the direction of the eccentric bearing 20. Further, on the outer periphery of the eccentric bearing 20, a lock pin guide groove 2 is provided at a position corresponding to the lock pin 22 and extends all the way in the circumferential direction.
6 is formed, and this groove 26 is provided with the lock pin engaging hole 23.

The hydraulic passages 24 and 25 provided in the connecting rod 17 communicate with oil grooves 28 and 29 provided independently on the circumference of the bearing at the large end of the connecting rod, respectively. . Oil groove 2
8 and 29 are oil passages 3 in the crankshaft 30
1, oil grooves 32, 3 independently provided on the circumference of the journal bearing of the crankshaft.
3 so that they can communicate intermittently when the crankshaft 30 rotates. The oil groove 32 can communicate with the lock pin locking hydraulic passage 24 via the oil groove 28, and the oil groove 33 can communicate with the lock pin unlocking hydraulic passage 25 via the oil groove 29.

Inside the cylinder block, there is a main oil passage 34 for high compression ratio and a main oil passage 35 for low compression ratio.
The high compression ratio main oil passage 34 communicates with the oil groove 32, and the low compression ratio main oil passage 35 communicates with the oil groove 33. The lubricating oil 37 in the oil pan 36 passes through an oil strainer 38 and a return pipe 39 to the oil pump 4.
0 and sent via the switching valve 41 to either the high compression ratio main oil passage 34 or the low compression ratio main oil passage 35. In the battery 4, there is an ignition switch 43, a relay 44 that detects a start signal, an intake negative pressure switch 46 attached to the intake manifold 45 in a gasoline engine, or a pressure sensor attached to the pump chamber 47 of the fuel injection pump in a diesel engine. A switch 48 is incorporated in a circuit as shown,
The switching valve 41 is operated according to the load, and when the load is medium or high, pressure oil is sent to the main oil passage 35 for low compression ratio, and when the load is light, pressure is sent to the main oil passage 34 for high compression ratio. The flow of oil is controlled.

Next, the operation of the embodiment configured as described above will be explained.

First, engine operating conditions such as engine speed and engine load are detected by the respective sensors 1 and 2, and the signals are sent to the CPU 3 (step 7), and the compression ratio is determined based on the compression ratio map 4. Then, the ignition timing is determined based on the ignition map 5 (Step 9). The output value is sent to a compression ratio control mechanism 41 and an ignition timing control mechanism 49 to control the compression ratio and ignition timing.

Specifically, the compression ratio is controlled as follows. First, when a low compression ratio output is being output, pressurized oil is sent to the low compression ratio main oil passage 35 by the switching valve 41, and the pressurized oil flows through the oil groove 33 and the oil in the crankshaft 30. The oil is sent to the lock pin unlocking hydraulic passage 25 via the passage 31 and the oil groove 29, and the lock pin 22 is housed in the lock pin storage hole 21 and removed from the lock pin engagement hole 23, and the eccentric bearing 20 is unlocked. In this state, the eccentric bearing 20 is rotatable, so it receives the inertia force and explosive force from the piston 16 via the piston pin 18 and rotates, so the piston 1
6 continues to move in the free state trajectory A in FIG. Therefore, at the compression top dead center position, piston 1
No. 6 is pushed down, and a low compression ratio can be achieved. For this reason, knocking is less likely to occur regardless of whether the load is medium or high, the compression ratio can be maintained high, and fuel efficiency and shaft torque can be improved.

On the other hand, when a high compression ratio output is being produced, the eccentric bearing 20 is locked at a position where a high compression ratio state can be achieved in the following manner. That is, the high compression ratio main oil passage 3 is controlled by the switching valve 41.
Pressure oil is sent to the lock pin lock hydraulic passage 24 via the oil groove 32, the oil passage 31 in the crankshaft 30, and the oil groove 28,
The lock pin 22 is driven in the direction out of the lock pin storage hole 21 and engaged with the lock pin engagement hole 23 of the rotating eccentric bearing 20, thereby locking the eccentric bearing 20. In the locked state, piston 1
6 is locked at a high position, it is possible to achieve a high compression ratio. At this time, piston 1
6 moves along the locus B of high compression ratio in FIG. Note that locus C is the locus that would be obtained if the piston was locked at a low compression ratio. In this way, the present invention can be applied to engines that are set to obtain high compression ratios under medium and high load conditions, and therefore engines that have substantially low compression ratios under light load conditions. Therefore, a high compression ratio can be obtained at low loads, improving fuel efficiency and increasing shaft torque.

[Effects of the invention] According to the invention, the compression ratio switching line, which is the boundary between the low compression ratio region and the high compression ratio region, in the compression ratio map for each cylinder is made different between the cylinders.
The compression ratios of all cylinders are not changed at the same time, which reduces the switching shock and reduces the discomfort felt to the occupants below the perceptible level.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism according to an embodiment of the present invention, FIG. 2 is a compression ratio map diagram, and FIG. 3 is an ignition map diagram.
Fig. 4 is a block diagram showing the operation, Fig. 5 is a sectional view of the variable compression ratio mechanism to which the present invention is applied, Fig. 6 is a sectional view of the variable compression ratio mechanism in a direction perpendicular to Fig. 5, and Fig. 7. 5 is a system diagram of a hydraulic circuit for switching the compression ratio of the mechanism shown in FIG. 5, and FIG. 8 is a piston locus diagram in each state in which the eccentric bearing is locked in FIG. 5. 1...Intake pipe negative pressure sensor, 2...Engine speed sensor, 3...CPU, 4...Compression ratio map,
41...Compression ratio control mechanism.

Claims (1)

[Scope of utility model registration request] Each cylinder has a compression ratio map that defines a low compression ratio region and a high compression ratio region for engine operating conditions, including engine speed and engine load, and has a compression ratio map that defines a low compression ratio region and a high compression ratio region for each engine operating condition, including engine speed and engine load. In a control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism, the CPU determines the compression ratio of each cylinder from moment to moment based on the compression ratio map according to the operating conditions. A control device for a multi-cylinder internal combustion engine with a variable compression ratio mechanism, characterized in that a compression ratio switching line between a low compression ratio region and a high compression ratio region of a ratio map is made different between cylinders.