JPH0415959Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a compression ratio switching control device for a variable compression ratio engine of an internal combustion engine.

[Prior Art] In an 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 combustion chamber undergoes adiabatic compression, 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 is small and the effective compression ratio in the combustion chamber is small. It is desirable to make the compression ratio variable depending on the load, so that the compression ratio, which has been set to be appropriate for medium and high loads, is increased during light loads. In this sense, many variable compression ratio engines have been proposed in the past.

A conventional variable compression ratio mechanism is disclosed in Japanese Utility Model Application Publication No. 13782/1982, and is constructed as shown in A and B of FIG. 3, for example. In A and B of FIG. 3, 1 is a cylinder block, 2 is a piston, 3 is a connecting rod, and 4 is a piston pin.

The wall thickness changes in the circumferential direction between the small end hole 5 at the small end of the connecting rod 3 and the outer periphery of the piston pin 4, and the inner periphery and the outer periphery are made of a cylindrical body eccentric from each other. An eccentric bearing 6 is rotatably interposed.

A lock pin hole 7 extending in the radial direction of the eccentric bearing 6 is formed at a position corresponding to the eccentric bearing 6 of the connecting rod 3, and the hole 7 includes:
A lock pin 8 is housed so as to be slidable and retractable from the eccentric bearing 6 through the hole 7. On the other hand, the eccentric bearing 6 has a lock hole 9 formed in its thick part in the radial direction with a diameter that allows the lock hole 8 to enter and exit.When the lock pin 8 engages with the lock hole 9, the piston 2 is connected. When the lock pin 8 is disengaged, the eccentric bearing 6 rotates freely, and the piston 2 is in a low position at compression top dead center, resulting in a low compression ratio. It is now possible to express

The lock pin 8 is driven by hydraulic switching between an oil passage 10 for the lock pin, which is opened at a position that urges the lock pin 8 in the direction of the eccentric bearing 6, and an oil passage 11 for unlocking the lock pin, which applies hydraulic pressure in the opposite direction. be exposed. Each oil passage 10,1
Pressure oil is sent to 1 from the crankshaft 12 side.

Conventionally, the compression ratio was determined by detecting engine operating conditions such as engine load and engine speed by respective sensors 16 and 17, and sending the signals to the CPU 18 to control the compression ratio control mechanism, as shown in FIG. Oil passage 10 for lock pin lock is sent to valve 19
This is controlled by switching the supply of hydraulic pressure to the lock pin unlocking oil passage 11.

[Problems to be solved by the invention] Normally, when a vehicle is running in an urban area, the operating conditions of the engine change frequently and the engine load and engine speed increase and decrease rapidly. The number of compression ratio switching increases. Moreover, near the compression ratio switching boundary line,
Because the difference in compression ratio selection between high compression ratio and low compression ratio is small, the compression ratio switching effect does not increase much, but the compression ratio switches every time the compression ratio crosses the switching boundary line. It is being In particular, if the operating conditions are such that the engine load increases or decreases near the compression ratio switching boundary line, the number of compression ratio switching may be unnecessarily increased, even though there is no need to switch the compression ratio. A problem arises in that the durability of the variable ratio mechanism is reduced. For example, a problem arises in that the lock pin, which is subjected to impact by colliding with the wall of the lock hole of the eccentric bearing during switching, is subject to increased damage and wear.

The present invention sets multiple operating regions with different controls near the compression ratio switching boundary line, and according to these operating regions, the compression ratio switching control is made to wait for a certain period of time in the motion region where the compression ratio switching effect is small. Therefore, an object of the present invention is to provide a control device for a variable compression ratio engine that can reduce the number of times the compression ratio is switched unnecessarily.

[Means for Solving the Problems] The control device for a variable compression ratio engine of the present invention, which meets this objective, is configured to wait for switching for a certain period of time before switching the compression ratio in the vicinity of the switching boundary line of the compression ratio in the variable compression ratio engine. The system is equipped with a control device that sets an operating range for switching the ratio, distinguishes it from other immediate switching ranges, and suspends switching of the compression ratio for a certain period of time when the actual operating range is in the standby operating range.

[Operation] In the control device for the variable compression ratio engine described above, a plurality of different operating regions are set near the compression ratio switching boundary line, and when the operating region is in the standby operating region, switching of the compression ratio is suspended for a certain period of time. Because it is possible to
Compression ratio switching is less likely to be performed in an operating range where the effect of compression ratio switching is small, and the number of times the compression ratio is switched is reduced overall, making the variable compression ratio engine less susceptible to damage and improving durability.

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

1 and 2 show an embodiment of the present invention. In the figure, the same reference numerals as in A, B in FIG. 3 and FIG. 4 are given to parts to which A, B in FIG. 3 and FIG. 4 can be applied correspondingly. The inner circumference of the small end hole 5 of the connecting rod 3 and the piston pin 4
A cylindrical eccentric bearing 6 whose inner and outer peripheral surfaces are mutually eccentric is rotatably interposed between the outer periphery of the connecting rod 3 and the lock hole 9 provided in the eccentric bearing 6. engaging the lock pin 8 slidably and retractably inserted into the lock pin hole 7 of the lock pin hole 7;
By separating it, the rotation of the eccentric bearing 6 can be locked or freed. Since the eccentric bearing 6 has a locking hole 9 in its thick wall, in the locked position the relative position of the piston 2 with respect to the connecting rod 3 is high, and a high compression ratio is locked, and in the unlocked position, the piston 2 is compressed. Since it receives the explosive force at specific dead center and naturally maintains its relative position with respect to the connecting rod 3 at a low position, the compression ratio is locked at a low compression ratio. The locking pin 8 is engaged with or released from the locking hole 9 by applying hydraulic pressure to the locking hydraulic passage 10 or by applying hydraulic pressure to the unlocking hydraulic passage 11, and the switching is activated by a signal from the CPU 18. This is done by the switching valve 19.

The structure up to this point is shown in Figure 3, A, B and 4.
The structure is the same as or similar to the structure described in the figure.

In this embodiment, as shown in FIG. 2, A, B, C,
Four operating regions D are set. In Figure 2, the vertical axis shows the fuel efficiency (g/Kw・H),
The horizontal axis shows the engine load, A, B,
It shows changes in fuel efficiency at high compression ratio 21 and low compression ratio 22 in C and D operating regions. When the fuel efficiency rate (g/Kw・H) increases, the amount of fuel consumed over a given distance traveled increases, resulting in poor fuel efficiency.
When the fuel efficiency rate (g/Kw·H) becomes small, the amount of fuel consumed over a certain distance traveled becomes small.

At light and medium loads such as A and B operating areas,
A high compression ratio of 21 has a lower fuel consumption rate, that is, better fuel efficiency.

At high loads such as those in the C and D operating ranges, a high compression ratio of 21 is basically better in terms of fuel efficiency, but increasing the compression ratio tends to cause knocking and actually retards the ignition timing. As shown in the figure, the fuel consumption rate increases and fuel efficiency worsens. For this reason, C
In the and D driving ranges, the low compression ratio of 22 has better fuel efficiency.

However, in operating regions near the switching boundary line 20, such as operating regions B and C, there is almost no difference in fuel efficiency and fuel efficiency between the high compression ratio 21 and the low compression ratio 22. Therefore, the A and D operating ranges are set as operating ranges in which the compression ratio is immediately switched, and the B and C operating ranges are set as operating ranges in which the switching of the compression ratio is postponed for a certain period of time.

FIG. 1 shows the control of the embodiment of the present invention within the CPU 18. First, in step 25, the crank angle
An interrupt is made to the CPU 18 every 180°. In step 26, engine operating conditions such as the intake pipe negative pressure sensor 16 that detects the engine load as engine operating condition detection means, the engine rotation speed sensor 17, etc. are input, and the current operating range is input. , B, C, or D, and the process proceeds to step 27.

In step 27, it is determined whether the current compression ratio is a high compression ratio, and if the current compression ratio is a high compression ratio,
Proceed to step 28. In step 28, the current operating area is D.
If the current operating range is D, the process proceeds to step 29, where a wait flag is determined.
If the current compression ratio is a high compression ratio and belongs to the D operation region, as is clear from Figure 2, a low compression ratio of 22 will have a lower fuel consumption rate and better fuel efficiency. Moreover, since there is a significant difference between the high compression ratio 21 and the low compression ratio 22 in the D operating region, it is desirable to immediately switch to the low compression ratio.
Therefore, if the wait flag is set to 1 in step 29, the process proceeds to step 30, where the wait flag is set to 0, the timer is reset, and the wait state is cleared, and the process proceeds to step 31. In step 31, the compression ratio is switched to a low compression ratio, and the ignition timing and fuel injection amount are also controlled for the low compression ratio, and in step 32, the process returns. If the weight flag is not set to 1 in step 29, proceed directly to step 31, switch to a low compression ratio, control the ignition timing and fuel injection amount to a low compression ratio, and return in step 32. .

In step 28, if it is determined that the current operating region is not D, the process proceeds to step 33, where it is determined whether the current operating region is C or not. In step 34, the weight flag is determined. The current compression ratio is high compression ratio,
Furthermore, in the case of belonging to the C operation region, as shown in Fig. 2, a low compression ratio of 22 has a lower fuel consumption rate and better fuel efficiency, but a high compression ratio of 21 and a low compression ratio in the C operation region have a lower compression ratio. Since there is little difference in superiority, it is preferable to postpone switching the compression ratio for a certain period of time. Therefore, if the wait flag is set to 1 in step 34, the process proceeds to step 35, where it is determined whether or not a timer set to wait a certain period of time before switching to a low compression ratio has timed up. If the time has not expired, the process waits for switching to a lower compression ratio, then proceeds directly to step 32 and returns. If the time is up, there is no need to wait for switching, so proceed to step 36 and control the compression ratio to be switched to a low compression ratio, and also control the ignition timing and fuel injection amount for the low compression ratio, and proceed to step 32. to return. If the wait flag is not set to 1 in step 34, that is, if no wait signal is issued, the process proceeds to step 37, where the wait flag is set to 1.
After setting the timer to 0 and starting it, and postponing the switching of the compression ratio for a predetermined period of time, the process proceeds to step 32 and returns.

If it is determined in step 28 that the current operating range is not D, and if it is determined in step 33 that the operating range is not C, the process proceeds to step 38, where the weight flag is determined. If the wait flag is not set to 1, that is, if no wait signal is issued, the process directly proceeds to step 32 and returns. If the weight flag is set to 1, the wait flag is set to 0 in step 39 and the timer is reset, and the process proceeds to step 32 to return.

If it is determined in step 27 that the current compression ratio is a low compression ratio, the process proceeds from step 27 to step 40, where it is determined whether the operating region is A or not. If there is, the process proceeds to step 41, where the weight flag is determined. If the current compression ratio is a low compression ratio and belongs to the A operation region, from Figure 2, a high compression ratio of 21 has a lower fuel consumption rate and better fuel efficiency, and is also in the A operation region. Since there is a significant difference between the high compression ratio 21 and the low compression ratio 22 in the region, it is desirable to immediately switch to the high compression ratio. Therefore, if the wait flag is set to 1 in step 41, the process proceeds to step 42, where the wait flag is set to 0, the timer is reset, and the wait state is cleared, and the process proceeds to step 43. In step 43, the compression ratio is switched to a high compression ratio, and the ignition timing and fuel injection amount are also controlled for high compression ratio.
Returns in 2. The weight flag is 1 in step 41.
If it is not set, proceed directly to step 4.
3, the compression ratio is increased, the ignition timing and fuel injection amount are also controlled for the high compression ratio, and the process returns to step 32.

In step 40, if it is determined that the current operating region is not A, the process proceeds to step 44, where it is determined whether the current operating region is B. If the current operating region is B, In step 45, the weight flag is determined. The current compression ratio is low compression ratio,
Furthermore, in the case of belonging to the B operating region, as shown in Fig. 2, a high compression ratio of 21 has a lower fuel efficiency and better fuel efficiency, but in the B operating region, a high compression ratio of 21 and a low compression ratio of 22 Since there is almost no difference in superiority, it is preferable to suspend the compression ratio for a predetermined period of time. Therefore, if the weight flag is set to 1 in step 45, the process proceeds to step 46, where it is determined whether or not a timer set to wait a certain period of time before switching to a high compression ratio has timed out. If there is no time-up, the process waits for switching to a high compression ratio and then returns to step 32. If the time has elapsed, the process proceeds to step 43, where the compression ratio is switched to a high compression ratio, and the ignition timing and fuel injection amount are also controlled for a high compression ratio, and the process proceeds to step 32, where the process returns. If the weight flag is not set to 1 in step 45, the process proceeds to step 47, where the weight flag is set to 1 and the timer is set to 0.
After starting at 1 and suspending the switching of the compression ratio for a predetermined period of time, the process proceeds to step 32 and returns.

If it is determined in step 40 that the current operating region is not A, and furthermore, in step 44 it is determined that the operating region is not B, the process proceeds to step 48, where a weight flag is determined. If the wait flag is not set to 1, that is, if no wait signal is issued, the process directly proceeds to step 32 and returns. If the weight flag is set to 1 in step 49, the weight flag is set to 0 in step 49, the timer is reset, and step 32 is performed. Proceed to return.

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

When switching to a high compression ratio, lock hydraulic passage 1
0 is applied, and the lock pin 8 is urged toward the eccentric bearing. Since the eccentric bearing 6 is rotating, the tip of the biased lock pin 8 is guided by the guide groove 13, and the thickest part of the eccentric bearing 6 comes to the lowest position when it hits the wall of the lock hole 9. When it enters the locking hole 9, the rotation of the eccentric bearing 6 is locked in a high compression ratio state where the piston is at its highest position relative to the connecting rod.

When the compression ratio is low, pressure builds up in the lock pin unlocking oil passage 11, and the lock pin 8 is retracted into the lock pin hole 7, and when the piston receives an explosive load, the connection near the top dead center of the compression ratio The position relative to the bearing rod is eccentric bearing 6.
When the thin wall portion of the compressor reaches its lowest position, it is lowered and a low compression ratio state appears.

In this way, each time the compression ratio is switched, the lock pin 8 is engaged with or disengaged from the lock pin hole 7 or the lock hole 9, and the compression ratio is switched, so the durability of the lock pin 8, the lock pin hole 7, etc. is reduced. was becoming a problem. However, when the control device for a variable compression ratio engine of the present invention is applied, control is performed according to the above control block, and the operating ranges A, B,
In operating regions B and C where C and D are set and the compression ratio switching effect is small, compression ratio switching is postponed for a predetermined period of time, so the number of compression ratio switching is reduced.
Compression ratio switching devices such as the lock pin 8 and the lock pin hole 7 are more difficult to maintain than conventional devices. However, in operating regions A and D where the compression ratio switching effect is large, the compression ratio switching is performed immediately.

[Effects of the invention] When the present invention is based on a control device for a variable compression ratio engine, switching standby and non-switching operation regions are set near the compression ratio switching boundary line, and in the operating region where the compression ratio switching effect is small, Since compression ratio switching is postponed for a predetermined period of time to prevent unnecessary compression ratio switching, the number of compression ratio switching can be reduced and a decrease in the durability of the switching device can be prevented. can.

In this embodiment, the present invention has been described as being applied to a control device for an eccentric bearing type variable compression ratio engine.A sub-piston is provided in the space communicating with the combustion chamber, and the compression ratio can be varied by moving the sub-piston. A similar effect can be obtained even when applied to a type of device.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram of the functions of a control computer in a control device for a variable compression ratio engine according to an embodiment of the present invention, and FIG. A diagram of the relationship between area and compression ratio, A in Fig. 3 is a sectional view of an eccentric bearing type variable compression ratio engine, B in Fig. 3 is a partially enlarged sectional view in a direction perpendicular to A in Fig. 3, and Fig. 4 This figure is a system diagram of the compression ratio changing circuit of the variable compression ratio engine shown in A and B of FIG. 3. 6... Eccentric bearing as a variable compression ratio engine, A, B, C, D... Operating range.

Claims (1)

[Scope of utility model registration request] In a variable compression ratio engine, an operating region is set near the compression ratio switching boundary line in which the compression ratio is switched after waiting for a certain period of time to distinguish it from other immediate switching regions, and the actual operating region becomes a standby operating region. A control device for a variable compression ratio engine, comprising a control device that suspends switching of the compression ratio for a certain period of time.