JPH0430354Y2 - - Google Patents

Description

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

[Conventional technology]

In internal combustion engines, 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 in 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 to high loads, is increased during light loads. In this sense, many variable compression ratio mechanisms for internal combustion engines have been proposed.

A conventional variable compression ratio mechanism is constructed, for example, as shown in FIG. 2, A and B. In A and B of FIG. 2, 1 is a cylinder block, 2 is a piston, 3 is a connecting rod, and 4 is a piston pin.

The small end of the connecting rod 3 is a cylindrical body whose wall thickness changes in the circumferential direction between the small end hole 5 and the outer periphery of the piston pin 4, and whose inner and outer peripheries are offset 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 has become 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
Hydraulic pressure is sent to 1 from the crankshaft 12 side.

In the lock mechanism of the eccentric bearing 6, when the lock pin 8 is urged by the oil pressure from the oil passage 10, the lock pin 8 locks into the lock hole 9 without jumping over the lock hole 9 of the rotating eccentric bearing 6.
A guide groove 13 extending in the circumferential direction is provided in front of the lock hole 9 in the direction of rotation of the eccentric bearing so as to be inserted into the eccentric bearing. (Utility Model Publication No. 58-13782).

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, which controlled 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.

Normally, when a vehicle is running in an urban area, engine operating conditions change rapidly, and the engine load and engine rotational speed rapidly increase and decrease, so in conventional devices, the number of times the compression ratio is switched increases. Moreover, switching to a high compression ratio to reduce fuel consumption does not need to be done in such a hurry because knocking is not a problem, but it is controlled at each moment in the same way as switching to a low compression ratio. Therefore, the number of times the compression ratio is switched is unnecessarily increased.
A problem arises in that the durability of the variable compression 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.

In order to alleviate such problems, the
As disclosed in Japanese Patent No. 142020, it is considered effective to delay switching the compression ratio from a low compression ratio to a high compression ratio for a certain period of time.

[The problem that the idea aims to solve]

However, when the delay time is constant, if this constant delay time is set short, the number of times the compression ratio will be switched will increase when the amount of change in load or rotational speed is large, and the durability of the switching means will deteriorate. ,vice versa,
If a certain delay time is set to be long, a problem arises in that when the amount of change in load or rotational speed is small, the compression ratio is not switched immediately, and fuel efficiency cannot be improved very much.

This invention aims to improve durability by optimally reducing the number of times the compression ratio is switched in response to engine operating conditions without significantly deteriorating fuel efficiency. The object of the present invention is to provide a control device for a variable mechanism.

[Means to solve the problem]

The control device for a variable compression ratio mechanism of the present invention, which meets this purpose, is configured to control a variable compression ratio mechanism for an internal combustion engine when changing the compression ratio from a low compression ratio to a high compression ratio. The compressor is equipped with a control means that lengthens the time required to switch to a high compression ratio as the amount of change or the amount of change in engine speed increases.

[Effect]

In the control device for the variable compression ratio mechanism, when switching the compression ratio to a higher compression ratio is postponed for a predetermined period of time depending on changes in operating conditions, the larger the engine load change or the engine rotation speed change, the more Equipped with a control means that lengthens the time before switching to a high compression ratio (increases the delay time), so the delay time becomes small during calm operation (no sudden changes in load or rotational speed). It switches to a high compression ratio relatively quickly, improving fuel efficiency, and during heavy driving (sudden changes in load and rotation speed), the delay time increases, reducing the number of times switching to a high compression ratio increases durability. Improvements can be made. As a result, the number of times the compression ratio is switched is optimally reduced, and durability is optimally improved.

〔Example〕

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

FIG. 1 shows an embodiment of the present invention. In the figure, the same reference numerals as in A, B in FIG. 2 and FIG. 3 are given to parts to which A, B in FIG. 2 and FIG. Connecting rod 3
A cylindrical eccentric bearing 6 whose inner and outer circumferential surfaces are mutually eccentric is rotatably interposed between the inner circumference of the small end hole 5 and the outer circumference of the piston pin 4. A lock pin 8, which is slidably and retractably inserted into a lock pin hole 7 of a connecting rod 3, is engaged and disengaged with the provided lock hole to lock or free the rotation of the eccentric bearing 6. Since the eccentric bearing 6 has a locking hole in its thick wall, the piston 2 is in the locked position.
The relative position of the piston 2 to the connecting rod 3 is high and the compression ratio is locked at a high level. When the piston 2 is unlocked, the piston 2 receives the explosive force at compression top dead center and naturally lowers its relative position to the connecting rod 3. This results in 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.
This is done by a switching valve 19 operated by a signal from the CPU 18.

The structure up to this point is the same as or similar to the structure described in A and B of FIG.

FIG. 1 shows the control of the embodiment of the present invention within the CPU 18. First, in step 21, the crank angle
An interrupt is made to the CPU 18 every 180°. In step 22, engine operating conditions are input, for example, from 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., and in step 23, the optimum compression is determined according to the engine operating conditions. The ratio is determined and step 2
Proceed to step 4.

If it is determined in step 24 that a high compression ratio is better, the process proceeds to step 25, where it is determined whether the current compression ratio is high or not. , proceed directly to step 26 and return.

If the current compression ratio is a low compression ratio in step 25 even though it is determined that the compression ratio determined in step 24 is a high compression ratio, the process proceeds to step 27, where the weight flap is A tsug (wait flag) determination is made. weight flag is 1
In this case, that is, in a wait state (wait state), the process proceeds to step 28, and 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 the time has not expired, the system waits for switching to a high compression ratio, and then proceeds to step 26 and returns. Process 2
If the timer is up in step 8, go to step 29.
Then, 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. The process then proceeds to step 26 and returns. Step 27
If the wait flag is not set to 1, that is, if the waiting signal is not output, proceed to step 30, calculate the difference between the previous operating conditions and the current operating condition, and proceed to step 31. After setting the time-up time according to changes in conditions, step 32
In step 27, the weight flag is set to 1, a timer is started, and step 27 is set to postpone switching of the compression ratio for a predetermined period of time, and then the process proceeds to step 26 and returns.

The amount of time up is calculated from the following formula.

T=aR+bB (T: time up amount, R: engine speed change amount, B: engine load change amount, a, b: constant) In step 24, if it is desirable that the determined compression ratio is low, step 24 The process then proceeds to step 33, where it is determined whether the weight flag is 1 or not. If the wade flag is not set, that is, if it is 0, the process proceeds to step 35, where it is determined whether the current compression ratio is a high compression ratio. If the weight flag is set to 1 in step 33, it is desirable to lower the compression ratio quickly due to the problem of knocking, so proceed to step 34, set the weight flag to 0, and set the timer. Reset and proceed to step 35. In step 35, it is determined whether the compression ratio is high or low, and if the current compression ratio is a low compression ratio, the process directly proceeds to step 26 and returns. If the current compression ratio is a high compression ratio in step 35, the compression ratio is switched to a low compression ratio in step 36, and the ignition timing and fuel injection amount are also controlled for a low compression ratio.

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, 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 occurs. The position relative to the rod is lowered by bringing the thin walled portion of the eccentric bearing 6 to its lowest position, creating a low compression ratio condition.

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 the variable compression ratio mechanism of the present invention is applied, control is performed according to the above control block, and when the current compression ratio is controlled to a higher compression ratio, T=
Compression ratio switching is postponed for an optimal predetermined time determined by aR+bB. More specifically, during calm operation (load and rotation speed changes are not sudden), the delay time is small and the compression ratio is switched relatively quickly to improve fuel efficiency, while during heavy operation (load and rotation speed changes are not sudden), fuel efficiency is improved. When the number of compression ratios changes rapidly), the delay time increases and the number of times the compression ratio is switched to a high compression ratio is reduced, thereby improving durability. As a result, the number of times the compression ratio is switched is optimally reduced, and durability is optimally improved. However, when switching from a high compression ratio to a low compression ratio, knocking becomes a problem at a high compression ratio, so the switching is performed quickly.

[Effect of idea]

According to the control device for the variable compression ratio mechanism of the present invention,
The variable compression ratio mechanism is equipped with a control means that lengthens the time required to switch to a high compression ratio as the engine load or engine speed change increases when controlling from a low compression ratio to a high compression ratio. During calm driving, the delay time becomes small and the compression ratio is switched to a high compression ratio relatively quickly, improving fuel efficiency. During aggressive driving, the delay time becomes large and the number of times the system switches to a high compression ratio is reduced. The durability is improved, and as a result, the number of times the compression ratio is switched can be optimally reduced, and a decrease in the durability of the switching device can be optimally prevented.

[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 mechanism according to an embodiment of the present invention, A in Fig. 2 is a sectional view of an eccentric bearing type variable compression ratio mechanism, Fig. 2 B is a partial enlarged sectional view in the direction perpendicular to A in Fig. 2, and Fig. 3 is a partially enlarged sectional view in the direction perpendicular to
FIG. 3 is a system diagram of the compression ratio changing circuit of the compression ratio variable mechanism shown in A and B of the figure. 6... Eccentric bearing as a variable compression ratio mechanism, 16... Intake pipe negative pressure sensor as means for detecting engine operating conditions, 17... Engine rotation speed sensor as means for detecting engine operating conditions.

Claims (1)

[Scope of utility model registration request] In a variable compression ratio mechanism of an internal combustion engine, when switching the compression ratio from a low compression ratio to a high compression ratio, the larger the engine load change or the engine rotation speed change, the higher the compression ratio is until the compression ratio is switched to a higher compression ratio. 1. A control device for a variable compression ratio mechanism, comprising a control means for lengthening the time.