JPH02163429A - Variable compression ratio controller for engine equipped with supercharger - Google Patents

Abstract

PURPOSE:To improve the acceleration performance by delaying the switching to the low compression ratio side of a variable compression ratio mechanism even if an engine shifts to a the low revolution high load region in acceleration, until the supercharge pressure reaches a prescribed value. CONSTITUTION:The number of engine revolution, engine load, catalyst temperature, and an acceleration signal are inputted into a control unit 15. When the prescribed acceleration state is detected, and the state on the start of acceleration is in the prescribed low revolution speed low load region, a high compression ratio is maintained for a certain time by a delay timer. In the state other than the acceleration state, if the catalyst temperature is over an activation temperature, the high compression ratio is maintained, while if the catalyst tempera ture is below the activation temperature, the low compression ratio state is maintained, and the exhaust gas temperature is raised to accelerate the activation of a catalyst. In the stationary operation, the compression ratio of the engine is controlled to the high compression ratio side in the low revolution speed low load region, while in the low revolution speed high load region, the compression ratio is controlled to the low compression ratio side. There fore, the delay in the increase of the supercharge pressure in the initial stage of acceleration is offset by the torque up due to the high compression ratio, and the acceleration response can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to control of a variable compression ratio mechanism in a supercharged engine.

(Prior art) In a supercharged engine, a bypass passage is usually provided to bypass the exhaust turbine, and when the boost pressure exceeds a set value, this bypass passage is opened to reduce the driving force of the supercharger and reduce supercharging. It is equipped with a supercharging pressure control means such as a so-called waste gate system that suppresses the rise in pressure.

By the way, in these models equipped with a boost pressure control means such as the wastegate method, if the maximum boost pressure setting is always kept constant, a temporary high output is required, such as when the engine is accelerating. For example, Japanese Patent Application Laid-Open No. 57-1460
As described in Publication No. 23, it is known to improve engine output by substantially increasing the opening pressure of the wastegate valve during acceleration and increasing the maximum boost pressure. . However, for example, in the case of full-throttle acceleration from a low-speed, low-load state, the engine speed increases due to the fact that the energy of the exhaust gas is originally low in this low-speed, low-load region, and the moment of inertia of the exhaust turbo itself is large. Due to this delay (so-called turbo lag), the supercharging pressure does not rise as expected. Therefore, it is difficult to obtain sufficient acceleration performance by increasing the maximum supercharging pressure setting as described above.

Therefore, in such a region where the supercharging pressure does not increase, it is necessary to take measures to compensate for this. As one such method, the use of a variable compression ratio mechanism described in, for example, Japanese Utility Model Application Publication No. Sho 62-3952 is being considered. The variable compression ratio mechanism described in the publication has a lock bin engagement hole in an eccentric bearing interposed between a piston pin and a connecting rod, and engages and disengages the lock bin provided on the connecting rod side with the engagement hole using hydraulic pressure. This structure is designed to change the relative position of the piston with respect to the connecting rod.

However, the above-mentioned variable compression ratio mechanism is usually configured to have a high compression ratio in the low-speed, low-load region to improve fuel efficiency, and a low compression ratio in the low-speed, high-load region to prevent knocking. Therefore, during full-throttle acceleration from a low rotation and low load range, the compression ratio switches to the low compression ratio side, making it impossible to function to compensate for the delay in boost pressure rise.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and it improves fuel efficiency by setting a high compression ratio in the low-speed, low-load range, and prevents knocking by setting a low compression ratio in the low-speed, high-load range. The aim is to improve acceleration performance by taking advantage of the variable compression ratio mechanism that can reduce the delay in boost pressure rise at the initial stage of acceleration of a supercharged engine. do.

(Structure of the Invention) In the present invention, when a supercharged engine is fully accelerated from low rotation and low load, there is a delay in the increase in rotation of the supercharger, so the engine output at the beginning of acceleration is in a state without supercharging. Focusing on the fact that the torque characteristic is in line with the torque characteristic at It was discovered that by configuring the control system so that the ratio mechanism is held at the high compression ratio side without immediately switching to the low compression ratio side, it is possible to increase torque due to a high compression ratio. As shown in Figure 1. That is, the variable compression ratio control device for a supercharged engine according to the present invention includes a variable compression ratio mechanism in a supercharged engine, and a variable compression ratio mechanism in which the engine is in a low rotation and low load region or in a low rotation and high load region. loaded part detection means for detecting whether the
A control signal is generated to control the variable compression ratio mechanism to a high compression ratio side when the engine is in a low rotation and low load range! a second control signal generating means for generating a control signal for controlling the variable compression ratio mechanism to a low compression ratio side when the engine is in a low rotation high load range; switching control means for switching the output of the control signal generation means and outputting it as a control signal for the variable compression ratio mechanism; acceleration detection means for detecting the acceleration state of the engine; and high compression by the switching control means when acceleration is detected. The present invention is characterized in that it includes acceleration correction means that delays switching of the control signal from the ratio side to the low compression ratio side until the boost pressure reaches a predetermined value.

(Operation) The variable compression ratio mechanism is controlled to a high compression ratio side when the engine is in a low rotation and low load range, and is controlled to a low compression ratio side when the engine is in a low rotation and high load range in a steady state.

Also, during acceleration, when the engine shifts to a low-speed, high-load range, the variable compression ratio mechanism does not immediately switch to the low compression ratio side, but delays it until the boost pressure reaches a predetermined value and lowers the compression ratio. Switch to the side.

(Example) Examples will be described below based on the drawings.

FIG. 2 shows the complete closure of the variable compression ratio mechanism in the engine with exhaust turbo supercharger according to the first embodiment of the present invention. In this embodiment, the pin boss portions 2a, 2b of the piston l
A piston pin 3 is fitted into the piston pin 3. piston pin 3
has an eccentric portion 3a in the center in the axial direction, and a connecting rod 4 is connected to the eccentric portion 3a, thus forming an eccentric piston pin whose axial center is eccentric with respect to the center of the connecting rod small end portion 4a. A pin pole 5 that opens toward the connecting rod large end 4b is provided on the inner periphery of the connecting rod small end 4a, and a pin pole 5 that opens toward the connecting rod large end 4b is provided on the outer periphery of the eccentric portion 3a of the piston pin 3. That is, the eccentric part 3a
At both ends of the line connecting the center of and the axis of piston pin 3,
A pinhole 6.7 corresponding to the pinhole 5 on the connecting rod small end 4a side is opened. A lock pin 8 is provided in the pin hole 5 on the inner peripheral side of the connecting rod small end 4a.
is loosely fitted. The pinhole 5 on the small end 4a side has a bottle sliding part deeper than the length of the lock pin 8,
A hydraulic passage 10 is opened at the bottom and communicates with M1'iR9 of the connecting rod large end 4b.

On the other hand, the two pinholes 6.7 on the outer circumferential side of the eccentric portion 3a are provided with bottle sliding portions that are shallower than the length of the lock pin 8. The lock pin 8 can be completely housed in the inner pinhole 5, and the outer pinhole 6.7
When an upward inertial force is applied in a state aligned with either of these pin holes 6.7 on the outer peripheral side, the pin holes 6.7 are engaged with each other.

The oil groove 9 of the connecting rod large end 4b is connected to the crankshaft 11.
Hydraulic passage formed in! 2 to a hydraulic pressure supply passage 13, and this hydraulic pressure supply passage 13 includes a solenoid control valve 1.
4 is interposed. This control valve 14 turns on and off the hydraulic pressure.

When switching the compression ratio, the hydraulic pressure acting on the lock pin 8 is switched on by the control valve I4 near the bottom dead center of the piston. At this time, since the inertia of the lock pin 8 is acting downward, the lock pin 8 is removed from the outer pin hole 6.7 and completely enters the inner pin pole 5 due to its own inertia. Thereby, the piston pin 3 becomes free in the rotational direction with respect to the connecting rod 4. In the case of switching from a high compression ratio to a low compression ratio, the hydraulic pressure is turned back on near the compression top dead center, and during that time the piston pin 3 is moved by the downward inertia of the piston l and the cylinder pressure. The low compression ratio position is reached after a half turn from the low compression ratio position. Then, at that position, the lock pin 8 is actuated by its own -L direction inertia force and oil pressure, and engages with one pinhole 6 to fix the piston pin 3 at the low compression ratio position. In addition, 1. When switching from a low compression ratio to a high compression ratio, after similarly setting the piston pin 3 free, turn the hydraulic pressure back on near the intake top dead center. The upward inertia force causes the lock pin 9 to rotate half a turn to the high compression ratio position, at which point the lock pin 9 engages with the other pin hole 7.8 by its own inertia force and hydraulic pressure, and the piston pin 3
is fixed at the high compression ratio position.

The solenoid control valve 1 =1 is controlled by the control unit 15 as shown in FIG.

The control unit 15 receives various information such as engine speed, engine load (intake pipe pressure), catalyst temperature, and acceleration signal. As the acceleration signal, for example, a change in intake air amount, a change in engine speed, a change in throttle opening, etc. are used. Then, when a predetermined acceleration state @ (full throttle acceleration) is detected and the state at the start of acceleration is in the predetermined low rotation and low load region shown by A in FIG. Maintain high compression ratio.

Also, when the catalyst temperature is not in the acceleration state, it depends on whether the catalyst temperature has reached the activation temperature or not. If it has reached the activation temperature, the compression ratio is set to high, but if it has not reached the activation temperature, the compression ratio is set to the low compression ratio state. This will increase the exhaust gas temperature and accelerate the activation of the catalyst. This prevents delays in catalyst activation, especially during cold starts, making it possible to improve both warm-up performance and emission performance as well as fuel efficiency. In addition, during steady operation, the compression ratio of the engine is controlled to the high compression ratio side in the low rotation and low load area, and is controlled to the low compression ratio side in the low rotation and high load area.

Next, the control of this embodiment will be explained with reference to the flowchart of FIG.

When the vehicle is started, an acceleration determination is first made, and if it is determined that the vehicle is in a predetermined acceleration state, then it is checked whether or not the initial acceleration was within region A shown in FIG.

If the initial state has exceeded the A range, the high compression ratio state is maintained for a certain period of time, and after the certain period of time has elapsed, the compression ratio state is controlled to be low.

Further, even if the engine is in an acceleration state, if the initial acceleration time is not within the A region, the compression ratio state is immediately controlled to a low compression ratio state.

If the acceleration state is not determined, then it is checked whether the catalyst temperature has reached the activation temperature, and if it has reached the activation temperature, the compression ratio is controlled to a high compression ratio state, and if it has not reached the activation temperature, the compression ratio state is controlled to a low compression ratio state.

In the above embodiment, a delay timer is used to delay switching from a high compression ratio to a low compression ratio at the beginning of acceleration, and this makes it easy to correct acceleration until the boost pressure reaches a predetermined value. can be done. However, if you directly check whether the boost pressure has reached a predetermined value during acceleration and control the compression ratio based on that, you can achieve more precise control than with a delay timer. This makes it possible to achieve both knock resistance and acceleration performance more satisfactorily. A concrete example of this is the second embodiment described below.

In this second embodiment, the variable compression ratio mechanism is the same as that of the first embodiment shown in FIG.

The control system is as shown in FIG. 6, with a control unit 15 controlling the solenoid control valve 14.
Information such as catalyst temperature, boost pressure, and acceleration signal is input to the . When a predetermined acceleration state is detected, the high compression ratio state is maintained until the boost pressure reaches the set value. Furthermore, when the boost pressure reaches the set value, the engine is controlled to a low compression ratio state as in the steady state, since the engine is at low rotation and high load.

The set value for this supercharging pressure determination is determined in advance according to each operating region within a range below the supercharging pressure at the time of steady full opening. Furthermore, when the engine is not accelerating, the same control as in the first embodiment is performed depending on whether the catalyst temperature has reached the activation temperature.

FIG. 7 is a flowchart for executing control in this embodiment.

It starts and first determines whether it is in an acceleration state. If it is in the acceleration state, then check whether the boost pressure has reached the set value, maintain the high compression ratio state until the boost pressure reaches the set value, and then If the compression ratio has been reached, the compression ratio is controlled to be low.

Also, when it is determined that the engine is not in an acceleration state, it is checked whether the catalyst temperature has been reached, and if it has reached the catalyst temperature, it is controlled to a high compression ratio state, and if it has not been reached, it is controlled to a low compression ratio state.

Note that the present invention can also be applied to an engine equipped with a mechanical supercharger.

(Effects of the Invention) Since the present invention is configured as described above, it is possible to improve fuel efficiency and anti-knock performance by using a variable compression ratio, and to compensate for the delay in boost pressure rise at the beginning of acceleration by increasing torque by using a high compression ratio. Supplementary acceleration response can be improved.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the present invention, FIG. 2 is an overall diagram of a variable compression ratio mechanism in a first embodiment of the present invention, FIG. 3 is a control system diagram of the same embodiment, and FIG. 4 is an implementation diagram of the same embodiment. FIG. 5 is a flowchart for executing the control of the example, FIG. 6 is a control system diagram of the second embodiment of the present invention, and FIG. 7 is a flowchart for executing the control of the example. This is a flowchart. l: piston, 3: piston pin, 3a: eccentric part, 4:
Connecting rod, 8: Lock bin, 10/hydraulic passage, 14:
Solenoid control valve, 15: Control unit.

Claims (1)

[Claims] (1) In a supercharged engine, a variable compression ratio mechanism,
load state detection means for detecting whether the engine is in a low rotation, low load region or a low rotation, high load region; and when the engine is in a low rotation, low load region, the variable compression ratio mechanism is set to a high compression ratio side. a first control signal generating means for generating a control signal for controlling the engine; and a first control signal generating means for generating a control signal for controlling the variable compression ratio mechanism to a low compression ratio side when the engine is in a low rotation and high load range. a switching control means for switching the outputs of these two control signal generation means and outputting them as a control signal for the variable compression ratio mechanism; an acceleration detection means for detecting the acceleration state of the engine; A supercharger characterized by comprising an acceleration correction means that, when detected, delays the switching of the control signal from the high compression ratio side to the low compression ratio side by the switching control means until the supercharging pressure reaches a predetermined value. Variable compression ratio control device for the attached engine.