JPH0521635Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a control device for a variable displacement turbocharger that is applied to an internal combustion engine such as an automobile and controls a nozzle area according to an acceleration state.

(Prior Art) Generally, in order to increase the output of an internal combustion engine, it is necessary to increase the weight of air that the engine uses for combustion per unit time. Therefore, a method is adopted in which a turbocharger is used to force high-density air (supercharging).

If the turbine capacity is made variable in such a turbocharger, it becomes possible to increase the torque over a wide range from a low speed range to a high speed range, so variable displacement turbochargers have been proposed.

Conventional control devices for this type of variable displacement turbocharger include those described in, for example, Japanese Utility Model Application No. 53-50310, Japanese Patent Application Publication No. 58-176417, and Japanese Patent Application Publication No. 60-219418. Are known. Here, the method described in Japanese Unexamined Patent Publication No. 60-219418 will be described as an example.

This device has variable capacity means as shown in FIG. 10, and a turbine is housed in a central circular portion 71. A scroll 72 whose area gradually decreases toward the downstream in the direction indicated by arrow F is provided around the scroll 72, and its inlet portion 73 serves as a throat. A flap valve 74 for the purpose of varying the turbine capacity is provided here so as to be rotatable about a shaft 75. These configure the scroll inlet portion into a variable nozzle (hereinafter referred to as V/N). Therefore, the flap valve 74
5, the turbine capacity changes within a predetermined capacity, and at this time, the V/N of the inlet portion 73 of the scroll 72 also changes.

On the other hand, FIG. 11 is a diagram showing a mode of control by the variable capacity means, and shows a V/N control state with engine rotational speed Ne and engine shaft torque T as two axes. In the figure, curve E is the engine shaft torque characteristic when the throttle is fully open, and the point where the intake manifold internal pressure (supercharging pressure) reaches the specified value (for example, 350 m/mHg) when the V/N is fully closed. B _{L is} the point at which the intake manifold internal pressure reaches the specified value when the V/N is fully open. V/
A region C between the N fully closed boundary line and the V/N fully open boundary line is a V/N operating region where V/N changes from fully closed to fully open or from fully open to fully closed. Also, area Q
is the region where the V/N is fully closed, and region D is the region where the V/N is fully open and the exhaust bypass valve (waste gate valve:
This is the operating area of W/G). Note that the engine operating line in the figure is an example under certain conditions.

(Problem to be solved by the invention) However, in the case of such a conventional variable displacement turbocharger control device, it is necessary to compensate for the delay in controlling the V/N opening during engine acceleration, and to adjust the boost pressure during acceleration. Although it is possible to make the
Since the V/N opening degree was controlled based on the engine speed Ne and the engine shaft torque T (actually the engine intake air flow rate), the problem was that the engine shaft torque T fluctuated depending on the acceleration state. The dot was hot.

That is, for example, when the gear position of the transmission is 4th speed or higher, if the accelerator pedal is suddenly depressed from a low rotation range, the engine rotation speed Ne will not increase rapidly but will accelerate slowly. Therefore, the rise in boost pressure is gradual and the V/N opening is appropriately controlled, resulting in a well-balanced match between boost pressure and exhaust pressure, and the rise of engine shaft torque T is smooth. It is.

However, for example, when the gear position of the transmission is in first gear, if the accelerator pedal is suddenly depressed from a low rotation range, the engine rotation speed Ne suddenly shifts to a high rotation range. As a result, a large amount of exhaust gas flows into the turbine, but since the V/N opening is at its minimum, exhaust resistance increases, exhaust pressure rises above the boost pressure, and the engine shaft torque T drops. Put it away. this is,
This is because the V/N opening degree is controlled based on the intake air flow rate of the engine as described above, so there is a delay in controlling the V/N opening degree in response to an increase in the exhaust flow rate due to sudden acceleration.

Therefore, in such cases, the acceleration performance intended by the driver cannot be obtained, and the driving feeling of the vehicle deteriorates.

(Purpose of the invention) Therefore, the present invention changes the nozzle area according to the degree of acceleration when the engine shifts to an acceleration state, thereby making the nozzle area appropriate regardless of the sudden acceleration of the engine, and reducing the exhaust pressure. The purpose of this is to suppress transient increases in engine torque and reduce drops in engine torque, thereby improving vehicle drivability.

(Means for Solving the Problems) In order to achieve the above object, the control device for a variable displacement turbocharger according to the present invention has an operating state detection means for detecting the operating state of the engine, as shown in FIG. a, supercharging pressure detecting means b for detecting the supercharging pressure of intake air, and acceleration determining means c for determining engine acceleration from the operating state of the engine;
When the engine shifts to an acceleration state, the acceleration ratio calculation means d calculates a value correlated to the degree of acceleration of the engine, and when the value correlated to the degree of acceleration is small, the nozzle area becomes small or the value is area setting means e for setting the nozzle area of the variable displacement turbocharger according to the degree of acceleration of the engine so that the nozzle area becomes large when the engine is in an acceleration state; ,
When the acceleration state is entered, the nozzle area is maintained at the nozzle area set by the area setting means, and when the boost pressure increases to a predetermined value, the area control means f calculates a control value that maximizes the nozzle area; a nozzle variable means g that changes the nozzle area of the variable displacement turbocharger based on the output of the means;
It is equipped with

(Function) In the present invention, when the engine shifts to an acceleration state, the nozzle area of the variable displacement turbocharger is optimally set according to a value (acceleration degree) that correlates with the degree of acceleration at that time. For example, during sudden acceleration, the nozzle area is set to be larger, so that an excessive increase in exhaust pressure is suppressed and a drop in engine torque is reduced. Furthermore, since the nozzle area is set to be smaller during slow acceleration, a sufficient supercharging effect can be obtained and the rise of engine torque can be accelerated. Therefore, no matter what driving condition the vehicle is accelerating from, a drive feeling without a feeling of stepped engine torque can be obtained, and the drivability of the vehicle can be significantly improved. Note that the nozzle area of the turbocharger in the present invention is set to a fully open state (in other words, a position that does not obstruct the flow of exhaust gas) when the engine is not in an accelerating state or when the boost pressure is above a predetermined value. This reduces the number of opening and closing operations of the nozzle that are exposed to high-temperature exhaust gas, increasing the durability of the nozzle and improving control accuracy.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 8 are diagrams showing a first embodiment of the present invention.

First, the configuration will be explained. In FIG. 2, 1 is an engine, and intake air is supplied to each cylinder from an air cleaner 2 through an intake pipe 3 and an intake manifold 4 sequentially, and fuel is injected by an injector (not shown). A spark plug 5 is installed in each cylinder (only one cylinder is shown in the figure).
The spark plug 5 is supplied with a high voltage pulse Pi from a high pressure generating unit 6. The spark plug 5 and the high pressure generating unit 6 constitute an ignition means 7 for igniting the air-fuel mixture, and the ignition means 7 generates and discharges a high pressure pulse Pi based on the ignition signal Sp. and,
The air-fuel mixture in the cylinder is ignited and exploded by the discharge of the high-pressure pulse Pi, and is discharged from the exhaust pipe 8 as exhaust.

A compressor 11 of a variable displacement turbocharger 10 is disposed in the intake pipe 3, and the compressor 11 is connected to a turbine 12 disposed in the exhaust pipe 9. The turbocharger 10 uses exhaust gas to drive a turbine 12, and a compressor 11 that is linked to the turbocharger 10 supercharges intake air.

The intake air flow rate Qa is detected by an air flow meter 14 and controlled by a throttle valve 15 in the intake pipe 3. The opening Cv of the throttle valve 15 is detected by a throttle valve opening sensor 16, the intake supercharging pressure Pa is detected by a supercharging pressure sensor (supercharging pressure detection means) 17,
Furthermore, the engine speed Ne is determined by the crank angle sensor 1.
8.

The turbocharger 10 has a scroll 19 formed to surround the turbine 12, as shown in FIG. Therefore, it is formed to gradually become smaller. A movable tongue portion 22 constituting a flap valve is provided at the confluence of the introduction passage 20 to the scroll 19 and the terminal end 21 of the scroll 19, and the movable tongue portion 22 is configured to expand and contract the cross-sectional area of the introduction passage 20. , its base end is rotatably supported by a shaft 23.

The movable tongue 22 is connected to the turbine 12 in FIG.
It is disposed in the exhaust pipe 9 near the upstream side, which is the introduction passage 20 to the exhaust pipe 9. Further, a shaft 23 rotatably supporting the movable tongue portion 22 is connected to the rod 2 via an arm 24.
The lower end of the rod 25 is connected to a diaphragm 27 constituting an actuator 26 for driving the movable tongue. In the case 28 that houses the diaphragm 27, the atmospheric chamber 29 is divided into a positive pressure chamber 30 by the diaphragm 27.
A spring 31 biased to push the diaphragm 27 toward the positive pressure chamber 30 is provided.

The boost pressure Pa on the downstream side of the compressor 11 is supplied to the positive pressure chamber 30 through the connecting pipe 32.
A solenoid valve 33 is disposed in the middle of 2. Solenoid valve 3
3 is a variable capacitance signal Sv having a duty control value
Based on this, the release ratio of the connecting pipe 32 to the atmosphere is controlled, and the larger the duty value is, the larger the release ratio is. Therefore, when the duty value increases, the pressure in the positive pressure chamber 30 decreases and the diaphragm 27 moves downward under the action of the spring 31. 22, the movable tongue portion 22 rotates in a direction that makes the exhaust gas introduction passage 20 to the turbine 12 smaller, that is, in a direction that closes it.
As a result, the flow rate supplied to the turbine 12 increases, and the supercharging pressure Pa applied to the engine 1 by the compressor 11 increases. On the other hand, as the duty value decreases, the opening rate of the solenoid valve 33 decreases and the pressure in the positive pressure chamber 30 increases, so the diaphragm 27 moves upward against the spring 31, and the movable tongue portion 22 moves upward. Rotates in the direction to open the introduction passage 20. As a result, the flow rate supplied to the turbine 12 becomes slower, and the supercharging pressure Pa applied to the engine 1 by the compressor 11 decreases. The actuator 26 and the movable tongue portion 22 constitute a nozzle variable means.

In addition, at the connection part between the exhaust bypass passage 34 that bypasses the turbine 12 and the exhaust manifold 8,
A wastegate valve 35 is provided. The waste gate valve 35 is connected to one end of a rod 38 via an arm 36 and a connecting member 37, and the other end of the rod 38 houses a diaphragm 40 that is connected to a diaphragm 40 of an actuator 39 for driving the waste gate valve. The case 41 has an atmospheric chamber 42 and a positive pressure chamber 43 by a diaphragm 40.
The atmospheric chamber 42 has a spring 44 biased to push the diaphragm 40 toward the positive pressure chamber 43.
is provided. The boost pressure Pa downstream of the compressor 11 is supplied to the positive pressure chamber 43 through a connecting pipe 45, and a solenoid valve 46 is disposed in the middle of the connecting pipe 45. The electromagnetic valve 46 controls the release ratio of the connecting pipe 45 to the atmosphere based on the bypass control signal S _B having a duty control value, and the larger the duty value, the larger the release ratio. Therefore, when the duty value increases, the pressure in the connecting pipe 45 decreases and the diaphragm 40 moves downward under the action of the spring 44, and this moving action causes the rod 3 to move downward.
8, the signal is transmitted to the waste gate valve 35 via the connecting member 37 and the arm 36, and the valve 35 moves in a direction to close the bypass passage 34. Furthermore, as the duty value decreases, the opening rate of the solenoid valve 46 decreases and the pressure in the positive pressure chamber 43 increases, so the diaphragm 40 moves upward against the spring 44, and the wastegate valve 35 is thereby Move in the direction of opening. The waste gate valve 35 is used to prevent the supercharging pressure Pa of the intake air supplied to the engine 1 by the turbocharger 10 from becoming too high and damaging the engine 1 when the engine 1 is in a high speed and high load state. , engine 1
A part of the exhaust gas is discharged to the outside, thereby reducing the amount of exhaust gas supplied to the turbine 12 so that an appropriate boost pressure Pa can be introduced into the engine 1.

Signals from the sensors 14, 16, 17, and 18 are input to a control unit (C/U) 52, and the control unit 52 controls the nozzle area based on information from these sensors.

That is, the control unit 52 has the functions of an acceleration determination means, an acceleration sum calculation means, an area setting means, and an area control means by itself, and also functions as an operating state detection means together with the throttle valve opening sensor 16 and the crank angle sensor 18. It is composed of a microcomputer consisting of a CPU, ROM, RAM, I/O ports, etc. Then, the processing values necessary for the nozzle opening degree and boost pressure are calculated from the above sensor information, and the nozzle area variable signal Sv
By outputting and bypass control signal S _B ,
The movable tongue portion 22 is appropriately controlled according to the operating condition to prevent a decrease in torque even during sudden acceleration in a wide range of operating ranges from low speed ranges to high speed ranges.

Next, the effect will be explained.

FIG. 4 is a flowchart showing a nozzle area control program, and in the figure, P ₁ to P ₁₁ indicate each step of the flow. This program is executed, for example, once every predetermined time.

First, read the opening Cv of the throttle valve 12 due to depression of the accelerator pedal at P ₁ , and read this opening Cv at P _2.
is compared with a predetermined value Cv′. The predetermined value Cv′ is the throttle valve 12
opening degree (in other words, the amount of accelerator pedal depression)
This is a parameter for determining whether or not the engine 11 is in an acceleration state based on the opening degree of the throttle valve 12.
When Cv is less than a predetermined value Cv'(Cv≦Cv'), it is determined that there is no acceleration state, and the opening degree Cv of the throttle valve 12 is set to a predetermined value.
When Cv' is exceeded (Cv>Cv'), it is determined that the vehicle is in an accelerating state. If it is determined that the acceleration is in progress (Cv>Cv′), the engine speed Ne is read in P ₃ , the engine speed Ne′ Δt seconds after the previous routine execution is read in P ₄ , and the engine speed is stopped in P ₅ . RPM increase rate (value correlated to degree of acceleration)
ΔNe/Δt is calculated according to the following formula.

ΔNe/Δt=Ne′−Ne/Δt...Next, in P ₆ , calculate the engine speed increase rate (ΔNe/Δt) from the table map shown in Figure 5.
The nozzle area V (amount of nozzle opening) corresponding to is looked up, and the movable tongue portion 22 is controlled based on this nozzle area V at _P7 . Therefore, when the engine speed increase rate (ΔNe/Δt) is small (during slow acceleration), the nozzle area is small, whereas when the engine speed increase rate (ΔNe/Δt) is large (during rapid acceleration), the nozzle area is small. The area is controlled to be large.

Then read the current boost pressure P _B at P ₈ and read it at P ₉
This boost pressure P _B is compared with the target boost pressure P _B '. Here, when the boost pressure P _B is equal to or smaller than the target boost pressure P _B ′ (P _B ≦P _B ′), it is determined that the engine is in a normal supercharging state, and the boost pressure P _B is Target boost pressure
When it is larger than P _B ′ (P _B >P _B ′), it is determined that the overboost state is present. If it is determined that the normal supercharging condition is present (P _B ≦P _B '), the process returns to step _P1 and this routine is repeatedly executed.

Also, it is in an overboost state (P _B >
P _B ′), proceed to step P ₁₀ and move the movable tongue 22
After fully opening, return to step _P9 and repeat the same process. Therefore, the boost pressure P _B is always controlled to the optimum boost pressure.

On the other hand, if it is not in the acceleration state at step _P2 (Cv≦Cv'), the process advances to step _P11 and the movable tongue portion 2
After fully opening 2, return to step _P1 . Therefore, when the opening degree of the throttle valve 12 is below a predetermined value (for example, during low speed operation), the movable tongue portion 22
is fully opened and the nozzle area is maximized,
Exhaust pressure does not increase (in other words, supercharging is not performed), and fuel efficiency is particularly improved.

Here, in the case of a variable displacement turbocharger control device, the operating condition of the engine 1 and the nozzle area (nozzle opening amount) of the exhaust turbocharger 10 are
Accordingly, the characteristics of boost pressure, exhaust pressure, and engine torque differ. Therefore, when the engine operating status is during sudden acceleration and slow acceleration, and when the nozzle area is A (minimum area: nozzle fully closed), B (intermediate area: nozzle medium opening), and C (maximum area: nozzle fully open). Each of the above characteristics will be explained.

First, during sudden acceleration, the characteristics are as shown in FIG. That is, when the nozzle area is A, a large amount of exhaust gas flows into the turbine and the supercharging pressure increases, but since the nozzle area is small, the increase in exhaust pressure is higher than the supercharging pressure, and the intake air filling efficiency deteriorates.
Therefore, the engine torque temporarily drops.

Further, when the nozzle area is B, the necessary nozzle area is secured even if a large amount of exhaust gas flows into the turbine, so that it is possible to obtain a sufficient boost pressure increase while reducing the exhaust pressure. Therefore, engine torque also increases smoothly.

Further, when the nozzle area is C, even if a large amount of exhaust gas flows into the turbine, the nozzle area is large, so the exhaust gas inflow speed is low, and although an increase in exhaust pressure can be avoided, the increase in supercharging pressure becomes gradual. Therefore, the rise of engine torque is delayed.

On the other hand, during slow acceleration, the characteristics are as shown in FIG. That is, when the nozzle area is A, even if the inflow amount of exhaust gas is small, the nozzle area is small, so the exhaust speed is high, and the supercharging effect can be improved. Therefore, the engine torque builds up quickly.

Furthermore, when the nozzle areas are B and C, the amount of exhaust gas flowing in is small and the nozzle area is also large, so the boost pressure increases extremely slowly. Therefore, the rise of engine torque is also extremely slow. In this way, there is an optimum value for engine torque generation depending on the operating state of the engine (in other words, the acceleration state) and the nozzle area.

Therefore, in the variable displacement turbocharger control device of the present invention, the nozzle area (nozzle opening amount) is appropriately controlled according to the magnitude of engine acceleration (engine speed increase rate ΔNe/Δt) and boost pressure. ing. In other words, during sudden acceleration (when the engine speed increase rate ΔNe/Δt is large), the nozzle area becomes B (intermediate area: medium opening degree) in Figure 6 above.
to the C (maximum area: fully open) side.
As a result, even if the engine speed suddenly increases and a large amount of exhaust gas flows into the turbine, the required nozzle area is secured, making it possible to obtain sufficient boost pressure while reducing exhaust resistance. I can do it. Therefore, unlike the prior art, a drop in engine torque due to an increase in exhaust pressure is prevented.

In addition, during slow acceleration (when the engine speed increase rate ΔNe/Δt is small), the nozzle area is set to the A (minimum area: fully closed) side in Figure 7, so the engine speed decreases. Even if the rise is slow, a sufficient supercharging effect can be obtained, and the engine torque can be built up quickly. Therefore, no matter what driving condition the vehicle is accelerated from, a drive feeling without a feeling of stepped engine torque can be obtained, and the drivability of the vehicle can be significantly improved.

8 and 9 are diagrams showing a second embodiment of the present invention. In FIG. 8, 61 is a double entry type turbocharger, and a turbine housing 62 of the turbocharger has scrolls 63, 64.
is formed. The scrolls 63 and 64 have different nozzle areas,
On the upstream side (engine side) of the scrolls 63, 64, shutoff valves 65, 66 as shown in FIG.
6a and shaft portions 65b and 66b. Further, the shaft portions 65b, 66b are fixed to the operating shaft of an actuator (not shown), and the actuator operates based on the output from the area control means to open and close the shutoff valves 65, 66 in an ON/OFF manner. The above actuator and shutoff valve 6
5 and 66 constitute a nozzle variable means 67. Therefore, in this embodiment, although the aspect of the variable nozzle is different, the same effects as in the first embodiment can be obtained.

Although the second embodiment has been described in which a single turbocharger is provided, the present invention is not limited to this embodiment. For example, it is also possible to use a plurality of turbochargers and perform similar control. be.

(Effects) According to the present invention, the nozzle area of the variable displacement turbocharger is optimally set according to the value correlated to the degree of acceleration of the engine (acceleration degree).
When the value that correlates with the degree of acceleration is large, the nozzle area can be set to be large to suppress an excessive increase in exhaust pressure and reduce a drop in engine torque. Further, when the value correlated to the degree of acceleration is small, the nozzle area can be set to be small to obtain a sufficient supercharging effect and to accelerate the rise of engine torque. Therefore, no matter what driving condition the vehicle is accelerated from, it is possible to obtain a drive feeling without a feeling of stepped engine torque, and the drivability of the vehicle can be significantly improved. Note that the nozzle area of the turbocharger in the present invention is set to a fully open state (in other words, a position that does not obstruct the flow of exhaust gas) when the engine is not in an accelerating state or when the boost pressure is above a predetermined value. This reduces the number of opening and closing operations of the nozzle that is exposed to high-temperature exhaust gas, improves the durability of the nozzle, and improves control accuracy.

[Brief explanation of drawings]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 8 are diagrams showing a first embodiment of the invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a main part of the variable displacement turbocharger. 4 is a flowchart showing the nozzle area control program, FIG. 5 is a table map showing the relationship between the engine speed increase rate (ΔNe/Δt) and nozzle area V, and FIG. 6 is a flowchart showing the nozzle area control program. Figure 7 is a diagram showing the relationship between boost pressure, exhaust pressure, and engine torque during rapid acceleration. Figure 7 is a diagram showing the relationship between boost pressure, exhaust pressure, and engine torque during slow acceleration. Figures 8 and 9 are from this book. FIG. 8 is a cross-sectional view of a main part of the double entry type turbocharger, FIG. 9 is a diagram showing a shutoff valve provided on the scroll, and FIG.
0 and 11 are diagrams showing a conventional variable displacement turbocharger, and FIG. 10 is a sectional view of the main part thereof.
FIG. 1 is a diagram showing the V/N control mode. 1...engine, 10,61...turbocharger, 16,18,52...(operating state detection means), 17...supercharging pressure sensor (supercharging pressure detection means),
22, 26, 67... Nozzle variable means, 52...
(Acceleration determination means, acceleration sum calculation means, area setting means, area control means).

Claims (1)

[Scope of Claim for Utility Model Registration] a. Operating condition detection means for detecting the operating condition of the engine; b. Boost pressure detection means for detecting the supercharging pressure of intake air; c. Determining the acceleration of the engine from the operating condition of the engine. acceleration determination means; d. acceleration amount calculation means for calculating a value correlated to the degree of acceleration of the engine when the engine shifts to an acceleration state; e. or an area setting means for setting the nozzle area of the variable displacement turbocharger according to the degree of acceleration of the engine so that the nozzle area becomes large when the value is large; f a nozzle of the variable displacement turbocharger when the engine is not in an acceleration state; Maximize the area, while
Area control means for maintaining the nozzle area at the nozzle area set by the area setting means when transitioning to the acceleration state, and calculating a control value to maximize the nozzle area when the supercharging pressure increases to a predetermined value; A control device for a variable displacement turbocharger, comprising: a nozzle variable means for changing the nozzle area of the variable displacement turbocharger based on the output of the means.