JPS6056128A - Control device for variable displacement type turbo-charger - Google Patents

Abstract

PURPOSE:To aim at increasing the supercharged pressure, by providing such an arrangement that the passage area of an exhaust gas introduction passage led to a turbine is made variable with the use of a displacement changing means which is controlled in accordance with the rotational speed and load of the engine, and the above- mentioned passage area is narrowed to such a limit that no knocking occurs. CONSTITUTION:A movable reed part 42 is swingably disposed in an introduction passage section for the turbine scrol of a turbo-charger 25 so that the passage area of introduction exhaust gas is made variable. This movable reed 42 is rotated by a vacuum actuator 46 through a rod 44, etc. Further, the vacuum actuator 46 is controlled by a control pressure which is produced by a vacuum pump 54 and is regulated in accordance with the opening degree of a solenoid valve 56. This solenoid valve 56 controls the passage area of the introduction passage to narrow the latter to such a limit that no knocking occurs in accordance with a control signal which is obtained by compensating, in accordance with the output of a knock sensor 33, a basic control value which is set in the control unit 29 in accordance with the outputs of an air-flowmeter 24 and a crank angle sensor 32.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a control device for a variable displacement turbocharger.

(Prior art) Generally, the boost pressure of a turbocharged engine is controlled by an exhaust bypass mechanism that bypasses exhaust gas and reduces the flow rate flowing into the turbine, and the turbine inlet pressure is uniquely determined by the turbine capacity. be done. Therefore, using a small-flow turbine increases torque at low speeds but reduces torque at high speeds, and using a high-flow turbine increases l-lux at high speeds but reduces torque at medium and low speeds. . Therefore, variable displacement turbochargers have been proposed that can vary the capacity of a turbine depending on the operating state of the engine and increase torque from a low speed range to a high speed range.

As a conventional variable displacement turbocharger and its control device, for example, one described in Japanese Utility Model Application Laid-Open No. 53-50310 is known, and is shown as shown in Fig. 1.2. In FIG. 1, reference numeral 1 denotes a turbine housing defining a scroll 2, and a scroll inlet portion 2A of the turbine housing 1 is provided with a capacity variable means 3 for varying the passage area. The capacity variable means 3 includes a movable member 4 extending near the scroll inlet portion 2A on the inner circumferential wall of the housing 1, and is connected to the movable portion JA4 by a rod 5, and changes the passage area of the scroll inlet portion 2A by moving the movable member 4. As shown in FIG.
The turbine capacity is changed by moving the movable member 4 in its axial direction. The function generator 8 receives a signal from a potentiometer 10 that determines the position of the accelerator lever 9, and a signal from an F/V converter 12 that converts the engine speed detected by the engine speed detection means 11 into a voltage. are input, and the function generator 8 determines the scroll entrance based on the engine speed Ne and the position of the accelerator lever (that is, the position of the accelerator rack operated as R, R2, R3 by the accelerator lever). A signal is outputted to the actuator 6 via the amplifier 7 so that the opening degree of the passage in the section 2A is as shown in FIG. The opening degree Y of this scroll entrance portion 2A is given by the following equation.

Y = , R + , , Ne + 3 However, k1% is 2, k'l is a constant R is the accelerator rank position, and the opening degree Y of the two scroll entrances has an upper limit for engine protection etc. (that is, the maximum opening degree) OL and a lower limit (that is, the minimum opening degree) CL are provided, and the opening degree Y of the two scroll entrances changes within the range of the upper limit OL and the lower limit CL.

For example, when the engine rotation is stable at point A in Figure 4, if you operate the accelerator lever 9 to set the accelerator rank position to R2 in order to accelerate, the moment you operate the accelerator lever 9, the engine rotation is Since the number Ne is the same, the opening Y of the scroll entrance portion 2A attempts to close to the fully closed point B', but since the opening Y has a lower limit CL,
Move to point B, which is the lower limit CL. After that, engine speed N
As e increases, the opening degree Y of the scroll entrance portion 2A moves from point B to point 0, and further moves along the line of the accelerator rack position R7 and gradually opens. Therefore, compared to a turbocharger with a fixed passage area, more intake air can be obtained during acceleration, and better combustion can be achieved.

However, in such a conventional control device for a variable displacement turbocharger, the opening degree of the scroll inlet section is determined uniquely by the engine speed and the accelerator rack position. Even if the accelerator opening is the same, the intake air flow rate will change due to changes in intake air temperature, atmospheric pressure, fuel octane number (indicating the degree of anti-knock performance), etc., or differences in the characteristics of individual engines, and the boost pressure will change. changes. Therefore, it is not possible to obtain the optimum supercharging pressure corresponding to the operating state of the engine. As a result, there was a problem in that it was not possible to maintain optimal fuel output especially under partial load conditions and output when the accelerator was fully opened. That is, the above-mentioned phenomenon causes deterioration of the fuel quality in the partial load range because the air flow rate that optimizes the combustion state cannot be obtained. Further, even during acceleration, which requires a large amount of air flow in a short period of time, the engine output is reduced, which requires setting the boost pressure at a low level in order to prevent knocking and the like.

(Object of the Invention) Therefore, the present invention aims to prevent knocking by controlling the passage area of the exhaust gas introduction passage to the turbine based on the rotation speed and load, and by narrowing the passage area of the introduction passage to the limit where no non-king occurs in the engine. The aim is to prevent this from occurring while increasing boost pressure in response to engine operating conditions, improving fuel efficiency and acceleration performance in the partial load range.

(Structure of the Invention) As shown in the overall configuration diagram in FIG. 5, the control device for a variable capacity cooler or bot charger of the present invention includes a rotation speed detection means 32 for detecting the engine rotation speed, and a rotation speed detection means 32 for detecting the engine rotation speed. The engine load detecting means 24 detects engine knocking, the knock detecting means 33 detects engine knocking, and the capacity variable means 36 changes the passage area of the exhaust gas introduction passage acting on the turbine wheel 38 to generate supercharging by the compressor wheel 26. A basic control value is set for controlling the variable displacement turbocharger 25 that makes the supercharging pressure of the intake air variable, and the displacement variable means 36 based on the rotation speed and load, and the basic control value is set for the knock detection means 33. By including a control means for controlling the capacity variable means 36 so that the boost pressure is corrected according to the output and becomes optimal for the engine, the engine can be operated while preventing the occurrence of knocking. The boost pressure is increased depending on the situation.

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

6 to 8 are diagrams showing one embodiment of the present invention.

First, to explain the configuration, in FIG. 6, 21 is an engine body, and intake air is introduced into the engine body 21 through an intake pipe 22 and an intake manifold 23. The intake pipe 22 is provided with an air flow meter U, a compressor wheel chamber 26 of the turbocharger section, a throttle valve 27, and a relief valve 28. The flow rate of the intake air is measured by the air flow meter 24, and the measured flow rate Q^ is It is input to the control unit 29. In addition, the intake air is supplied to a compressor wheel 30 housed in the compressor wheel chamber 26.
After being pressurized by the throttle valve 27 and having its flow rate regulated by the throttle valve 27, the air is distributed and supplied to each cylinder of the engine body 21 by the intake manifold 23. The throttle valve 27 is detected by the throttle opening sensor 31 and input to the control unit 29 . Further, the engine rotation speed Ne is detected by a crank angle sensor (rotation speed detection means) 32 and input to the control unit 29 . Furthermore, a knock sensor (knock detection means) 33 is attached to the engine body 21, and the knock sensor 33 detects non-king occurring in the engine body 21, and inputs it to the control unit 29 as a knock signal SFJ. Exhaust gas from the engine is collected at an exhaust manifold 34 and discharged through an exhaust pipe 35, and the exhaust pipe 35 is provided with a capacity variable means 36 and a turbine wheel chamber 37 of the turbocharger 5. A turbine wheel 38 connected to the compressor wheel 30 is housed in the turbine wheel chamber 37.
The flow rate of the exhaust gas acting on the pump 8 can be varied by the variable capacity means 36. That is, the turbine wheel chamber 37 has a scroll 39 formed to surround the turbine wheel 38 (see FIG. 6), as shown in FIG. It gradually becomes smaller as it goes downstream (in the direction of the arrow in the figure). A movable tongue portion 42 is provided at the confluence of the introduction passage 40 to the scroll 39 and the terminal end portion 41 of the scroll 39.
is provided, and the movable tongue portion 42 swings about a shaft 43 in the direction of expanding and contracting the introduction passage 40. This shaft 43 is connected via an arm 45 to a rod 44 shown in FIG. 6, and the rod 44 is connected to a diaphragm 47 of a negative pressure actuator 46. Negative pressure actuator 46
The inside of the case 48 is a negative pressure chamber 4 due to the diaphragm 47.
9 and an atmospheric chamber 50, and a spring 5 inside the negative pressure chamber 49 biases the diaphragm 47 toward the atmospheric chamber 50.
1 has been reduced. Further, the negative pressure chamber 49 is connected to a negative pressure passage 52.
is in communication with the negative pressure tank 53, and the negative pressure tank 53
The negative pressure is supplied by a negative pressure pump 54. The operation of the negative pressure pump 54 is controlled by a negative pressure switch 55 attached to the negative pressure tank 53.
When the negative pressure in the negative pressure tank 53 becomes lower than a predetermined negative pressure, the contact point 5 is turned OFF to maintain the negative pressure in the negative pressure tank 53 at a predetermined negative pressure at all times. The negative pressure passage 52 is opened to the atmosphere via a solenoid valve 56, and the solenoid valve 56 is duty-controlled by the control unit 29. That is, the negative pressure introduced into the negative pressure chamber 49 of the negative pressure actuator 46 is changed by changing the duty ratio of the solenoid valve 56, and as the duty ratio increases, the negative pressure introduced into the negative pressure chamber 49
When the negative pressure weakens, the diaphragm 47 moves into the atmospheric chamber 50. Due to this movement of the diaphragm 47, the rod 44
, the arm 45 and the shaft 43 move, and the movable tongue 42 swings to narrow the introduction passage 40. The movable tongue portion 42, shaft 43, arm 45, rod 44, negative pressure valve 46
, the negative pressure passage 52, the negative pressure tank 53, the negative pressure pump 54, the negative pressure switch 55, and the solenoid valve 56 collectively constitute a capacity variable means 36 that changes the passage area of the exhaust gas introduction passage 40 that acts on the turbine wheel 38. do. Alternatively, a step motor or the like may be used as the capacity variable means.

The control unit 29 is mainly composed of a microcomputer including a microprocessor, a memory, and an interface, and the interface of the control unit 4 includes the air flow meter 24, the throttle opening sensor 31, and the crank angle sensor 32. and signals from the knock sensor 33 are input. Among these signals, analog signals are input as digital signals via an A/D converter. The memory stores programs that control the microprocessor and various data necessary for the operations performed by the microprocessor, and also temporarily stores data imported from outside. The microprocessor calculates the fuel injection amount, injection timing, ignition timing, etc. according to the above program, outputs the injection signal S1 and ignition signal Sp appropriate for the operating condition, and also calculates the duty value of the electromagnetic valve 56 and controls it from the interface. It outputs a signal Sc.

Next, the operation will be explained based on the flowchart shown in FIG. In addition, in the figure, P, to P11. shows each step of the flowchart.

The control calculation of the present invention is executed, for example, once per rotation or once every fixed period of time. When the program starts, first the engine speed Ne and intake flow IQA are input at P.
At P2, the previous duty value Dp is read. Furthermore, P
3, the knock signal S1 is input. Next, P- determines whether or not it is in an acceleration state from the throttle opening (acceleration is determined from the rate of change of throttle opening with respect to time), and if it is not in an acceleration state, P- determines the engine rotation speed Ne and engine load. Intake air flow per unit rotation speed to be displayed 1tQA/N
In relation to e, the duty value is looked up from a table map that has been input into the memory in advance and is set as the basic duty value DH. Then, in P9, it is determined whether or not knocking has occurred in the engine, and if non-knocking has occurred, in P7, a value obtained by decreasing the previous correction value Dp by a predetermined amount DO is set as a new correction value H1, and then P? The duty value obtained by subtracting this new correction value H1 from the basic duty value DM obtained by table lookup in ' is set as the basic duty value DM (DM=Dx-Hi). On the other hand, when knocking has not occurred, the value obtained by increasing the previous correction value Dp by a predetermined amount D'o is set as a new correction value Hi at P, and then the basic duty value Ds obtained by table lookup is set at P8'. , the duty value with this new correction value H1 added is the basic duty value (DM
=Dr-t +Hf). Next, it is determined whether the basic duty value DM, which is corrected depending on whether non-king occurs at P, is between the upper limit value Du and the lower limit value DL. When Du≧DM≧DL, the basic duty value is set as the control duty value Dc at P and stored in the memory, and the solenoid valve 56 is set via the interface at PU.
A signal Sc of the control duty value Dc is outputted to the control duty value Dc. Also,
When DN>DIJ in P9, the upper value Du is set as the basic duty value in PI3, and the basic duty value DM, which is the upper limit value Du of the P lever, is set as the control duty value DC and is stored in the memory. , furthermore, l]
At step 7', the new correction value Hi is stored in the memory as the correction value I)p, and at P1.1, the control duty value (Dc=Du
) is output to the solenoid valve 56 via the interface. Furthermore, when I)M<DL in P, the lower limit value I)L is set as the basic duty value D+ in P and arm, and similarly P.

The basic duty value DM, which is the lower limit value, is set as the control duty value DC and stored in the memory, and a signal S c of the control duty value DC=DL is outputted to the solenoid valve 56 via the interface at Pll. This upper limit Du
The lower limit value is provided to prevent the program from running out of control, to protect the program from the nozzle, and to protect the solenoid valve 56. For example, since the solenoid valve 56 is operated at a constant cycle, at the upper limit side, the frequency is about 51 at a maximum of 20 Hz.
It operates every 2 ms, but if the ON duty exceeds 100% at this time, it will flow into the next cycle, causing malfunction and failure of the solenoid valve 56. Therefore, an upper limit value Du is provided to prevent this problem. Now, as mentioned above, the solenoid valve 56
When the signal Sc is input to the solenoid valve 56, the solenoid valve 56
The duty is controlled by the control duty value DC corresponding to . As a result, the capacity variable means 36 operates to control the passage area of the introduction passage 40 to the supercharging pressure immediately before knocking occurs.

In this way, when not in an acceleration state, the basic duty value DM is calculated based on the engine rotation speed Ne and the intake flow rate QA/Ne per unit rotation, while ensuring safety and protection between the program and the solenoid valve. The basic duty value DM is corrected depending on whether or not knocking occurs, and the supercharging pressure is always controlled to the value immediately before knocking occurs. Therefore, as shown in Fig. 9, even though the rotation speed is the same, it is considered that the intake air flow JiQx changes due to changes in intake air temperature, atmospheric pressure, fuel octane number, etc., or differences in individual engine characteristics. When the ignition timing is controlled to the retarded side (especially in the partial load range), the ignition timing is the same in this embodiment compared to the conventional boost pressure E (dotted chain line in Fig. 9). Tc, the supercharging pressure can be increased to the value just before knocking occurs, as shown by the solid line F in the figure.

As a result, combustion efficiency is increased, and fuel consumption can be significantly improved, especially in a partial load range, and torque can be increased to improve engine output.

On the other hand, in step P-4, when the engine is in an acceleration state, the upper limit value Du is set as the basic duty value DI/l at PI3, and it is determined at P+s whether or not knocking has occurred in the engine. When knocking is not occurring, the upper limit value Du is stored in the memory at P as the control duty value DC through step P;
At u, the flow is outputted to the solenoid valve 56 via the interface, and the flow starts flowing again. However, when knocking occurs, a duty value that is reduced by a predetermined amount DA from the upper limit value [)u in Plb is set as the basic duty value DM, and then P as the control duty value Dc via P9.
, and is stored in the memory at Pll and output to the solenoid valve 56 via the interface. That is, when the engine is in an acceleration state, the duty value is increased to the upper limit value Du, the passage area of the introduction passage 40 is minimized, and the action of the exhaust gas on the turbine wheel 38 is maximized.

As a result, sufficient supercharging pressure can be obtained and output during acceleration can be increased. On the other hand, when the boost pressure is increased, the intake air temperature rises quickly and the output during acceleration increases, but this causes the problem of non-king. However, in the two embodiments, when engine knocking is detected and non-king occurs, the duty value is lowered and the introduction standard 40 is slightly expanded to lower the boost pressure to the limit where non-king occurs. . In this manner, during −1 acceleration, the supercharging pressure can be instantly increased to the limit of knocking, so that acceleration performance can be improved while preventing knocking.

(Effects) According to the present invention, by narrowing the passage area of the exhaust gas introduction passage that acts on the turbine wheel to the limit of knocking depending on the engine operating condition, the occurrence of non-king can be prevented and the engine operating condition can be reduced. The boost pressure can be increased accordingly, and the combustion efficiency can be increased.

As a result, fuel efficiency in the partial load range can be significantly improved, and acceleration performance can also be improved.

[Brief explanation of the drawing]

1 to 4 are diagrams showing a conventional control device for a variable displacement turbocharger. FIG. 1 is a sectional view of the turbocharger, FIG. 2 is a block diagram showing the control circuit of the actuator, and FIG. A characteristic diagram showing the relationship between scroll inlet opening and engine speed, FIG. 4 is an explanatory diagram of its operation, FIG. 5 is an overall configuration diagram of a control device for a variable displacement turbocharger of the present invention, and FIGS. 6 to 8 are 6 is a diagram showing an embodiment of a control device for a variable displacement turbocharger according to the present invention, FIG. 6 is an overall schematic diagram thereof, FIG. 7 is a cross-sectional view of the variable displacement turbocharger, and FIG. 8 is a diagram showing a control unit of the variable displacement turbocharger. Control flowchart 1 and FIG. 9 are characteristic diagrams showing the supercharging pressure in relation to ignition timing and torque. 21----1 engine body, 24---1 air flow meter (engine load detection means), 25---1 turbocharger, 30---1---compressor wheel, 32----
--Crank angle sensor (rotation speed detection means), 33---
---Knock sensor (knock detection means), 36--Capacity variable means, 3B--Turbine wheel, 40--Introduction passage. Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Agagun Part

Claims (1)

[Claims] A rotation speed detection means for detecting the rotation speed of the engine, an engine load detection means for detecting the load condition of the elgin, a knock detection means for detecting backing of the engine, and an exhaust introduction passageway acting on the turbine wheel J. A variable capacity turbocharger that changes the supercharging pressure of the intake air supercharged by a compressor/nosa wheel by changing the area with a variable capacity means, and a basic control value that controls the variable capacity means based on the rotation speed and load. and a control means for controlling the capacity variable means so that the basic control value is set and the basic control value is corrected according to the output of the knock detection means so that the boost pressure becomes optimal for the engine.
．． A control device for a variable displacement turbocharger.