JPH051364B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technology of the Invention] The present invention supplies exhaust gas from an engine to a turbine through a variable exhaust introduction passage to rotate the turbine, and the turbine operates a compressor to supply exhaust gas to the engine. The present invention relates to a control device for a variable displacement turbocharger that variably controls the supercharging pressure of intake air.

[Prior art and its problems] A valve that changes the cross-sectional area of the exhaust gas introduction passage to the turbine is provided at the turbine inlet, and the opening and closing of the valve is controlled according to the engine speed, engine load, etc. to cut off the turbine introduction passage. There are engines that increase torque from low speed ranges to high speed ranges by providing variable capacity turbochargers that vary the area and appropriately control the supercharging pressure of intake air supplied to the engine (for example, Utsukai No. 53-50310). In addition, in such a variable displacement turbocharger, in order to supplement the control by the valve at higher speeds, the exhaust gas supplied from the engine to the turbine is connected between the engine exhaust manifold and the flap valve. A bypass wastegate valve is provided, and in the high-speed range as mentioned above, this wastegate valve is controlled to be opened, and the exhaust gas supplied from the engine to the turbine is appropriately bypassed, so that the rotation of the turbine is optimized. There is a variable displacement turbocharger with a wastegate valve that appropriately controls the supercharging pressure of intake air supplied to the engine to improve engine performance even at high speeds.

In such a variable displacement turbocharger, the opening of the valve or wastegate valve for varying the displacement is set according to the engine speed and engine load to determine the target boost pressure and the actual amount supplied to the engine. Measures the boost pressure of the intake air of the engine, compares the measured boost pressure with the target boost pressure, and corrects the boost pressure of the intake air supplied to the engine based on the difference between the two. Feedback control is performed to deal with variations in component parts and changes over time. However, in variable displacement turbochargers that perform such feedback control, the boost pressure sensor that measures the boost pressure may fail, and in such cases,
It is unclear what value of boost pressure is being supplied, and in some cases, there is a possibility that an abnormally high boost pressure is being supplied. In such a case, the engine may be damaged.

[Object and Summary of the Invention] An object of the present invention is to provide a variable displacement turbocharger that uses a boost pressure sensor to measure the boost pressure supplied to the engine and performs feedback control of the boost pressure. An object of the present invention is to provide a control device for a variable displacement turbocharger that prevents excessive supercharging pressure from being applied to an engine even if a supercharging pressure sensor fails.

In order to achieve the above object, the variable displacement turbocharger control device of the present invention sets the supercharging pressure of intake air supplied to the engine to a predetermined set value based on the engine condition, as shown in FIG. In order to achieve this, the calculation means 101 calculates a control value that controls the cross-sectional area of the introduction passage for exhaust gas supplied from the engine to the turbine, and the calculated control value is combined with the boost pressure measured by the boost pressure sensor 85 to a predetermined value. Based on the difference from the target boost pressure, correction means 103 corrects the control value, and supplies the corrected control value to control means 105 to control the cross-sectional area of the exhaust introduction passage and supply appropriate boost pressure to the engine. At the same time, the identifying means 107 identifies an abnormality in the boost pressure sensor 85, and if the boost pressure sensor 85 is abnormal, the boost pressure reducing means 109 reduces the boost pressure of the intake air supplied to the engine. , the engine is configured so that it will not be damaged by abnormal boost pressure.

[Embodiments of the Invention] Hereinafter, an example of a variable displacement turbocharger to which the present invention is applied will be explained with reference to the drawings. In this example, the control is performed based on the engine load and engine speed as engine conditions, and the accuracy can be improved compared to control based only on the engine load. In FIG. 1, air is supplied to an engine 1 via an intake pipe 3 and an intake manifold 5, and is exhausted via an exhaust manifold 7 and an exhaust pipe 9. An air flow meter 11 for measuring the amount of intake air Q _A is provided at the leftward bent end of the intake pipe 3, and a part of the turbocharger 13 is provided at the bent end of the intake pipe 3. A compressor 15 is provided to compress intake air supplied via the air flow meter 11 and supply it to the engine 1. A throttle valve 17 is provided at the base end of the intake pipe 3 close to the intake manifold 5, and a relief valve 19 is provided in the intake pipe 3 between the throttle valve 17 and the compressor 15. .

A rightward bent portion of the exhaust pipe 9 forms a turbine chamber 37, and a turbine 21 is disposed within this turbine chamber 37, and the turbine 21 is connected to the compressor 15 via a connecting shaft 23. . The turbine chamber 37, as shown in FIG.
1, and the scroll 39 has a cross-sectional area that gradually becomes smaller as it goes downstream in the direction indicated by an arrow 43 from the introduction passage 41. A movable tongue part 25 constituting a flap valve is provided at the confluence of the introduction passage 41 to the scroll 39 and the terminal end 45 of the scroll 39, and the movable tongue part 25 expands and contracts the cross-sectional area of the introduction passage 41. The proximal end portion thereof is rotatably supported by a shaft 27 so as to obtain the desired results.

This movable tongue portion 25 is connected to the exhaust pipe 9 near the upstream side, which is the introduction passage 41 to the turbine 21 in FIG.
It is located inside. A shaft 27 rotatably supporting the movable tongue portion 25 is connected to the upper end of a rod 31 via an arm 29, and the lower end of the rod 31 is connected to a diaphragm 35 constituting an actuator 33 for driving the movable tongue portion. connected. The case 47 housing the diaphragm 35 is divided into an atmospheric chamber 49 and a positive pressure chamber 51 by the diaphragm 35, and the atmospheric chamber 49 has a spring biased to push the diaphragm 35 toward the positive pressure chamber 51. 55 are arranged.

The positive pressure chamber 51 is connected to the intake pipe 3 on the downstream side of the compressor 15 via a connecting pipe 53, and supercharging pressure generated by the compressor 15 is supplied to the positive pressure chamber 51, causing the diaphragm 35 to resist the spring 55. and is pushed toward the atmospheric chamber 49 side. Further, a solenoid valve 57 is provided in the middle of the connecting pipe 53, and this solenoid valve 57
When the valve is driven by the control unit 59 to open, the connecting pipe 5 is opened via the solenoid valve 57.
3 is communicated with the atmosphere, and the pressure inside the positive pressure chamber 51 decreases. More specifically, the solenoid valve 57 is duty-controlled by the control unit 59, and as the duty value increases, the degree of opening of the solenoid valve 57 increases and the pressure in the positive pressure chamber 51 decreases. 49, the diaphragm 35 moves downward, and this movement is transmitted to the movable tongue 25 via the rod 31, the arm 29, and the shaft 27, and the movable tongue 25
The exhaust gas introduction passage 41 to the exhaust gas 1 is rotated in a direction to make it smaller, that is, in a direction to close it. As a result, the flow rate supplied to the turbine 21 increases, and the boost pressure applied to the engine 1 by the compressor 15 increases.
Moreover, the smaller the duty value, the more the solenoid valve 57
As the degree of opening becomes smaller and the pressure in the positive pressure chamber 51 increases, the diaphragm 35 moves upward against the spring 55, causing the movable tongue 25 to rotate in the direction of opening the introduction passage 41. . As a result, the flux supplied to the turbine 21 slows down, and the boost pressure applied to the engine 1 by the compressor 15 decreases.

A waste gate valve 61 is provided at the lower right portion of the exhaust manifold 7. This waste gate valve 61 includes an arm 63, a connecting member 65
is connected to one end of the actuating rod 67 via the actuating rod 6
The other end of 7 is connected to a diaphragm 71 of an actuator 69 for driving a wastegate valve. A case 79 housing this diaphragm 71 is divided into an atmospheric chamber 73 and a positive pressure chamber 75 by the diaphragm 71, and the atmospheric chamber 73 has a spring biased to push the diaphragm 71 toward the positive pressure chamber 75. 81 is provided. The positive pressure chamber 75 is connected to the intake pipe 3 on the downstream side of the compressor 15 via a connecting pipe 77, and the supercharging pressure generated by the compressor 15 is supplied to the positive pressure chamber 75.

Further, a solenoid valve 78 is provided in the middle of the connecting pipe 77, and this solenoid valve 78 is connected to the control unit 5.
When the solenoid valve 78 is driven to open, the connecting pipe 77 is communicated with the atmosphere through the solenoid valve 78, and the pressure in the positive pressure chamber is reduced. More specifically, the solenoid valve 7
8 is duty controlled by the control unit, and as the duty value increases, the degree of opening of the solenoid valve increases and the pressure in the positive pressure chamber decreases, so the diaphragm moves downward due to the action of the spring 81 in the atmospheric chamber. However, this moving action is the rod 6
7. Waste gate valve 6 via arm 63
1, the waste gate valve 61 moves in the direction of closing the bypass passage.

Also, the smaller the duty value, the more the solenoid valve 78
As the degree of opening of the valve becomes smaller and the pressure in the positive pressure chamber increases, the diaphragm moves upward against the spring 81, thereby moving the wastegate valve in the opening direction.

The waste gate valve 61 is used to prevent engine damage when the engine is in a high-speed, high-load state due to the supercharging pressure of the intake air supplied to the engine by the turbocharger becoming too high. A portion of the exhaust gas is discharged to the outside, reducing the amount of exhaust gas supplied to the turbine and ensuring that appropriate boost pressure is introduced into the engine.

The control unit 50 is composed of a microcomputer consisting of a microprocessor, a memory, and an input/output interface including an A/D converter _. and engine 1
The rotation speed Ne of the engine 1 is supplied from a crank angle sensor 83 provided on the left side of the engine 1, and the supercharging pressure _P2 is supplied from a supercharging pressure sensor 85 provided on the engine 1. The control unit 59 appropriately controls the duty value of the signal that drives the solenoid valve 57 based on this information, and varies the cross-sectional area of the exhaust gas introduction passage 41 to the solenoid valve 21 via the movable tongue portion 25. Therefore, the supercharging pressure of the intake air supplied to the engine 1 is determined by the engine speed Ne and the intake air amount Q _A
The torque is increased from low speed range to high speed range by controlling the engine appropriately. In addition, if the boost pressure becomes higher than necessary in the high speed range, the waste gate valve 61 is opened to supply appropriate boost pressure to the engine 1 to prevent damage to the engine 1 even in the high speed range. Enables you to drive safely.

More specifically, the control unit 59
follows the processing program stored in memory,
Intake air volume supplied via interface
The fuel supply pulse width Tp for the electronically controlled fuel injection device is calculated from Q _A and the engine speed Ne based on the following equation (1).

Tp=k·Q _A /Ne...(1) Here, k is a constant. The fuel supply pulse width Tp calculated in this way is a parameter representative of the engine load, and from this fuel supply pulse width Tp and the engine rotational speed Ne, a table as shown in FIG.
The duty value of the signal driving the signal is determined. The table shown in Figure 3 is based on the engine speed Ne
The duty value at which an appropriate boost pressure can be obtained for the fuel supply pulse width Tp is determined in advance through experiments. That is, a duty value is determined from this table based on the engine speed Ne and the fuel supply pulse width Tp, and intake air with an appropriate boost pressure is introduced into the engine 1 by driving the solenoid valves 57 and 78 with this duty value. and engine 1
The torque can be increased from low speed range to high speed range. In this table, the region indicated by A is a region ranging from a low speed region to a medium speed region, and even if the cross-sectional area of the exhaust introduction passage 41 is minimized, the supercharging pressure of the intake air supplied to the engine remains at a predetermined set value. , for example, a region that does not reach +350 mmHg. Therefore, in order to minimize the cross-sectional area of the introduction passage 41 in this region and operate it, the control unit 59 supplies a drive signal with a duty value of 100% to the solenoid valve 57, as shown in the table of FIG. As a result, the solenoid valve 57 is opened and the positive pressure chamber 51 is opened.
pressure is reduced to atmospheric pressure. the result,
The diaphragm 35 is connected to the positive pressure chamber 51 by the spring 55.
Since it is pushed to the side, the rod 31, arm 29,
Via the shaft 27, the movable tongue 25 is actuated in the direction of closing the introduction passage 41, setting the cross-sectional area of the introduction passage 41 to the minimum state. (fully closed state).

The region indicated by C is a high-speed region, and the introduction passage 41
Even if the cross-sectional area of the engine is maximized (fully open state), the supercharging pressure of the intake air supplied to the engine becomes too high than the set value, and there is a risk of engine damage.
Therefore, in this region, the solenoid valve 78 is duty-controlled, the wastegate valve actuator 69 is operated, and the wastegate valve 61 is operated.
is gradually opened to bypass the exhaust gas supplied to the turbine 21, thereby controlling the boost pressure to a constant level.
Further, in this region, in order to maximize the turbine introduction passage 41, the duty value of the solenoid valve 57 is set to 0%.
is set to fully closed. That is, since the solenoid valve 57 is in a fully closed state, the boost pressure downstream of the compressor 15 is directly supplied to the positive pressure chamber 51, and the diaphragm 35 resists the elastic force of the spring 55 to move toward the atmospheric chamber 49 side. Because it is pushed by Rod 3
1. The movable tongue portion 25 operates in the direction of opening the introduction passage 41 via the arm 29 and the shaft 27, and
The cross-sectional area of is set to the maximum state.

The region indicated by B is between the A region and the C region, and corresponds to the position of the movable tongue portion 25, that is, the introduction passage 41.
This is the area where boost pressure can be controlled by the cross-sectional area of
The duty value is determined experimentally so that an appropriate set boost pressure is obtained depending on each operating point.

In addition, in FIG. 3, curves a and b are characteristic curves showing the relationship between the fuel supply pulse width Tp, that is, the torque, and the engine speed Ne when the cross-sectional area of the introduction passage 41 is fixed at the minimum value and the maximum value, respectively. It is. As shown in this characteristic curve, when the cross-sectional area of the introduction passage 41 is fixed at a certain value, Tp decreases as the rotational speed Ne increases, but if the cross-sectional area of the introduction passage 41 is adjusted to the rotational speed Ne, it is ideal. When the rotational speed Ne is changed as shown by curve d, which is the envelope of curves a and b, the torque can be increased over the entire rotational speed Ne.

FIG. 5 is a block diagram showing a first embodiment of a device for performing feedback control according to the present invention.
In the control unit 59, the arithmetic unit 8
7 calculates the fuel supply pulse width Tp corresponding to the intake air amount per rotation representing the engine load from the intake air amount Q _A and the engine rotation speed Ne, and the calculated fuel supply pulse width Tp and rotation speed Ne are The signal is supplied to a duty value calculation device 89. As shown in FIG. 3, the duty value calculation device 89 includes a variable displacement mechanism table 89a and an exhaust bypass mechanism table 89b that store appropriate duty values for the fuel supply pulse width Tp and the engine speed Ne. This table is looked up based on the input fuel supply pulse width Tp and rotational speed Ne, and the corresponding duty value is output. The duty value thus output is corrected via an adder 97 as will be described later, and then supplied to the electromagnetic valve 57. After being supplied to the solenoid valve 57, as shown in FIG. 1, the set value corresponding to the duty value calculated is the supercharging pressure of the intake air supplied to the engine 1 via the actuator 33 and the turbocharger 13. It is controlled so that Further, the supercharging pressure P ₂ of the intake air supplied to the engine 1 is measured by the supercharging pressure sensor 85 and is supplied to the inverting input terminal of the subtracter 93 of the control unit 59. The target supercharging pressure Ps is supplied from the target supercharging pressure setting section 91 to a non-inverting input terminal of the subtractor 93 . The subtracter 93 calculates the boost pressure sensor 8 from this target boost pressure Ps.
The supercharging pressure P ₂ measured in step 5 is subtracted to calculate the deviation ΔP of the supercharging pressure P ₂ from the target supercharging pressure Ps, and this deviation ΔP is supplied to the calculation device 95. The calculation device 95 is
Arithmetic operations such as proportionality, integration, and differentiation are performed on this supercharging pressure deviation ΔP to calculate a duty value deviation, and the calculated result is supplied to an adder 97 and then supplied from a duty value calculation device 89. The calculated duty value is added and corrected.

The abnormality detection means 96 is a device that determines whether the signal from the boost pressure sensor 85 is normal or abnormal.
2b, 94a, and 94b are brought into contact with their lower sides, and the look-up of the table sends a signal to the wastegate driving electromagnetic valve 78, thereby performing control. In addition, when it is determined that there is an abnormality, four changeover switches 92a, 92b, 94 are activated.
By bringing a and 94b into contact with the upper side, a fixed value is input to the subtracter 98 to subtract a fixed value from the table look-up and the look-up value, and the solenoid valve 78 is controlled by the subtracted value.

In FIG. 6, first, the supercharging pressure P ₂ of the intake air supplied to the engine 1 is read from the supercharging pressure sensor 85, and the apparent supercharging pressure P ₂ is converted into a digital value by A/D conversion. Identify whether it is normal (steps 100, 110, 120). Whether or not the boost pressure sensor is abnormal can be determined, for example, based on the read value of the boost pressure _P2 .
That is, as shown in FIG. 7, if the value of supercharging pressure _P2 is outside the normal range and is smaller than -700 mmHg or larger than +700 mmHg, it can be identified as abnormal. In addition, in areas B and C shown in FIG. 3, the boost pressure is set to the target boost pressure Ps (for example,
350mmHg), correction control is performed based on the difference between the two, but in this case, even if the difference between the read supercharging pressure _P2 and the target supercharging pressure Ps is greater than a predetermined value. Can be identified as abnormal.

In this way, as a result of identifying the boost pressure P ₂ ,
If the boost pressure sensor is normal, the engine speed
Calculate the duty value by looking up a table as shown in FIG. 3 from Ne and the fuel supply pulse width Tp, and compare the boost pressure _P2 measured by the boost pressure sensor 85 with the target boost pressure Ps, Feedback control is performed to correct the duty value based on the difference between the two, and this corrected duty value is supplied to the solenoid valve 57 so that normal supercharging pressure is always supplied (step 160,
170, 150).

In addition, if the boost pressure sensor is abnormal, the table is looked up from the engine speed Ne and the fuel supply pulse width Tp, and the solenoid valve 57 is driven in the same way as in normal times, and the waste gate valve 61 is activated in the same way as in normal times. By opening the valve a little more than the normal pressure and forcibly reducing the supercharging pressure, the risk of the supercharging pressure rising too much due to changes over time, variations in parts, etc. is avoided. The forced opening control of the waste gate valve 61 is performed by supplying a subtracted value obtained by subtracting a fixed value from the table pull-up value to the solenoid valve 78 from the control unit 59 as described above (steps 130 and 140).

FIG. 8 is a block diagram showing another embodiment of the present invention, and the difference from the previous embodiment is that the supercharging pressure is reduced by controlling the variable displacement means instead of controlling the waste gate. It is.

Therefore, the same parts are given the same reference numerals to avoid redundant explanation. When the supercharging pressure sensor abnormality detecting means 96 determines that the signal from the sensor 85 is normal, the two interlocking changeover switches 92a' and 92b' are brought into contact with the lower side, thereby changing the table as described above. Control is performed by sending a signal to the solenoid valve 57 for driving the variable displacement means with correction based on the lookup means and supercharging pressure. Also, if it is determined to be abnormal, 2
By bringing the two changeover switches 92a' and 92b' into contact with the upper side, the above-mentioned signal value and constant value are inputted to the subtractor 98', and the solenoid valve 57 is controlled by the subtractor.

FIG. 9 is a flowchart showing the operation of another embodiment of the present invention, and in this flowchart, in the flowchart shown in FIG.
The flowchart is the same as the flowchart shown in FIG. 6, except that a table backup 160 for controlling the variable capacity means is used instead of , and step 240 is provided instead of step 140. That is, in this flowchart, when the boost pressure sensor is identified as abnormal, the table is looked up to find the duty value, and then a constant value is subtracted from the found duty value (step 160,
240), the solenoid valve 57 is driven with this subtracted smaller duty value, and the solenoid valve 57 is controlled to open a little more than usual, and as a result, the supercharging pressure is lowered and the variable displacement turbo charge is controlled. This prevents the engine from being damaged by abnormal boost pressure while taking advantage of the characteristics of the engine.

In this embodiment, the control value for the boost pressure of the intake air supplied to the engine is set using a table based on the engine speed and the fuel supply pulse width as parameters representing the engine state. Since it is approximately proportional to the amount of air, this control value can also be set using a one-dimensional table based only on the amount of intake air.

[Effects of the Invention] As explained above, according to the present invention, when the boost pressure sensor fails, the boost pressure of the intake air supplied to the engine is reduced.
Even if there is a temporary charge, changes over time, variations in parts, etc., the supercharging pressure will not rise abnormally and the engine will not be damaged.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a control device for a variable displacement turbocharger, Figure 2 is an enlarged sectional view of the variable displacement section of the turbocharger used in Figure 1, and Figure 3 is an illustration of engine rotation. Number Ne and fuel supply pulse width
FIG. 4 is a table for calculating a duty value from Tp and a characteristic curve diagram showing the relationship between the fuel supply pulse width and the engine speed when the cross-sectional area of the introduction passage is used as a parameter. FIG. 4 is a diagram corresponding to the claims of the present invention, FIG. 5 is a circuit block diagram of the first embodiment of the present invention, FIG. 6 is a flowchart showing the operation of one embodiment of the present invention, and FIG. 8 is a circuit block diagram of another embodiment of the present invention, and FIG. 9 is a flow chart showing the operation of another embodiment of the present invention. . 1...Engine, 11...Air flow meter, 13
...Turbocharger, 15...Compressor, 2
DESCRIPTION OF SYMBOLS 1...Turbine, 25...Movable tongue part, 33...Movable tongue part drive actuator, 57...Solenoid valve, 59...Control unit, 61...Wastegate valve, 69...Wastegate valve drive actuator, 85...Supercharging pressure sensor , 87... Arithmetic device,
89...Duty value calculation device, 93...Subtractor, 9
5... Arithmetic device, 97... Adder.

Claims (1)

[Claims] 1. A variable displacement turbocharger having a turbine operated by exhaust gas supplied through a variable exhaust introduction passage; a calculation means for calculating a control value for controlling the cross-sectional area of the variable exhaust introduction passage in order to achieve the desired result; a boost pressure sensor for measuring the boost pressure of intake air supplied to the engine; and the measured boost pressure and the target. a correction means that calculates a difference from the supercharging pressure and corrects the calculated control value based on this difference; a control means that controls the cross-sectional area of the variable exhaust introduction passage based on the corrected control value; an identification means for identifying that the pressure sensor is out of order; and when the identification means identifies that the boost pressure sensor is out of order, reducing the supercharging pressure of intake air supplied to the engine. A variable capacity turbocharger control device comprising: boost pressure reducing means;