JPH0324570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a supercharger for a diesel engine, and particularly to a control device thereof using a microcomputer.

Conventional turbochargers for diesel engines have been unable to operate optimally in all operating ranges. For example, if the scroll area (cross-sectional area of the exhaust gas passage) of the turbine case is made smaller, good matching characteristics will be achieved when the engine is running at low speeds and under light loads, but the scroll area will be small when the engine is at high speeds or under heavy loads. As a result, the engine revs at high speeds and boost pressure rises abnormally, which can destroy the engine. Furthermore, even if the exhaust passage does not reach the point of destruction, the exhaust efficiency is poor due to the narrow exhaust passage, and the exhaust pressure of the engine becomes high, resulting in a large pumping loss and deteriorating the performance of the engine.

On the other hand, increasing the scroll area of the turbine case provides suitable characteristics when the engine is running at high speeds or under heavy loads, but at low speeds or under light loads, the turbine inlet pressure is low, making the turbine rotation unsmooth and necessary. Cannot obtain sufficient boost pressure. As a result, engine performance deteriorates at low engine speeds and under light loads, and when comparing a supercharged engine and a non-supercharged engine in this region, the supercharger acts as a drag on intake and exhaust, resulting in a reduction in fuel consumption. The disadvantage was that the consumption rate was higher for supercharged engines. That is, in any case, if the scroll area is fixed, it is difficult to obtain suitable characteristics over the entire operating range.

In recent years, exhaust turbine superchargers provided with an exhaust bypass path have come into use. This supercharger sets the scroll area of the turbine case small to match the engine speed to the low speed range so that supercharging pressure can be obtained from the low speed range, and excess exhaust gas during high speed operation is bypassed by the exhaust. Excessive pressure rise is prevented by direct exhaust from the pipe. However, this method wastes exhaust energy in high-speed rotation ranges or under heavy loads, lowering engine efficiency and worsening fuel consumption.

In order to compensate for this drawback, if the scroll area is increased to a certain extent to improve the characteristics in the high-speed rotation range, the performance in the low-speed rotation range deteriorates, resulting in the problem that matching cannot be achieved in the entire operating range.

Furthermore, even if the above turbocharger has an exhaust bypass,
Not only is it not possible to obtain the optimal boost pressure when the engine is running at low speeds or under light load, but the supercharger is operated using intake air instead of using the energy of the exhaust gas to send compressed air to the engine. In this case, the supercharger acts as intake and exhaust resistance for the engine, resulting in a disadvantage in that the fuel consumption rate deteriorates.

Note that, for example, Japanese Patent Application Laid-Open No. 56-521 discloses a related technique.

The present invention aims to eliminate the drawbacks of the above-mentioned prior art and provide a control device for a turbocharger for a diesel engine that can obtain optimal operating conditions in all operating ranges, and is characterized by: A turbine impeller is rotated by engine exhaust gas, and a compressor impeller is fixed to the other end of a common rotating shaft with the turbine impeller, and compresses air introduced into the engine when the turbine impeller rotates. A turbocharger for a diesel engine having a bypass control valve provided in a bypass passage that communicates the upstream side of the compressor case with an intake manifold that communicates the compressor case housing the compressor impeller and the engine; It has an exhaust gas control valve installed at the connection between the exhaust manifold and the turbine case housing the turbine impeller.When the engine is operating at low speed and high load, the bypass control valve is closed and the exhaust gas control valve closes the turbine case. Only scroll A on one side is allowed to pass through, and when the engine is operating at high speed and high load, the higher the engine speed is, the lower the load condition is, and the bypass control valve is closed. The bypass control valve is opened to allow exhaust gas to pass through, and during low-load operation, which is lower than a predetermined load, the bypass control valve is opened regardless of the rotation speed to allow intake air to bypass the compressor case. This is because the exhaust gas is configured to bypass the turbine case and be released.

FIG. 1 is a system diagram of a control device for a diesel engine supercharger, which is an embodiment of the present invention. The turbine impeller 1 and compressor impeller 2 are connected by the same shaft, and each turbine case 3,
It is housed in a compressor case 4. Turbine case 3 has scroll A5 and scroll B6.
and a bypass passage 7 are provided, and the exhaust gas passing through these passages is discharged to the outside air via an exhaust muffler 8. In addition, clean air that has passed through the air filter 11 is compressed by the compressor impeller 2 and supplied to the engine 9 via the intake manifold 12, and the exhaust gas combusted by the engine 9 is passed through the exhaust manifold 18 to the inlet of the turbine case 3. be guided by In this way, the exhaust turbine type supercharger 10 is configured.

A bypass control valve 13 is installed in a bypass passage 22 that communicates the downstream of the air filter 11 with the intake manifold 12, and this bypass control valve 13 introduces air pressure supplied from a compressor pump 17 via a solenoid valve 16. The air cylinder 14 is controlled by the air cylinder 14. That is, when air at supercharging pressure is not required during low-speed operation, the bypass control valve 13 is opened and the air is supplied to the intake manifold 12 without passing through the compressor case 4.

On the other hand, exhaust gas from the engine 9 is controlled by an exhaust gas control valve 19 installed at the inlet of the turbine case 3, and this exhaust gas control valve 19 is controlled by a compressor pump regulated by a solenoid valve 21. Air cylinder 2 introducing air pressure from 17
Controlled by 0. Further, the solenoid valve 21 and the solenoid valve 16 are controlled by an output signal from the microcomputer unit 15, and in FIG. 1, exhaust gas is directly discharged to the bypass passage 7, but the exhaust gas control The position of the valve 19 allows the exhaust manifold 18 to communicate with the scroll A5 or even with the scroll A5 and the scroll B6.

FIG. 2 is an explanatory diagram of the operation of the control device shown in FIG. 1, in which the same parts as in FIG. 1 are denoted by the same reference numerals. As mentioned above, the passage inside the turbine case 3 is divided into two parts, and the scroll A5 and the scroll B6 are provided.
The passage area of the scroll B6 is set to be small for low speed rotation ranges and light loads, and the passage area of the scroll B6 is set so that when combined with the scroll A5, a large amount of exhaust gas can pass through during high speed operation ranges and heavy loads. Furthermore, the turbine case 3 is provided with the bypass passage 7 to allow exhaust gas to pass therethrough when the supercharger 10 is not in use. Note that the air cylinder 20 that operates the exhaust gas control valve 19 is operated by compressed air from the compressor pump 17 attached to the engine 9, similarly to the air cylinder 14 on the compressor side.

The microcomputer unit 15 inputs the rotational speed signal of the engine 9 and the accelerator opening of the fuel injection pump.
It is output to solenoid valves 16 and 21. The accelerator opening signal is obtained by connecting a potentiometer directly to the accelerator lever, extracting it as a divided voltage Es of the low voltage Eb of the accelerator opening detector 33, and converting it into direct current using the A/D converter 26. Since it is known that the accelerator opening degree of the fuel injection pump is proportional to the torque of the engine 9, the above-mentioned divided voltage Es shows a value proportional to the torque and the load.

Also, the rotation speed of the engine 9 is determined by its ring gear 2.
The number of teeth per period of 3 is detected by an electromagnetic pickup 24, shaped by a pulse shaper 25, and inputted to the microcomputer unit 15. Microcomputer unit 1
5 is a 1-chip microcontroller, and on the chip is a 2K byte read-only memory ROM27,128.
It uses Motorola's MC6801 model, which is equipped with 28 bytes of random access memory RAM, serial communication interface and parallel input/output unit I/O 29, microprocessor unit MPU 30, and other functions such as a 16-bit counter, oscillator circuit, and interrupt function. ing.

This microcomputer unit 15 is the accelerator opening Es
and engine rotational speed N are input, calculations and judgments are made, and the solenoid valves 16 and 21 are controlled to adjust the intake air and exhaust air so that the state is optimal at that time. The output from the microcomputer unit 15 is supplied to a drive circuit 31 and converted into an analog quantity by a pair of D/A converters. These analog quantities are output to the respective electro-pneumatic converters 32a, 32b, and are sent to the air cylinders 14, 20 via the compressed air solenoid valves 16, 21.
supply compressed air. Therefore, the bypass control valve 13 and the exhaust gas control valve 19 are switched.

Figure 3 is a diagram comparing the characteristics of a diesel engine with a supercharger and a diesel engine without a supercharger, where the horizontal axis shows the engine speed N and the vertical axis shows the torque T. It shows. When a supercharger is not installed, the torque shows a maximum value at a relatively low engine speed N, and decreases in a gentle curve when the engine speed I becomes higher than that.

However, in the case of a supercharged engine, the maximum torque T occurs at a higher rotational speed N than in the case of a non-supercharged engine.
There are places where it is shown. Therefore, if high torque is required, operation should be performed in the shaded I range, and if low speed ranges and torque are not required, the range should be used to obtain suitable drivability in all driving ranges. can. The poor performance of the supercharged engine in the above range is due to the fact that the scroll area of the turbine case is constant. Therefore, attempts have been made in the past to change the scroll area depending on the operating conditions to perform supercharging over the entire area.

FIG. 4 is a sectional view of various turbine cases with variable scroll areas. Figure 4A shows a system in which part of the scroll partition is movable and one passage is sealed during low-speed movement to reduce the through-roll area.
Figure B shows a switch valve installed in one passage that can be opened and closed by rotating it, Figure 4 C shows a type in which movable blades are installed on the air passage wall to make the scroll area variable, and Figure 4 D shows a type in which the scroll area is variable. A flexible plate installed close to the inner surface of the scroll is pulled in the direction of the arrow at low speeds to the position shown by the broken line, thereby reducing the scroll area.

This will improve performance compared to a supercharger with a fixed scroll area, but the supercharger will act as resistance to intake and exhaust at light loads, so the load will be lower than an engine without a supercharger. performance is poor.

However, in the case of this embodiment shown in FIG. 1, the bypass passages 7 and 22 on the turbine side and the compressor side are in an open state, and when the engine 9 is started and the load is light, the bypass state is the same as when the engine is stopped. Therefore, the supercharger does not act as resistance. That is, it can be operated under the same conditions as an engine without a supercharger. Also, when the engine speed increases to a certain extent and the load becomes large, that is, when the counting frequency of the electromagnetic pickup 24 that detects the rotation speed increases and the output voltage Es of the accelerator opening detector 33 increases. ,
The microcomputer unit 15 comes to control the supercharger 10 according to the following program.

FIG. 5 shows a supercharger control program. First, the engine speed N and accelerator opening Es are measured, and the
Import it into RAM28 as data. Next, a comparison calculation is made with the (Ni, SJ) map shown in FIG. 7, which is preset in the ROM 27 in the microcomputer unit 15.
Determine which area on the map the current operating state is in. Subsequently, the position of each control valve 13, 19 is calculated and the result is output to the drive circuit 31, and the signals of the movement amount of the control valves 13, 19 are converted from D/A to electro-pneumatic converters 32a, 32b. can be conveyed to. At the same time, a signal is sent to the air cutoff valve (solenoid valve 16, 21) for driving the control valve.
Open 6,21. The amount of movement thus converted into air pressure is transmitted to the air cylinders 14, 20 of the control valves 13, 19, respectively.

For example, in the area shown in Figure 3, the exhaust gas control valve 1
9 opens only the scroll A5 with a small passage area, the bypass control valve 13 on the compressor side is closed, and the supercharger 10 is in a state suitable for a low speed rotation range. Similarly, if the rotational speed N of the engine 9 and the opening degree of the bypass control valve 13 are within the range, the exhaust gas control valve 19 simultaneously opens scroll A5 and scroll B6, which have a large exhaust gas passage area, and The bypass control valve 13 is closed to be in a state suitable for high-speed operation. Furthermore, when the engine 9 is started or under a light load, the microcomputer unit 15 determines that the engine is in the range state as described above, and in this case, the bypass control valve 13 is opened and the exhaust gas control valve 19 is in the state shown in FIG. The exhaust gas is then completely released from the bypass passage 7.

Each of the above regions is determined by actually measuring the engine speed and load torque characteristics, and taking into consideration the drivability and fuel consumption rate of the engine 9. FIG. 6 is a diagram showing the control range of the supercharger more clearly, in which the horizontal axis shows the rotational speed N of the engine 9 in rpm, and the vertical axis shows the load torque in Kg·m. In this range, the engine speed is low and the load is high, and at this time, the supercharger 10 is activated and the scroll A5 is opened.
This range corresponds to the case of high rotation and high load, and at this time, the scroll A5 and the scroll B6 are opened and the supercharger 10 is in full operation. Also,
In this region, the bypass control valve 14 is opened and the exhaust gas is discharged through the bypass passage 7 in the state shown in FIG. In this way, the state becomes irrelevant to the supercharger 10, and energy loss due to the supercharger 10 can be minimized.

Fig. 7 is an enlarged view of the part where the three areas in Fig. 6 approach, and Fig. 8 is an enlarged view of part A in Fig. 7. ) is divided into equal parts and created into a map. In this embodiment, the rotation speed N of the engine 9 is divided into 125 equal parts between 500 and 2500 rpm in units of 16 rpm. In addition, the load torque is 1.375 by dividing the accelerator opening corresponding to 20 to 108 kg・m into 64 equal parts.
Classified by kg/m. As mentioned above, the load torque % and the accelerator opening % are proportional, so
In this case, it is indicated by the accelerator opening, and the position of 100% of the accelerator opening indicates the maximum torque at each rotation speed at full load.

The black areas shown in FIG. 8 are the boundary positions of each area, so these are
In addition, the shaded areas are areas where hysteresis is provided for each boundary, and this is also stored in the ROM 27. By providing such a hysteresis section, the hunting phenomenon that occurs when switching between each region is suppressed.

If you do the above, the inside of the microcomputer unit 15 will be
It becomes possible to appropriately control the bypass control valve 14 and the exhaust gas control valve 19 by comparing the engine speed and the accelerator opening with the control map stored in the ROM 27, and the engine horsepower, torque, Characteristics such as exhaust gas and fuel consumption rate
Can be improved by ~10%.

The control device of this embodiment is provided with a bypass control valve in a bypass passage that communicates between a flow path between an air filter and a compressor of a supercharger and an intake manifold, and also has crawler A and scroll B at the inlet of a turbine case. and means for selecting the entrance to the exhaust bypass passage; in high load and low speed ranges, the bypass control valve is closed and only scroll A is opened; in high load and high speed ranges, the bypass control valve is closed and scrolls A and B are opened. In all low-load operating ranges, the bypass control valve is opened and operated in such a way that all exhaust gas from the engine is released by bypass. In addition, the above three areas of the grab indicating the relationship between engine speed and load torque or accelerator opening over the entire operating range should be stored in the ROM of the microcomputer unit, and the values should be compared and judged during actual operation. This has the effect of improving engine drivability and fuel consumption by 5 to 10%.

In the above embodiment, in the low load range where the supercharger 10 does not operate, the engine speed and accelerator opening are controlled as described above, and when the load range is entered, the compressor pressure ratio πc (compressor pressure ratio πc) of the supercharger 10 is controlled. The supercharger 10 can be controlled more accurately by controlling the ratio of the outlet pressure P _C2 to the inlet pressure P _C1 (P _C2 /P _C1 ) and the rotation speed N of the supercharger 10. . Furthermore, since the above-mentioned πc is input, the altitude correction of the supercharger 10 can be automatically performed. Furthermore, in addition to the above, the map to be written to the microcomputer's ROM is
In the range, the engine rotational speed and the compressor pressure ratio πc, or the control valve opening degree and the rotational speed of the supercharging number 10 may be used. Furthermore, similar control can be achieved by using the amount of movement of the plunger of the fuel injection pump instead of the control valve opening.

Further, in the above embodiment, the operation of the exhaust gas control valve 19 on the turbine side is performed in three digital stages, but it is also possible to control this by continuously moving the control valve in an analog manner.
As another method, control may be performed using a combination of analog and digital movement amounts, or the control valve on the compressor side may similarly be a continuously variable valve. Performing this continuously variable control has the advantage that the supercharger moves smoothly when switching between each region.

In the above embodiment, the bypass control valve 14 and the exhaust gas control valve 19 are pneumatically driven air cylinder type control valves, but other hydraulic servo valves, servo valves with a pulse motor, servo valves with a DC motor, turbo valves with a diaphragm can also be used. It is also possible to configure a control system using the following. In addition, although the scroll A and scroll B of the turbine case 4 are switched in two stages: scroll A only and scroll A+scroll B, the map may be formed in three stages: A, B, and A+B. Further, this scrolling may be controlled by a microcomputer as a variable type shown in FIG.

The diesel engine supercharger control device of the present invention improves drivability and fuel efficiency in the low speed range by providing a system without a supercharger during low speed ranges or light loads. Furthermore, since the turbine case is of a variable scroll type, optimum boost pressure can be obtained over a wide operating range of the engine. Therefore, the features of the supercharged engine can be fully demonstrated during medium-load or heavy-load operation of the engine, and the supercharging pressure can be increased by 10 to 20% compared to conventional engines, resulting in high performance. As a result of the above, compared to conventional supercharged engines, the horsepower and torque can be improved by 5 to 15%, and the fuel consumption rate can be reduced by 5 to 8%.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a control device for a diesel engine supercharger which is an embodiment of the present invention, and FIG.
Fig. 3 is a graph comparing the characteristics of a diesel engine with a supercharger and one without a supercharger, and Fig. 4 is a graph showing the characteristics of a diesel engine with a turbocharger and one without a supercharger. 5 is a supercharger control program, FIG. 6 is a line diagram showing the control area of the supercharger, FIG. 7 is an enlarged view of the area where the three areas in FIG. 6 approach each other, and FIG. It is an enlarged view of part A in FIG. 7. 1... Turbine impeller, 2... Compressor impeller, 3... Turbine case, 4... Compressor case, 5... Scroll A, 6... Scroll B, 7, 22... Bypass passage, 8... Exhaust Muffler, 9...Engine, 10...Supercharger, 11...
Air filter, 12...Intake manifold,
13... Bypass control valve, 14, 20... Air cylinder, 15... Microcomputer unit, 16, 21
... Solenoid valve, 17 ... Compressor pump, 18
...Exhaust manifold, 19...Exhaust gas control valve,
23...Ring gear, 24...Electromagnetic pickup, 25...Pulse shaper, 26...A/D converter, 27...ROM, 28...RAM, 29...
I/O, 30...MPU, 31...Drive circuit, 3
2... Electro-pneumatic converter, 33... Accelerator opening detector.

Claims (1)

[Scope of Claims] 1. A turbine impeller rotated by engine exhaust gas; and a turbine impeller fixed to the other end of a common rotating shaft with the turbine impeller, and when the turbine impeller rotates, the turbine impeller rotates by the engine exhaust gas. In a diesel engine supercharger having a compressor impeller that compresses introduced air, the upstream side of the compressor case is communicated with an intake manifold that communicates the compressor case housing the compressor impeller with the engine. a bypass control valve provided in a bypass passage; and an exhaust gas control valve provided at a connection between an exhaust manifold of the engine and a turbine case housing the turbine impeller; The bypass control valve is closed and the exhaust gas control valve is used to close the scroll A on one side of the turbine case.
During high-speed, high-load operation of the engine, the bypass control valve is closed at lower load conditions as the engine speed increases, and the exhaust gas control valve closes the scrolls A and B on both sides of the turbine case. is opened to allow the exhaust gas to pass through, and during low-load operation lower than a predetermined load, the bypass control valve is opened regardless of the rotation speed to allow the intake air to bypass the compressor case. 1. A supercharger control device for a diesel engine, characterized in that the exhaust gas is configured to be discharged bypassing the turbine case by switching an exhaust gas control valve. 2 The bypass control valve and the exhaust gas control valve are introduced by respective electromagnetic valves that are opened by the output of the microcomputer unit calculated by inputting the engine rotation speed and the signal from the accelerator opening detector. A turbocharger control device for a diesel engine according to claim 1, which is a valve operated by air pressure.