JPS626256Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a control device for a turbocharger installed in an engine to prevent the pressure of the supercharger supplied to the engine by the turbocharger from becoming excessive.

A turbocharger is installed on an engine to improve the engine's power performance.It uses the energy of the exhaust gas discharged from the engine to drive the exhaust turbine, and an intake compressor that rotates on the same axis as the exhaust turbine. This supplies compressed air (supercharging air) to the engine.

However, if the rotation of the turbocharger becomes excessive and the pressure of supercharging air (supercharging pressure) becomes excessive, problems such as engine knocking and damage may occur. The device is attached.

As a conventional turbocharger control device,
For example, there is one shown in FIG. In the figure, an exhaust turbine 4 of a turbocharger 3 is disposed in an exhaust passage 2 for exhaust gas discharged from an engine 1, and the exhaust turbine 4 is rotationally driven using the energy possessed by the exhaust gas, and is identical to the exhaust turbine 4. An intake compressor 6 disposed within the intake passage 5 rotates on the shaft. On the other hand, air cleaner 7
After the flow rate of the air taken in from the airflow meter 8 is measured, the air is pressurized and compressed by the intake compressor 6 to become supercharged air, and the supercharged air flows through the intake passage 5.
The flow rate is adjusted by the throttle valve 9, and the air is supplied (supercharged) to the engine 1 via the intake manifold 10.

The intake air flow rate signal detected by the air flow meter 8 mentioned above and the throttle valve switch 11
A signal indicating whether the throttle valve 9 is on or off detected by the ignition coil 12 and an engine rotation signal detected from the ignition coil 12 are sent to the control unit 1.
3, the control unit 13 calculates the fuel injection amount that provides the optimum air-fuel ratio according to the operating conditions such as engine speed and load at that time, outputs the control signal, and uses the control signal to control the injector 14. A predetermined amount of fuel is injected into the vicinity of the intake valve 15 in the intake manifold 10, and a mixture of this fuel and the above-mentioned supercharged air is supplied to the engine 1.

The exhaust turbine 4 is provided with a bypass passage 16 that communicates its inlet and outlet sides, and the bypass passage 16 is opened and closed by a swing valve 18 operated by a swing valve controller 17. The swing valve controller 17 has a preset pressure (for example, about 350 mmHg), the supercharging pressure of the intake passage 5 is introduced into its diaphragm chamber, and the differential pressure at which the supercharging pressure exceeds atmospheric pressure is set. The swing valve 18 is opened or closed depending on whether the pressure is above or below. That is, when the differential pressure is below the set value, the swing valve 18 is fully closed and all exhaust gas is absorbed into the exhaust turbine 4. When the differential pressure reaches the set value, the swing valve controller 17 is activated,
Open swing valve 18. Therefore, a portion of the exhaust gas is discharged through the bypass passage 16, so the rotational speed of the exhaust turbine 4 decreases and the boost pressure decreases. In this way, the supercharging pressure is controlled so as not to rise above the pressure (maximum supercharging pressure) obtained by adding the set pressure of the swing valve controller 17 to the atmospheric pressure.

Furthermore, an intake relief valve 19 is installed downstream of the throttle valve 9 in the intake passage 5 in case the supercharging pressure cannot be controlled due to a failure of the swing valve 18 or the control device. This intake relief valve 19 is preset at a set pressure that is slightly higher than the set pressure of the swing valve controller 17 (for example, about 390 mmHg).
The swing valve controller 17 becomes unable to control the swing valve 18 and the supercharging pressure drops to atmospheric pressure.
When the pressure increases beyond the set pressure of , and the boost pressure further exceeds the atmospheric pressure plus the set value of the intake relief valve 19, the intake relief valve 19 opens and releases the boost pressure to the atmosphere. , the supercharging pressure is prevented from exceeding the atmospheric pressure plus the set pressure of the intake relief valve 19.

However, in such a conventional turbocharger control device, the set pressure set in the swing valve controller 17 is always constant regardless of engine speed or cooling water temperature, and usually there is a risk of engine damage. It is set taking into consideration the maximum rotation time when the speed is high. Note that the performance of the turbocharger is such that even at low rotation speeds, it is possible to obtain a supercharging pressure that is higher than the set pressure set in the swing valve controller 17 in consideration of the maximum rotation speed. Therefore, this set value is too low for medium and low speed conditions where there is little risk of engine damage. For this reason, even though it is possible to further increase the set pressure to increase the output particularly under medium rotation conditions, the pressure is limited to the set pressure under maximum rotation conditions.
Further, since it has nothing to do with the cooling water temperature, there is a problem that when the engine overheats, the overheating progresses even further due to supercharging. Furthermore, the maximum boost pressure is regulated by the atmospheric pressure plus a set value, and the set value of the maximum boost pressure differs depending on the atmospheric pressure, so the generated torque and output at high altitudes where atmospheric pressure is low may vary. The problem is that the atmospheric pressure is lower than normal at sea level, which deteriorates power performance at high altitudes.

This idea was created by focusing on these conventional problems, and it sets the maximum boost pressure to an optimal value depending on the engine speed and cooling water temperature, and also sets the actual boost pressure to the optimum value. The purpose of the present invention is to solve the above problem by measuring absolute pressure and controlling the actual supercharging pressure so that it does not exceed a set value.

This invention will be explained below based on the drawings.

FIG. 2 is a diagram showing an embodiment of this invention. As shown in the figure, in this invention, the following components are added or changed from the conventional device shown in FIG. 20 is a distributor from which an engine rotation signal is taken out. A water temperature sensor 21 outputs an engine cooling water temperature signal. 22
is an intake pressure sensor that detects the supercharging pressure of the supercharging air downstream of the throttle valve 9 in the intake passage 5 as an absolute pressure and outputs a signal thereof. 23 is a control unit using a microcomputer, etc., which inputs the engine rotation signal, the cooling water temperature signal, and the absolute pressure signal of the boost pressure, and sets the set value of the maximum boost pressure according to the engine speed and the cooling water temperature. A control signal is output according to the comparison result between the set value and the measured value of boost pressure. 24 is a solenoid valve operated by the control signal, and swing valve controller 17
The solenoid valve 2 is disposed in a passage 25 that communicates the diaphragm chamber (therefore, inside the intake passage 5) with the inlet side of the intake compressor 6 of the turbocharger 3.
4 changes the escape of supercharging air from the intake passage 5 to the inlet side of the intake compressor 6, thereby controlling the pressure in the diaphragm chamber of the swing valve controller 17.

Next, the operation will be described with reference to the flow charts of Fig. 2 and Fig. 3. The engine speed is measured by the distributor 20, the cooling water temperature by the water temperature sensor 21, and the absolute pressure of the supercharging pressure by the intake pressure sensor 22 (step 3 of Fig. 3).
0), each measurement signal is input to a control unit 23. The control unit 23 calculates the engine speed at regular intervals from the engine speed signal.

The memory in the control unit 23 stores the maximum boost pressure set value (mm) according to the engine speed (rpm) and cooling water temperature (°C) as shown in Figure 4.
Hg (absolute pressure) is stored in advance. As is clear from FIG. 4, the setting value of the maximum boost pressure increases as the engine speed decreases, taking into account damage to the engine, and reaches its maximum value when the cooling water temperature is around 80 degrees.

The control unit 23, based on the input coolant temperature and the calculated engine speed,
The table shown in FIG. 4 stored in the memory is looked up and the set value of the maximum boost pressure is calculated (step 31). Next, the set value and the measured supercharging pressure are compared (step 32). If the measured value of the boost pressure is smaller than the set value of the maximum boost pressure, a control signal to open the solenoid valve 24 is output. When the solenoid valve 24 opens (step 33), the supercharging pressure introduced into the diaphragm chamber of the swing valve controller 17 escapes to the inlet side of the intake compressor 6 through the passage 25, the pressure inside the diaphragm chamber decreases, and the pressure inside the swing valve 18 decreases. The opening becomes smaller. Therefore, the bypass amount of exhaust gas decreases, the rotation of the exhaust turbine 4 increases, and the boost pressure also increases.

If the measured value of the boost pressure is greater than the set value of the maximum boost pressure in step 32, the solenoid valve 24 is closed (step 34). This increases the pressure in the diaphragm chamber of the swing valve controller 17,
The swing valve 18 opens, the bypass amount of exhaust gas increases, the rotation of the exhaust turbine 4 decreases, and the boost pressure decreases. In this way, the boost pressure is controlled so as not to rise above the maximum boost pressure set according to the engine speed and cooling water temperature at that time.

The method of determining the maximum boost pressure set value from the engine speed and cooling water temperature may be the table pickup method described above, but it is also a method of formulating the characteristic relationship between the three in advance and calculating it. Good too.

Further, the opening/closing control of the electromagnetic valve may be either fully open or fully closed, or duty control may be used to keep the control frequency constant and change the time span of fully open or fully closed.

As explained above, according to this invention, the optimum maximum boost pressure is set according to the engine rotational speed and cooling water temperature, and the actual boost pressure is prevented from exceeding this set value. This not only prevents engine knocking and damage caused by the boost pressure exceeding the set maximum boost pressure, but also allows the set value to be set high, especially in the low rotation range. , power performance in the low rotation range is improved, and when overheating occurs, the set value is lowered, which prevents overheating from worsening.Furthermore, the actual boost pressure is measured as an absolute pressure, and the set value is also set as an absolute pressure. This eliminates the influence of atmospheric pressure and improves power performance, especially at high altitudes with low atmospheric pressure.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of a conventional turbocharger control device, FIG. 2 is a block diagram of an embodiment of a turbocharger control device according to this invention, and FIG. 3 explains the operation of the device shown in FIG. 2. The flowchart, FIG. 4, is a diagram showing characteristic values of the relationship between the engine speed, the cooling water temperature, and the set value of the maximum boost pressure according to this invention. DESCRIPTION OF SYMBOLS 1... Engine, 2... Exhaust passage, 3... Turbocharger, 4... Exhaust turbine, 5... Intake passage, 10... Intake manifold, 16... Bypass passage, 17... Swing valve controller, 18... Swing valve, 19... Intake relief valve, 20... Distributor, 21... Water temperature sensor, 22... Intake pressure sensor, 23... Control unit, 24... Solenoid valve, 25... Passage.

Claims (1)

[Scope of utility model registration request] The engine rotation speed is detected in a turbocharger that drives an exhaust turbine using the energy of exhaust gas discharged from the engine and supplies the engine with supercharged air that has been pressurized and compressed by an intake compressor rotated by the exhaust turbine. means for detecting the engine cooling water temperature; and means for detecting the supercharging pressure of the supercharging air in absolute pressure;
Means for calculating a set value of maximum boost pressure in absolute pressure according to the engine speed and the cooling water temperature, and outputting a control signal according to a comparison result between the set value and the measured value of the boost pressure. and a valve device that opens and closes in response to the control signal to adjust the amount of exhaust gas that bypasses the exhaust turbine and controls the actual boost pressure so that it does not exceed the set value of the maximum boost pressure. A turbocharger control device characterized by: