JPS6047455B2 - Engine with turbocharger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a turbocharged engine.

Conventional turbocharged engines typically perform supercharging by bypassing the exhaust turbine and discharging excess exhaust gas directly into the exhaust passage when the boost pressure generated by the turbocharger compressor exceeds a set limit. Equipped with a wastegate valve to prevent pressure build-up.

However, in such a turbocharged engine, if the wastegate valve fails, there is a risk that the engine will be damaged.

An object of the present invention is to provide an engine with a turbo charger that guarantees the safety of the engine in the event of a wastegate valve failure and enables normal running without sacrificing the supercharging effect. be.

According to the present invention, a turbocharger includes an exhaust turbine disposed in an exhaust gas passage and driven by exhaust gas, and a compressor disposed in an intake passage and driven by the exhaust turbine to pressurize intake air; A wastegate valve is disposed in a bypass passage that bypasses the exhaust turbine and controls the opening and closing of the bypass passage; and a wastegate valve is disposed in the intake passage downstream of the compressor and provides predetermined supercharging when the wastegate valve fails. a relief valve that operates in response to pressure and discharges intake air to the atmosphere or the inlet side of the compressor, and the relief valve is controlled in response to the pressure of the scroll portion of the compressor to reduce the engine speed in the medium speed range of the engine. The present invention provides a turbocharged engine characterized in that the supercharging pressure at high speeds is higher than the supercharging pressure at high speeds.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, a turbocharger 1 includes an exhaust turbine 4 disposed in an exhaust gas passage 3 of an engine 2 and driven by exhaust gas, and an exhaust turbine 4 disposed in an intake passage 5 of the engine 2. The compressor 6 is driven by the compressor 6 to pressurize the intake air.

A fuel injector 7 and a throttle valve 8 are provided downstream of the compressor 6 in the intake passage 5 . The fuel injector 7 has its fuel injection operation controlled by a computer 9. Bypass passage 1 that bypasses the exhaust turbine 4
A waste gate valve 11 is disposed at 0.

The opening and closing operations of the wastegate valve 11 are controlled by a wastegate actuator 12. The wastegate actuator 12 has a diaphragm 14 defining a pressure chamber 13 to which the wastegate valve 11 is secured via a link 15 and biased to close the bypass passage 10, typically by a spring 16. .
The pressure chamber 13 communicates with a scroll portion of the compressor 6 via a passage 17. A relief valve 18 is disposed in the intake passage 5 between the compressor 6 and the fuel injector 7, and supplies intake air to the compressor in the intake passage 5 via a passage 19. 6 can be released upstream.

Instead of discharging the intake air to the inlet side of the compressor 6, it may be discharged to the atmosphere. The relief valve 18 includes a valve member 20 disposed in the intake passage 5, a diaphragm 22 that is connected to the valve member 20 and forms a pressure chamber 21, and acts on the diaphragm 22 to bias the valve member 20 in the valve closing direction. It has a spring 23. The pressure chamber 21 communicates with the scroll portion of the compressor 6 via a passage 24. aisle 2
An orifice 25 is provided within the relief valve 4 to prevent hunting of the relief valve 18. An alarm mechanism that operates in conjunction with the relief valve 18 to notify the driver of the operation of the relief valve is a reed switch 26 disposed within the pressure chamber 21.
and a magnet 27 that is fixed to the diaphragm 22 and moves together with the diaphragm, and the reed switch 26 is connected to a warning light 28 and a power source 29 mounted in the vehicle interior, for example.

It is also connected to a computer 9 for the fuel injector 7. The operation of the above-mentioned turbocharged engine will be explained.

When the engine 2 is in operation, the exhaust gas in the exhaust gas passage 3 drives an exhaust turbine 4, which drives a compressor 6 to pressurize intake air.

The pressurized intake air in the intake passage 5 is mixed with fuel from the fuel injector 7 and then supplied to the combustion chamber of the engine 2 via the throttle valve 8. As the rotational speed of the engine 2 increases, the exhaust gas pressure increases and the rotational speed of the exhaust turbine 4 increases, so that the supercharging pressure generated by the compressor 6 also increases accordingly.

If the boost pressure exceeds the limit set value, the pressure in the scroll section of the compressor 6 is in communication with the pressure chamber 13 of the wastegate actuator 12 via the passage 17, so that the diaphragm 14 is moved against the spring 16 1 to the left in Figure 1, the wastegate valve 11 is opened via the link 15, and the bypass passage 10 is opened. As a result, excess exhaust gas is discharged into the exhaust gas passage 3 via the bypass passage 10, and the supercharging pressure is prevented from increasing beyond the set limit value. If the wastegate valve 11 fails, the relief valve 18 can perform a fail-safe function.

When the wastegate valve 11 fails, the pressure in the scroll portion of the compressor 6 communicates with the pressure chamber 21 of the relief valve 18 via the passage 24, and therefore acts on the diaphragm 22 to generate a force in the valve opening direction. When the relief valve 18 is in the closed position, the supercharging pressure in the intake passage 5 acts on one side of the valve member 20 and presses the valve member in the valve closing direction. When the pressure becomes sufficient to overcome the combined force of the boost pressure and the force of the spring 23 acting on the valve member 20, the diaphragm 22 moves to the right in FIG. 1 and the valve member 20 moves into the intake passage 5. It is moved in the valve opening direction to connect the intake passage 5 and the passage 19. As a result, part of the supercharging pressure begins to be released to the inlet side of the compressor 6, but once the relief valve 18 is opened, the valve member 20
Since both sides of the valve member 20 are exposed to the supercharging pressure in the intake passage 5, the valve member 20 is moved in the valve opening direction until the pressure of the scroll portion and the force of the spring 23 are balanced, thereby opening the intake air. The communication area between the passage 5 and the passage 19 increases, and the supercharging pressure decreases. When the pressure of the scroll portion of the compressor 6 acting on the diaphragm 22 becomes insufficient to overcome the force of the spring 23, the spring 23 again moves the diaphragm 22 to the left in FIG. The member 20 is moved in the valve closing direction to cut off communication between the intake passage 5 and the passage 19, allowing the boost pressure to rise. As mentioned above, the relief valve 18 according to the invention is controlled by the pressure in the scroll section of the compressor 6.

Generally, the pressure at each location in the intake system depends on the shape of the passage,
Depending on the resistance etc., the outlet PEPb of the compressor 6
Assuming that P is constant, the pressure Pa of the scroll portion and the manifold pressure Pc downstream of the throttle valve 8 have characteristics as shown in FIG. The reason why the pressure Pa has the characteristics shown in FIG. 2 is thought to be because it is influenced by the suction pressure. Here, the spring 23 is selected to obtain the target supercharging pressure (that is, the manifold Fc, which is the pressure after subtracting the pressure drop due to passage resistance etc. with respect to the outlet liver b) at the engine speed N1, which is a high speed range. If we set the biasing force F,
F=PalA-PblB (A: area of tire flam 22, B: area of valve member 20), and since A and B are constants, F is determined by Pa and Pb, and its value is constant due to the structure. becomes.

By the way, P at engine speed N2 which is a medium speed range
If the points on the a, Pb line are Pa3, pb3, at P■, which is the same compressor outlet pressure as in the high-speed range, the pressure difference with the scroll pressure Pa3 is small as is clear from Fig. 2, so F>Pa3A. -P? It becomes B. For this reason,
In order to cause the relief valve 18 to open, the pressure Pa
It is necessary to raise the pressure to a higher pressure than Pa3. Therefore, when the engine speed is N2 and the engine load etc. is increased to raise the pressure Pa to a higher pressure than Pa3, the output pressure Pb also gradually increases from P1)3 and the pressure Pa becomes Pa2. When F:Pa2A-PY)2B, the relief valve 18 is opened. Therefore, the outlet pressure Pb of the compressor 6 at that time has increased to P2, which is greater than Pbl, and the supercharging pressure λ(Pi) has accordingly increased more than the supercharging pressure Pc(Pi) in the high speed range. In addition, the broken line shown in FIG. 2 is a constant pressure line passing through Pb2 for the outlet pressure Pb, and a line showing the change in the pressure Pa of the scroll portion in the case of the same constant pressure line. As a result, by using the pressure of the scroll portion, which has characteristics that vary greatly depending on the engine speed (i.e., intake air amount) as shown in FIG. 2, as the control pressure for the relief valve 18, the relief valve 18 The boost pressure in the medium speed range is controlled to be higher than the boost pressure in the high speed range. Therefore, the supercharging effect can be maintained high in the medium speed range. Furthermore, when the relief valve 18 is opened, the pressure of the scroll acting on the diaphragm 22 must overcome the combined force of the supercharging pressure acting on the valve member 20 and the force of the spring 23, as shown in FIG. As shown,
The relief valve opening pressure Pj is set higher than the operating pressure Pw of the wastegate actuator. Thereby, the relief valve 18 functions as a fail-safe in the event of a failure of the wastegate valve 11, and prevents the relief valve from operating unnecessarily during normal operation of the wastegate valve. On the other hand, when the relief valve 18 is closed after opening, only the force of the spring 23 acts on the diaphragm 22, so the relief valve closing PEPr is lower than the valve opening pressure Pl as shown in FIG. will also be lower. As a result, the supercharging pressure is not maintained near the set limit value, but drops considerably after the relief valve is opened, so that the stability of the engine can be ensured.
Note that PI in FIG. 3 indicates the knock occurrence or exhaust gas temperature upper limit range. Furthermore, by appropriately selecting the effective area of the diaphragm 22 and the valve member 20 and the spring constant 7 of the spring 23, the relief valve opening pressure and the relief valve closing pressure after opening can be freely set. is possible. When the diaphragm 22 moves to the right in FIG. 1 when the relief valve 18 is opened, the magnet 27 fixed to the diaphragm also moves accordingly, and the reed switch 26 is closed and installed in the passenger compartment. Warning light 28 is turned on.

Therefore, by operating the alarm mechanism in conjunction with the relief valve 18, it is possible to notify the driver of a malfunction of the wastegate valve. Further, by integrating the alarm mechanism with the relief valve and operating them simultaneously, it becomes possible to maintain the supercharging pressure at a high level. In other words, when the relief valve and alarm mechanism are separated and controlled by separate systems, the accuracy of the relief valve and alarm mechanism varies, and the warning light may operate at the same time or before the relief valve operates. Therefore, it is necessary to set the range of variation in the operation of the alarm mechanism to the low boost pressure side so as not to overlap the range of variation in the operation of the relief valve. However, in order to prevent the alarm mechanism from operating during normal operation of the turbocharger, that is, when the boost pressure is below the set limit value, it is necessary to lower the set limit value. Therefore, there arises a drawback that the supercharging effect of the turbocharger is diminished. Further, when the reed switch 26 is closed, a close signal of the reed switch is transmitted to the input side of the computer 9, and the computer adjusts the fuel injection operation of the fuel injector 7 according to this signal. Therefore, it is possible to prevent the air-fuel ratio from decreasing, that is, from enriching the air-fuel mixture.

As described above, the turbocharged engine according to the present invention has an effective emergency system that guarantees the safety of the engine in the event of wastegate valve failure and enables normal running without sacrificing the supercharging effect. This is what we have in place.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a turbocharged engine according to the present invention, Fig. 2 is a chart showing the relationship between engine speed and pressure at various locations in the intake system, and Fig. 3 is a diagram showing the relationship between engine speed and relief valve. and a chart showing the relationship between supercharging pressure during operation of the wastegate actuator. 1...Turbocharger, 2...Engine, 3...Exhaust gas passage, 4...Exhaust turbine, 5...Intake passage, 6...・Compressor, 7... Fuel injector, 8... Throttle valve, 10... Bypass passage, 11...
...wastegate valve, 12 ...wastegate actuator, 18 ...relief valve,
19... Passage, 20... Valve member, 21
...pressure chamber, 22...diaphragm,
23... Spring, 26... Reed switch, 27... Magnet, 28... Warning light.

Claims (1)

[Scope of Claims] 1. A turbocharger having an exhaust turbine disposed in an exhaust gas passage and driven by exhaust gas, and a compressor disposed in an intake passage and driven by the exhaust turbine to pressurize intake air. , a wastegate valve disposed in a bypass passage that bypasses the exhaust turbine and controls the opening/closing of the bypass passage; and a wastegate valve disposed in the intake passage downstream of the compressor that controls a predetermined overflow when the wastegate valve fails. a relief valve that operates in response to supply pressure and discharges intake air to the atmosphere or the inlet side of the compressor, and the relief valve is controlled in response to the pressure of the scroll portion of the compressor to reduce the engine speed at medium speed. A turbocharged engine that is characterized by having a higher boost pressure at low speeds than at high speeds. 2. The relief valve includes a valve member disposed in the intake passage, a diaphragm connected to the valve member and configured to move the valve member in a valve opening direction in response to the pressure of the scroll portion of the compressor, and a diaphragm connected to the valve member, and an elastic device that acts to bias the valve member in the valve closing direction, the valve opening pressure of the relief valve is higher than the operating pressure of the wastegate valve, and the valve closing pressure of the relief valve after opening is 2. The turbocharged engine according to claim 1, wherein the valve opening pressure is set lower than the valve opening pressure. 3. The turbocharged engine according to claim 1, further comprising an alarm mechanism that operates in conjunction with the relief valve to notify the driver of the operation of the relief valve.