JPH01142214A - Turbo supercharged engine - Google Patents

Abstract

PURPOSE:To enhance a low speed torque, by connecting high and low pressure turbo chargers to each other in series, and arrauging an overflow valve and a check valve respectively in a high pressure exhaust bypass for communicating high/low exhaust pipes with each other and in an intake air bypass for communicating low/high pressure air supply tubes with each other. CONSTITUTION:A high pressure turbo charger 1 consisting of a turbine 2 with a small allowable exhaust gas flow quantity and a compressor with a small ejection quantity and the low pressure turbo charger 9 consisting of the turbine 10 with a large allowable exhaust gas flow quantity and a compressor 12 with a large ejection flow quantity, are provided respectively so as to install them in the exhaust system of an engine (E) by connecting them to each other in series. And high/low pressure exhaust pipes 5, 13 and low pressure exhaust pipe 13/turbine outlet 10 are respectively connected communicably to each other through respective exhaust bypasses 15, 18, and overflow valves 17, 20 to be controlled by an engine operation state are installed on the way of those exhaust bypasses respectively. In addition, high/low pressure air supply tubes 7, 14 are communicablly connected to each other through an air supply bypass 21 and a check valve 22 for allowing air flow only from the air supply tube 14 to the air supply tube 7 is are installed on the way of the supply bypass.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention provides a turbocharged engine, especially a plurality of turbochargers arranged in series, each consisting of a high-pressure turbocharger and a low-pressure turbocharger. Adjusting the supply pressure generated by the turbocharger according to supply pressure, exhaust pressure, load, knocking, etc., and sequentially selecting the number of operating turbochargers to improve responsiveness.
The present invention relates to a turbocharged engine that can improve low-speed torque and avoid knocking.

<Prior Art> Well-known turbocharged engines are usually equipped with a single turbocharger designed to produce maximum torque at the engine speed required for the engine. Due to the characteristics of a speed type compressor, the air supply pressure ratio generated is low at low speeds, as shown by the dotted line in Figure 5, and therefore the torque generated by the engine is also low, as shown by the solid line in the figure, which is desirable for a vehicle engine. It is not possible to increase low-speed torque. Furthermore, when the engine is at idle speed, the energy of the exhaust gas is insufficient and the rotational speed of the turbocharger is low, so that the rotational speed of the turbocharger cannot follow the rapid acceleration of the engine, resulting in so-called turbo lag.

Therefore, in order to create the torque curve shown in the dashed line in Fig. 5, which increases low-speed torque and reduces turbo lag at the same time, the main turbocharger generates the necessary torque at low speeds, and the secondary turbocharger generates torque to compensate for this at high speeds. A so-called sequential turbocharged engine has been devised that is equipped with a plurality of turbochargers and selectively operates one or more depending on the engine rotational speed, thereby increasing charge air pressure at low speeds and increasing low-speed torque. There is something.

<Problems to be Solved by the Invention> However, even with the above method, if the number of turbochargers activated when the vehicle accelerates is increased.

Since the exhaust switching valve is suddenly opened and the auxiliary turbocharger, which had been stopped until then, is activated, the turbine output of the main turbocharger decreases due to a sudden increase in the turbine nozzle area, and the acceleration delay of the auxiliary turbocharger temporarily reduces the As a result, the supply pressure decreases, and the torque temporarily decreases as shown by the solid line in Figure 6, and the engine output control requested by the vehicle as shown by the dotted chain line in Figure 6 decreases. The current situation is that this is temporarily impossible.

In view of the above, the present invention aims to prevent a temporary torque drop and improve engine response when changing the number of turbochargers operating during acceleration in a sequentially turbocharged engine equipped with a plurality of turbochargers. It was devised as.

Means for Solving Problems> In order to achieve the above object, the present invention connects a high-pressure and low-pressure turbocharger to an engine in series, and connects a high-pressure exhaust pipe and a low-pressure exhaust pipe to a high-pressure exhaust bypass provided in communication with each other. A high-pressure exhaust gas overflow valve is provided, and a check valve is provided in the air supply bypass provided to communicate the low-pressure air supply pipe and the high-pressure air supply pipe, and the exhaust gas overflow valve is operated according to the operating state of the engine. The valve was configured to open using an actuator.

With the above configuration, when the engine speed increases and the air supply pressure generated by the high-pressure turbocharger 1 exceeds the allowable limit of the engine, the actuator 26 or 43 is activated by the pressure inside the intake manifold 8 to prevent high-pressure exhaust gas from overflowing. The flow valve 17 is opened to reduce the amount of exhaust gas passing through the high pressure turbine 2, reducing the capacity of the high pressure turbocharger 1 and maintaining the pressure in the high pressure air supply pipe 7 within permissible limits.

When the engine speed reaches a medium speed and exceeds the capacity of the high-pressure turbocharger 1, the pressure inside the high-pressure exhaust pipe 5 increases, and the actuator 26, 27 or 4 operates according to the pressure.
3 further increases the opening area of the high-pressure exhaust gas flow valve 17, most of the exhaust gas flowing through the high-pressure exhaust pipe 5 flows through the high-pressure exhaust bypass 15, the high-pressure turbocharger 1 stops functioning, and supercharging is exclusively performed. The air supplied by the low pressure turbocharger 9 and discharged from the low pressure compressor 12 passes through the low pressure air supply pipe 14, the air supply bypass 21, and the check valve 2.
2 is opened, and air is supplied to the engine E through the high-pressure intake pipe 11.

Therefore, while supplying air with high air pressure to the engine from low to medium speeds where the engine is often used,
The engine charge pressure can be adjusted so that it does not exceed the engine's permissible limits.

<Example> Fig. 1 shows an example of a turbocharged engine according to the present invention, in which 1 is a high-pressure engine having a turbine 2 with a small allowable exhaust gas flow rate and a compressor 4 with a small discharge rate rotated coaxially with the turbine 2. In the turbocharger, a turbine inlet 2a is connected to an exhaust manifold 6 of the engine E by a high-pressure exhaust pipe 5, and a compressor outlet 4a is connected to an intake manifold 8 of the engine E by a high-pressure intake pipe 7.

Reference numeral 9 designates a low-pressure turbocharger having a turbine 10 with a large allowable exhaust gas flow rate and a compressor 12 with a large discharge amount rotated coaxially with the turbine 10.
0a is connected to the turbine outlet 2b of the high-pressure turbocharger 1 through a low-pressure exhaust pipe 13, and the compressor outlet 12a is connected to the compressor inlet 4b of the high-pressure turbocharger 1 through a low-pressure air supply pipe 14.

A high-pressure exhaust bypass 15 is provided between the high-pressure exhaust pipe 5 and the low-pressure exhaust pipe 13 to communicate with each other. is provided. Furthermore, a low-pressure exhaust bypass 18 is provided between the low-pressure exhaust pipe 13 and the turbine outlet 10b of the low-pressure turbine 10, and the bypass 18 is provided with a low-pressure exhaust gas overflow valve 20 that is rotated by an operating lever 19. There is. Further, an air supply bypass 21 is provided between the low pressure air supply pipe 14 and the high pressure air supply pipe 7, and a check valve 22 is rotatably provided on the bypass 21 by a pin 23. The check valve 22 is connected to the low pressure air supply pipe 14.
Although it is possible for the air to flow from the air to the high-pressure air supply pipe 7, it has a function of blocking the flow in the opposite direction.

The other end of the operating lever 16 for operating the high pressure exhaust gas overflow valve 17 is connected to the middle of a communication lever 24 with a pin 25, and actuators 26.2 are connected to both ends of the communication lever 24.
7 piston shafts 28, 29 are connected by respective pins 28a, 29a.

Said actuator 26.27 has a piston 32.3 connected to said piston shaft 28.29 in a cylinder 30.31.
3 is charged, and the upper end of the cylinder 30 is connected to the engine E.
The upper end of the cylinder 31 is connected to the intake manifold 8 of the engine E and the pipe 34, and the upper end of the cylinder 31 is connected to the high pressure exhaust pipe 5 of the engine E through a pipe 35, respectively. Note that 36.37 is a spring provided between the lower surface of the piston 32.33 and the inner wall of the cylinder 30.31.

The other end of the operating lever 19 for operating the low pressure exhaust gas overflow valve 20 is connected to a piston shaft 39 of an actuator 38.
are pin-connected. Like the actuators 26 and 27, the actuator 38 has a piston 41 connected to the piston shaft 39 inserted into a cylinder 40, and is pressed upward by a spring 42, and the upper end of the cylinder 40 is connected to the low pressure supply through a pipe 43. A tube is connected to the trachea 14.

Note that the low-pressure exhaust gas overflow valve 20 and its actuator 38 are not essential in the case of a diesel engine.

This is because, in a turbocharged diesel engine, by limiting the amount of fuel supplied per hour, the cylinder pressure can be limited within permissible limits.

Next, the operation of the above embodiment will be explained.

In the turbocharged engine of the present invention, supply air at a low speed 1, for example, 700 rpm is supplied by a high pressure turbocharger 1 and a low pressure turbocharger 9 disposed in series downstream thereof, and the supply air pressure at full engine load is is point a on the supply air pressure ratio curve a-b shown by the solid line in FIG. At this time, the air supply pressure generated only by the low-pressure turbocharger 9 is at point C on the solid line C-d in the figure.

The intake pressure at point a above is the maximum allowable intake pressure of the engine,
When the charge air pressure exceeds point a, the cylinder pressure exceeds the engine's permissible limits, or knocking occurs in the case of gasoline engines.

When the engine speed is increased beyond 700 revolutions per minute, the charge air pressure ratio follows the characteristics of the turbocharger and tends to increase beyond the maximum allowable charge air pressure ratio of the engine as shown by the solid line a-b.

At this time, in the turbocharged engine of the present invention, when the internal pressure of the high-pressure air supply pipe 7 exceeds the allowable maximum air supply pressure ratio, the cylinder 3 of the actuator 26 communicated with the pipe 34
0 internal pressure increases, and the piston shaft 2 passes through the piston 32.
8 moves downward against the spring 36, and rotates the communication lever 24 counterclockwise using the pin 29a as a fulcrum. As a result, the operating lever 16 is rotated clockwise via the pin 25, the high pressure exhaust gas overflow valve 17 is opened, and the exhaust gas flowing through the high pressure exhaust pipe 5 is allowed to flow into the high pressure exhaust bypass 15 as shown by the dotted line. Therefore, the pressure inside the high pressure air supply pipe 7 is the solid line a-
It is adjusted so that it does not exceed e. At this time, low pressure exhaust pipe 1
The flow rate and pressure within 3 increases, and the low pressure turbocharger 9 is energized to generate the charge air pressure remaining as indicated by the solid line ce in FIG.

Further, as the engine speed increases, the pressure inside the high-pressure exhaust pipe 5 also increases according to the characteristics of the turbocharger, and the pressure inside the cylinder 31 of the actuator 27, which is communicated with the high-pressure exhaust pipe 5 through the pipe 35, also increases.

The piston shaft 29 is pushed down via the piston 33 against the force of the spring 37, the communication lever 24 is rotated clockwise around the pin 28a, and the operating lever 16 is thereby further rotated clockwise to prevent the overflow. The opening area of the valve 17 is increased and the air supply pressure in the high-pressure air supply pipe 11 is adjusted so as not to exceed line ae-g in FIG. 2, which is the allowable limit for the engine.

In FIG. 2, when the engine speed is, for example, 2000 rpm, the opening area of the high-pressure exhaust gas overflow valve 17 becomes maximum, and most of the exhaust gas flows through the high-pressure exhaust bypass 15.
The air flows into the low-pressure exhaust pipe 13, and at the same time the high-pressure turbocharger 1 loses most of its functions, the low-pressure turbocharger 9 is energized and generates the charge air pressure shown at point e in Figure 2. At this time, most of the air supplied to the low pressure air supply pipe 14 passes through the air supply bypass 21, opens the check valve 22, and flows into the high pressure air supply pipe 7.

Also, in Figure 2, the engine speed is 2000 rpm/
If the rotation speed increases (or if knocking occurs due to excessive supply pressure in a gasoline engine),
As the air supply pressure attempts to rise beyond the allowable limit of the engine, the pressure of the low pressure air supply pipe 14 causes the piston 41 and piston shaft 39 in the cylinder 40 of the actuator 38 to resist the spring 42 through the pipe 43. and press down.
Rotate the operating lever 19 clockwise to open the low-pressure exhaust gas overflow valve 20, which has the same configuration as a known wastegate,
This maintains the maximum allowable intake air pressure of the engine at e-H.

In addition, at partial load, for example, 1/3 of 6,000 revolutions/minute
The amount of air required by the engine under load is shown in Figure 2, Actual #1e-
h, and at engine load or torque below the solid line e-h, the actuators 26 and 27 do not fully open the high-pressure exhaust gas overflow valve 17 but instead open the high-pressure exhaust gas overflow valve 17 completely. The exhaust gas exclusively energizes the turbine 2 of the high-pressure turbocharger 1 while flowing into the low-pressure turbocharger 9.

At this time, the high-pressure turbocharger is in a state close to full power operation, so if you want to rapidly increase the engine load or torque, press the accelerator pedal and open the throttle valve to increase the amount of air and increase fuel. By increasing the exhaust gas pressure, the actuator 27 connected through the pipe 35 of the exhaust manifold 6 is actuated to open the high-pressure exhaust gas overflow valve 17 via the operating lever 16, and both the high-pressure and low-pressure turbochargers 19 are accelerated immediately without a time lag. , responds sharply to engine load fluctuations.

In the example shown in FIG. 3, the actuator 27 that operates the high-pressure exhaust gas overflow valve 17 is replaced by the following structure.

That is, in parallel with the high-pressure exhaust bypass 15, there is a secondary high-pressure exhaust bypass 15 that communicates the high-pressure exhaust pipe 5 and the low-pressure exhaust pipe 13.
', and an auxiliary high-pressure exhaust gas overflow valve 17' is disposed there, and the other end of the operating lever 16' that rotates the valve 17' is rotated by the engine E through a link 44, and the actuator 27 is rotated by the engine E. It is connected to a governor (not shown) that operates at the operating engine speed.

Therefore, after the actuator 26 is activated, when the engine E reaches the operating speed of the governor, the link 44 is pulled to the left in FIG. The gas overflow valve 17' is opened, and most of the exhaust gas in the high-pressure exhaust pipe 5 flows through the high-pressure exhaust bypass 15 and the auxiliary high-pressure exhaust bypass 15', and the function of the high-pressure turbocharger 1 is lost as described above, and at the same time, the low-pressure turbo Charger 9 will be energized.

The example shown in FIG. 4 is a modification of the control means for the actuator that operates the high-pressure exhaust gas overflow valve 17,
An actuator 45 that operates the operating lever 16 of the overflow valve 17 connects a piston shaft 49 of a piston 48 pushed upward by a spring 47 within a cylinder 46 to the other end of the operating lever 16, and Pressure intake ports 50 and 51 are provided at the upper and lower ends of the cylinder.

On the other hand, a venturi pipe 52 is provided at the inlet 12b of the compressor 12 of the low-pressure turbocharger 9, and its constricted portion 5
3 and the pressure intake port 54.55 provided immediately before the pressure intake port 51.50 of the actuator 45 and the pipe 5, respectively.
6.57.

Therefore, the air flow rate through the venturi tube 52 is extracted as pressure by the pressure outlet 54.55, and
．． 57 is applied to the upper and lower sides of the piston 48 of the actuator 45 through the pressure inlets 51 and 50, so that the piston shaft 49 is balanced with the force of the spring 47 by the differential pressure between the pressure inlets 54 and 55 of the venturi tube 52. The opening of the overflow valve 17 can be adjusted via the operating lever 16.

Therefore, according to the example shown in FIG. 4, the high-pressure exhaust gas overflow valve 17 can be continuously controlled in accordance with the operating state of the engine at all speeds of the engine E, for example, 700 revolutions per minute or more.

<Effects of the Invention> As described above, the present invention connects the high-pressure and low-pressure turbochargers to the engine in series, and provides a high-pressure exhaust gas overflow valve to the high-pressure exhaust bypass provided to communicate the high-pressure exhaust pipe and the low-pressure exhaust pipe. In addition, a check valve is provided in each air supply bypass provided to communicate the low pressure air supply pipe and the high pressure air supply pipe, and the exhaust gas overflow valve is opened by an actuator operated according to the operating state of the engine. In this way, high charge air pressure is supplied to the engine from low to medium speeds, where the engine is most frequently used, and the engine's charge air pressure does not exceed the allowable limit of the engine. This has the effect of providing a turbocharged engine that can be adjusted, has a simple configuration, has good responsiveness, improves low-speed torque, and can avoid knocking.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the turbocharged engine of the present invention;
3 is a partial sectional view of the second embodiment, FIG. 4 is a partial sectional view of the third embodiment, and FIG. 5 is a torque curve and diagram of the engine of the present invention. Turbocharger Pressure Ratio Diagram FIG. 6 is a torque curve and turbocharger pressure ratio diagram of a conventional turbocharged engine. 1; High pressure turbocharger, 2; Turbine, 4; Compressor, 5; High pressure exhaust pipe, 6; Exhaust manifold,
7: High pressure air supply pipe, 9: Low pressure turbocharger, 10: Turbine, 12: Compressor, 13: Low pressure exhaust pipe,
14; Low pressure air supply pipe. 15; High pressure exhaust bypass, 16.16', 19; Operating lever, 17; High pressure exhaust gas overflow valve, 18; Low pressure exhaust bypass, 20; Low pressure exhaust gas overflow valve, 21; Supply air bypass, 22; Non-return Valve, 24;
Communication lever, 26.27, 38, 44; actuator, 28.29
, 39, 48; same piston shaft, 30. 31, 40, 45
Niji Linda. 32.33,41,47;Piston, 34.35,43,55,56;Pipe. 36. 37, 42, 46; spring, engine 1 raki 11 4 shi kudzu 21''

Claims (1)

[Claims] 1) High-pressure and low-pressure turbochargers are connected to the engine in series, and a high-pressure exhaust gas overflow valve is installed in the high-pressure exhaust bypass that connects the high-pressure exhaust pipe and the low-pressure exhaust pipe, and the low-pressure air supply pipe and high-pressure air supply pipe are connected. A turbocharger characterized in that a check valve is disposed in each intake air bypass provided in communication with each other, and the exhaust gas overflow valve is opened by an actuator that operates according to the operating state of the engine. engine.