JPH0240272Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a turbocharged engine for vehicles such as trucks.

As is well known in the art, in a turbocharged engine, the turbocharger supplies a sufficient amount of intake air to the engine at low speeds when the amount of exhaust gas supplied from the engine is low. It is difficult to do so. Therefore, when the engine is running at low speed and the accelerator pedal is fully depressed for acceleration, etc., and a large amount of fuel is supplied to the engine, insufficient air is provided to match the amount of fuel, resulting in incomplete combustion. The smoke evacuation performance deteriorates significantly. Therefore, conventional methods have been used to detect the discharge air pressure of the turbocharger, that is, the boost pressure, and when the boost pressure is lower than a set value, to limit the amount of fuel supplied to the engine to a certain low value that does not deteriorate the smoke exhaust performance. A fuel restriction device (commonly called a boost compensator) is used.

For convenience, this will now be described with reference to the accompanying drawings, which illustrate one embodiment of the present invention. In the figure, 10 is a diesel engine that is the prime mover of the truck, and 12 is a turbo supercharger that cooperates with the engine 10. The turbo supercharger 12 is connected to the exhaust manifold 14 of the engine 10.
a variable displacement exhaust gas turbine 16 connected to
and a compressor 20 driven by the exhaust gas turbine to compress intake air and supply it to the intake manifold 18 of the engine 10. Fuel is supplied to the engine 10 by the driver depressing an accelerator pedal (not shown) to displace the rack 24 of the fuel pump 22 in the left-right direction in the figure. Reference numeral 26 generally indicates the above-mentioned fuel restriction device, which includes a pressure chamber 30 into which the boost pressure of the compressor 20 is introduced through a conduit indicated by 28 in the figure, and a movable partition forming a part of the pressure chamber. (Diaphragm) 32, a first spring 34 that always urges the movable bulkhead 32 upward in opposition to the boost pressure introduced into the pressure chamber 30, a push rod 32 that is integrally fixed to the movable bulkhead 32. ' The actuating member 3 is pressed against the second spring 36.
8, and a hook 44 pivoted on a pivot 40, one end of which cooperates with the actuating member 38, and the other end of which cooperates with a stopper 42 on the fuel rack 24.

In the above device, when the rotation speed of the engine 10 is low and the amount of exhaust gas supplied to the exhaust gas turbine 16 is small, the discharge air pressure of the compressor 20, that is, the boost pressure P _b is also low, and this low boost pressure is transmitted from the conduit 28. It is supplied into the pressure chamber 30 and presses down the movable partition wall 32. However, when the boost pressure _Pb is lower than the set pressure determined by the first spring 34, the actuating member 38 and the hook 44 are in the positions shown, respectively. Therefore, even if the driver fully depresses the accelerator pedal, the rack rod 24 stops at the position where its stopper 42 contacts the hook 44, and cannot move any further in the direction of fuel increase (to the left in the figure). . Therefore, the amount of fuel supplied to the engine 10 is
0, the amount of air supplied to the engine is limited to a limit commensurate with the amount of air supplied to the engine, thereby preventing deterioration of smoke exhaust performance. Also, as the rotational speed of the engine 10 increases, the discharge air pressure P _b of the compressor 20 increases.
increases and the first spring 34 and second spring 36 are overcome by the downward force acting on the movable bulkhead 32, the actuating member 38 is lowered from the illustrated position and the hook 44 is rotated clockwise in the figure. Therefore, the fuel rack 24 can be moved in the fuel increasing direction, that is, to the left in the figure. In this case, since the amount of air supplied to the engine 10 by the compressor 20 is also increasing, the smoke exhaust performance does not deteriorate even if the amount of supplied fuel increases. Therefore, in a vehicle equipped with the above-mentioned turbocharged engine,
In order to improve starting performance (from a stopped state to clutch engagement) without deteriorating smoke exhaust performance, it is necessary to increase the rotation speed of the exhaust gas turbine as much as possible within a short period of time until clutch engagement. , it is important to be able to increase the amount of fuel supplied.

On the other hand, the engine 10 of a motor vehicle such as a truck is operated over an extremely wide range of rotation speeds, from an idle rotation speed to a maximum rotation speed, and frequently changes the rotation speed. Therefore, exhaust gas turbines with fixed nozzles cannot recover the energy contained in the exhaust gas of the engine sufficiently effectively. Therefore, variable displacement turbines have already been put into practical use that include variable nozzle vanes that change the nozzle area at the inlet of the turbine rotor in accordance with the engine speed and load. In the illustrated case, the exhaust gas turbine 16 includes a variable nozzle vane 46 whose opening degree is controlled in three stages by a pneumatically responsive actuator 48 . The actuator 48 is connected to the cylinder 5
A first piston 52 and a second piston 54 are inserted in tandem into the piston 0, and a stopper 56 is provided in the middle to limit the stroke of the first piston. Then, the first piston 52, the second piston 5
The pressure chambers 4 have first and second solenoid valves 58 and 6, respectively.
0 to a compressed air tank 62, these solenoid valves 58, 60 each receive as input a rotational speed signal Ne of the engine 10 and a load signal T typically represented by the engine accelerator opening. It is designed to be opened and closed by a controller 64 that generates the electromagnetic valve operating output described in . In the conventional device, as shown in FIG. 2, when the engine 10 is operating in a relatively low rotational speed range of Ne ₁ or less and in a high load area A, both the solenoid valves 58 and 60 are closed. When closed, the variable nozzle vanes 46 of the exhaust gas turbine 16 are operated with a minimum nozzle area, or in other words, a minimum flow characteristic. Next, when the engine speed exceeds the above Ne ₁ and is operating in the high load region B, the first solenoid valve 58 is opened by the output of the controller 64,
Compressed air is supplied from the compressed air tank 62 to the pressure chamber of the first piston 52 . Therefore, the first piston 52 moves to the left until it contacts the stopper 56, and the variable nozzle vane 46 is adjusted to the second opening degree via the second piston 54. In other words, the exhaust gas turbine 16 has an intermediate flow rate characteristic. be driven with.
Furthermore, when the engine speed exceeds Ne ₂ , regardless of the load, and even if the engine speed is below Ne ₂ , in the low load region C below the load switching line d, the output of the controller 64 Then, the second solenoid valve 60 is opened, and the compressed air tank 62 is supplied to the second piston 5.
Compressed air is supplied to pressure chamber 4. Therefore, the second piston 54 moves further to the left, changing the variable nozzle vane 46 to the third opening degree, and as a result, the exhaust gas turbine 16 is operated with the maximum flow rate characteristic.

As can be easily understood from the above explanation, in a vehicle equipped with an engine equipped with a supercharger equipped with a conventional variable capacity exhaust gas turbine, when starting from a stopped state, the engine speed is usually low, so the exhaust gas The gas turbine 16 is operated in the region C of FIG. 2, and therefore the rise of the output boost pressure P _b of the compressor 20 is slow, and the fuel supply to the engine is reduced by the action of the fuel restriction device (usually a boost compensator) 26 described above. Since the speed is limited, there is a problem that the starting acceleration performance is inevitably inferior.

This invention was devised in view of the above circumstances.
The exhaust gas turbine is driven by the engine exhaust gas, and the exhaust gas turbine is driven by the same exhaust gas turbine.
A turbo supercharger consisting of a compressor that pressurizes the intake air of the engine, a fuel supply device that supplies fuel to the engine, and a fuel supply amount of the fuel supply device that adjusts the amount of fuel to be supplied by the fuel supply device in response to the discharge air pressure of the turbo supercharger. The exhaust gas turbine is further provided with a fuel restriction device that limits the fuel, and the exhaust gas turbine is operated with a plurality of nozzle areas that vary depending on engine speed and load, wherein the engine speed is set to a set speed. or less, the gist is an engine with a turbo supercharger, characterized in that the exhaust gas turbine is configured to be operated with a minimum nozzle area, regardless of the engine load. It is.

Below, the embodiments of the present invention will be explained again in Figures 1 and 3.
This will be explained in detail with reference to the drawings. According to the present invention, as shown in the characteristic diagram of Fig. 3, when the engine rotation speed is less than a preset low rotation speed Ne ₀ , the exhaust gas is discharged with the minimum nozzle area regardless of the load. The gas turbine 16 is then operated. In other words, area A in FIG. 2 is widened as shown in FIG. 3. The set rotational speed Ne ₀ is selected to be approximately 800rpm, for example, when the idle rotational speed is 500rpm in a truck diesel engine. By adopting such a configuration,
When the vehicle starts from a standstill and before the clutch is engaged, the compressor 20 is operated so that the exhaust gas turbine 16 is operated with a minimum nozzle area.
Since the boost pressure P _b rises quickly and the fuel supply restriction of the fuel restriction device 26 is correspondingly relaxed,
The starting performance of the vehicle is significantly improved compared to the conventional method. Note that the expansion of the region A is achieved by controlling the rotation speed signal Ne in the controller 64 in the conventional device.
This can be realized very easily by, for example, providing a simple gate so that the output signal is not emitted until Ne ₀ is reached.

As described above, according to the present invention, by making slight modifications to the operating characteristics of a conventional supercharged engine equipped with a variable displacement exhaust gas turbine, the starting performance of a vehicle can be significantly improved. Because it is possible to
Extremely useful.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention;
Figure 2 is a characteristic diagram of a conventional engine with a variable displacement turbocharger, with shaft torque T on the vertical axis and rotational speed Ne on the horizontal axis, and Figure 3 is a characteristic diagram of a conventional variable displacement turbocharged engine with the variable displacement turbocharger according to the present invention. FIG. 2 is a characteristic diagram similar to FIG. 2 of the attached engine. 10...Engine, 24...Fuel rack, 12
...Turbo supercharger, 26...Fuel restriction device, 16
...Exhaust gas turbine, 64...Controller,
20...Completsa.

Claims (1)

[Scope of utility model registration request] A turbo supercharger consisting of an exhaust gas turbine driven by engine exhaust gas and a compressor driven by the exhaust gas turbine to pressurize intake air of the engine; a fuel supply device that supplies fuel to the engine; The exhaust gas turbine includes a plurality of fuel limiting devices that limit the amount of fuel supplied by the fuel supply device in response to the discharge air pressure of the turbo supercharger, and further includes a plurality of exhaust gas turbines that change in accordance with engine speed and load. When the engine speed is below the set speed, the exhaust gas turbine is operated with the minimum nozzle area regardless of the engine load. An engine with a turbo supercharger, characterized in that it is configured to