JPH0241330Y2 - - Google Patents

Description

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

Generally, in turbocharged engines,
During low speed rotation when the amount of exhaust gas supplied from the engine is small, it is difficult to supply a sufficient amount of intake air from the turbocharger to the engine.

Therefore, if you fully depress the accelerator pedal to supply a large amount of fuel to the engine for acceleration when the engine is running at low speed, the engine will not be receiving enough air to match the fuel. Complete combustion will occur, resulting in a significant deterioration in smoke evacuation performance.

Conventionally, in order to eliminate the occurrence of such problems, the discharge air pressure of the turbocharger, that is, the boost pressure, was detected, and if the boost pressure was lower than the set value, the amount of fuel supplied to the engine was adjusted. It is known to employ a fuel limiting device (generally called a boost compensator) that limits fuel consumption to a low value that does not deteriorate smoke exhaust performance.

For convenience, this structure will be described below with reference to the accompanying drawings for explaining the embodiments of the present invention.

In FIG. 1, the reference numeral 10 indicates a diesel engine that is the prime mover of the truck, and the reference numeral 12 indicates a turbocharger that cooperates with the engine 10.

The turbo supercharger 12 described above includes a variable displacement exhaust gas turbine 16 connected to the exhaust manifold 14 of the engine 10, and the exhaust gas turbine 16.
is driven by the engine 10 and compresses the intake air.
The compressor 20 supplies the air to the intake manifold 18.

The above-described fuel is supplied to the engine 10 by the driver depressing an accelerator pedal (not shown) and displacing the control rack 24 inside the fuel injection pump 22 in the left-right direction in the figure. Fuel is metered and supplied according to the amount of depression of the accelerator pedal. And in the figure, numeral 26
generally shows the above-mentioned fuel restriction device (boost compensator), and this fuel restriction device 2
6 is a pressure chamber 30 into which the boost pressure of the compressor 20 is introduced via a conduit 28;
, a movable partition wall (diaphragm) 32 constituting a part of the pressure chamber 30, and a first diaphragm that always urges the movable partition wall 32 upward against the boost pressure introduced into the pressure chamber 30. a spring 34;
It is pivoted on an actuating member 38 and a pivot 40 which are pressed against a push rod 32' that is integrally fixed to the movable bulkhead 32 by a second spring 36, and one end thereof cooperates with the actuating member 38. The other end consists of a hook 44 that cooperates with a stopper 42 on the control 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 Pb is also low, and this low boost pressure is applied to the conduit 28. It acts on the inside of the pressure chamber 30 through the pressure chamber 30 and also acts on the movable partition wall 32 to push down the movable partition wall 32.

In the structure described above, boost pressure
When Pb is lower than the set pressure determined by the first spring 34, the actuating member 38 and the hook 44 are in the position shown in the figure, in other words, the control rack 24 is in a position in which it cannot move in the direction of increasing the amount of fuel. is held in

Therefore, even if the driver fully depresses the accelerator pedal at this point, the control rack 24 remains stopped at the position where its stopper 42 comes into contact with the hook 44, and the control rack 24 remains stopped in the direction of fuel increase (towards the left in the figure). ) remains unable to move.

Therefore, the amount of fuel supplied to the engine 10 is limited to an amount commensurate with the amount of air supplied to the engine set by the compressor 20. In other words, the amount of fuel supplied to the engine 10 is limited to the limited amount, and the smoke exhaust performance due to incomplete combustion is This will prevent the deterioration of

Further, as the rotational speed of the engine 10 increases and the discharge air pressure (Pb) from the compressor 20 increases accordingly, the pressure acting on the movable bulkhead 32 causes the first spring 34 and the second spring 36 to is displaced from its normal state, and the actuating member 38
is lowered from the illustrated position to allow the hook 44 to rotate clockwise. The control rack 24 is therefore allowed to move in the direction of increasing fuel, ie to the left in the figure. In this case, since the amount of air supplied to the engine 10 by the compressor 20 has also increased, a combustion state is set in which the smoke exhaust performance does not deteriorate even if the amount of supplied fuel increases.

Therefore, in order to improve the starting performance (ability to obtain output from a stopped state to clutch engagement) of a vehicle equipped with the above-mentioned turbocharged engine without deteriorating the smoke emission performance. It is important to be able to increase the rotational speed of the exhaust gas turbine as much as possible within a short period of time until the clutch is engaged, thereby increasing the amount of fuel supplied.

On the other hand, the engine 10 for automobiles such as trucks,
The engine may be operated in an extremely wide range of rotation speeds, from idle rotation speed to maximum rotation speed, and may be operated with frequent changes in rotation speed. Therefore, an exhaust gas turbine having a fixed nozzle cannot sufficiently and effectively recover the energy contained in the exhaust gas of the engine.

Therefore, variable displacement turbines equipped with variable nozzle vanes that change the nozzle area at the inlet of the turbine rotor in accordance with engine speed and load have already been put into practical use.

In FIG. 1, the variable capacity turbine described above includes variable nozzle vanes 4 in the exhaust gas turbine 16.
6, and the opening degree of the vane is controlled by a pneumatic actuator 48, for example, in three stages with high, medium, and low zones set based on the engine speed (Ne) and load (T). It's becoming like that.

That is, the pneumatic actuator 48 in the above-mentioned turbine includes a first piston 52 and a second piston 54 inserted in tandem within a cylinder 50, with a piston located at an intermediate position corresponding to between each piston. , a stopper 56 for limiting the stroke of the first piston 52 is provided.

The above-mentioned pressure chambers of the first piston 52 and the second piston 54 are connected to the first and second electromagnetic chambers, which are normally set to the atmosphere open position and the supply of air is cut off when no electricity is applied. It is connected to a compressed air tank 62 via valves 58 and 60, and these solenoid valves 58 and 60 respectively receive a rotational speed signal Ne of the engine 10 and a load signal T typically represented by the accelerator opening of the engine 10. It is designed to be opened and closed by the solenoid valve operation output from the controller 64 that receives the input.

Conventionally, the opening/closing control of the solenoid valves 58 and 60 is performed at a relatively low rotational speed of the engine 10 of Ne ₁ or less and in a high load region A, as shown in FIG. Sometimes both solenoid valves 58,
60 are both energized and opened to allow air supply. Therefore, the compressed air tank 6
2, compressed air is supplied to the pressure chambers of both the first and second pistons 52, 54. In this case, the variable nozzle vane 46 of the exhaust gas turbine 16 is set to the minimum nozzle area, and the The gas flow rate is kept to a minimum.

Next, when the rotational speed of the engine 10 exceeds Ne ₁ and the engine is operating in the high load region B, only the first solenoid valve 58 is opened by the output from the controller 64, and the compressed air is discharged from the compressed air tank 62. Compressed air is supplied to the pressure chamber of the first piston 52 . At this time, the compressed air in the pressure chamber of the second piston 54 is released to the atmosphere.

Therefore, the first piston 52 moves toward the left in the figure until it comes into contact with the stopper 56, and the variable nozzle vane 46 is moved to the second position via the second piston 54.
In this case, the exhaust gas turbine 16 sets the flow rate of the exhaust gas to a medium level.

On the other hand, in Fig. 5, the engine speed is sign
If Ne exceeds ₂ , regardless of the load, and
Load switching line d even at rotation speeds below Ne ₂
In the following low load area C, the controller 5
In addition to the second solenoid valve 60, the above-mentioned first solenoid valve 58 is also closed by the output from the compressed air tank 62, and the supply of compressed air from the compressed air tank 62 to the pressure chamber of the first piston 52 is also cut off. At this time, the pressure chamber of the first piston 52 is opened to the atmosphere. Therefore, the second
The piston 54 further moves toward the right side by the biasing means in the cylinder 50, sets the opening degree of the variable nozzle vane 46 to the third opening degree, in this case the maximum opening degree, and discharges the exhaust gas. The air flow rate in the turbine 16 is set to the maximum amount.

As is clear from the above explanation, in a vehicle equipped with a conventional engine equipped with a supercharger equipped with a variable capacity exhaust gas turbine, the engine speed is low when starting from a stopped state, so the exhaust gas turbine 16
will be operated in region C in FIG.

Therefore, in such a structure, when starting from a stopped state, the compressor 2
The slow rise of the zero boost pressure Pb and the aforementioned fuel restriction device (boost compensator) 2
Coupled with the fact that the amount of fuel supplied to the engine is limited by the effect of No. 6, there is a problem that the starting acceleration is inevitably inferior.

Moreover, when you release the accelerator pedal, such as when changing gears while driving,
Due to the drop in rotational speed and load that occurs at that time, the exhaust gas turbine 16 is in the region C in FIG. That will happen. Furthermore, since the amount of fuel injected is minimized by reducing the accelerator opening, the time it takes to press the accelerator pedal again and obtain the engine speed corresponding to the specified torque becomes longer. As a result, the start-up until the predetermined torque is obtained after the gear change is delayed, giving the impression that the engine has poor responsiveness to depression of the accelerator pedal.

Therefore, the present invention was developed in view of the above, and its purpose is to provide a turbo overload that can improve the poor transient response on the engine side, which affects starting acceleration and re-acceleration. The goal is to obtain a powered engine.

In order to achieve this objective, the present invention provides 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 the air supplied to the engine; The exhaust gas turbine includes a fuel supply device that supplies fuel to the engine, and a fuel restriction device that controls the amount of fuel supplied by the fuel supply device in response to the discharge air pressure of the turbocharger, In a turbocharged engine that is operated with a nozzle area that changes by an actuator that operates depending on the engine speed and load, settings are made for the actuator used to set the nozzle area of the exhaust gas turbine. It is proposed to set the position of the exhaust gas turbine so that the nozzle area of the exhaust gas turbine is minimized in response to releasing the accelerator pedal when the nozzle area is at the maximum at a point in time when the rotation speed is higher than the rotation speed. It is something to do.

According to the present invention, when the engine speed is below a predetermined speed, the nozzle area is minimized regardless of the load size, and when the engine speed is above the predetermined speed,
In other words, even at the maximum nozzle area,
When the accelerator pedal is released, the nozzle area can be set to the minimum area to increase sensitivity regarding the rise in boost pressure.

The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 is a block diagram for explaining the overall configuration of a turbocharged engine according to an embodiment of the present invention, and the reference numerals used in the above description of the components shown in FIG. 1 are used as they are. Let me preface this.

That is, in this embodiment, the input side of the controller 64 receives the engine speed (Ne) signal and the load (T) from the load sensor.
In addition to the signal, a signal from an accelerator pedal sensor 65 is also input.

The above-mentioned load sensor is, for example, installed in a fuel injection pump, and the load lever is set to a predetermined value (for example, the load switching shown in FIG. The accelerator pedal sensor 65 is composed of a switch that is turned ON when the vehicle has moved an amount corresponding to line d) or above to indicate a high load, and the accelerator pedal sensor 65 is composed of a micro switch that can be brought into contact with and separated from the accelerator pedal. , turns ON when the accelerator pedal is released, and remains OFF while the accelerator pedal is depressed.

The accelerator pedal sensor 65 may be used as a switch for detecting the initial position of the control rack in the fuel injection pump when the accelerator pedal is released.

In the controller 64 described above, the opening degree of the variable nozzle vane is set based on engine speed information, load information, and accelerator pedal depression information, and the opening degree map is shown in FIG. 2 and FIG. As shown in Figure 4.

In addition, in FIG. 4, the display "→" indicates that the accelerator pedal sensor 65 is ON.
After turning OFF, in other words, after a predetermined time (t) has elapsed since the accelerator pedal was released and pressed again, the nozzle area changes from the state where the minimum area is set to the nozzle area. Let me preface this by saying that this means changing to the state of , that is, the state where the maximum area is set.

In other words, in Figures 2 and 4, when the engine speed (Ne) is lower than the preset low engine speed (Ne ₀ ) (area indicated by symbol A in Figure 4), the load sensor The minimum nozzle area is set regardless of the result of load detection (detecting a load that is above or below the load switching line indicated by d in FIG. 5 as a reference).

Therefore, in this state, the controller 64:
A signal for opening both the first and second solenoid valves 58 and 60 is output, and compressed air is supplied to the pneumatic actuator 48 via the solenoid valves 58 and 60.
The pressure chamber of the first piston 52 and the pressure chamber of the second piston 54 are supplied.

When the engine speed (Ne) is higher than the above-mentioned low speed (Ne ₀ ), for example, lower than the predetermined speed (Ne ₁ ) in the medium speed range (in FIG. 4,
In the area indicated by symbol B), the result of the load detection from the load sensor indicates that the load is higher than the load switching line d and the accelerator pedal sensor 65 is OFF.
In other words, when the accelerator pedal is depressed, the first and second solenoid valves 58, 60 described above
, set the minimum nozzle area, and set the nozzle area to the minimum state if the load switching line d or less and the accelerator pedal is not depressed (accelerator pedal sensor 65 is ON). (state) to the maximum state (state), and when the accelerator pedal is depressed (accelerator pedal sensor 65 is OFF), the nozzle area is set to the maximum.

Therefore, when the nozzle area is set to the maximum, no signal is output from the controller 64 to both the first and second electromagnetic valves 58, 60, so that both electromagnetic valves 58, 60 are de-energized. Therefore, it is set to the atmosphere open position, which is the normal position.

On the other hand, the predetermined rotation speed (Ne ₁ ) at a rotation speed where the engine rotation speed (Ne) corresponds to the intermediate speed range mentioned above.
, and lower than the predetermined rotation speed (Ne ₂ ) in the rotation speed range corresponding to the high speed range (region indicated by symbol C in Fig. 4), based on the result of load detection from the load sensor, When the load is higher than the load switching line d and the accelerator pedal sensor 65 is OFF, in other words, the accelerator pedal is being depressed, the energization setting is made only to the first solenoid valve 58, and the intermediate level is set. Set the nozzle area.

Therefore, in this state, the controller 64
A signal for opening only the first solenoid valve 58 is output, and compressed air is supplied to the pressure chamber of the first piston 52 in the pneumatic actuator 48 via the solenoid valve 58.

In addition, in the area indicated by symbol C in FIG. 4 mentioned above, when the load is below the load switching line d and the accelerator pedal is not depressed (accelerator pedal sensor 65 is ON), the nozzle area is set to the minimum state ( state) to the maximum state (state of),
When the accelerator pedal sensor is depressed (accelerator pedal sensor 65 is OFF), the nozzle area is set to the maximum. Therefore, when setting the minimum nozzle area, the first and second solenoid valves 58, 60 are energized as described above, and the first piston 5 is energized via these two solenoid valves 58, 60.
When compressed air is supplied to the second pressure chamber and the pressure chamber of the second piston 54 and the maximum nozzle area is set, both the electromagnetic valves 58 and 6 are
Both solenoid valves 58 and 60 were not energized to zero.
The atmosphere open position, which is the normal position, is set.

Furthermore, when the engine speed (Ne) is above the high speed range (Ne ₂ ), the result of the load detection from the load sensor indicates that the accelerator pedal sensor 65 is under high load above the load switching line d.
OFF, in other words, when the accelerator pedal is depressed, the first and second solenoid valves 58,
The maximum nozzle area is set as the normal atmosphere open state without energization setting to 60, and
When the load switching line d or less is applied and the accelerator pedal is not depressed (accelerator pedal sensor 6
5 is ON), the nozzle area is shifted from the minimum state (state) to the maximum state (state), and when the accelerator pedal is depressed (accelerator pedal sensor 65 is OFF), the nozzle area is changed. Set to maximum.

Therefore, in setting the nozzle opening degree in this way, the area A shown in Fig. 2 is expanded.In other words, when the engine speed is low, the area A shown in FIG. The nozzle area is designed to improve the rise of boost pressure (Pb). Therefore, by improving the boost pressure rise, the fuel restriction device 26
As fuel supply restrictions are relaxed, it is expected that the starting performance of the vehicle will be improved.

The actual operation control of the controller 64 described above will now be explained with reference to the operating situation shown in FIG. 3.

That is, in FIG. 3, after the engine is started and goes through an idling state, the engine changes from A to D.
The setting of the nozzle area in the region indicated by is as explained in FIG. 4.

In other words, when the accelerator pedal is pressed to start from an idling state after starting the engine, the nozzle area is set to the minimum state (), and the rotation speed of the exhaust gas turbine can be set to increase. By this, boost pressure (Pb)
In this state, the fuel restriction device 26 increases the boost pressure (Pb).
By increasing the height, it becomes easier to move the control rack 24 in the direction of increasing the amount of fuel. Therefore, the time it takes to engage the clutch for starting can be shortened by increasing the boost pressure and increasing the amount of fuel, which shortens the time it takes for the engine speed to rise enough to obtain the torque required to engage the clutch. .

On the other hand, in Figure 3, engine speed (Ne)
When the vehicle is cruising with the load sensor OFF and the accelerator pedal is temporarily released to change gears, the sign (Ne > Ne _{0 )} will appear in Figure 3.
As shown in the area shown, the accelerator pedal sensor 6
5 is turned on, and based on these conditions, the nozzle area is set to the minimum state () as explained in FIG. This state is maintained for a predetermined time t (t>0) even when the accelerator pedal is depressed again and the accelerator pedal sensor 65 is turned off, and then the nozzle area is set to the maximum state ( ).

In this case, generally, when the accelerator pedal is released, the rack 24 of the fuel pump 22 is released.
returns to its initial state, and since the nozzle area of the exhaust gas turbine 16 at that point is in the maximum state () as described above, the compressor 2
The boost pressure (Pb) at
However, since the nozzle area of the exhaust gas turbine 16 is set to the minimum state ( ) as described above, the boost pressure (Pb) at the compressor 20 increases. Therefore, the actuating member 38 is such that the hook 44 is attached to the hook 24.
The movement is such that it takes a longer time to lock the stopper 42. Therefore, when the accelerator pedal is depressed again, the rack 24 of the fuel pump 22 can be moved relatively freely, so that the fuel supply amount can be set relatively quickly in accordance with the amount of depression of the accelerator pedal. As a result, the rotational speed and torque can be started from a state where there is not much of a drop, so that the rise until reaching a predetermined torque after a gear change, in other words, the transient characteristics are improved.

Note that the set rotation speed Ne ₀ mentioned above is, for example, in a truck diesel engine, when the idle speed is
In the case of 500 rpm, as an example, Ne ₀ =800 rpm, and Ne ₁ and Ne ₂ are set to 1150 rpm and 1650 rpm, respectively.

Further, when the accelerator pedal sensor is turned off, the nozzle area may be maintained at the minimum nozzle area for a certain period of time t seconds.

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, it is possible to improve the starting performance of the vehicle and the transient response after gear change. Responsiveness can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the overall configuration of a turbocharged engine according to an embodiment of the present invention, and FIG.
The figure shows shaft torque T on the vertical axis and rotation speed Ne on the horizontal axis.
Diagram 3 for explaining the characteristics of the turbocharged engine according to the embodiment of the present invention shown by taking
The figure is a table for explaining the characteristics of the main parts in the configuration shown in Fig. 1, Fig. 4 is a diagram showing the operating mode of the engine according to the embodiment of the present invention shown in Fig. 1, and Fig. 5 2 is a characteristic diagram corresponding to FIG. 2 for explaining the characteristics of a conventional turbocharged engine. 10... Engine, 12... Turbo supercharger, 1
6...Exhaust gas turbine, 20...Compressor, 22...Fuel supply device, 24...Rack, 2
6... fuel restriction device, 38... operating member, 46...
...Variable capacity nozzle vane, 48...Pneumatic actuator, 64...Controller, 65...
...Accelerator pedal sensor.

Claims (1)

[Claims for Utility Model Registration] 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 the intake air of the engine; a fuel supply device that supplies fuel; and a fuel restriction device that controls the amount of fuel supplied by the fuel supply device in response to the discharge air pressure of the turbocharger; In a turbocharged engine that is operated with a nozzle area that changes by an actuator that operates according to The turbo overflow is characterized in that the position of the exhaust gas turbine is set so that the nozzle area of the exhaust gas turbine is minimized in response to release of the accelerator pedal when the nozzle area is at the maximum at the time. Fueled engine.