JPS6248929A - Controller for mechanical supercharger - Google Patents

Abstract

PURPOSE:To keep a low rate of fuel consumption as well as to prevent black smoke from occurring at the time of high load, by regulating a degree of opening in a control valve in a bypass passage according to oxygen content when a mechanical supercharger operates. CONSTITUTION:A control valve 34 is in a state of full-open at a low load range where a supercharger is nonoperational. An output voltage out of an oxygen content sensor 43 in an exhaust passage 42 is read and thereby whether the output voltage V is smaller than the setting value and oxygen content is smaller than the specified value or not are discriminated by an electronic control part 51. When the oxygen content is smaller, a step motor 1 of an actuator 37 is rotated, and if the control valve 34 is operated in a closing direction, a flow passage area of a second passage 32 becomes smaller whereby an air quantity flowing in a first passage 31 increases instead, so that supercharging pressure of suction air by the superchager 33 goes up. And, when the oxygen content is larger, the control valve 34 is operated in a opening direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for the boost pressure of a mechanical supercharger (supercharger) provided in the intake system of a diesel engine.

[Conventional technology and problems]

Superchargers are excellent in terms of responsiveness, but the driving loss due to supercharging is large, and fuel consumption will be poor if they are driven all the time. Therefore, it is necessary to control the supercharger to drive it as necessary. Conventionally, the upstream and downstream sides of the supercharger are connected by a bypass passage, and a control valve is provided in this bypass passage, and the opening degree of this control valve is controlled. A configuration is known in which the pressure is changed depending on the amount of depression of the accelerator pedal. Now, in a diesel engine, the amount of fuel injected changes depending on the amount of depression of the accelerator pedal, etc., but this injection amount varies, so the opening degree of the control valve is changed depending on the amount of depression of the accelerator pedal. For example, the air-fuel ratio may become too rich and black smoke may be generated.

The present invention was made to maintain low fuel consumption by driving the supercharger only when necessary, and to prevent the air-fuel ratio from becoming too rich during high loads to avoid the generation of black smoke. It is.

[Means for solving problems]

A control device for a mechanical supercharger according to the present invention is a control device for a mechanical supercharger provided in a first passage formed in the middle of an intake passage of a diesel engine, and the control device is a control device for a mechanical supercharger provided in a first passage formed in the middle of an intake passage of a diesel engine. A drive mechanism that operates the mechanical supercharger when It is characterized by comprising an oxygen concentration sensor that detects the oxygen concentration, and a control means that adjusts the opening degree of the control valve according to the oxygen concentration when the mechanical supercharger is operated.

〔Example〕

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

In FIG. 1, a piston 13 is slidably accommodated in a cylinder pore 12 formed in an engine body 11.
A combustion chamber 14 is defined between the top surface of the piston 13 and the cylinder bore 12.

An intake boat 16 formed in the cylinder bed 15 is opened and closed by an intake valve 17, and an exhaust port 18 is opened and closed by an exhaust valve 19. The fuel injection valve 21 is disposed at the upper center of the combustion chamber 14 and injects fuel fed under pressure from the fuel injection pump 22 into the combustion chamber 14 . The pulley 23 of the fuel injection pump 22 is connected to the connecting rod 2 of the piston 13.
The fuel injection pump 22 is driven by the rotation of the crankshaft 25, and the amount of fuel injected depends on the amount of depression of the accelerator pedal 28. It is now determined that

The middle of the intake passage 30 leading to the intake boat 16 is separated into a first passage 31 and a second passage 31, 32, a supercharger 33 is disposed in the first passage 31, and a supercharger 33 is disposed in the second passage 32.
A control valve 34 is provided to change the flow path area. Second
The passage 32 connects the upstream side and the downstream side of the supercharger 33. Therefore, the smaller the opening degree of the control valve 34, the more the amount of air flowing through the first passage 31 increases, and the supercharging effect by the supercharger 33 increases. Note that the control valve 34 is
The supercharger 33 is fully open in a low load range where it does not operate. The supercharger 33 has a clutch, which is connected to the pulley 26 of the crankshaft 25 via a pulley 29 and a belt 35, and is connected when the solenoid 36 is energized and disconnected when the solenoid 36 is demagnetized. ing. De-energization of the solenoid 36 is controlled by an electronic control section 51, which will be described later. On the other hand, the control valve 34 is operated by an actuator 37 having a step motor.
The actuator 37 is driven to open and close by the electronic control section 51.

An air cleaner 38 is provided at the inlet of the intake passage 30, and a surge tank 3 is provided downstream of the control valve 34.
9 is provided with an intake temperature sensor 41. Intake temperature sensor 4
The output signal of 1 is input to the A/D converter 55 of the electronic control section 51. On the other hand, an oxygen concentration sensor 43 is provided in the exhaust passage 42.
is provided, and the output signal of this sensor 43 is also sent to the electronic control unit 5.
The signal is input to the A/D converter 55 of No. 1. accelerator pedal 2
An accelerator switch 44 is provided near 8. The accelerator switch 44 is activated when the accelerator pedal 28 is depressed by 3.
/4 or more, it is configured to turn on, and this ON signal is sent to the input/output port (I/O) of the electronic control unit 51.
10 port) 56.

The electronic control unit 51 includes a central processing unit (CPU) 52
, a read-only memory (ROM) 53, a random access memory (RAM) 54, an A/D converter 55, and an I10 port 56, which are interconnected by a bus 57. Further, a drive circuit 58 for de-energizing the solenoid 36 is connected to the I10 port 56. C.P.
U52 controls clutch 36 via drive circuit 58 and opens/closes control via actuator 37 according to a program stored in ROM 53.

Figures 2 and 3 show supercharger 3, respectively.
3 and a flowchart of programs for controlling the control valve 34, for example, 30°
Interrupt processing is performed for each crank angle.

In the flowchart of FIG. 2, in step 101, it is determined whether the accelerator switch 44 is in the ON state or not. If it is in the ON state, step 102 is executed and the solenoid 36 is activated to drive the supercharger 33. Excite and connect the clutch, if it is not in the ON state, step 1
03 to demagnetize the solenoid 36 and disconnect the clutch in order to stop the supercharger 33. Pulley 2
9 receives the rotation of the pulley 26 of the crankshaft 25 via the belt 35, and is constantly rotating while the engine is running.
The rotation of this pulley 29 is controlled when the accelerator switch 44 is turned on.
In this state, the signal is transmitted to the supercharger 33 via the clutch.

In the flowchart of FIG. 3, in step 201, it is determined whether or not the supercharger 33 is being driven, that is, whether the solenoid 36 is energized. If it is being driven, steps 202 and subsequent steps are executed; If so, skip the following steps and finish this program. In step 202, the output voltage V of the oxygen concentration sensor 43 is
I Read. As shown in FIG. 4, this output voltage {circle around (2)} is proportional to the oxygen concentration, and the higher the oxygen concentration, the higher the output voltage V becomes.

In step 203, it is determined whether the output voltage ■ is smaller than the set value Vref, that is, whether the oxygen concentration is smaller than the predetermined value. If the oxygen concentration is small, step 20
4 to set the step motor of actuator 37 to 1.
The control valve 34 is rotated by one step and the control valve 34 is closed by one step. As a result, the flow area of the second passage 32 becomes smaller and the amount of air flowing through the first passage 31 increases, thereby increasing the supercharging pressure of the intake air by the supercharger 33.

FIG. 5 shows the relationship between the opening degree of the control valve 34 and the supercharging pressure. As can be understood from this graph, the smaller the opening degree of the control valve 34, the more the supercharging pressure increases linearly. When the control valve 34 closes and the boost pressure increases, the excess air ratio λ
The value of (actual air amount/air amount at stoichiometric air-fuel ratio) increases, and harmful exhaust components such as soot and HC are reburned. When the accelerator pedal 28 is further depressed, the fuel injection amount increases and the oxygen concentration decreases, step 204
At this time, the control valve 34 is further closed, and the excess air ratio λ is maintained at a predetermined value.

On the other hand, in step 203, the output voltage V is set to the set value Vr.
If it is determined that the oxygen concentration is greater than ef, that is, if it is determined that the oxygen concentration is large, step 205 is executed, the step motor of the actuator 37 is rotated by one step, and the control valve 34 is opened by one step. As a result, the second
The flow area of the passage 32 increases, the amount of air flowing through the first passage 31 decreases, and the supercharging pressure of intake air decreases.

As described above, in this embodiment, the supercharger 33 is
Drives when the accelerator pedal 28 is pressed a lot during direct loading,
The system is designed to pause when the load is low, and to change the supercharging pressure depending on the oxygen concentration in the exhaust gas during operation. By stopping the supercharger 33 during low-load operation in this way, the loss caused by driving the supercharger can be reduced by this amount.
This can prevent deterioration of fuel efficiency. Furthermore, during high-load operation, the supercharging pressure is changed according to the oxygen concentration detected by the oxygen concentration sensor 43, and the excess air ratio λ is always controlled to a constant value, thereby preventing the generation of black smoke. be able to. Furthermore, in this embodiment, a control valve 34 is provided in the second passage 32, and the control valve 34 is kept fully open during low load so that the oxygen concentration in the exhaust gas reaches a predetermined value after the supercharger 33 is driven. Since the control valve 34 is closed, there is an advantage that no shock is applied when the supercharger 33 is started.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to maintain low fuel consumption and prevent the generation of black smoke during high loads.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing one embodiment of the present invention, Fig. 2 is a flowchart of a program for supercharger drive control, Fig. 3 is a flowchart of a program for control valve opening/closing control, and Fig. 4 is an oxygen concentration diagram. FIG. 5 is a graph showing the relationship between control valve opening and supercharging pressure. 30... Intake passage, 31... First passage, 3
2... Second passage, 33... Mechanical supercharger (supercharger), 34
...Control valve, 42...Exhaust passage, 43
...Oxygen concentration sensor, 51...Electronic control unit.

Claims (1)

[Claims] 1. A control device for a mechanical supercharger provided in a first passage formed in the middle of an intake passage of a diesel engine, comprising: a drive mechanism that operates the mechanical supercharger when an engine load is equal to or higher than a predetermined value; A control valve provided in a second passage that extends between the upstream and downstream sides of the first passage, an oxygen concentration sensor provided in the exhaust passage that detects the oxygen concentration in the exhaust gas, and a mechanical supercharger. A control device for a mechanical supercharger, comprising: control means for adjusting the opening degree of the control valve according to the oxygen concentration during operation.