JP2011052587A - Control device for air bypass valve of diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diesel engine having a turbocharger which prevents generation of a surge sound or flow-back sound with backflow of supercharging air. <P>SOLUTION: The diesel engine includes: an air bypass valve 51 disposed on an air bypass passage 5 connecting the upstream with the downstream of a compressor 21 of the turbocharger 2; the air bypass valve 51 opened by turning off an accelerator. Time for opening the air bypass valve 51 takes longer and the opening thereof increases according to the increase in the change amount of the accelerator opening at turning off the accelerator. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an air bypass valve control device for a diesel engine having a turbocharger.

  In an engine having a turbocharger, supercharged air that is not required when the accelerator is off may flow backward toward the compressor of the turbocharger due to pressure reflection. The supercharged air that has flowed back is not preferable because it generates a surge noise in the compressor and blows back noise in the air cleaner.

  In order to prevent the occurrence of such abnormal noise, it is known to provide an air bypass passage that connects the upstream side and the downstream side of the compressor. In a gasoline engine, an air bypass passage can be controlled to open and close by providing a mechanical air bypass valve on the air bypass passage that is operated by a differential pressure between the upstream and downstream of the throttle valve (for example, , See the following patent document). When the throttle valve is suddenly closed and the pressure upstream of the throttle valve is increased, the air bypass valve is opened to open the air bypass passage, the supercharging pressure is suppressed, and the generation of abnormal noise is avoided.

  However, in diesel engines, it is customary not to install a throttle valve in the intake system. Therefore, opening / closing control of the air bypass passage employing the conventional air bypass valve cannot be performed.

JP-A-11-264321 Japanese Patent Laid-Open No. 11-324689

  An object of the present invention, which has been made by paying attention to the above problem for the first time, is to prevent the occurrence of a surge noise and a blowback sound accompanying a backflow of supercharged air in a diesel engine having a turbocharger.

  The present invention controls a diesel engine having a turbocharger, and includes an air bypass passage that communicates an upstream side and a downstream side of a compressor of a turbocharger provided in an intake system, and the air bypass passage on the air bypass passage. An air bypass valve that opens and closes the air bypass passage, and a control device that opens the air bypass valve for a predetermined time or a predetermined opening when the accelerator is off, wherein the value of the predetermined time or the predetermined opening is determined by the accelerator The diesel engine air bypass valve control device is configured to increase the amount of change in the accelerator opening when the engine is off. Here, “accelerator off” refers to reducing the amount of depression of the accelerator pedal that the driver has stepped on until then, or stopping the depression completely. The amount of change in the accelerator opening is the difference between the pedal depression amount immediately before the accelerator is off and the pedal depression amount immediately after the accelerator is off, or the amount of change in the pedal depression amount per unit time.

  With such a configuration, the pressure downstream of the compressor in the operation region where pressure reflection may occur can be released to the upstream of the compressor appropriately through the air bypass passage. And it becomes possible to prevent generation | occurrence | production of the surge sound and blow-back sound accompanying a backflow of supercharging air.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the surge sound and blowback sound accompanying a backflow of supercharged air can be prevented in the diesel engine which has a turbocharger.

The typical whole block diagram of the diesel engine in one Embodiment of this invention. The flowchart which shows the procedure of the process which the control apparatus of the embodiment performs.

  An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the structure of the diesel engine 1 of this embodiment which has the turbocharger 2 and the air bypass passage 5 is shown typically. The diesel engine 1 includes a plurality of cylinders 7 (only one cylinder is shown in the figure), an injector 73 that injects fuel into each cylinder 7, and an intake system for supplying intake air to each cylinder 7. A path 3, an exhaust system path 4 for discharging exhaust gas from each cylinder 7, and a turbocharger 2 that is a set of a drive turbine 22 and a compressor 21 are provided.

  The intake system path 3 takes in air from the outside and guides it to the intake port 71 of the cylinder 7. On the intake path 3, an air cleaner 31, a compressor 21, an intercooler 32, and a surge tank 33 are arranged in this order from the upstream.

  The exhaust system path 4 guides exhaust gas generated as a result of burning fuel in the cylinder 7 from the exhaust port 72 of the cylinder 7 to the outside. A drive turbine 22 is disposed on the exhaust system path 4.

  The turbocharger 2 is configured such that the drive turbine 22 and the compressor 21 are connected coaxially and interlocked. Then, the drive turbine 22 is rotationally driven using the energy of the exhaust gas, and the compressor 21 is pumped by using the rotational force, whereby the intake air is pressurized and compressed, that is, supercharged and sent to the cylinder 7. .

  Therefore, in the present embodiment, the air bypass passage 5 that communicates the upstream side and the downstream side of the compressor 21 is provided, and the air bypass valve 51 is provided on the air bypass passage 5.

  The air bypass valve 51 is, for example, a solenoid valve that can be opened / closed by inputting a control signal e. The air bypass valve 51 is operated by the ECU 6 serving as a control device.

  The ECU 6 is a microcomputer system having a CPU 61, a memory 62, an input interface 63, an output interface 64, and the like. The input interface 63 includes a supercharging pressure signal a output from a supercharging pressure sensor 81 that detects supercharging pressure, a rotational speed signal b output from a rotational speed sensor 82 that detects engine rotational speed, and an accelerator opening, An accelerator opening signal c and the like output from an accelerator sensor 83 that detects the amount of depression of the accelerator pedal are input. From the output interface 64, a fuel injection signal d is output to the fuel injection valve 3, a valve opening signal e is output to the air bypass valve 51, and the like.

  The CPU 61 interprets and executes a program stored in advance in the memory 62 and controls the operation of the diesel engine 1. The CPU 61 acquires various information a, b, and c necessary for operation control of the diesel engine 1 through the input interface 63, and calculates the fuel injection amount, the valve opening time of the air bypass valve 51, and the like based on the information. Various control signals d and e corresponding to the calculation result are applied via the output interface 64.

  In this embodiment, the ECU 6 determines the required fuel injection amount, in other words, the required engine load, based on the engine speed, the accelerator pedal depression amount, and other various conditions (cooling water temperature, etc.). Calculate. The required load calculation logic may be the same as in known engine control. In addition, in an operation region in which pressure reflection due to excessive supercharging pressure may occur, the valve opening signal e is supplied to the air bypass valve 51 to open it, and the pressure downstream of the compressor is changed to the air bypass passage 5. To escape upstream of the compressor.

  The time during which the valve opening signal e is energized to the air bypass valve 51, that is, the length of the valve opening time of the air bypass valve 51 depends on the amount of change in the accelerator opening when the accelerator is off. Specifically, the valve opening time of the air bypass valve 51 is lengthened in proportion to the amount of change in the accelerator opening. The change amount of the accelerator opening is the difference between the pedal depression amount immediately before the accelerator off and the pedal depression amount immediately after the accelerator off, or the change amount per unit time of the pedal depression amount obtained through the accelerator sensor 83. It is.

However, if the air bypass valve 51 is operated only on the basis of the change amount of the accelerator opening, the air bypass valve 51 is opened even at a low supercharging pressure at which no surge noise or blowback noise occurs. On the other hand, the possibility of a decrease in drivability cannot be denied. Therefore, in this embodiment,
1) Supercharging pressure ≧ A
2) Engine speed ≥ B
3) Required load ≥ C
Only when all the conditions are satisfied, the air bypass valve 51 is opened. The determination value A is related to the fact that the supercharging pressure is high, and the determination values B and C are related to the fact that the current operating range of the diesel engine 1 is in the range above the middle-rotation load range. Is. Each of these determination values A, B, and C is stored in advance in the memory 62 as map data.

  FIG. 2 shows a procedure example of processing executed by the ECU 6 according to the program. The ECU 6 observes the depression amount of the accelerator pedal via the accelerator sensor 83, and when the accelerator-off occurs when the depression amount becomes a predetermined threshold value (this threshold value is 0 or a value close to 0). (Step S1), whether the supercharging pressure obtained via the supercharging pressure sensor 81 is equal to or higher than the judgment value A (Step S2), or the engine speed obtained via the rotational speed sensor 82 is equal to or higher than the judgment value B (Step S3) and whether the required load at that time is equal to or greater than the determination value C (Step S4). If both conditions are satisfied, the valve opening time corresponding to the amount of change in the accelerator opening is determined (step S5), and the air bypass valve 51 is energized for the determined valve opening time. Is opened (step S6).

  According to the present embodiment, the air bypass passage 5 that communicates the upstream side and the downstream side of the compressor 21 of the turbocharger 2 provided in the intake system 3, and the air bypass passage 5 that is interposed on the air bypass passage 5 is opened and closed. And the control device 6 that opens the air bypass valve 51 for a predetermined time when the accelerator is off, and the value of the predetermined time is set to be larger as the change amount of the accelerator opening when the accelerator is off. Since the control device for the air bypass valve 51 to be increased is configured, the pressure downstream of the compressor in the operation region where pressure reflection may occur can be appropriately released to the upstream of the compressor via the air bypass passage 5. And it becomes possible to prevent generation | occurrence | production of the surge sound and blow-back sound accompanying a backflow of supercharging air.

  The present invention is not limited to the embodiment described in detail above. In particular, a flow control valve capable of PWM control of the valve opening degree may be employed as the air bypass valve 51. In this case, the ECU 6 increases the opening degree of the air bypass valve 51 (DUTY ratio of the valve opening signal e) as the change amount of the accelerator opening degree when the accelerator is off is larger.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be used to control a diesel engine mounted on a vehicle or the like.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Turbocharger 21 ... Compressor 5 ... Air bypass passage 51 ... Air bypass valve 6 ... Control apparatus (ECU)

Claims (1)

Controlling a diesel engine with a turbocharger,
An air bypass passage communicating the upstream side and the downstream side of the compressor of the turbocharger provided in the intake system;
An air bypass valve interposed on the air bypass passage to open and close the air bypass passage;
A control device for opening the air bypass valve for a predetermined time or a predetermined opening when the accelerator is off,
An air bypass valve control device for a diesel engine, wherein the value of the predetermined time or the predetermined opening is increased as the amount of change in the accelerator opening when the accelerator is off is increased.

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