JP2006299833A - Fuel injection quantity control device in diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine the maximum injection quantity limit values adapted to a nontransitional state and a transitional state, respectively. <P>SOLUTION: A control computer C stores a map indicated by a graph in Fig. 1(b). A curve h1 expresses a part of the map set in response to the transitional state, and a curve h2 expresses a part of the map set in response to the nontransitional state. The map being aggregation of a large number of curves including the curve h1 is first maximum injection quantity limit value information on a maximum injection quantity limit value predetermined in response to an oxygen quantity-related value and the transitional state. The map being aggregation of a large number of curves including the curve h2 is second maximum injection quantity limit value information on a maximum injection quantity limit value predetermined in response to the oxygen quantity-related value and the nontransitional state. The control computer C specifies a maximum injection quantity limit value by using such a map. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection amount control device for a diesel engine.

  In the injection amount control device in the diesel engine disclosed in Patent Document 1, a plurality of maximum injection amount control patterns are prepared, and one of the plurality of maximum injection amount control patterns is selected according to the shift position of the transmission, Maximum injection amount control is performed according to the selected maximum injection amount control pattern.

In the fuel injection amount control device for a diesel engine disclosed in Patent Document 2, the first calculation means for calculating the intake air amount when the diesel engine is in a steady operation state, and the intake when the diesel engine is in an acceleration operation state Second calculating means for calculating the amount of air. The first calculation means calculates the intake air amount in the steady operation state based on the intake air amount detected by the intake air amount detection means (specifically, an air flow meter). The second calculating means calculates the intake air amount in the acceleration operation state based on the throttle opening detected by the throttle opening detecting means and the engine speed detected by the engine speed detecting means. To do. Further, a traveling state detecting means for detecting whether or not the diesel engine is switched from the steady operating state to the accelerated operating state is provided, and when the traveling state detecting means detects this switching, it is detected by the first calculating means. The larger one of the intake air amount and the intake air amount detected by the second calculating means is selected. Then, the fuel injection amount is determined based on the selected intake air amount and the detected engine speed. That is, at the time of transition from the steady operation state to the acceleration operation state, the larger one of the intake air amounts calculated by the pair of calculating means is adopted, and the fuel injection of the injection amount corresponding to the intake air amount of the larger value is adopted. Is done.
Japanese Utility Model Publication No. 1-1118143 JP-A-4-365934

  Increasing the fuel injection amount is advantageous for increasing torque, but black smoke is likely to be generated when the fuel injection amount is excessive. The limit value of the maximum fuel injection amount is an important factor in considering the avoidance of black smoke generation and higher torque.

  The limit value of the maximum fuel injection amount depends on the amount of oxygen in the combustion chamber. The amount of oxygen in the combustion chamber can be grasped, for example, by detecting the intake pressure, but there is a response delay of intake during transition from the steady operation state to the acceleration operation state (transient state), and at the same engine speed and load. The intake pressure is lower than the steady state. In addition, at high altitudes where the atmospheric pressure is low, the intake pressure is low even in steady operation. Therefore, even when the engine speed and load are the same, the limit value of the maximum fuel injection amount may be different when black smoke generation and high torque are taken into consideration.

  Also, different fuel injection control may be performed in the normal operation state and the acceleration operation state, for example, by varying the advance timing of the injection timing. In this case, black smoke is generated even with the same intake pressure (oxygen amount). There are cases where the limit value of the maximum injection amount is different in consideration of avoidance of occurrence and higher torque.

However, in the control device disclosed in Patent Document 1, there is no idea to determine the maximum injection amount limit value that is suitable for the steady operation state and the transient state even with the same intake pressure (oxygen amount).
In the control device disclosed in Patent Document 2, in a transient state, the larger one of the intake air amounts calculated by the pair of calculating means is adopted, and fuel injection is performed with an injection amount corresponding to the adopted intake air amount. However, there is no idea of determining the maximum injection amount limit value adapted to the steady operation state and the transient state even with the same intake pressure (oxygen amount).

  An object of the present invention is to make it possible to determine a maximum injection amount limit value adapted to each of a non-transient state and a transient state.

  According to the first aspect of the present invention, the transient state detecting means for detecting whether the engine rotational state is the transient state or the non-transient state, and the value related to the oxygen amount of the gas sucked into the cylinder and the transient state are previously stored. First determined maximum injection amount limit value information, second maximum injection amount limit value information determined in advance corresponding to a value related to the oxygen amount of gas sucked into the cylinder and a non-transient state, And when the transient state detecting means detects that it is in a transient state, the maximum injection amount limit value is specified using the first maximum injection amount limit value information, and the transient state detecting means Is detected as a non-transient state, the limit value specifying means for specifying the maximum injection quantity limit value using the second maximum injection quantity limit value information, and the maximum specified by the limit value specifying means Fuel that causes fuel injection with an injection amount less than the injection amount limit value Characterized in that a morphism control means.

  The limit value specifying means specifies the maximum injection amount limit value using the first maximum injection amount limit value information when in the transient state, and the second maximum injection amount limit value when in the non-transient state. The maximum injection amount limit value is specified using the information. The first maximum injection amount limit value information is information on the maximum injection amount limit value determined in advance corresponding to the oxygen amount related value and the transient state, and the maximum injection amount limit specified in the transient state. The value is a limit value adapted to the transient state. The second maximum injection amount limit value information is information on the maximum injection amount limit value determined in advance corresponding to the oxygen amount related value and the non-transient state, and the maximum injection specified in the non-transient state. The quantity limit value is a limit value adapted to a non-transient state. That is, the fuel injection is performed in accordance with the maximum injection amount limit value adapted to each of the non-transient state and the transient state.

  In a preferred example, oxygen amount related value detecting means for detecting an oxygen amount related value is provided, and the first maximum injection amount limit value information includes a first maximum injection amount limit value calculation having an oxygen amount related value correction coefficient. The second maximum injection amount limit value information is a second maximum injection amount limit value calculation formula having an oxygen amount related value correction coefficient, and the transient state detecting means detects that it is in a transient state. In this case, the limit value specifying unit specifies the oxygen amount related value correction coefficient in the first maximum injection amount limit value information based on the oxygen amount related value detected by the oxygen amount related value detecting unit. When the transient state detecting means detects that the state is a non-transient state, the limit value specifying means uses the oxygen amount related value correction coefficient in the second maximum injection amount limit value information as the oxygen amount related value. The amount of oxygen detected by the detection means It identified based on continuous values.

The determination of the maximum injection amount limit value by specifying the oxygen amount related value correction coefficient is simple in determining the maximum injection amount limit value adapted to each of the non-transient state and the transient state.
In a preferred example, the oxygen amount related value detecting means is an intake pressure detecting means for detecting an intake pressure.

The intake pressure detecting means is suitable as means for detecting the oxygen amount related value with high accuracy.
In a preferred example, the diesel engine performs pilot injection prior to main injection. In a preferred example, the fuel injection control means controls the fuel injection amount by changing a pilot injection period in pilot injection. In a preferred example, the fuel injection control means controls the fuel injection amount by changing the pilot injection start timing in the pilot injection.

  Pilot injection is advantageous for improving fuel consumption and reducing combustion noise.

  The present invention has an excellent effect that the maximum injection amount limit value adapted to each of the non-transient state and the transient state can be determined.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1A, a diesel engine 10 mounted on a vehicle includes a plurality of cylinders 11, and an electromagnetically driven fuel injection nozzle 13 is attached to each cylinder 11 on a cylinder head 12. Yes. The fuel injection nozzle 13 injects fuel (light oil) into each cylinder 11.

  An intake manifold 14 is connected to the cylinder head 12. The intake manifold 14 is connected to an intake passage 15, and the intake passage 15 is connected to an air cleaner 17. A throttle valve 18 is provided in the intake passage 15. The throttle valve 18 is for adjusting the intake air flow that is drawn into the intake manifold 14 via the air cleaner 17 and the intake passage 15. The opening degree of the throttle valve 18 is adjusted according to the engine rotation and the load state.

  The depression angle of the accelerator pedal is detected by an accelerator opening detector 19. A crank angle rotation angle (crank angle) of a crankshaft (not shown) is detected by a crank angle detector 20. The depression angle (accelerator opening) detection information detected by the accelerator opening detector 19 and the crank angle detection information detected by the crank angle detector 20 are sent to the control computer C. The control computer C obtains the engine speed from the time change of the crank angle detected by the crank angle detector 20. The control computer C obtains the engine load F from the accelerator opening detected by the accelerator opening detector 19.

  A compressor portion 161 of the supercharger 16 is interposed in the intake passage 15. The supercharger 16 is a known variable nozzle turbocharger that is operated by an exhaust gas flow. The throttle valve 18 is provided in the intake passage 15 between the supercharger 16 and the intake manifold 14. The intake air drawn into the intake passage 15 and sent out from the compressor unit 161 of the supercharger 16 flows into the intake manifold 14 and is supplied to the cylinder 11.

  An exhaust manifold 21 is connected to the cylinder head 12. Exhaust gas generated in the cylinder 11 is discharged to the exhaust manifold 21. The exhaust manifold 21 is connected to the exhaust passage 22 via the turbine section 162 of the supercharger 16.

  The intake manifold 14 is provided with an intake air temperature detector 23 and a pressure detector 24. The pressure detector 24 detects the pressure (intake pressure) in the intake manifold 14. Information on the intake pressure detected by the pressure detector 24 is sent to the control computer C.

  The control computer C calculates the maximum injection amount limit value Q1 or the maximum injection amount limit value based on the following first maximum injection amount limit value calculation formula [1] or second maximum injection amount limit value calculation formula [2]. Q2 is calculated.

Q1 = H1 × T × Qo [1]
Q2 = H2 × T × Qo [2]
Qo is the maximum injection amount limit value at standard atmospheric pressure (= 1 atmospheric pressure), H1 and H2 are intake pressure correction coefficients, and T is the intake air temperature.

  The control computer C stores a map shown in a graph in FIG. A curve h1 in the graph of FIG. 1B represents a part of a map (hereinafter referred to as a map M1) of the intake pressure correction coefficient H1 set corresponding to the intake pressure and the engine speed in the transient state. A curve h2 represents a part of a map (hereinafter referred to as map M2) of the intake pressure correction coefficient H2 set corresponding to the intake pressure and the engine speed in the non-transient state. That is, the map M1 is a set of curves set for each engine speed so as to represent the relationship between the intake pressure in the transient state and the intake pressure correction coefficient H1, and the map M2 is the intake pressure in the non-transient state. A set of curves set for each engine speed so as to represent the relationship with the intake pressure correction coefficient H2. A map M1 which is a set of a plurality of curves including the curve h1 and a map M2 which is a set of a plurality of curves including the curve h2 are intake pressure correction coefficient information determined in advance according to the intake pressure.

  The stored intake pressure correction coefficient is set to increase as the intake pressure increases. This is because the amount of oxygen increases as the intake pressure increases. The stored intake pressure correction coefficient is set to increase as the engine speed increases.

  FIG. 2 is a flowchart showing an intake pressure correction coefficient specifying program executed by the control computer C. The intake pressure correction coefficient specifying control is repeated at a predetermined control cycle. In the present embodiment, the main injection is performed after the pilot injection is performed. Hereinafter, the intake pressure correction coefficient specifying control by the control computer C will be described.

  The control computer C captures each detection information of the engine speed Nx, the accelerator opening Kx, the intake pressure Px, and the engine load F (step S1). Based on the detected engine speed Nx and the detected engine load F, the control computer C determines a target intake pressure Po in a steady operation state from a preset map (step S2). The control computer C controls the vane opening in the turbine unit 162 of the supercharger 16 so that the intake pressure Px detected by the pressure detector 24 becomes the target intake pressure Po.

  The control computer C compares the detected accelerator opening Kx with a preset accelerator opening Ko (step S3). When the detected accelerator opening Kx is equal to or greater than the preset accelerator opening Ko (YES in step S3), the control computer C determines that the difference between the detected intake pressure Px and the target intake pressure Po | Px−Po | Is compared with a preset reference value α (step S4).

  If the difference | Px−Po | is equal to or larger than the reference value α (YES in step S4), the control computer C specifies the intake pressure correction coefficient H1 using the engine speed Nx, the intake pressure Px, and the map M1. (Step S5). Then, the control computer C calculates and specifies the maximum injection amount limit value Q1 using the specified intake pressure correction coefficient H1 and the calculation formula [1] (step S6). When the accelerator opening degree Kx is equal to or larger than the preset accelerator opening degree Ko and the difference | Px−Po | is equal to or larger than the reference value α, it is determined that the engine rotational state is a transient state.

  If accelerator opening Kx does not reach accelerator opening Ko (NO in step S3) or if difference | Px−Po | does not reach reference value α (NO in step S4), the engine rotation state is non-transient. It is determined that it is in a state. In the non-transient state, the control computer C specifies the intake pressure correction coefficient H2 using the engine speed Nx, the intake pressure Px, and the map M2 (step S7). Then, the control computer C calculates and specifies the maximum injection amount limit value Q2 using the specified intake pressure correction coefficient H2 and the calculation formula [2] (step S8).

  After the process of step S8, the control computer C specifies basic fuel injection in the steady operation state based on the detected engine speed Nx (step S9). Basic fuel injection refers to basic main injection start timing and basic main injection period (main injection amount) in main injection, basic pilot injection start timing and basic pilot injection period (pilot injection amount) in pilot injection performed prior to main injection. It is a fuel injection determined by. The basic fuel injection in the steady operation state is specified such that the fuel injection amount is equal to or less than the specified maximum injection amount limit value Q2.

  After the process of step S6, the control computer C specifies the basic fuel injection in the steady operation state based on the detected engine speed Nx (step S10). Based on the difference (Px−Po) between the detected intake pressure Px and the target intake pressure Po, the control computer C performs basic fuel injection (basic main injection start timing and basic main injection period in main injection, pilot injection) Basic pilot injection start timing and basic pilot injection period) are corrected (step S11). The fuel injection in the transient state is specified such that the fuel injection amount is equal to or less than the specified maximum injection amount limit value Q1. The main injection start timing is, for example, a timing after the piston (not shown) in the cylinder 11 reaches the compression top dead center. The pilot injection start timing is the timing before the piston in the cylinder 11 reaches the compression top dead center.

In the present embodiment, the correction of the basic fuel injection in step S11 is a correction that increases the pilot injection period (pilot injection amount) by advancing the pilot injection start timing.
Then, the control computer C starts the pilot injection at the determined pilot injection start timing and causes the fuel injection to be performed by the determined pilot injection amount. After the pilot injection is completed, the control computer C starts main injection at the determined main injection start timing and causes fuel injection by the determined main injection amount. In this way, the advance angle control is performed to increase the maximum fuel injection amount in consideration of avoiding the generation of black smoke and increasing the torque. In addition, when the maximum fuel injection amount is determined by the intake pressure in the same manner in both the steady operation state and the transient operation state as in the past, the advance angle control is performed during the transient operation state so that more fuel is injected than in the normal operation state. Although a large amount of fuel was not injected in spite of the state, the acceleration response can be improved by widening the maximum fuel injection limit value in the transient operation state as in this embodiment.

  The accelerator opening detector 19 is an engine load detection means. The crank angle detector 20 and the control computer C constitute engine speed detecting means for detecting the engine speed. The pressure detector 24 is intake pressure detection means as oxygen amount related value detection means. The control computer C, together with the pressure detector 24 and the engine speed detecting means, constitutes a transient state detecting means for detecting whether the engine rotational state is a transient state or a non-transient state. Further, the control computer C specifies the maximum injection amount limit value by using the first maximum injection amount limit value information (calculation formula [1]) in the transient state, and in the non-transient state. This is limit value specifying means for specifying the maximum injection amount limit value using the second maximum injection amount limit value information (calculation formula [2]). Further, the control computer C is a fuel injection control means for performing fuel injection in a range that is equal to or less than the specified maximum injection amount limit value.

In the first embodiment, the following effects can be obtained.
(1-1) The control computer C specifies the maximum injection amount limit value Q1 using the calculation formula [1] when in the transient state, and uses the calculation formula [2] when in the non-transient state. Thus, the maximum injection amount limit value Q2 is specified. The calculation formula [1] is information on the maximum injection amount limit value Q1 (first maximum injection amount limit value information) determined in advance corresponding to the oxygen amount related value and the transient state, and is in the transient state. The maximum injection amount limit value Q1 specified in (1) is a limit value adapted to a transient state. The calculation formula [2] is information on the maximum injection amount limit value Q2 determined in advance corresponding to the oxygen amount related value and the transient state (second maximum injection amount limit value information), and is in a non-transient state. The maximum injection amount limit value Q2 specified in this case is a limit value adapted to a non-transient state. That is, the fuel injection is performed in accordance with the maximum injection amount limit value adapted to each of the non-transient state and the transient state. That is, fuel injection effective for avoiding black smoke generation and increasing torque can be performed after specifying the maximum injection amount limit value adapted to each of the non-transient state and the transient state.

  (1-2) In the transient state, the control computer C calculates the intake pressure correction coefficient (oxygen amount related value correction coefficient) in the calculation formula [1] based on the intake pressure detected by the pressure detector 24. Identify. When detecting the non-transient state, the control computer C calculates the intake pressure correction coefficient (oxygen amount related value correction coefficient) in the calculation formula [2] based on the intake pressure detected by the pressure detector 24. Identify. The determination of the maximum injection amount limit value by specifying the intake pressure correction coefficient is simple in determining the maximum injection amount limit value adapted to each of the non-transient state and the transient state.

(1-3) The pressure detector 24 that detects a value (intake pressure) related to the oxygen amount of the gas (air) sucked into the cylinder 11 is suitable as means for detecting the oxygen amount with high accuracy.
(1-4) In the present invention, pilot injection is performed prior to main injection. A small amount of fuel from the pilot injection prior to the main injection is not burned immediately, but is gently burned with the fuel injected at the beginning of the main injection. Thereby, combustion with low combustion pressure and combustion temperature is performed, and the effect of improving fuel consumption and reducing combustion noise is obtained.

  (1-5) In the transient state, the control computer C corrects the pilot injection period (pilot injection amount) by increasing the pilot injection start timing. Control for increasing the fuel injection amount by advancing the pilot injection start timing is suitable for increasing the torque while improving fuel efficiency and reducing combustion noise.

In the present invention, the following embodiments are also possible.
(1) An air flow meter that detects the flow rate of intake air flowing through the intake passage may be used as the oxygen amount related value detection means.

(2) The present invention may be applied to a fuel injection amount control device that does not perform pilot injection.
(3) The present invention may be applied to a diesel engine not provided with the supercharger 16.
(4) The determination method of the transient state is not particularly limited to the embodiment. For example, the detected accelerator opening is greater than or equal to the accelerator opening Ko, and the change amount per unit time of the detected accelerator opening is greater than or equal to the predetermined amount. In some cases, it may be determined as a transient state.

  (5) As the first maximum injection amount limit value information, a calculation formula in which the intake air temperature correction coefficient in the first maximum injection amount limit value calculation formula [1] is fixed to 1, and the second maximum injection amount limit value is used. As information, a calculation formula in which the intake air temperature correction coefficient in the second maximum injection amount limit value calculation formula [2] is fixed to 1 may be used.

1 shows an embodiment, and (a) is a schematic configuration diagram of a diesel engine and a fuel injection amount control device. (B) is a graph showing a map showing the relationship between the intake pressure and the intake pressure correction coefficient in the non-transient state, and a map showing the relationship between the intake pressure and the intake pressure correction coefficient in the transient state. The flowchart showing an intake pressure correction coefficient specific program.

Explanation of symbols

  10 ... Diesel engine. 11 ... cylinder. 20 A crank angle detector which constitutes engine speed detecting means together with the control computer C. 24 A pressure detector which is an intake pressure detection means as an oxygen amount related value detection means. C: A control computer that constitutes a transient state detection means together with the pressure detector 24 and the engine speed detection means, and serves as a limit value specifying means and a fuel injection control means.

Claims (6)

Transient state detecting means for detecting whether the engine rotation state is a transient state or a non-transient state;
First maximum injection amount limit value information determined in advance corresponding to a value related to the oxygen amount of the gas sucked into the cylinder and a transient state, and a value related to the oxygen amount of the gas sucked into the cylinder, The second maximum injection amount limit value information determined in advance corresponding to the non-transient state is stored, and when the transient state detecting means detects the transient state, the first maximum When the maximum injection amount limit value is specified using the injection amount limit value information and the transient state detecting means detects that the non-transient state is detected, the maximum injection amount is determined using the second maximum injection amount limit value information. Limit value specifying means for specifying the quantity limit value;
A fuel injection amount control device in a diesel engine, comprising: fuel injection control means for performing fuel injection with an injection amount equal to or less than a maximum injection amount limit value specified by the limit value specifying means.   An oxygen amount related value detecting means for detecting a value related to the oxygen amount of the gas sucked into the cylinder is provided, and the first maximum injection amount limit value information includes a first maximum injection having an oxygen amount related value correction coefficient. The second maximum injection amount limit value information is a second maximum injection amount limit value calculation formula having an oxygen amount related value correction coefficient, and the transient state detecting means is in a transient state. If it is detected, the limit value specifying means sets the oxygen amount related value correction coefficient in the first maximum injection amount limit value information to the oxygen amount related value detected by the oxygen amount related value detecting means. And when the transient state detecting means detects that the transient state detecting means is in a non-transient state, the limit value specifying means calculates the oxygen amount related value correction coefficient in the second maximum injection amount limit value information. Detected by oxygen level related value detection means Fuel injection quantity control device in a diesel engine according to claim 1 to identify on the basis of the amount of oxygen-related value.   The fuel injection amount control device for a diesel engine according to claim 2, wherein the oxygen amount related value detection means is intake pressure detection means for detecting intake pressure.   The fuel injection amount control device for a diesel engine according to any one of claims 1 to 3, wherein the diesel engine performs pilot injection prior to main injection.   The fuel injection amount control device for a diesel engine according to claim 4, wherein the fuel injection control means controls a fuel injection amount by changing a pilot injection period in pilot injection.   The fuel injection amount control device for a diesel engine according to claim 5, wherein the fuel injection control means controls a fuel injection amount by changing a pilot injection start timing in pilot injection.

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