JP2012211523A - Fuel injection control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly perform gas fuel injection control at engine start-up, and to thereby avoid destabilization of combustion, deterioration of emission, degradation of fuel consumed amount, and the like.SOLUTION: A fuel injection control system includes: a first control device for performing energization control of a liquid fuel injection valve; and a second control device for performing energization control of a gas fuel injection valve depending on an energization pulse for the liquid fuel injection valve that is input from the first control valve, and the second control device calculates a start time gas fuel injection amount and start time gas fuel injection timing at engine start-up, and performs energization control of the gas fuel injection valve depending on the calculation results.

Description

 The present invention relates to a fuel injection control system.

Patent Document 1 below discloses a technique for setting an increase in gasoline fuel immediately after cranking to an appropriate value according to a change in engine temperature at the time of engine start.
Further, in Patent Document 2 below, as one form of a bi-fuel system, a gas fuel injection control device uses a gas fuel injection signal (a signal indicating a gasoline fuel injection amount) received from a gasoline fuel injection control device for gas fuel. There is disclosed a technique for calculating a gas fuel injection amount by multiplying a correction coefficient and performing energization control of the gas fuel injection valve in accordance with the calculation result.

Japanese Patent Publication No. 6-60581 JP 2009-133207 A

Gasoline fuel has a low evaporation rate and adheres to the wall surface of the intake port. Therefore, when starting the engine, it is necessary to inject a large amount of gasoline fuel until the wall surface of the intake port gets wet (see Patent Document 1). Does not have such a property, and it is not necessary to inject a large amount of gas fuel when starting the engine.
However, when a bi-fuel system that controls energization of the gas fuel injection valve in accordance with the gas fuel injection amount calculated from the gasoline fuel injection signal as described in Patent Document 2, for example, the engine is started with gas fuel. Sometimes a large amount of gas fuel is injected, which may lead to instability of combustion, deterioration of emissions, deterioration of fuel consumption, and the like.

   The present invention has been made in view of the above-described circumstances, and appropriately performs gaseous fuel injection control at the time of starting the engine, thereby avoiding instability of combustion, deterioration of emissions, deterioration of fuel consumption, and the like. An object of the present invention is to provide a fuel injection control system capable of this.

 In order to solve the above-described problems, in the present invention, as a first solving means related to a fuel injection control system, a first control device that performs energization control of a liquid fuel injection valve, and the input from the first control device. A fuel injection control system comprising: a second control device that performs energization control of the gaseous fuel injection valve in response to a pulse signal for energization of the liquid fuel injection valve, wherein the second control device is a gas at start-up when the engine is started A fuel injection amount and a start-time gaseous fuel injection timing are calculated, and energization control of the gaseous fuel injection valve is performed according to the calculation result.

 Further, in the present invention, as a second solving means related to the fuel injection control system, in the first solving means, the second control device is configured such that the engine speed becomes equal to or higher than a predetermined speed when the engine is started. The gas fuel injection valve is energized and controlled according to the calculation result of the starting gaseous fuel injection amount and the starting gaseous fuel injection timing until a condition that the number of fuel injections exceeds a predetermined number is satisfied. To do.

Further, in the present invention, as a third solving means relating to the fuel injection control system, in the second solving means, the second control device is configured such that the engine speed is equal to or higher than a predetermined speed and the fuel injection frequency is After the condition that the predetermined number of times has been exceeded, the normal gas fuel injection calculated by correcting the transition coefficient α that increases by a certain value each time the number of fuel injections increases, the start-up gas fuel injection amount SGF, and the liquid fuel injection amount is corrected. The final gaseous fuel injection amount GF is calculated based on the following equation (1) consisting of the amount NGF, and the energization control of the gaseous fuel injection valve is performed according to the calculation result.
GF = SGF × (1−α) + NGF × α (1)

  Further, in the present invention, as a fourth solving means relating to the fuel injection control system, in the third solving means, the second control device is configured such that the normal gas fuel injection is performed after the transition coefficient α exceeds 1. The gas fuel injection amount is controlled to be the final gaseous fuel injection amount and the rising timing of the energization pulse signal input from the first control device is used as the gaseous fuel injection timing. To do.

 In the fuel injection control system according to the present invention, the second control device calculates the starting gaseous fuel injection amount and the starting gaseous fuel injection timing when starting the engine, and performs energization control of the gaseous fuel injection valve according to the calculation result. Do. In other words, according to the present invention, the second control device does not relate to the pulse signal for energization of the liquid fuel injection valve input from the first control device when the engine is started (in other words, regardless of the liquid fuel injection amount). ) Since the starting gas fuel injection amount and the starting gas fuel injection timing are independently calculated and the energization control of the gas fuel injection valve is performed, the gas fuel injection control at the time of starting the engine can be appropriately performed. It is possible to avoid instability of combustion, deterioration of emission, deterioration of fuel consumption, and the like.

1 is a schematic configuration diagram of a fuel injection control system according to the present embodiment. It is an operation | movement flowchart at the time of the gas fuel injection mode of 2nd-ECU4. It is the flowchart (a) showing the calculation process of the injection quantity at the time of start, and the timing chart (b) showing the injection timing at the time of start. It shows how the gas fuel injection amount, the gasoline fuel injection amount, and the engine speed change with the passage of time from engine start (ignition switch 7 is turned on).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a fuel injection control system according to the present embodiment. This fuel injection control system is a bi-fuel system that selectively switches between liquid fuel (gasoline) and gaseous fuel (compressed natural gas) and supplies it to a single engine (not shown). The fuel supply system 2, 1st-ECU (Electronic Control Unit) 3, 2nd-ECU 4, fuel switch 5, battery 6, and ignition switch 7 are included.

 The liquid fuel supply system 1 includes a gasoline tank 11, a gasoline supply pipe 12, and a gasoline injector (liquid fuel injection valve) 13. The gasoline tank 11 is a corrosion-resistant container that stores gasoline fuel as liquid fuel, and incorporates a pump and a regulator (not shown) that sucks the gasoline fuel and sends it to the gasoline supply pipe 12.

 The gasoline supply pipe 12 is a pipe for delivering gasoline fuel from the gasoline tank 11 to the gasoline injector 13. The gasoline injector 13 is an electromagnetic valve (for example, a solenoid valve) attached to the intake pipe so that the injection port is exposed toward the intake port of the engine. The gasoline injector 13 receives a pulse signal for energizing the gasoline injector input from the 2nd-ECU 4. In response, gasoline fuel is injected from the injection port.

 The gaseous fuel supply system 2 includes a gas tank 21, a high pressure gas supply pipe 22, a shutoff valve 23, a regulator 24, a low pressure gas supply pipe 25, a gas injector (gaseous fuel injection valve) 26, a fuel pressure sensor 27, a fuel temperature sensor 28, and a relief. It consists of a valve 29.

 The gas tank 21 is a high pressure vessel filled with high-pressure compressed natural gas (CNG) as gaseous fuel. The high-pressure gas supply pipe 22 is a high-pressure pipe for delivering high-pressure gas fuel from the gas tank 21 to the regulator 24. The shut-off valve 23 is an electromagnetic valve inserted in the middle of the high-pressure gas supply pipe 22 and opens or closes according to a shut-off valve drive signal input from the 2nd-ECU 4.

 The regulator 24 is a pressure regulating valve disposed on the downstream side of the shut-off valve 23, and reduces the high-pressure gas fuel supplied from the gas tank 21 to a desired pressure when the shut-off valve 23 is opened to the low-pressure gas supply pipe 25. Send it out. The low-pressure gas supply pipe 25 is a low-pressure piping for delivering low-pressure gas fuel from the regulator 24 to the gas injector 26. The gas injector 26 is an electromagnetic valve attached to the intake pipe so that the injection port is exposed toward the intake port of the engine. The gas injector 26 injects gas fuel in accordance with a gas injector energization pulse signal input from the 2nd-ECU 4. Spray from mouth.

 The fuel pressure sensor 27 detects the internal pressure (gas fuel pressure) of the low-pressure gas supply pipe 25 and outputs a gas fuel pressure signal indicating the detection result to the 2nd-ECU 4. The fuel temperature sensor 28 detects the internal temperature (gas fuel temperature) of the low-pressure gas supply pipe 25 and outputs a gas fuel temperature signal indicating the detection result to the 2nd-ECU 4. The relief valve 29 is a safety valve inserted in a pipe branched from the low-pressure gas supply pipe 25. When the internal pressure of the low-pressure gas supply pipe 25 exceeds a set pressure, the relief valve 29 opens to discharge gas fuel to the outside. .

 The 1st-ECU 3 (first control device) calculates the gasoline fuel injection amount and the gasoline fuel injection timing based on various sensor signals input from various sensors (not shown) for detecting the engine state, Accordingly, a gasoline injector energization pulse signal is generated and output to the 2nd-ECU 4. Specifically, the pulse width of the gasoline energization pulse signal is set according to the gasoline fuel injection amount, and the rising timing of the gasoline energization pulse signal is set according to the gasoline fuel injection timing.

 The various sensor signals input to the 1st-ECU 3 include at least a crank pulse signal that takes a time for the crankshaft to rotate at a constant angle as one cycle, and a time for the piston to reach top dead center (TDC) as one cycle. A TDC pulse signal, an intake air temperature signal indicating the intake air temperature, an intake air pressure signal indicating the intake air pressure, a cooling water temperature signal indicating the cooling water temperature, and the like.

 The 1st-ECU 3 calculates the engine speed from the crank pulse signal, calculates the gasoline fuel injection amount based on the engine speed and the intake air temperature (or cooling water temperature), and further calculates the gasoline fuel injection timing from the gasoline fuel injection amount. (Crankshaft angle at which gasoline fuel should be injected) is calculated. Note that the method for calculating the gasoline fuel injection amount and the gasoline fuel injection timing is the same as the conventional method, and a detailed description thereof will be omitted.

 The 2nd-ECU 4 (second control device) includes various sensor signals input from various sensors that detect the engine state, a gas fuel pressure signal input from the fuel pressure sensor 27, and a gas input from the fuel temperature sensor 28. Based on the fuel temperature signal, the gasoline injector energization pulse signal input from the 1st-ECU 3, and the fuel selection signal input from the fuel changeover switch 5, the gasoline injector 13, the gas injector 26 and the shutoff valve 23 are controlled. .

 Specifically, when the 2nd-ECU 4 detects that gasoline fuel is selected based on the fuel selection signal input from the fuel changeover switch 5, the 2nd-ECU 4 enters the gasoline fuel injection mode and is input from the 1st-ECU 3. A pulse signal having the same pulse width and rising timing as the gasoline injector energization pulse signal, that is, a gasoline injector energization pulse signal is output to the gasoline injector 13.

 When the 2nd-ECU 4 detects that the gas fuel is selected based on the fuel selection signal input from the fuel changeover switch 5, the gas fuel injection mode is set and the shutoff valve 23 is opened to open the gas tank 21. The gas injector 26 starts to supply gas fuel and generates a gas injector energization pulse signal based on various sensor signals (including gas fuel pressure signal and gas fuel temperature signal) and a gasoline injector energization pulse signal to generate a gas injector 26. Output to. Details of the operation in the gas fuel injection mode will be described later.

 The fuel change-over switch 5 is a switch that enables the fuel to be changed by manual operation. The state of the switch, that is, whether gasoline fuel is selected as fuel used in the engine or whether gas fuel is selected. The fuel selection signal shown is output to the 2nd-ECU 4.

 The battery 6 is a secondary battery having a positive terminal connected to the 1st-ECU 3 and the 2nd-ECU 4 via an ignition switch 7 and a negative terminal connected to the vehicle body. The ignition switch 7 is a switch that allows the engine to be started manually. When the ignition switch 7 is turned on, a power supply voltage is supplied from the battery 6 to the 1st-ECU 3 and the 2nd-ECU 4 and a cell motor (not shown) to start the engine.

Next, the operation of the bi-fuel system configured as described above, particularly the operation in the gas fuel injection mode of the 2nd-ECU 4 that is a feature of the present embodiment will be described.
When the 2nd-ECU 4 detects that gas fuel is selected based on the fuel selection signal input from the fuel selector switch 5 when the engine is started, that is, when the ignition switch 7 is turned on, In this mode, the shutoff valve 23 is opened to start the supply of gas fuel from the gas tank 21, and gas fuel injection control is performed according to the flowchart shown in FIG.

  As shown in FIG. 2, the 2nd-ECU 4 first calculates a starting gas fuel injection amount (step S1). Specifically, the 2nd-ECU 4 calculates the starting gas fuel injection amount in accordance with the flowchart shown in FIG. As shown in FIG. 3 (a), the 2nd-ECU 4 presets the starting basic injection amount from the cylinder stroke volume of the engine and the valve timing so as to be approximately the stoichiometric air-fuel ratio with respect to the intake air amount (step). S1a).

  Subsequently, since the actually sucked air amount changes according to the engine speed, the 2nd-ECU 4 sets a rotational speed correction coefficient to be multiplied by the basic injection amount at the start time according to the engine speed. (Step S1b). The intake air pulsates due to the intake by the piston, and the charging efficiency changes due to the correlation between the engine speed and the pulsation cycle, and therefore corresponds to the change in the intake air amount according to the speed.

  Subsequently, the 2nd-ECU 4 searches the intake air temperature correction table for the intake air temperature correction coefficient to be multiplied by the starting basic injection amount according to the intake air temperature because the amount of air actually sucked changes according to the intake air temperature. (Step S1c). Note that the correction coefficient may be calculated using the cooling water temperature instead of the intake air temperature. Then, the 2nd-ECU 4 calculates the starting gas fuel injection amount by multiplying the starting basic injection amount by the rotation speed correction coefficient and the intake air temperature correction coefficient (step 1d).

  Returning to FIG. 2, the 2nd-ECU 4 calculates the starting gas fuel injection amount as described above, and then starts the starting gas fuel injection timing (the crankshaft angle at which the gas fuel is to be injected) from the starting gas fuel injection amount. Is calculated (step S2). As mentioned above, gasoline fuel has a low evaporation rate, so it is necessary to inject a large amount until the intake port wall gets wet when starting the engine. However, gas fuel does not have such properties and is equivalent to that during normal operation. The engine can be started with the amount of fuel (see FIG. 4). Therefore, as shown in FIG. 3 (b), the gasoline fuel start-up injection timing is set during the compression stroke, but the gas fuel start-up injection timing is set during the exhaust stroke as well as the ideal injection timing. Is done.

 Subsequently, the 2nd-ECU 4 receives various sensor signals input from various sensors that detect the engine state, a gas fuel pressure signal input from the fuel pressure sensor 27, and a gas fuel temperature signal input from the fuel temperature sensor 28. The normal gas fuel injection amount is calculated by multiplying the gasoline injector energization pulse signal input from the 1st-ECU 3 by the gas fuel correction coefficient (step S3).

  Subsequently, the 2nd-ECU 4 determines whether the engine speed is equal to or higher than the initial explosion speed (for example, 500 rpm) (step S4). If “No” (when cranking), the counter variable CINJAST is set to “ It is set to “0” (step S5). The counter variable CINJAST is a variable used for counting the number of fuel injections from the first explosion.

 Then, the 2nd-ECU 4 sets the starting gas fuel injection amount calculated in step S1 as a final gas fuel injection amount (step S6), and sets the starting gas fuel injection timing calculated in step S2. The final gas fuel injection timing is set (step S7), and gas fuel injection control, that is, energization control of the gas injector 26 is performed according to the gas fuel injection amount and gas fuel injection timing (step S8).

  Specifically, in step S8, the 2nd-ECU 4 grasps the stroke and piston position (crankshaft angle) of each cylinder based on the crank pulse signal, the TDC pulse signal, and the intake pressure, and the gas fuel injection timing arrives. At this time, a gas injector energization pulse signal having a pulse width corresponding to the gas fuel injection amount is output to the gas injector 26.

  On the other hand, if “Yes” in step S4 (when the engine speed is equal to or greater than the initial explosion speed), the 2nd-ECU 4 determines that the counter variable CINJAST, that is, the number of fuel injections from the initial explosion is a predetermined number (for example, “5 times”). It is determined whether it is larger than ")" (step S9). If “No” in this step S9, the 2nd-ECU 4 increments the counter variable CINJAST and proceeds to the process of step S6 described above (step S10).

  That is, until the second-ECU 4 determines “Yes” in step S9 (until the condition that the engine speed is equal to or higher than the predetermined speed and the number of fuel injections exceeds the predetermined number), the above-described step S1. The energization control of the gas injector 26 is performed according to the start-time gas fuel injection amount calculated in step S2 and the start-time gas fuel injection timing calculated in step S2 (period until the transition period in FIG. 4 is reached). See).

  On the other hand, if “Yes” in step S9 (when the condition that the engine speed is equal to or higher than the predetermined speed and the number of fuel injections exceeds the predetermined number), the 2nd-ECU 4 has a transition coefficient α of “1”. It is determined whether or not (step S11). The transition coefficient α is a coefficient that increases by a constant value (Δα) each time the number of fuel injections increases, and “0” is set as an initial value.

In the case of “Yes” in this step S11, the 2nd-ECU 4 uses the transition coefficient α, the starting gas fuel injection amount SGF calculated in step S1 and the normal gas fuel injection amount NGF calculated in step S3. Based on the following equation (1), the final gas fuel injection amount GF is calculated (step S12).
GF = SGF × (1−α) + NGF × α (1)

  Then, after calculating the gas fuel injection amount GF, the 2nd-ECU 4 adds a constant value (Δα) to the transition coefficient α (step S13), and the rise of the gasoline injector energization pulse signal input from the 1st-ECU 3 The timing is set as the gas fuel injection timing (step S14), and energization control of the gas injector 26 is performed according to the gas fuel injection amount calculated in step S12 and the gas fuel injection timing set in step S14 (step S8). .

  That is, in this case, the 2nd-ECU 4 synchronizes with the rising timing of the gasoline injector energizing pulse signal input from the 1st-ECU 3, and has a pulse width corresponding to the gas fuel injection amount calculated in step S12. An injector energization pulse signal is output to the gas injector 26.

  On the other hand, if “No” in step S11 (when the transition coefficient α exceeds “1”), the 2nd-ECU 4 uses the normal gas fuel injection amount calculated in step S3 as the final gas fuel injection amount. Then, the process proceeds to step S14 (step S15). That is, in this case, the 2nd-ECU 4 has a pulse width corresponding to the normal gas fuel injection amount calculated in step S3 in synchronization with the rising timing of the gasoline injector energization pulse signal input from the 1st-ECU 3. A gas injector energization pulse signal is output to the gas injector 26.

  Thus, in the period from when the condition that the engine speed is equal to or higher than the predetermined speed and the fuel injection count exceeds the predetermined count to when the transition coefficient α exceeds “1”, the above equation (1) is satisfied. Accordingly, the ratio of the starting gas fuel injection amount to the gas fuel injection amount gradually decreases, and the ratio of the normal gas fuel injection amount increases (see the transition period in FIG. 4). Then, after the transition coefficient α exceeds “1”, it is not necessary to use the above equation (1). Therefore, the energization control of the gas injector 26 is performed with the normal gas fuel injection amount as the final gas fuel injection amount. (See after the transition period in FIG. 4).

  As described above, according to this embodiment, the 2nd-ECU 4 is not related to the gasoline injector energization pulse signal input from the 1st-ECU 3 at the time of engine start (in other words, regardless of the gasoline fuel injection amount). Since the start-up gas fuel injection amount and the start-up gas fuel injection timing are independently calculated and the energization control of the gas injector 26 is performed, the gas fuel injection control at the engine start-up can be performed appropriately, and as a result, combustion It is possible to avoid the instability of fuel, the deterioration of emissions, the deterioration of fuel consumption, and the like.

  Although one embodiment of the present invention has been described above, this embodiment is merely an example, and it is needless to say that various details of the embodiment can be changed without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Liquid fuel supply system, 2 ... Gaseous fuel supply system, 3 ... 1st-ECU (1st control apparatus), 4 ... 2nd-ECU (2nd control apparatus), 5 ... Fuel switch, 6 ... Battery, 7 ... Ignition switch

Claims (4)

A first control device that performs energization control of the liquid fuel injection valve, and a second control device that performs energization control of the gaseous fuel injection valve in accordance with an energization pulse signal of the liquid fuel injection valve input from the first control device A fuel injection control system comprising:
The second control device calculates a starting gaseous fuel injection amount and a starting gaseous fuel injection timing when starting the engine, and performs energization control of the gaseous fuel injection valve according to the calculation result. Control system.   The second control device is configured to start the gas fuel injection amount and the start gas until the condition that the engine speed is equal to or higher than the predetermined speed and the number of fuel injections exceeds the predetermined number is satisfied. The fuel injection control system according to claim 1, wherein energization control of the gaseous fuel injection valve is performed according to a calculation result of fuel injection timing. The second control device has a transition coefficient α that increases by a constant value each time the number of fuel injections increases after the condition that the engine speed is equal to or higher than the predetermined number of revolutions and the number of fuel injections exceeds the predetermined number of times. The final gaseous fuel injection amount GF is calculated based on the following equation (1) consisting of the normal gaseous fuel injection amount NGF calculated by correcting the starting gaseous fuel injection amount SGF and the liquid fuel injection amount. The fuel injection control system according to claim 2, wherein energization control of the gaseous fuel injection valve is performed according to
GF = SGF × (1−α) + NGF × α (1)   The second control device sets the normal gaseous fuel injection amount as a final gaseous fuel injection amount after the transition coefficient α exceeds 1, and the energization pulse signal input from the first control device. 4. The fuel injection control system according to claim 3, wherein energization control of the gaseous fuel injection valve is performed using a rising timing of the gas as a gaseous fuel injection timing. 5.

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