JP5859842B2 - Fuel injection system - Google Patents

Description

 The present invention relates to a fuel injection system.

  Conventionally, as a technology for improving the fuel efficiency and environmental protection performance of a vehicle, there is a bi-fuel system that selectively switches between liquid fuel such as gasoline and gaseous fuel such as compressed natural gas (CNG) and supplies it to a single engine. Are known. In Patent Document 1 below, in such a bi-fuel system, at least one of the fuel injection amount correction, the intake air amount correction, and the ignition timing correction control is executed for the torque step and the fluctuation generated at the time of fuel switching. Techniques to avoid are disclosed.

JP 2004-211161 A

  In the above-described prior art, since air-fuel ratio feedback control is not performed at the time of fuel switching, air-fuel ratio over-rich or over-lean occurs at the time of fuel switching, which may reduce emission performance.

 The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a fuel injection system capable of avoiding a decrease in emission performance at the time of fuel switching.

 In order to achieve the above object, according to the present invention, as a first solving means related to the fuel injection system, the liquid fuel basic injection amount is calculated based on the engine operating state, and the actual calculation calculated from the output signal of the air-fuel ratio sensor is performed. A liquid that calculates the liquid fuel injection amount by multiplying the liquid fuel basic injection amount by an air-fuel ratio feedback correction coefficient for making the air-fuel ratio coincide with the target air-fuel ratio, and outputs a first drive signal according to the calculation result In a fuel injection system, comprising: a fuel injection control device; and a gas fuel injection control device that calculates a basic fuel fuel injection amount based on the first drive signal input from the liquid fuel injection control device during gas fuel operation. Based on the output signal of the air amount sensor and the first drive signal input from the liquid fuel injection control device, it is used for correcting the liquid fuel basic injection amount. The air-fuel ratio feedback correction coefficient is estimated, and the ratio of the air-fuel ratio feedback correction coefficient estimated during the liquid fuel operation and the gas fuel operation is calculated as the air-fuel ratio feedback correction coefficient for the gas fuel. To do.

 In the present invention, as the second solving means related to the fuel injection system, in the first solving means, the gaseous fuel injection control device is inputted from the liquid fuel injection control device during the gaseous fuel operation. The basic fuel injection quantity is calculated based on the first drive signal, and the basic fuel injection quantity is multiplied by the air fuel ratio feedback correction coefficient for the gaseous fuel to calculate the gaseous fuel injection quantity. A means of outputting a second drive signal corresponding to the result to the gaseous fuel injection valve is adopted.

 Further, in the present invention, as a third solving means relating to the fuel injection system, in the first or second solving means, the gaseous fuel injection control device is configured such that the engine operating state stabilizes the air-fuel ratio feedback correction coefficient. In other words, the air-fuel ratio feedback correction coefficient is estimated when it is included in the region that can be estimated.

In the present invention, the air / fuel ratio feedback correction used by the gaseous fuel injection control device for correcting the basic gasoline injection amount based on the output signal of the intake air amount sensor and the first drive signal input from the liquid fuel injection control device. The coefficient is estimated, and the ratio of the air-fuel ratio feedback correction coefficient estimated during the liquid fuel operation and during the gas fuel operation is calculated as the air-fuel ratio feedback correction coefficient for the gas fuel.
As a result, the change amount of the air-fuel ratio feedback coefficient during the liquid fuel operation and the gas fuel operation can be grasped, and the change is corrected on the gas fuel injection control device side, so that the liquid fuel operation and the gas fuel are corrected. The difference in fuel injection amount from that during operation can be eliminated. In other words, according to the present invention, it becomes possible to perform air-fuel ratio feedback correction using the air-fuel ratio feedback correction coefficient for gaseous fuel on the gaseous fuel injection control device side. Lean generation can be prevented, and as a result, it is possible to avoid a decrease in emission performance.

It is a schematic structure figure of fuel injection system A concerning this embodiment. It is a flowchart which shows the air fuel ratio feedback control (gas feedback correction control) for gas fuels which 2nd-ECU4 implements. It is a figure which shows the effect of the gas feedback correction | amendment control by this embodiment.

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 system A according to the present embodiment. The fuel injection system A is a bi-fuel system that selectively switches between liquid fuel (for example, gasoline) and gaseous fuel (for example, compressed natural gas) and supplies it to a single engine (not shown). And a gaseous fuel supply system 2, a 1st-ECU (Electronic Control Unit) 3, a 2nd-ECU 4, and a fuel changeover switch 5.

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

 The gasoline supply pipe 12 is a pipe for delivering gasoline from the gasoline tank 11 to the gasoline injector 13. The gasoline injector 13 is an electromagnetic valve (for example, a solenoid valve) mounted on the intake pipe so that the injection port is exposed toward the intake port of the engine, for example, and corresponds to a gasoline pulse signal input from the 2nd-ECU 4. A predetermined amount of gasoline is injected.

 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 26 (gaseous fuel injection valve), and a low pressure side fuel pressure sensor 27. And a low-pressure side fuel temperature sensor 28.

 The gas tank 21 is a high pressure vessel filled with 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 25. The shut-off valve 23 is an electromagnetic valve inserted in the middle of the high-pressure gas supply pipe 22 (position close to the gas tank 21), and opens or closes according to a shut-off valve drive signal input from the 2nd-ECU 4.

 The regulator 24 is a pressure reducing valve disposed on the downstream side of the shutoff valve 23, and decompresses the high pressure gas fuel supplied from the gas tank 21 to a desired pressure when the shutoff 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, for example, the injection port is exposed toward the intake port of the engine, and injects a predetermined amount of gas fuel according to a gas pulse signal input from the 2nd-ECU 4. To do. Thus, the high-pressure gas supply pipe 22 and the low-pressure gas supply pipe 25 correspond to a gaseous fuel supply path from the gas tank 21 to the gas injector 26.

 The low pressure side fuel pressure sensor 27 detects the low pressure side (downstream side) from the regulator 24, that is, the internal pressure (low pressure side fuel pressure) of the low pressure gas supply pipe 25, and outputs a low pressure side fuel pressure signal indicating the detection result to the 2nd-ECU 4. To do. The low-pressure side fuel temperature sensor 28 detects the internal temperature (low-pressure side fuel temperature) of the low-pressure gas supply pipe 25 and outputs a low-pressure side fuel temperature signal indicating the detection result to the 2nd-ECU 4.

 The 1st-ECU 3 (liquid fuel injection control device) is configured to inject a gasoline injection amount (liquid fuel) to be injected from the gasoline injector 13 to the engine based on various sensor signals input from various sensors (not shown) that detect the engine operating state. An injection amount) is calculated, and a gasoline pulse signal (first drive signal) having a pulse width corresponding to the calculation result is output to the 2nd-ECU 4. The various sensor signals input to the 1st-ECU 3 include at least a crank pulse signal having a period during which the crankshaft rotates by a certain angle as one cycle, an intake air temperature signal indicating an intake air temperature, an intake air pressure signal indicating an intake air pressure, A throttle opening signal indicating the throttle opening, a cooling water temperature signal indicating the cooling water temperature, an O2 sensor output signal (voltage signal corresponding to the air / fuel ratio) output from the O2 sensor (air / fuel ratio sensor), and the like are included.

 The 2nd-ECU 4 (gaseous fuel injection control device) includes a low pressure side fuel pressure signal input from the low pressure side fuel pressure sensor 27, a low pressure side fuel temperature signal input from the low pressure side fuel temperature sensor 28, and an air flow sensor (intake air amount). Based on the air flow sensor output signal indicating the intake air amount input from the sensor), the gasoline pulse signal input from the 1st-ECU 3, and the fuel switching signal input from the fuel changeover switch 5, the gasoline injector 13 and the gas Energization control of the injector 26 and the shutoff valve 23 is performed.

 Specifically, when the 2nd-ECU 4 recognizes that gasoline is selected as the fuel to be used for engine operation based on the fuel switching signal input from the fuel switch 5 (that is, during gasoline operation), The gasoline pulse signal input from the 1st-ECU 3 is output to the gasoline injector 13 as it is.

 When the 2nd-ECU 4 recognizes that gas fuel is selected as the fuel to be used for engine operation based on the fuel switch signal input from the fuel switch 5 (that is, during gas operation), the shut-off valve 23 is opened to start supply of gas fuel from the gas tank 21 to the gas injector 26, and from the gas injector 26 based on the gasoline pulse signal, the airflow sensor output signal, the low pressure side fuel pressure signal and the low pressure side fuel temperature signal. A gas injection amount (gaseous fuel injection amount) to be injected into the engine is calculated, and a gas pulse signal (second drive signal) having a pulse width corresponding to the calculation result is generated and output to the gas injector 26.

 The fuel change-over switch 5 is a switch that enables the fuel to be changed by a user's manual operation. Whether the liquid fuel is selected as the state of the switch, that is, the fuel used for engine operation, or the gaseous fuel is selected. A fuel switching signal indicating whether or not the fuel is being output is output to the 2nd-ECU 4.

Next, the operation of the fuel injection system A configured as described above will be described in detail.
<Operation of 1st-ECU 3>
The 1st-ECU 3 should inject fuel into the engine at each fuel injection timing based on various sensor signals regardless of the state of the fuel switch 5 (that is, regardless of gasoline operation or gas operation) while the engine is operating. The gasoline injection amount (the energization time of the gasoline injector 13) is calculated, and a gasoline pulse signal having a pulse width corresponding to the calculation result is output to the 2nd-ECU 4.

 Specifically, the 1st-ECU 3 calculates the engine speed from the crank pulse signal, and calculates the basic gasoline injection amount based on the engine speed, the intake air temperature, the coolant temperature, the intake pressure, and the throttle opening. Further, the 1st-ECU 3 corrects the basic gasoline injection amount so that the air-fuel ratio becomes the target air-fuel ratio (theoretical air-fuel ratio or an air-fuel ratio appropriate for the engine operating state) based on the O2 sensor output signal. Feedback control is also implemented.

 Here, in the air-fuel ratio feedback control, the 1st-ECU 3 associates the previously calculated air-fuel ratio feedback correction coefficient (coefficient for correcting the gasoline basic injection amount) with the engine operating state at that time in the internal memory in a timely manner. Remember and update. Thus, storing and updating the air-fuel ratio feedback correction coefficient calculated in the past in the memory in association with the engine operating state is called “learning”, and the air-fuel ratio feedback coefficient obtained by this “learning” is “learned”. Called “value”.

 That is, in the air-fuel ratio feedback control, the 1st-ECU 3 extracts a learning value corresponding to the current engine operating state from the learning values obtained by past learning, that is, an air-fuel ratio feedback correction coefficient, and the air-fuel ratio feedback. By multiplying the previously calculated basic gasoline injection amount by the correction coefficient, the final gasoline injection amount to be injected into the engine is calculated.

<Operation of 2nd-ECU 4>
On the other hand, the 2nd-ECU 4 receives a gas pulse signal from the 1st-ECU 3 for the air-fuel ratio feedback control for gas fuel (hereinafter referred to as gas feedback correction control) shown in the flowchart of FIG. Perform every time.

  As shown in FIG. 2, in the gas feedback correction control, the 2nd-ECU 4 first measures the time of the pulse width of the gasoline pulse signal input from the 1st-ECU 3 (the energization time of the gasoline injector 13) (step S1). . Here, since the pulse width of the gasoline pulse signal is set to a time corresponding to the gasoline injection amount calculated by the 1st-ECU 3, the 2nd-ECU 4 determines the pulse width of the gasoline pulse signal and the flow rate of the gasoline injector 13. The gasoline injection amount Pet_mass is calculated backward based on the characteristics (step S2).

  Subsequently, the 2nd-ECU 4 calculates the intake air amount estimated value (estimated intake air amount) Air_mass_s by multiplying the gasoline injection amount Pet_mass calculated in Step S2 by the gasoline theoretical air-fuel ratio Pet_afr (Step S3). ). Subsequently, the 2nd-ECU 4 reads the airflow sensor output signal and performs A / D conversion (step S4). Based on the value obtained by this A / D conversion, the actual intake air amount (actual intake air amount) Air_mass_r is calculated. Calculate (step S5).

  The 2nd-ECU 4 uses the 1st-ECU 3 to correct the basic gasoline injection amount based on the estimated intake air amount Air_mass_s calculated in step S3 and the actual intake air amount Air_mass_r calculated in step S4. Estimated air-fuel ratio feedback correction coefficient (step S6). Specifically, the 2nd-ECU 4 calculates the ratio between the estimated intake air amount Air_mass_s and the actual intake air amount Air_mass_r as an air-fuel ratio feedback correction coefficient estimated value Klamd_s (= Air_mass_s ÷ Air_mass_r).

  Thus, since the 2nd-ECU 4 cannot directly know the air-fuel ratio feedback correction coefficient used for the correction of the basic gasoline injection amount by the 1st-ECU 3, the 1st-ECU 3 performs the above-described steps S1 to S6. The used air-fuel ratio feedback correction coefficient (air-fuel ratio feedback correction coefficient estimated value Klamd_s) is estimated.

  Subsequently, the 2nd-ECU 4 determines whether or not the gas fuel is selected as the fuel to be used for the engine operation based on the fuel switching signal input from the fuel changeover switch 5 (that is, during the gas operation) (step). S7) If “No”, that is, if the gasoline operation is being performed, the processing of steps S8 and S9 described later is executed. If “Yes”, that is, if the gas operation is being performed, steps S10 to S13 described later are performed. Execute the process.

  When “No” is determined in step S7, that is, when it is determined that the gasoline is being operated, the 2nd-ECU 4 includes the engine operating state in a region where the air-fuel ratio feedback correction coefficient can be stably estimated (correction coefficient estimation region). It is determined whether or not (step S8). Specifically, the 2nd-ECU 4 includes the engine operating state in the correction coefficient estimation region when the condition that the engine load is equal to or less than a set value or the variation of the engine load and the engine speed is equal to or less than the set value is satisfied. Judge that

  Here, the reason for using the condition that the engine load is equal to or less than the set value is that when the throttle valve is opened and operating at a high load, pulsation occurs in the intake air passing through the air flow sensor, and an accurate flow rate cannot be measured. It is desirable to estimate (calculate) the air-fuel ratio feedback correction coefficient in the case of a load that does not generate pulsation. Since the intake air amount changes depending on the engine speed, the engine load can be calculated by “intake air amount ÷ maximum intake air amount at the current engine speed”.

  The reason why the engine load and engine speed fluctuation are less than the set value is used is that the engine load fluctuation and engine speed fluctuation are measured by the intake air quantity actually supplied to the cylinder and the air flow sensor. This is because the intake air amount does not match, and it is desirable to estimate the air-fuel ratio feedback correction coefficient when these variations in engine load and engine speed are equal to or less than the set error.

  As for the engine load, the ratio of the average value of the engine load to the engine cycle calculated this time and the engine load calculated this time in one cycle of the engine, that is, the period of two rotations of the crank is calculated. The fuel ratio feedback correction coefficient may be estimated. Similarly, for the engine speed, if the ratio of the average value of the engine speed during the period of two crank rotations and the engine speed calculated this time is equal to or less than the set value, the air-fuel ratio feedback correction coefficient is estimated. good.

If the 2nd-ECU 4 determines “Yes” in step S8 as described above, that is, determines that the engine operating state is included in the correction coefficient estimation region, the air-fuel ratio feedback calculated in step S6. The correction coefficient estimated value Klamd_s is learned as an air-fuel ratio feedback correction coefficient estimated value (gasoline feedback correction coefficient estimated value) Klamd_Pets for gasoline, that is, stored and updated in the internal memory in association with the engine operating state (step S9).
Note that the 2nd-ECU 4 determines that the gas feedback of this time is “No” in step S8, that is, if it is determined that the engine operating state is not included in the correction coefficient estimation region, or after the processing of step S9 is completed. The correction control is terminated.

  On the other hand, if “Yes” is determined in step S7, that is, if it is determined that the gas operation is being performed, the 2nd-ECU 4 determines the low pressure side fuel pressure calculated from the gasoline injection amount Pet_mass calculated in step S2 and the low pressure side fuel pressure signal. The basic gas injection amount Gas_mass_b is calculated based on the low pressure side fuel temperature calculated from the low pressure side fuel temperature signal (step S10).

  Subsequently, the 2nd-ECU 4 determines whether or not the engine operating state is included in the correction coefficient estimation region as in step S8 (step S11). If “Yes”, the process of step S12 described later is performed. On the other hand, in the case of “No”, the process proceeds to step S13 described later.

  That is, in the case of “Yes” in step S11, that is, when it is determined that the engine operating state is included in the correction coefficient estimation region, the 2nd-ECU 4 estimates the air-fuel ratio feedback correction coefficient calculated in step S6. The ratio between the value Klamd_s and the gasoline feedback correction coefficient estimated value Klamd_Pets learned in step S9 is calculated as an air-fuel ratio feedback correction coefficient (gas feedback correction coefficient) Klamd_gas (= Klamd_s ÷ Klamd_Pets) for gas fuel (step) S12).

  Here, as the gasoline feedback correction coefficient estimated value Klamd_Pets used for calculating the gas feedback correction coefficient Klamd_gas, a value corresponding to the current engine operating state is selected from learning values obtained by past learning. Further, the 2nd-ECU 4 stores and updates (that is, learns) the calculated gas feedback correction coefficient Klamd_gas in the internal memory in association with the engine operating state.

  Then, the 2nd-ECU 4 determines the gas corresponding to the current engine operating state from the learned values obtained by the past learning after the processing of the above step S12 or when “No” in the above step S11. The feedback correction coefficient Klamd_gas is taken out and multiplied by the gas basic injection amount Gas_mass_b calculated in step S10, thereby calculating the gas injection amount Gas_mass to be injected from the gas injector 26 to the engine (step S13).

  When the 2nd-ECU 4 calculates the gas injection amount Gas_mass to be injected into the engine during the gas operation by the gas feedback correction control as described above, the 2nd-ECU 4 generates a gas pulse signal having a pulse width corresponding to the calculation result to generate a gas injector. 26. The 2nd-ECU 4 outputs the gasoline pulse signal input from the 1st-ECU 3 to the gasoline injector 13 as it is during gasoline operation.

 As described above, in the present embodiment, the 2nd-ECU 4 uses the 1st-ECU 3 to correct the basic gasoline injection amount based on the air flow sensor output signal and the gasoline pulse signal input from the 1st-ECU 3. The fuel ratio feedback correction coefficient is estimated, and the ratio of the air fuel ratio feedback correction coefficient estimated during the gasoline operation and during the gas operation is calculated as the gas feedback correction coefficient for the gas fuel.

 As a result, it is possible to grasp the amount of change in the air-fuel ratio feedback coefficient during gasoline operation and during gas operation, and by correcting the amount of change on the 2nd-ECU 4 side, fuel injection during gasoline operation and during gas operation is performed. The difference in quantity can be eliminated. That is, conventionally, as shown in FIG. 3 (a), the air-fuel ratio over-rich or over-lean occurs at the time of fuel switching, and the emission performance is deteriorated, whereas in this embodiment, FIG. 3 (b) As shown in FIG. 2, by performing air-fuel ratio feedback correction using the gas feedback correction coefficient for gas fuel on the 2nd-ECU 4 side, it is possible to prevent the occurrence of air-fuel ratio overrich or overlean during fuel switching. It is possible to avoid a decrease in emission performance.

  A ... fuel injection system, 1 ... liquid fuel supply system, 2 ... gaseous fuel supply system, 3 ... 1st-ECU (liquid fuel injection control device), 4 ... 2nd-ECU (gaseous fuel injection control device), 5 ... fuel switching Switch, 13 ... gasoline injector (liquid fuel injection valve), 21 ... gas tank (gas fuel tank), 26 ... gas injector (gas fuel injection valve)

Claims (3)

The liquid fuel basic injection amount is calculated based on the engine operating state, and an air-fuel ratio feedback correction coefficient for making the actual air-fuel ratio calculated from the output signal of the air-fuel ratio sensor coincide with the target air-fuel ratio is set as the liquid fuel basic injection amount. The liquid fuel injection control device that calculates the liquid fuel injection amount by multiplication and outputs a first drive signal according to the calculation result, and the first drive input from the liquid fuel injection control device during gas fuel operation In a fuel injection system comprising a gaseous fuel injection control device that calculates a gaseous fuel basic injection amount based on a signal,
Estimating the air-fuel ratio feedback correction coefficient used for correcting the liquid fuel basic injection amount based on the output signal of the intake air amount sensor and the first drive signal input from the liquid fuel injection control device; A fuel injection system characterized in that the ratio of the air-fuel ratio feedback correction coefficient estimated during fuel operation and during gas fuel operation is calculated as the air-fuel ratio feedback correction coefficient for gas fuel.   The gaseous fuel injection control device calculates a gaseous fuel basic injection amount based on the first drive signal input from the liquid fuel injection control device during the gaseous fuel operation, and provides an air-fuel ratio feedback for the gaseous fuel. 2. The gas fuel injection amount is calculated by multiplying the gas fuel basic injection amount by a correction coefficient, and a second drive signal corresponding to the calculation result is output to the gas fuel injection valve. Fuel injection system.   The gaseous fuel injection control device estimates the air-fuel ratio feedback correction coefficient when the engine operating state is included in a region where the air-fuel ratio feedback correction coefficient can be stably estimated. The fuel injection system according to claim 1 or 2.

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