JP3957529B2 - Fuel injection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronically controlled fuel injection method for supplying fuel to an engine or the like, and in particular, fuel accurately without being affected by fluctuations in power supply voltage or fluctuations in the coil resistance of a solenoid constituting an injector. The present invention relates to a fuel injection method for performing injection.
[0002]
[Prior art]
FIG. 15 is a diagram for explaining a control mechanism of a conventional fuel injection device that performs correction based on a power supply voltage. In this type of control mechanism, the power supply voltage V _B applied to the power supply terminal 11 is supplied to an ECU (Electronic) via a power supply voltage input circuit 12.
To the microcomputer 13 of the control unit.
[0003]
When the power supply voltage V _B is low, the microcomputer 13 outputs a pulse having a waveform that lengthens the ON period of the FET 14 to the FET drive circuit 15. As a result, the time during which the coil current flows through the solenoid 16 becomes longer, and the fuel injection time becomes longer. When the power supply voltage V _B is high, the reverse is true, and the fuel injection amount is controlled to be constant by shortening the fuel injection time. Immediately after the FET 14 is switched from on to off, the current flowing through the solenoid 16 flows to the Zener diode 18 via the diode 17, and the drain voltage of the FET 14 becomes substantially the same as the voltage of the Zener diode 18, where power is consumed and fuel is consumed. Injection stops.
[0004]
FIG. 16 is a diagram for explaining a control mechanism of a conventional fuel injection device that performs constant current control. In this type of control mechanism, the coil current is detected by the resistor 22 and the current detection circuit 23 added for current detection. Then, the microcomputer 13 and a constant current driving circuit 24 is controlled so that the coil current is not changed by variations in the supply voltage V _B.
[0005]
[Problems to be solved by the invention]
However, in the control mechanism that performs correction based on the power supply voltage as shown in FIG. 15, when the temperature of the coil constituting the solenoid 16 rises, the resistance value of the coil changes, and even if the power supply voltage V _B is the same, the coil Since the current changes, there is a problem that it is difficult to accurately correct the fuel injection amount. According to the constant current control as shown in FIG. 16, the coil current can be controlled to be constant even if the coil temperature rises. However, the complexity of the control circuit for that purpose increases the number of parts and increases the software processing. There was an inconvenience of inviting.
[0006]
Recently, the present inventors have proposed a new type of injection device (hereinafter referred to as “injection device”) that injects fuel while being pressurized, unlike conventional injectors that inject fuel that has been pressurized and sent by a fuel pump or regulator. , A discharge pump).
[0007]
Since this discharge pump has the characteristic that the injection amount is affected by the coil current that drives the fuel injection solenoid, the drive pulse width is simply increased or decreased by the control mechanism that performs correction based on the power supply voltage described above. However, there is a problem that it is not possible to correct the injection amount accurately.
[0008]
The present invention has been made in view of the above circumstances, and can accurately correct the fuel injection amount without complicating the control circuit and increasing the number of parts. In the above-described discharge pump, Another object of the present invention is to provide a fuel injection method capable of accurately correcting the fuel injection amount.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a fuel injection method according to the present invention detects a coil current value when a sampling time corresponding to a power supply voltage value at the start of driving of a fuel injection solenoid has elapsed, and based on the detected value. This corrects the drive stop timing of the solenoid. According to the present invention, the drive stop timing of the fuel injection solenoid is corrected based on the coil current value at the time when the sampling time corresponding to the power supply voltage value has elapsed from the start of driving of the solenoid.
[0010]
Also, the fuel injection method according to the present invention detects the coil current value when the sampling time corresponding to the coil current value detected at the previous fuel injection has elapsed since the start of driving of the fuel injection solenoid. The drive stop timing of the solenoid is corrected based on the detected value. According to this invention, the drive stop timing of the fuel injection solenoid is based on the coil current value at the time when the sampling time corresponding to the coil current value detected at the previous fuel injection has elapsed since the start of the solenoid drive. It is corrected.
[0011]
In the fuel injection method according to the present invention, the first coil current value is detected when a predetermined time has elapsed from the start of driving of the fuel injection solenoid, and the sampling time corresponding to the detected value is determined. When the time has elapsed, the second coil current value is detected, and the solenoid drive stop timing is corrected based on the detection value obtained by the second sampling. According to the present invention, the drive stop timing of the fuel injection solenoid is corrected based on the coil current value at the time when the sampling time has elapsed according to the coil current value after the elapse of a predetermined time from the start of driving of the solenoid.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
First, the configuration of a discharge pump system to which the fuel injection method according to the present invention is applied will be described. FIG. 1 is a diagram showing a schematic configuration of a discharge pump system to which a fuel injection method according to the present invention is applied. As shown in FIG. 1, the discharge pump system passes a plunger pump 32 as an electromagnetic drive pump that pumps fuel in a fuel tank 31 and fuel pressurized to a predetermined pressure by pumping by the plunger pump 32. An inlet orifice nozzle 33 having an orifice portion, an injection nozzle 34 that injects fuel into the intake passage (of the engine) when the fuel passing through the inlet orifice nozzle 33 is equal to or higher than a predetermined pressure, engine operation information, and a plunger pump 32 A drive driver 35 and a control unit (ECU) 36 for generating a control signal to the plunger pump 32 and the like based on the value of the coil current flowing through the solenoid are provided as its basic configuration.
[0013]
FIG. 2 is a diagram for explaining a control mechanism of the discharge pump system to which the fuel injection method according to the first embodiment of the present invention is applied. In FIG. 2, the solenoid 46 constitutes the plunger pump 32. For example, an N-channel FET 44, an FET drive circuit 45, a power supply voltage detection circuit 49, a current detection resistor 52, a current detection circuit 53, a diode 47 and a Zener diode 48 which are switching elements for driving the solenoid 46 are drive drivers 35. include. The Zener diode 48 consumes the solenoid current when the FET 44 is turned from on to off, with the drain voltage of the FET 44 being the same as the voltage of the Zener diode 48. The microcomputer 43 is included in the control unit 36.
[0014]
The power supply voltage detection circuit 49 detects the power supply voltage V _B and supplies the detected value to the microcomputer 43. One end of the solenoid 46 is connected to the power supply terminal 41 to which the power supply voltage V _B is applied. The other end of the solenoid 46 is connected to the drain of the FET 44 and to the gate of the FET 44 through the diode 47 and the Zener diode 48. A drive pulse generated in the FET drive circuit 45 based on a control signal output from the microcomputer 43 is supplied to the gate of the FET 44.
[0015]
The source of the FET 44 is grounded via a current detection resistor 52. When the FET 44 is turned on by the drive pulse, a current (coil current) flows from the power supply terminal 41 to the ground terminal via the solenoid 46, the FET 44, and the resistor 52, and the solenoid 46 is driven. The magnitude of the current flowing through the resistor 52 is input to the current detection circuit 53 as a voltage signal, where the current value is detected, and the detected value is input to the microcomputer 43.
[0016]
In the discharge pump system, since the solenoid 46 injects fuel while pressurizing the fuel, the amount of fuel injection is affected by the drive current flowing through the solenoid 46, that is, the coil current. FIG. 3 schematically shows the relationship between the fuel injection amount Q and the drive pulse width T of the solenoid. As shown in FIG. 3, the fuel injection amount remains zero until the pulse width reaches a certain value (Toffset), and thereafter, the value of the fuel injection amount increases with a certain slope Td as the pulse width increases. Increase with.
[0017]
The time from when the pulse width becomes zero to Toffset is a time called dead time or invalid time, and does not affect the fuel injection amount. In addition, the slope Td is a ratio between an increase in the required fuel amount (required fuel injection amount) Qc and an increase in the drive pulse width. When these Td and Toffset are used, the drive pulse width Tout necessary to accurately obtain the required fuel injection amount Qc is expressed by the following equation (1).
[0018]
Tout = Qc × Td + Toffset (1)
[0019]
By the way, the dead time Toffset is a function of the value of the coil current Ih flowing through the solenoid when a certain sampling time Ts has elapsed from the start of driving of the solenoid and the sampling time Ts. That is, by detecting the coil current after a certain sampling time has elapsed from the start of solenoid driving, the Toffset value corresponding to the detected value Ih at that time is obtained. The value of Toffset is obtained from, for example, a three-dimensional display map obtained by mapping Toffset values corresponding to combinations of various Ts values and various Ih values. This map is obtained in advance by experiments or the like.
[0020]
The same applies to the slope Td. For example, the slope Td can be obtained from a three-dimensional display map in which Td values corresponding to combinations of various Ts values and various Ih values are mapped. This map is obtained in advance by experiments or the like. However, if the relationship between the required fuel injection amount Qc and the drive pulse width Tout is not linear, the required fuel injection amount Qc also affects Td, which needs to be taken into consideration.
[0021]
FIG. 4 is a conceptual diagram showing how to determine the drive pulse width Tout of the solenoid. As shown in FIG. 4, first, the multiplier 75 multiplies the required fuel injection amount Qc and the gradient Td. The value of Td is obtained from the map 81 based on the detected value Ih of the coil current at the time when the sampling time Ts has elapsed from the start of driving of the solenoid. However, when the relationship between the required fuel injection amount Qc and the drive pulse width Tout is not linear, the required fuel injection amount Qc is also considered.
[0022]
Subsequently, the adder 76 adds the dead time Toffset to the value of Qc × Td. The value of Toffset is obtained from the map 82 based on the detected value Ih of the coil current at the time when the sampling time Ts has elapsed from the start of driving of the solenoid. In this way, the drive pulse width Tout is obtained. Here, the multiplier 75 and the adder 76 are included in the control unit 36. The maps 81 and 82 are obtained in advance by experiments or the like and are stored in a nonvolatile memory in the control unit 36.
[0023]
Next, a fuel injection method according to the first embodiment of the present invention will be described. In the fuel injection method according to the first embodiment, the sampling time from the start of driving of the solenoid to the detection of the coil current value is changed according to the power supply voltage. FIG. 5 is a flowchart illustrating an example of a processing procedure of the fuel injection method according to the first embodiment of the present invention.
[0024]
When the fuel injection method according to the first embodiment is started, first, the power supply voltage detection circuit 49 detects the power supply voltage V _B and inputs it to the microcomputer 43 (step S51). The microcomputer 43, sampling converts the detected value of the power supply voltage V _B to a digital signal, corresponding map mapping the sampling time Ts with respect to the power supply voltage V _B (see FIG. 6) to the detected value of power supply voltage V _B Time Ts is obtained (step S52). The map shown as an example in FIG. 6 is obtained in advance by experiments or the like, and is stored in the nonvolatile memory in the control unit 36.
[0025]
Next, driving of the discharge pump is started (step S53). When the sampling time Ts obtained in step S52 has elapsed after the start of driving, the coil current Ih is detected by the current detection circuit 53 and input to the microcomputer 43 (step S54). The microcomputer 43 converts the detected value of the coil current Ih into a digital signal, and obtains a slope Td corresponding to the detected value of the coil current Ih from the map 81 (see FIG. 4) (step S55). Further, the dead time Toffset corresponding to the detected value of the coil current Ih is obtained from the map 82 (see FIG. 4) (step S56).
[0026]
Using the calculated values of Td and Toffset and the required fuel injection amount Qc, the above equation (1) is calculated to determine the actual drive pulse width Tout (step S57). The obtained drive pulse width Tout is set in a timer (not shown) in the microcomputer 43 (step S58), and the discharge pump is driven when the elapsed time from the start of the discharge pump reaches the timer value. Stop (step S59). The above processing is repeated from the start of engine operation to the stop of operation. FIG. 7 schematically shows the waveform of the coil current when the detected value of the power supply voltage V _B is 7V, 12V and 16V, and schematically shows the relationship between the sampling timing of the coil current and the drive pulse width.
[0027]
According to the first embodiment described above, the coil current can be detected at a timing corresponding to the fluctuation of the power supply voltage by detecting the power supply voltage. Therefore, the drive stop timing of the discharge pump can be determined appropriately without being affected by fluctuations in the power supply voltage, so that fuel injection can be performed accurately. In particular, if the time from the start of the discharge pump to the sampling of the coil current is determined to be a certain time, the driving of the discharge pump is terminated before the sampling of the coil current when the power supply voltage V _B is high. However, according to the first embodiment, the problem can be avoided. In addition, by applying the fuel injection method of the first embodiment, it is not necessary to provide a constant current drive circuit or the like in the fuel injection device, so that the control circuit is simplified and the number of parts is reduced. There is an effect that is possible.
[0028]
Embodiment 2. FIG.
FIG. 8 is a diagram for explaining a control mechanism of the discharge pump system to which the fuel injection method according to the second embodiment of the present invention is applied. The control mechanism of the discharge pump system shown in FIG. 8 is different from the configuration of the first embodiment shown in FIG. 2 in that the power supply voltage detection circuit 49 is not provided. Since other configurations are the same as those of the first embodiment, the same reference numerals as those of the first embodiment are given and the description thereof is omitted.
[0029]
A fuel injection method according to Embodiment 2 of the present invention will be described. In the fuel injection method according to the second embodiment, the sampling time from the start of driving the solenoid to the detection of the coil current value is changed according to the coil current value detected at the previous fuel injection. FIG. 9 is a flowchart illustrating an example of a processing procedure of the fuel injection method according to the second embodiment of the present invention.
[0030]
When the fuel injection method according to the second embodiment is started, first, the microcomputer 43 reads the previous coil current value Ib from a memory (not shown) in the microcomputer 43 (step S91). Then, a sampling time Ts corresponding to the previous coil current value Ib is obtained from a map (see FIG. 10) in which the sampling time Ts is mapped to the previous coil current value Ib (step S92). The map shown as an example in FIG. 10 is obtained in advance by experiments or the like and is stored in the nonvolatile memory in the control unit 36.
[0031]
Next, the processes from the start of the discharge pump (step S93) to the stop of the drive (step S99) are performed in the same manner as steps S53 to S59 in FIG. After the discharge pump is stopped, the detected value of the coil current Ih detected at the time of the current fuel injection is used as the value of the previous coil current value Ib in order to determine the sampling timing at the next fuel injection ( Step S100). The above processing is repeated from the start of engine operation to the stop of operation. FIG. 11 schematically shows the waveform of the coil current when the previous coil current value Ib is 2A, 4A, and 6A, and schematically shows the relationship between the coil current sampling timing and the drive pulse width.
[0032]
By the way, when the solenoid 46 is driven for the first time, such as when the engine is started, there is no previous fuel injection cycle, so there is no data of the previous coil current value Ib. The same applies to the case where the driving of the solenoid 46 is resumed after the fuel injection is interrupted when the vehicle goes down a hill or when a fuel cut such as an idling stop is performed. Further, even when the microcomputer 43 is reset due to an extreme decrease in the power supply voltage V _B , it is impossible to refer to the Ib data at the previous fuel injection. For such a case, the power supply voltage V _B is detected only at the time of starting the engine or at the time of driving the solenoid 46 again after interruption of fuel injection, and the slope Td is determined based on the detected value. The dead time Toffset may be obtained. In this case, the power supply voltage detection circuit 49 is required.
[0033]
According to the second embodiment described above, the previous coil current value Ib reflects the fluctuation of the power supply voltage, such that if the power supply voltage at the previous fuel injection is high, the previous coil current value Ib increases. In addition, since the power supply voltage at the time of fuel injection is hardly different between the previous time and this time, by detecting the coil current Ih when the sampling time Ts corresponding to the previous coil current value Ib has elapsed, The coil current can be detected at an appropriate timing without measuring the power supply voltage. Therefore, since the discharge pump drive stop timing can be appropriately obtained without being affected by fluctuations in the power supply voltage and coil resistance, fuel injection can be performed accurately. Further, by applying the fuel injection method of the second embodiment, it is not necessary to provide a power supply voltage detection circuit in the fuel injection device, so that the control circuit is further simplified and the number of parts is reduced as compared with the first embodiment. It is possible.
[0034]
Embodiment 3 FIG.
The control mechanism of the discharge pump system to which the fuel injection method according to the third embodiment of the present invention is applied is the same as the control mechanism shown in FIG.
[0035]
A fuel injection method according to Embodiment 3 of the present invention will be described. In the fuel injection method according to the third embodiment, the first coil current value is detected after a predetermined time has elapsed from the start of driving of the solenoid, and the second coil current value is detected based on the detected value. The sampling time is changed. Then, the drive stop timing of the discharge pump is obtained based on the detected value of the second coil current. FIG. 12 is a flowchart illustrating an example of a processing procedure of the fuel injection method according to the third embodiment of the present invention.
[0036]
When the fuel injection method according to the third embodiment is started, first, the driving of the discharge pump is started (step S121). When the first sampling time Ts1 has elapsed after the start of driving, the first coil current Ih1 is detected by the current detection circuit 53 and input to the microcomputer 43 (step S122). The microcomputer 43 converts the detection value of the first coil current Ih1 into a digital signal, and maps the second sampling time Ts2 to the first coil current Ih1 (see FIG. 13). A second sampling time Ts2 corresponding to the detected value of the first coil current Ih1 is obtained (step S123). The map shown as an example in FIG. 13 is obtained in advance by experiments or the like and is stored in the nonvolatile memory in the control unit 36.
[0037]
Next, when the second sampling time Ts2 elapses, the current detection circuit 53 detects the second coil current Ih2, and inputs it to the microcomputer 43 (step S124). In the microcomputer 43, the detected value of the second coil current Ih2 is converted into a digital signal, and the gradient Td and waste corresponding to the detected value of the second coil current Ih2 are calculated from the maps 81 and 82 (see FIG. 4). Time Toffset is obtained (steps S125 and S126).
[0038]
The actual drive pulse width Tout is obtained from the obtained values of Td and Toffset, the required fuel injection amount Qc and the above equation (1) (step S127). The drive pulse width Tout is set in a timer (not shown) in the microcomputer 43 (step S128), and the discharge pump is stopped when the timer expires (step S129). The above processing is repeated from the start of engine operation to the stop of operation. FIG. 14 schematically shows the waveform of the coil current when the first coil current value Ih1 is 2A, 4A, and 6A, and the first sampling timing and the second sampling timing of the coil current. The relationship between the driving pulse width and the driving pulse width is schematically shown.
[0039]
According to the third embodiment described above, if the power supply voltage at the time of fuel injection is high, the detected value of the first coil current Ih1 becomes large. Therefore, the coil current is determined based on the detected value of the first coil current Ih1. By obtaining the second sampling timing and detecting the second coil current Ih2 at the second sampling timing, the coil current can be detected at the optimum timing without measuring the power supply voltage. it can. Therefore, even when the drive pulse width changes abruptly, such as during acceleration / deceleration, the discharge pump drive stop timing can be determined appropriately without being affected by fluctuations in the power supply voltage. Fuel injection can be performed. Further, by applying the fuel injection method of the third embodiment, it is not necessary to provide a power supply voltage detection circuit in the fuel injection device, so that the control circuit is further simplified and the number of parts is reduced as compared with the first embodiment. It is possible.
[0040]
In the above, this invention is not restricted to each embodiment mentioned above, A various change is possible. For example, when the slope Td and the dead time Toffset are obtained based on the detected value of the coil current, instead of using a map, a relational expression for obtaining them may be derived and obtained from the relational expression. Further, the present invention is not limited to the discharge pump but can be applied to a conventional injector.
[0041]
【The invention's effect】
According to the present invention, the coil current detected at the time of the previous fuel injection based on the coil current value at the time when the sampling time corresponding to the power supply voltage value at the start of driving of the solenoid has elapsed or from the start of driving of the solenoid. Based on the coil current value at the time when the sampling time according to the value has elapsed, or based on the coil current value at the time when the sampling time has elapsed according to the coil current value after a predetermined time has elapsed from the start of driving the solenoid, Since the drive stop timing of the fuel injection solenoid is corrected, the fuel injection amount can be accurately corrected without being affected by fluctuations in the power supply voltage value. Further, since a conventional constant current drive circuit or the like is not required, there is an effect that a fuel injection method capable of simplifying the control circuit and reducing the number of parts can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a discharge pump system to which a fuel injection method according to the present invention is applied.
FIG. 2 is a diagram for explaining a control mechanism of a discharge pump system to which a fuel injection method according to a first embodiment of the present invention is applied.
FIG. 3 is a characteristic diagram schematically showing fuel injection characteristics in a discharge pump system to which a fuel injection method according to the present invention is applied.
FIG. 4 is a diagram conceptually showing how to obtain a drive pulse width in a discharge pump system to which a fuel injection method according to the present invention is applied.
FIG. 5 is a flowchart showing an example of a processing procedure of the fuel injection method according to the first embodiment of the present invention.
FIG. 6 is a diagram showing an example of a map used in the fuel injection method according to the first embodiment of the present invention.
7 is a diagram schematically showing a relationship among a power supply voltage, a coil current, a sampling timing of the coil current, and a drive pulse width in the fuel injection method according to the first embodiment of the present invention. FIG.
FIG. 8 is a diagram for explaining a control mechanism of a discharge pump system to which a fuel injection method according to a second embodiment of the present invention is applied.
FIG. 9 is a flowchart showing an example of a processing procedure of a fuel injection method according to a second embodiment of the present invention.
FIG. 10 is a diagram showing an example of a map used in the fuel injection method according to the second embodiment of the present invention.
FIG. 11 is a diagram schematically showing the relationship between the previous coil current value, the current coil current, the sampling timing of the current coil current, and the drive pulse width in the fuel injection method according to the second embodiment of the present invention;
FIG. 12 is a flowchart showing an example of a processing procedure of a fuel injection method according to a third embodiment of the present invention.
FIG. 13 is a diagram showing an example of a map used in the fuel injection method according to the third embodiment of the present invention.
FIG. 14 is a diagram schematically showing a relationship among a coil current, a first sampling timing of the coil current, a second sampling timing, and a drive pulse width in the fuel injection method according to the third embodiment of the present invention; .
FIG. 15 is a diagram for explaining a control mechanism of a fuel injection device of a type that performs correction based on a conventional power supply voltage.
FIG. 16 is a diagram for explaining a control mechanism of a conventional fuel injection device that performs constant current control.
[Explanation of symbols]
41 Power supply terminal 43 Microcomputer 44 N-channel FET
45 FET drive circuit 46 Solenoid 47 Diode 48 Zener diode 49 Power supply voltage detection circuit 52 Current detection resistor 53 Current detection circuit

Claims (6)

Starting driving a solenoid for fuel injection;
Detecting a coil current value at the time when a sampling time corresponding to a power supply voltage value at the start of driving of the solenoid has passed;
Correcting the drive stop timing of the solenoid based on the detected coil current value;
A step of stopping the drive of the solenoid at the corrected drive stop timing;
A fuel injection method comprising: The relationship between the sampling time with respect to the power supply voltage value is obtained in advance, and the power supply voltage value is detected before the solenoid starts to be driven. Based on the detected value of the power supply voltage and the relationship between the sampling time with respect to the power supply voltage value, The fuel injection method according to claim 1, wherein a sampling time is obtained. Starting driving a solenoid for fuel injection;
Detecting the coil current value at the time when the sampling time corresponding to the coil current value detected at the time of the previous fuel injection has elapsed from the start of driving of the solenoid;
Correcting the drive stop timing of the solenoid based on the detected coil current value;
A step of stopping the drive of the solenoid at the corrected drive stop timing;
A fuel injection method comprising: 4. The sampling time with respect to the coil current value at the previous fuel injection is obtained in advance, and the sampling time is obtained based on the relationship and the coil current value at the previous fuel injection. Fuel injection method. Starting driving a solenoid for fuel injection;
Detecting a first coil current value after a predetermined time has elapsed from the start of driving of the solenoid;
Detecting a second coil current value when a sampling time corresponding to the detected first coil current value has elapsed;
Correcting the drive stop timing of the solenoid based on the detected second coil current value;
A step of stopping the drive of the solenoid at the corrected drive stop timing;
A fuel injection method comprising: 6. The fuel injection method according to claim 5, wherein a relationship between the sampling time and the first coil current value is obtained in advance, and the sampling time is obtained based on the relationship and the first coil current value. .

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