JPH04325763A - Fuel pump control device - Google Patents

Abstract

PURPOSE:To detect the short-circuit and disconnection of wiring in a device for detecting the abnormality of a fuel pump. CONSTITUTION:A current supplied to a motor-driven fuel pump 6 is controlled by a switching element 41, and whether this current has become an overcurrent is detected by an overcurrent detector 43. At the normal time, a latch 44 generates high-level output voltage, and when the driving current of the fuel pump 6 becomes the overcurrent, the output voltage of the latch 44 is lowered to earth voltage by the output signal of the overcurrent detector 43, so that the input voltage of the input terminal 47 of an input port 25 becomes earth voltage. The input voltage of the input terminal 47 becomes earth voltage also when a signal line 46 is short-circuited or disconnected. When the input voltage of the input terminal 47 becomes earth voltage, current supply to the fuel pump 6 is temporarily stopped and then resumed. At this time, the signal line 46 is judged to be short-circuited or disconnected when the input voltage of the input terminal 47 is still earth voltage.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pump control device.

0002

2. Description of the Related Art In an electric fuel pump, for example, if a foreign object enters the fuel pump and the rotation of the fuel pump is stopped, that is, if the fuel pump is locked, the driving current of the fuel pump increases, causing an overcurrent in the fuel pump. is supplied. Therefore, the fuel pump control device detects the drive current of the fuel pump, and when this drive current exceeds a set value, it determines that the fuel pump is locked, stops the fuel pump, and lights up a warning light. is publicly known (
(See Japanese Patent Application Laid-Open No. 63-235658).

0003

[Problems to be Solved by the Invention] As described above, there is a known fuel pump control device that determines that the fuel pump is locked when the drive current of the fuel pump exceeds a set value. At present, no consideration is given to detecting any abnormality that occurs in the wiring of the drive current detection system.

0004

[Means for Solving the Problems] According to the present invention, in order to detect an abnormality in wiring, as shown in the configuration diagram of the invention in FIG. A driving current detection means A that outputs a substantially constant voltage when the voltage is below a predetermined set value and changes the output voltage when the voltage exceeds the set value; A drive current supply control means B temporarily stops the supply of the fuel pump drive current when the voltage changes, and then restarts the supply of the fuel pump drive current, A determining means C is provided which determines that there is an abnormality in the wiring between the driving current detecting means A and the driving current supply controlling means B when the voltage is changing from a constant voltage.

[0005]

[Operation] When the fuel pump is locked, the input voltage of the drive current supply control means changes from a substantially constant voltage. Further, even when an abnormality occurs in the wiring between the drive current detection means and the drive current supply control means, the input voltage of the drive current supply control means changes from a substantially constant voltage. However, if the supply of fuel pump drive current is temporarily stopped when the input voltage of the drive current control means changes from a substantially constant voltage, the fuel pump drive current immediately decreases, and then the supply of fuel pump drive current stops. When the fuel pump is restarted, if the fuel pump is locked, the input voltage of the drive current supply control means will be approximately constant voltage, and if there is an abnormality in the wiring, the input voltage of the drive current supply control means will be approximately constant voltage. It's changing. Therefore, if the input voltage of the drive current supply control means changes from a substantially constant voltage when the supply of the fuel supply pump drive current is restarted, it is determined that there is an abnormality in the wiring.

[0006]

[Embodiment] Referring to FIG. 2, 1 is an internal combustion engine main body, 20
Reference numeral 40 indicates an electronic control unit, and 40 indicates a fuel pump drive circuit. An intake branch pipe 2 is attached to the internal combustion engine main body 1, and a fuel injection valve 3 for injecting fuel into an intake port is attached to each intake branch pipe 2. Each fuel injection valve 3 is connected to a fuel tank 5 via a fuel conduit 4, and an electric fuel pump 6 for supplying fuel to the fuel injection valve 3 is disposed within the fuel conduit 4. Each intake branch pipe 2 is connected to an air cleaner 9 via a surge tank 7 and an intake duct 8, and a throttle valve 10 is disposed within the intake duct 8. Further, a pressure sensor 11 is arranged inside the surge tank 7.

The electronic control unit 20 is composed of a digital computer, and includes a ROM (read only memory) 22, a RAM (random access memory) 23, a CPU (microprocessor) 24, and an input port 25, which are interconnected by a bidirectional bus 21. and an output port 26. Pressure sensor 11 generates an output voltage proportional to the absolute pressure within surge tank 7 , and this output voltage is input to input port 25 via AD converter 27 . Further, the output port 26 is connected to a first warning light 30 and a second warning light 31 via corresponding drive circuits 28 and 29, respectively.

The drive circuit 40 includes a switching element 41, a current detector 42, an overcurrent detector 43, and a latch 44. The switching element 41 is inserted between the power supply 45 and the fuel pump 6, and the current supplied to the fuel pump 6 is controlled by the switching element 41. This switching element 41 is connected to the output port 26 via the drive circuit 32 and is controlled based on data output to the output port 26. The current supplied to the fuel pump 6 is detected by a current detector 42 connected to the output terminal of the switching element 41. An overcurrent detector 43 is connected to the current detector 42, and this overcurrent detector 43 is composed of, for example, a comparator, and is configured to detect when the current supplied to the fuel pump 6 exceeds a predetermined set value. Output voltage changes from high level to low level.

The output terminal of the overcurrent detector 43 is a latch 44.
The other input terminal of the latch 44 is connected to the output port 26 via the drive circuit 33. On the other hand, the output terminal 44 of the latch 44 is input to the input terminal 47 of the input port 25 via the signal line 46. The output voltage of this latch 44 is normally a substantially constant high level "1".
When the output voltage of the overcurrent detector 43 becomes a low level, the output voltage of the latch 44 becomes a low level "0".
That is, it is lowered to ground voltage.

FIG. 3 shows a control signal for the switching element 41 that is output to the output port 26. The switching element 41 is normally supplied with a pulse signal as shown in FIG. 3(A), and at this time, the switching element 41 becomes conductive every time the pulse signal is generated. On the other hand, for example, during engine acceleration, a signal at a constant level as shown in FIG. 3(B) is supplied to the switching element 41, and at this time the switching element 41 is always maintained in a conductive state. Therefore, when a pulse signal as shown in FIG. 3A is supplied to the switching element 41, the current supplied to the fuel pump 6 becomes relatively small as indicated by L in FIG. The pulse signal shown in FIG. 3(A) is hereinafter referred to as an L signal. On the other hand, when the switching element 41 is supplied with a signal at a constant level as shown in FIG. 3(B), the current supplied to the fuel pump 6 becomes relatively large, as indicated by H in FIG. The signal shown in FIG. 3(B) is hereinafter referred to as an H signal. When the fuel pump 6 is operating normally, L in FIG.
As shown by H, the drive current is lower than the set value A0. However, if the fuel pump 6 is locked, for example, the drive current drops to the set value A0, as shown by K in FIG.
becomes larger than

When the drive current becomes larger than the set value A0, the output voltage of the overcurrent detector 43 becomes a low level as described above, and thereby the output voltage of the latch 44 also becomes a low level, that is, the ground voltage. Therefore, it can be determined from the output voltage of the latch 44 whether or not the fuel pump 6 is locked. However, when the signal line 46 is short-circuited to the ground side, the voltage at the input terminal 47 of the input port 25 becomes the ground voltage. Also,
In the embodiment shown in FIG. 2, input port 25 is input terminal 4.
7 is open, the input terminal 47 is at the ground voltage. Therefore, when the signal line 46 is disconnected, the voltage at the input terminal 47 is at the ground voltage. That is, even if the fuel pump 6 is locked, the signal line 46 is short-circuited, or the signal line 46 is disconnected, the input terminal 47 becomes the ground voltage, and therefore even if the input terminal 47 becomes the ground voltage, the fuel pump 6 is locked or whether there is an abnormality in the signal line 46 cannot be determined.

5 to 9 show a control method for the fuel pump 6 that can determine whether there is an abnormality in the fuel pump 6 or in the signal line 46 when the input terminal 47 becomes the ground voltage. ing. 5 and 6 show the fuel pump 6
This control routine is executed by interrupts at regular intervals. 7 and 8 show time charts when the fuel pump 6 is locked at time t1. As shown in FIGS. 7 and 8, when the fuel pump 6 is locked, the drive current supplied to the fuel pump 6 increases, and when the drive current exceeds the set value A0, the output voltage of the latch 44 goes to the low level L, that is, grounded. Therefore, the input voltage at the input terminal 47 of the input port 25 becomes the ground voltage. On the other hand, FIG. 9 shows a time chart when the signal line 46 is short-circuited to the ground side or disconnected at time t1. As shown in Figure 9, the signal line 4
Even if the signal line 46 is short-circuited or disconnected, the drive current supplied to the fuel pump 6 does not change. However, when the signal line 46 is short-circuited or disconnected, the input voltage at the input terminal 47 of the input port 25 immediately drops to the ground voltage. Note that in FIGS. 7 to 9, time t2 indicates the time when the routine shown in FIGS. 5 and 6 is interrupted. Next, an embodiment of a fuel pump control routine according to the present invention will be described with reference to FIGS. 5 and 6 while referring to time charts shown in FIGS. 7 to 9.

Referring to FIGS. 5 and 6, first, in step 50, it is determined whether there is an abnormality, that is, whether the input terminal 47 of the input port 25 is at ground voltage. If there is no abnormality, the process proceeds to step 51 where the count value C is set to zero, and then the process proceeds to step 52. In step 52, the pump driving process shown in FIG. 6 is performed. Referring to FIG. 6, first, in step 53, it is determined whether flag F is set. Since this flag F is normally reset, the process advances to step 54. In step 54, the difference (
It is determined whether or not P-P1) is greater than or equal to a certain value ΔP0, that is, whether or not the vehicle is in acceleration operation. When the driving is not accelerating, the process proceeds to step 55, where the control signal F for the switching element 41 is set to the L signal shown in FIG.
The control signal F for 1 is the H signal shown in FIG. 3(B). Therefore, it can be seen that when there is no abnormality, the L signal or the H signal is supplied to the switching element 41, and therefore the drive current continues to be supplied to the fuel pump 6. Note that the time charts shown in FIGS. 7 to 9 show the case where the L signal is supplied to the switching element 41 before time t1.

Returning to FIG. 5 again, when it is determined in step 50 that there is an abnormality, that is, when the input voltage at the input terminal 47 of the input port 25 becomes the ground voltage, the process proceeds to step 57 and an abnormality flag is set. It is determined whether the At this time, since the abnormality flag is not set, the process proceeds to step 58, where the control signal F to the switching element 41 is turned off as shown in FIGS. 7 to 9. That is, the switching element 41 is brought into a non-conductive state, and the supply of drive current to the fuel pump 6 is stopped. When the supply of drive current to the fuel pump 6 is stopped, this drive current becomes less than the set value A0, so the output voltage of the overcurrent detector 43 becomes a high level, but the latch 44 outputs a low level output voltage. continue. Therefore, as shown in FIGS. 7 and 8, even if the supply of drive current to the fuel pump 6 is stopped, the input voltage at the input terminal 47 of the input port 25 remains at the ground voltage. Further, as shown in FIG. 9, when the signal line 46 is short-circuited or disconnected, the input voltage of the input terminal 47 of the input port 25 is maintained at the ground voltage after the signal line 46 is short-circuited or disconnected.

Next, in step 59, latch 44 is reset, so that the output voltage of latch 44 goes high. At this time, the output voltage of the overcurrent detector 43 is at a high level, so the output voltage of the latch 44 is maintained at a high level. Therefore, as shown in FIGS. 7 and 8, the signal line 46
If there is no abnormality, the input voltage at the input terminal 47 of the input port 25 becomes a substantially constant voltage at a high level H when the latch 44 is reset. On the other hand, as shown in FIG. 9, when there is an abnormality in the signal line 46 itself, the latch 44 is reset, and even if the output voltage of the latch 44 becomes high level, the input voltage of the input terminal 47 is maintained at the ground voltage. .

Next, in step 60, the control signal F for the switching element 41 is set to the H signal shown in FIG. 3(B). At this time, the drive current of the fuel pump 6 starts to rise as shown in FIGS. 7 to 9. Next, in step 61, it is determined again whether there is an abnormality, that is, whether the input voltage at the input terminal 47 of the input port 25 is the ground voltage. This time is indicated by t3 in FIGS. 7 to 9. At this time, if there is no abnormality in the signal line 46, FIGS.
As shown in , the input voltage of the input terminal 47 is at high level H.
Therefore, it is determined that there is no abnormality, and step 62 is performed.
Proceed to. In step 62, the count value C is incremented by 1, and the process proceeds to step 63. In step 63, it is determined whether or not the count value C has reached a constant value C0. If the count value C has not reached the constant value C0, the process returns to step 62 again. Count value C is constant value C0
When it reaches step 64, it is again determined whether there is an abnormality, that is, whether the input voltage at the input terminal 47 of the input port 25 is the ground voltage. This time is indicated by time t4 in FIGS. 7 and 8.

As described above, when the control signal F to the switching element 41 is set to the H signal in step 60, a stronger driving force than before is applied to the fuel pump 6. Therefore, if a foreign object gets stuck in the fuel pump 6 and the fuel pump 6 becomes locked, by applying a stronger driving force than before, the foreign object can be thrown off and the fuel pump 6 can be returned to a normal state. It can be returned. When the control signal F becomes the H signal and the foreign object is repelled, the image shown in Fig. 7
As shown in , the drive current at time t4 is the set value A0.
will be lower than Therefore, at this time, since the input voltage at the input terminal 47 of the input port 25 is at a high level H at time t4, it is determined that there is no abnormality, and the process proceeds to step 65, where flag F is set. Once the flag F is set, the control signal F is maintained at an H signal in order to proceed from step 53 to step 56 in FIG. That is, if the control signal F is changed to the L signal again after a foreign object has become lodged, that is, if the fuel pump 6 is driven at a low speed, there is a risk that the foreign object may become lodged again and lock the fuel pump. Therefore, once a foreign object is caught, the control signal F is kept at the H signal to continue to apply a strong driving force to the fuel pump 6, thereby preventing it from locking again.

Meanwhile, in step 60, the fuel pump 6
If the foreign object cannot be repelled even if a stronger driving force than before is applied to the fuel pump 6, the fuel pump 6 will continue to be locked. At this time, as shown in FIG. 8, the drive current exceeds the set value A0, so the output voltage of the overcurrent detector 43 changes from a high level to a low level, so that the output voltage of the latch 44 changes to a low level. As a result, the input voltage at the input terminal 47 of the input port 25 becomes the ground voltage. In this way, when the input voltage of the input terminal 47 becomes the ground voltage, it is determined that there is an abnormality at time t4, so the process proceeds to step 66, the control signal F is turned off, and the fuel pump 6
is forced to stop. Then in step 67 the first
The warning light 30 is turned on.

On the other hand, if the signal line 46 is short-circuited or disconnected, the input voltage at the input terminal 47 of the input port 25 is maintained at the ground voltage as shown in FIG. It is determined that In this case, the process proceeds to step 68, where the abnormality flag is set, and then, in step 69, the second warning light 31
is lit, and then the process proceeds to step 52. Once the abnormality flag is set, the process jumps from step 57 to step 52, and the control signal F is controlled according to the routine shown in FIG. That is, when there is an abnormality in the signal line 46, the fuel pump 6 is controlled in the same way as when it is normal.

On the other hand, when the current supplied to the fuel pump 6 is below the set value, the overcurrent detector 43 generates a high level output voltage that is a substantially constant voltage, and the current supplied to the fuel pump 6 is lower than the set value. If the output voltage of the overcurrent detector 43 is lowered to the ground voltage when the voltage exceeds the current value, the latch 44 shown in FIG. 2 can be omitted. In this case, the fuel pump control routine is such that step 59 in FIG. 5 is omitted. FIG. 10 shows a time chart in this case, and this time chart corresponds to FIG. In this case, the control signal F for the switching element 41 is turned off and then turned into an H signal. When the control signal F is turned off, the supply of current to the fuel pump 6 is stopped, so the output voltage of the overcurrent detector 43 immediately becomes a high level. Therefore, if there is no abnormality in the signal line 46, the output high voltage of the input terminal 47 of the input port 25 is at a high level at time t3, and thus it is determined that there is no abnormality in step 61 of FIG. . On the other hand, the signal line 46
If there is an abnormality, the output voltage of the input terminal 47 becomes the ground voltage at time t3, and therefore step 6 in FIG.
1, it will be determined that there is an abnormality.

[0021]

As described above, it is possible to determine whether there is an abnormality in the wiring between the drive current detection means and the drive current supply control means.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the invention.

FIG. 2 is an overall view of the fuel pump control device.

FIG. 3 is a diagram showing control signals for switching elements.

FIG. 4 is a diagram showing drive current.

FIG. 5 is a flowchart for controlling the fuel pump.

FIG. 6 is a flowchart for driving the fuel pump.

FIG. 7 is a time chart of the first embodiment.

FIG. 8 is a time chart of the first embodiment.

FIG. 9 is a time chart of the first embodiment.

FIG. 10 is a time chart of the second embodiment.

[Explanation of symbols]

3...Fuel injection valve 6...Fuel pump 20...Electronic control unit 40...Drive circuit 41...Switching element 42...Current detector 43...Overcurrent detector 44...Latch 46...Signal line

Claims (1)

[Claims] 1. An electric fuel pump, a drive current detection means that outputs a substantially constant voltage when the drive current of the fuel pump is below a predetermined set value, and changes the output voltage when it is above the set value; drive current supply control means for inputting the output voltage and temporarily stopping the supply of the fuel pump drive current when the input voltage changes from the substantially constant voltage, and then restarting the supply of the fuel pump drive current; , further comprising determining means for determining that there is an abnormality in the wiring between the driving current detecting means and the driving current supply controlling means when the input voltage changes from the substantially constant voltage when the driving current supply is resumed. fuel pump control device.