JP5799919B2 - Pump control device - Google Patents

Description

  The present invention relates to a pump control device that controls a metering valve installed in each of a plurality of plungers to meter a discharge amount of a fuel supply pump.

  It is known to control the electromagnetically driven metering valve to meter the discharge amount of the fuel supply pump (see, for example, Patent Document 1). Patent Document 1 discloses a technique for reducing the discharge amount of a fuel supply pump by controlling a metering valve when performing a reduced-cylinder operation that reduces the number of cylinders that inject fuel in a multi-cylinder engine.

  Also in the fuel supply pump, for example, when an abnormality is detected in a part of the metering valves installed in each of the plurality of plungers, the energization control to the abnormal metering valves is stopped and the fuel is discharged from the corresponding plungers. Control to stop may be performed. If there is a plunger for stopping fuel discharge, the discharge amount of the fuel supply pump is insufficient with respect to the required discharge amount. In this case, in the conventional discharge amount control, the shortage of the discharge amount of the fuel supply pump is compensated by feedback control.

JP 2000-110612 A

  However, even if the discharge amount control by feedback control is performed in a state where there is a plunger for stopping fuel discharge, the actual discharge amount (hereinafter also referred to as “actual discharge amount”) is insufficient with respect to the required discharge amount. There is a problem that the responsiveness of the actual fuel pressure (hereinafter also referred to as “actual fuel pressure”) with respect to the target fuel pressure is low. Further, since the actual discharge amount is insufficient with respect to the required injection amount, the feedback integral term becomes excessively large, and the fuel pressure may overshoot the target fuel pressure.

  The present invention has been made to solve the above-described problem. Even when fuel discharge from some of the plungers stops, the response of the actual fuel pressure to the target fuel pressure is high, and the overshoot of the fuel pressure is prevented. An object of the present invention is to provide a pump control device for preventing the above.

  According to the pump control device of the present invention, the injection pumping ratio, which is the ratio of the number of injections of the fuel injection valve and the number of pumping of the fuel supply pump, is calculated. Excludes the plunger from which fuel discharge stops. Note that the number of pumping times of the fuel supply pump represents the number of fuel discharges from the plunger.

Then, based on the injection pumping ratio, the metering valve operates to distribute the discharge amount of the fuel supply pump to the plunger that discharges the fuel.
When the discharge amount is distributed, it is controlled by feedforward control that controls the discharge amount of the fuel supply pump based on the injection amount from the fuel injection valve and the differential pressure between the target pressure of the fuel pressure and the actual fuel pressure. The injection amount is multiplied by the discharge amount controlled by feedback control that controls the discharge amount of the fuel supply pump based on the differential pressure between the previous fuel pressure and the current fuel pressure. The discharged amount is distributed to the plunger that operates the metering valve to discharge the fuel.
As a result, the amount of discharge from the plunger that stops the operation of the metering valve and does not discharge fuel can be distributed to the plunger that operates the metering valve and discharges fuel. The shortage of discharge amount can be solved. As a result, the response of the actual fuel pressure to the target fuel pressure is improved. Furthermore, since the feedback integral term can be prevented from becoming excessively large, it is possible to prevent the fuel pressure from overshooting the target fuel pressure.

  The functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.

The block diagram which shows the fuel-injection system by this embodiment. The time chart which shows the relationship between the injection at normal time and the time of a partial stop, and discharge. The other time chart which shows the relationship between the injection at normal time and the time of a partial stop, and discharge. (A) is a time chart which shows the change of the rail pressure of this embodiment and a comparative example, (B) is a time chart which shows the change of F / B integral term. The flowchart which shows discharge amount control processing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Fuel injection system)
A fuel injection system 10 shown in FIG. 1 is for injecting fuel into, for example, a four-cylinder diesel engine (hereinafter also simply referred to as “engine”) 2 for an automobile. The fuel injection system 10 includes a fuel supply pump 14, a common rail 20, a fuel injection valve 30, and an electronic control unit (ECU) 40.

  The fuel supply pump 14 incorporates a feed pump that pumps fuel from the fuel tank 12. The fuel supply pump 14 is provided with a plurality of plungers, and a known pump that pressurizes and feeds fuel sucked from the feed pump into the pressurizing chamber by reciprocating the plunger as the camshaft cam rotates. It is. The fuel supply pump 14 of the present embodiment includes two plungers.

  The metering valve 16 serving as a metering actuator is a solenoid valve that closes when energized, and one metering valve is installed for each plunger. By adjusting the valve closing timing of the metering valve 16 in the pressure feed stroke of the fuel supply pump 14, the amount of discharge from each plunger is metered. When energization to the metering valve 16 is stopped, the metering valve 16 does not close, so that fuel is not discharged from the corresponding plunger.

  The common rail 20 is a hollow member that forms a pressure accumulating chamber that accumulates fuel pumped from the fuel supply pump 14. The common rail 20 is provided with a pressure sensor 22 that detects internal fuel pressure (rail pressure), and a pressure reducing valve 24 that discharges fuel from the common rail 20 to reduce the rail pressure.

  The engine 2 is provided with a rotation angle sensor 32 that generates a rotation angle signal for each predetermined rotation angle of the engine 2 as a sensor for detecting an operation state. The ECU 40 calculates the engine speed based on the rotation angle signal output by the rotation angle sensor 32 at every predetermined rotation angle. Therefore, the rotation angle sensor 32 functions as a rotation speed sensor.

  Further, in the fuel injection system 10, as other sensors for detecting the driving state, an accelerator sensor for detecting an accelerator opening (ACCP) which is an operation amount of an accelerator pedal by a driver, a temperature (water temperature) of cooling water, and intake air. A temperature sensor or the like for detecting the temperature (intake air temperature) is provided.

  The fuel injection valve 30 is installed in each cylinder of the engine 2 and injects fuel accumulated in the common rail 20 into the cylinder. The fuel injection valve 30 is, for example, a known electromagnetically driven valve that controls the lift of the nozzle needle that opens and closes the nozzle hole with the pressure in the control chamber. The injection amount of the fuel injection valve 30 is controlled by the pulse width of the injection command signal commanded from the ECU 40. As the pulse width of the injection command signal increases, the injection amount increases.

  The ECU 40 is mainly configured by a microcomputer centering on a CPU, RAM, ROM, flash memory and the like. The ECU 40 executes various control of the fuel injection system 10 based on output signals taken from various sensors including the pressure sensor 22 and the rotation angle sensor 32 when the CPU executes a control program stored in the ROM or the flash memory. Run.

For example, the ECU 40 controls the discharge amount of the fuel supply pump 14 by controlling the timing at which the metering valve 16 is energized and closed.
In addition, the ECU 40 stores a so-called TQ map indicating the correlation between the pulse width (T) of the injection command signal for instructing the fuel injection valve 30 and the injection amount (Q) for each predetermined pressure region of the rail pressure in the ROM or Stored in flash memory. Then, when the target injection amount of the fuel injection valve 30 is determined based on the engine speed and the accelerator opening, the ECU 40 refers to the TQ map of the corresponding pressure region according to the rail pressure detected by the pressure sensor 22. The pulse width of the injection command signal for commanding the target injection amount to the fuel injection valve 30 is acquired from the TQ map.

(Injection pumping ratio)
Next, the injection pumping ratio used for the discharge amount control of the fuel supply pump 14 will be described. The injection pumping ratio represents the ratio between the number of injections of the fuel injection valve 30 and the number of pumping of the fuel supply pump 14 representing the number of fuel discharges from the plunger.

  As shown in FIG. 2A, in the normal time when the two metering valves 16 operate, the fuel injection valve 30 performs a single injection near the top dead center (TDC) of the corresponding cylinder of the engine 2. When pumping once from the fuel supply pump 14 during the period, the injection pumping ratio is 1.

  On the other hand, as shown in FIG. 2B, when one of the two metering valves 16 is de-energized due to an abnormality or the like, and fuel discharge from the corresponding plunger is stopped, the fuel injection valve In the control period in which 30 is injected twice, the fuel supply pump 14 pumps the fuel once, so the injection pumping ratio is 2.

  Further, as shown in FIG. 3A, the fuel injection valve 30 injects once near the top dead center (TDC) of the corresponding cylinder of the engine 2 at the normal time when the two metering valves 16 are operated. When pumping twice from the fuel supply pump 14 during the control period, the injection pumping ratio is 0.5.

  On the other hand, as shown in FIG. 3B, when one of the two metering valves 16 is deenergized due to an abnormality or the like and the fuel discharge from the corresponding plunger is stopped, the fuel injection valve Since the fuel supply pump 14 pumps the fuel once in the control period in which 30 is injected once, the injection pumping ratio becomes 1.

  That is, in FIGS. 2 and 3, when the fuel discharge from one of the two plungers is stopped, the injection pumping ratio is doubled. Therefore, when the discharge amount of the fuel supply pump 14 is distributed based on the injection pumping ratio, the discharge amount commanded to the plunger for operating the metering valve 16 to discharge the fuel is doubled.

  As described above, in this embodiment, when the fuel discharge from some of the plungers is stopped, the plunger for stopping the fuel discharge is calculated based on the injection pumping ratio calculated by excluding the plunger for stopping the fuel discharge from the target of the number of times of pumping. Is distributed to the plunger for discharging the fuel. Therefore, the discharge amount from the plunger that discharges the fuel increases.

  On the other hand, when the discharge amount from the plunger that stops fuel discharge is not distributed to the plunger that discharges fuel without considering the plunger that stops fuel discharge, the discharge amount required for the fuel supply pump 14 The amount of discharge from the plunger that discharges fuel is insufficient.

  FIG. 4A shows the rail pressure change characteristic 210 of the present embodiment when the fuel discharge from one of the two plungers is stopped with respect to the target rail pressure, and the discharge from the plunger that stops the fuel discharge. The rail pressure change characteristic 212 of the comparative example which does not distribute quantity to the plunger which discharges fuel is shown. Reference numeral 200 indicates a change characteristic of the rail pressure when fuel is discharged from both of the two plungers.

  FIG. 4A shows an example in which full discharge is commanded to the metering valve 16 halfway because the required discharge amount to the fuel supply pump 14 is large. Therefore, the fuel is supplied from both of the two plungers. Is more responsive than the change characteristic 210 of this embodiment and the change characteristic 212 of the comparative example in which fuel is discharged from only one plunger. In addition, during the period in which the full discharge is commanded, the responsiveness between the change characteristic 210 of the present embodiment and the change characteristic 212 of the comparative example hardly changes.

  However, when the differential pressure between the target rail pressure and the actual rail pressure is reduced and the discharge amount required for the fuel supply pump 14 is reduced, the comparison does not distribute the discharge amount from the plunger that stops fuel discharge to the plunger that discharges fuel. In the example, the discharge amount commanded to one plunger is smaller than the total discharge amount.

  On the other hand, in the present embodiment in which the discharge amount of the plunger that stops the fuel discharge is distributed to the plunger that discharges the fuel, the full amount discharge is continued longer than the comparative example. As a result, the actual rail pressure reaches the target rail pressure more quickly in the change characteristic 210 of the present embodiment than in the change characteristic 212 of the comparative example.

  Further, in FIG. 4A, control is employed in which an integral term of feedback (F / B) control is not calculated when commanding full discharge. Therefore, in this embodiment in which the full rail discharge is controlled until the actual rail pressure approaches the target rail pressure, the integral term is hardly accumulated as shown by the integral term change characteristic 220 in FIG. As a result, in this embodiment, it is possible to prevent the rail pressure from overshooting when the actual rail pressure approaches the target rail pressure.

  On the other hand, in the comparative example, when the actual rail pressure approaches the target rail pressure, the timing at which the discharge of the entire amount ends is earlier than in this embodiment, and the F / B integral term is calculated. The integral term is integrated as the actual rail pressure approaches the target rail pressure, as shown by the integral term change characteristic 222 shown. As a result, in the comparative example, the rail pressure may overshoot when the actual rail pressure approaches the target rail pressure.

  Even in the case where the integral term of the F / B control is calculated even if the entire amount is discharged, the present embodiment continues the full amount discharge longer than the comparative example. Further, even when the required discharge amount for the fuel supply pump 14 decreases and the command discharge amount for each plunger is smaller than the total discharge amount, the present embodiment has a larger discharge amount from the plunger than the comparative example. The difference between the required discharge amount for the pump 14 and the actual discharge amount is small.

  Thereby, the responsiveness of the actual rail pressure with respect to the target rail pressure is higher in the present embodiment than in the comparative example. As a result, since the integral term of the F / B control is smaller in the present embodiment than in the comparative example, it is possible to prevent the rail pressure from overshooting when the actual rail pressure approaches the target rail pressure.

(Discharge rate control process)
Next, the discharge amount control process executed by the ECU 40 will be described. The flowchart of FIG. 5 is executed at a predetermined cycle. In FIG. 5, “S” represents a step.

  The ECU 40 acquires the rail pressure from the output signal of the pressure sensor 22 (S400), and calculates the engine speed from the output signal of the rotation angle sensor 32 (S402). Then, the injection amount from the fuel injection valve 30 is calculated based on the engine speed and the accelerator opening (S404), and the target rail pressure is calculated (S406).

  When there is a plunger that does not discharge fuel because the current supply to the metering valve 16 is stopped and the operation of the metering valve 16 is stopped (S408: Yes), the ECU 40 will be described with reference to FIGS. As described above, the injection pumping ratio is calculated in the control period (S410), and the process proceeds to S412.

  As one of the reasons that the current supply to the metering valve 16 is stopped and the operation of the metering valve 16 is stopped, there is an abnormality in the electric system that controls the current supply to the metering valve 16. It is conceivable to stop energization of the.

  As another cause, when the injection amount of the fuel injection valve 30 is small and the required discharge amount to the fuel supply pump 14 is equal to or less than a predetermined amount, the ECU 40 may stop energizing some of the metering valves 16. . In this case, power consumption can be reduced by stopping the energization control to some of the metering valves 16.

  On the other hand, when the operation of all the metering valves 16 is normal and there is no plunger that does not discharge fuel (S408: No), the ECU 40 proceeds to S412 without changing the injection pumping ratio.

  In S412, the ECU 40 determines from the fuel injection amount set by the engine speed and the accelerator opening, the differential pressure between the target rail pressure and the actual rail pressure detected by the pressure sensor 22, and the fuel leak amount of the fuel injection system 10. The discharge amount required for the fuel supply pump 14 is calculated by feed forward (F / F) control.

Further, the ECU 40 calculates a discharge amount required for the fuel supply pump 14 by F / B control based on the differential pressure between the current rail pressure and the previous rail pressure (S414).
And the command discharge amount with respect to the plunger which discharges a fuel is calculated by multiplying the discharge amount requested | required of the fuel supply pump 14 which added the discharge amount calculated by S412 and S414 by the injection pressure sending ratio (S416).

  As described above, in the present embodiment, when there is a plunger for stopping the fuel discharge, by multiplying the discharge amount required for the fuel supply pump 14 by the injection pumping ratio without changing the control logic, The discharge amount from the plunger that stops the fuel discharge by stopping the operation of some of the metering valves 16 is distributed to the plunger that discharges the fuel.

  Thereby, even if there is a plunger that does not discharge fuel, the shortage of discharge amount can be solved. As a result, the response of the actual rail pressure to the target rail pressure is improved. Furthermore, since the integral term of the F / B control can be prevented from becoming excessively large, it is possible to prevent the fuel pressure from overshooting the target pressure.

[Other Embodiments]
The number of plungers of the fuel supply pump 14 is not limited to two as long as it is plural, and may be three or more. Also in this case, a configuration is employed in which the metering valve 16 installed for each plunger regulates the discharge amount from each plunger. If there is a plunger that stops the fuel discharge because the operation of the metering valve 16 is stopped, the injection pumping ratio is calculated by removing the plunger that stops the fuel discharge from the target of the number of times of pumping.

  As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

14: fuel supply pump, 16: metering valve, 30: fuel injection valve, 40: ECU (pump control device, discharge amount setting means, determination means, calculation means, discharge amount distribution means, metering valve control means, feed forward Control means, feedback control means)

Claims (1)

Pump control for metering the discharge amount of a fuel supply pump (14) that pressurizes and pumps fuel sucked by reciprocating movement of a plurality of plungers by controlling a metering valve (16) installed for each plunger. A device (40) comprising:
Discharge amount setting means (S412, S414) for setting the discharge amount of the fuel supply pump;
A determination unit (S408) for determining whether or not there is the plunger in which the operation of some of the metering valves among the plurality of metering valves is stopped and fuel discharge is stopped;
An injection pumping ratio, which is a ratio between the number of injections of the fuel injection valve (30) for injecting fuel pumped by the fuel supply pump and the number of pumping of the fuel supply pump, is calculated, When the determination means determines that it exists, calculation means (S410) excluding the plunger from which fuel discharge stops from the target of the number of pumping times;
Discharge amount distribution means (S416) for distributing the discharge amount set by the discharge amount setting means to the plunger for operating the metering valve to discharge fuel based on the injection pressure ratio calculated by the calculation means; ,
A metering valve control unit (S408) that stops the operation of some of the metering valves when the abnormal metering valve operation is stopped and the discharge amount set by the discharge amount setting unit is a predetermined amount or less; ,
Equipped with a,
The discharge amount setting means feed-forward control means (S412) for controlling the discharge amount of the fuel supply pump based on the injection amount from the fuel injection valve and the differential pressure between the target pressure of the fuel pressure and the actual fuel pressure. ) And feedback control means (S414) for controlling the discharge amount of the fuel supply pump based on the differential pressure between the previous fuel pressure and the current fuel pressure,
The discharge amount distribution means multiplies the discharge amount controlled by the feedforward control means and the discharge amount controlled by the feedback control means by the injection pressure ratio, and multiplies the metering valve. Calculates the command discharge amount for the plunger that operates to discharge the fuel,
A pump control device characterized by that.

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