JP4863528B2 - Operation control method for accumulator fuel injector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling operation of an accumulator fuel injection device, controlling rail pressure with high reliability. <P>SOLUTION: In this method for controlling operation, a high-pressure control solenoid valve 11 is provided downstream of a high-pressure pump 2 for pressurizing and feeding fuel in a fuel tank 1 to a common rail 4, and a low-pressure control solenoid valve 7 is provided upstream of the high-pressure pump 2. After fuel temperature is raised by the closed loop control operation of the high-pressure control solenoid valve 11, rail pressure is controlled by the closed loop control operation of the low-pressure control solenoid valve 7. If there is something wrong with the closed loop control operation of the high-pressure control solenoid valve 11, backup control over rail pressure is performed by the low-pressure control solenoid valve 7 without waiting for a fuel temperature rise. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an operation control method for an accumulator fuel injection device.

  In recent years, as one of the fuel injection devices that supply fuel to the engine, the fuel pumped from the high pressure pump is temporarily stored in the common rail, then electrically calculated and stored in the common rail at the set injection timing. An accumulator fuel injection device for an internal combustion engine configured to inject the high-pressure fuel thus injected into a cylinder of an engine from a fuel injection valve has been widely adopted. In a conventional accumulator fuel injector, a high-pressure pump that supplies high-pressure fuel into a common rail is controlled according to the engine speed and the amount of accelerator operation, and the pressure of the high-pressure fuel in the common rail, that is, the rail pressure, is In order to obtain a value commensurate with the driving state of the vehicle, the required injection amount of the driver at that time is calculated according to the engine speed and the accelerator operation amount, and the target rail pressure of the common rail is determined according to the calculation result, The feedback control is performed so that the rail pressure becomes the target rail pressure.

  Therefore, in this type of accumulator fuel injection device, how stable and reliable the rail pressure is set as the target pressure greatly affects the quality of the injection characteristics. Conventionally, in order to maintain this rail pressure at a required value, a method of controlling the rail pressure by providing a low-pressure control solenoid valve upstream of the high-pressure pump and performing open / close control, and a high-pressure on the downstream side of the high-pressure pump. A method of controlling rail pressure by providing a control electromagnetic valve and performing opening / closing control is known. In Patent Document 1, in order to maintain the rail pressure at a required value, a low pressure control solenoid valve is provided upstream of the high pressure pump and a high pressure control solenoid valve is provided downstream of the high pressure pump to control the rail pressure. A method is described. Each of these methods has advantages and disadvantages, and various operation control methods that take into account the respective advantages and disadvantages have been proposed.

JP 2000-303883 A

  However, in any case, if the control solenoid valve for rail pressure control is stuck, the solenoid coil is broken, or for other reasons, rail pressure control becomes impossible and the engine operation stops. As a result, various problems may occur. For this reason, it is desired to improve the reliability of rail pressure control.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an operation control method for a pressure accumulation fuel injection device that can improve the reliability of rail pressure control.

  Another object of the present invention is to provide an operation control method for an accumulator type fuel injection device that can quickly detect a failure in a rail pressure regulator for adjusting rail pressure. is there.

In order to solve the above problems, according to the invention of claim 1, the fuel in the fuel tank is pressurized by the high pressure pump and stored in the common rail, and the high pressure fuel in the common rail is stored in the engine via the fuel injection valve. An operation control method for an accumulator fuel injection device configured to inject and supply into a combustion chamber, wherein a high pressure control solenoid valve is provided downstream of the high pressure pump and a low pressure control solenoid valve is provided upstream of the high pressure pump. After the start of operation, the high pressure control solenoid valve is operated with closed loop control, and the low pressure control solenoid valve is operated with open loop control, and the temperature of the fuel is raised to a predetermined temperature by operation in the first operation mode. Thereafter, the low pressure control solenoid valve is operated in a closed loop control and the high pressure control solenoid valve is operated in a second operation mode in which the high pressure control solenoid valve is operated in an open loop control to control the rail pressure. Thus, when an abnormality occurs in the closed-loop control operation of the high-pressure control solenoid valve, the rail pressure control is performed in the second operation mode without waiting for the fuel temperature to rise to a predetermined temperature. An operation control method for an accumulator fuel injection device characterized in that the operation is performed is proposed.

  According to the invention of claim 2, in the invention of claim 1, whether or not the closed-loop control operation of the high-pressure control solenoid valve is abnormal based on the target rail pressure value and the actual rail pressure value in the first operation mode. There is proposed an operation control method for an accumulator fuel injection device that is configured to determine whether or not.

  According to the invention of claim 3, in the invention of claim 2, it is determined whether or not the closed-loop control operation of the high-pressure control solenoid valve is abnormal after a lapse of a predetermined period from the start of the first operation mode. An operation control method for a pressure accumulating fuel injection apparatus is proposed.

  According to a fourth aspect of the present invention, in the second aspect of the invention, when the state where the difference between the target rail pressure and the actual rail pressure is equal to or greater than a predetermined value continues for a predetermined time or longer, the closed loop control of the high pressure control electromagnetic valve is performed. There is proposed an operation control method for a pressure accumulator type fuel injection device in which the operation is determined to be abnormal.

  According to the invention of claim 5, in the invention of claim 3, it is determined whether or not the predetermined period has passed by whether or not the number of pumping times of the high pressure pump has reached a predetermined value after the start of the closed loop control. The operation control method of the pressure accumulation type fuel injection device thus made is proposed.

  By controlling the rail pressure of the common rail on the downstream side and upstream side of the high-pressure pump, rail pressure control utilizing the features of each control becomes possible, and either one of the closed-loop control operations by the high-pressure or low-pressure control solenoid valve is abnormal In this case, closed loop control of rail pressure is performed using the other control solenoid valve. This backup control can significantly improve the reliability of rail pressure control. In addition, since the operation monitoring for whether or not an abnormality has occurred in the operation of the control solenoid valve is started after a predetermined period has elapsed since the control solenoid valve entered the closed loop control operation, the rail pressure is stabilized. Therefore, it is possible to perform the monitoring, and it is possible to reliably perform the required abnormality determination.

  According to the present invention, as described above, the high pressure control solenoid valve is provided on the downstream side of the high pressure pump and the low pressure control solenoid valve is provided on the upstream side of the high pressure pump, and the rail pressure of the common rail is controlled by the closed loop control operation of the high pressure control solenoid valve. After it is raised, the rail pressure is controlled by the closed-loop control operation of the low-pressure control solenoid valve. When a malfunction occurs in the operation of one control solenoid valve, the rail pressure backup control is performed by the other control solenoid valve. As a result, it is possible to control the occurrence of a state where the fuel supply to the engine becomes impossible, and to control the rail pressure with high reliability.

  In addition, monitoring of each control solenoid valve is started after a predetermined period has elapsed since entering the closed-loop control operation, so that monitoring of rail pressure control by the control solenoid valve is performed while the pressure of the high-pressure fuel in the common rail is substantially stable. Will be started. Therefore, the monitoring can be performed correctly and misjudgments can be reduced.

The block diagram which shows an example of embodiment of the pressure accumulation type fuel-injection apparatus by which driving | operation is controlled by the method of this invention. 2 is a partial flowchart showing an operation control program for operating and controlling the pressure accumulation type fuel injection device having the configuration shown in FIG. 1 according to the method of the present invention. 2 is a partial flowchart showing an operation control program for operating and controlling the pressure accumulation type fuel injection device having the configuration shown in FIG. 1 according to the method of the present invention. 2 is a partial flowchart showing an operation control program for operating and controlling the pressure accumulation type fuel injection device having the configuration shown in FIG. 1 according to the method of the present invention. The flowchart which shows the subroutine program of the forced switching check step shown in FIG. The flowchart which shows the subroutine program of the forced switching check step shown in FIG.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram showing an example of an embodiment of a pressure accumulation type fuel injection device whose operation is controlled by the method of the present invention. The pressure accumulating fuel injection device A shown in FIG. 1 is roughly described in terms of its configuration. Fuel accumulated in the fuel tank 1 is pumped via a high-pressure pump 2 to a common rail 4 to which a plurality of injection nozzles 3 are connected. The operation of a solenoid valve (not shown) built in the injection nozzle 3 is controlled by the control unit 5 so that fuel injection from the injection nozzle 3 is controlled. In the present embodiment, the injection nozzle 3 is attached to each cylinder (not shown) of a multi-cylinder engine for driving the vehicle, and the accumulator fuel injector A burns each cylinder of the vehicle engine. The fuel is injected and supplied into the room.

  Hereinafter, the configuration of the accumulator fuel injection device A will be described more specifically. A fuel pipe 8 is disposed between the fuel tank 1 and the low pressure side of the high pressure pump 2, and in the middle of the fuel pipe 8, in order to remove dust and the like in the fuel in order from the fuel tank 1 side. The filter 6 and the low-pressure control solenoid valve 7 are provided. A fuel temperature sensor 9 is provided at an appropriate position on the fuel pipe 8 between the filter 6 and the low-pressure control solenoid valve 7, and the temperature of the fuel passing through the fuel pipe 8 from the fuel temperature sensor 9. Is output, and the fuel temperature signal SA is input to the control unit 5 described later. In addition, a mechanical low pressure control valve 10 is provided at an appropriate portion of the fuel pipe 8 between the filter 6 and the low pressure control electromagnetic valve 7 so that the fuel pressure in the fuel pipe 8 becomes a predetermined valve opening pressure. Then, the mechanical low pressure control valve 10 is opened, and the fuel in the fuel pipe 8 between the low pressure control electromagnetic valve 7 and the filter 6 is discharged into the fuel tank 1.

  The high pressure side of the high pressure pump 2 is directly connected to the input end 4 </ b> A of the common rail 4 by a fuel pipe 13. The outlet end 4B of the common rail 4 is connected to the fuel tank 1 by a fuel pipe 14 provided with a high pressure control electromagnetic valve 11 in the middle. Further, the common rail 4 is provided with a high pressure sensor 12 for detecting the rail pressure at an appropriate portion, and a rail pressure signal SB indicating the rail pressure output from the high pressure sensor 12 is input to the control unit 5. Has been.

The control unit 5 executes software that will be described later, and controls the operations of the low-pressure control electromagnetic valve 7, the high-pressure control electromagnetic valve 11, and the electromagnetic nozzles (not shown) of the injection nozzle 3. It consists of a microcontroller and various interface circuits. As described above, the fuel temperature signal SA from the fuel temperature sensor 9 and the rail pressure signal SB from the high pressure sensor 12 are input to the control unit 5, and fuel is injected and supplied by the accumulator fuel injection device A. The rotational speed Ne of the engine (not shown), the depression amount Acc of the accelerator pedal (not shown), and the position information Key of a so-called ignition engine key (not shown) used when starting the vehicle are input. .

The low-pressure control solenoid valve 7 and the high-pressure control solenoid valve 11 are provided to set the rail pressure of the common rail 4 to a required value, and both are controlled by the control unit 5. The control mode of each control solenoid valve for rail pressure adjustment by the control unit 5 is as follows:
(1) Control (open loop control) in which only the drive current is output from the control unit 5 to the control solenoid valve, and the difference between the result and the target drive state is not fed back.
(2) The drive current is output from the control unit 5 to the control solenoid valve, and the difference between the result and the target drive state is fed back so that the rail pressure becomes a desired pressure. Control for adjusting the drive current of the control solenoid valve by the control based on the rail pressure signal SB of the high pressure sensor 12 (closed loop control).
It is the structure which can be performed by either.

  2 to 4 are flowcharts showing an operation control program 20 for controlling the operation of the accumulator type fuel injection apparatus A having the configuration shown in FIG. 1 according to the method of the present invention. Examples of operation control according to the present invention will be described with reference to FIGS.

When the execution of the operation control program 20 is started after the engine is started, first, in step S21, the control unit 5 controls the control solenoid valve to fully close the high pressure control solenoid valve 11 and fully open the low pressure control solenoid valve 7. Execute with open loop control. As a result, the amount of high-pressure fuel delivered from the high-pressure pump 2 is maximized and the high-pressure fuel is fed into the common rail 4 without discharging the high-pressure fuel fed from the high-pressure pump 2 from the common rail 4. The fuel pressure inside rises quickly. In step S22, based on the rail pressure signal SB, it is determined whether or not the rail pressure has reached a predetermined pressure P _{0 at} which rail pressure control by the high pressure control electromagnetic valve 11 is to be performed. If the rail pressure has not reached the predetermined pressure P ₀ , the determination result of step S22 is NO and the process returns to step S21. On the other hand, if it is determined that the rail pressure has reached the predetermined pressure P ₀ , the determination result of step S22 is YES, and the process proceeds to step S23.

  In step S23, a counter for the number of times of pumping formed in software in the control unit 5 is reset in order to count the number of times of pumping of fuel by the high-pressure pump 2. Here, the number of times of pumping is counted by increasing the count value by one every time the camshaft of the pump makes one rotation.

  In the next step S24, the high pressure control solenoid valve 11 is switched to the pressure adjustment operation in the closed loop control mode and the low pressure control solenoid valve 7 is switched to the pressure adjustment operation in the open loop control mode, thereby entering the first operation mode. In the first operation mode, for the closed loop control by the high pressure control electromagnetic valve 11, the upper limit value of the rail pressure required in the normal operation of the accumulator fuel injector A is given as the first target rail pressure. The same first target rail pressure is similarly applied to the open loop control of the rail pressure by the control electromagnetic valve 7.

  In the next step S25, it is determined whether or not the count value M of the pumping frequency counter has become larger than the value MA. This value MA is set to the number of times of fuel pumping required until the actual rail pressure substantially converges to the target rail pressure after the control in step S24 is started. The MA value is obtained in advance through experiments or the like. The pump-specific value can be set in the control unit 5.

When the count value M of the pumping number counter is smaller than MA, the determination result of step S25 is NO, and the control state of step S24 is maintained. In this way, the count value M
However, if the actual rail pressure becomes larger than the value MA, which is the number of times of fuel pumping required until the actual rail pressure substantially converges to the target rail pressure, the determination result in step S25 becomes YES, and the process proceeds to step S26. As can be seen from the above description, when the determination result in step S25 is YES, the actual rail pressure is almost converged to the target rail pressure, that is, the high-pressure fuel pressure in the common rail 4 is substantially stable. Yes.

  In step S26, since the stable state of the rail pressure control in which the target rail pressure and the actual rail pressure are substantially equal in the closed loop control by the high pressure control solenoid valve 11 is obtained, the rail pressure control monitoring by the high pressure control solenoid valve 11 is monitored. Is started. The rail pressure control is monitored by checking whether or not the state where the difference between the actual rail pressure and the target rail pressure is equal to or greater than a predetermined value has continued for a predetermined time.

  Thus, after confirming that the number M of fuel pumping by the high-pressure pump 2 has become larger than the predetermined value MA, that is, it is estimated that the pressure of the high-pressure fuel in the common rail 4 is substantially stable. Since the monitoring of the rail pressure control by the high pressure control electromagnetic valve 11 is started after entering the state, the monitoring can be performed correctly, and misjudgments can be reduced.

  Note that the method of setting the predetermined period from when the control switching in step S24 is executed to when monitoring is started is limited to the method based on the count value of the number of times of fuel pumping of the high-pressure pump 2 shown in the present embodiment. However, other methods may be used. For example, when the fluctuation range of the actual rail pressure becomes smaller than a predetermined value, when a predetermined time has elapsed since the switching of the control in step S24, or when the fluctuation range of the engine speed becomes smaller than the predetermined value, the common rail 4 may be a method for estimating that the pressure of the high-pressure fuel in 4 is substantially stable. Alternatively, the above estimation may be performed by appropriately combining these methods. In addition to avoiding false detections by combining several methods in this way, it becomes possible to accurately determine the timing at which monitoring should be started, and the waiting time necessary and sufficient for starting monitoring. You can start monitoring without time loss.

  When the monitoring of the rail pressure control is started as described above, the process proceeds to step S27, where a forced switching check from the high pressure control solenoid valve 11 to the low pressure control solenoid valve 7 is performed. The check here takes into consideration the monitoring result of the rail pressure control started in step S26 and the other check results, and the rail pressure control is changed from the closed loop control operation by the high pressure control solenoid valve 11 to the closed loop control by the low pressure control solenoid valve 7. This is to check whether or not the operation should be forcibly switched.

  FIG. 5 is a flowchart showing a subroutine program for this forced switching check. The forced switching check will be described with reference to FIG.

  In step S41, it is determined whether or not the rail pressure in the common rail 4 has reached a predetermined value or more based on the rail pressure signal SB. If the rail pressure is greater than or equal to the predetermined value, the determination result of step S41 is YES, and step S42 is entered. If the rail pressure is smaller than the predetermined value and not equal to or higher than the predetermined value, the determination result in step S41 is NO, and step S43 is entered. Here, it is determined whether or not the high pressure control solenoid valve 11 is fixed. .

If it is determined in step S43 that the high pressure control solenoid valve 11 is fixed, the determination result in step S43 is YES, and the process proceeds to step S42. If it is determined that the high-pressure control solenoid valve 11 is not fixed, the determination result in step S43 is NO, and step S44 is entered, where it is determined whether or not the high-pressure control solenoid valve 11 has failed. . If it is determined that the high-pressure control solenoid valve 11 has not failed, the determination result of step S44 is NO, and step S45 is entered. If it is determined that the high-pressure control solenoid valve 11 is malfunctioning, the determination result of step S44 is YES, and step S42 is entered.

  In step S42, it is determined whether or not the low-pressure control solenoid valve 7 has failed. This failure determination is performed based on the monitoring result of the rail pressure control executed in step S26. That is, it is performed by checking whether or not the state where the difference between the actual rail pressure and the target rail pressure is equal to or greater than a predetermined value has continued for a predetermined time. If it is determined that the low-pressure control solenoid valve 7 has failed, the determination result of step S42 is YES, and step S45 is entered. If it is determined that the low pressure control solenoid valve 7 has not failed, the determination result of step S42 is NO, and the process proceeds to step S46.

  In step S46, it is determined whether or not the rail pressure is in an abnormal state based on the rail pressure signal SB. If the rail pressure is in an abnormal state, the determination result of step S46 is YES and step S45 is entered. In step S45, it is determined that the condition for switching the control operation from the high pressure control solenoid valve 11 to the low pressure control solenoid valve 7 is not satisfied, the execution of step S27 ends, and the next step S28 is entered. .

  On the other hand, if the rail pressure is not abnormal in step S46, the determination result in step S46 is NO, and step S47 is entered. Here, the high pressure control electromagnetic valve 11 to the low pressure control electromagnetic valve 7 are entered. It is determined that the condition for switching the control operation has been established, the execution of step S27 ends, and the process proceeds to the next step S28.

  That is, when the high-pressure control solenoid valve 11 is not broken, the determination results in steps S41, S43, and S44 are all NO, and the switching condition is not satisfied in step S45. On the other hand, when the high pressure control solenoid valve 11 is in a failure state or a state close to failure, at least one of the determination results in steps S41, S43, and S44 is YES, and in step S42, it is determined whether or not the low pressure control solenoid valve 7 is in failure. If the low-pressure control solenoid valve 7 also fails, the switching condition is not satisfied in step S45. If the low pressure control solenoid valve 7 has not failed, it is determined in step S46 whether or not the rail pressure is abnormal. Only when the rail pressure is not abnormal, the switching condition is determined to be established in step S47.

  In step S28, it is determined whether or not the switching condition is satisfied by the switching check in step S27. If it is determined that the switching condition is not satisfied, the determination result of step S28 is NO and the process proceeds to step S29.

At step S29, whether the fuel temperature Tf on the basis of the fuel temperature signal SA becomes a predetermined value T ₀ or more is determined, the determination result of step S29 in the case of Tf <T ₀ returns NO, to step S26.

When the rail pressure is controlled by the closed loop control by the high pressure control solenoid valve 11 in this way, the fuel temperature rises relatively quickly, and when Tf ≧ T ₀ , the determination result in step S29 becomes YES, Proceed to step S30.

  When the closed-loop control operation of the high-pressure control electromagnetic valve 11 is started in step S24 and the fuel pressure in the common rail 4 is controlled, the rail pressure control is executed with good responsiveness and the temperature rise of the fuel is promoted. It will be. As described above, since the temperature of the fuel can be quickly raised immediately after starting the engine, there is an advantage that the operation of the engine at the time of starting can be quickly stabilized. This is particularly effective in winter when the outside air temperature is low.

When it is determined that the fuel temperature has become equal to or higher than the predetermined value T ₀ in this way, step S3
At 0, the target rail pressure is changed so that the first target rail pressure for performing the closed loop control operation for the rail pressure control by the high pressure control electromagnetic valve 11 is set to another lower second target rail pressure.

  In step S31, it is determined whether or not a predetermined time has elapsed since the change of the target rail pressure in step S30. If it is determined that the predetermined time has not elapsed, the determination result of step S31 is NO, and the process returns to step S30. Thus, when the closed loop control by the second target rail pressure is performed for a predetermined time, it is determined that the actual value of the rail pressure has substantially converged to the second target rail pressure by the control after the change of the target rail pressure. The determination result is YES, and the process proceeds to step S32.

  In step S32, the pumping frequency counter is reset, and in the next step S33, the low pressure control solenoid valve 7 is set to the closed loop control mode, thereby maintaining the rail pressure of the common rail 4 at the target rail pressure corresponding to the operation conditions at that time. While switching to the pressure adjustment operation, the second operation mode is set by switching to the open loop control mode in which the high pressure control solenoid valve 11 is fully closed. Thereafter, the rail pressure control is performed in the second operation mode, and the rail pressure control is performed by the closed loop control of the low pressure control solenoid valve 7 so that the rail pressure in the common rail 4 is maintained at the target rail pressure according to the operation conditions at that time. Is called. The target rail pressure according to this operating condition can be calculated based on parameters such as engine speed, target injection amount, rail pressure, engine coolant temperature (water temperature), fuel temperature (fuel temperature), etc. By controlling the rail pressure in the closed loop control mode by the low pressure control solenoid valve 7 using the target rail pressure obtained by considering such parameters, the value of the rail pressure can be set to an optimum value.

As described above, after the engine is started, the high pressure control solenoid valve 11 is fully closed and the low pressure control solenoid valve 7 is fully opened to quickly increase the fuel pressure in the common rail 4 to the predetermined value P _0. Is operated in the closed loop control mode to raise the fuel temperature early, and the rail pressure is converged to the first target rail pressure with good response, and the fuel temperature has reached a predetermined value T ₀ necessary for stable engine operation. If so, it is configured to shift to rail pressure control by closed-loop control of the low-pressure control solenoid valve 7 without a large increase in fuel temperature. As a result, the rail pressure can be increased to a pressure at which stable operation can be achieved quickly while increasing the fuel temperature at the start of the engine. The switching from the closed loop control operation by the high pressure control solenoid valve 11 to the closed loop control operation of the low pressure control solenoid valve 7 is performed by performing the closed loop control operation by the high pressure control solenoid valve 11 for a predetermined time while the target rail pressure is once lowered. Therefore, the switching of the control operation can be performed very smoothly without causing an overshoot of the rail pressure, and the rail pressure is not greatly changed by the switching. Therefore, the operation of the engine is stably performed under a constant rail pressure regardless of the switching of the control operation, and good operating characteristics can be ensured. In addition, since this control does not require the addition of parts, the cost does not increase.

  In step S34, it is determined whether or not the count value M of the pumping number counter has become larger than the value MB. This value MB is the number of times of fuel pumping required until the actual rail pressure of the common rail 4 substantially converges to the target rail pressure according to the operation conditions at that time after the control in the second operation mode in step S33 is started. The value of MB can be set in the control unit 5 in advance as the value of MB.

When the count value M of the pumping number counter is smaller than MB, the determination result of step S34 is NO, and the control state of step S33 is maintained. In this way, when the count value M increases and the actual rail pressure becomes larger than the fuel pumping number MB required until the actual rail pressure substantially converges to the target rail pressure according to the operation condition at that time, the determination result in step S34 becomes YES. The process proceeds to step S35. As can be seen from the above description, the determination result in step S34 is YES.
When this happens, the actual rail pressure is almost converged to the target rail pressure according to the operating conditions at that time, that is, the pressure of the high-pressure fuel in the common rail 4 is substantially stable.

  In step S35, in the closed-loop control by the low-pressure control solenoid valve 7, the stable state of the rail pressure control in which the target rail pressure and the actual rail pressure according to the operation conditions at that time are substantially equal is obtained. Monitoring of rail pressure control is started.

  When the monitoring of the rail pressure control is started as described above, the process proceeds to step S36, where a forced switching check from the low pressure control solenoid valve 7 to the high pressure control solenoid valve 11 is performed. The check here takes into consideration the monitoring result of the rail pressure control started in step S35 and the other check results, and the rail pressure control is forced from the closed loop control operation by the low pressure control solenoid valve 7 to the high pressure control solenoid valve 11. It is checked whether or not to switch to a closed-loop control operation by.

  FIG. 6 is a flowchart showing a subroutine program for this forced switching check. The forced switching check will be described with reference to FIG.

  In step S51, it is determined whether or not the rail pressure in the common rail 4 has reached a predetermined value or more based on the rail pressure signal SB. If the rail pressure is equal to or higher than the predetermined value, the determination result of step S51 is YES, and the process enters step S52. If the rail pressure is smaller than the predetermined value and not equal to or higher than the predetermined value, the determination result in step S51 is NO, and step S53 is entered. Here, it is determined whether or not the low pressure control solenoid valve 7 is fixed. .

  If it is determined in step S53 that the low pressure control solenoid valve 7 is fixed, the determination result in step S53 is YES, and the process proceeds to step S52. If it is determined that the low-pressure control solenoid valve 7 is not fixed, the determination result in step S53 is NO, and step S54 is entered, where it is determined whether or not the low-pressure control solenoid valve 7 has failed. . If it is determined that the low pressure control solenoid valve 7 has not failed, the determination result of step S54 is NO, and the process proceeds to step S55. If it is determined that the low-pressure control solenoid valve 7 is out of order, the determination result of step S54 is YES, and the process proceeds to step S52.

  In step S52, it is determined whether or not the high-pressure control solenoid valve 11 has failed. This failure determination is performed based on the monitoring result of the rail pressure control executed in step S35. That is, it is performed by checking whether or not the state where the difference between the actual rail pressure and the target rail pressure is equal to or greater than a predetermined value has continued for a predetermined time. If it is determined that the high-pressure control solenoid valve 11 has failed, the determination result of step S52 is YES, and the process proceeds to step S55. If it is determined that the high-pressure control solenoid valve 11 has not failed, the determination result of step S52 is NO, and step S56 is entered.

  In step S56, it is determined whether or not the rail pressure is in an abnormal state based on the rail pressure signal SB. If the rail pressure is in an abnormal state, the determination result of step S56 is YES, and the process proceeds to step S55. In step S55, it is determined that the condition for switching the control operation from the low pressure control solenoid valve 7 to the high pressure control solenoid valve 11 is not satisfied, the execution of step S36 is finished, and the next step S37 is entered. .

  On the other hand, if the rail pressure is not in an abnormal state in step S56, the determination result in step S56 is NO, and step S57 is entered. In step S57, it is determined that a condition for switching the control operation from the low pressure control solenoid valve 7 to the high pressure control solenoid valve 11 is satisfied, the execution of step S36 is terminated, and the process proceeds to the next step S37.

  That is, when the low-pressure control solenoid valve 7 is not broken, the determination results of steps S51, S53, and S54 are all NO, and the switching condition is not satisfied in step S55. On the other hand, if the low-pressure control solenoid valve 7 is in a failure state or a state close to failure, at least one of the determination results in steps S51, S53, and S54 is YES, and whether or not the high-pressure control solenoid valve 11 is in failure is determined in step S52. Thus, if the high pressure control solenoid valve 11 also fails, it is determined in step S55 that the switching condition is not satisfied. If the high pressure control solenoid valve 11 is not broken, it is determined in step S56 whether or not the rail pressure is abnormal. Only when the rail pressure is not abnormal, the switching condition is established in step S57.

  In step S37, it is determined whether or not the switching condition is satisfied by the switching check in step S36. If it is determined that the switching condition is not satisfied, the determination result of step S37 is NO, and the process returns to step S35.

  On the other hand, if it is determined in step S37 that the switching condition is satisfied by the switching check in step S36, the determination result in step S37 is YES, and the process returns to step S23.

  Similarly, if it is determined in step S28 that the switching condition is satisfied, the determination result is YES, and step S32 is entered, where the pumping frequency counter is reset. In step S33, the low pressure control electromagnetic valve 7 is switched to the closed loop control mode, thereby performing backup control for maintaining the rail pressure of the common rail 4 at a required target rail pressure.

  As described above, the pressure accumulation type fuel injection device A is controlled in the first operation mode after the start in which the rail pressure of the common rail 4 is controlled, and then switched to the second operation mode at a predetermined timing. Rail pressure is controlled. In these rail pressure controls, it is checked in steps S27 and S36 whether the required control solenoid valve is normally performing the closed loop control operation as scheduled.

  As a result, in the first operation mode, it is determined that the operation of the high pressure control solenoid valve 11 is not normally performed, and if the low pressure control solenoid valve 7 is normal, the switching condition is established, and the second operation is determined. The mode is switched to rail pressure control by mode, and backup control by this is started.

  On the other hand, when it is determined that the operation of the low pressure control solenoid valve 7 is not normally performed in the second operation mode and the high pressure control solenoid valve 11 is normal, the switching condition is determined to be satisfied, and the first operation mode is determined. The control is switched to the rail pressure control by and the backup control by this is started.

  As described above, when the control solenoid valve is provided on the upstream side and the downstream side of the high-pressure pump 2 and the rail pressure is controlled by switching the control solenoid valve, when one of the control solenoid valves does not operate normally, Is configured to perform a backup operation using the other control solenoid valve, so that the occurrence of a situation in which engine fuel supply becomes impossible can be suppressed to a very low level, thereby controlling rail pressure with high reliability. Can do.

  Each control solenoid valve is monitored after confirming that the fuel pumping frequency M by the high-pressure pump 2 has become larger than a predetermined value MA, that is, when the pressure of the high-pressure fuel in the common rail 4 is substantially stable. Since the monitoring of the rail pressure control by the high pressure control electromagnetic valve 11 is started after entering the state estimated to be in the state, the monitoring can be performed correctly, and erroneous determination can be reduced.

  As described above, the operation control method for an accumulator fuel injection device according to the present invention is useful for performing rail pressure control operation with high reliability.

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 High pressure pump 3 Injection nozzle 4 Common rail 5 Control unit 6 Filter 7 Low pressure control solenoid valve 8, 13, 14 Fuel pipe 9 Fuel temperature sensor 10 Mechanical low pressure control valve 11 High pressure control solenoid valve 12 High pressure sensor 20 Operation control Program A Accumulated fuel injection device Acc Depression amount Ne Speed Key Position information SA Fuel temperature signal SB Rail pressure signal

Claims (5)

A pressure accumulation type fuel injection device configured to pressurize fuel in a fuel tank with a high pressure pump and store it in a common rail, and inject and supply the high pressure fuel in the common rail into a combustion chamber of an engine via a fuel injection valve The operation control method of
A high-pressure control solenoid valve is provided on the downstream side of the high-pressure pump and a low-pressure control solenoid valve is provided on the upstream side of the high-pressure pump. After the start of operation, the high-pressure control solenoid valve is operated in closed loop control and the low-pressure control solenoid valve is opened. After the temperature of the fuel is raised to a predetermined temperature by operation in the first operation mode operated by loop control, the low pressure control solenoid valve is operated by closed loop control and the high pressure control solenoid valve is operated by open loop control. The operation is switched to the operation in the second operation mode to control the rail pressure, and when an abnormality occurs in the closed loop control operation of the high pressure control solenoid valve, the temperature of the fuel rises to a predetermined temperature. An operation control method for an accumulator fuel injection device, wherein the rail pressure is controlled in the second operation mode without waiting for the operation. The accumulator fuel injection according to claim 1, wherein whether or not the closed-loop control operation of the high-pressure control solenoid valve is abnormal is determined based on a target rail pressure value and an actual rail pressure value in the first operation mode. Device operation control method. The operation of the accumulator fuel injection device according to claim 2, wherein it is determined whether or not the closed-loop control operation of the high-pressure control solenoid valve is abnormal after a lapse of a predetermined period from the start of the first operation mode. Control method. 3. The closed-loop control operation of the high pressure control solenoid valve is determined to be abnormal when a state where a difference between the target rail pressure and the actual rail pressure is equal to or greater than a predetermined value continues for a predetermined time or longer. An operation control method for an accumulator fuel injection device. The operation control of the pressure accumulation type fuel injection device according to claim 3, wherein whether or not the predetermined period has elapsed is determined based on whether or not the number of pumping of the high pressure pump has reached a predetermined value after the closed loop control is started. Method.

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