JP5672163B2 - Fuel pump control device - Google Patents

Description

  The present invention relates to a pressure accumulating container capable of accumulating fuel in a high pressure state, a fuel injection valve for directly injecting fuel supplied from the pressure accumulating container to a combustion chamber of an internal combustion engine, and fuel from a fuel tank to the pressure accumulating container. The present invention relates to a control device for a fuel pump applied to a fuel injection system for an internal combustion engine, which includes a fuel pump for supplying and discharging and a fuel pressure detecting means for detecting a fuel pressure of the pressure accumulating vessel.

  As this type of control device, as can be seen in the following Patent Document 1, an electronically controlled expression that the fuel pump has to control the detected value (actual fuel pressure) of the fuel pressure sensor that detects the fuel pressure of the pressure accumulator vessel to the target value. One that energizes the actuator is known. Such control is performed in order to improve the combustion state of the internal combustion engine.

JP 2007-32323 A

  By the way, when the vehicle is decelerated, fuel cut control for stopping fuel injection from the fuel injection valve may be performed. When the fuel cut control is performed, the fuel supply from the pressure accumulating vessel to the combustion chamber is stopped, so that the fuel pump discharge amount required to control the actual fuel pressure to the target value tends to decrease. When the discharge amount of the fuel pump decreases, the time that the fuel pumped up by the fuel pump stays in the fuel pump becomes longer, and the time that the fuel is heated from the surroundings in the fuel pump becomes longer. When the heating time of the fuel becomes longer, the fuel temperature in the fuel pump becomes higher, and fuel bubbles (vaporization) may occur in the fuel pump.

  Here, in a situation where the fuel cut control is canceled and the fuel pump discharge command is issued, if the fuel is bubbled in the fuel pump, the fuel pump discharge amount may be excessively reduced. There is a possibility that the discharge amount of the pump cannot be adjusted appropriately. In this case, there is a possibility that the controllability of the actual fuel pressure may be lowered, for example, it becomes impossible to quickly increase the actual fuel pressure to the target value after canceling the fuel cut control.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for a fuel pump that can suitably suppress a decrease in fuel pressure controllability of an accumulator vessel.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

According to a first aspect of the present invention, there is provided a pressure accumulating container capable of accumulating fuel in a high pressure state, a fuel injection valve for directly injecting fuel supplied from the pressure accumulating container into a combustion chamber of an internal combustion engine, and the pressure accumulating fuel from a fuel tank. The present invention is applied to a fuel injection system of an internal combustion engine including a fuel pump for supplying and discharging to a container and a fuel pressure detecting means for detecting a fuel pressure of the pressure accumulating container, and the fuel pump includes an electronically controlled actuator and energizes the actuator And operating means for energizing the actuator to control the fuel pressure detected by the fuel pressure detecting means to its target value, and the fuel pump. Based on the fact that the fuel cut control for stopping the fuel injection from the fuel injection valve is being executed, and the fuel temperature in the inside is higher than the specified temperature, Characterized in that it comprises a forced energization stopping means for forcibly stopping the current supply to the actuator.

  Normally, when the actuator is energized to discharge fuel from the fuel pump, the fuel temperature in the fuel pump rises. This is because the actuator generates heat due to energization of the actuator or the fuel is compressed in the fuel pump. And if the fuel temperature in a fuel pump becomes high, bubbling of the fuel in a fuel pump may be accelerated | stimulated during execution of fuel cut control.

  Here, in the above invention, the energization of the actuator is forcibly stopped based on the fact that the fuel temperature in the fuel pump is equal to or higher than the specified temperature and the fuel cut control is being executed. For this reason, in a situation where the fuel temperature in the fuel pump is high and the fuel cut control is executed and the residence time of the fuel in the fuel pump becomes long (in other words, the fuel is bubbled) In a highly probable situation, the fuel in the fuel pump can be prevented from being heated. Thereby, generation | occurrence | production of the bubble of the fuel in a fuel pump can be suppressed, and the fall of the fuel pressure controllability of an accumulator can be suppressed suitably by extension.

In a second aspect based on the first aspect , the forced energization stop means does not forcibly stop energization of the actuator based on the fact that the fuel temperature in the fuel pump becomes lower than the specified temperature. It is characterized by that.

According to a third invention, in the first or second invention, the fuel pressure detected by the fuel pressure detecting means is not more than a specified pressure in a situation where energization to the actuator is forcibly stopped by the forced energization stopping means. If it is determined, the energization restarting means for releasing the forced energization stop of the actuator and resuming the energization of the actuator, and the energization resuming means for resuming the energization of the actuator, the target And a means for setting the value to a value equal to or higher than the specified pressure.

  When energization to the actuator is forcibly stopped, fuel is not supplied from the fuel pump to the pressure accumulating vessel. Under such circumstances, the fuel pressure in the pressure accumulator vessel may gradually decrease due to a slight fuel leak from the fuel injection valve to the combustion chamber. If the fuel pressure in the pressure accumulating vessel is gradually decreased, the fuel pressure in the pressure accumulating vessel becomes excessively low, and there is a risk that fuel will be bubbled in the pressure accumulating vessel.

  In this regard, in the above-described invention, when it is determined that the actual fuel pressure is equal to or lower than the specified pressure, the forcible stop of the energization to the actuator is released and the energization to the actuator is resumed. At this time, the target value is set to a value equal to or higher than the specified pressure. That is, the fuel pump is driven so that the fuel pressure of the pressure accumulating container is equal to or higher than the specified pressure. Thereby, it can avoid that the fuel pressure of a pressure accumulation container becomes low too much, and can suppress that the bubble formation of a fuel arises in a pressure accumulation container by extension.

In a fourth aspect based on any one of the first to third aspects, the operation means calculates an integral calculation value of a value corresponding to a deviation between the fuel pressure detected by the fuel pressure detection means and the target value. An integral term calculating means for energizing the actuator based on the integral calculation value so as to feedback-control the detected fuel pressure to the target value, and energizing the actuator by the forced energization stopping means. And an integral term increase suppression means for suppressing an increase in the absolute value of the integral calculation value during a period in which is forcibly stopped.

  When energization to the actuator is forcibly stopped and the discharge amount of the fuel pump becomes zero, the fuel pressure in the pressure accumulator gradually decreases due to, for example, a slight fuel leak from the fuel injection valve to the combustion chamber, and is detected by the fuel pressure detection means. Deviation between the fuel pressure (actual fuel pressure) and the target value may occur. In this case, the absolute value of the integral calculation value for feedback control of the actual fuel pressure to the target value may increase. Here, in the situation where the absolute value of the integral calculation value increases, when energization to the actuator is resumed, the discharge amount of the fuel pump increases excessively, so-called overshoot in which the actual fuel pressure greatly exceeds the target value. There is a risk that the controllability of the actual fuel pressure will be excessively reduced, such as occurrence of a so-called undershoot in which the actual fuel pressure is significantly lower than the target value due to occurrence or excessive decrease in the discharge amount of the fuel pump.

  In this regard, in the above invention, the integral term increase suppression means is provided to suppress an increase in the absolute value of the integral calculation value during execution of the fuel cut control. For this reason, the fall of the fuel pressure controllability of a pressure accumulation container in case discharge of a fuel pump is started by the start of electricity supply to an actuator can be controlled suitably.

In a fourth aspect based on the fourth aspect , the integral term calculation means continues to calculate the integral calculation value during execution of the fuel cut control, and the integral term increase suppression means During the execution of the cut control, the fuel pressure detected by the fuel pressure detection means is set to the target value.

  In the above invention, the integral calculation value for feedback control of the actual fuel pressure to the target value is calculated even during execution of the fuel cut control. In the above invention, the actual fuel pressure is set to the target value during execution of the fuel cut control. Thereby, the deviation during the execution of the fuel cut control can be set to an extremely small value (for example, 0), and an increase in the integral calculation value can be suppressed.

In a fourth aspect based on the fourth aspect , the integral term calculation means continues to calculate the integral calculation value during execution of the fuel cut control, and the integral term increase suppression means In the calculation of the integral calculation value when cut control is executed, a value corresponding to the deviation is forcibly made smaller than when the actuator is energized by the operating means.

  In the above invention, the integral calculation value for feedback control of the actual fuel pressure to the target value is calculated even during execution of the fuel cut control. And in the said invention, in calculation of the integral calculation value in case fuel cut control is performed, the value according to the said deviation is forcedly made small in the said aspect. Thereby, increase of the integral calculation value during execution of fuel cut control can be suppressed.

According to a seventh invention, in any one of the first to sixth inventions, the fuel pump is of an engine drive type using the internal combustion engine as a power supply source.

  Engine-driven fuel pumps typically tend to be located near the internal combustion engine. For this reason, the heat generated in the internal combustion engine is easily transmitted to the fuel in the fuel pump, and the fuel is easily bubbled in the fuel pump. For this reason, the said invention has a big merit provided with the forced electricity supply stop means which can suppress the heating of the fuel in a fuel pump.

According to an eighth invention, in any one of the first to seventh inventions, the fuel pump is a high-pressure fuel pump, and the fuel injection system pumps up fuel in the fuel tank and supplies it to the high-pressure fuel pump. A low-pressure fuel pump that discharges and supplies the fuel pumped up by the low-pressure fuel pump to the pressure accumulator, and is sucked and rotated by rotation of a drive shaft of the high-pressure fuel pump. The valve body is provided with a normally open valve body that repeats discharge and communicates and shuts off the fuel suction port and the pump chamber that pressurizes the fuel, and the valve body is closed by energizing the actuator. And the operating means controls the timing of energization of the actuator so as to control the fuel pressure detected by the fuel pressure detecting means to the target value. And adjusting the discharge amount of the high-pressure fuel pump I.

According to a ninth invention, in any one of the first to eighth inventions, the invention further includes setting means for setting the specified temperature higher as the fuel pressure supplied to the fuel pump is higher.

  When the fuel pressure supplied to the fuel pump is increased, the fuel temperature at which the fuel is bubbled tends to increase in the fuel pump. In view of this point, in the above invention, the higher the fuel pressure supplied to the fuel pump, the higher the specified temperature. Therefore, it is possible to accurately grasp the situation in which the fuel in the fuel pump is likely to be bubbled and forcibly stop energization of the actuator.

1 is a system configuration diagram according to a first embodiment. FIG. The flowchart which shows the procedure of the fuel pressure control process concerning the embodiment. The time chart which shows an example of the fuel pressure control process concerning the embodiment. The time chart which shows an example of the fuel pressure control process concerning the embodiment. The flowchart which shows the procedure of the fuel pressure control process concerning 2nd Embodiment. The time chart which shows an example of the fuel pressure control process concerning the embodiment. The time chart which shows an example of the fuel pressure control process concerning the embodiment.

(First embodiment)
Hereinafter, a first embodiment in which a fuel pump control device according to the present invention is applied to an accumulator fuel injection system of a direct injection gasoline engine will be described with reference to the drawings.

  FIG. 1 shows a system configuration according to the present embodiment.

  As shown in the drawing, the fuel in the fuel tank 10 is pumped up by the feed pump 14 through the low pressure passage 12. The feed pump 14 is an electric pump that discharges and supplies the fuel pumped from the fuel tank 10 to the high-pressure fuel pump 16. In the present embodiment, it is assumed that the feed pump 14 can continuously and variably set the discharge pressure (feed pressure) to the high-pressure fuel pump 16 by a regulator (not shown) that the feed pump 14 has.

  The high-pressure fuel pump 16 includes a cylinder 18, a plunger 20 that reciprocates in the cylinder 18, a pump chamber 22 that is defined by the inner peripheral wall surface of the cylinder 18 and the plunger 20, and a suction that sucks fuel supplied from the feed pump 14. A suction valve 26 that communicates or shuts off the port 24 and the pump chamber 22, an actuator that electromagnetically drives the suction valve 26 (electromagnetic solenoid 28), and a pump chamber 22 and a discharge port 30 that discharges fuel are provided. It is a plunger pump configured to include a discharge valve 32.

  Specifically, the high-pressure fuel pump 16 is disposed near the cylinder head of the engine. The intake valve 26 of the high-pressure fuel pump 16 is a normally open type that is opened when the electromagnetic solenoid 28 is not energized, and is closed when the electromagnetic solenoid 28 is energized. It is a disc.

  In the high-pressure fuel pump 16 configured as described above, the plunger 20 is driven by a pump cam 36 connected to the drive shaft 34 of the high-pressure fuel pump 16. Specifically, the drive shaft 34 is mechanically connected to an intake-side or exhaust-side cam shaft 38 disposed near the cylinder head of the engine, and rotates in synchronization with the cam shaft 38. The camshaft 38 is rotated by rotational energy supplied from the engine output shaft (crankshaft 40), and rotates at a predetermined speed ratio (for example, 1/2) with respect to the crankshaft 40. The pump cam 36 has a shape (pump cam profile) in which the distance between the drive shaft 34 and the outer periphery of the cam changes. As a result, the plunger 20 reciprocates in the cylinder 18 in synchronization with the rotation of the drive shaft 34. The period during which the volume in the pump chamber 22 increases due to the lowering of the plunger 20 is the suction stroke of the high-pressure fuel pump 16, and the period during which the volume in the pump chamber 22 decreases as the plunger 20 moves up is the discharge stroke of the high-pressure fuel pump 16. It becomes.

  Specifically, in the suction stroke of the high-pressure fuel pump 16, the fuel from the feed pump 14 is sucked into the pump chamber 22 through the suction port 24 by opening the suction valve 26. Thereafter, when the volume in the pump chamber 22 is reduced by raising the plunger 20, the fuel in the pump chamber 22 is pressurized by closing the intake valve 26 by energizing the electromagnetic solenoid 28. The When the pressure in the pump chamber 22 exceeds the valve opening pressure of the discharge valve 32, the fuel in the pump chamber 22 is discharged from the discharge port 30 through the discharge valve 32. Here, the earlier the valve closing timing of the intake valve 26 in the discharge stroke, the greater the discharge amount of the high-pressure fuel pump 16.

  Incidentally, the high-pressure fuel pump 16 is provided with a fuel temperature sensor 42 for detecting the temperature of fuel sucked into the pump.

  The high-pressure fuel pump 16 is provided with a passage 44 that connects the discharge port 30 and the pump chamber 22 and a relief valve 46. The relief valve 46 is provided on the passage 44. For example, when an abnormality in which energization cannot be stopped despite the command to stop energization of the electromagnetic solenoid 28 occurs, the discharge pressure of the high-pressure fuel pump 16 is excessively increased. It is a member provided for the purpose of preventing it from rising. Specifically, the relief valve 46 is opened when the discharge pressure of the high-pressure fuel pump 16 (the fuel pressure of the discharge port 30 of the high-pressure fuel pump 16) exceeds the valve opening pressure of the relief valve 46, and the pump chamber is opened from the discharge port 30 side. It has a function to return the fuel to the 22 side. The valve opening pressure of the relief valve 46 is set from the viewpoint of avoiding a decrease in reliability of the high-pressure fuel pump 16 and the like.

  The fuel discharged from the high-pressure fuel pump 16 is supplied to the pressure accumulation container (delivery pipe 50) via the high-pressure passage 48. The delivery pipe 50 stores fuel discharged from the high-pressure fuel pump 16 in a high-pressure state, and supplies high-pressure fuel to the fuel injection valve 52 of each cylinder of the engine. The delivery pipe 50 is provided with a fuel pressure sensor 51 that detects the fuel pressure (actual fuel pressure) in the delivery pipe 50.

  The fuel injection valve 52 is arranged such that its injection hole 52 a protrudes into the combustion chamber 54 of the engine, and directly injects and supplies fuel to the combustion chamber 54. Specifically, the fuel injection valve 52 includes a nozzle needle 56 that operates by energization, a body 58, and the like, and the injection hole 52a is formed in the body 58. By energizing the fuel injection valve 52, the nozzle needle 56 is separated from the valve seat formed in the body 58 and opens the injection hole 52a (by opening the fuel injection valve 52), thereby the injection hole 52a. Fuel is injected from. On the other hand, by stopping energization of the fuel injection valve 52, the nozzle needle 56 comes into contact with the valve seat and closes the injection hole 52a (by closing the fuel injection valve 52), thereby injecting fuel from the injection hole 52a. Is stopped.

  An air-fuel mixture of fuel injected from the fuel injection valve 52 and intake air introduced into the combustion chamber 54 via an intake valve (not shown) sparks from the spark plug 60 disposed so as to protrude into the combustion chamber 54. It is ignited by discharge and used for combustion.

  A crank angle sensor 62 that detects the rotation angle of the crankshaft 40 is provided in the vicinity of the crankshaft 40. On the other hand, a cam angle sensor 64 that detects the rotation angle of the cam shaft 38 is provided in the vicinity of the cam shaft 38.

  The electronic control device (ECU 66) is a control device that operates various actuators necessary for various controls of the pressure accumulation type fuel injection system. The ECU 66 includes an air flow meter 68 that detects the amount of intake air supplied to the combustion chamber 54, a water temperature sensor 70 that detects the temperature (cooling water temperature) of cooling water for cooling the engine, the fuel temperature sensor 42, the fuel pressure sensor 51, Detection signals from the crank angle sensor 62 and the cam angle sensor 64 are sequentially input. Based on these input signals, the ECU 66 performs fuel injection control processing by the fuel injection valve 52, energization processing of the feed pump 14, and fuel pressure control processing by the high-pressure fuel pump 16.

  The fuel injection control process calculates the required injection amount of the fuel injection valve 52 based on the engine rotation speed detected by the crank angle sensor 62, the intake air amount (engine load) detected by the air flow meter 68, and the like. The fuel injection valve 52 is energized based on the required injection amount and the actual fuel pressure detected by the fuel pressure sensor 51. Thereby, an amount of fuel corresponding to the required injection amount is injected from the fuel injection valve 52. As the fuel injection control process, a fuel cut control process for stopping fuel injection from the fuel injection valve 52 is also performed.

  The energization process of the feed pump 14 is a process of controlling the feed pressure to the target value. Here, the feed pressure is set higher as the fuel temperature in the high-pressure fuel pump 16 detected by the fuel temperature sensor 42 becomes higher. This is a setting for suppressing the formation of fuel bubbles (vaporization) in the high-pressure fuel pump 16 that is the fuel supply destination of the feed pump 14. In other words, the higher the fuel pressure, the higher the fuel temperature at which the fuel is bubbled. For this reason, the above setting suppresses the bubbling of fuel in the high-pressure fuel pump 16. In the present embodiment, the feed pump 14 is continuously driven even during execution of the fuel cut control. Further, the ECU 66 performs a process of grasping the feed pressure based on a detected value of a fuel pressure sensor (not shown) that the feed pump 14 has.

  The fuel pressure control process is a process of energizing the electromagnetic solenoid 28 to control the actual fuel pressure PF to the target value (target fuel pressure PFREQ).

  This process will be described in detail. First, the target fuel pressure PFREQ in the delivery pipe 50 is calculated based on the engine speed and the intake air amount.

Next, the discharge amount (FB operation amount) of the high-pressure fuel pump 16 required for feedback control of the actual fuel pressure PF to the target fuel pressure PFREQ is calculated. In the present embodiment, the FB manipulated variable is calculated by PI control (proportional integral control) based on the deviation ΔP between the actual fuel pressure PF and the target fuel pressure PFREQ. Specifically, as shown in the following formula (e1), a proportional term that is a value obtained by multiplying the deviation ΔP calculated as a value obtained by subtracting the actual fuel pressure PF from the target fuel pressure PFREQ by a proportional gain Kp, The FB manipulated variable is calculated as an addition value with an integral term that is an integral operation value of the product of the deviation ΔP and the integral gain Ki.
FB manipulated variable = Kp × ΔP + ∫ (Ki × ΔP) dt (e1)
Subsequently, the change amount ΔPFREQ of the target fuel pressure PFREQ is calculated, and the change amount ΔPFREQ of the target fuel pressure is used as the fuel amount in order to calculate the fuel amount required to change the actual fuel pressure PF by the change amount ΔPFREQ of the target fuel pressure. Convert. In this conversion, a value “E / V” obtained by dividing the volume expansion coefficient E of the fuel by the sum V of the volume of the fuel passage between the high-pressure fuel pump 16 and the delivery pipe 50 and the volume of the delivery pipe 50, This is performed by multiplying the change amount ΔPFREQ of the target fuel pressure.

  Then, the discharge amount (FF operation amount) of the high-pressure fuel pump 16 required as the sum of the required injection amount of the fuel injection valve 52 and the converted fuel amount is calculated.

  Then, a final required discharge amount (command discharge amount) for the high-pressure fuel pump 16 is calculated as an addition value of the FB operation amount and the FF operation amount. Based on the output value of the crank angle sensor 62 and the command discharge amount, the energization timing (period from the energization start timing to the energization end timing) to the electromagnetic solenoid 28 is calculated. Then, by outputting an energization signal to the electromagnetic solenoid 28 based on the calculated energization timing, an amount of fuel corresponding to the command discharge amount is discharged from the high pressure fuel pump 16. As a result, the actual fuel pressure PF is controlled to the target fuel pressure PFREQ.

  Next, the forced energization stop process according to the present embodiment will be described.

  This process is a process for stopping energization of the electromagnetic solenoid 28 on condition that the fuel cut control is being executed. This process is a process for suppressing a decrease in fuel pressure controllability in the delivery pipe 50. That is, when the fuel cut control is performed, for example, when the discharge amount of the high-pressure fuel pump 16 decreases or the discharge amount becomes zero, the time that the fuel pumped up by the high-pressure fuel pump 16 stays in the pump becomes long. Thus, the time during which the fuel in the high-pressure fuel pump 16 is heated from the surroundings becomes longer. Here, the fuel in the high-pressure fuel pump 16 includes an electromagnetic solenoid 28 that generates heat when energized, engine oil supplied to a camshaft 38 (pump cam 36) for lubrication, a plunger 20 that generates frictional heat by reciprocation, and a cylinder. 18 etc. are heated as a heat source, and the fuel temperature in this pump rises. The fuel temperature also rises when the fuel itself is compressed in the pump chamber 22.

  When the fuel temperature in the high-pressure fuel pump 16 becomes high due to the heating of the fuel in the high-pressure fuel pump 16, fuel bubbles may be generated in the high-pressure fuel pump 16. Specifically, bubbles can occur in the high-pressure fuel pump 16 on the fuel upstream side of the intake valve 26.

  In particular, in the present embodiment, since the power supply source of the high-pressure fuel pump 16 is an engine, this pump is disposed in the vicinity of the engine head together with the camshaft 38, so that there is a tendency for heat transfer from the engine to be large. For this reason, there is a concern that the degree of heating of the fuel in the high-pressure fuel pump 16 is likely to increase and the occurrence of bubbling becomes significant.

  When the fuel bubbles are generated, the generated bubbles are introduced into the pump chamber 22 and compressed by the plunger 20, and the discharge amount of the high-pressure fuel pump 16 is reduced, and the fuel pressure in the delivery pipe 50 is reduced. There is a risk that the degree of increase in the decrease. In particular, when the pump chamber 22 is filled with bubbles, fuel cannot be discharged from the high-pressure fuel pump 16, and a minute amount of fuel leaks from the delivery pipe 50 side to the pump chamber 22 side via the relief valve 46. Therefore, there is a concern that the fuel pressure in the delivery pipe 50 is reduced to the feed pressure. In these cases, after the fuel cut control is canceled, the actual fuel pressure cannot be quickly increased to the target fuel pressure, and the combustion state may not be improved. In this case, the desired engine output may not be obtained, or the exhaust characteristics may deteriorate.

  For this reason, by performing the forced energization stop processing, heat generation of the electromagnetic solenoid 28 is suppressed, and heating of the fuel in the high-pressure fuel pump 16 is suppressed. Thereby, suppression of generation | occurrence | production of the bubble of the fuel in the high pressure fuel pump 16 is aimed at.

  FIG. 2 shows a procedure of fuel pressure control processing including forced energization stop processing according to the present embodiment. This process is repeatedly executed by the ECU 66 at a predetermined cycle, for example.

  In this series of processing, it is first determined in step S10 whether or not fuel cut control is being executed. In the present embodiment, the calculation of the command discharge amount of the high-pressure fuel pump 16 is continued in preparation for the case where the fuel cut control is canceled during the execution of the fuel cut control.

  When an affirmative determination is made in step S10, the process proceeds to step S12, and the target fuel pressure PFREQ is set to the actual fuel pressure PF. This process is for avoiding a decrease in the fuel pressure controllability in the delivery pipe 50 when the energization to the electromagnetic solenoid 28 is resumed after the energization to the electromagnetic solenoid 28 is stopped by the process of step S20 described later. It is processing of. Hereinafter, this process will be described.

  When energization to the electromagnetic solenoid 28 is stopped and the discharge amount of the high-pressure fuel pump 16 becomes zero, the fuel pressure in the delivery pipe 50 gradually decreases. This is because minute fuel leaks to the combustion chamber 54 via the nozzle needle 56 of the fuel injection valve 52 and the valve seat, or the discharge port 30 of the high-pressure fuel pump 16 via the discharge valve 32 and the relief valve 46. This is because a minute amount of fuel leaks from the side to the pump chamber 22 side. Note that the amount of leakage tends to increase as the fuel pressure in the delivery pipe 50 increases.

  When the fuel pressure in the delivery pipe 50 is gradually decreased, the state where the actual fuel pressure PF is lower than the target fuel pressure PFREQ is continued, and the deviation ΔP may increase. When the situation in which the deviation ΔP is increased continues, the integral term of the FB manipulated variable increases. Here, when energization to the electromagnetic solenoid 28 is resumed under a situation where the integral term increases, the command discharge amount of the high pressure fuel pump 16 becomes excessively large, so that the actual fuel pressure PF greatly exceeds the target fuel pressure PFREQ. There is a possibility that the fuel pressure controllability in the delivery pipe 50 may be lowered, such as occurrence of overshoot. For this reason, by performing the processing of this step, the deviation ΔP is set to an extremely small value (0), and an increase in the integral term is suppressed, and a decrease in the fuel pressure controllability is suppressed.

  When the amount of leakage from the delivery pipe 50 is small, the fuel pressure in the delivery pipe 50 may gradually increase for a while due to the stop of energization of the electromagnetic solenoid 28 during fuel cut control. This is because the fuel is heated by the retention of the fuel in the delivery pipe 50. Here, if the state where the actual fuel pressure PF is higher than the target fuel pressure PFREQ is continued due to the gradual increase of the fuel pressure in the delivery pipe 50, the deviation ΔP becomes smaller than 0 and the integral term becomes smaller than 0. Sometimes. In this case, when energization to the electromagnetic solenoid 28 is resumed, a so-called undershoot occurs in which the actual fuel pressure PF is significantly lower than the target fuel pressure PFREQ due to the command discharge amount of the high-pressure fuel pump 16 being excessively reduced. There is also a fear.

  In the subsequent step S14, the specified temperature T1 is variably set based on the feed pressure PL. Here, the specified temperature T1 is set higher as the feed pressure PL is higher. As described above, this setting is based on the fact that the higher the fuel pressure, the higher the temperature at which fuel aeration occurs. The specified temperature T1 may be set using, for example, a map or a mathematical formula associated with the feed pressure PL.

  In the subsequent step S16, it is determined whether or not the fuel temperature Te in the high-pressure fuel pump 16 is equal to or higher than a specified temperature T1. This process is a process for determining whether or not there is a high probability that fuel will be bubbled in the high-pressure fuel pump 16.

  If an affirmative determination is made in step S16, the process proceeds to step S18 to determine whether the actual fuel pressure PF is higher than the specified pressure Pα. Here, the specified pressure Pα is set to a pressure that is higher than, for example, the feed pressure PL and slightly higher than a pressure that is assumed to cause fuel to be bubbled in the delivery pipe 50. This process is for determining whether or not the fuel pipe is likely to be bubbled in the delivery pipe 50. The specified pressure Pα may be set higher as the fuel temperature in the delivery pipe 50 is higher, for example.

  When it is determined in step S18 that the actual fuel pressure PF is higher than the specified pressure Pα, the process proceeds to step S20, and a forced energization stop process for forcibly stopping energization of the electromagnetic solenoid 28 is performed.

  On the other hand, if a negative determination is made in step S18, the process proceeds to step S22, and the target fuel pressure PFREQ is set to the specified pressure Pα. In step S24, the forced stop of energization of the electromagnetic solenoid 28 is released, and the energization of the electromagnetic solenoid 28 is resumed. In these processes, the fuel pressure in the delivery pipe 50 is maintained at the specified pressure Pα by starting the fuel discharge from the high-pressure fuel pump 16, thereby suppressing the generation of fuel bubbles in the delivery pipe 50. It is.

  When the processes of steps S20 and S24 are completed, or when a negative determination is made in steps S10 and S16, the process proceeds to step S26, where the command discharge amount of the high-pressure fuel pump 16 is added as an addition value of the FF operation amount and the FB operation amount. Is calculated. Here, in the case of going through the processing of step S12 or step S22, the deviation ΔP each time becomes a very small value (0), so that an increase in the integral term is suppressed.

  Incidentally, when it is determined that the fuel cut control has been canceled, the target fuel pressure PFREQ is set based on the engine speed, the intake air amount, and the like.

  In addition, when the process of step S26 is completed, this series of processes is once complete | finished.

  3 and 4 show an example of the fuel pressure control process according to the present embodiment.

  First, FIG. 3 shows an example in which the fuel temperature Te in the high-pressure fuel pump 16 becomes equal to or higher than the specified temperature T1 before the fuel cut control is executed. Specifically, FIG. 3A shows the transition of whether or not the fuel cut control is executed, FIG. 3B shows the transition of the driving state of the high-pressure fuel pump 16, and FIG. 3C shows the high-pressure fuel. A transition of the fuel temperature Te in the pump 16 is shown, and FIG. 3D shows a transition of the actual fuel pressure PF and the target fuel pressure PFREQ. In the illustrated example, the fuel cut control is executed in a situation in which the vehicle travels on a downhill from time t2 after the engine is operated at a high load so that the vehicle travels uphill until time t2. Show.

  As shown in the figure, it is determined that the fuel temperature Te in the high-pressure fuel pump 16 becomes equal to or higher than the specified temperature T1 at time t1. Then, at time t2, it is determined that the fuel cut control has been started under the condition that the actual fuel pressure PF is determined to exceed the specified pressure Pα. Thereby, the energization to the electromagnetic solenoid 28 is stopped by the forced energization stop process, the discharge amount of the high-pressure fuel pump 16 becomes 0, and the target fuel pressure PFREQ is set to the actual fuel pressure PF.

  It should be noted that immediately after time t2, the actual fuel pressure PF once rises, then rises and then falls again. Although the discharge amount of the high-pressure fuel pump 16 becomes zero and the actual fuel pressure PF once falls, This is because the fuel pressure in the delivery pipe 50 increases due to the heating of the fuel in the delivery pipe 50, and the fuel pressure decreases due to minute fuel leaks from the gap between the nozzle needle 56 and the valve seat of the fuel injection valve 52.

  After that, until the time t3, the target fuel pressure PFREQ is set to the actual fuel pressure PF in a situation where the actual fuel pressure PF gradually decreases, so the deviation ΔP becomes a very small value (0), and the integral term of the FB manipulated variable An increase can be avoided.

  At time t3 when it is determined that the actual fuel pressure PF is equal to or lower than the specified pressure Pα, the target fuel pressure PFREQ is set to the specified pressure Pα, and energization of the electromagnetic solenoid 28 is resumed.

  Next, FIG. 4 shows an example of the fuel pressure control process when the fuel temperature Te in the high-pressure fuel pump 16 becomes equal to or higher than the specified temperature T1 after the start of the fuel cut control. Specifically, FIGS. 4A to 4D correspond to FIGS. 3A to 3D described above.

  As shown in the drawing, the target fuel pressure PFREQ is set to the actual fuel pressure PF by starting the fuel cut control at time t1. Then, at time t2, when it is determined that the fuel temperature Te in the high-pressure fuel pump 16 is equal to or higher than the specified temperature T1, the energization of the electromagnetic solenoid 28 is forcibly stopped by the forced energization stop process.

  Thereafter, at time t3 when the actual fuel pressure PF gradually decreases and the actual fuel pressure PF is determined to be equal to or lower than the specified pressure Pα, the target fuel pressure PFREQ is set to the specified pressure Pα, and energization of the electromagnetic solenoid 28 is resumed.

  As described above, in this embodiment, when it is determined that the fuel cut control is being executed, for example, the forced energization stop process for forcibly stopping the energization of the electromagnetic solenoid 28 is performed, so that the internal pressure of the high-pressure fuel pump 16 is increased. The rise in the fuel temperature Te can be suppressed, and the generation of fuel bubbles in the high-pressure fuel pump 16 can be suppressed.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) Forced energization stop processing for forcibly stopping energization of the electromagnetic solenoid 28 when it is determined that the fuel cut control is being executed and the fuel temperature Te in the high-pressure fuel pump 16 is equal to or higher than the specified temperature T1. Went. For this reason, it is possible to suppress the fuel in the high pressure fuel pump 16 from being heated by the heat generated by the high pressure fuel pump 16 itself including the heat generated by the electromagnetic solenoid 28. Thereby, generation | occurrence | production of the bubbling of a fuel can be suppressed and by extension, the fall of the fuel pressure controllability of the delivery pipe 50 can be suppressed suitably.

  Furthermore, the specified temperature T1 was set higher as the feed pressure PL was higher. As a result, it is possible to accurately grasp whether or not there is a high probability that fuel will be bubbled in the high-pressure fuel pump 16 and stop energization of the electromagnetic solenoid 28.

  (2) The target fuel pressure PFREQ is set to the actual fuel pressure PF during the period when the fuel cut control is executed. Thereby, when the energization to the electromagnetic solenoid 28 is resumed, it is possible to suitably suppress a decrease in the fuel pressure controllability of the delivery pipe 50 due to an increase in the integral term.

  (3) When it is determined that the forced energization to the electromagnetic solenoid 28 is stopped by the forced energization stop process, if it is determined that the actual fuel pressure PF is equal to or lower than the specified pressure Pα, the target fuel pressure PFREQ is set to the specified pressure. Set to Pα. Moreover, the forced stop of energization was canceled and the energization of the electromagnetic solenoid 28 was resumed. Thereby, generation | occurrence | production of the bubbling of the fuel in the delivery pipe 50 can be suppressed.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, in the situation where it is determined that the fuel cut control is being executed, instead of setting the target fuel pressure PFREQ to the actual fuel pressure PF, the integral gain Ki is set to be extremely different in the calculation of the integral term of the FB manipulated variable. By setting a small value, an increase in the integral term is suppressed.

  FIG. 5 shows the procedure of the fuel pressure control process including the forced energization stop process according to the present embodiment. This process is repeatedly executed by the ECU 66 at a predetermined cycle, for example. In FIG. 5, the same steps as those shown in FIG. 2 are given the same step numbers for the sake of convenience.

  In this series of processes, if an affirmative determination is made in step S10, the integral gain Ki is set to a very small value in step S28. Specifically, the integral gain Ki is set to a fixed value (for example, 0.00001) smaller than a value (for example, 1) when the electromagnetic solenoid 28 is energized (during engine operation before fuel cut control), for example. This process is similar to the process of step S12 of the first embodiment, and when the energization to the electromagnetic solenoid 28 is resumed after the energization to the electromagnetic solenoid 28 is forcibly stopped, the integral term This is a process for avoiding a decrease in fuel pressure controllability in the delivery pipe 50 due to the increase.

  If the determination in step S16 is affirmative after step S14, and the determination in step S18 is negative, the process proceeds to step S30. In step S30, the setting of the process in step S28 is canceled, and the process returns to the calculation of the integral term using the integral gain Ki at the normal time (before the fuel cut control). In this step, the target fuel pressure PFREQ is set to the specified pressure Pα as in the process of step S22 of FIG. Thereafter, the process proceeds to step S24.

  In addition, when the process of step S26 is completed, this series of processes is once complete | finished.

  6 and 7 show an example of the fuel pressure control process according to the present embodiment.

  First, FIG. 6 shows an example in which the fuel temperature Te in the high-pressure fuel pump 16 becomes equal to or higher than the specified temperature T1 before the fuel cut control is executed. Specifically, FIG. 6C shows the transition of the integral gain Ki, and FIGS. 6A, 6B, 6D, and 6E are shown in FIG. Corresponds to FIG. In the figure, the running state of the vehicle is the same as in FIG.

  As shown in the figure, it is determined that the fuel temperature Te in the high-pressure fuel pump 16 becomes equal to or higher than the specified temperature T1 at time t1. Then, at time t2, it is determined that the fuel cut control has been started under the condition that the actual fuel pressure PF is determined to exceed the specified pressure Pα. Thereby, the forced energization stop process is started, and the integral gain Ki is set to a very small fixed value.

  Thereafter, until the time t3, the integral gain Ki is set to a very small fixed value in a situation where the actual fuel pressure PF gradually decreases, so that an increase in the integral term can be suppressed.

  Then, at time t3 when it is determined that the actual fuel pressure PF is equal to or lower than the specified pressure Pα, the target fuel pressure PFREQ is set to the specified pressure Pα, and the process returns to the calculation of the integral term using the normal integral gain Ki. Then, energization to the electromagnetic solenoid 28 is resumed.

  Next, FIG. 7 shows an example of the fuel pressure control process when the fuel temperature Te in the high-pressure fuel pump 16 becomes equal to or higher than the specified temperature T1 after the start of the fuel cut control. Specifically, FIGS. 7A to 7E correspond to FIGS. 6A to 6E.

  As shown in the figure, when the fuel cut control is started at time t1, the integral gain Ki is set to a very small fixed value. Then, at time t2, when it is determined that the fuel temperature Te in the high-pressure fuel pump 16 is equal to or higher than the specified temperature T1, the energization of the electromagnetic solenoid 28 is forcibly stopped by the forced energization stop process.

  Thereafter, the target fuel pressure PFREQ is set to the specified pressure Pα at the time t3 when the actual fuel pressure PF is gradually decreased and the actual fuel pressure PF is determined to be equal to or lower than the specified pressure Pα, and the integral term using the normal integral gain Ki is used. Returning to the calculation, the energization of the electromagnetic solenoid 28 is resumed.

  As described above, in the present embodiment, by setting the integral gain Ki to a very small fixed value in the calculation of the integral term, it is possible to suppress the decrease in the fuel pressure controllability of the delivery pipe 50 due to the increase in the integral term. it can.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  The method for suppressing the increase of the integral calculation value during execution of the fuel cut control is not limited to those exemplified in the above embodiments. For example, a method of stopping feedback control (stopping calculation of the FB operation amount) during execution of fuel cut control may be employed.

  The feed pump 14 is not limited to those exemplified in the above embodiments. For example, the feed pressure PL may be variably set stepwise (for example, N steps: N is an integer of 2 or more). In addition, the feed pump 14 is not limited to one in which the feed pressure PL can be variably set, and the feed pressure PL may be a fixed value.

  In each of the above embodiments, the fuel temperature Te in the high-pressure fuel pump 16 is directly detected, but the present invention is not limited to this. For example, the fuel temperature Te in the high-pressure fuel pump 16 may be estimated based on the detection value of the water temperature sensor 70, the temperature of the engine oil, the temperature of the engine room, and the like. This is based on the fact that the fuel temperature Te in the high-pressure fuel pump 16 tends to increase as the coolant temperature, engine oil temperature, and engine room temperature increase. Further, instead of the fuel temperature Te in the high-pressure fuel pump 16, for example, the processing in step S <b> 16 of FIG. 2 is performed using a parameter value (for example, cooling water temperature or engine oil temperature) correlated with this temperature. You may go.

  The method for setting the target fuel pressure PFREQ in the case where the energization to the electromagnetic solenoid 28 is resumed is not limited to those exemplified in the above embodiments. For example, the target fuel pressure PFREQ may be set to a value higher than the specified pressure Pα. However, if the target fuel pressure PFREQ is suddenly increased at the timing of resuming energization of the electromagnetic solenoid 28, there is a concern that the fuel pressure controllability of the delivery pipe 50 may be reduced due to an increase in the integral term. For this reason, for example, a control logic for gradually increasing the target fuel pressure PFREQ toward a value higher than the specified pressure Pα from the timing of resuming energization of the electromagnetic solenoid 28 may be employed.

  In the first embodiment, when it is determined that the fuel cut control is being executed, the target fuel pressure PFREQ is set to the actual fuel pressure PF, but the present invention is not limited to this. For example, when it is determined that the energization to the electromagnetic solenoid 28 is stopped by the forced energization stop process, the target fuel pressure PFREQ may be set to the actual fuel pressure PF. Even in this case, an increase in the integral term can be suppressed.

  The method for calculating the FB operation amount is not limited to the one exemplified in the first embodiment. For example, the FB manipulated variable may be calculated by PID control (proportional integral derivative control) based on the deviation ΔP.

  The actuator is not limited to the one that generates heat when energized, and may be an actuator that generates a small amount of heat when energized or does not generate heat when energized. Even in this case, the forced energization stop process is effective. That is, for example, in order to maintain the actual fuel pressure at a predetermined pressure in preparation for when the fuel cut control is canceled, a control logic that drives the high-pressure fuel pump 16 even when the fuel cut control is being executed may be employed. is there. This control is for compensating for an actual fuel pressure that is reduced by a minute fuel leak or the like from the delivery pipe 50 side to the pump chamber 22 side via the relief valve 46.

  Here, when the above control is adopted, the discharge amount of the high-pressure fuel pump 16 during execution of the fuel cut control is compared with the discharge amount of the high-pressure fuel pump 16 by the fuel pressure control process before the fuel cut control (normal time). Since there is a tendency to decrease, the fuel temperature in the pump rises and there is a possibility that bubble formation will occur. For this reason, under the situation where the fuel temperature in the fuel pump becomes equal to or higher than the specified temperature and the fuel cut control is executed, the fuel accompanying the compression of the fuel in the high-pressure fuel pump 16 is stopped by forcibly stopping energization of the actuator. By suppressing the rise in temperature, it can be expected to suppress the generation of fuel bubbles.

  The fuel injection system for the internal combustion engine is not limited to a system including a spark ignition internal combustion engine such as a direct injection gasoline engine. For example, a system (common rail fuel injection system) including a compression ignition type internal combustion engine such as a diesel engine may be used. Even in this case, in order to adjust the discharge amount of a fuel pump (for example, a plunger type high-pressure fuel pump) that discharges and supplies fuel to the common rail, the actuator and the like generate heat by energizing the actuator of the fuel pump. If the fuel in the fuel pump is heated by this and there is a risk that the fuel will be bubbled, the application of the present invention is effective.

  The high-pressure fuel pump is not limited to an engine-driven type, and may be an electric type (electric pump), for example.

  The fuel injection system to which the present invention is applied is not limited to those exemplified in the above embodiments. For example, it is good also as a structure further equipped with the return path which connects the delivery pipe 50 and the fuel tank 10, and the valve body which is provided on a return path and opens when the fuel pressure of the delivery pipe 50 becomes more than predetermined. In this case, a slight fuel leak from the valve body may be included in the factor that the fuel pressure of the delivery pipe 50 gradually decreases due to the stop of energization of the electromagnetic solenoid 28. In addition, the said valve body is a member for avoiding that the fuel pressure of the delivery pipe 50 rises too much and the reliability of the delivery pipe 50 grade | etc., Falls.

  DESCRIPTION OF SYMBOLS 10 ... Fuel tank, 14 ... Feed pump, 16 ... High pressure fuel pump, 28 ... Electromagnetic solenoid, 50 ... Delivery pipe, 51 ... Fuel pressure sensor, 52 ... Fuel injection valve, 66 ... ECU (one embodiment of control apparatus of fuel pump) ).

Claims (9)

A pressure accumulating container capable of accumulating fuel in a high pressure state, a fuel injection valve for directly injecting fuel supplied from the pressure accumulating container to a combustion chamber of an internal combustion engine, and a fuel for discharging fuel from a fuel tank to the pressure accumulating container Applied to a fuel injection system of an internal combustion engine comprising a pump and a fuel pressure detecting means for detecting a fuel pressure of the pressure accumulating vessel,
The fuel pump includes an electronically controlled actuator, and discharges and supplies fuel to the pressure accumulating container on condition that the actuator is energized,
Operating means for energizing the actuator to control the fuel pressure detected by the fuel pressure detecting means to the target value;
The fuel temperature in the fuel pump is equal to or higher than a specified temperature for determining whether or not there is a high probability that fuel will be bubbled in the fuel pump, and fuel injection from the fuel injection valve A fuel pump control device comprising: a forced energization stopping means for forcibly stopping energization of the actuator on condition that fuel cut control for stopping the operation is being executed. The operation means includes an integral term calculation means for calculating an integral calculation value of a value corresponding to a deviation between the fuel pressure detected by the fuel pressure detection means and the target value, and feeds back the detected fuel pressure to the target value. In order to control, the actuator is energized based on the integral calculation value,
The integral term calculation means continues calculation of the integral calculation value during execution of the fuel cut control.
During the execution of the fuel cut control, by setting the fuel pressure detected by the fuel pressure detecting means to the target value, the integration is performed in a period in which the energization to the actuator is forcibly stopped by the forced energization stopping means. 2. The fuel pump control device according to claim 1, further comprising integral term increase suppression means for suppressing an increase in the absolute value of the calculated value. The operation means includes an integral term calculation means for calculating an integral calculation value of a value corresponding to a deviation between the fuel pressure detected by the fuel pressure detection means and the target value, and feeds back the detected fuel pressure to the target value. In order to control, the actuator is energized based on the integral calculation value,
The integral term calculation means continues calculation of the integral calculation value during execution of the fuel cut control.
In the calculation of the integral calculation value when the fuel cut control is executed, the forcing is performed by forcibly reducing a value corresponding to the deviation each time than when the actuator is energized by the operation means. 2. The fuel pump according to claim 1, further comprising an integral term increase suppression unit that suppresses an increase in the absolute value of the integral calculation value during a period in which the energization to the actuator is forcibly stopped by the energization stop unit. Control device. A pressure accumulating container capable of accumulating fuel in a high pressure state, a fuel injection valve for directly injecting fuel supplied from the pressure accumulating container to a combustion chamber of an internal combustion engine, and a fuel for discharging fuel from a fuel tank to the pressure accumulating container Applied to a fuel injection system of an internal combustion engine comprising a pump and a fuel pressure detecting means for detecting a fuel pressure of the pressure accumulating vessel,
The fuel pump includes an electronically controlled actuator, and discharges and supplies fuel to the pressure accumulating container on condition that the actuator is energized,
Operating means for energizing the actuator to control the fuel pressure detected by the fuel pressure detecting means to the target value;
Based on the fact that the fuel temperature in the fuel pump is equal to or higher than a specified temperature and fuel cut control for stopping the fuel injection from the fuel injection valve is being executed, energization to the actuator is forcibly stopped. A forced energization stop means,
The operation means includes an integral term calculation means for calculating an integral calculation value of a value corresponding to a deviation between the fuel pressure detected by the fuel pressure detection means and the target value, and feeds back the detected fuel pressure to the target value. In order to control, the actuator is energized based on the integral calculation value,
The integral term calculation means continues calculation of the integral calculation value during execution of the fuel cut control.
During the execution of the fuel cut control, by setting the fuel pressure detected by the fuel pressure detecting means to the target value, the integration is performed in a period in which the energization to the actuator is forcibly stopped by the forced energization stopping means. A fuel pump control device comprising integral term increase suppression means for suppressing an increase in absolute value of a calculated value. The forced energization stopping means, any fuel temperature in the fuel pump based on the less than the prescribed temperature, according to claim 1-4, characterized in that does not perform stopping of the forced energization of the actuator or control device for a fuel pump according to item 1. In a situation where energization to the actuator is forcibly stopped by the forced energization stop means, if it is determined that the fuel pressure detected by the fuel pressure detection means is below a specified pressure, the energization to the actuator is forced Energization restarting means for releasing the stop and resuming energization of the actuator;
Upon resuming the power supply to said actuator by said current supply resuming means, wherein the target value in any one of claims 1-5, characterized by further comprising a means for setting a value above the specified pressure Fuel pump control device.   The fuel pump control device according to any one of claims 1 to 6, wherein the fuel pump is of an engine drive type using the internal combustion engine as a power supply source. The fuel pump is a high-pressure fuel pump,
The fuel injection system further includes a low-pressure fuel pump that pumps up fuel from the fuel tank and supplies the fuel to the high-pressure fuel pump.
The high-pressure fuel pump discharges and supplies the fuel pumped up by the low-pressure fuel pump to the pressure accumulating vessel, and repeats suction and discharge by rotation of the drive shaft of the high-pressure fuel pump, and also a fuel suction port And a normally open valve body that communicates and shuts off the fuel and a pump chamber that pressurizes the fuel,
The valve body is closed by energizing the actuator,
The operation means adjusts the discharge amount of the high-pressure fuel pump by operating the energization timing to the actuator so as to control the fuel pressure detected by the fuel pressure detection means to the target value. The control apparatus of the fuel pump of any one of -7.   The fuel pump control device according to any one of claims 1 to 8, further comprising setting means for setting the specified temperature higher as the fuel pressure supplied to the fuel pump is higher.

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