JP2012162995A - Fuel supply system of internal combustion engine - Google Patents

Abstract

The present invention relates to a fuel supply system for an internal combustion engine including a low pressure fuel pump capable of changing the number of operating impellers and a high pressure fuel pump for boosting fuel discharged from the low pressure fuel pump. Too much provision of technology that can contribute to reducing the power consumption of fuel pumps.
The present invention relates to a first impeller that rotates in conjunction with a rotating shaft of an electric motor, a second impeller that can rotate relative to the rotating shaft of the electric motor, and a rotating shaft between the rotating shaft and the second impeller of the electric motor. By using a low-pressure fuel pump provided with the arranged centrifugal clutch, an increase in power consumption accompanying a change in the number of operating impellers is suppressed.
[Selection] Figure 2

Description

  The present invention relates to a fuel supply system for an internal combustion engine including a low-pressure fuel pump (feed pump) and a high-pressure fuel pump (supply pump).

  In recent years, an electric fuel pump (for example, a turbine-type fuel pump) is used as a low-pressure fuel pump, and a mechanical fuel pump (for example, a plunger-type fuel pump) driven by the power of an internal combustion engine is used as a high-pressure fuel pump. 2. Description of the Related Art A fuel supply system for an internal combustion engine used as the above is known.

  As an electric fuel pump, there is known a fuel pump capable of switching between coupling and non-coupling of two impellers using electric power. As a method of using such a fuel pump, when the engine load is low, only one impeller is moved by disengaging the two impellers, and when the engine load is high, the two impellers are combined. There has also been proposed a method of moving two impellers in a state (see, for example, Patent Document 1).

Japanese Utility Model Publication No. 63-57392 Japanese Patent Laid-Open No. 09-151823 Japanese Patent Laying-Open No. 2005-076568 JP 2004-360909 A JP 05-509141 A

  By the way, in a fuel supply system for an internal combustion engine equipped with a low-pressure fuel pump and a high-pressure fuel pump, the power consumption of the low-pressure fuel pump is reduced as much as possible by reducing the discharge pressure of the low-pressure fuel pump within a range where no vapor is generated. It is hoped to reduce it.

  However, when the above-described conventional fuel pump is used as the low-pressure fuel pump, power is consumed to switch between coupling and non-coupling of the two impellers, so that an effect of reducing the power consumption of the low-pressure fuel pump is obtained. It can be difficult.

  The present invention has been made in view of the above-described circumstances, and an object thereof is a low-pressure fuel pump capable of changing the number of operation of the impeller, and a high-pressure fuel for boosting the fuel discharged from the low-pressure fuel pump. In a fuel supply system for an internal combustion engine equipped with a pump, the present invention provides a technique that can contribute to reducing power consumption of a low-pressure fuel pump.

  In order to solve the above-described problems, the present invention is configured to mechanically change the number of operating impellers of a low-pressure fuel pump in an internal combustion engine fuel supply system including a low-pressure fuel pump and a high-pressure fuel pump.

Specifically, the present invention relates to a fuel supply system for an internal combustion engine comprising a low-pressure fuel pump and a high-pressure fuel pump for boosting the fuel discharged from the low-pressure fuel pump.
The low-pressure fuel pump includes a first impeller that rotates in conjunction with a rotating shaft of the electric motor, a second impeller that is arranged coaxially with the rotating shaft of the electric motor and is rotatable relative to the rotating shaft, and a rotating shaft of the electric motor A centrifugal clutch that is interposed between the second impellers and that engages the rotary shaft and the second impeller using a centrifugal force generated by an increase in the rotational speed of the rotary shaft.

  According to this configuration, when the rotating shaft of the electric motor is rotating at a low speed, the centrifugal clutch is disengaged. That is, the rotational force of the rotating shaft of the electric motor is not transmitted to the second impeller. As a result, when the rotating shaft of the electric motor is rotating at a low speed, the electric motor rotates only the first impeller.

  Further, when the rotational speed of the rotating shaft of the electric motor becomes high, the centrifugal clutch is engaged. That is, the rotational force of the rotating shaft of the electric motor is transmitted to the second impeller. As a result, when the rotating shaft of the electric motor is rotating at a high speed, the electric motor rotationally drives both the first impeller and the second impeller.

  According to the low-pressure fuel pump of the present invention, the number of operating impellers can be changed without using electric power. As a result, it is possible to suppress an increase in power consumption accompanying a change in the number of operating impellers.

  The second impeller may be configured such that the flow rate that can be discharged per unit time is larger than that of the first impeller. In other words, the first impeller may be configured such that the flow rate that can be discharged per unit time is smaller than that of the second impeller. According to such a configuration, the pump efficiency when only the first impeller operates can be increased, and the discharge pressure and flow rate when the first impeller and the second impeller operate can be increased.

  A fuel supply system for an internal combustion engine according to the present invention includes a detection unit that detects a change amount of current consumption of an electric motor, and an engagement state and a disengagement state of a centrifugal clutch when the change amount detected by the detection unit exceeds a threshold value. And a determination unit that determines that the state has been switched.

  When the centrifugal clutch shifts from the non-engaged state to the engaged state, the load on the motor increases due to an increase in the number of operating impellers. As a result, the current consumption of the electric motor increases at a time. On the other hand, when the centrifugal clutch shifts from the engaged state to the non-engaged state, the load on the electric motor decreases due to the decrease in the number of operating impellers. As a result, the current consumption of the electric motor is reduced at a time. Therefore, when the amount of change detected by the detection unit exceeds a predetermined threshold, it can be determined that the engaged state and the disengaged state of the centrifugal clutch are switched.

  Here, when the centrifugal clutch is shifted from the non-engaged state to the engaged state, the rotational speed of the rotating shaft is increased by increasing the voltage applied to the low-pressure fuel pump. At this time, the current consumption of the low-pressure fuel pump increases linearly with an increase in applied voltage if the number of operating impellers is constant, but shows a larger change (increase) than the applied voltage when the number of operating impellers increases. . On the other hand, when shifting the centrifugal clutch from the engaged state to the non-engaged state, the rotational speed of the rotating shaft is decreased by decreasing the voltage applied to the low-pressure fuel pump. At this time, the current consumption of the low-pressure fuel pump decreases linearly with respect to the decrease in applied voltage if the number of operating impellers is constant, but shows a change (decrease) greater than the applied voltage when the number of operating impellers decreases. .

Therefore, when the amount of change in current consumption per unit time becomes larger than the amount of change in applied voltage per unit time, the number of operating impellers changes (the engagement state and the non-engagement state of the centrifugal clutch are switched). May be determined. That is, the change amount of the applied voltage per unit time may be determined as the threshold value.

  When switching between the engaged state and the disengaged state of the centrifugal clutch is determined by the above-described method, the number of operating impellers can be accurately changed. For example, in the fuel supply system for an internal combustion engine according to the present invention, when the centrifugal clutch is shifted from the non-engaged state to the engaged state, first, the applied voltage of the electric motor is made higher than the target value, and then the determination unit is configured to You may make it further provide the control part which reduces the applied voltage of an electric motor to a target value, when switching is determined. According to such a configuration, it becomes possible to quickly and accurately switch the engagement state and the disengagement state of the centrifugal clutch (change of the number of operating impellers). When the centrifugal clutch is shifted from the engaged state to the non-engaged state, the control unit first lowers the applied voltage of the motor below the target value, and then the motor is switched when the determination unit determines that the centrifugal clutch is switched. The applied voltage may be increased to the target value.

  According to the present invention, in a fuel supply system for an internal combustion engine comprising a low-pressure fuel pump capable of changing the number of operating impellers and a high-pressure fuel pump for boosting fuel discharged from the low-pressure fuel pump, the low-pressure fuel This can contribute to reduction of power consumption of the pump.

It is a figure which shows schematic structure of the fuel supply system of an internal combustion engine. It is a figure which shows the structure of a low pressure fuel pump typically. It is a figure which shows the structure of a centrifugal clutch typically. It is a figure which shows the engagement state of a centrifugal clutch. It is a figure which shows the change of the consumption current of a motor when the applied voltage of a motor is increased when a centrifugal clutch is in a non-engagement state. It is a figure which shows the change of the consumption current of a motor when the applied voltage of a motor is reduced when a centrifugal clutch is in an engagement state. It is a figure which shows the example of control of the voltage applied to a motor when switching a centrifugal clutch from a non-engagement state to an engagement state. It is a figure which shows the example of control of the voltage applied to a motor, when switching a centrifugal clutch from an engagement state to a non-engagement state.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of a fuel supply system for an internal combustion engine. The fuel supply system shown in FIG. 1 includes a low-pressure fuel pump 1 and a high-pressure fuel pump 2.

  The low-pressure fuel pump 1 is a pump for pumping up fuel stored in the fuel tank 3 and is a turbine pump (Wesco pump) driven by electric power. The fuel discharged from the low pressure fuel pump 1 is guided to the suction port of the high pressure fuel pump 2 by the low pressure fuel passage 4.

The high-pressure fuel pump 2 is a pump for boosting the fuel discharged from the low-pressure fuel pump 1, and is a reciprocating pump (plunger pump) driven by the power of the internal combustion engine (for example, the rotational force of the camshaft). ). A suction valve 2 a for switching between conduction and blockage of the suction port is provided at the suction port of the high-pressure fuel pump 2. The suction valve 2a is an electromagnetically driven valve mechanism, and changes the discharge amount of the high-pressure fuel pump 2 by changing the opening / closing timing with respect to the position of the plunger. The base end of the high-pressure fuel passage 5 is connected to the discharge port of the high-pressure fuel pump 2. The end of the high pressure fuel passage 5 is connected to a delivery pipe 6.

  A plurality of (four in the example shown in FIG. 1) fuel injection valves 7 are connected to the delivery pipe 6, and high-pressure fuel pumped from the high-pressure fuel pump 2 to the delivery pipe 6 is supplied to each fuel injection valve 7. It is to be distributed. The fuel injection valve 7 is a valve mechanism that injects fuel directly into the cylinder of the internal combustion engine.

  In addition to the in-cylinder fuel injection valve such as the fuel injection valve 7 described above, a port injection fuel injection valve for injecting fuel into the intake passage (intake port) is attached to the internal combustion engine. If so, the low pressure fuel passage 4 may be branched from the middle to supply the low pressure fuel to the port injection delivery pipe.

  Returning to FIG. 1, the base end of the branch passage 8 is connected to the low-pressure fuel passage 4. The end of the branch passage 8 is connected to the fuel tank 3. A pressure regulator 9 is provided in the middle of the branch passage 8. The pressure regulator 9 opens when the pressure (fuel pressure) in the low-pressure fuel passage 4 exceeds a predetermined value, so that excess fuel in the low-pressure fuel passage 4 passes to the fuel tank 3 via the branch passage 8. Configured to return.

  A check valve 10 and a pulsation damper 11 are arranged in the middle of the high-pressure fuel passage 5 described above. The check valve 10 is a one-way valve that allows a flow from the discharge port of the high-pressure fuel pump 2 to the delivery pipe 6 and restricts a flow from the delivery pipe 6 to the discharge port of the high-pressure fuel pump 2. The pulsation damper 11 attenuates fuel pulsation caused by the operation (suction operation and discharge operation) of the high-pressure fuel pump 2.

  Connected to the delivery pipe 6 is a return passage 12 for returning surplus fuel in the delivery pipe 6 to the fuel tank 3. In the middle of the return passage 12, a relief valve 13 that switches between return and passage of the return passage 12 is disposed. The relief valve 13 is an electric or electromagnetically driven valve mechanism, and is opened when the fuel pressure in the delivery pipe 6 exceeds a target value.

  In the middle of the return passage 12, the end of the communication passage 14 is connected. A base end of the communication path 14 is connected to the high-pressure fuel pump 2. The communication passage 14 is a passage for guiding excess fuel discharged from the high-pressure fuel pump 2 to the return passage 12.

  Here, the fuel supply system in the present embodiment includes an ECU 15 for electrically controlling the above-described devices. The ECU 15 is an electronic control unit that includes a CPU, ROM, RAM, backup RAM, and the like. The ECU 15 is electrically connected to various sensors such as a fuel pressure sensor 16, an intake air temperature sensor 17, an accelerator position sensor 18, a crank position sensor 19, a fuel temperature sensor 20, and a feed pressure sensor 21.

  The fuel pressure sensor 16 is a sensor that outputs an electrical signal correlated with the fuel pressure in the delivery pipe 6 (discharge pressure of the high-pressure fuel pump). The intake air temperature sensor 17 outputs an electrical signal correlated with the temperature of air taken into the internal combustion engine. The accelerator position sensor 18 outputs an electrical signal correlated with the operation amount (accelerator opening) of the accelerator pedal. The crank position sensor 19 is a sensor that outputs an electrical signal correlated with the rotational position of the output shaft (crankshaft) of the internal combustion engine. The fuel temperature sensor 20 is a sensor that outputs an electrical signal correlated with the temperature of the fuel flowing through the low pressure fuel passage 4. The feed pressure sensor 21 is a sensor that outputs an electrical signal correlated with the discharge pressure (feed pressure) of the low-pressure fuel pump 1.

  The ECU 15 controls the low-pressure fuel pump 1 and the intake valve 2a based on the output signals of the various sensors described above. For example, the ECU 15 adjusts the opening / closing timing of the intake valve 2a so that the output signal (actual fuel pressure) of the fuel pressure sensor 16 converges to the target value. At that time, the ECU 15 performs proportional integral control (PI control) based on the deviation between the actual fuel pressure and the target value with respect to the drive duty (ratio of solenoid energization time and non-energization time) that is the control amount of the intake valve 2a. Do. The target value described above is a value determined according to the target fuel injection amount of the fuel injection valve 7.

  In the proportional-integral control described above, the ECU 15 responds to the amount of control (feed-forward term) determined according to the target fuel injection amount and the difference between the actual fuel pressure and the target value (hereinafter referred to as “fuel pressure difference”). The drive duty is calculated by adding the control amount (proportional term) determined in this way and the control amount (integral term) obtained by integrating a part of the difference between the actual fuel pressure and the target value.

  It is assumed that the relationship between the fuel pressure difference and the feedforward term and the relationship between the fuel pressure difference and the proportional term are determined in advance by an adaptation operation using experiments or the like. In addition, the ratio of the amount added to the integral term in the difference in the fuel pressure described above is determined in advance by an adaptation operation using an experiment or the like.

  In addition, the ECU 15 executes a process (a reduction process) for reducing the target discharge pressure (target feed pressure) of the low-pressure fuel pump 1 in order to reduce the power consumption of the low-pressure fuel pump 1 as much as possible. Specifically, the ECU 15 first determines a default value of the target feed pressure based on the operating state of the internal combustion engine, the fuel temperature, and the like. Subsequently, the ECU 15 decreases the target feed pressure by a certain amount (hereinafter referred to as “decrease coefficient”). The above-described decrease coefficient is desirably set to a maximum value within a range where the fuel pressure in the low-pressure fuel passage 4 does not significantly fall below the saturated vapor pressure, and is desirably obtained in advance by an adaptation process such as an experiment. In the case where the internal combustion engine includes a port injection fuel injection valve, the target feed pressure may be determined in consideration of the amount of fuel injected from the port injection fuel injection valve.

  By the way, when fuel vapor is generated in the low pressure fuel passage 4, when the load of the internal combustion engine is high, or when the required injection amount of the fuel injection valve for port injection increases, the discharge pressure of the low pressure fuel pump 1 Need to be raised promptly. Therefore, the capacity of the low-pressure fuel pump 1 needs to be set to a size that can cover the target fuel injection amount when the internal combustion engine is in the full load operation state.

  Here, when a pump in which the number of operating impellers is always constant is used as the low-pressure fuel pump 1, there is a possibility that the pump efficiency may be lowered when the target discharge pressure is low (that is, when the target discharge amount is small). . On the other hand, as the low-pressure fuel pump 1, a method using a pump that includes a plurality of impellers and can change the number of operating impellers is conceivable. As such a pump, one that changes the number of operating impellers using electric power is known. However, when power is consumed to change the number of operating impellers, there is a possibility that the power consumption of the low-pressure fuel pump 1 cannot be reduced suitably.

  Therefore, the low-pressure fuel pump 1 of the present embodiment is configured so that the number of operating impellers can be mechanically changed. Hereinafter, the configuration of the low-pressure fuel pump 1 in the present embodiment will be described with reference to FIGS.

FIG. 2 is a diagram schematically showing the configuration of the low-pressure fuel pump 1. The low pressure fuel pump 1 includes a substantially cylindrical housing 100. In the housing 100, three spaces 101, 102, 103 formed in a columnar shape are arranged in series in the axial direction. At that time, the spaces 101, 102, 10 are arranged so that the axial centers of the three spaces 101, 102, 103 are collinear.
3 is arranged.

  A motor 101 is accommodated in a space 101 formed on the base end side (upper side in FIG. 2) of the housing 100 (hereinafter, the space 101 is referred to as “motor chamber 101”). The motor 200 includes a rotating shaft (motor shaft) 201 attached to the housing 100 so as to be rotatable in the circumferential direction of the motor chamber 101, a rotor 202 attached to the outer peripheral surface of the motor shaft 201, and the motor chamber 101. A stator 203 fixed to the inner peripheral surface, and the rotor 202 and the motor shaft 201 are rotated by electric power supplied from a battery or an alternator (not shown).

  A first impeller 120 is accommodated in a space 102 adjacent to the motor chamber 101 (hereinafter, the space 102 is referred to as a “first accommodation chamber 102”). A second impeller 130 is accommodated in the space 103 located on the distal end side (lower side in FIG. 2) of the housing 100 from the first accommodation chamber 102 (hereinafter, the space 103 is referred to as “second accommodation chamber 103”). Called). The outer diameter of the second impeller 130 is larger than that of the first impeller 120. That is, the discharge flow rate per unit time (in other words, the discharge flow rate per rotation) is larger in the second impeller 130 than in the first impeller 120.

  An inflow passage 107 communicating with the first storage chamber 102 and the second storage chamber 103 is formed in the housing 100. The inflow passage 107 communicates with the fuel tank 3 and is a passage that guides the fuel in the fuel tank 3 to the first storage chamber 102 and the second storage chamber 103. Further, the housing 100 has a first outflow passage 108 that communicates the low-pressure fuel passage 4 and the first storage chamber 102, and a second outflow passage 109 that communicates the low-pressure fuel passage 4 and the second storage chamber 103. And are provided. The first outflow passage 108 and the second outflow passage 109 are passages for guiding the fuel discharged from the first storage chamber 102 and the second storage chamber 103 to the low pressure fuel passage 4. A chuck valve that allows fuel flow from the second storage chamber 103 to the low pressure fuel passage 4 and blocks fuel flow from the low pressure fuel passage 4 to the first storage chamber 102 in the second outflow passage 109. 110 is arranged so that the fuel guided from the first storage chamber 102 to the low-pressure fuel passage 4 does not flow back to the second storage chamber 103 via the second outflow passage 109.

  A first through hole 104 is provided in the central portion of the partition wall between the motor chamber 101 and the first storage chamber 102 to allow the motor chamber 101 and the first storage chamber 102 to communicate with each other. A second through-hole 105 that allows the first storage chamber 102 and the second storage chamber 103 to communicate with each other is provided in the central portion of the partition wall between the first storage chamber 102 and the second storage chamber 103.

  The front end of the motor shaft 201 protrudes from the motor chamber 101 through the first through hole 104 and the first storage chamber 102 to the second through hole 105 and is connected to the centrifugal clutch 30 accommodated in the second through hole 105. ing. At this time, the motor shaft 201 passes through the central portion of the first impeller 120 and rotates integrally with the first impeller 120. The centrifugal clutch 30 is connected to a movable shaft 106 that is rotatably disposed in the second storage chamber 103. The movable shaft 106 passes through the central portion of the second impeller 130 and rotates with the second impeller 130 at a constant rate.

  As shown in FIG. 3, the centrifugal clutch 30 includes a columnar input shaft 31 and a cylindrical output shaft 32 disposed coaxially on the outer periphery of the input shaft 31. The input shaft 31 is connected to the motor shaft 201 of the motor 200 and rotates integrally with the motor shaft 201 and the first impeller 120. The output shaft 32 is connected to the movable shaft 106 and rotates integrally with the movable shaft 106 and the second impeller 130.

  Two projecting portions 31 a and 31 b projecting in the radial direction are provided at two locations on the outer peripheral surface of the input shaft 31 facing each other. Moreover, between the input shaft 31 and the output shaft 32, the semicircular centrifugal weights 33a and 33b provided with the groove | channel fitted to the said protrusion parts 31a and 31b are arrange | positioned so that it may mutually oppose. The centrifugal weights 33a and 33b are accommodated in the output shaft 32 so as to be movable in the radial direction while being fitted to the protrusions 31a and 31b. Further, the two centrifugal weights 33 a and 33 b are biased so as to approach each other by a biasing member (metal spring) 34. Further, friction members (shoes) are attached to the outer peripheral surfaces of the centrifugal weights 33a and 33b.

  Hereinafter, the operation of the low-pressure fuel pump 1 will be described. When the motor shaft 201 is rotated by the motor 200, the rotational force of the motor shaft 201 is transmitted to the first impeller 120 and the input shaft 31 of the centrifugal clutch 30. At this time, since the protrusions 31 a and 31 b of the input shaft 31 are fitted to the centrifugal weights 33 a and 33 b, the two centrifugal weights 33 a and 33 b also rotate in conjunction with the input shaft 31. When the centrifugal weights 33a and 33b rotate in this way, centrifugal force acts on the centrifugal weights 33a and 33b. However, when the rotational speed of the motor shaft 201 is low, the magnitude of the centrifugal force is smaller than the urging force of the urging member 34, so that the outer peripheral surfaces of the centrifugal weights 33a and 33b are output shaft 32 as shown in FIG. It is maintained in a state (non-engaged state) separated from the inner peripheral surface. Therefore, when the centrifugal force acting on the centrifugal weights 33a and 33b is smaller than the biasing force of the biasing member 34, the rotational force of the input shaft 31 is not transmitted to the output shaft 32, and only the first impeller 120 rotates. Become.

  Next, when the centrifugal force acting on the centrifugal weights 33 a and 33 b becomes larger than the urging force of the urging member 34 due to the increase in the rotation speed of the motor shaft 201, the centrifugal weights 33 a and 33 b become the projections 31 a and 31 b of the input shaft 31. Along the radial direction. When the centrifugal force acting on the centrifugal weights 33a and 33b is sufficiently larger than the urging force of the urging member 34, the outer peripheral surfaces (friction members) of the centrifugal weights 33a and 33b are connected to the output shaft as shown in FIG. It will be in the state (engaged state) pressed against the 32 inner peripheral surface. As a result, the rotational force of the input shaft 31 is transmitted to the output shaft 32. That is, the rotational force of the motor shaft 201 is transmitted to the movable shaft 106. Therefore, when the centrifugal force acting on the centrifugal weights 33a and 33b is larger than the urging force of the urging member 34, the second impeller 130 is rotated in addition to the first impeller 120.

  According to the low-pressure fuel pump 1 as described above, the engagement state and the disengagement state of the centrifugal clutch 30 can be switched by adjusting the rotation speed of the motor 200. In other words, by adjusting the rotation speed of the motor 200, the number of operating impellers can be changed. Therefore, external force such as electric power is not required when changing the number of operating impellers. As a result, it is possible to avoid a situation where the reduction in power consumption due to the above-described reduction process is reduced due to the increase in power consumption accompanying the change in the number of operation of the impeller, and the power consumption of the low-pressure fuel pump 1 can be effectively reduced. It becomes possible to reduce.

  By the way, in order to accurately control the discharge pressure (discharge amount) of the low-pressure fuel pump 1, it is also important to accurately detect the switching between the engaged state and the disengaged state of the centrifugal clutch 30. On the other hand, although a method of providing a dedicated sensor is also conceivable, there is a possibility that the number of parts increases and the centrifugal clutch 30 increases in size. Therefore, in this embodiment, the switching between the engaged state and the disengaged state of the centrifugal clutch 30 is detected based on the current consumption of the low-pressure fuel pump 1.

FIG. 5 is a diagram showing a change in current consumption of the motor 200 when the applied voltage of the motor 200 is increased when the centrifugal clutch 30 is in the non-engaged state. In addition, t1 in FIG. 5 shows the timing when the centrifugal clutch 30 switched from the non-engaged state to the engaged state. In FIG. 5, when the centrifugal clutch 30 is in a non-engaged state (non-engagement region in FIG. 5), in other words, when only the first impeller 120 is operating, the consumption current of the motor 200 is the applied voltage. It increases approximately linearly with increasing. On the other hand, when the centrifugal clutch 30 is switched from the non-engaged state to the engaged state, in other words, when the operating state of only the first impeller 120 is switched to the operating state of the first impeller 120 and the second impeller 130, The consumption current of the motor 200 shows an excessive increase with respect to the increase amount of the applied voltage. When the centrifugal clutch 30 is stabilized in the engaged state, the current consumption of the motor 200 returns to a substantially linear increasing tendency with respect to the increase in the applied voltage.

  FIG. 6 is a diagram showing a change in current consumption of the motor 200 when the applied voltage of the motor 200 is lowered when the centrifugal clutch 30 is in the engaged state. 6 indicates the timing at which the centrifugal clutch 30 is switched from the engaged state to the specific engaged state. In FIG. 6, when the centrifugal clutch 30 is in the engaged state (engagement region in FIG. 6), in other words, when the first impeller 120 and the second impeller 130 are operating, the current consumption of the motor 200 is Decreasing substantially linearly with decreasing applied voltage. On the other hand, when the centrifugal clutch 30 is switched from the engaged state to the disengaged state, in other words, when the operating state of the first impeller 120 and the second impeller 130 is switched to the operating state of only the first impeller 120, The consumption current of the motor 200 shows an excessive decrease with respect to the decrease of the applied voltage. When the centrifugal clutch 30 is stabilized in the non-engaged state, the current consumption of the motor 200 returns to a substantially linear decreasing tendency with respect to the decrease in the applied voltage.

  As described with reference to FIGS. 5 and 6, when the centrifugal clutch 30 is switched between the engaged state and the non-engaged state, the consumption current of the motor 200 changes more than the applied voltage. Therefore, the ECU 15 determines that the centrifugal clutch 30 has been switched from the engaged state to the non-engaged state or from the non-engaged state to the engaged state on the condition that the amount of change in current consumption per unit time is greater than the threshold value. can do. Here, the “threshold value” is a value obtained by adding a margin to the amount of change in applied voltage per unit time. When the ECU 15 executes such a determination process, the determination unit according to the present invention is realized.

  When the switching of the centrifugal clutch 30 is detected by such a method, the switching of the centrifugal clutch 30 can be suitably performed. For example, when the centrifugal clutch 30 is switched from the non-engaged state to the engaged state, the ECU 15 raises the applied voltage of the motor 200 above the target voltage Vtrg as shown in FIG. The applied voltage may be converged to the target voltage Vtrg when the amount of increase exceeds the threshold. When the centrifugal clutch 30 is switched from the engaged state to the non-engaged state, the ECU 15 lowers the applied voltage of the motor 200 below the target voltage Vtrg as shown in FIG. The applied voltage may be converged to the target voltage Vtrg when the amount of decrease in the hit exceeds a threshold value.

  According to the embodiment described above, the fuel of the internal combustion engine including the low pressure fuel pump 1 capable of changing the number of operation of the impeller and the high pressure fuel pump 2 for boosting the fuel discharged from the low pressure fuel pump 1. In the supply system, the power consumption of the low-pressure fuel pump 1 can be effectively reduced. Further, since the discharge amount per rotation of the first impeller 120 can be set small, the pump efficiency when the discharge amount of the low-pressure fuel pump 1 decreases can be increased.

In the present embodiment, the configuration in which the low-pressure fuel pump 1 includes two impellers has been described as an example. However, the low-pressure fuel pump 1 may include three or more impellers. In that case, one or two impellers may be fixed to the motor shaft, and the remaining two or one impeller may be fixed to the movable shaft. Moreover, each impeller may be connected via a centrifugal clutch, and the rotational speed when each centrifugal clutch is switched may be made different from each other. For example, when the rotational speed is in the low speed region, all the centrifugal clutches are disengaged (only one impeller is in operation), and when the rotational speed is in the medium speed region, only one centrifugal clutch is engaged. When the state (two impellers are in an operating state) and the rotational speed is in a high speed region, all the centrifugal clutches may be in an engaged state (three impellers are in an operating state).

DESCRIPTION OF SYMBOLS 1 Low pressure fuel pump 2 High pressure fuel pump 2a Suction valve 3 Fuel tank 4 Low pressure fuel passage 5 High pressure fuel passage 6 Delivery pipe 7 Fuel injection valve 8 Branch passage 9 Pressure regulator 10 Check valve 11 Pulsation damper 12 Return passage 13 Relief valve 14 Passage 15 ECU
16 Fuel pressure sensor 17 Intake air temperature sensor 18 Accelerator position sensor 19 Crank position sensor 20 Fuel temperature sensor 21 Feed pressure sensor 30 Centrifugal clutch 31 Input shaft 31a Protruding portion 31b Protruding portion 32 Output shaft 33a Centrifugal weight 33b Centrifugal weight 34 Energizing member 100 Housing 101 Motor chamber 102 First storage chamber 103 Second storage chamber 104 First through hole 105 Second through hole 106 Movable shaft 107 Inflow passage 108 First outflow passage 109 Second outflow passage 110 Chuck valve 120 First impeller 130 Second impeller 200 Motor 201 Motor shaft 202 Rotor 203 Stator

Claims (2)

In a fuel supply system for an internal combustion engine comprising a low-pressure fuel pump and a high-pressure fuel pump for boosting the fuel discharged by the low-pressure fuel pump,
The low-pressure fuel pump is
A first impeller that rotates in conjunction with the rotating shaft of the electric motor;
A second impeller disposed coaxially with the rotating shaft of the electric motor and rotatable relative to the rotating shaft;
A centrifugal clutch that is interposed between the rotary shaft and the second impeller and engages the rotary shaft and the second impeller by utilizing a centrifugal force generated by an increase in the rotational speed of the rotary shaft;
A fuel supply system for an internal combustion engine. In Claim 1, The detection part which detects the variation | change_quantity of the consumption current of the said electric motor,
A determination unit that determines that the engagement state and the disengagement state of the centrifugal clutch are switched when the amount of change detected by the detection unit exceeds a threshold;
A fuel supply system for an internal combustion engine further comprising:

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