JP4415894B2 - Fuel injection device - Google Patents

Description

  The present invention relates to a fuel injection device that injects and supplies fuel to an engine.

[Conventional technology]
Conventionally, in a fuel injection device, various measures have been taken in order to prevent wax precipitated with a decrease in fuel temperature while the engine is stopped from being captured by a filter and causing clogging at the next engine start. Yes. For example, in the conventional fuel injection device 100 shown in FIG. 5, by taking the measures described below, the melting of the wax is promoted and the filter 101 is prevented from being clogged at an early stage.

  That is, in the conventional fuel injection device 100, a filter 101 that removes foreign matters contained in fuel sucked into the fuel supply pump 103 is provided in a fuel suction passage 104 that connects the fuel tank 102 and the suction port of the fuel supply pump 103. It is arranged. In addition, a fuel return passage 107 that leads fuel (return fuel) returned from the injector 105, the common rail 106, and the like to the fuel tank 102 is provided, and a fuel return passage 108 that leads the return fuel to the filter 101 branches from the fuel return passage 107. And is joined to the fuel intake passage 104 upstream of the filter 101.

  A flow path switching valve 109 is disposed at a branch point of the fuel return path 108 in the fuel return path 107, and the fuel return path 107 (upstream return path 110 on the injector 105 side (upstream side of the flow path switching valve 109)). ) And the fuel return passage 107 (referred to as the downstream return passage 111) on the fuel tank 102 side (downstream from the flow path switching valve 109) and the upstream return passage 110 and the fuel. The wax trapped by the filter 105 is melted by switching the valve opening side in communication with the reflux passage 108.

  That is, since the return fuel is warmed and returned by heat transfer from the engine, when the temperature of the fuel flowing into the filter 101 (referred to as the filter inflow temperature Tf) is low, the flow path switching valve 108 is opened. The wax is melted at an early stage by introducing the warmed return fuel to the filter 101. When the filter inflow temperature Tf rises to such an extent that the wax can be sufficiently melted, the flow path switching valve 108 is closed to stop the return fuel from being guided to the filter 101 and returned to the fuel tank 102. (For example, refer to Patent Document 1).

[Problems with conventional technology]
In such a conventional fuel injection device 100, as shown in FIG. 6, the flow rate of the fuel flowing into the filter 101 (filter inflow rate) Qf starts to rise at the same time as the ignition is turned on, and eventually depends on the operating state of the engine. The predetermined value Qfconst is obtained. In the fuel injection device 100, the upper limit temperature Tc1 and the lower limit temperature Tc2 are set as the filter inflow temperature Tf as threshold values for opening and closing the flow path switching valve 109. When the filter inflow temperature Tf exceeds the upper limit temperature Tc1, the flow path switching valve 109 is closed, and the flow rate of fuel guided from the fuel recirculation passage 108 to the filter 101 (referred to as the recirculation amount Qr) becomes zero. If the filter inflow temperature Tf is lower than the lower limit temperature Tc2, the flow path switching valve 109 is opened and the recirculation amount Qr becomes the maximum value Qrmax (in FIG. 6, the return fuel temperature (return temperature) is Tr, fuel The temperature of the fuel sucked from the tank 102 (tank suction temperature) is displayed as Tt.)

For this reason, the filter inflow temperature Tf changes while vibrating up and down in a short cycle. As a result, when the engine is started, if the temperature difference between the tank suction temperature Tt and the return temperature Tr is large, the vibration width may be excessive. When the vibration width of the filter inflow temperature Tf becomes excessive, not only does the wax not melt, but also when it swings to the high temperature side, the high temperature fuel flows into the fuel supply pump 103 and the injector 105, so that these reliability can be improved. There is also a risk of adverse effects.
JP 2003-176661 A

  The present invention has been made to solve the above-described problems, and the object thereof is to suppress the filter inflow temperature from vibrating up and down and to melt the wax trapped in the filter at an early stage. It is to provide a fuel injection device.

[Means of Claim 1]
The fuel injection apparatus according to claim 1 is a fuel supply pump that sucks and pressurizes fuel in a fuel tank, an injector that injects fuel discharged from the fuel supply pump into an engine, a fuel tank, and a fuel supply pump A filter for removing foreign matter contained in the fuel sucked into the fuel supply pump, a filter inflow temperature detecting means for detecting the temperature of the fuel flowing into the filter, and a filter The upstream fuel intake passage is connected to the fuel return passage for guiding the fuel returned from the injector to the fuel tank, the fuel return passage for guiding the fuel returned from the injector to the filter, and the fuel introduced to the filter through the fuel return passage. Based on the value detected by the recirculation amount adjusting means for adjusting the recirculation amount indicating the flow rate and the filter inflow temperature detecting means, A control means for giving the recirculation amount adjusting means calculates a command value corresponding to the amount.
In addition, the control means adjusts the return flow rate indicating the flow rate of the fuel returned from the injector by changing the engine speed during idling, and the detected value by the filter inflow temperature detecting means is adjusted to the amount of fuel flowing into the filter. Make it approximately equal to the target temperature.

As a result, the reflux amount becomes a variable amount that increases or decreases in accordance with the command value calculated by the control means. Further, since the command value is calculated based on the detected value of the filter inflow temperature, the recirculation amount is adjusted to a value corresponding to the filter inflow temperature, instead of being either zero or the maximum value as in the past. The For this reason, the amount of recirculation can be freely adjusted according to the filter inflow temperature, so that the filter inflow temperature is prevented from vibrating up and down, and the filter inflow temperature is quickly raised to quickly melt the wax trapped in the filter. can do.
Further, since the amount of reflux can be increased by increasing the return flow rate, the rate of increase in the filter inflow temperature can be increased.

In addition , the control means adjusts the return flow rate by changing the engine speed during idling, so that the value detected by the filter inflow temperature detection means substantially matches the target temperature of the fuel flowing into the filter.
Thus, increasing the return flow by utilizing the increase in the idle speed performed to hasten engine warm-up, it is possible to quickly the melting of the wax.

The fuel injection device of the best mode 1 includes a fuel supply pump that sucks and pressurizes fuel in a fuel tank, an injector that injects fuel discharged from the fuel supply pump into an engine, a fuel tank, and a fuel supply pump. Than a filter that is disposed in a fuel suction passage that connects to the suction port, removes foreign matter contained in fuel sucked into the fuel supply pump, a filter inflow temperature detection means that detects the temperature of fuel flowing into the filter, and a filter The upstream fuel intake passage is connected to the fuel return passage for guiding the fuel returned from the injector to the fuel tank, the fuel return passage for guiding the fuel returned from the injector to the filter, and the flow rate of the fuel guided to the filter through the fuel return passage Based on the value detected by the filter inflow temperature detecting means and the filter inflow temperature detecting means for adjusting the reflux amount indicating A control means for giving the recirculation amount adjusting means calculates a command value corresponding to.

In addition, the control means adjusts the return flow rate indicating the flow rate of the fuel returned from the injector by changing the engine speed during idling, and the detected value by the filter inflow temperature detecting means is adjusted to the amount of fuel flowing into the filter. Make it approximately equal to the target temperature .

[Configuration of Reference Example ]
A configuration of a fuel injection device 1 of a reference example will be described with reference to FIG.
The fuel injection device 1 includes, for example, a common rail 2 that accumulates fuel in a high pressure state, and injects and supplies fuel to a diesel engine (not shown: hereinafter referred to as an engine) via the common rail 2.

  The fuel injection device 1 includes a fuel supply pump 4 that sucks and pressurizes and discharges fuel in a fuel tank 3, injection means 5 that supplies fuel discharged from the fuel supply pump 4 to an engine, a fuel tank 3, and fuel supply A filter 7 that is disposed in a fuel intake passage 6 that connects the suction port of the pump 4 to remove foreign matters contained in the fuel sucked into the fuel supply pump 4, and a temperature of the fuel that flows into the filter 7 (filter inflow temperature) A filter inflow temperature detecting means 8 for detecting Tf, a fuel intake passage 6 upstream of the filter 7, and a fuel return passage 9 for guiding the fuel returned from the injection means 5 to the fuel tank 3 are connected to each other from the injection means 5. A fuel recirculation passage 10 for guiding the returned fuel to the filter 7 and a recirculation amount adjusting means 1 for adjusting a recirculation amount Qr indicating the flow rate of the fuel guided to the filter 7 through the fuel recirculation passage 10 Based on the value detected by the detecting means such as sensors, a control unit 12 for calculating the various instruction value output.

  The fuel supply pump 4 sucks, pressurizes, and discharges the fuel in the fuel tank 3 so that the fuel in the common rail 2 is accumulated at a target pressure (target rail pressure) corresponding to the state of the engine. The fuel supply pump 4 has a suction metering valve (not shown) for metering the fuel pumped from the fuel tank 3 according to the target rail pressure.

  A pump drive current indicating the magnitude of a current supplied to a solenoid coil (not shown) of the suction metering valve is given to the suction metering valve as a command value. The pump drive current is calculated based on a deviation of the actual pressure (actual rail pressure) of the fuel accumulated in the common rail 2 with respect to the target rail pressure. Then, the solenoid coil of the intake metering valve is energized based on the pump drive current, whereby the valve opening degree of the suction metering valve is adjusted and metering according to the target rail pressure is performed.

  The injection means 5 is a common rail 2 that accumulates fuel discharged from the fuel supply pump 4 in a high-pressure state, an injector 13 that communicates with the common rail 2 and injects fuel accumulated in the common rail 2 into the cylinder of the engine.

  The common rail 2 is connected to the discharge port of the fuel supply pump 4 via a high-pressure pipe 17, receives the supply of pressurized fuel, accumulates fuel in a high-pressure state, and passes through the inlet of the injector 13 and the high-pressure pipe 18. The fuel of the actual rail pressure is supplied to the injector 13. That is, the common rail 2 functions as a pressure accumulation container that accumulates high-pressure fuel, and also functions as a distribution container that distributes high-pressure fuel to the injectors 13. The actual rail pressure is detected by a rail pressure sensor 19 attached to one end of the common rail 2, and the detected value of the actual rail pressure is output to the control means 12. The detected value of the actual rail pressure is used for calculating the pump driving current.

  In addition, a pressure reducing valve 21 that reduces the actual rail pressure by opening the valve and letting fuel from the common rail 2 to the low pressure pipe 20 is attached to the other end of the common rail 2. The pressure reducing valve 21 is given as an instruction value from the control means 12 an open command period indicating a period during which the pressure reducing valve 21 is open, that is, a period during which the solenoid coil (not shown) of the pressure reducing valve 21 is energized. It is done. The opening command period is calculated according to the difference between the actual rail pressure and the target rail pressure. Then, when the pressure reducing valve 21 is opened based on the opening command period, fuel is released from the common rail 2 to the low pressure pipe 20, and the actual rail pressure is reduced.

  The injector 13 is connected to the common rail 2 through a high-pressure pipe 18 connected thereto, and includes an injection nozzle 24 for injecting fuel into the cylinder, an electromagnetic valve 25 for operating the injection nozzle 24, and the like. The number of injectors 13 is the same as the number of cylinders (only one is shown in FIG. 1).

  As shown in FIG. 2, the injection nozzle 24 has a needle-like valve body (hereinafter referred to as an injection valve body) 27 that opens and closes the injection hole 31. The injection valve body 27 opens the injection hole 31 in the direction (opening side) by the pressure of the fuel supplied from the common rail 2 to the reservoir 30 through the high pressure passage 29 provided in the high pressure pipe 18 and the body 28. At the same time, the spring 32 disposed on the side opposite to the injection hole of the injection valve body 27 and the back pressure transmitted from the command piston 33 are urged in the direction of closing the injection hole 31 (closed side). .

  Here, the back pressure is the pressure of the fuel supplied to the back pressure chamber 34, and the back pressure chamber 34 is formed on the side opposite to the injection hole of the injection valve body 27 and closed downward by the command piston 33. ing. The back pressure chamber 34 communicates with the common rail 2 through the high pressure pipe 18 and the orifice 35, and the back pressure rises when the fuel is supplied from the common rail 2. The supply of fuel from the common rail 2 is restricted by the orifice 35. Further, the back pressure chamber 34 is opened by the valve body 36 of the electromagnetic valve 25, so that the fuel is discharged through the orifice 37 and the back pressure is lowered. The orifices 35 and 37 are provided so that the amount of fuel discharged from the orifice 37 is larger than the amount of fuel supplied from the orifice 35.

  The electromagnetic valve 25 receives a magnetic attraction force and is displaced in a direction (opening side) to open the back pressure chamber 34. The electromagnetic valve 25 receives high voltage and constant current, and opens the valve body 36 to the opening side. And a solenoid coil 38 that generates a magnetic attractive force that is held on the opening side and a spring 39 that biases the valve body 36 in the direction of closing the back pressure chamber 34 (closing side).

  The electromagnetic valve 25 is given an injection start timing and an injection period as command values from the control means 12. These command values are calculated according to the state of the engine based on the detected value of the engine speed, the detected value of the accelerator opening, the detected value of the actual rail pressure, and the like. Based on the calculated values of the injection start timing and the injection period, the control means 12 applies a high voltage to the solenoid coil 38 and energizes the solenoid coil 38 with a predetermined constant current. Thus, an amount of fuel corresponding to the engine state is injected at a time according to the engine state.

  That is, when a high voltage is applied to the solenoid coil 38 and a constant current is continuously applied, the valve body 36 is displaced to the opening side and the back pressure chamber 34 is opened, and this open state continues. The amount of fuel discharged from the chamber 34 becomes larger than the amount of fuel supplied to the back pressure chamber 34, and the back pressure decreases. Thus, the biasing force acting on the opening side of the injection valve body 27 (the biasing force due to the pressure of the fuel in the reservoir 30) acts on the closing hole side (the biasing force due to the back pressure and the spring 32). Than the urging force by). As a result, the injection valve body 27 is displaced to the opening side, the injection hole 31 is opened, and injection is performed.

  When the energization of the solenoid coil 38 is stopped, the valve body 36 is displaced to the closed chamber side, the back pressure chamber 34 is closed, and the discharge of fuel from the back pressure chamber 34 is stopped. Supply increases back pressure. Thereby, the urging force acting on the closed hole side with respect to the injection valve body 27 becomes stronger than the urging force acting on the opening side. As a result, the injection valve body 27 is displaced to the closed hole side, the injection hole 31 is closed, and the injection is stopped.

  The solenoid valve 25 is provided with a leak port 40 for leaking fuel that has not been used for injection into the fuel return passage 9 that is a low-pressure pipe. Here, the fuel leaking from the injector 13 includes a fuel caused by a static leak and a fuel caused by a dynamic leak.

  The static leak means that the fuel leaks through the sliding portion inside the injector 13. For example, the fuel in the reservoir 30 leaks from the sliding portion between the body 28 and the injection valve body 27, or the back. The fuel in the pressure chamber 34 leaks from the sliding portion between the body 28 and the command piston 33. The fuel leaking from the reservoir 30 and the back pressure chamber 34 flows into the spring chamber 41 formed between the injection valve body 27 and the command piston 33 and accommodating the spring 32, and is provided in the body 28. 42, leaks from the leak port 40 to the fuel return passage 9 through the low pressure flow path 43 provided in the electromagnetic valve 25.

  The dynamic leak means that the fuel leaks due to an intentional operation such as giving a command value to the electromagnetic valve 25 from the control means 12 like when the fuel is discharged from the back pressure chamber 34 in order to reduce the back pressure. It is to be. The fuel discharged from the back pressure chamber 34 through the orifice 37 merges with the fuel due to static leak in the low pressure channel 43 and leaks from the leak port 40 to the fuel return passage 9.

  The fuel leaking from the injector 13 to the fuel return passage 9 is warmed by heat transfer from the engine. The fuel leaked into the fuel return passage 9 is combined with the fuel released from the common rail 2 via the low-pressure pipe 20 and becomes fuel returned to the fuel tank 3 (return fuel). This return fuel is guided to the filter 7 for the early melting of the wax immediately after the engine is started.

  The filter 7 removes solid matter such as dust contained in the fuel and moisture, thereby preventing mechanical wear and rusting in the sliding parts such as the fuel supply pump 4 and the injector 13. Have

  The filter inflow temperature detection means 8 is a known temperature sensor that detects the filter inflow temperature Tf (hereinafter, the filter inflow temperature detection means 8 is referred to as the filter inflow temperature sensor 8). The filter inflow temperature sensor 8 is mounted in the fuel intake passage 6 on the inlet side of the filter 7 on the downstream side of the junction 47 with the fuel recirculation passage 10 and on the upstream side of the filter 7. . Further, the detected value (that is, the filter inflow temperature Tf) by the filter inflow temperature sensor 8 is output to the control means 12, and is used when executing the control for guiding the return fuel to the filter 7 for early melting of the wax.

  The fuel recirculation passage 10 branches from the fuel return passage 9 and joins the fuel suction passage 6 upstream of the filter 7. That is, the fuel recirculation passage 10 is a passage for connecting the fuel suction passage 6 and the fuel return passage 9 upstream of the filter 7 and guiding the return fuel to the filter 7 for early melting of the wax.

  The recirculation amount adjusting means 11 is attached to the branch point where the fuel recirculation passage 10 branches from the fuel return passage 9 to adjust the recirculation amount Qr. Specifically, the fuel return passage 9 is changed to the fuel recirculation passage 10. On the other hand, it is an electromagnetic three-way valve that opens and closes (hereinafter, the reflux amount adjusting means 11 is referred to as an electromagnetic three-way valve 11). The electromagnetic three-way valve 11 can vary the recirculation-side opening and the return-side opening in accordance with the magnitude of current supplied to a solenoid coil (not shown).

  Here, the recirculation-side opening degree is such that the fuel return passage 9 (hereinafter referred to as the upstream return passage 49) on the injection means 5 side (upstream side of the electromagnetic three-way valve 11) communicates with the fuel recirculation passage 10. Is a state quantity. The return side opening degree is such that the upstream return passage 49 and the fuel return passage 9 (hereinafter referred to as the downstream return passage 50) on the fuel tank 3 side (downstream side of the electromagnetic three-way valve 11) communicate with each other. Is a state quantity.

  The reflux side opening and the return side opening have a negative correlation with each other, and when one increases, the other decreases, and the sum of the reflux side opening and the return side opening is It is set to be a constant value (for example, 100%). When the return side opening is fully closed (0%), the return side opening is fully open (100%), and when the return side opening is fully closed (0%), the return side opening is fully open (100%). It becomes.

  The electromagnetic three-way valve 11 is supplied with a valve drive current indicating the magnitude of the current supplied to the solenoid coil as a command value from the control means 12. The valve drive current is calculated by the control means 12. Then, energization based on the valve drive current is performed on the solenoid coil of the electromagnetic three-way valve 11, whereby the reflux side opening and the return side opening are adjusted, and the amount of reflux is adjusted.

  The control means 12 calculates various command values using detection values input from various sensors such as the rail pressure sensor 19 and the filter inflow temperature sensor 8, and synthesizes a command signal based on the calculated command values. The electronic control unit (ECU) 52 is configured by various drive circuits that receive an input of a command signal synthesized and output by the ECU 52 and energize various solenoid coils. Thus, the control unit 12 calculates the command value based on the detection values input from the various sensors, and performs energization according to the calculated command value to each solenoid coil, thereby obtaining the calculated command value. Give to each device such as the electromagnetic three-way valve 11.

  The ECU 52 is configured as a computer having a known structure including a CPU that performs control processing and arithmetic processing, storage means such as a ROM and RAM that store various programs and data, an input circuit, an output circuit, and the like.

  With such a configuration, the ECU 52 includes, in addition to the rail pressure sensor 19 and the filter inflow temperature sensor 8, a rotation speed sensor 53 that detects the engine speed, an accelerator opening sensor 54 that detects the accelerator opening, and the fuel tank 3. Detection values are input from various sensors such as a tank suction temperature sensor 55 for detecting the temperature of fuel sucked into the fuel suction passage 6 (hereinafter referred to as tank suction temperature Tt). Then, the ECU 52 uses these detection values to calculate command values such as a pump drive current given to the fuel supply pump 4, an open command period given to the pressure reducing valve 21, an injection start timing given to the injector 13, and an injection period.

  Of the above sensors, the tank suction temperature sensor 55 is mounted in the fuel suction passage 6 upstream of the junction 47 and detects the tank suction temperature Tt. The value detected by the tank suction temperature sensor 55 is used for calculating the valve drive current described below.

この数式１を還流量Ｑｒについて解くと、以下の数式２が得られる。

The ECU 52 calculates a temporary value of the valve drive current (temporary valve drive current), which is a command value given to the electromagnetic three-way valve 11, based on the heat balance of the fuel flowing into the filter 7. That is, the target value of the filter inflow temperature Tf (filter inflow target temperature) is Tf *, the return fuel temperature (return temperature) is Tr, the flow rate of fuel flowing into the filter 7 (filter inflow rate) is Qf, and the filter inflow temperature. When it is assumed that Tf is substantially equal to the filter inflow target temperature Tf *, when the heat balance is taken between the upstream side and the downstream side of the junction 47, the following formula 1 is obtained.

When Equation 1 is solved for the reflux amount Qr, the following Equation 2 is obtained.

  Based on Formula 2, the ECU 52 calculates a provisional value of the reflux amount Qr. Here, the value detected by the tank suction temperature sensor 55 is applied to the value of the tank suction temperature Tt, and the value of the filter inflow target temperature Tf * is a predetermined temperature to the temperature at which the fuel is waxed (cloud point). The value set by adding the width is applied. Further, values calculated based on engine operating conditions and the like are applied to the return temperature Tr and the filter inflow rate Qf. More specifically, the value calculated based on the target rail pressure and the target value of the injection amount by the injector 13 is applied to the value of the return temperature Tr, and the value of the filter inflow flow rate Qf is the target value of the engine speed and A value calculated based on a target value of the injection amount by the injector 13 is applied.

  Then, the ECU 52 calculates a temporary target value of the return side opening of the electromagnetic three-way valve 11 based on the temporary value of the return amount Qr, and calculates a temporary valve drive current according to the temporary target value of the return side opening.

  Further, the ECU 52 calculates the valve drive current by correcting the temporary valve drive current according to the deviation between the filter inflow target temperature Tf * and the value detected by the filter inflow temperature sensor 8 (that is, the filter inflow temperature Tf). . This deviation may be calculated as a difference between the filter inflow target temperature Tf * and the filter inflow temperature Tf, or may be calculated as a ratio of the filter inflow temperature Tf to the filter inflow target temperature Tf *. Then, the temporary valve drive current is corrected by reducing or increasing in accordance with this deviation, and the final valve drive current applied to the electromagnetic three-way valve 11 is calculated.

  Then, the ECU 52 determines the duty ratio of the command signal to be output to the drive circuit (three-way valve drive circuit) 56 that energizes the solenoid coil of the electromagnetic three-way valve 11 based on the finally calculated valve drive current. Here, a known switching element is incorporated in the three-way valve drive circuit 56. The switching element is repeatedly turned on and off according to the duty ratio, so that the energization amount from the predetermined power source to the solenoid coil of the electromagnetic three-way valve 11 is adjusted to a magnitude according to the valve driving current.

  As described above, the control means 12 calculates the valve drive current as a command value corresponding to the recirculation amount Qr based on the filter inflow temperature Tf, and gives this valve drive current to the electromagnetic three-way valve 11. As a result, the recirculation side opening degree and the recirculation amount Qr are adjusted to a magnitude corresponding to the filter inflow temperature Tf, and the wax trapped by the filter 7 is melted.

[Control method of reference example ]
A control method by the fuel injection device 1 of the reference example will be described with reference to a flowchart shown in FIG. First, in step S1, it is determined whether or not the tank suction temperature Tt is lower than the filter inflow target temperature Tf *. This determination is performed by comparing the detection value by the tank suction temperature sensor with the set value of the filter inflow target temperature Tf *. The filter inflow target temperature Tf * is set by adding a predetermined temperature range to the fuel cloud point as described above.

  If it is determined in step S1 that the tank suction temperature Tt is lower than the filter inflow target temperature Tf * (YES), the process proceeds to step S2. If it is determined that the tank suction temperature Tt is not lower than the filter inflow target temperature Tf * (NO), the process proceeds to step S3, and the recirculation amount Qr is made zero. That is, the opening degree on the reflux side is set to 0% in the electromagnetic three-way valve 11.

  Next, in step S2, it is determined whether or not the filter inflow temperature Tf is higher than a predetermined lower limit temperature Tc2. This determination is performed by comparing the detected value by the filter inflow temperature sensor 8 with the set value of the lower limit temperature Tc2. The lower limit temperature Tc2 is set as a value having a difference by a predetermined temperature range with respect to the filter inflow target temperature Tf *. This temperature range is set to such a size that the filter inflow temperature Tf can be suppressed within a certain range from vibrating up and down exceeding the filter inflow target temperature Tf *.

  If it is determined in step S2 that the filter inflow temperature Tf is higher than the lower limit temperature Tc2 (YES), the process proceeds to step S4. If it is determined that the filter inflow temperature Tf is not higher than the lower limit temperature Tc2 (NO), the process proceeds to step S5, and the recirculation amount Qr is maximized. That is, the return side opening degree is set to the maximum value in the electromagnetic three-way valve 11.

  In step S4, control of the recirculation amount Qr according to the filter inflow temperature Tf is executed. That is, the provisional value of the recirculation amount Qr is calculated based on Equation 2, and the provisional target value of the recirculation side opening of the electromagnetic three-way valve 11 is calculated based on the provisional value of the recirculation amount Qr. A temporary valve drive current is calculated according to the target value. Further, the valve drive current is calculated by correcting the temporary valve drive current according to the deviation between the filter inflow target temperature Tf * and the filter inflow temperature Tf. Then, based on the finally calculated valve drive current, the duty ratio of the command signal to be output to the three-way valve drive circuit 56 is obtained.

  The three-way valve drive circuit 56 receives a command signal corresponding to the duty ratio and energizes the solenoid coil of the electromagnetic three-way valve 11 from a predetermined power source according to the valve drive current. As described above, the recirculation side opening degree is adjusted, and the recirculation amount Qr according to the filter inflow temperature Tf is controlled.

[Operation of Reference Example ]
The effect | action by the fuel-injection apparatus 1 of a reference example is demonstrated using the time chart shown in FIG. The time chart shown in FIG. 4 shows the filter inflow temperature Tf, the tank intake temperature Tt, the return temperature Tr, and the electromagnetic three-way valve 11 after the fuel supply from the fuel tank 3 to the common rail 2 and the injector 13 is started by the ignition on. The transition of the recirculation side opening, the filter inflow flow rate Qf, and the recirculation amount Qr is shown.

  First, at the same time as the ignition is turned on, the supply of fuel from the fuel tank 3 to the common rail 2, the injector 13, and the like is started. Thereby, the filter inflow flow rate Qf becomes a predetermined value Qfconst according to the operating state of the engine. Further, immediately after the ignition is turned on, since the tank suction temperature Tt is low, the recirculation side opening degree is fully open (100%), and the recirculation amount Qr becomes the maximum value Qrmax. As a result, the filter inflow temperature Tf starts to rise and the wax starts to melt.

  When the filter inflow temperature Tf becomes higher than the lower limit temperature Tc2 at time t1, the recirculation amount Qr is controlled according to the filter inflow temperature Tf. As a result, the filter inflow temperature Tf substantially stabilizes to coincide with the filter inflow target temperature Tf *, and the recirculation side opening degree and the recirculation amount Qr are respectively values X * and Qr * corresponding to the filter inflow target temperature Tf *. become. Thereby, the wax is completely melted. Moreover, since the return fuel which is not recirculated to the filter 7 is returned to the fuel tank 3, the tank suction temperature Tt also rises.

  Note that the state where the filter inflow temperature Tf is substantially consistent with the filter inflow target temperature Tf * is stable until the tank suction temperature Tt substantially coincides with the filter inflow target temperature Tf *. When the tank suction temperature Tt substantially coincides with the filter inflow target temperature Tf *, the recirculation side opening is fully closed (0%), and the recirculation amount Qr becomes zero. Thereby, control of the recirculation | reflux amount Qr according to filter inflow temperature Tf is complete | finished.

[Effects of Reference Example ]
The fuel injection device 1 of the reference example includes a filter 7 that removes foreign matters contained in fuel sucked into the fuel supply pump 4, a filter inflow temperature sensor 8 that detects a filter inflow temperature Tf, and a fuel intake upstream of the filter 7. The passage 6 is connected to a fuel return passage 9 that guides return fuel to the fuel tank 3, a fuel return passage 10 that guides return fuel to the filter 7, an electromagnetic three-way valve 11 that adjusts the return amount Qr, and a filter inflow temperature Tf. And a control means 12 for calculating a valve driving current as a command value corresponding to the recirculation amount Qr and giving the calculated value to the solenoid coil of the electromagnetic three-way valve 11.

  Thereby, the recirculation amount Qr becomes a variable amount that increases or decreases in accordance with the valve drive current calculated by the control means 12. Further, since the valve drive current is calculated based on the detection value of the filter inflow temperature sensor 8, the recirculation amount Qr is not equal to either zero or the maximum value Qrmax as in the prior art, but is equal to the filter inflow temperature Tf. The value is adjusted accordingly. For this reason, since the recirculation amount Qr can be freely adjusted according to the filter inflow temperature Tf, the filter inflow temperature Tf is prevented from oscillating up and down, and the filter inflow temperature Tf is quickly raised and captured by the filter 7. The wax can be melted early.

Further, the ECU 52 takes a heat balance between the fuel flowing into the filter 7 on the upstream side and the downstream side of the junction 47, calculates a temporary valve drive current based on the heat balance, and corrects the temporary valve drive current. Finally, the valve drive current is calculated.
As a result, the filter inflow target temperature Tf * can be set and the valve drive current can be calculated, so that the filter inflow temperature Tf oscillates up and down without applying an excessive load to the fuel injection device 1. In addition, the wax trapped in the filter 7 can be melted at an early stage.

Further, the ECU 52 finally calculates the valve driving current by correcting the temporary valve driving current according to the deviation between the filter inflow target temperature Tf * and the detected value by the filter inflow temperature sensor 8.
As a result, the recirculation amount Qr is adjusted according to the deviation of the filter inflow temperature Tf from the filter inflow target temperature Tf *, so that it is possible to reliably suppress the filter inflow temperature Tf from vibrating up and down .

〔Example〕
In the fuel injection device 1 according to the embodiment, the control unit 12 adjusts the return flow rate indicating the flow rate of the return fuel, thereby increasing the filter inflow temperature Tf and substantially matching the filter inflow target temperature Tf *. That is, by opening the return side opening of the electromagnetic three-way valve 11 and setting the return amount Qr to the maximum value Qrmax, the filter inflow temperature Tf is increased and the return flow rate is increased while the return side opening is kept fully open. By increasing the maximum value Qrmax itself, the increase in the filter inflow temperature Tf can be accelerated.

The increase in the return flow rate can be achieved by increasing the engine speed (idle speed) during idling. That is, if the number of injections by the injector 13 per unit time is increased in order to increase the idle speed, the amount of dynamic leak from the back pressure chamber 34 per unit time can be increased. As a result, the return flow rate can be increased and the filter inflow temperature Tf can be raised earlier. Further, the idling engine speed is set to increase when the engine is at a low temperature in order to accelerate the warm-up of the engine. Therefore, it is possible to increase the return flow rate and increase the maximum value Qrmax without particularly changing the control method or the like.

[Modification]
In the electromagnetic three-way valve 11 of the fuel injection device 1 of the present embodiment, the return side opening is adjusted by changing the energization amount to the solenoid coil according to the duty ratio. Can also be adjusted.
Although the fuel injection device 1 of the present embodiment injects and supplies fuel to a diesel engine, it can also be applied to a device that injects and supplies fuel to a gasoline engine.

It is a block diagram of a fuel injection device ( reference example ). It is a block diagram of an injector ( reference example ). It is a flowchart which shows the process by a fuel-injection apparatus ( reference example ). (A) is a time chart showing changes in filter inflow temperature, tank suction temperature, and return temperature, (b) is a time chart showing changes in recirculation side opening, and (c) is a filter inflow rate and recirculation amount. It is a time chart which shows transition of ( reference example ). It is a block diagram of a fuel injection device (conventional example). (A) is a time chart which shows transition of filter inflow temperature, tank suction temperature, and return temperature, (b) is a time chart which shows transition of the open / close state of a flow path switching valve, (c) is filter inflow flow rate. It is a time chart which shows transition of recirculation | reflux amount (conventional example).

1 fuel injection device 3 fuel tank 4 fuel supply pump
6 Fuel intake passage 7 Filter 8 Filter inflow temperature sensor (filter inflow temperature detecting means)
9 Fuel return passage 10 Fuel return passage 11 Electromagnetic three-way valve (reflux amount adjusting means)
12 Control means
13 Injector Tf Filter inflow temperature (temperature of fuel flowing into the filter)
Qr Reflux amount Tf * Filter inflow target temperature (target temperature of fuel flowing into the filter)

Claims (1)

A fuel supply pump that sucks and pressurizes fuel in the fuel tank;
An injector for injecting and supplying fuel discharged from the fuel supply pump to the engine;
A filter that is disposed in a fuel suction passage that connects the fuel tank and a suction port of the fuel supply pump, and removes foreign matters contained in the fuel sucked into the fuel supply pump;
Filter inflow temperature detecting means for detecting the temperature of the fuel flowing into the filter;
A fuel recirculation passage that connects a fuel intake passage upstream of the filter and a fuel return passage that guides fuel returned from the injector to the fuel tank, and guides fuel returned from the injector to the filter;
A recirculation amount adjusting means for adjusting a recirculation amount indicating a flow rate of the fuel guided to the filter through the fuel recirculation passage;
Control means for calculating a command value corresponding to the recirculation amount based on a detection value by the filter inflow temperature detection means and giving the recirculation amount adjustment means,
The control means, by changing the engine speed during idle operation, by adjusting the return flow showing the flow rate of the fuel returned from the injector, the value detected by the filter inlet temperature detecting means, flows into the filter A fuel injection device characterized by substantially matching a target temperature of fuel .

Images