JP2007077967A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device 1 wherein an actual injection amount to the same command value is not changed even when oil-tight force in a back pressure control chamber is lowered with sliding wear. <P>SOLUTION: The return flow amount of fuel to leak from an injector 5 is adjusted by a throttle valve 7 provided in a fuel return pipe 6. Thus, valve chest pressure on a control valve which opens/closes the back pressure control chamber can be increased/reduced. A timing for starting a reduction of back pressure or a timing for finishing an increase of back pressure is controlled to vary a timing for starting/finishing injection. As a result, a change of the actual injection amount is suppressed even when oil-tight force in the back pressure control chamber is lowered. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

[Conventional technology]
Conventionally, for example, a fuel supply pump that sucks fuel from a fuel tank and pressurizes and discharges the fuel, a common rail that accumulates fuel discharged from the fuel supply pump in a high-pressure state, and a fuel that is accumulated in the common rail as an engine cylinder. 2. Description of the Related Art There is known a fuel injection device that includes an injector that injects fuel into the inside and a control unit that controls operations of a fuel supply pump, an injector, and the like.

  Here, as shown in FIG. 6, the injector 100 is configured such that the injection nozzle 102 is attached to the front end side of the main body 101 and the actuator such as the electromagnetic valve 103 is attached to the rear end side of the main body 101.

  The main body 101 accommodates the command piston 105 slidably in the axial direction. The command piston 105 forms a back pressure control chamber 107 together with the main body 106 and transmits the back pressure to the injection valve 109. Here, the back pressure is the pressure exerted on the command piston 105 by the fuel in the back pressure control chamber 107, and is transmitted to the injection valve 109 via the piston pin 110, and the injection valve 109 is closed (the injection hole 111). In the closing direction). The back pressure control chamber 107 communicates with the inside of the common rail via the high pressure channel 112 and the in-orifice 113, and is supplied with high pressure fuel. The fuel in the back pressure control chamber 107 is almost equal to the fuel pressure in the common rail. An equivalent back pressure is applied to the command piston 105.

  A spring chamber 115 that houses a spring 114 that urges the injection valve 109 in the closing direction is formed on the distal end side of the command piston 105. In addition, the fuel leaked from the back pressure control chamber 107 and the reservoir 117 flows into the spring chamber 115. That is, the high pressure fuel leaked from the clearance between the sliding surface on the command piston 105 side and the sliding surface on the main body body 106 side, and the clearance between the sliding surface on the injection valve 109 side and the sliding surface on the nozzle body 118 side. Flows into the spring chamber 115. The fuel in the spring chamber 115 leaks to the outside of the injector 100 via the low pressure channel 119 and the control valve chamber 121, and is returned to the fuel tank (not shown).

  The injection nozzle 102 accommodates the injection valve 109 slidably in the axial direction. The injection valve 109 opens and closes the injection hole 111, and forms a pool portion 117 together with the nozzle body 118. The reservoir 117 communicates with the inside of the common rail via the high-pressure channel 123 and receives supply of high-pressure fuel. The fuel in the pool portion 117 exerts pressure on the injection valve 109 in the opening direction (direction in which the injection hole 111 is opened).

  The electromagnetic valve 103 includes a solenoid coil 125 that generates a magnetic attractive force when energized, a control valve 126 that moves in the axial direction by the magnetic attractive force to open the back pressure control chamber 107, and a closing direction (closes the back pressure control chamber 107). Spring 127 for urging the control valve 126 in the direction). The electromagnetic valve 103 houses the control valve 126 and forms a control valve chamber 121 through which fuel discharged from the back pressure control chamber 107 passes. The control valve 126 opens and closes between the back pressure control chamber 107 and the control valve chamber 121 as the solenoid coil 125 repeatedly receives energization start and energization stop.

  That is, when the solenoid coil 125 is energized and a magnetic attractive force is generated, the magnetic attractive force acts on the control valve 126 in the opening direction (the direction in which the back pressure control chamber 107 is opened). Further, the magnetic attractive force is set to be stronger than the urging force (closed chamber urging force) acting in the closing direction such as the urging force by the spring 127 and the urging force by the pressure of the fuel in the control valve chamber 121 (valve chamber pressure). Has been. For this reason, when the solenoid coil 125 is energized and a magnetic attractive force is generated, the back pressure control chamber 107 is opened and fuel flows out. Further, when the energization to the solenoid coil 125 is stopped and the magnetic attractive force disappears, the back pressure control chamber 107 is closed and the outflow of fuel stops.

  An out-orifice 129 is provided in the flow path from the back pressure control chamber 107 to the control valve chamber 121. The out-orifice 129 is more than the in-orifice 113 when pressure is applied by the high-pressure fuel of the common rail. It is provided so that the passage flow rate becomes large. For this reason, when the space between the back pressure control chamber 107 and the control valve chamber 121 is opened by the control valve 126, the back pressure decreases. Further, when the space between the back pressure control chamber 107 and the control valve chamber 121 is closed by the control valve 126, the outflow of fuel from the out orifice 129 stops and only the inflow of fuel from the in orifice 113 continues. The pressure rises. The fuel that flows into the control valve chamber 121 from the back pressure control chamber 107 leaks to the outside of the injector 100 together with the fuel that flows into the control valve chamber 121 from the spring chamber 115 and is returned to the fuel tank.

  When the back pressure control chamber 107 is opened by the control valve 126 and the back pressure is reduced, the biasing force acting on the injection valve 109 in the opening direction (opening biasing force) such as the biasing force due to the fuel pressure in the reservoir 117. ) Becomes stronger than the urging force acting in the closing direction (closing urging force) such as the urging force by the back pressure and the urging force by the spring 114. For this reason, the injection hole 109 is opened by the injection valve 109, and fuel injection starts. When the back pressure control chamber 107 is closed by the control valve 126 and the back pressure rises, the closing biasing force becomes stronger than the opening biasing force. For this reason, the injection hole 109 is closed by the injection valve 109, and fuel injection stops.

  The control means controls the fuel injection by the injector 100 by instructing the opening start timing (injection start timing) of the injection hole 111 and the opening period (injection period) of the injection hole 111 according to the state of the engine. ing. That is, the control means calculates the energization start timing and the energization period for the solenoid coil 125 as command values according to the operating state of the engine, and energizes the solenoid coil 125 according to the command values.

[Problems with conventional technology]
By the way, with the aging of the injector 100, between the sliding surface on the command piston 105 side and the sliding surface on the main body body 106 side, the sliding surface on the injection valve 109 side, and the sliding surface on the nozzle body 118 side, During this time, sliding wear occurs, and the oil tightness of the back pressure control chamber 107 and the reservoir 117 decreases.

  For this reason, for example, when the oil tightness of the back pressure control chamber 107 is reduced, the energizing force and the opening force are closed even when energization to the solenoid coil 125 is started based on a command value having the same magnitude as the energization start timing. The time when the urging force balances becomes earlier. As a result, as shown in FIG. 7, the injection start timing, that is, the timing at which the injection rate starts to increase is also advanced. Further, even when the energization to the solenoid coil 125 is stopped based on the command value having the same magnitude as the energization period, the timing at which the closing biasing force and the opening biasing force are balanced is delayed. As a result, the injection end timing, that is, the timing when the injection rate becomes zero is also delayed. As a result, even if a command value having the same magnitude is calculated as the energization start timing and the energization period, the actual injection amount increases.

In addition, a technique for improving a low-pressure flow path or the like has been proposed so that bubbles generated with opening and closing of the back pressure control chamber by the control valve can be discharged to the outside of the injector at an early stage (see, for example, Patent Document 1). . However, this technique aims to stabilize the operation of the control valve by early discharge of bubbles, and does not cope with a decrease in oil tightness due to sliding wear as described above.
JP-A-11-141428

  The present invention has been made in order to solve the above-described problems. The purpose of the present invention is to reduce the actual injection amount with respect to the same command value even if the oil tightness of the back pressure control chamber or the like decreases due to sliding wear. The object is to provide a fuel injection device that does not fluctuate.

[Means of Claim 1]
The fuel injection device according to claim 1 is an injection valve that opens and closes an injection hole, and a control valve that opens and closes a return flow path that communicates a back pressure control chamber formed on the side opposite to the injection hole of the injection valve and a low pressure side. The fuel is injected and supplied through the nozzle hole by the opening operation of the injection valve, the fuel in the back pressure control chamber is returned to the low pressure side by the opening operation of the control valve, and the return flow rate of the fuel returned by the opening operation of the control valve is Squeeze in the return channel downstream of the control valve.

  Thereby, since the valve chamber pressure can be increased, the closing force for closing the chamber can be increased. For this reason, the opening time of the back pressure control chamber by the control valve can be delayed and the closing time of the back pressure control chamber by the control valve can be advanced. The start time of the accompanying back pressure rise can be advanced. As a result, even when the oil tightness of the back pressure control chamber is reduced, it is possible to maintain the same timing when the closing biasing force and the opening biasing force are balanced by the start of energization. Similarly, the same timing can be maintained when the closing biasing force and the opening biasing force are balanced by stopping energization. From the above, it is possible to provide a fuel injection device in which the actual injection amount with respect to the same command value does not fluctuate even if the oil tightness of the back pressure control chamber is reduced due to sliding wear.

  The “low pressure side” means a flow path, a container, or the like in which low pressure fuel exists before being pressurized by the fuel supply pump, such as a fuel tank and a fuel flow path in the vicinity thereof.

[Means of claim 2]
According to the fuel injection device of the second aspect, the throttle valve that varies the degree of opening is disposed in the downstream return flow path, and the return flow rate is adjusted by varying the degree of opening of the throttle valve.
As a result, the valve chamber pressure can be increased or decreased by adjusting the return flow rate with the throttle valve, so that the chamber closing biasing force can be operated freely. For this reason, the return flow rate can be adjusted according to the oil tightness of both the back pressure control chamber and the reservoir, and the fluctuation of the actual injection amount with respect to the same command value can be suppressed.

  For example, when the oil tightness of the reservoir portion decreases, the time when the closing biasing force and the opening biasing force are balanced by the start of energization is delayed, contrary to the case where the oil tightness of the back pressure control chamber is reduced, When the energization is stopped, the time when the closing biasing force and the opening biasing force are balanced is advanced. For this reason, as shown in FIG. 8, even if the energization to the solenoid coil is started based on the same command value as the energization start timing, the injection start timing, that is, the timing at which the injection rate starts to rise is delayed. Further, even when the energization to the solenoid coil is stopped based on the same command value as the energization period, the injection end timing, that is, the timing when the injection rate becomes zero is advanced. As described above, even if the same command value is calculated as the energization start timing and the energization period, the actual injection amount decreases.

  Thus, the increase / decrease direction of the actual injection amount is different between when the oil tightness of the reservoir portion is significantly reduced and when the oil tightness of the back pressure control chamber is significantly reduced. In contrast, if the return flow rate is adjusted by the throttle valve as described above so that the closing urging force can be freely operated, it is possible to cope with any decrease in the oil tightness of the back pressure control chamber and the reservoir. Can do.

[Means of claim 3]
The fuel injection device according to claim 3 is an injection valve that opens and closes an injection hole, a control valve that opens and closes a return passage that communicates a back pressure control chamber formed on the counter-injection hole side of the injection valve and a low pressure side, And a throttle valve that is arranged in the return flow path upstream of the control valve and has a variable opening degree. The fuel is injected through the injection hole by the opening operation of the injection valve, and the back pressure is supplied by the opening operation of the control valve. The fuel in the control chamber is returned to the low pressure side, and the return flow rate of the fuel returned by the opening operation of the control valve is adjusted by varying the opening degree of the throttle valve.
This means shows another form having the same effect as the means of claim 2.

[Means of claim 4]
According to the fuel injection device of the fourth aspect, the return flow rate is adjusted in accordance with the injection state quantity corresponding to at least one of the combustion temperature of the injected fuel and the flow rate of the fuel supplied to the nozzle hole. .
If the actual injection amount for the same command value varies, at least one of the combustion temperature of the fuel supplied by injection and the flow rate of the fuel supplied to the injection hole also vary. Therefore, if the return flow rate is adjusted in accordance with the injection state quantity corresponding to at least one of the combustion temperature of the fuel supplied to the injection and the flow rate of the fuel supplied to the nozzle hole, the fluctuation of the actual injection quantity with respect to the same command value Can be suppressed.

[Means of claim 5]
According to the fuel injection device of the fifth aspect, the injection state quantity is the engine speed.
Even if the command value is the same, if the engine speed is high, it can be determined that the actual injection amount has increased. Conversely, if the engine value is low even if the command value is the same, Therefore, it can be determined that the actual injection amount is decreasing. Therefore, if the engine speed is adopted as the injection state quantity and the return flow rate is adjusted according to the engine speed, fluctuations in the actual injection quantity with respect to the same command value can be suppressed.

[Means of claim 6]
According to the fuel injection device of the sixth aspect, the injection state quantity is the accelerator opening.
Even if the command value is the same, if the accelerator opening is small, it can be determined that the actual injection amount has increased. Conversely, if the accelerator opening is large even if the command value is the same, Therefore, it can be determined that the actual injection amount is decreasing. Therefore, if the accelerator opening is employed as the injection state quantity and the return flow rate is adjusted according to the accelerator opening, fluctuations in the actual injection quantity with respect to the same command value can be suppressed.

[Means of Claim 7]
According to the fuel injection device of the seventh aspect, the injection state quantity is the exhaust temperature.
Even if the command value is the same, if the exhaust gas temperature is high, it can be determined that the actual injection amount has increased. Conversely, if the exhaust gas temperature is low even if the command value is the same, the actual injection amount can be determined. It can be determined that the injection amount is decreasing. Therefore, if the exhaust gas temperature is adopted as the injection state quantity and the return flow rate is adjusted according to the exhaust gas temperature, fluctuations in the actual injection quantity with respect to the same command value can be suppressed.

[Means of Claim 8]
The fuel injection device according to claim 8 has a fuel supply pump that sucks and pressurizes fuel from a fuel tank, a common rail that accumulates fuel discharged from the fuel supply pump, an injection valve, and a control valve. And an injector for injecting and supplying fuel distributed from the common rail.

  The fuel injection device of the best mode 1 includes an injection valve that opens and closes an injection hole, and a control valve that opens and closes a return flow path that communicates a back pressure control chamber formed on the side opposite to the injection hole of the injection valve and a low pressure side. The fuel is injected and supplied through the nozzle hole by the opening operation of the injection valve, the fuel in the back pressure control chamber is returned to the low pressure side by the opening operation of the control valve, and the return flow rate of the fuel returned by the opening operation of the control valve is Throttle in the return flow path downstream of the control valve. That is, a throttle valve that varies the degree of opening is disposed in the downstream return flow path, and the fuel injection device adjusts the return flow rate by varying the degree of opening of the throttle valve.

  Further, according to this fuel injection device, the return flow rate is adjusted in accordance with the injection state quantity corresponding to at least one of the combustion temperature of the supplied fuel and the flow rate of the fuel supplied to the nozzle hole. The injection state quantity of the fuel injection device is the engine speed.

  The fuel injection device has a fuel supply pump that sucks and pressurizes fuel from a fuel tank, a common rail that accumulates fuel discharged from the fuel supply pump, an injection valve, and a control valve. And an injector for injecting and supplying the distributed fuel.

[Configuration of Example 1]
A configuration of the fuel injection device 1 according to the first embodiment will be described with reference to FIGS. 1 to 3.
The fuel injection device 1 injects and supplies fuel to, for example, a direct injection type engine such as a diesel engine. As shown in FIG. 1, a fuel supply pump that sucks fuel from a fuel tank 2 and pressurizes and discharges the fuel. 3 and a common rail 4 for accumulating the fuel discharged from the fuel supply pump 3, and each cylinder of an engine (not shown), receiving fuel distribution from the common rail 4 and opening the valve to open the fuel An injector 5 that is injected into the cylinder; a fuel return pipe 6 that returns fuel leaking from the injector 5 to the fuel tank 2; a throttle valve 7 that is disposed in the fuel return pipe 6 and adjusts the return flow rate; and a fuel supply pump 3 And a control means 8 for controlling the operation of the injector 5 and the throttle valve 7 and the like.

  The control means 8 calculates various command values to be given to each device such as the injector 5 based on detection signals input from various sensors, and outputs from the microcomputer 9 as a command signal. It is composed of various drive circuits that feed power to each device from an in-vehicle power supply (not shown) in accordance with a command signal.

  Here, the command value is, for example, a pump command value given to the fuel supply pump 3, an injector command value given to the injector 5, a throttle valve command value given to the throttle valve 7, etc. A pump drive circuit 13 that feeds power to the pump 3, an injector drive circuit 14 that feeds power to the injector 5, a throttle valve drive circuit 15 that feeds power to the throttle valve 7, and the like.

  The fuel supply pump 3 is a low pressure pump (not shown) for pumping fuel from the fuel tank 2, and an intake metering valve 17 for metering the pumped fuel in accordance with the target pressure (target rail pressure) of the fuel in the common rail 4. And a high-pressure pump 19 for pressurizing the sucked fuel and discharging it to the high-pressure pipe 18. The fuel pumped up from the fuel tank 2 is sucked in by the suction metering valve 17 after foreign matters are removed by the filter 20.

  The intake metering valve 17 has its valve opening adjusted in accordance with the amount of current supplied to a solenoid coil (not shown). In other words, the suction metering valve 17 is supplied with a drive current from the pump drive circuit 13 based on a command signal from the microcomputer 9.

  Here, the value of the drive current corresponds to a pump command value, and this pump command value is calculated as an energization amount necessary for the valve opening degree of the intake metering valve 17 to be a target value. The target value of the valve opening is calculated as the valve opening required for the actual pressure (actual rail pressure) of the common rail 4 and the target rail pressure to substantially match. Then, a drive current corresponding to the pump command value is energized to the solenoid coil of the suction metering valve 17, whereby the valve opening of the suction metering valve 17 is adjusted, and metering according to the target rail pressure is performed. .

  The common rail 4 is connected to the discharge port of the high-pressure pump 19 via the high-pressure pipe 18, receives the supply of pressurized fuel, accumulates the fuel in a high-pressure state, and is connected to each injector 5 via the high-pressure pipe 23. The fuel at the actual rail pressure is distributed to each injector 5. That is, the common rail 4 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 5.

  A rail pressure sensor 24 that detects the actual rail pressure and outputs the detected value to the microcomputer 9 as a detection signal is attached to one end of the common rail 4. Further, a pressure limiter 25 is mounted at the other end, which opens when the actual rail pressure exceeds the limit value and suppresses the actual rail pressure to the limit value or less. The fuel escaped from the common rail 4 returns to the fuel tank 2 together with the fuel leaked from the injector 5.

  As shown in FIG. 2, the injector 5 is configured such that an injection nozzle 28 is attached to the front end side of the main body 27 and an actuator such as an electromagnetic valve 29 is attached to the rear end side of the main body 27. Here, the injection nozzle 28 includes an injection valve 32 that opens and closes the injection hole 31, and the electromagnetic valve 29 includes a control valve 35 that opens and closes the back pressure control chamber 34. The injection nozzle 28 and the electromagnetic valve 29 are attached to the main body 27 by tightening a retaining nut (not shown).

  The main body 27 accommodates the command piston 37 so as to be slidable in the axial direction. The command piston 37 forms a back pressure control chamber 34 together with the main body 38 on the side opposite to the injection hole of the injection valve 32, and transmits the back pressure to the injection valve 32. Here, the back pressure is the pressure exerted on the command piston 37 by the fuel in the back pressure control chamber 34, and is transmitted to the injection valve 32 via the piston pin 39, and the injection valve 32 is closed (the injection hole 31). In the closing direction). The back pressure control chamber 34 communicates with the inside of the common rail 4 through the high pressure pipe 23, the high pressure flow path 40, and the in-orifice 41, and is supplied with high pressure fuel. A back pressure substantially equal to the pressure is applied to the command piston 37.

  A spring chamber 43 that houses a spring 42 that biases the injection valve 32 in the closing direction is formed on the tip end side of the command piston 37. In addition, the fuel leaked from the back pressure control chamber 34 and a pool portion 47 described later flows into the spring chamber 43. That is, the high-pressure fuel leaked from the clearance between the sliding surface on the command piston 37 side and the sliding surface on the main body 38 side and the clearance between the sliding surface on the injection valve 32 side and the sliding surface on the nozzle body 48 side. Flows into the spring chamber 42. The fuel in the spring chamber 42 leaks to the fuel return pipe 6 outside the injector 5 through the low pressure passage 50 and a control valve chamber 52 described later.

  The injection nozzle 28 accommodates the injection valve 32 slidably in the axial direction. The injection valve 32 opens and closes the injection hole 31 and injects and supplies fuel through the injection hole 31 by an opening operation. In addition, the injection valve 32 forms a reservoir 47 together with the nozzle body 48. The reservoir 47 communicates with the inside of the common rail 4 through the high-pressure pipe 23 and the high-pressure channel 54 and receives supply of high-pressure fuel. The fuel in the pool portion 47 exerts a pressure acting on the injection valve 32 in the opening direction (direction in which the injection hole 31 is opened).

  The electromagnetic valve 29 includes a solenoid coil 56 that generates a magnetic attractive force when energized, a control valve 35 that moves in the axial direction by the magnetic attractive force to open the back pressure control chamber 34, and a closing direction (closes the back pressure control chamber 34). Spring 57 for urging the control valve 35 in the direction). The electromagnetic valve 29 houses the control valve 35 and forms a control valve chamber 52 through which fuel flowing out from the back pressure control chamber 34 passes. Then, when the solenoid coil 56 repeatedly receives energization start and energization stop, the control valve 35 opens and closes between the back pressure control chamber 34 and the control valve chamber 52 (that is, opens and closes the back pressure control chamber 34). .

  That is, the control valve 35 opens and closes a return flow path that communicates the back pressure control chamber 34 and the fuel tank 2. Here, the return flow path is a flow path through which the fuel in the back pressure control chamber 34 is returned to the fuel tank 2, and a fuel flow path from the back pressure control chamber 34 to the control valve chamber 52, a control valve It is comprised by the chamber 52, the fuel return piping 6, etc. The control valve 35 returns the fuel in the back pressure control chamber 34 to the fuel tank 2 through the return flow path by the opening operation.

  When the solenoid coil 56 is energized and a magnetic attractive force is generated, the magnetic attractive force acts on the control valve 35 in the opening direction (the direction in which the back pressure control chamber 34 is opened). Further, the magnetic attractive force is set to be stronger than the urging force (closed chamber urging force) acting in the closing direction such as the urging force by the spring 57 and the urging force by the pressure of the fuel in the control valve chamber 52 (valve chamber pressure). Has been. For this reason, when the solenoid coil 56 is energized and a magnetic attractive force is generated, the back pressure control chamber 34 is opened and fuel flows out. When the energization of the solenoid coil 56 is stopped and the magnetic attractive force disappears, the back pressure control chamber 34 is closed and the outflow of fuel is stopped.

  An out orifice 59 is provided in the fuel flow path from the back pressure control chamber 34 to the control valve chamber 52. The out-orifice 59 is provided so that the passage flow rate is larger than that of the in-orifice 41 on the inflow side when pressure is applied by the high-pressure fuel of the common rail 4. For this reason, when the space between the back pressure control chamber 34 and the control valve chamber 52 is opened, the back pressure decreases. When the space between the back pressure control chamber 34 and the control valve chamber 52 is closed, the outflow of fuel from the out orifice 59 stops and only the inflow of fuel from the in orifice 41 continues, so the back pressure increases. . The fuel flowing out from the back pressure control chamber 34 and flowing into the control valve chamber 52 leaks into the fuel return pipe 6 together with the fuel flowing into the control valve chamber 52 from the spring chamber 43.

  When the back pressure control chamber 34 is opened by the control valve 35 and the back pressure is lowered, a biasing force acting on the injection valve 32 in the opening direction (opening biasing force) such as a biasing force due to the fuel pressure in the reservoir 47. ) Becomes stronger than the urging force acting in the closing direction (closing urging force) such as the urging force by the back pressure and the urging force by the spring 42. For this reason, the injection hole 32 is opened by the injection valve 32, and fuel injection is started. Further, when the back pressure control chamber 34 is closed by the control valve 35 and the back pressure rises, the closing biasing force becomes stronger than the opening biasing force. For this reason, the injection hole 32 is closed by the injection valve 32, and fuel injection stops.

  Here, a drive current having a pattern corresponding to the injector command value is applied from the injector drive circuit 14 to the electromagnetic valve 29 based on a command signal from the microcomputer 9. The injector command value is, for example, the energization start timing and the energization period for the solenoid coil 56, and these command values are injected and supplied with an injection amount of fuel according to the engine state at a time according to the engine state. Is calculated as follows. Then, fuel injection is performed by energizing the solenoid coil 56 with a drive current having a pattern corresponding to the injector command value.

  The throttle valve 7 is disposed in the fuel return pipe 6, which is a return flow path downstream of the control valve 35, and the flow rate of fuel leaked from the injector 5, that is, the flow rate of fuel returned from the injector 5 to the fuel tank 2. (Return flow rate) is adjusted. Here, the fuel returned to the fuel tank 2 is the clearance between the sliding surface on the command piston 37 side and the sliding surface on the main body 38 side, and the sliding surface on the injection valve 32 side and the sliding side on the nozzle body 48 side. The fuel leaked from the clearance with the surface flows into the spring chamber 43, and further flows into the control valve chamber 52 via the low-pressure channel 50, and the fuel in the back pressure control chamber 34 is controlled by the opening operation of the control valve 35. It has flowed into the valve chamber 52.

  As shown in FIG. 3, the throttle valve 7 includes a valve portion 61 that opens and closes the fuel return pipe 6, a movable element 62 that is displaced in the valve opening direction by receiving a magnetic attractive force, and an energization of a drive current, A solenoid coil 63 that generates a magnetic attraction force that moves the valve 62 in the valve opening direction, a stator 64 that is excited by energization of the solenoid coil 63 and magnetically attracts the mover 62, and is arranged between the mover 62 and the stator 64. And a spring 65 or the like that biases the mover 62 in the valve closing direction. The throttle valve 7 adjusts the return flow rate by changing the opening degree by the mover 62.

  Based on the command signal from the microcomputer 9, the throttle valve 7 is supplied with a drive current corresponding to the throttle valve command value from the throttle valve drive circuit 15. As will be described later, the throttle valve command value is calculated, for example, according to the detected value of the engine speed. Then, when a drive current having a magnitude corresponding to the throttle valve command value is supplied to the solenoid coil 63, the valve opening degree of the throttle valve 7 is adjusted and the return flow rate is adjusted.

  The microcomputer 9 is a computer having a well-known structure including a CPU that performs control processing and arithmetic processing, a ROM that stores various programs, data, and the like, storage means such as a RAM, an input circuit, and an output circuit. 1, the microcomputer 9 includes a rail pressure sensor 24, an engine speed sensor 68 that detects the engine speed, an accelerator position sensor 69 that detects the accelerator position, and an exhaust temperature sensor 70 that detects the exhaust temperature. The detection signals input from various sensors such as A / D are converted into detection values. Then, the microcomputer 9 calculates a pump command value, an injector command value, a throttle valve command value, and the like based on these detected values, synthesizes a command signal based on these command values, and sends them to the drive circuits 13-15. Output.

  Each of the drive circuits 13 to 15 incorporates a switching element that operates in response to an input of a command signal. Then, when the switching element is activated or deactivated, power supply corresponding to each command value is performed from the in-vehicle power source to each device such as the injector 5.

[Operation of Example 1]
The operation of the fuel injection device 1 according to the first embodiment will be described.
The microcomputer 9 of the fuel injection device 1 determines the command value of the valve opening (throttle opening) of the throttle valve 7 according to the detected value of the engine speed, which is one of the injection state quantities, A drive current for achieving the command value is calculated as a throttle valve command value.

  Here, the injection state quantity is a variable corresponding to at least one of the combustion temperature of the fuel supplied by injection and the flow rate of the fuel supplied to the injection hole 31, and in addition to the engine speed, the accelerator opening and the exhaust gas Temperature etc. can be mentioned. That is, the microcomputer 9 functions as a throttle valve command value calculation unit that calculates a throttle valve command value according to the injection state quantity.

  Here, if the injector command values such as the energization start timing and the energization period are the same, the actual injection amount by the injector 5 is essentially the same amount. However, with the passage of time, the space between the sliding surface on the command piston 37 side and the sliding surface on the body body 38 side, and the space between the sliding surface on the injection valve 32 side and the sliding surface on the nozzle body 48 side are increased. As a result of sliding wear, the oil tightness of the back pressure control chamber 34 and the reservoir 47 is reduced.

  For this reason, when the oil tightness of the back pressure control chamber 34 is reduced, even when energization to the solenoid coil 56 is started based on the same value as the energization start timing, the closing biasing force and the opening biasing force are balanced. Becomes faster. For this reason, the injection start time, that is, the time when the injection rate starts to increase is also advanced (see FIG. 7). Further, even when the energization to the solenoid coil 56 is stopped based on the same value as the energization period, the timing at which the closing biasing force and the opening biasing force are balanced is delayed. As a result, the injection end timing, that is, the timing when the injection rate becomes zero is also delayed (see FIG. 7). As a result, even if a command value having the same magnitude is calculated as the energization start timing and the energization period, the actual injection amount increases.

  Further, when the oil tightness of the reservoir 47 is reduced, even when energization to the solenoid coil 56 is started based on the same value as the energization start timing, the timing at which the closing biasing force and the opening biasing force are balanced is delayed. The injection start timing is also delayed (see FIG. 8). Further, even when the energization to the solenoid coil 56 is stopped based on the same value as the energization period, the timing at which the closing biasing force and the opening biasing force are balanced is earlier and the injection end timing is also earlier (see FIG. 8). . As described above, even if a command value having the same magnitude is calculated as the energization start timing and the energization period, the actual injection amount is reduced.

  Therefore, the throttle valve command value calculation means calculates the throttle valve command value according to the increase / decrease of the engine speed (hereinafter referred to as the rotational speed) when injection is performed based on the same injector command value.

  For example, when the number of rotations is increasing despite injection being performed based on the same command value, the throttle valve command value calculation means determines that the actual injection amount is increasing and reduces the throttle opening A throttle valve command value is calculated so that the valve chamber pressure is increased. That is, when the valve chamber pressure is increased, the closing urging force becomes stronger. Therefore, as shown in FIGS. 4 (a) and 4 (b), the energization start timing is the same as the timing when the control valve 35 opens the back pressure control chamber 34. However, the time when the control valve 35 closes the back pressure control chamber 34 becomes early even if the energization period is the same. As a result, as shown in FIG. 4C, the decrease in the back pressure due to the start of energization is delayed, and the increase in the back pressure due to the stop of energization is accelerated. For this reason, as shown in FIG.4 (d), the injection start by an energization start becomes late, and the injection completion by an energization stop becomes early.

  If the number of revolutions is decreasing despite injection being performed based on the same command value, the throttle valve command value calculation means determines that the actual injection amount is decreasing and increases the throttle opening. The throttle valve command value is calculated so that the valve chamber pressure becomes small. That is, when the valve chamber pressure is reduced, the closing force is weakened. Therefore, as shown in FIGS. 5A and 5B, the energization start timing is the same as the timing when the control valve 35 opens the back pressure control chamber 34. However, the timing of closing the back pressure control chamber 34 by the control valve 35 is delayed even if the energization period is the same. Thereby, as shown in FIG.5 (c), the decrease start of the back pressure by an energization start becomes early, and the completion | finish of the increase of the back pressure by an energization stop is delayed. For this reason, as shown in FIG.5 (d), the injection start by energization start becomes early, and the injection completion by energization stop becomes late.

  As described above, the actual injection amount is adjusted according to the injector command value by adjusting the throttle opening and increasing / decreasing the valve chamber pressure when the actual injection amount increases or when the actual injection amount decreases. The injection amount according to the state can be controlled. The calculation of the throttle valve command value by the microcomputer 9 and the command based on the throttle valve command value can be performed as follows, for example.

  First, the microcomputer 9 calculates a throttle opening command value according to the degree of increase / decrease in the rotational speed, and according to the throttle opening command value, a drive current value corresponding to the throttle valve command value (that is, a solenoid) The energization amount to the coil 63 is calculated. Then, the microcomputer 9 calculates the duty ratio of the command signal to be output to the throttle valve drive circuit 15 based on the throttle valve command value.

  Then, the microcomputer 9 synthesizes a command signal based on this duty ratio and outputs it to the throttle valve drive circuit 15. As a result, the throttle valve drive circuit 15 energizes the solenoid coil 63 with a drive current corresponding to the throttle valve command value. As a result, the throttle opening substantially coincides with the command value, the valve chamber pressure is adjusted, and the actual injection amount is controlled to the injection amount corresponding to the injector command value, that is, the injection amount corresponding to the state of the engine.

[Effect of Example 1]
According to the fuel injection device 1 of the first embodiment, the return flow rate of the fuel returned from the back pressure control chamber 34 to the fuel tank 2 is throttled in the return passage on the downstream side of the fuel return pipe 6, that is, the control valve 35. .
As a result, the valve chamber pressure can be increased to increase the closing force, so that the opening time of the back pressure control chamber 34 by the control valve 35 is delayed and the closing time of the back pressure control chamber 34 by the control valve 35 is advanced. Can do. Therefore, it is possible to delay the start of the decrease in the back pressure accompanying the start of energization of the solenoid coil 56 and to accelerate the end of the increase in the back pressure accompanying the stop of the energization of the solenoid coil 56. As a result, even when the oil tightness of the back pressure control chamber 34 is reduced, it is possible to maintain the same timing when the closing biasing force and the opening biasing force are balanced at the start of energization. Similarly, the timing when the closing biasing force and the opening biasing force are balanced when the energization is stopped can be kept the same. As described above, even if the oil tightness of the back pressure control chamber 34 is reduced due to sliding wear, fluctuations in the actual injection amount can be suppressed.

Further, according to the fuel injection device 1, the throttle valve 7 that adjusts the return flow rate is disposed in the fuel return pipe 6.
For this reason, since the return flow rate can be adjusted by the throttle valve 7 and the valve chamber pressure can be increased or decreased, the closing force for the chamber can be operated freely. As a result, the return flow rate can be adjusted not only according to the oil tightness of the back pressure control chamber 34 but also according to the oil tightness of the reservoir 47, and fluctuations in the actual injection amount can be suppressed.

[Modification]
The fuel injection device 1 of the present embodiment selects the rotational speed as the injection state quantity and adjusts the throttle opening according to the rotational speed, but selects the accelerator opening and the exhaust temperature as the injection state quantity, and The throttle opening may be adjusted according to the opening and the exhaust temperature.

  That is, even if the injector command value is the same, the actual injection amount increases if the accelerator opening is small, and conversely if the accelerator opening is large, the actual injection amount decreases. Therefore, if the accelerator opening is small, the throttle valve command value calculating means calculates the throttle valve command value so as to reduce the throttle opening and increase the valve chamber pressure. On the contrary, if the accelerator opening is large, the throttle valve command value calculation means calculates the throttle valve command value so as to increase the throttle opening and decrease the valve chamber pressure.

  Even if the injector command value is the same, the actual injection amount increases if the exhaust temperature increases, and conversely if the exhaust temperature decreases, the actual injection amount decreases. For this reason, if the exhaust temperature is high, the throttle valve command value calculation means calculates the throttle valve command value so as to reduce the throttle opening and increase the valve chamber pressure. On the other hand, if the exhaust temperature is low, the throttle valve command value calculation means calculates the throttle valve command value so as to increase the throttle opening and decrease the valve chamber pressure.

  As described above, even if the accelerator opening degree or the exhaust gas temperature is adopted as the injection state quantity, fluctuations in the actual injection quantity with respect to the same command value can be suppressed.

  The fuel injection device 1 of the present embodiment employs a form in which the throttle valve 7 is disposed in the fuel return pipe 6 that is the return flow path downstream of the control valve 35, but the return valve upstream of the control valve 35 is used. You may employ | adopt the form which arrange | positions the throttle valve 7 in a flow path. In this case, the return flow rate may be adjusted by changing the opening degree of the out orifice 59 to the out orifice 59 as the throttle valve 7.

  According to the fuel injection device 1 of the present embodiment, the fuel leaking from the injector 5 is returned to the fuel tank 2 via the fuel return pipe 6, but the low-pressure fuel before being pressurized by the fuel supply pump 3. In other words, the fuel flow path from the fuel tank 2 to the intake metering valve 17 may be returned.

  The fuel injection device 1 of the present embodiment employs a structure that applies a back pressure to the injection valve 32 via the command piston 37, but the back of the fuel injection device 1 directly to the injection valve 32 without using the command piston 37. Even if a structure that exerts pressure is adopted, the same effect as in the present embodiment can be obtained.

  The fuel injection device 1 of this embodiment supplies fuel to a direct injection type engine such as a diesel engine. However, even if the fuel injection device 1 injects and supplies fuel to an intake pipe of a gasoline engine or the like, this embodiment The same effect can be obtained.

It is a whole lineblock diagram of a fuel injection device (example). It is a block diagram of an injector (Example). (A) is a block diagram of a throttle valve, (b) is explanatory drawing which shows the open state of the fuel return piping by a throttle valve (Example). (A) is a time chart which shows the energization state to the solenoid coil of an injector, (b) is a time chart which shows the movement state of the control valve before and behind valve chamber pressure increase, (c) is before and after valve chamber pressure increase. FIG. 4D is a time chart showing the change over time in the back pressure, and FIG. 6D is a time chart showing the change over time in the injection rate before and after the increase in the valve chamber pressure (Example). (A) is a time chart which shows the energization state to the solenoid coil of an injector, (b) is a time chart which shows the movement state of the control valve before and behind valve chamber pressure reduction, (c) is before and after valve chamber pressure reduction. FIG. 6D is a time chart showing the change over time in the back pressure, and FIG. 6D is a time chart showing the change over time in the injection rate before and after the valve chamber pressure is decreased (Example). It is a block diagram of an injector (conventional example). (A) is a time chart which shows the energization state to the solenoid coil of an injector, (b) is a time chart which shows the condition of the actual injection amount increase by the time-dependent change of an injection rate (conventional example). (A) is a time chart which shows the energization state to the solenoid coil of an injector, (b) is a time chart which shows the condition of the actual injection amount reduction | decrease by the time-dependent change of an injection rate (conventional example).

Explanation of symbols

1 Fuel injector 2 Fuel tank (low pressure side)
3 Fuel supply pump 4 Common rail 5 Injector 7 Throttle valve 31 Injection hole 32 Injection valve 34 Back pressure control chamber 35 Control valve

Claims (8)

An injection valve that opens and closes the injection hole, and a control valve that opens and closes a return passage that communicates the low pressure side with the back pressure control chamber formed on the counter injection hole side of the injection valve,
The fuel is injected and supplied through the nozzle hole by the opening operation of the injection valve, and the fuel in the back pressure control chamber is returned to the low pressure side by the opening operation of the control valve.
A fuel injection device, characterized in that a return flow rate of fuel returned by an opening operation of the control valve is throttled in a return flow path downstream of the control valve. The fuel injection device according to claim 1,
A fuel injection device, wherein a throttle valve that varies an opening degree is disposed in the downstream return flow path, and the return flow rate is adjusted by varying an opening degree of the throttle valve. An injection valve that opens and closes the injection hole, a control valve that opens and closes a return flow path that communicates the back pressure control chamber formed on the counter injection hole side of the injection valve and the low pressure side, and a return upstream of the control valve Provided with a throttle valve that is arranged in the flow path and varies the opening degree,
The fuel is injected and supplied through the nozzle hole by the opening operation of the injection valve, and the fuel in the back pressure control chamber is returned to the low pressure side by the opening operation of the control valve.
A fuel injection device, wherein a return flow rate of fuel returned by an opening operation of the control valve is adjusted by varying an opening degree of the throttle valve. The fuel injection device according to claim 2 or 3,
The fuel injection device, wherein the return flow rate is adjusted in accordance with an injection state quantity corresponding to at least one of a combustion temperature of fuel supplied by injection and a flow rate of fuel supplied to the nozzle hole. The fuel injection device according to claim 4, wherein
The fuel injection device characterized in that the injection state quantity is an engine speed. The fuel injection device according to claim 4, wherein
The fuel injection device characterized in that the injection state quantity is an accelerator opening. The fuel injection device according to claim 4, wherein
The fuel injection device characterized in that the injection state quantity is an exhaust temperature. The fuel injection device according to any one of claims 1 to 3,
A fuel supply pump that sucks fuel from the fuel tank and pressurizes and discharges the fuel, a common rail that accumulates fuel discharged from the fuel supply pump, the injection valve, and the control valve, and is distributed from the common rail A fuel injection device comprising an injector for injecting and supplying fuel.

Images