JP2009013841A - Back pressure regulating valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid fluctuation of a valve opening pressure Pb of a back pressure regulating valve 1 for inhibiting evaporation of a liquefied gas fuel in a back pressure chamber of an injector in a fuel injection device for supplying injection to an internal combustion engine by introducing the liquefied gas fuel to the injector. <P>SOLUTION: The back pressure regulating valve 1 is equipped with a first spring 38 for biasing a valve element 31 in the valve opening direction, and a piston 37 for supporting an end out of both ends of the first spring 38 opposite to the end supported by the valve element 31. Further, biasing force of the first spring 38 is made variable by the inner pressure Pt of the tank 5 and the atmospheric pressure acting in the reverse direction from each other on a large diameter sliding part 35 of the piston 37, and the piston 37 being displaced in response to the inner pressure Pt of the tank 5. Therefore, the valve opening pressure Pb of the back pressure regulating valve 1 can be prevented from fluctuating because even when the inner pressure Pt of the tank 5 fluctuates, resultant force of the biasing force acting on the valve element 31 in the valve closing direction can be kept constant. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a back pressure regulating valve that regulates back pressure acting on a valve body of an injector (hereinafter, the valve body of the injector is referred to as an injection valve body).

  Conventionally, an injector that injects and supplies fuel to an internal combustion engine has been provided with an injection valve body that opens and closes an injection hole, and by operating a fuel pressure acting on the injection valve body, the injection hole is opened and closed to start fuel injection. To stop or stop.

  That is, the injector includes a nozzle chamber that forms a fuel pressure that biases the injection valve body in the valve opening direction, and a back pressure chamber that forms a fuel pressure (back pressure) that biases the injection valve body in the valve closing direction. Is provided. The injection valve body is displaced in the valve opening direction or the valve closing direction to open and close the nozzle hole by operating the flow of fuel into and out of the back pressure chamber to increase or decrease the back pressure. Further, the fuel that has flowed out of the back pressure chamber is returned to the tank that stores the fuel, and is supplied to the injector again.

  In recent years, liquefied gaseous fuel has attracted attention as a fuel that is introduced into an injector and injected and supplied to an internal combustion engine because of increased interest in environmental problems. This liquefied gaseous fuel is a gaseous fuel that can be liquefied at room temperature by compression, and for example, dimethyl ether (DME), liquefied petroleum gas (LPG), liquefied natural gas (LNG) and the like are known.

  By the way, the liquefied gaseous fuel cannot exist as a liquid unless it is under a high pressure such as several MPa, and easily vaporizes due to a pressure drop. When the liquefied gaseous fuel in the back pressure chamber that forms the back pressure is vaporized, the opening and closing operation of the injection hole by the injection valve body becomes unstable, and the variation in the injection amount by the injector becomes large.

  Therefore, in order to prevent the liquefied gaseous fuel in the back pressure chamber from vaporizing while maintaining the back pressure at a high pressure, a back pressure regulating valve with a simple check valve structure is provided in the return flow path connecting the back pressure chamber and the tank. Therefore, a technique for preventing the back pressure from decreasing below a predetermined regulation value has been studied. This back pressure regulating valve is composed of, for example, a valve body that opens and closes a return flow path and a spring as a biasing member that biases this valve body in the valve closing direction, and ideally only a set load of the spring is set. Accordingly, the regulation value of the back pressure, that is, the valve opening pressure is determined.

  However, according to this back pressure regulating valve, in addition to the biasing force of the spring (that is, the biasing force of the biasing member), the biasing force (hereinafter referred to as the downstream pressure) by the fuel pressure downstream of the valve body (hereinafter referred to as the downstream pressure) Hereinafter, “the urging force by the downstream pressure” is referred to as the downstream pressure urging force) acts on the valve body in the valve closing direction. This downstream pressure substantially matches the internal pressure of the tank through the return flow path downstream of the valve body.

  Here, the internal pressure of the tank substantially coincides with the saturated vapor pressure of the liquefied gaseous fuel, but the change rate of the saturated vapor pressure of the liquefied gaseous fuel with the temperature change is large. For this reason, the internal pressure of the tank greatly varies with temperature change, and as a result, the downstream pressure also varies significantly with temperature change. Therefore, the urging force acting on the valve body in the valve closing direction (mainly, the resultant force of the urging force of the urging member and the downstream pressure urging force: hereinafter referred to as the valve closing resultant force) varies greatly depending on the temperature. The valve opening pressure of the back pressure regulating valve also varies depending on the temperature.

Patent Document 1 discloses a pressure regulating valve that regulates the return fuel pressure from the fuel injection pump. Even in this pressure regulating valve, the downstream pressure acts in the valve closing direction. For this reason, when using liquefied gaseous fuel as a fuel, a valve opening pressure will fluctuate similarly to the above.
JP 2003-65186 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection device that introduces liquefied gaseous fuel into an injector and injects it into an internal combustion engine, and liquefies it in a back pressure chamber of the injector. The object is to avoid fluctuations in the valve opening pressure of the back pressure regulating valve that prevents vaporization of the gaseous fuel.

[Means of Claim 1]
The back pressure regulating valve according to claim 1 is arranged in a return flow path for returning the liquefied gaseous fuel flowing out from the back pressure chamber of the injector to the tank, and urges the injector valve body in the valve closing direction. It regulates back pressure. The back pressure regulating valve includes a valve body that opens and closes the return flow path, and an urging member that urges the valve body in a valve closing direction, and the urging force of the urging member that acts on the valve body is It varies according to the internal pressure (internal pressure) or internal temperature.
Thereby, the fluctuation | variation of the downstream pressure urging | biasing force accompanying the fluctuation | variation of the internal pressure of a tank can be offset by the change of the urging | biasing force of an urging | biasing member. For this reason, even if the internal pressure of the tank fluctuates, the valve closing force can be kept constant, so that the valve opening pressure of the back pressure regulating valve can be prevented from fluctuating.

[Means of claim 2]
According to a second aspect of the present invention, the back pressure regulating valve includes a seat member that supports an end of the biasing member opposite to the end supported by the valve body. Then, the internal pressure and atmospheric pressure of the tank act on the seat member in opposite directions, and the urging force of the urging member is varied by displacing the seat member according to the difference between the internal pressure of the tank and the atmospheric pressure.
This means shows one form in which the urging force of the urging member is varied according to the internal pressure of the tank. According to this means, the internal pressure and atmospheric pressure of the tank are applied to the seat member in opposite directions, and the seat member is displaced according to the internal pressure of the tank, so that the biasing member supported at one end by the seat member is expanded and contracted. Thus, the urging force of the urging member is varied.

[Means of claim 3]
The back pressure regulating valve according to claim 3 supports a thermistor that expands and contracts according to its own temperature, and an end opposite to the end supported by the valve body in both ends of the urging member, And a seat member that is displaced by expansion and contraction of the thermistor. The temperature of the thermistor changes according to the internal temperature of the tank, and the urging force of the urging member is varied by the displacement of the seat member according to the temperature of the thermistor.
This means also shows one form in which the urging force of the urging member is varied according to the internal pressure of the tank. According to this means, the temperature of the thermistor is changed according to the internal temperature of the tank, which fluctuates with the internal pressure of the tank, and the seat member is displaced according to the expansion and contraction of the thermistor, so that the bias is supported at one end by the seat member The urging force of the urging member is varied by expanding and contracting the member.

[Means of claim 4]
The back pressure regulating valve according to claim 4 supports a solenoid coil that generates a magnetic attractive force when energized and an end opposite to the end supported by the valve body at both ends of the urging member. And a seat member that is displaced by the magnetic attraction force of the solenoid coil. The energization amount to the solenoid coil is varied according to the internal pressure or the internal temperature of the tank, and the urging force of the urging member is varied by displacing the seat member according to the energization amount to the solenoid coil.
This means also shows one form in which the urging force of the urging member is varied according to the internal pressure of the tank. According to this means, the energizing amount to the solenoid coil is varied according to the internal pressure or the internal temperature of the tank, and one end is supported by the seat member by displacing the seat member according to the magnetic attractive force of the solenoid coil. The biasing force of the biasing member is varied by expanding and contracting the biasing member.

  The back pressure regulating valve of the best mode 1 is arranged in a return flow path for returning the liquefied gaseous fuel flowing out from the back pressure chamber of the injector to the tank, and biases the injector valve body of the injector in the valve closing direction. It regulates the pressure. The back pressure regulating valve includes a valve body that opens and closes the return flow path, and an urging member that urges the valve body in a valve closing direction, and the urging force of the urging member that acts on the valve body is It varies according to the internal pressure or internal temperature of the.

  The back pressure regulating valve includes a seat member that supports an end portion opposite to an end portion supported by the valve body in both ends of the urging member. Then, the internal pressure and atmospheric pressure of the tank act on the seat member in opposite directions, and the urging force of the urging member is varied by displacing the seat member according to the difference between the internal pressure of the tank and the atmospheric pressure.

  The back pressure regulating valve of the best mode 2 supports a thermistor that expands and contracts according to its own temperature, and an end opposite to the end supported by the valve body in both ends of the urging member. And a seat member that is displaced by expansion and contraction. The temperature of the thermistor changes according to the internal temperature of the tank, and the urging force of the urging member is varied by the displacement of the seat member according to the temperature of the thermistor.

  The back pressure regulating valve of the best mode 3 supports a solenoid coil that generates a magnetic attractive force by energization, and an end opposite to the end supported by the valve body in both ends of the urging member, And a seat member that is displaced by the magnetic attractive force of the solenoid coil. The energization amount to the solenoid coil is varied according to the internal pressure or the internal temperature of the tank, and the urging force of the urging member is varied by displacing the seat member according to the energization amount to the solenoid coil.

[Configuration of Example 1]
A configuration of the back pressure regulating valve 1 according to the first embodiment will be described with reference to the drawings.
First, a fuel injection device 3 that includes a back pressure regulating valve 1 and an injector 2 whose back pressure is regulated by the back pressure regulating valve 1 and that injects fuel to an internal combustion engine (not shown) will be described. The fuel injection device 3 supplies dimethyl ether (DME), which is a liquefied gaseous fuel, to the internal combustion engine.

  As shown in FIG. 1, the fuel injection device 3 has a tank 5 that stores DME, a feed pump 6 that sucks and discharges DME from the tank 5, and discharges the DME discharged from the feed pump 6 at a high pressure. Operation of the high pressure pump 7, the common rail 8 that accumulates the DME discharged from the high pressure pump 7 in a high pressure state and distributes it to the plurality of injectors 2, the injector 2 that injects the DME distributed from the common rail 8, and the operation of the injector 2, etc. And an electronic control unit (ECU) 9 for controlling the motor. The back pressure regulating valve 1 is disposed in a return flow path 10 for returning DME from the injector 2 to the tank 5.

  The tank 5 is provided with high pressure resistance so that it can withstand the saturated vapor pressure of DME which reaches a high pressure of about 3 MPa at about 90 ° C. A gas-liquid two-phase equilibrium state of DME is formed inside the tank 5, and the internal pressure (internal pressure) Pt of the tank 5 substantially matches the saturated vapor pressure corresponding to the internal temperature.

  The feed pump 6, the high pressure pump 7, the common rail 8, and the injector 2 are also provided so that the DME can flow at a pressure of 3 MPa or more so that the DME does not vaporize even at a high temperature close to 90 ° C. The common rail 8 is equipped with a rail pressure sensor 13 for detecting the pressure of accumulated DME (rail pressure) and outputting it to the ECU 9, a pressure reducing valve 14 for quickly reducing the rail pressure, and the like.

  The ECU 9 is configured as a well-known computer having a storage device such as a CPU, a ROM and a RAM having a control function and an arithmetic function, an input device, and an output device, and detection signals obtained from various sensors such as the rail pressure sensor 13. Based on the above, the operation of the injector 2 and the like is controlled.

  As shown in FIG. 2, the injector 2 includes an injection valve body 17 that opens and closes the injection hole 16 and a spring 18 that biases the injection valve body 17 in the valve closing direction, and acts on the injection valve body 17. Is operated to open and close the nozzle hole 16 to start or stop the DME injection.

  That is, the injector 2 forms a hydraulic pressure that urges the injection valve body 17 in the valve opening direction and is opened and closed between the nozzle hole 16 by the tip of the injection valve body 17, and the injection valve A back pressure chamber 21 for forming a hydraulic pressure (back pressure) for urging the body 17 in the valve closing direction is provided. The injection valve body 17 is displaced in the valve opening direction or the valve closing direction to open and close the nozzle hole 16 by operating the flow of DME into and out of the back pressure chamber 21 to increase or decrease the back pressure.

  Here, the inlet of the back pressure chamber 21 is provided so that DME flows from the common rail 8 via the inlet orifice 22, and the outlet of the back pressure chamber 21 is returned via the outlet orifice 23. 10, DME flows out and is opened and closed by a solenoid valve 24. Further, the inlet and outlet orifices 22 and 23 are configured such that the flow rate of DME passing through the outlet orifice 23 is larger than the flow rate of DME passing through the inlet orifice 22 when the outlet is open. Is provided.

Further, the solenoid valve 24 is energized by a command from the ECU 9 to generate a magnetic attraction force and a solenoid coil 27 that is driven by the magnetic attraction force to open the outlet of the back pressure chamber 21 with a valve function. And a spring 29 that biases the armature 28 toward the valve closing side (that is, the direction in which the outflow port of the back pressure chamber 21 is closed).
The nozzle chamber 20 is provided so that DME flows from the common rail 8 without being restricted by an orifice or the like.

  As described above, when the solenoid coil 27 is energized, DME flows out from the back pressure chamber 21 and the back pressure is lowered. Therefore, the energizing force in the valve closing direction acting on the injection valve body 17 (the energizing force due to the back pressure) The resultant force with the urging force of the spring 18 is smaller than the urging force in the valve opening direction acting on the injection valve body 17 (the urging force due to the hydraulic pressure of the nozzle chamber 20). As a result, the injection valve body 17 is displaced in the valve opening direction to open the injection hole 16.

  When the energization of the solenoid coil 27 is stopped, the outflow of DME from the back pressure chamber 21 stops and the back pressure rises, so that the urging force in the valve closing direction acting on the injection valve body 17 is increased in the valve opening direction. It becomes larger than the urging force. As a result, the injection valve body 17 is displaced in the valve closing direction to close the injection hole 16.

  As shown in FIG. 3, the back pressure regulating valve 1 has a ball-like valve body 31 and two sliding portions 35 that are different in size and coaxial and have sliding contact with the valve body 34 via seal rings 32 and 33. , 36, a first spring 38 interposed between the valve body 31 and the piston 37, and a second spring 39 interposed between the piston 37 and the valve body 34.

  Here, the valve body 34 is provided with a cylinder 43 that houses the valve body 31, the first spring 38, the piston 37, and the second spring 39. In the cylinder 43, the valve body 31, the first spring 38, the piston 37, and the second spring 39 are accommodated in series from the left side to the right side in the drawing, and the displacement direction of the valve body 31 and the piston 37, In addition, the expansion and contraction directions of the first and second springs 38 and 39 are substantially the same.

  The cylinder 43 includes a large diameter portion 44 and a small diameter portion 45 that are large and different in diameter and coaxial. The large diameter portion 44 includes a valve body 31, a first spring 38, and a large diameter sliding portion (hereinafter referred to as a large diameter). 35) is housed, and the second spring 39 is housed in the small diameter portion 45. The small-diameter sliding portion (hereinafter referred to as a small-diameter sliding portion) 36 is accommodated across the large-diameter portion 44 and the small-diameter portion 45.

  A part of the return flow path 10 is formed in a space (referred to as a first spring chamber 47) that is partitioned by the large-diameter sliding portion 35 inside the large-diameter portion 44 and accommodates the valve body 31 and the first spring 38. Two openings 48 and 49 are connected. The valve body 31 is disposed in the opening 48 on the upstream side and is biased by the first spring 38 in a direction to close the opening 48.

  Further, the DME of the tank 5 is introduced into the first spring chamber 47 from the downstream opening 49, and the hydraulic pressure in the first spring chamber 47 substantially matches the internal pressure Pt of the tank 5. The hydraulic pressure in the first spring chamber 47 urges the valve body 31 in the left direction in the figure (that is, the valve closing direction) and urges the piston 37 in the right direction in the figure. That is, the hydraulic pressure in the first spring chamber 47 that substantially matches the internal pressure Pt of the tank 5 forms a hydraulic pressure (downstream pressure) that urges the valve body 31 from the downstream side. The urging force (downstream pressure urging force) against the valve body 31 due to the hydraulic pressure in the first spring chamber 47 forms a valve closing force together with the urging force (first spring force) due to the first spring 38.

A space on the right side of the figure defined by the large-diameter sliding portion 35 inside the large-diameter portion 44 forms an atmospheric chamber 50 that is open to the atmosphere and exhibits a pressure that substantially matches the atmospheric pressure. The large-diameter sliding portion 35 is urged in the left direction in the figure by the atmospheric pressure guided to the atmospheric chamber 50.
Further, in the space (referred to as the second spring chamber 51) that is sealed by the small-diameter sliding portion 36 inside the small-diameter portion 45 and accommodates the second spring 39, there is one opening portion for introducing DME from the tank 5. 52 is connected. As a result, the hydraulic pressure in the second spring chamber 51 substantially matches the internal pressure Pt of the tank 5, and the hydraulic pressure in the second spring chamber 51 urges the piston 37 in the left direction in the figure.

  Thus, the return flow path 10 is opened and closed by the valve body 31, and the valve body 31 is urged in the valve closing direction by the first spring 38 (that is, the first spring 38 applies the valve body 31 in the valve closing direction). Functions as a biasing member). Further, the piston 37 functions as a seat member that supports the end opposite to the end supported by the valve body 31 in both ends of the first spring 38, and the large-diameter sliding portion 35 of the piston 37 includes The internal pressure Pt and the atmospheric pressure in the tank 5 act in opposite directions.

  The first spring force is varied by the displacement of the piston 37 according to the difference between the internal pressure Pt of the tank 5 and the atmospheric pressure, that is, according to the internal pressure Pt of the tank 5. Since the internal pressure Pt of the tank 5 substantially matches the saturated vapor pressure corresponding to the internal temperature of the tank 5, the first spring force varies depending on the internal temperature of the tank 5.

  According to the back pressure regulating valve 1, as shown in the following calculation, the valve opening pressure Pb of the valve body 31 is set regardless of the value of the downstream pressure (that is, regardless of the value of the internal pressure Pt of the tank 5). Can be a constant value.

[Valve opening pressure calculation of Example 1]
The valve opening pressure Pb of the back pressure regulating valve 1 of the first embodiment is calculated using various parameters.
The parameters used for this calculation are the seat area A of the valve body 31, the pressure receiving area A 1 in the large-diameter sliding portion 35 of the hydraulic pressure of the first spring chamber 47, and the small-diameter sliding portion 36 of the hydraulic pressure in the second spring chamber 51. Pressure receiving area A2, spring constant K1 of first spring 38, spring constant K2 of second spring 39, initial compression amount X1 of first spring 38, initial compression amount X2 of second spring 39, internal pressure Pt of tank 5, etc. (Note that the initial compression amounts X1 and X2 are compression amounts of the first and second springs 38 and 39 when the hydraulic pressures of the first and second spring chambers 47 and 51 substantially match the atmospheric pressure, The internal pressure Pt is a relative pressure with respect to the atmospheric pressure).

A large-diameter slide is assumed when the hydraulic pressure in the first and second spring chambers 47 and 51 is substantially equal to the atmospheric pressure, assuming the X axis in the horizontal direction in the figure and the right direction in the figure as the positive direction of X. The position of the right end of the part 35 is defined as X = 0.
First, when the hydraulic pressures of the first and second spring chambers 47 and 51 substantially coincide with the atmospheric pressure, the piston 37 is acted on by a first spring force having a strength of K1 · X1 in the positive direction and K2 in the negative direction. The urging force (second spring force) by the second spring 39 having the strength of X2 acts and stops. For this reason, the following numerical formula 1 is established from the balance of the force related to the piston 37.
[Formula 1]
K1 / X1 = K2 / X2

  Next, consider the case where the internal pressure Pt of the tank 5 is introduced into the first and second spring chambers 47 and 51 and the piston 37 is displaced by X in the positive direction and is stationary. In this case, the hydraulic pressures in the first and second spring chambers 47 and 51 substantially coincide with the internal pressure Pt, and the first spring force having a strength of K1 (X1-X) acts on the piston 37 in the positive direction. , A biasing force due to the hydraulic pressure of the first spring chamber 47 having a strength of Pt · A1 is applied. Further, a second spring force having a strength of K2 (X2 + X) acts in the negative direction on the piston 37, and a biasing force due to the hydraulic pressure of the second spring chamber 51 having a strength of Pt · A2 acts on the piston 37.

For this reason, the following mathematical formula 2 is established from the balance of the force related to the piston 37.
[Formula 2]
K1 (X1-X) + Pt.A1 = K2 (X2 + X) + Pt.A2
Then, when Equation 2 is solved for X, the following Equation 3 is obtained.
[Formula 3]
X = {Pt (A1-A2) + (K1 * X1-K2 * X2)} / (K1 + K2)
Furthermore, if Formula 1 is applied to Formula 3, the following Formula 4 is obtained.
[Formula 4]
X = Pt (A1-A2) / (K1 + K2)

  Further, the first spring force having the strength of K1 (X1-X) acts in the negative direction on the valve body 31 and the downstream pressure urging force having the strength of Pt · A acts on the valve body 31. A force equivalent to (valve closing force) is applied in the positive direction by the hydraulic pressure of the valve body 34 and the opening 48 (which substantially matches the back pressure of the injector 2).

Therefore, when the hydraulic pressure in the opening 48 increases and the valve body 31 is detached from the valve body 34, the hydraulic pressure in the opening 48 (that is, the back pressure of the injector 2) substantially matches the valve opening pressure Pb. The following formula 5 is established from the balance of force related to the valve body 31.
[Formula 5]
Pb · A = K1 (X1−X) + Pt · A
Then, when Equation 5 is solved for the valve opening pressure Pb, the following Equation 6 is obtained.
[Formula 6]
Pb = K1 (X1-X) / A + Pt

Further, when Expression 4 is applied to X of Expression 6, and divided into a term including the internal pressure Pt and a term not including the internal pressure Pt, the following Expression 7 is obtained.
[Formula 7]
Pb = K1 * X1 / A + Pt {1-K1 (A1-A2) / (K1 + K2) / A}

Therefore, if each parameter is set so that the coefficient part other than the internal pressure Pt in the term including the internal pressure Pt in Formula 7 is zero, that is, the following Formula 8 is satisfied, the valve opening pressure Pb is The constant value K1 · X1 / A.
[Formula 8]
A (K1 + K2) = K1 (A1-A2)

  That is, if the seat area A, the pressure receiving areas A1 and A2, and the spring constants K1 and K2 are set so as to satisfy Formula 8, the valve opening pressure Pb is set to a constant value K1 · X1 / regardless of the internal pressure Pt of the tank 5. A can be set.

According to the back pressure regulating valve 1 of the first embodiment, since the pressure receiving area A1 is larger than the seat area A, the responsiveness of the valve opening pressure Pb to the fluctuation of the internal pressure Pt of the tank 5 is high. That is, even if the internal pressure Pt of the tank 5 fluctuates, the valve opening pressure Pb quickly converges to a constant value K1 · X1 / A.
Further, by introducing the internal pressure Pt of the tank 5 into the second spring chamber 51, the pressure receiving area of the atmospheric pressure of the piston 37 in the atmospheric chamber 50 becomes equal to the difference between the pressure receiving area A1 and the pressure receiving area A2.

[Effect of Example 1]
The back pressure regulating valve 1 according to the first embodiment includes a valve body 31 that opens and closes the return flow path 10, a first spring 38 that biases the valve body 31 in the valve closing direction, and a valve that is located at both ends of the first spring 38. The piston 37 which supports the edge part opposite to the edge part supported by the body 31 is provided. The internal pressure Pt and atmospheric pressure of the tank 5 act in opposite directions on the large-diameter sliding portion 35 of the piston 37, and the piston 37 is displaced according to the difference between the internal pressure Pt of the tank 5 and the atmospheric pressure. The first spring force is varied.
Thereby, the fluctuation | variation of the downstream pressure energizing force accompanying the fluctuation | variation of the internal pressure Pt of the tank 5 can be canceled by the change of the 1st spring force. For this reason, even if the internal pressure Pt fluctuates, the valve closing force can be kept constant, so that the valve opening pressure Pb of the back pressure regulating valve 1 can be avoided from fluctuating.

  According to the back pressure regulating valve 1 of the second embodiment, as shown in FIG. 4, the cylinder 43 is formed with a single diameter, and the piston 37 is also provided with a single diameter. The valve body 31 is provided in a spool shape and is slidably accommodated in the cylinder 43. An annular groove 55 is provided on the inner peripheral surface of the cylinder 43, and a downstream opening 49 is connected to the annular groove 55. The upstream opening 48 communicates with the annular groove 55 and the downstream opening 49 due to the displacement of the valve body 31 in the valve opening direction.

  The cylinder 43 is divided into a first spring chamber 47 and a second spring chamber 51 by a piston 37, and the first spring chamber 47 is connected to the return flow path 10 by an opening 57, and the second spring chamber 51 is Open to the atmosphere. Thereby, the hydraulic pressure (downstream pressure) of the first spring chamber 47 substantially matches the internal pressure Pt of the tank 5, and the pressure of the second spring chamber 51 substantially matches the atmospheric pressure (that is, the second spring chamber 51 is It has the function of the atmospheric chamber 50).

  As described above, the return flow path 10 is opened and closed by the valve body 31, and the valve body 31 is urged in the valve closing direction by the first spring 38. Further, the piston 37 functions as a seat member that supports the end opposite to the end supported by the valve body 31 in both ends of the first spring 38, and the piston 37 includes an internal pressure Pt and a tank 5. Atmospheric pressure acts in opposite directions. The first spring force is varied by the displacement of the piston 37 according to the difference between the internal pressure Pt of the tank 5 and the atmospheric pressure, that is, according to the internal pressure Pt of the tank 5.

Further, according to the back pressure regulating valve 1 of the second embodiment, since the atmospheric pressure is introduced into the second spring chamber 51, the valve opening pressure Pb can be determined by regarding the pressure receiving area A2 as substantially zero in Expression 8. A conditional expression that can be set to a constant value K1 · X1 / A can be obtained as in Expression 9 below.
[Formula 9]
A (K1 + K2) = K1 · A1

  That is, if the seat area A, the pressure receiving area A1, and the spring constants K1 and K2 are set so as to satisfy Formula 9, the valve opening pressure Pb of the back pressure regulating valve 1 varies regardless of the internal pressure Pt of the tank 5. Can be avoided.

  According to the back pressure regulating valve 1 of the second embodiment, the second spring chamber 51 functions as the atmospheric chamber 50, and the pressure receiving area of the atmospheric pressure of the piston 37 in the second spring chamber 51 substantially matches the pressure receiving area A1. .

  As shown in FIG. 5, the back pressure regulating valve 1 according to the third embodiment includes a thermistor 59 that expands and contracts according to its own temperature, and an end portion that is supported by the valve body 31 within both ends of the first spring 38. And a seat member 60 that supports the opposite end and is displaced by expansion and contraction of the thermistor 59. In the cylinder 43, the valve body 31, the first spring 38, the seat member 60, and the second spring 39 are accommodated in series sequentially from the left side to the right side in the figure, and the thermistor 59 is accommodated in parallel with the first spring 38. The displacement directions of the valve body 31 and the seat member 60 and the expansion / contraction directions of the thermistor 59 and the first and second springs 38 and 39 are all substantially the same.

  The second spring force is set to be sufficiently larger than the first spring force, and the seat member 60 and the thermistor 59 are always kept in contact with each other by the strong second spring force. For this reason, when the thermistor 59 expands and contracts according to its own temperature, the seat member 60 is displaced and the first spring force is varied.

  Further, the internal pressure Pt of the tank 5 is introduced into the cylinder 43 through the opening 49. The internal temperature of the cylinder 43 (that is, the liquid temperature of DME filled in the cylinder 43) changes according to the internal pressure Pt of the tank 5, that is, the saturated vapor pressure of DME. The temperature changes according to the internal temperature of the tank 5. That is, the temperature of the thermistor 59 changes according to the internal temperature of the tank 5 and the internal pressure Pt of the tank 5.

As described above, the back pressure regulating valve 1 according to the third embodiment changes the temperature of the thermistor 59 according to the internal temperature of the tank 5 and displaces the seat member 60 according to the expansion and contraction of the thermistor 59 accompanying this temperature change. The first spring force is varied by extending and contracting the first spring 38.
Since the back pressure regulating valve 1 of the third embodiment needs to maintain a high correlation between the internal temperature of the tank 5 and the temperature of the thermistor 59, the distance between the back pressure regulating valve 1 and the tank 5 can be as long as possible. It is preferable to make it small. For this reason, for example, the back pressure regulating valve 1 may be provided inside the tank 5 so that the internal temperature of the tank 5 and the temperature of the thermistor 59 substantially coincide.

  As shown in FIG. 6, the back pressure regulating valve 1 of the fourth embodiment includes a solenoid coil 62 that generates a magnetic attractive force when energized, and an end portion that is supported by the valve body 31 within both ends of the first spring 38. Is provided with an armature 63 that supports the opposite end and functions as a seat member and is displaced by the magnetic attractive force of the solenoid coil 62. In the cylinder 43, the valve body 31, the first spring 38, the armature 63, and the second spring 39 are accommodated in order from the left side to the right side in the figure, and the displacement direction of the valve body 31 and the armature 63, In addition, the expansion and contraction directions of the first and second springs 38 and 39 are substantially the same.

  The energization amount to the solenoid coil 62 is varied by the ECU 9 according to the output from the pressure sensor 64 that detects the internal pressure Pt of the tank 5. That is, the ECU 9 operates the resistance value of the variable resistor 65 in accordance with the output from the pressure sensor 64 in the electric circuit including the solenoid coil 62, the variable resistor 65, and the power source 66, thereby energizing the solenoid coil 62. Is variable. And since the magnetic attraction force which acts on the armature 63 changes by changing the energization amount to the solenoid coil 62, the armature 63 is displaced and the first spring force is changed.

  As described above, the back pressure regulating valve 1 of the fourth embodiment varies the energization amount to the solenoid coil 62 according to the internal pressure Pt of the tank 5, and the armature 63 according to the change of the magnetic attraction force accompanying the variation of the energization amount. Is displaced to expand and contract the first spring 38 to vary the first spring force.

  Note that, according to the back pressure regulating valve 1 of the fourth embodiment, the first spring force can be forcibly weakened by increasing the energization amount to the solenoid coil 62 and strengthening the magnetic attractive force. For this reason, for example, when the engine is stopped, the first spring force is forcibly weakened to displace the valve body 31 in the valve opening direction, and the DME in the return flow path 10 can be purged. That is, the back pressure regulating valve 1 can function as a purge valve.

[Modification]
According to the back pressure regulating valve 1 of the first, third, and fourth embodiments, the valve body 31 has a ball shape, and according to the back pressure regulating valve 1 of the second embodiment, the valve body 31 has a spool shape. The shape of 31 is not limited to these forms, and the valve body 31 of the first, third, and fourth embodiments may be a spool shape, and the valve body 31 of the second embodiment may be a ball shape.

Further, the ECU 9 of the fourth embodiment varies the energization amount to the solenoid coil 62 based on the output from the pressure sensor 64 that detects the internal pressure Pt of the tank 5, but the tank 5 is equipped with a temperature sensor that detects the internal temperature. The energization amount to the solenoid coil 62 may be varied according to the internal temperature of the tank 5.
In addition, the ECU 9 of the fourth embodiment changes the energization amount to the solenoid coil 62 by operating the resistance value of the variable resistor 65. The control signal output from the ECU 9 is used as an on / off signal, and the duty ratio of the on / off signal is set. The amount of energization to the solenoid coil 62 may be varied by operating.

  Further, according to the back pressure regulating valve 1 of the first to fourth embodiments, the biasing member that biases the valve body 31 in the valve closing direction is provided in a coil shape and exerts a biasing force in the axial direction. However, the present invention is not limited to such a form. For example, a member provided in a plate shape such as a leaf spring and exhibiting elasticity may be employed as a biasing member, or provided in a bellows shape and compressed. You may employ | adopt the member which can accumulate reaction force as an urging | biasing member.

1 is an overall view of a fuel injection device (Example 1). (Example 1) which is explanatory drawing of an injector. (Example 1) which is explanatory drawing of a back pressure control valve. (Example 2) which is explanatory drawing of a back pressure control valve. (Example 3) which is explanatory drawing of a back pressure control valve. (Example 4) which is explanatory drawing of a back pressure control valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Back pressure control valve 2 Injector 5 Tank 10 Return flow path 17 Injection valve body 21 Back pressure chamber 31 Valve body 37 Piston (seat member)
38 First spring (biasing member)
59 Thermistor 60 Seat member 62 Solenoid coil 63 Armature (seat member)
Pt internal pressure (internal tank pressure)

Claims (4)

In the back pressure regulating valve which is arranged in a return flow path for returning the liquefied gaseous fuel flowing out from the back pressure chamber of the injector to the tank and regulates the back pressure for urging the injector valve body in the valve closing direction,
A valve body that opens and closes the return flow path, and a biasing member that biases the valve body in a valve closing direction,
A back pressure regulating valve characterized in that an urging force of the urging member acting on the valve body is varied in accordance with an internal pressure or an internal temperature of the tank. The back pressure regulating valve according to claim 1,
A seat member for supporting an end opposite to the end supported by the valve body in both ends of the biasing member;
The internal pressure and atmospheric pressure of the tank act on the seat member in opposite directions,
The back pressure regulating valve according to claim 1, wherein the urging force of the urging member acting on the valve body is changed by the displacement of the seat member according to a difference between the internal pressure of the tank and the atmospheric pressure. The back pressure regulating valve according to claim 1,
A thermistor that expands and contracts according to its own temperature,
A support member that supports an end opposite to the end supported by the valve body in both ends of the biasing member, and a seat member that is displaced by expansion and contraction of the thermistor;
The temperature of the thermistor changes according to the internal temperature of the tank,
The back pressure regulating valve according to claim 1, wherein the urging force of the urging member acting on the valve body is varied by the displacement of the seat member in accordance with the temperature of the thermistor. The back pressure regulating valve according to claim 1,
A solenoid coil that generates a magnetic attractive force when energized;
A seat member that supports an end opposite to the end supported by the valve body in both ends of the biasing member, and is displaced by a magnetic attractive force of the solenoid coil;
The energization amount to the solenoid coil is variable according to the internal pressure or the internal temperature of the tank,
The back pressure regulating valve according to claim 1, wherein the urging force of the urging member acting on the valve body is varied by displacing the seat member in accordance with an energization amount to the solenoid coil.

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