JP2011163209A - Differential pressure control valve and fuel flow rate control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the controllability of a fuel flow rate control device by preventing the generation of a fluid force or a fluid fixing force in a differential pressure control unit, in the fuel flow rate control device including the differential pressure control unit. <P>SOLUTION: The control valve 21 of the differential pressure section includes a control valve piston 23 formed with a large diameter portion and a small diameter portion. A through-hole penetrating the control valve piston is opened in the control valve piston. A flapper 24 having a diameter smaller than that of the through-hole is inserted into the through-hole. The opening degree of the through-hole is adjusted by the relative displacement between the flapper and the control valve piston. Discharge pressure from a fixed positive displacement fuel pump is applied to the small diameter pressure receiving surface of the small diameter portion. Pressure penetrating the through-hole and depressurized is applied to the large diameter pressure receiving surface of the large diameter portion. A pressure difference sensing piston and the flapper are connected to each other, and the control valve piston is displaced by following the displacement of the pressure difference sensing piston through the flapper. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a differential pressure control valve and a fuel flow rate control device for controlling a fuel supply amount to a jet engine or a gas turbine.

  The fuel flow control device of a jet engine is composed of a constant displacement fuel pump, a differential pressure control valve, a metering valve, etc., and controls the opening of the metering valve according to a metering valve opening command from an electronic control unit. , Weigh the fuel.

  The constant displacement fuel pump is directly connected to and driven by a high pressure system of the engine, and discharges a fuel flow rate proportional to the engine speed. The metering valve is determined to have an arbitrary opening area by feedback control of an electronic control unit, and the differential pressure control valve constantly maintains the metering valve differential pressure between the inlet pressure and the outlet pressure of the metering valve, The metered fuel passing through the metering valve is always proportional to the metering valve opening.

  An example of a conventional fuel flow control device for a jet engine is shown in FIG.

  The fuel flow control device 1 includes a constant displacement fuel pump 2, a differential pressure control unit 3, a fuel pressurization valve 4, a metering valve 5, a flap valve 6 for adjusting the opening of the metering valve 5, and the like.

  The constant displacement fuel pump 2 discharges a fuel flow rate proportional to the engine speed, and the discharged fuel is increased from the inlet pressure P1 to the discharge pressure P2. The flap valve 6 is driven by an opening command from an electronic control unit (not shown), the opening of the metering valve 5 is adjusted by the flap valve 6, and fuel discharged from the constant displacement fuel pump 2 is measured. is doing.

  The differential pressure control unit 3 includes a differential pressure sensing valve 7 and a bypass valve 8. The differential pressure sensing valve 7 detects the differential pressure between the discharge pressure P2 from the constant displacement fuel pump 2 and the measured pressure P3 measured by the metering valve 5, and transmits the servo pressure P4 to the bypass valve 8. To do. At this time, the metering pressure P3 is determined by the opening degree of the metering valve 5.

  The discharge pressure P2 acts on the bypass valve 8, and the opening degree of the bypass valve 8 is determined by the differential pressure between the discharge pressure P2 and the servo pressure P4, and according to the opening degree of the bypass valve 8. A part of the discharge flow rate from the constant displacement fuel pump 2 is bypassed and returned to the inlet side of the discharge pressure P2 through the bypass valve 8 at the flow rate. As a result, the amount of fuel supplied from the metering valve 5 to the fuel pressurizing valve 4 and the orifice 9 increases or decreases. That is, the fuel supply flow rate from the metering valve 5 is controlled to a predetermined amount by the bypass fuel flow rate control of the bypass valve 8, and the fuel whose flow rate is controlled passes through the fuel pressurization valve 4 and the orifice 9 to the jet engine (FIG. Not shown).

  On the other hand, the fuel from the constant displacement fuel pump 2 in which the discharge pressure P2 is applied to the differential pressure sensing valve 7 is reduced to the inlet pressure P1 and returned to the inlet side of the constant displacement fuel pump 2.

  For this reason, a high pressure, that is, a large differential pressure and a large flow of fuel always pass through the differential pressure sensing valve 7. From this large differential pressure, there is a possibility that a fluid force acts on the piston of the differential pressure sensing valve 7 or a fluid adhering force that is fixed by pressing the piston against the wall surface by the fluid force.

  For this reason, there is a possibility that the differential pressure sensing valve 7 does not operate normally or a response delay occurs.

JP-A-7-54672

  In view of such circumstances, the present invention prevents the generation of fluid force or fluid adhering force in the differential pressure control unit and improves the controllability of the fuel flow control device in the fuel flow control device having the differential pressure control unit. It is something to be made.

  The present invention includes a differential pressure sensing valve that outputs a pressure difference acting on a differential pressure sensing piston as a displacement of the differential pressure sensing piston, and a control valve that controls a flow rate or servo pressure by the displacement of the piston. Has a control valve piston having a large diameter portion and a small diameter portion, a low pressure acting on the large diameter pressure receiving surface of the large diameter portion, and a high pressure acting on the small diameter pressure receiving surface of the small diameter portion, the control valve The piston has a through-hole penetrating through the center and communicating the small-diameter pressure receiving surface and the large-diameter pressure-receiving surface, and a flapper having a smaller diameter than the through-hole is inserted into the through-hole. The flapper and the control valve piston The differential pressure sensing piston and the flapper are connected to each other so that the degree of opening of the through hole is adjusted by relative displacement with the control valve piston via the flapper. Configured to follow and displace It relates to a pressure control valve.

  Further, according to the present invention, the cylinder of the differential pressure sensing valve and the cylinder of the control valve are disposed on the same axis, a high pressure chamber is formed between both cylinders, and opposite ends of both cylinders are opposed to the high pressure chamber. The fluid pressure to be detected acts on the differential pressure sensing piston and the pressure from the high pressure chamber acts, and the pressure of the high pressure chamber acts on the small diameter pressure receiving surface of the control valve piston. The radial pressure receiving surface relates to a differential pressure control valve configured to pass through the through hole and to apply a reduced pressure.

  The present invention also provides a metering valve for measuring the supply flow rate of the discharged fuel from the constant displacement fuel pump, a bypass line for bypassing the discharged fuel from the constant displacement fuel pump to the inlet side of the constant displacement fuel pump, A differential pressure control unit provided in the bypass line, and the differential pressure control unit includes: a discharge pressure from the constant displacement fuel pump acting on a differential pressure sensing piston; a metering pressure after metering by the metering valve; A differential pressure sensing valve that outputs the pressure difference as a displacement of the differential pressure sensing piston, and a control valve that controls the fuel return flow rate by the bypass line by the displacement of the piston, the control valve having a large diameter portion and a small diameter portion. A control valve piston formed, a through hole penetrating the control valve piston is formed, and a flapper having a smaller diameter than the through hole is inserted into the through hole; the flapper and the control valve piston And the discharge pressure from the constant displacement fuel pump acts on the small diameter pressure receiving surface of the small diameter portion, and the large diameter pressure receiving surface of the large diameter portion is adjusted. Is configured so that a reduced pressure acts through the through-hole, and connects the differential pressure sensing piston and the flapper, and the control valve piston moves through the flapper to the displacement of the differential pressure sensing piston. The present invention relates to a fuel flow control device configured to follow and displace.

  The present invention also provides a metering valve for measuring the supply flow rate of the discharged fuel from the constant displacement fuel pump, a bypass line for bypassing the discharged fuel from the constant displacement fuel pump to the inlet side of the constant displacement fuel pump, A differential pressure control unit provided in the bypass line, and the differential pressure control unit includes: a discharge pressure from the constant displacement fuel pump acting on a differential pressure sensing piston; a metering pressure after metering by the metering valve; A differential pressure sensing valve that outputs the pressure difference as a displacement of the differential pressure sensing piston, a control valve that controls the servo pressure by the displacement of the piston, and a bypass valve that controls the fuel flow to be bypassed by controlling the opening degree by the servo pressure The control valve has a control valve piston having a large diameter portion and a small diameter portion, and has a through hole penetrating the control valve piston, and the through hole has a smaller diameter than the through hole. A flapper is inserted, and the opening degree of the through hole is adjusted by relative displacement between the flapper and the control valve piston, and the discharge pressure from the constant displacement fuel pump is applied to the small diameter pressure receiving surface of the small diameter portion. The large pressure receiving surface of the large diameter portion passes through the through-hole and is configured so that a reduced pressure acts, and the differential pressure sensing piston and the flapper are connected, and the differential pressure sensing piston The fuel flow control device is configured such that the control valve piston is displaced following the displacement of the control valve via the flapper.

  According to the present invention, there is provided a differential pressure sensing valve that outputs a pressure difference acting on the differential pressure sensing piston as a displacement of the differential pressure sensing piston, and a control valve that controls a flow rate or a servo pressure by the displacement of the piston, The control valve has a large-diameter portion and a small-diameter portion, and has a control-valve piston configured so that a low pressure acts on the large-diameter pressure receiving surface of the large-diameter portion and a high-pressure acts on the small-diameter pressure-receiving surface of the small diameter portion, The control valve piston has a through hole penetrating the center portion and communicating the small diameter pressure receiving surface and the large diameter pressure receiving surface, and a flapper having a smaller diameter than the through hole is inserted into the through hole. The opening degree of the through hole is adjusted by relative displacement with the valve piston, the differential pressure sensing piston and the flapper are connected, and the control valve is connected to the displacement of the differential pressure sensing piston via the flapper. A structure in which the piston follows and displaces Therefore, the hydraulic pressure that acts on the control valve uses the maximum differential pressure of the fuel flow control device, and even if an external force such as a fluid force or a fluid adhering force is applied, the piston is moved quickly and sufficiently by the change in the large-diameter pressure. It is possible to drive with a large margin (force margin), and furthermore, since a large differential pressure does not act on the differential pressure sensing valve that detects subtle changes in metering pressure, the generation of fluid force and fluid adhering force is prevented. it can.

  According to the present invention, the metering valve for measuring the supply flow rate of the discharged fuel from the constant displacement fuel pump, the bypass line for bypassing the discharged fuel from the constant displacement fuel pump to the inlet side of the constant displacement fuel pump, And a differential pressure control unit provided in the bypass line, wherein the differential pressure control unit measures the discharge pressure from the constant volume fuel pump acting on the differential pressure sensing piston and the metering valve after metering. A differential pressure sensing valve that outputs a pressure difference from the pressure as a displacement of the differential pressure sensing piston, and a control valve that controls a fuel return flow rate by a bypass line by the displacement of the piston, the control valve having a large diameter portion and a small diameter A control valve piston having a portion formed therein, a through hole penetrating the control valve piston is formed, and a flapper having a smaller diameter than the through hole is inserted into the through hole. The degree of opening of the through hole is adjusted by relative displacement with the ton, and the discharge pressure from the constant displacement fuel pump acts on the small diameter pressure receiving surface of the small diameter portion, and the large diameter pressure receiving pressure of the large diameter portion The surface passes through the through-hole and is configured such that a reduced pressure is applied, the differential pressure sensing piston and the flapper are connected, and the control valve is connected to the displacement of the differential pressure sensing piston via the flapper. Since the piston is configured to follow and displace, the hydraulic pressure applied to the control valve uses the maximum differential pressure of the fuel flow control device, and even if an external force such as fluid force or fluid adhering force is applied, the large diameter part It is possible to drive the piston at a high speed with sufficient remaining force (force margin) due to the change in pressure, and since a large differential pressure does not act on the differential pressure sensing valve that detects subtle changes in the metering pressure, Physical fitness The occurrence of body fixing force can be prevented.

  According to the present invention, the metering valve for measuring the supply flow rate of the discharged fuel from the constant displacement fuel pump, the bypass line for bypassing the discharged fuel from the constant displacement fuel pump to the inlet side of the constant displacement fuel pump, And a differential pressure control unit provided in the bypass line, wherein the differential pressure control unit measures the discharge pressure from the constant volume fuel pump acting on the differential pressure sensing piston and the metering valve after metering. A differential pressure sensing valve that outputs the pressure difference from the pressure as a displacement of the differential pressure sensing piston, a control valve that controls the servo pressure by the displacement of the piston, and the opening degree is controlled by the servo pressure to control the fuel flow rate to bypass A bypass valve, the control valve having a control valve piston formed with a large diameter portion and a small diameter portion, a through hole penetrating the control valve piston is formed, and the through hole is connected to the through hole. A small-diameter flapper is inserted, and the opening degree of the through-hole is adjusted by relative displacement between the flapper and the control valve piston, and the small-diameter pressure receiving surface of the small-diameter portion discharges from the constant displacement fuel pump. Pressure is applied, the large diameter pressure receiving surface of the large diameter portion passes through the through hole, and the pressure reduced pressure is applied, the differential pressure sensing piston and the flapper are connected, and the differential pressure Since the control valve piston is configured to follow the displacement of the sensing piston via the flapper, the hydraulic pressure applied to the control valve uses the maximum differential pressure of the fuel flow control device, and the fluid force The piston can be driven at a high speed and with sufficient remaining force (force margin) by the change in the large-diameter pressure even when an external force such as a fluid adhering force is applied, and a subtle change in the metering pressure is detected. Since the difference between pressure sensing valve does not act a large differential pressure, there is exhibited an excellent effect that can prevent the occurrence of fluid force and the fluid fixing strength.

1 is a schematic configuration diagram of a fuel flow control device according to a first embodiment of the present invention. It is a differential pressure control part enlarged view of this fuel flow control device. (A) and (B) are enlarged views of the differential pressure control unit of the fuel flow control device, showing a case where the metering pressure is changed to be small. (A) and (B) are enlarged views of the differential pressure control unit of the fuel flow control device, showing a case where the metering pressure changes so as to increase. It is a schematic block diagram of the fuel flow control apparatus which concerns on 2nd Example of this invention. (A) and (B) are enlarged views of a differential pressure control unit of the fuel flow control device. It is a schematic block diagram of the conventional fuel flow control apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIGS. In FIGS. 1 and 2, the same components as those in FIG.

  The discharge line 15 of the constant displacement fuel pump 2 is provided with a metering valve 5 and a fuel pressurization valve 4 in the downstream direction, and a fuel supply line 16 from the fuel pressurization valve 4 is provided with an orifice 9. Fuel is supplied to the jet engine (not shown) through the pressurizing valve 4 and the orifice 9.

  A bypass line 17 communicating with the discharge side of the constant displacement fuel pump 2 and further communicating with the inlet side of the constant displacement fuel pump 2 is provided, and the differential pressure control unit 3 is provided in the bypass line 17. A bypass connection line 18 communicating with the fuel supply line 16 is connected to the fuel pressurizing valve 4 so that an inlet side pressure P1 acts on the fuel pressurizing valve 4 as a back pressure.

  The differential pressure control unit 3 includes a differential pressure sensing valve 20 and a control valve 21 that also serves as a servo valve. The piston 22 of the differential pressure sensing valve 20 and the piston 23 of the control valve 21 are mechanically coupled by a flapper 24. It is connected to.

  The metering valve 5 and the differential pressure sensing valve 20 are connected to each other by the metering pressure line 25 so that the metering pressure P3 and the discharge pressure P2 act on the differential pressure sensing valve 20, and the pressure difference between the discharge line 15 and the differential pressure sensing valve 20. The sensing valve 20 is connected by a bypass line 17. The control valve 21 is provided in the middle of the bypass line 17, and fuel returned from the bypass line 17 through the control valve 21 to the fixed displacement fuel pump 2 inlet side is discharged through the control valve 21. The pressure is reduced from P2 to the inlet pressure P1.

  Next, the differential pressure control unit 3 will be further described with reference to FIG.

  A piston 22 is slidably provided in a cylinder chamber 29 of the differential pressure sensing valve 20, and the piston 22 is urged in a protruding direction by a spring 28. A metering pressure line 25 is connected to the cylinder chamber 29, and the metering pressure P 3 acts on the cylinder chamber 29.

  A piston 23 is slidably provided in the cylinder chamber of the control valve 21. The piston 23 has a convex shape in a longitudinal section composed of a large diameter portion 23a and a small diameter portion 23b, and hydraulic chambers 32 and 33 are formed on both sides of the large diameter portion 23a. The hydraulic chamber 32 and the hydraulic chamber 33 communicate with each other via a throttle 34, and a recess 35 is formed on the peripheral surface of the piston 23. The area ratio between the large diameter portion 23a and the small diameter portion 23b is, for example, 2: 1.

  A through hole 36 is formed at the center of the piston 23, and a small diameter throttle hole 36a is provided at the tip of the through hole 36. The flapper 24 is inserted into the through hole 36, and a variable throttle 41 is formed by the tip of the flapper 24 and the throttle hole 36a. The through hole 36 is an oil passage that communicates with a hydraulic chamber 37 described later via the variable throttle 41.

  One end (base end) of the flapper 24 is connected to the piston 22, and a distal end is a valve portion 24 a having a tapered shape. The valve portion 24 a is in the axial direction of the piston 23 and the flapper 24. By the relative displacement, the gap with the aperture hole 36a changes, and the aperture of the aperture changes. The opening area of the variable throttle 41 is set to be equal to the opening area of the diaphragm 34 when the piston 22 and the piston 23 are balanced.

  A hydraulic chamber 37 is formed between the differential pressure sensing valve 20 and the control valve 21.

  The bypass line 17 on the high pressure side communicates with the hydraulic chamber 37 and always communicates with the recess 35 via the first port 38. The bypass line 17 on the low pressure side is always communicated with the hydraulic chamber 32 via the second port 39 and also communicated with the recess 35 via the third port 40, and the bypass port 17 of the third port 40 depends on the position of the piston 23. The opening is adjusted.

  Thus, the bypass line 17 communicates the outlet side and the inlet side of the constant displacement fuel pump 2 via the first port 38, the recess 35, and the third port 40, and is returned by bypass. Is adjusted by the position of the piston 23.

  The operation of the first embodiment will be described below.

  With respect to the differential pressure sensing valve 20, the position of the piston 22 is determined by the balance between the differential pressure between the pressure (P 3) of the cylinder chamber 29 and the pressure (P 2) of the hydraulic chamber 37 and the reaction force of the spring 28. Is done. That is, the position of the piston 22 is determined by the differential pressure between the metering pressure P3 and the discharge pressure P2, that is, the metering state of the metering valve 5.

  The position of the piston 22 is transmitted by the piston 23 by the flapper 24, and the position of the piston 23 is determined by the position of the piston 22. The opening degree of the third port 40 is determined by the position of the piston 23, and the fuel return flow rate by the bypass line 17 is determined.

  Thus, the metering action of the metering valve 5 is reflected in the determination of the flow rate delivered to the discharge line 15.

  Next, the operation of the control valve 21 will be described.

  Since the pressure receiving area of the small diameter portion 23b of the piston 23 and the pressure receiving area of the large diameter portion 23a are in a 1: 2 relationship, the relative movement between the piston 22 and the piston 23 is stopped. The pressure P5 is substantially between the pressures P2 and P1. That is, the displacement of the piston 23 stops when the aperture of the aperture 34 becomes equal to the aperture of the aperture 36a. This position is the null position (neutral position) of the opening of the throttle hole 36a.

  From the neutral state shown in FIG. 2, the metering pressure P3 becomes smaller than the discharge pressure P2, and as shown in FIG. 3 (A), the piston 22 is displaced to the left in the figure and follows the piston 22. When the flapper 24 is displaced to the left, the opening area of the variable throttle 41 increases. As a result, high-pressure oil flows into the hydraulic chamber 33 through the variable throttle 41, and the pressure P5 in the hydraulic chamber 33 is increased. Increase. As the pressure in the hydraulic chamber 33 increases, the piston 23 is displaced to the left, and the piston 23 stops at a position where the opening area of the variable throttle 41 becomes equal to the opening area of the throttle 34 (FIG. 3). (See (B)). Further, the displacement of the piston 23 to the left increases the opening area of the third port 40 and increases the return amount to the bypass line 17. That is, the amount of fuel oil supplied decreases.

  Further, from the neutral state shown in FIG. 2, the metering pressure P3 becomes larger than the discharge pressure P2, the piston 22 is displaced to the right in the figure as shown in FIG. Is displaced to the right, the opening area of the variable throttle 41 decreases, and as a result, the flow of high-pressure oil into the hydraulic chamber 33 is further throttled by the variable throttle 41, and the pressure P5 in the hydraulic chamber 33 decreases. To do. As the pressure in the hydraulic chamber 33 decreases, the piston 23 is displaced to the right, and the piston 23 stops at a position where the opening area of the variable throttle 41 becomes equal to the opening area of the throttle 34 (FIG. 4). (See (B)). Further, the displacement of the piston 23 to the right decreases the opening area of the third port 40, and the amount of return to the bypass line 17 decreases. That is, the amount of fuel oil supplied increases.

  The piston 23 is displaced following the position of the flapper 24, whereby the opening degree of the third port 40 is adjusted and the return amount of fuel is adjusted. At this time, the displacement of the flapper 24 is determined by the displacement of the piston 22, and the displacement of the piston 22 is determined by the differential pressure between the metering pressure P3 and the discharge pressure P2 determined by the opening of the metering valve 5. Is done. Therefore, the metering action by the metering valve 5 is quickly reflected in the fuel supply amount.

  Further, the hydraulic pressure applied to the piston 23 becomes the discharge pressure P2 and the inlet pressure P1, and the maximum differential pressure of the fuel flow control device 1 is used, and even if an external force such as a fluid force or a fluid adhering force is applied. The piston 23 can be driven at a high speed and with a sufficient remaining force (force margin) by changing the pressure of the diameter portion 23a.

  The differential pressure acting on the piston 22 slightly changes due to the metering action of the metering valve 5, but the pressure difference acting on the piston 22 of the differential pressure sensing valve 20 that senses this differential pressure is different from the discharge pressure P2. It is a differential pressure with the metering pressure P3, which is smaller than the differential pressure between the conventional discharge pressure P2 and the inlet side pressure P1, and generates less fluid force and fluid adhering force.

  Therefore, in the present embodiment, the differential pressure sensing valve is less susceptible to disturbance, and the control valve 21 is configured to be resistant to external force, so that the differential pressure control unit 3 and the fuel flow control device 1 that are less susceptible to external force can be configured. Is possible.

  The flapper 24 can be appropriately displaced or amplified by a link mechanism, and a desired null state can be set by appropriately selecting the area ratio of the large diameter portion 23a and the small diameter portion 23b. .

  The second embodiment will be described with reference to FIGS. The second embodiment has the same configuration as that of the first embodiment except for the differential pressure control unit 3, and is equivalent to that shown in FIGS. 5, 6, 1, 2, and 7. Are denoted by the same reference numerals, and the description thereof is omitted.

  In the second embodiment, the bypass valve 42 is provided independently in the differential pressure control unit 3, and the bypass valve 42 is provided in the middle of the bypass line 17. The flow rate at which the fuel discharged from the constant volume fuel pump 2 is bypassed and returned is adjusted.

  In FIG. 6, the control valve 21 is provided with a fourth port 43 and a fifth port 44 as inlet ports, and a second port 39 and a third port 40 as outlet ports. The bypass connection line 18 communicates with the fourth port 43, and low-pressure (inlet pressure P1) fuel flows into the fourth port 43.

  The fifth port 44 communicates with the discharge side of the constant displacement fuel pump 2 by the bypass line 17 so that high pressure (discharge pressure P2) fuel flows into the fifth port 44.

  When the piston 23 of the control valve 21 is in a neutral position (see FIG. 6A), the fourth port 43 and the fifth port 44 are both sealed, and the piston 23 is displaced, One of the fourth port 43 and the fifth port 44 communicates with the recess 35.

  The second port 39 is connected to the bypass line 17 by a second bypass connection line 45, and a low pressure (inlet pressure P1) acts on the second port 39. The third port 40 is always in communication with the recess 35, and the third port 40 is connected to the bypass valve 42 by a servo line 46. The servo pressure is applied to the bypass valve 42 via the servo line 46. P4 is made to act.

  When the metering flow rate is changed by the metering valve 5, this change appears in the change of the metering pressure P3, and the metering pressure P3 acting on the cylinder chamber 29 changes. For this reason, the position of the piston 22 is displaced, and the flapper 24 is displaced.

  As described above, the flapper opening is changed by the displacement of the flapper 24, and the position of the piston 23 is displaced so that the flapper opening becomes the null position. That is, the displacement of the piston 22 is transmitted to the piston 23 of the control valve 21 through the flapper 24.

  For example, when it is desired to decrease the fuel supply flow rate, the opening of the metering valve 5 is adjusted to change the metering pressure P3 to the low pressure side. At this time, the piston 22 is displaced to the left in FIG. 3 under the force of the differential pressure between the metering pressure P3 and the discharge pressure P2, and the piston 23 is displaced to the left via the flapper 24 (FIG. 6). (See (B)). The fourth port 43 and the recess 35 communicate with each other so that a low pressure inlet pressure P1 acts on the fourth port 43, and the servo pressure P4 output from the third port 40 decreases. As the servo pressure P4 decreases, the piston of the bypass valve 42 is displaced leftward to increase the opening, and the amount of fuel returned increases. That is, the amount of fuel supplied from the fuel supply line 16 decreases.

  Also in the second embodiment, the hydraulic pressure applied to the piston 23 of the control valve 21 is the discharge pressure P2 and the inlet pressure P1, and the maximum differential pressure of the fuel flow control device 1 is used. Less susceptible to external forces such as fluid force and fluid adhering force. The pressure difference acting on the piston 22 of the differential pressure sensing valve 20 is a differential pressure between the discharge pressure P2 and the metering pressure P3, which is smaller than the differential pressure between the conventional discharge pressure P2 and the inlet pressure P1. There is little generation of fluid force or fluid adhering force.

  Therefore, also in the second embodiment, the differential pressure sensing valve is not easily affected by disturbance, and the control valve 21 is configured to be resistant to external force, and the differential pressure control unit 3 and the fuel flow rate control device 1 which are not easily affected by external force. Can be configured.

DESCRIPTION OF SYMBOLS 1 Fuel flow control apparatus 2 Constant displacement type fuel pump 3 Differential pressure control part 4 Fuel pressurization valve 5 Metering valve 6 Flap valve 8 Bypass valve 15 Discharge line 16 Fuel supply line 17 Bypass line 18 Bypass connection line 20 Differential pressure sensing valve 21 Control Valve 24 Flapper 24a Valve part 37 Hydraulic chamber 45 Second bypass connection line P1 Inlet pressure P2 Discharge pressure P3 Metering pressure P4 Servo pressure

Claims (4)

  A differential pressure sensing valve that outputs a pressure difference acting on the differential pressure sensing piston as a displacement of the differential pressure sensing piston, and a control valve that controls the flow rate or servo pressure by the displacement of the piston, the control valve having a large diameter portion And a control valve piston that is configured so that a low pressure acts on the large diameter pressure receiving surface of the large diameter portion and a high pressure acts on the small diameter pressure receiving surface of the small diameter portion. A through-hole is formed through which the small-diameter pressure receiving surface communicates with the large-diameter pressure-receiving surface, and a flapper having a smaller diameter than the through-hole is inserted into the through-hole, and the relative displacement between the flapper and the control valve piston The degree of opening of the through hole is adjusted by connecting the differential pressure sensing piston and the flapper, and the control valve piston follows the displacement of the differential pressure sensing piston via the flapper. It is configured to do Differential pressure control valve to be.   The cylinder of the differential pressure sensing valve and the cylinder of the control valve are arranged on the same axis, a high pressure chamber is formed between both cylinders, opposite ends of both cylinders open to the high pressure chamber, The pressure of the detection target fluid pressure acts on the differential pressure sensing piston and the pressure from the high pressure chamber acts, the pressure of the high pressure chamber acts on the small diameter pressure receiving surface of the control valve piston and the large diameter pressure receiving surface. 2. The differential pressure control valve according to claim 1, wherein a pressure reduced pressure is applied through the through hole.   A metering valve for measuring the supply flow rate of the discharged fuel from the constant displacement fuel pump, a bypass line for bypassing the discharged fuel from the constant displacement fuel pump to the inlet side of the constant displacement fuel pump, and the bypass line A differential pressure control unit, and the differential pressure control unit provides a difference between a discharge pressure from the constant displacement fuel pump acting on the differential pressure sensing piston and a measured pressure after metering by the metering valve. A differential pressure sensing valve that outputs as a displacement of the pressure sensing piston, and a control valve that controls the fuel return flow rate by the bypass line by the displacement of the piston, the control valve having a large diameter portion and a small diameter portion A through-hole penetrating the control valve piston is provided, and a flapper having a smaller diameter than the through-hole is inserted into the through-hole. The relative displacement between the flapper and the control valve piston The opening degree of the through hole is adjusted, and the discharge pressure from the constant displacement fuel pump acts on the small diameter pressure receiving surface of the small diameter portion, and the through hole is formed on the large diameter pressure receiving surface of the large diameter portion. The differential pressure sensing piston and the flapper are connected, and the control valve piston follows the displacement of the differential pressure sensing piston via the flapper. A fuel flow control device configured to do so.   A metering valve for measuring the supply flow rate of the discharged fuel from the constant displacement fuel pump, a bypass line for bypassing the discharged fuel from the constant displacement fuel pump to the inlet side of the constant displacement fuel pump, and the bypass line A differential pressure control unit, and the differential pressure control unit provides a difference between a discharge pressure from the constant displacement fuel pump acting on the differential pressure sensing piston and a measured pressure after metering by the metering valve. A differential pressure sensing valve that outputs the displacement of the pressure sensing piston, a control valve that controls the servo pressure by the displacement of the piston, and a bypass valve that controls the fuel flow rate to be bypassed, the opening degree of which is controlled by the servo pressure, The control valve has a control valve piston having a large-diameter portion and a small-diameter portion, and has a through hole penetrating the control valve piston, and a flapper having a smaller diameter than the through-hole is formed in the through-hole. The opening degree of the through hole is adjusted by relative displacement between the flapper and the control valve piston, and the discharge pressure from the constant displacement fuel pump acts on the small diameter pressure receiving surface of the small diameter portion. The large-diameter pressure receiving surface of the large-diameter portion passes through the through-hole and is configured such that a reduced pressure acts, connects the differential pressure sensing piston and the flapper, and displaces the differential pressure sensing piston. Further, the fuel flow control device is configured such that the control valve piston is displaced following the flapper.

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