JP2022125574A - triple gear pump - Google Patents

Abstract

To provide a triple gear pump that can be stably operated not only in series and parallel modes, but also in a no-loading mode.SOLUTION: A triple gear pump is equipped with one driving gear, and first and second driven gears that respectively engage with the driving gear to respectively configure first and second gear pumps. The triple gear pump discharges a fluid used as fuel. The triple gear pump is equipped with a housing surrounding the first gear pump and the second gear pump, a driving shaft that is united with the driven gears so as to integrally rotate and is pulled out from the housing, a driving shaft bearing that rotatably supports the driving shaft, can floating in an axial direction, and abuts on the driving gear by receiving pressure of the fluid, a mechanical seal that is interposed between the driving shaft and the housing and prevents the leakage of the fluid to the outside of the housing, and a seal that is interposed between the driving shaft bearing and the mechanical seal and prevents the propagation of the pressure of the fluid to the mechanical seal.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present disclosure relates to a floating bearing type triple gear pump that pressurizes and discharges fluid by rotating gears, and more particularly to a triple gear pump that can be stably operated not only in serial and parallel modes but also in no-load mode.

A gear pump normally includes a pair of gears that mesh with each other and a housing that accommodates the gears, and pressurizes and discharges fluid by rotating the pair of gears in a flow path defined by the housing. It is used in reciprocating engines and fuel supply systems for jet engines.

Floating bearings are often used in gear pumps. In a floating-bearing gear pump, the bearings not only support the gear shaft, but are also slightly axially movable to abut and support the gear flanks. Fluid passing through the gear pump is used not only to lubricate the bearings, but also to pressurize the bearings against the sides of the gears.

A triple gear pump has been proposed in which one drive shaft drives two gear pumps simultaneously. A triple gear pump can achieve a relatively small flow rate by operating two gear pumps in series, and a relatively large flow rate by operating two gear pumps in parallel.

Patent Documents 1 and 2 disclose related techniques.

JP-A-2008-50979 International Publication WO2017/009994A1

Floating bearings require pressurization, and in order to ensure smooth operation of the gear pump and to prevent fluid from leaking from the sides of the gears, it is necessary to manage the pressurization within an appropriate range. In a triple gear pump, the pressure of the fluid around the floating bearings varies depending on the operating mode, which cannot be ignored. Resulting in.

The present disclosure relates to a triple gear pump that can stably operate not only in series and parallel modes, but also in no-load mode.

A triple gear pump according to one aspect includes a driving gear and first and second driven gears respectively meshing with the driving gear to form first and second gear pumps, respectively, and is used as fuel. Dispense fluid to be applied. The triple gear pump includes a housing enclosing the first gear pump and the second gear pump, a drive shaft coupled to the drive gear to rotate together, a drive shaft extending from the housing, and a drive shaft for rotating the drive shaft. a drive shaft bearing that is axially floatable and abuts against the drive gear under pressure from the fluid; and a seal interposed between the drive shaft bearing and the mechanical seal to prevent the pressure of the fluid from propagating to the mechanical seal.

Preferably, the triple gear pump includes a driven shaft coupled to said second driven gear, a driven shaft rotatably supporting said driven shaft, being axially floatable and axially abutting against said second driven gear. abutting floating bearing and a communication passage fluidly communicating the drive shaft bearing and the floating bearing within the housing, the seal being interposed between the communication passage and the mechanical seal. More preferably, the triple gear pump further includes an introduction path for introducing the fluid before being pressurized from outside the housing to the mechanical seal. More preferably, the triple gear pump further comprises an inlet opening in said housing and communicating with said second gear pump for introducing said fluid into said second gear pump, said inlet receiving said pressure. It is in fluid communication with the drive shaft bearing, the floating bearing and the communication passage for applying power to the drive shaft bearing and the floating bearing. Also preferably, the seal is a labyrinth seal.

A triple gear pump is provided that can stably operate not only in series and parallel modes, but also in no-load mode.

FIG. 1 is a schematic block diagram of a system for supplying fuel to an aircraft engine, according to one embodiment. FIG. 2 is a cross-sectional plan view of a triple gear pump according to one embodiment. FIG. 3 is a schematic cross-sectional view of a triple gear pump. FIG. 4 is a cross-sectional plan view showing an enlarged view mainly around the floating bearings in the triple gear pump. FIG. 5 is a schematic block diagram illustrating series mode, parallel mode and no-load mode.

Several exemplary embodiments are described below with reference to the accompanying drawings. Throughout the following description and appended claims, the terms "axial" and "axial" are used as defined on a shaft-by-shaft basis.

Referring to FIG. 1, a triple gear pump 1 according to the present embodiment is used by being incorporated in a system for supplying fuel to an aircraft engine 10, for example, and is used for relatively low-viscosity oil such as kerosene. pressurizes and discharges a fluid such as

Fluid is supplied from a tank through a flow path F1, pressurized by a triple gear pump ₁ , and discharged. _Another low pressure pump 3 may be interposed on line F1 for system start-up or other purposes. A centrifugal pump can be used as the low-pressure pump 3, although it is not necessarily limited to this.

Since energy extracted from, for example, the turbine of the engine 10 is used for the power of the triple gear pump 1, the discharge amount of the triple gear pump 1 is usually proportional to or at least dependent on the rotation speed of the turbine. For example, when cruising at high altitudes, the rpm may be relatively high but the fuel consumption may be low, so the discharge does not always match the demand of the engine 10 . Of the fluid discharged there, the portion exceeding the required amount is diverted by the fuel control unit ₅ and returned to the flow path F1 through the return path F3, and _only the required amount is supplied to the engine ₁₀ through the flow path F5. be done.

Since the lubricating oil L circulates in the engine 10 and is heated, the discharged fluid is also used for cooling. That is, the flow path F5 communicates with the oil cooler ₉ , cools the lubricating oil L, and after the fluid itself is preheated, is introduced into the combustion chamber ₇ of the engine 10 via the supply path F7, where it burns. served to

The triple gear pump 1 itself generates heat, and part of the heat is returned to the _triple gear pump ₁ through the return path F3, resulting in an unignorable temperature rise in the fluid in the flow path F5. Therefore, the cooling capacity of the oil cooler 9 is often out of balance with the temperature rise of the lubricating oil L. Therefore, an air-cooled oil cooler 11 using air A bled from a bypass passage of the engine 10 or the like is used as an auxiliary. As the circulation through the circulation path F3 increases _, the temperature of the discharge fluid rises, and the load on the air-cooled oil cooler 11 increases, the thermal stress on each part of the system increases, and thermal energy is wasted. Energy efficiency drops. A conventional triple gear pump enables serial and parallel modes to increase or decrease the discharge amount, thereby minimizing the return amount.

According to the triple gear pump 1 according to this embodiment, not only the series and parallel modes but also the no-load mode are made possible, thereby making it possible to further increase/decrease the discharge amount and to improve the energy efficiency. . That is, for example, when the aircraft is idling on the ground and cruising at high altitudes, the series and parallel modes are used, and when a large flow rate is required, such as during takeoff, the triple gear pump 1 is unloaded. It enables switching such that fuel is exclusively supplied by the centrifugal pump 3. The problem is that high pressure is applied to the entire triple gear pump 1 in the no-load mode, making it difficult to control the pressurization. The solution will become clear from the following description.

Combining FIGS. 2 and 3 and referring mainly to FIG. 3, the triple gear pump 1 generally includes a drive gear 23 driven by one drive shaft 21 and first and second gears meshing with the drive gear 23, respectively. The combination of the driving gear 23 and the first driven gear 27 constitutes the _first gear pump G1, and the combination of the driving gear 23 and the second driven gear 31 constitutes the first gear pump G1. Configure gear pump _G2 . Since the housing 41 surrounds them and is in close contact with the tip of each gear, each of the spaces 43, 45, 47 surrounded by the gear teeth and the housing 41 functions to convey the fluid while pressurizing it according to the rotation of the gears. do. The housing 41 also has an inlet 49 and an outlet 51 communicating with the _first gear pump G1, and an inlet 53 and an outlet 55 communicating with the _second gear pump G2. When the drive gear 23 rotates around its axis by _an external power source, the _first and _second gear pumps G1 and G2 are operated in parallel, and the fluid sucked from the suction port 49 with the pressure P1 is discharged. The fluid is discharged to 51 at pressure P3 _, and the fluid sucked from suction port 53 at pressure P5 is discharged to discharge port ₅₅ at pressure _P7 . Normally the discharge pressures P ₃ and P ₇ are higher than the suction pressures P ₁ and P ₅ respectively, but this depends on the operating mode, as explained below.

Referring mainly to FIG. 2, the drive shaft 21 is pulled out of the housing 41 for connection with the power source, but the shafts 25, 29 of the first and second driven gears 27, 31 are connected to the housing. Enclosed within 41. Each shaft 21, 25, 29 is rotatably supported by a pair of floating bearings 33, 35, 37, respectively. Each floating bearing 33, 35, 37 also encloses a gear 23, 27, 31, respectively. The floating bearings 33, 35, 37 are slightly floatable in the axial direction and abut on both side surfaces of the gears 23, 27, 31, respectively, with appropriate pressurization.

Between both ends of the first and second driven shafts 25, 29 and the floating bearings 35, 37 and the housing 41, gaps are maintained, and fluid flows in by communicating with suction ports 49, 53, respectively. , the fluid in the gap pressurizes the respective ends with suction pressures P ₁ , P ₅ . Such pressurization is utilized to press the floating bearings 35, 37 against the first and second driven gears 27, 31, respectively. For example, the first and second driven shafts 25, 29 are hollow so as to spread the fluid over both ends and exert a uniform pressure. In order to apply such pressurization also to the floating bearing 33 of the drive shaft 21, a communication passage 67 is interposed therebetween for fluidly connecting the floating bearings 37 and 33 together.

For example, both side surfaces of the housing 41 may each be provided with an introduction pipe to introduce a pressure P ₉ different from the suction pressures P ₁ and P ₅ from the outside and exert it on the floating bearings 35 and 37 . To accommodate such pressure P9, the floating bearings 35, ₃₇ may be reduced in diameter at the ends and provided with a step at their shoulders, and the inner ends of the introduction tubes may open towards such shoulders. . The step surface can be used as a surface for receiving the pressure _P9 . A suitable seal, such as a gasket, should be interposed between the end face and the shoulder to suppress mutual pressure propagation. Such an inlet tube can also be connected to, for example, outlet 51 or outlet 55, in which case the pressure _P9 applied to the step surface corresponds in principle to the outlet pressure _P3 or _P7 . A pressurizing means, such as a spring 39, may be interposed between such shoulder and housing 41 to further adjust the pressurization. These are used to adjust the preload to the floating bearings 35,37.

Seals 61 and 63 are interposed between housing 41 and drive shaft 21 to prevent internal fluid leakage. One or both of the seals 61 and 63 may be a mechanical seal that presses the seal surfaces against each other by using elastic force of a spring, for example. A seal 65 is interposed between the communication passage 67 and the seal 61 to prevent the pressure from being applied to the mechanical seal. A labyrinth seal, for example, can be applied to the seal 65 .

The housing 41 may further comprise an introduction passage 69 so as to collect fluid leaking from the labyrinth seal and to apply an appropriate pressure _P11 to the mechanical seal 61. As shown in FIG. For example, a flow path F ₁ can be connected to the introduction path 69 , so that the pressure of the fluid before being pressurized by the triple gear pump 1 can be applied to the mechanical seal 61 . Of course, other appropriate flow paths may be connected.

₄ in combination with FIG. 2, the upper end of the upper floating bearings 33, 37 is acted upon by _a force f1 originating from the suction pressure P5, so that the upper floating bearings 33, 37 and the second driven gear 31 with a downward force _fd . _A force f1 originating from the suction pressure P5 acts _on the lower floating bearing 37 and also on the lower floating bearing 33 due to the intervening passage 67, so that the lower floating bearing 33 , 37 are pressed against the driving gear 23 and the second driven gear 31 by an upward force _fu . Since the common pressure acts, the forces f _d and f _u are balanced and the driving gear 23 and the second driven gear 31 are stably supported. A different (usually larger) force f ₂ is also used to adjust the upward force f _u and thus prevent the floating bearing 37 from disengaging from the second driven gear 31 . can do.

Although the above description relates exclusively to the _second gear pump G2, a similar force balance holds for the _first gear pump G1.

The triple gear pump 1 is operated by being connected to a fuel supply system as shown in FIG. That is, the flow path F1 is branched into _two and connected to the inflow path _F11 and the inflow path _F17 . _A check valve _V1 may be interposed between the flow path F1 and the inflow path _F11 . The inflow paths F ₁₁ and F ₁₇ are connected to the suction ports 49 and 53 of the first and second gear pumps G ₁ and G ₂ respectively. Each discharge port ₅₁ , 55 is connected to the outflow path _F13 , F19, respectively. The inflow path _F11 is also branched into two, one of which is connected to the outflow path _F15 via the valve V3 _, and after joining the outflow paths _F13 and _F19 , the flow path _F21 It is connected to the. Channel _F21 is connected to channel _F5 of the fuel supply system.

Referring to FIG. 5(a) in combination with FIGS. 2 to 4, when valve V3 is closed, _triple gear pump 1 operates in series mode. _At this time, both the inflow path _F11 communicating with the suction port 49 of the _first gear pump G1 and the inflow path _F17 communicating with the suction port 53 of the _second gear pump G2 are compared by the flow path F1. A relatively low pressure is applied. At this time, the pressures P ₁ and P ₅ are both low pressures, and the upper and lower forces f _d and f _u of the floating bearings 33 , 35 and 37 are balanced. The fluid discharged from the discharge port 51 under pressure passes through the outflow passages F ₁₃ and F ₁₅ , the fluid discharged from the discharge port 55 passes through the outflow passage F ₁₉ , and joins at the flow passage F ₂₁ to be fed into the engine 10 . supplied to

Referring to FIG. 5(b) instead of FIG. 5(a), when the valve V3 is opened, the _triple gear pump 1 operates in parallel mode. The outlet pressure P3 of the _first gear pump G1 passes through the valve _V3 to the inlet _F11 and as a result the suction pressure _P1 increases to _match the outlet pressure _P3 . _The intervening non _- return valve V1 prevents the fluid from flowing back toward the flow path F1. Since the common pressure P1 is applied to both floating bearings 35 at this time as well, the _upper and lower forces f _d and f _u are balanced. Also, changes in pressure P1 have _no effect on the floating bearings 33,37. At this time, the _first gear pump G1 idles (does no work) and only the discharge by the _second gear pump G2 contributes to the fluid supply.

A control valve such as a variable throttle valve that can continuously change the flow rate can be applied to the valve _V3 instead of the open/close valve. _In this case, the valve V3 can be in an intermediate state other than fully closed (state shown in FIG. 5(a)) and fully open (state shown in FIG. 5(b)). There is no loss of force balance with respect to the floating bearings 33,35,37.

Referring to FIG. 5(c) instead of FIGS. 5(a) and 5(b), a no-load mode is possible according to this embodiment. At this time, the valve V3 remains open (or may be closed) and the discharge rate of the centrifugal pump ₃ is increased. Then, the high pressure by the centrifugal pump 3 is applied to both gear pumps G ₁ and G ₂ . As can be understood from the above description, not only are the vertical forces f _d and f _u balanced with respect to the floating bearings 35 and 37, but also pressure is applied to the floating bearing 33 of the drive shaft 21 by the communicating passage 67, so that the floating The upper and lower forces f _d and f _u are balanced for the bearing 33 as well. Although high pressure is applied to the floating bearing 33 , the pressure does not reach the mechanical seal 61 due to the labyrinth seal 65 . Fluid does not leak from the mechanical seal 61 to the outside, and smooth operation of the mechanical seal 61 is not impaired.

In the no-load mode, both gear pumps G ₁ , G ₂ do virtually no work and only the centrifugal pump 3 contributes to the supply of fluid. A centrifugal pump can efficiently discharge a large volume of fluid, especially when the engine 10 exhibits high output. As can be understood with reference to FIG. 1 again, the _triple gear pump 1 does not substantially perform any work, and the return flow of the fluid through the return path _F3 can be minimized, so that the flow rate of the fluid supplied to the flow path F5 is reduced. Temperature rise is suppressed. The cooling capacity of the oil cooler 9 can be fully utilized, and the load on the air-cooled oil cooler 11 can be reduced.

For example, the parallel mode is used when the engine 10 requires high output while the speed is low, the parallel mode is used when cruising at high altitudes, and the no-load mode is used exclusively when high output is required, such as when taking off. According to this embodiment, the optimum mode can be selected and used. The present embodiment can realize high energy efficiency in any of them.

Although several embodiments have been described, modifications or variations of the embodiments are possible based on the above disclosure.

1 triple gear pump 3 low pressure pump 5 fuel control unit 7 combustion chamber 9 oil cooler 10 engine 11 air-cooled oil cooler 21 drive shaft 23 drive gear 25 first driven shaft 27 first driven gear 29 second driven shaft 31 second driven gear 33 floating bearing 35 floating bearing 37 floating bearing 39 spring 41 housing 43 space 45 space 47 space 49 suction port 51 discharge port 53 suction port 55 discharge port 61 mechanical seal 63 seal 65 labyrinth seal 67 communication passage 69 introduction passage A air P ₁ pressure P ₃ pressure P ₅ pressure P ₇ pressure P ₉ pressure P ₁₁ pressure f ₁ force f ₂ force f ₃ force f _d downward force f _u upward force F ₁ flow path F ₃ return flow path F ₅ flow path F ₇ supply path F ₁₁ inflow path F ₁₃ outflow path F ₁₅ outflow path F ₁₇ inflow path F ₁₉ outflow path F ₂₁ flow path G ₁ first gear pump G ₂ second gear pump V ₁ check valve V ₃ valve L lubricating oil

Claims (5)

A triple gear pump, comprising one drive gear and first and second driven gears respectively meshing with the drive gear to constitute first and second gear pumps, respectively, and for discharging fluid used as fuel. and
a housing enclosing the first gear pump and the second gear pump;
a drive shaft coupled to the drive gear for rotation therewith and extending from the housing;
a drive shaft bearing that rotatably supports the drive shaft, is axially floatable, and abuts against the drive gear under pressure from the fluid;
a mechanical seal interposed between the drive shaft and the housing to prevent the fluid from leaking out of the housing;
a seal interposed between the drive shaft bearing and the mechanical seal to prevent the pressure of the fluid from propagating to the mechanical seal;
Triple gear pump with a driven shaft coupled to the second driven gear;
a floating bearing that rotatably supports the driven shaft, is axially floatable, and axially abuts the second driven gear;
a communication passage that fluidly communicates the drive shaft bearing and the floating bearing within the housing;
2. The triple gear pump of claim 1, wherein said seal is interposed between said communication passage and said mechanical seal. further comprising an inlet opening in said housing communicating with said second gear pump for introducing said fluid into said second gear pump;
3. The triple gear pump of claim 2, wherein said inlet is in fluid communication with said drive shaft bearing, said floating bearing and said communication passage to apply said pressure to said drive shaft bearing and said floating bearing. an introduction path for introducing the fluid before being pressurized from the outside of the housing to the mechanical seal,
4. The triple gear pump of any one of claims 1-3, further comprising: 5. A triple gear pump according to any one of claims 1 to 4, wherein said seal is a labyrinth seal.

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