JP5163573B2 - Shaft support structure - Google Patents

Description

  The present invention relates to a shaft support structure including a hydrostatic bearing that supports a shaft section, and more particularly to a shaft support structure of a shaft section included in a gear pump.

  2. Description of the Related Art Conventionally, in an aircraft or the like, fuel to be supplied to a combustor is boosted and supplied by a pump such as a gear pump (for example, see Patent Document 1). Such an aircraft or the like includes a shaft support structure that supports a shaft portion connected to a rotating body such as a gear of a gear pump. This shaft supporting structure includes a rotating body in addition to a general hydrodynamic bearing. In some cases, a hydrostatic bearing that ejects fluid toward the shaft portion and pivotally supports the shaft portion is provided so that the load on the shaft portion is reduced even when the rotation speed is low.

In particular, in an aircraft, fuel discharged from the pump is used as a working fluid in a shaft support structure. That is, a low-viscosity fluid is used as the working fluid.
In order for a hydrodynamic bearing to function satisfactorily, it is necessary to form a film made of a working fluid having a sufficient thickness with respect to the surface roughness of the bearing. However, as described in Non-Patent Document 1, the thickness of the film made of the working fluid is a function of the Sommerfeld number, and the viscosity of the working fluid is low and the rotating body rotates at a low speed. As a result, the Sommerfeld number decreases and the film thickness decreases. For this reason, when the viscosity of the working fluid is low and the rotating body is rotating at a low speed, it is difficult to allow the dynamic pressure bearing to function well, and the shaft portion easily comes into contact with the surrounding wall surface.
For this reason, the structure in which the shaft support structure includes a hydrostatic bearing in addition to the dynamic pressure bearing is often employed.

  The hydrostatic bearing is configured to be supplied with fuel from a bypass flow path connected to a flow path of fuel discharged from the pump. A part of the fuel discharged from the pump flows into the bypass flow path and is automatically supplied to the hydrostatic bearing.

JP 2005-233014 A

Eiichi Watabayashi, Hisayoshi Tahara, “Bearing Story”, Japan Standards Association, March 5, 1987 Issue 1st edition, November 6, 1992 Issue 8

  However, when fuel is used as the fluid ejected from the hydrostatic bearing as described above, a part of the fuel discharged from the pump is supplied to the hydrostatic bearing, so that the apparent volumetric efficiency of the pump Decreases.

In particular, when the pump is started, the pressure increase speed of the fuel decreases due to the above-described decrease in the apparent volumetric efficiency of the pump. For this reason, it takes time until the fuel pressure increases to the pressure required by the supply destination.
For example, when starting an aircraft engine from a stopped state, the pump is first driven, and when the fuel is boosted to a predetermined pressure, the control valve is opened and the fuel control device is activated, Fuel supply to the combustion chamber is started. For this reason, when it takes time until the fuel pressure is increased to the pressure required for the supply destination as described above, the time until the engine is started becomes long.
In order to avoid such a problem, a pump having a sufficiently large volumetric efficiency may be used, but in such a case, the pump becomes large.

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to improve the apparent volumetric efficiency of the pump at the time of starting without increasing the size of the pump and improve the fuel pressure increase speed. .

  In order to achieve the above object, the present invention provides a hydrostatic bearing that supports a shaft portion by ejecting the supplied fuel and supplying a part of the fuel discharged from a pump to a supply destination. A fuel supply restricting means capable of restricting the supply of fuel to the hydrostatic bearing when the pressure of the fuel discharged from the pump is equal to or lower than the pressure required by the supply destination. It is characterized by providing.

  According to the present invention having such characteristics, when the pressure of the fuel discharged from the pump is equal to or lower than the pressure required by the supply destination by the fuel supply restricting means, a part of the fuel discharged from the pump is static. Supply to the pressure bearing can be limited.

  In the present invention, the fuel supply restriction means stops supplying fuel to the hydrostatic bearing when the pressure of the fuel discharged from the pump is equal to or lower than the pressure required by the supply destination. Is adopted.

  In the present invention, the fuel supply restricting means is a check valve that opens when the pressure of the fuel discharged from the pump is higher than the pressure required by the supply destination.

  In the present invention, the pump is a gear pump including a gear for boosting the fuel and a shaft connected to the gear, and the shaft supported by the hydrostatic bearing is connected to the gear. A configuration that is a shaft portion is adopted.

  Moreover, in this invention, the structure provided with the dynamic pressure bearing which supports the said axial part is employ | adopted.

According to the present invention, when the pressure of the fuel discharged from the pump is equal to or lower than the pressure required by the supply destination, a part of the fuel discharged from the pump is supplied to the hydrostatic bearing by the fuel supply restriction unit. Can be limited.
For this reason, according to the present invention, when the fuel pressure is increased by the pump (that is, when the pressure of the fuel discharged from the pump is equal to or lower than the pressure required by the supply destination), a part of the fuel discharged from the pump is By limiting the supply to the hydrostatic bearing, it is possible to improve the apparent volumetric efficiency of the pump at the time of starting and improve the fuel pressure increase speed.
Therefore, when the present invention is applied to an aircraft, it is possible to shorten the engine start start time without installing a pump with a large output.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a gear pump that employs a shaft support structure according to an embodiment of the present invention, and is a cross-sectional view including gears. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a gear pump that employs a shaft support structure according to an embodiment of the present invention, and is a cross-sectional view including a shaft. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a gear pump that employs a shaft support structure according to an embodiment of the present invention, and is a cross-sectional view along a direction in which a shaft (shaft) extends. A specific operation sequence of the first hydrostatic bearing, the second hydrostatic bearing, the first hydrodynamic bearing, and the second hydrodynamic bearing in the gear pump employing the shaft support structure according to the embodiment of the present invention will be described. It is a figure for doing.

  Hereinafter, an embodiment of a shaft support structure according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

  1 and 2 are schematic views showing a schematic configuration of a gear pump that employs the shaft support structure of this embodiment, FIG. 1 is a sectional view including gears of the gear pump, and FIG. 2 is a shaft of the gear pump. 3 is a cross-sectional view including (shaft portion), and FIG. 3 is a cross-sectional view in a direction along the extending direction of the shaft portion of the gear pump.

  As shown in these drawings, the gear pump 1 includes a casing 2, a first gear 3, a second gear 4, a first shaft 5 (shaft portion), a second shaft 6 (shaft portion), and a shaft support. And a structure 7 (shaft support structure of the shaft portion).

The casing 2 is a housing that forms the outer shape of the gear pump 1, and accommodates the first gear 3, the second gear 4, the first shaft 5, and the second shaft 6 therein.
Further, the casing 2 is formed with two openings 21 and 22 connected to the accommodation space of the first gear 3 and the second gear 4. The opening 21 is used as a suction port for introducing fuel into the gear pump 1, and the opening 22 is used as a discharge port for discharging fuel from the gear pump 1.

The first gear 3 and the second gear 4 are arranged to mesh with each other inside the casing 2 and are rotated in reverse to each other.
The first gear 3 boosts the fuel supplied from the opening 21 between itself and the inner wall surface of the casing 2 and discharges the fuel through the opening 22. Similarly, the second gear 4 boosts the fuel supplied from the opening 21 between itself and the inner wall surface of the casing 2 and discharges the fuel through the opening 22.

The first shaft 5 is connected to the first gear 3, and transmits rotational power to the first gear 3 by being rotationally driven by a motor (not shown) or the like.
The second shaft 6 is connected to the second gear 4 and is rotationally driven by a motor or the like (not shown) to transmit the rotational power to the second gear 4.

The shaft support structure 7 includes a first hydrodynamic bearing 71 that supports the first shaft 5 with fuel (working fluid) interposed between the first shaft 5 and itself when the first shaft 5 rotates at a high speed, When the second shaft 6 rotates at a high speed, a second dynamic pressure bearing 72 is provided that supports the second shaft 6 with fuel (working fluid) interposed between the second shaft 6 and itself.
The first dynamic pressure bearing 71 is constituted by a part of the casing 2 that surrounds the first shaft 5. The second dynamic pressure bearing 72 is constituted by a part of the casing 2 surrounding the second shaft 6.

The shaft support structure 7 includes a first hydrostatic bearing 73 that ejects fuel (working fluid) toward the first shaft 5 and a second hydrostatic bearing 74 that ejects fuel toward the second shaft 6. I have.
Even if the first shaft 5 is rotating at a low speed such that the first dynamic pressure bearing 71 does not operate, the first hydrostatic bearing 73 is applied to the wall surface of the casing 2 of the first shaft 5 by the jetted fuel. The first shaft 5 is pivotally supported with low friction by suppressing contact.
Even if the second shaft 6 is rotating at a low speed such that the second dynamic pressure bearing 72 does not operate, the second hydrostatic bearing 74 is applied to the wall surface of the casing 2 of the second shaft 6 by the injected fuel. By suppressing the contact, the second shaft 6 is pivotally supported with low friction.

Further, the shaft support structure 7 includes a bypass passage 75 for supplying a part of the fuel discharged from the opening 22 of the casing 2 used as a discharge port to the first hydrostatic bearing 73 and the second hydrostatic bearing 74. And a check valve 76 (fuel supply restriction means) installed in the middle of the bypass flow path 75.
The check valve 76 is installed in the middle part of the bypass flow path 75, and fuel is supplied only from the opening 22 of the casing 2 used as a discharge port toward the first hydrostatic bearing 73 and the second hydrostatic bearing 74. It is a valve that passes through. In this embodiment, the check valve 76 is configured to be opened only when the pressure of the fuel discharged from the gear pump 1 is higher than the pressure required by the supply destination to which the fuel is supplied from the gear pump 1. .

When starting the gear pump 1 of this embodiment having such a configuration, the first gear 3 and the second gear 4 are rotationally driven by the motor (not shown) via the first shaft 5 and the second shaft 6. .
Thus, the fuel introduced into the gear pump 1 through the opening 21 of the casing 2 is pressurized by the rotation of the first gear 3 and the second gear 4 and discharged through the opening 22.
As a result, the fuel discharged from the gear pump 1 is gradually increased in pressure, and when this pressure exceeds the pressure required by the fuel supply destination of the gear pump 1, the check valve 76 installed in the bypass passage 75 opens. Then, fuel is supplied to the first hydrostatic bearing 73 and the second hydrostatic bearing 74, and the first hydrostatic bearing 73 and the second hydrostatic bearing 74 operate.
That is, in the shaft support structure 7 of the present embodiment, when the pressure of the fuel discharged from the gear pump 1 is equal to or lower than the pressure required by the supply destination, a part of the fuel discharged from the gear pump 1 is the first static pressure. Supply to the bearing 73 and the second hydrostatic bearing 74 is stopped.
Then, once the pressure of the fuel discharged from the gear pump 1 becomes equal to or higher than the pressure required by the supply destination, the first hydrostatic bearing 73 and the second hydrostatic bearing 74 operate as long as this pressure is maintained. Further, when the rotational speeds of the first shaft 5 and the second shaft 6 become high, the first dynamic pressure bearing 71 and the second dynamic pressure bearing 72 are operated.

Next, specific operation sequences of the first hydrostatic bearing 73, the second hydrostatic bearing 74, the first hydrodynamic bearing 71, and the second hydrodynamic bearing 72 will be described with reference to FIG.
In the following description, the case where the gear pump 1 of this embodiment is used as a fuel pump that supplies fuel to a jet engine will be described.
In FIG. 4, (a) shows the change in the output of the jet engine, (b) shows the change in the fuel pressure, and (c) shows the change in the load of the gear pump 1. In addition, the time axis in (a)-(c) is the same scale.

First, at the timing immediately after the jet engine is started by an air starter or the like, the fuel pressure and the load on the gear pump 1 are small, the check valve 76 is closed, and the fuel pressure increase speed is increased. In this case, only the first dynamic pressure bearing 71 and the second dynamic pressure bearing 72 are operating.
Subsequently, when the output of the jet engine becomes about 10 to 15%, the fuel pressure rises to become a pressure that can be supplied to the jet engine. At this timing, the check valve 76 is opened and the first hydrostatic bearing 73 is opened. And the 2nd hydrostatic bearing 74 act | operates.

According to the shaft support structure 7 of the present embodiment as described above, the fuel discharged from the gear pump 1 when the pressure of the fuel discharged from the gear pump 1 by the check valve 76 is equal to or lower than the pressure required by the supply destination. Is stopped from being supplied to the first hydrostatic bearing 73 and the second hydrostatic bearing 74.
For this reason, according to the shaft support structure 7 of the present embodiment, the gear pump 1 when the pressure of the fuel is increased by the gear pump 1 (that is, when the pressure of the fuel discharged from the gear pump 1 is equal to or lower than the pressure required by the supply destination). By stopping the supply of a part of the fuel discharged from the first hydrostatic bearing 73 and the second hydrostatic bearing 74, the apparent volumetric efficiency of the gear pump 1 at the time of starting is improved, and the fuel The boosting speed can be improved.
Therefore, when the gear pump 1 that employs the shaft support structure 7 of the present embodiment is employed in an aircraft, it is possible to shorten the engine start start time without installing a gear pump having a large output.

  As mentioned above, although preferred embodiment of the axial support structure of the axial part concerning this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

For example, in the said embodiment, the structure which uses the axial support structure of the axial part of this invention for a gear pump was demonstrated. That is, in the said embodiment, the structure which axially supports the axial part (1st shaft and 2nd shaft) connected with the gear with which a gear pump is equipped was demonstrated by the axial support structure of the axial part of this invention.
However, the present invention is not limited to this, and can be applied to a general shaft support structure for supplying a part of fuel discharged from a pump to a hydrostatic bearing.
The pump in the present invention is not limited to a gear pump.

Moreover, in the said embodiment, when the pressure of the fuel discharged from the gear pump 1 is below the pressure which a supply destination calculates | requires, a part of fuel discharged from the gear pump 1 is the 1st hydrostatic bearing 73 and 2nd. The configuration in which the supply to the hydrostatic bearing 74 is stopped has been described.
However, the present invention is not limited to this, and when the pressure of the fuel discharged from the gear pump 1 is equal to or lower than the pressure required by the supply destination, a part of the fuel discharged from the gear pump 1 is the first static pressure. The amount supplied to the pressure bearing 73 and the second hydrostatic bearing 74 may be reduced.
That is, in the present invention, when the pressure of the fuel discharged from the gear pump 1 is equal to or lower than the pressure required by the supply destination, a part of the fuel discharged from the gear pump 1 is transferred to the first hydrostatic bearing 73 and the second static pressure bearing 73. The supply to the pressure bearing 74 may be limited.

Moreover, in the said embodiment, the structure which uses the check valve 76 opened when the pressure of the fuel discharged from the gear pump 1 is higher than the pressure which a supply destination calculates | required was demonstrated as a fuel supply restriction | limiting means of this invention.
However, the present invention is not limited to this. For example, the fuel supply means measures the pressure of the fuel discharged from the gear pump 1, and opens and closes the bypass passage 75 according to the pressure of the pressure gauge. It is also possible to employ a configuration including an opening / closing device that performs the above.

Moreover, in the said embodiment, the structure provided with the dynamic pressure bearing (The 1st dynamic pressure bearing 71 and the 2nd dynamic pressure bearing 72) demonstrated the axial support structure of the axial part.
However, when the shaft portion does not rotate at a high speed, the support structure for the shaft portion does not necessarily include a dynamic pressure bearing.

  DESCRIPTION OF SYMBOLS 1 ... Gear pump, 2 ... Casing, 3 ... 1st gear (gear), 4 ... 2nd gear (gear), 5 ... 1st shaft (shaft part), 6 ... 2nd shaft (shaft part) ), 7... Shaft support structure, 71... 1st dynamic pressure bearing (dynamic pressure bearing), 72... 2nd dynamic pressure bearing (dynamic pressure bearing), 73. 74 ... second hydrostatic bearing (hydrostatic bearing), 75 ... bypass passage, 76 ... check valve (fuel supply limiting means)

Claims (5)

A shaft support structure comprising a hydrostatic bearing that supplies a part of the fuel discharged from a pump to a supply destination and ejects the supplied fuel to support the shaft,
A shaft of a shaft portion comprising fuel supply restriction means capable of restricting the supply of fuel to the hydrostatic bearing when the pressure of fuel discharged from the pump is equal to or lower than the pressure required by the supply destination Support structure.   2. The fuel supply limiting means stops fuel supply to the hydrostatic bearing when the pressure of fuel discharged from the pump is equal to or lower than a pressure required by the supply destination. The shaft support structure of the shaft part.   3. The shaft support structure according to claim 2, wherein the fuel supply limiting means is a check valve that opens when the pressure of the fuel discharged from the pump is higher than the pressure required by the supply destination. .   The pump is a gear pump including a gear for boosting the fuel and a shaft connected to the gear, and the shaft supported by the hydrostatic bearing is a shaft connected to the gear. The shaft support structure of the shaft part according to any one of claims 1 to 3.   The shaft support structure according to claim 1, further comprising a hydrodynamic bearing that supports the shaft.

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