JP6193068B2 - Double-rotating double internal gear pump - Google Patents

Description

  The present invention includes first and second inner gears that are rotatably integrated with a drive shaft that can be driven in both directions, and the first and second inner gears so as to mesh with a part of the circumferential direction of the first and second inner gears, respectively. The present invention relates to a double-rotating double internal gear pump in which outer gears are respectively arranged.

  Conventionally, as in a variable displacement gear pump of Patent Document 1, for example, a main gear pump portion having a main drive gear and a main driven gear that mesh with each other, a sub gear pump portion having a sub drive gear and a sub driven gear that mesh with each other, To the suction flow passage communicating with each suction side space portion of the gear pump portion and the sub gear pump portion, the discharge flow passage communicating with each discharge side space portion of the main gear pump portion and the sub gear pump portion, and the discharge side space portion of the sub gear pump portion A bypass flow path for returning discharged hydraulic oil to the intake flow path, and a check valve for preventing the hydraulic oil discharged to the discharge side space of the main gear pump section from flowing into the discharge side space of the sub gear pump section; A variable displacement gear pump having an open / close valve that opens and closes a bypass flow path is known. In this variable displacement gear pump, a low capacity operation that supplies only the hydraulic oil discharged from the main gear pump section, and a high capacity that discharges the hydraulic oil discharged from the sub gear pump section in addition to the hydraulic oil discharged from the main gear pump section. The operation can be switched. In this variable displacement gear pump, the discharge amount can be adjusted depending on the pressure difference between loading and non-loading without a solenoid valve, but the maximum working pressure is determined by the discharge pressure of the main gear pump or sub gear pump itself. Therefore, when a low discharge pressure is sufficient, the operation becomes a low level and waste occurs.

  Further, as in Patent Document 2, for example, there is known a double gear pump that houses a drive gear and two driven gears that mesh with the drive gear in a casing and operates as a two-system pump. This double gear pump is provided with an unload flow path for connecting the discharge side of the pump of one system to the suction side of the pump, and provided with valve means for opening and closing the unload flow path. In this double gear pump, according to the pressure on the discharge side, the discharge capacity is increased at low pressure and the discharge capacity is decreased at high pressure. However, a differential pressure valve and a flow path connected to the differential pressure valve must be provided, and a compact structure cannot be obtained.

  On the other hand, there is known a low pressure / high pressure switching pump disclosed in Patent Document 3 in which two internal gear devices having the same discharge amount and an electromagnetic direction switching valve are connected and assembled. In this low-pressure switching pump, a compact structure is realized by integrally providing an electromagnetic direction switching valve and a flow path connected thereto.

  As disclosed in Patent Document 4, a check valve for a reversible hydraulic pump that adjusts excess or deficiency of hydraulic oil in a hydraulic circuit is known. Further, as in Patent Document 5, an independent internal gear pump for both rotations using a backflow prevention valve is known.

JP 2009-191754 A JP 2002-70757 A (particularly FIG. 6) Japanese Utility Model Publication No. 55-172684 (particularly FIGS. 1 and 3) Japanese Utility Model Publication No. 54-43602 (especially FIG. 2) JP 2004-308547 A

  However, in the gear pumps of Patent Documents 1 to 3, it is not considered to rotate the drive shaft in both directions. A single internal gear pump as disclosed in Patent Document 5 is configured to be capable of rotating in both directions. However, when a dual gear pump is used, a switching valve and a flow path are integrally formed as shown schematically in FIG. It is not easy to provide.

  The present invention has been made in view of such a point, and an object of the present invention is to obtain a double-rotating double internal gear pump capable of switching between low and high pressure with a compact structure.

  In order to achieve the above object, in the present invention, the switching valve and the flow path are integrally provided in the middle flange between the pair of pumps.

Specifically, in the first invention, the first and second inner gears that are rotatably integrated with the drive shaft that can be driven in both directions;
It is premised on a double-rotating double internal gear pump in which first and second outer gears are respectively arranged so as to mesh with part of the first and second inner gears in the circumferential direction.

And the above-mentioned double-rotating double internal gear pump is
A middle flange is disposed between the first pump constituted by the first inner gear and the first outer gear and the second pump constituted by the second inner gear and the second outer gear,
The middle flange
A first discharge suction port and a second discharge suction port for taking in and out the hydraulic oil in the middle flange;
Low pressure and large flow rate operation that combines the hydraulic oil discharged from the first pump and the hydraulic oil discharged from the second pump, and the hydraulic oil discharged from the first pump to the suction side of the second pump A switching valve for switching between high pressure and low flow operation for further boosting by the second pump;
An excess / deficiency adjustment valve that adjusts excess / deficiency of hydraulic fluid between the first discharge suction port and the second discharge suction port;
A flow path connecting the excess / deficiency adjustment valve and the switching valve is provided ,
The switching valve is configured to be able to switch between the low pressure and large flow rate operation and the high pressure and small flow rate operation only during normal rotation of the first pump and the second pump .

According to the above configuration, the hydraulic oil discharged from the first pump is reduced in the high pressure and low flow rate operation compared to the low pressure and high flow rate operation in which the hydraulic oil discharged from the respective pumps during the forward rotation of the first pump and the second pump is added. Since two-stage boosting is performed by leading to the suction side of the two pumps and further boosting by the second pump, the pressure difference necessary for boosting to the maximum operating pressure is equally shared between the first pump and the second pump. As a result, the amount of leakage that increases with the pressure difference can be reduced as much as possible. Thereby, not only the discharge amount is halved in order to match the required discharge flow rate, but also the volumetric efficiency is improved at the same time, so no waste occurs. In addition, an excess / deficiency adjustment valve and switching valve for adjusting excess / deficiency of hydraulic fluid in the hydraulic system are provided in the middle flange, so there is no need to connect hydraulic piping and secure installation space. . Therefore, the structure is compact and easy to maintain.

In the second invention, in the first invention,
A tank port is formed in the middle flange, and the switching valve and the excess / deficiency adjustment valve can communicate with the tank port in the middle flange.
In the low pressure and large flow rate operation, the ratio of the flow rate of the first discharge suction port to the flow rate of the second discharge suction port is 2: 1, and the hydraulic oil is replenished from the tank without passing through the excess / deficiency adjustment valve. Configured as possible,
In the high pressure and small flow rate operation, only the internal leak can be supplemented by the excess / deficiency adjustment valve.

  According to the above configuration, particularly in the case of a hydraulic system that expands and contracts a cylinder with an area ratio of 2: 1 between the head side and the rod side, it is not necessary to go through an excess / deficiency adjustment valve during low pressure and large flow rate operation in the middle flange. Since the shortage of hydraulic oil can be replenished from the tank, the size of the excess / deficiency adjustment valve can be reduced, and the arrangement in the middle flange becomes much easier.

In the third invention, in the first or second invention,
A tank port is formed in the middle flange so that the first pump and the second pump communicate with the first discharge suction port, the second discharge suction port or the tank port via the middle flange. It has become.

  According to said structure, since the port for connecting with the exterior is gathering in the middle flange, it is not necessary to provide an outer case like patent document 3, and piping is very easy.

In a fourth invention, in any one of the first to third inventions,
The switching valve is a spool valve built in the middle flange, and by operating the hydraulic oil from the second pump through a pilot flow path formed in the middle flange, the first pump and The low-pressure large-flow operation and the high-pressure small-flow operation can be switched only during the forward rotation of the second pump .

  According to the above configuration, there is no need to provide a hydraulic sensor or a solenoid valve for operation switching, the structure is further simplified, and no special control for switching is required.

As described above, according to the present invention, the switching valve for switching between the low pressure and large flow rate operation and the high pressure and small flow rate operation is adjusted to the middle flange only during the normal rotation of the first pump and the second pump. By incorporating the excess / deficiency adjusting valve and the flow path, it is possible to easily install the double-rotating double internal gear pump capable of switching between low and high pressure with a compact structure.

It is the schematic which shows the hydraulic system which has the both rotation type | mold double inscribed gear pump which concerns on Embodiment 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a hydraulic circuit diagram showing a hydraulic system having a double-rotating double internal gear pump according to a first embodiment of the present invention. It is sectional drawing which shows the double rotation type | mold double inscribed gear pump which concerns on Embodiment 1 of this invention. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3, and is a perspective view taken along line IV-IV showing details of each member / flow path in order to grasp the structural layout of the middle flange portion. It is sectional drawing which expands and shows a lubrication mechanism. FIG. 2 is a view corresponding to FIG. 1 and illustrating a flow of hydraulic oil during low-pressure and large-flow operation. FIG. 2 is a view corresponding to FIG. FIG. 7 is a view corresponding to FIG. 6 illustrating a hydraulic system having a double-rotating double internal gear pump according to a second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows an outline of a hydraulic system 2 having a double rotation internal gear pump 1 (hereinafter referred to as a dual internal gear pump 1) according to Embodiment 1 of the present invention. FIG. 2 is a hydraulic circuit diagram of the hydraulic system 2. This double internal gear pump 1 has a drive shaft 3 that can be driven in both directions, and this drive shaft 3 is connected to, for example, an electric motor 4. Although not described in detail, the electric motor 4 is not particularly limited, such as a servo motor, and can freely control the rotational speed, the rotational torque, and the like. The dual internal gear pump 1 has a first discharge suction port A, a second discharge suction port B, and a tank port T in a middle flange 12 to be described later, and the first discharge suction port A is a head of the hydraulic cylinder 5 by hydraulic piping. The second discharge suction port B is connected to the rod side of the hydraulic cylinder 5. A tank port T is connected to the oil tank 15. In this embodiment, for example, the hydraulic cylinder 5 is a press cylinder of a press machine, and the ratio of the area of the head side of the hydraulic cylinder 5 to the area of the rod side is 2: 1.

  As shown in FIGS. 3 and 4, the dual internal gear pump 1 includes first and second inner gears 6, 7 that are provided on a single drive shaft 3 so as to be integrally rotated by key connection or the like. The first and second pump casings 10a are partially engaged with each of the first and second inner gears 6 and 7 in a circumferential direction with the first and second outer gears 8 and 9 meshing with each other in an eccentric manner. , 11a are incorporated in the gear housing spaces 10b, 11b. The first inner gear 6, the first outer gear 8, and the first pump casing 10a constitute the first pump 10, and the second inner gear 7, the second outer gear 9, and the second pump casing 11a constitute the second pump 11. Has been. In the present embodiment, the first pump 10 and the second pump 11 have the same discharge amount. Pump ports P1A and P1B are formed in the first pump casing 10a of the first pump 10, and pump ports P2A and P2B are formed in the second pump casing 11a of the second pump 11. These pump ports P1A, P1B, P2A, and P2B communicate with corresponding ports of the middle flange 12 disposed between the first pump 10 and the second pump 11.

  The middle flange 12 includes a spool valve 13 as a switching valve. The spool valve 13 has pump ports P1A, P1B, P2A, and P2B that communicate with the pump ports P1A, P1B, P2A, and P2B of the first pump 10 and the second pump 11 by a flow path formed in the middle flange 12, respectively. doing. In addition, the spool valve 13 has ports A, B, and T that communicate with the hydraulic cylinder 5 and the oil tank 15, respectively, through a flow path formed in the middle flange 12. Further, in the middle flange 12, as shown in FIG. 1, a pilot flow path 13a communicating with the pump port P2A of the second pump 11 is formed. When a pressure is generated in the pilot flow path 13a that pushes the spring 13b of the spool valve 13, the spool valve 13 moves. Thus, the spool valve 13 causes the hydraulic oil discharged from the first pump 10 and the hydraulic oil discharged from the second pump 11 to merge, and the hydraulic oil discharged from the first pump 10 It is configured to switch between high pressure and low flow rate operation that is led to the suction side of the two pumps 11 and further boosted by the second pump 11.

  Further, the middle flange 12 is formed with a first discharge suction port A and a second discharge suction port B, and an excess of hydraulic oil between the first discharge suction port A and the second discharge suction port B is formed. An excess / deficiency adjustment valve 14 for adjusting the deficiency is incorporated. Furthermore, a flow path that connects the excess / deficiency adjustment valve 14 and the spool valve 13 is formed in the middle flange 12.

  As shown in FIG. 3, in the first pump casing 10a, a pair of lubrication mechanisms 21A and 21B are provided on the outer peripheral side of the first outer gear 8 in order to prevent seizure of the sliding portion of the first outer gear 8. Is located. The pair of lubrication mechanisms 21A and 21B are in symmetrical positions with the circular gear housing space 10b interposed therebetween, and correspond to the pump ports P1A and P1B, respectively. Similarly, in the second pump casing 11a, a set of lubrication mechanisms 22A and 22B are provided on the outer peripheral side of the second outer gear 9 in order to prevent the sliding contact portion of the second outer gear 9 from being seized. It has been. The pair of lubrication mechanisms 22A and 22B are in symmetrical positions with the circular gear housing space 11b interposed therebetween, and correspond to the pump ports P2A and P2B, respectively. Since the structures of the lubrication mechanisms 21A, 21B, 22A, and 22B are substantially the same, the structure of the lubrication mechanism 21A corresponding to the pump port P1A will be described in detail.

  As shown in FIGS. 3 and 5, the lubrication mechanism 21 </ b> A is provided in the flow path 23, and a narrow flow-dividing flow path 23 that connects the sliding contact portion of the outer peripheral surface of the first outer gear 8 and the pump port P <b> 1 </ b> A. And a backflow prevention valve 24. The flow path 23 includes an axial first straight portion 23a provided on the outer peripheral side of the gear housing space 10b, an inclined portion 23b extending obliquely from the first straight portion 23a toward the gear housing space 10b, and a first straight line. The second straight portion 23c in the radial direction intersecting the portion 23a at a right angle and the third straight portion 23d in the axial direction extending from the second straight portion 23c toward the gear housing space 10b. Opening is made on the peripheral surface of the gear housing space 10 b facing the outer peripheral surface of the one outer gear 8. The other end of the flow path 23 opens at a position facing the pump port P1A on the end face of the middle flange 12 surrounding the gear housing space 10b. The plug 25 plays a role of closing one end of the first straight portion 23a.

  The backflow prevention valve 24 is a check valve disposed in the first straight portion 23a, and is configured to press the ball 24b toward the port side with a slight pressure by the spring 24a and press it against the seat portion. With this configuration, when the pump port P1A is positive pressure (strictly, when the pump port P1A is equal to or higher than the operating pressure of the backflow prevention valve 24), that is, in the discharge state, the backflow prevention valve 24 is opened, and the inside of the flow path 23 passes through the pump port P1A. The working fluid flows from the first side to the outer peripheral surface side of the first outer gear 8. When the pump port P1A has a negative pressure (strictly, when the pump port P1A is less than the operating pressure of the backflow prevention valve 24), that is, in the suction state, the backflow prevention valve 24 is closed and the inside of the flow path 23 is surrounded by the outer periphery of the first outer gear 8. The backflow of the working fluid from the surface side to the pump port P1A side is prevented. And, by the action of the backflow prevention valve 24 of the lubrication mechanisms 21A, 21B, 22A, 22B, the lubricating oil is not deficient even if the drive shaft 3 is rotated in both directions. Also, since these lubrication mechanisms 21A, 21B, 22A, 22B are compactly incorporated in the first and second pump casings 10a, 11a, separate components are added to the dual internal gear pump 1 for both rotations. There is no need to install or connect special piping, and a very compact structure is realized.

  Next, the operation of the dual internal gear pump 1 according to this embodiment will be described.

  FIG. 6 shows the flow of hydraulic oil during low pressure and high flow rate operation. When the hydraulic cylinder 5 is extended, it is necessary to extend it at a high speed, and usually a load is not often applied, and a low pressure and large flow rate operation is suitable. At this time, the reaction force of the hydraulic cylinder 5 is small, no pressure is generated in the pilot flow path 13a to overcome the spring 13b, and the spool valve 13 is in the neutral position.

  The drive shaft 3 rotates forward according to the rotation speed and rotation direction of the electric motor 4. Thereby, the 1st and 2nd pumps 10 and 11 rotate forward at the same rotation speed, and each discharge the hydraulic fluid of the same discharge amount Q.

  The hydraulic oil discharged from the first and second pumps 10 and 11 enters the middle flange 12 from the pump ports P1A and P2A, is discharged from the first discharge suction port A through the spool valve 13, and the hydraulic cylinder 5 2Q hydraulic oil is supplied to the head side and the rod extends.

  Since the area on the rod side is 1/2 of that on the head side, Q hydraulic oil is pushed out from the rod side, returns to the second discharge suction port B of the middle flange 12, and is supplied to the pump port P1B of the first pump 10. Is done. Since the first and second pumps 10 and 11 discharge a total of 2Q of hydraulic oil, the hydraulic oil Q is insufficient, so the hydraulic oil is replenished from the oil tank 15 through the tank port T of the middle flange 12. And supplied to the pump port P2B of the second pump 11 through the spool valve 13. At this time, since the hydraulic oil replenished from the oil tank 15 does not pass through the excess / deficiency adjustment valve 14, the excess / deficiency adjustment valve 14 does not need to pass a large volume of hydraulic oil, and its size can be reduced. it can. This is useful for making the middle flange 12 compact.

  As shown in FIG. 7, when the rod of the hydraulic cylinder 5 expands and comes into contact with the workpiece W to be pressed, for example, the pressure on the head side of the hydraulic cylinder 5 increases. This state is maintained for a predetermined time.

  Then, the pressure in the pilot flow path 13a also rises and the spool valve 13 moves to the left side of FIG. 7 so as to push and shrink the spring 13b, and the flow of hydraulic oil is automatically switched to the high pressure and low flow rate operation.

  That is, the hydraulic oil from the first pump 10 is supplied from the pump port P1A through the spool valve 13 in the middle flange 12 to the pump port P2B of the second pump 11, and is further pressurized by the second pump 11 to be middle flange. 12 is supplied to the pump port P2A of 12 and supplied from the first discharge suction port A to the head side of the hydraulic cylinder 5 through the spool valve 13, and the workpiece W is pressed at a high pressure increased by two stages. At this time, since the rod is not substantially extended, the return amount of the hydraulic oil from the rod side of the hydraulic cylinder 5 is substantially zero. If there is leakage of hydraulic oil in the first and second pumps 10, 11, etc., as shown by the broken line in FIG. 7, the hydraulic oil is replenished by that amount from the excess / deficiency adjustment valve 14, and the middle from the second discharge suction port B It is supplied to the pump port P1B of the first pump 10 through the spool valve 13 in the flange 12. This high pressure and small flow rate operation is terminated by stopping the electric motor 4.

  On the other hand, if the electric motor 4 is rotated reversely after maintaining the hydraulic cylinder 5 for a predetermined time, the flow of hydraulic oil is reversed. In the present embodiment, since the first and second pumps 10 and 11 are provided with the lubrication mechanisms 21A, 21B, 22A, and 22B, the lubricating oil is not insufficient even when the first and second pumps 10 and 11 are rotated in the reverse direction. , 11 can be prevented from seizing.

  In the present embodiment, the spool valve 13 is thus built in the middle flange 12, and the hydraulic oil from the second pump 11 is operated via the pilot flow path 13 a formed in the middle flange 12. Since it is possible to switch between large flow operation and high pressure small flow operation, it is not necessary to provide a hydraulic sensor or solenoid valve for operation switching, the structure is further simplified, and special control for switching is required. And not.

Further, in the high pressure and small flow rate operation, since the hydraulic oil discharged from the first pump 10 is led to the suction side of the second pump 11 and further boosted by the second pump 11, the pressure is increased to the maximum working pressure. Therefore, the pressure difference required to do so is equally shared between the first pump and the second pump, and the amount of leakage that increases with the pressure difference can be reduced as much as possible. Thereby, not only the discharge amount is halved in order to match the required discharge flow rate, but also the volumetric efficiency is improved at the same time, so no waste occurs.

  Further, a tank port T is formed in the middle flange 12, and the first pump 10 and the second pump 11 communicate with the first discharge suction port A, the second discharge suction port B, or the tank port T through the middle flange 12. Therefore, the ports for connecting to the outside gather at the middle flange 12 so that piping is very easy.

  Furthermore, in the hydraulic system 2 that expands and contracts the hydraulic cylinder 5 such that the area ratio between the head side and the rod side is 2: 1 as in the present embodiment, the oil does not go through the excess / deficiency adjustment valve 14 during low pressure and large flow rate operation. Since the shortage of hydraulic oil can be replenished from the tank 15, the size of the excess / deficiency adjustment valve 14 can be reduced, and the arrangement in the middle flange 12 becomes much easier.

  Therefore, in the present embodiment, the dual internal gear pump 1 capable of switching between low and high pressure can be easily installed with a compact structure.

(Embodiment 2)
FIG. 8 shows a second embodiment of the present invention, which differs from the first embodiment in that the configuration of the excess / deficiency adjustment valve 14 ′ is different. In the present embodiment, the same portions as those in FIGS. 1 to 7 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the tank port T is not communicated with the spool valve 13 in the middle flange 12 and is connected only to the excess / deficiency adjustment valve 14 ′.

  For this reason, as shown in FIG. 8, the shortage of hydraulic oil on the head side and the rod side of the hydraulic cylinder 5 is supplied via the excess / deficiency adjustment valve 14 in the low pressure and large flow rate operation. For this reason, the excess / deficiency adjustment valve 14 ′ cannot be downsized as in the first embodiment.

  When the volume ratio between the head side and the rod side of the hydraulic cylinder 5 is not 2: 1, the application of this embodiment is advantageous.

  In this embodiment, the size of the excess / deficiency adjustment valve 14 ′ is larger than that of the first embodiment, but the spool valve 13, the excess / deficiency adjustment valve 14 ′ and the flow path are provided in the middle flange 12 as in the first embodiment. Since it is formed, it does not require separate hydraulic piping and has a compact structure.

(Other embodiments)
The present invention may be configured as follows for each of the above embodiments.

  That is, in each of the above embodiments, the spool valve 13 is automatically operated using the pilot flow path 13a. However, instead of the spool valve 13, an electromagnetic valve is provided in the middle flange 12, and a pressure sensor is provided. Alternatively, the high pressure small flow operation and the low pressure large flow operation may be switched by electronic control using a time switch or the like.

  In each of the above embodiments, the hydraulic cylinder 5 of the press machine has been described as an example. However, the present invention is not limited to this, and is applicable to any hydraulic system that requires switching between a high pressure small flow operation and a low pressure large flow operation. .

  In the above embodiment, hydraulic oil is described as an example of the fluid. However, a dual internal gear pump that circulates other fluid such as water may be used.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or a use.

  As described above, according to the present invention, the first and second inner gears, which are rotatably integrated with the drive shaft which can be driven in both directions, and the circumferential portions of the first and second inner gears respectively mesh with each other. This is useful for a double rotation internal gear pump in which the first and second outer gears are respectively disposed.

1 Double inscribed gear pump (Double-rotating double inscribed gear pump)
2 hydraulic system 3 drive shaft 4 electric motor 5 hydraulic cylinder 6 first inner gear 7 second inner gear 8 first outer gear 9 second outer gear 10 first pump 10a first pump casing 10b gear housing space 11 second pump 11a Second pump casing 11b Gear housing space 12 Middle flange 13 Spool valve 13a Pilot flow path 13b Spring 14, 14 'Excess / deficiency adjustment valve 15 Oil tank 21A, 21B, 22A, 22B Lubrication mechanism 23 Flow path 23a First linear portion 23b Inclination Part 23c second straight part 23d third straight part 24 backflow prevention valve 24a spring 24b ball 25 plug P1A, P1B, P2A, P2B (pump) port T (tank) port A first discharge suction port B second discharge suction port

Claims (4)

First and second inner gears that are rotatably integrated with a drive shaft that can be driven in both directions;
In the double rotary internal gear pump in which the first and second outer gears are respectively arranged so as to mesh with a part of the circumferential direction of the first and second inner gears,
A middle flange is disposed between the first pump constituted by the first inner gear and the first outer gear and the second pump constituted by the second inner gear and the second outer gear,
The middle flange
A first discharge suction port and a second discharge suction port for taking in and out the hydraulic oil in the middle flange;
Low pressure and large flow rate operation that combines the hydraulic oil discharged from the first pump and the hydraulic oil discharged from the second pump, and the hydraulic oil discharged from the first pump to the suction side of the second pump A switching valve for switching between high pressure and low flow operation for further boosting by the second pump;
An excess / deficiency adjustment valve that adjusts excess / deficiency of hydraulic fluid between the first discharge suction port and the second discharge suction port;
A flow path connecting the excess / deficiency adjustment valve and the switching valve is provided ,
The double-rotation type dual-linkage characterized in that the switching valve is configured to be able to switch between the low-pressure and large-flow operation and the high-pressure and small-flow operation only when the first pump and the second pump are rotating forward . Contact gear pump. In the double rotation internal gear pump according to claim 1,
A tank port is formed in the middle flange, and the switching valve and the excess / deficiency adjustment valve can communicate with the tank port in the middle flange.
In the low pressure and large flow rate operation, the ratio of the flow rate of the first discharge suction port to the flow rate of the second discharge suction port is 2: 1, and the hydraulic oil is replenished from the tank without passing through the excess / deficiency adjustment valve. Configured as possible,
A double-rotating double internal gear pump characterized in that, in the high-pressure and small-flow operation, only an internal leak can be replenished by the excess / deficiency adjustment valve. The double-rotating double internal gear pump according to claim 1 or 2,
A tank port is formed in the middle flange so that the first pump and the second pump communicate with the first discharge suction port, the second discharge suction port or the tank port via the middle flange. A double-rotating double internal gear pump characterized by The double-rotating double internal gear pump according to any one of claims 1 to 3,
The switching valve is a spool valve built in the middle flange, and by operating the hydraulic oil from the second pump through a pilot flow path formed in the middle flange, the first pump and A double-rotating double internal gear pump characterized in that the low-pressure large-flow operation and the high-pressure small-flow operation can be switched only when the second pump rotates forward .

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