JP5695995B2 - Gear pump - Google Patents

Description

  The present invention relates to a gear pump for delivering a working fluid such as a medium that is circulated and used in a binary power generation device, for example.

  In recent years, from the viewpoint of energy saving, there is an increasing need for a power generation apparatus that recovers so-called exhaust heat discharged from various facilities such as factories and generates power using the energy contained in the recovered exhaust heat. .

  As the power generation device, a binary power generation device has been proposed (see, for example, Patent Document 1). This binary power generation apparatus includes an evaporator that evaporates a medium by heat of a heat source fluid, a screw turbine that drives the generator by expanding the vapor of the medium, and a condenser that condenses the vapor of the medium discharged from the screw turbine. And a circulation pump that circulates the medium and a circulation channel that is connected in series to form a closed loop, and is configured to generate power by driving the generator with the screw turbine.

  As the circulation pump, various types are applicable, but so-called gear pumps are generally used.

  As a gear pump, the thing shown in FIG.10 and FIG.11 is known, for example (for example, refer patent document 2). In this gear pump, a pair of side plates 112 are fitted into opposing portions of a cavity inside the housing 101 to define a gear chamber 114, and a pair of gears 103 and 104 each consisting of a spur gear are provided inside the gear chamber 114. Furthermore, the shafts 130 and 140 of the gears 103 and 104 are fitted and supported by the support holes 131 and 141 formed in the corresponding side plates 112, and are accommodated in the gear chamber 114. The medium suction chamber 105 and the discharge chamber 106 are formed with the meshing positions of the gears 103 and 104 interposed therebetween.

  For the housing 101 and the side plate 112, an aluminum alloy is used for improving workability and reducing the weight, while the gears 103 and 104 are required to have wear resistance. System materials are used.

Japanese Patent Laid-Open No. 10-103030 JP-A-10-141246

  By the way, if the liquid delivered by the gear pump having such a configuration is a highly viscous oil having a viscosity of, for example, about 32 cSt, the lubricity is good, and wear can be sufficiently suppressed by using the above-described cast iron or the like for each gear. be able to.

  However, when the working liquid delivered by the gear pump is a medium such as R245fa used in a binary power generator, for example, the viscosity is much lower than that of oil having the above-mentioned viscosity of about 32 cSt. The viscosity is much lower than oil of about 32 cSt. Therefore, there is a possibility that the wear cannot be sufficiently prevented only by using a cast iron or the like for each gear.

  The present invention has been made to solve the above-described problems of the prior art, and provides a gear pump capable of suppressing the occurrence of wear even when a working fluid having a low viscosity is used. Objective.

The gear pump of the present invention is a gear pump including a drive rotor and a driven rotor that are housed in a casing in mesh with each other, and the teeth of the drive rotor are included in the teeth of the driven rotor. In addition to the two positions after the movement, in addition to the two positions moved in accordance with the rotation, the initial meshing attitude in contact with two positions separated from each other and the attitude rotated from the initial meshing attitude. There is a three-point meshing posture in which the teeth of the drive rotor come into contact with the teeth of the driven rotor at one position on the upstream side in the rotational direction, and the downstream side between the two positions on the downstream side in the rotational direction in the three-point meshing posture The pressure in the space is higher than the pressure in the upstream space between the two positions upstream in the rotational direction, and the perpendicular bisector connecting the two positions downstream in the rotational direction is the driven As causes rotation direction of the moment over data, wherein are offset from the axis of the driven rotor, inside the casing, the discharge chamber is provided for the working fluid, at least one of the driving rotor and the driven rotor A first groove communicating with the downstream space is formed on the rotor end surface, and a surface of the casing facing the rotor end surface having the first groove is formed on the surface of the casing in the three-point meshing posture. A second groove that communicates with the chamber is formed .

In the case of this invention, in the three-point meshing posture, the pressure in the downstream space between the two positions downstream in the rotational direction is higher than the pressure in the upstream space between the two positions upstream in the rotational direction. Therefore, the pressure in the upstream space does not affect the rotational direction of the driven rotor so much, and the vertical line segment connecting the two positions downstream of the rotational direction generates a moment in the rotational direction of the driven rotor. The equipartition line is offset from the axis of the driven rotor. For this reason, it is possible to rotate the driven rotor in an idle state in the three-point meshing posture. Thereby, even when a working fluid having a low viscosity is used, it is possible to suppress the occurrence of wear.
In addition, as described above, a first groove communicating with the downstream space is formed on at least one rotor end surface of the drive rotor and the driven rotor, and the surface of the casing facing the rotor end surface having the first groove. Is formed with a second groove that allows the first groove and the discharge chamber to communicate with each other in the three-point engagement posture. In this configuration, even after the downstream space is formed, even if the volume of the downstream space gradually decreases, the discharge chamber communicates with the downstream space via the first groove and the second groove. Therefore, the working fluid accommodated in the downstream space can be released to the discharge chamber, thereby preventing the gear pump from being damaged.

  In the gear pump having this configuration, it is preferable that the upstream space has a volume formed from zero when changing from the initial meshing posture to the three-point meshing posture. In such a case, it is possible to prevent the driven rotor from being affected at all, so that the driven rotor can be more reliably rotated in the idling state in the three-point meshing posture.

  In the gear pump of this configuration, the tooth shape of the drive rotor has two different shapes, the rotational direction side tooth surface (X) and the counter rotation direction side tooth surface (Y) across the tooth tip, When the rotation direction side tooth surface (X) is defined as the first function (H), the tooth surface of the driven rotor facing the tooth surface of the driven rotor is the generating function of the first function (H) when the drive rotor rotates in the counter rotation direction. In the counter rotation direction side tooth surface (Y), the tooth tip side portion of the counter rotation direction side tooth surface (Y) is defined as the third function (F). Then, the tooth surface of the driven rotor is defined by a fourth function (f) that is a generating function of the third function (F) when the driving rotor rotates in the counter-rotating direction, and the fourth function (f ) To the predetermined position in the pitch circle of the driven rotor. The fifth function (g) connected to the number (f) defines the tooth tip of the driven rotor, and is a generating function of the fifth function (g) when the drive rotor is rotated in the rotation direction. The counter-rotation direction side tooth surface (Y) may be defined in a state where the function (G) follows the portion defined by the third function (F). In this case, the tooth shape of the drive rotor is defined by the first function (H), the third function (F), and the sixth function (G), and the tooth shape of one driven rotor is the second function (h ), The shapes of the teeth of the drive rotor and the driven rotor are designed so that the drive rotor and the driven rotor are meshed in the three-point meshing posture by being defined by the fourth function (f) and the fifth function (g). The

In the gear pump of this configuration, each tooth of the driving rotor and each tooth of the driven rotor are twisted with respect to the respective rotor shaft centers, and the downstream space is connected to the discharge chamber by the twisting . You may make it the structure closed with respect to the said suction chamber by the part which a tooth | gear and the tooth | gear of a driven rotor contact | adhere . In this case, the teeth of the drive rotor and the driven rotor are twisted with respect to the respective rotor shaft centers, so that the positions where the teeth of the drive rotor and the teeth of the driven rotor mesh with each other as the rotor rotates. The working fluid accommodated in the downstream space is moved by the movement of the meshing position, and the working fluid is allowed to escape to the discharge chamber. This also prevents the gear pump from being damaged.

  In the case of the present invention, since the driven rotor can be rotated in the idle state in the three-point meshing posture, the occurrence of wear can be suppressed even when a working fluid having a low viscosity is used. A possible gear pump can be provided.

It is a top view showing a gear pump concerning one embodiment of the present invention. It is a left view which shows the drive rotor and driven rotor which comprise the gear pump of FIG. (A) shows a state in which the driving rotor and the driven rotor are engaged in the first posture, (b) shows a state in which the driving rotor is engaged in the second posture, and (c) shows a state in which the driving rotor and the driven rotor are also engaged in the third posture. . It is explanatory drawing for designing the tooth surface shape of the drive rotor and driven rotor which are used by this invention. It is a figure which shows the direction of the perpendicular bisector of the line segment of the contact position power and the contact position key in the three-point meshing posture. It is a figure which shows the relationship between a rotor rotation angle (horizontal axis) and a torque (vertical axis). It is explanatory drawing of the formation process of upstream space. It is explanatory drawing of the twist of the tooth | gear of the drive rotor of this invention, and a driven rotor. It is a figure for demonstrating the relationship between the 1st groove | channel and 2nd groove | channel used by this invention. It is a front view which shows the conventional gear pump. It is a side view (sectional drawing) of the gear pump of FIG.

  Embodiments of the present invention will be specifically described below.

  FIG. 1 is a plan view showing a gear pump according to this embodiment, and FIG. 2 is a left side view showing a drive rotor and a driven rotor constituting the gear pump.

  The gear pump 1 is stored in a storage chamber 5 provided inside the casing 3 in a state where the drive rotor 7 and the driven rotor 9 are engaged with each other. The casing 3 includes a first casing 3a having a storage chamber 5 on one end side, a second casing 3b that is abutted against one end of the first casing 3a, and a first lid 3c that is abutted against the other end of the first casing 3a. And a second lid portion 3d that is abutted against the end surface opposite to the end surface that abuts the first casing 3a of the second casing 3b. The first lid portion 3 c and the second lid portion 3 d have a two-part structure corresponding to each axis of the drive rotor 7 and the driven rotor 9.

  The shaft portion 7 a of the drive rotor 7 is connected to a motor (not shown), is driven to rotate by the motor, and the rotation is transmitted to the driven rotor 9. The casing 3 is provided with a suction chamber 15 on one side and a discharge chamber 17 on the other side across a portion where the drive rotor 7 and the driven rotor 9 mesh with each other. 17 communicates with the storage chamber 5. Note that 9 a in FIG. 1 is a shaft portion of the driven rotor 9.

  The driving rotor 7 has a plurality of teeth, 10 teeth 7b in the illustrated example, while the driven rotor 9 has a plurality of teeth, 12 teeth 9b in the illustrated example. The shape of the teeth 7b is a shape that bulges outward on the outside of the pitch circle 7p of the drive rotor 7, and the shape of the root portion of the teeth 7b is such that the concave bottom portion of the root portion is the shape of the drive rotor 7. It is a hollow shape located inside the pitch circle 7p. The shape of the one tooth 9b is a shape corresponding to the outer portion of the pitch circle 7p in the tooth 7b inside the pitch circle 9p of the driven rotor 9, that is, a shape created when the drive rotor 7 rotates. . Each tooth 7 b of the drive rotor 7 is twisted with respect to the axis 7 c of the drive rotor 7, and each tooth 9 b of the driven rotor 9 is twisted with respect to the axis 9 c of the driven rotor 9. As for the twisting direction of the teeth 7b and the twisting direction of the teeth 9b, the ends of the teeth 7b and 9b located on the first lid 3c side rotate more than the ends of the teeth 7b and 9b located on the second lid 3d side. It is set to be located downstream in the direction. This twist angle will be described in detail later.

  A first groove 11 is formed for each tooth 9b on the rotor end surface 9d on the second lid 3d side of the driven rotor 9, and a second surface 3e of the second casing 3b facing the rotor end surface 9d is a second end. A groove 13 is formed. The first groove 11 and the second groove 13 will be described in detail later.

  The tooth surface shapes of the teeth 7b of the drive rotor 7 and the teeth 9b of the driven rotor 9 are designed so as to obtain the following three postures.

First posture: a posture in which the teeth 7b of the drive rotor 7 are in contact with the teeth 9b of the driven rotor 9 at one position as shown in FIG. 3A (a closed space is formed between the teeth 7b and 9b). Absent)

Second posture: as shown in FIG. 3B, the tooth 7b of the drive rotor 7 is in contact with the tooth 9b of the driven rotor 9 at two positions d and o (initial meshing posture).

3rd posture: the posture rotated from the initial meshing posture as shown in FIG. 3 (c), and in addition to the two-position force and the key moved in accordance with the rotation, Posture (three-point meshing posture) in which the tooth 7b of the drive rotor 7 is further in contact with the tooth 9b of the driven rotor 9 at one position on the upstream side in the rotational direction from the second position.

  The direction of the torque Tm generated in the drive rotor 7 is such that a moment in the direction opposite to the rotation direction of the drive rotor 7 is generated in the drive rotor 7 in any of the first attitude, the second attitude, and the third attitude. Become. Specifically, the direction of the torque Tm generated in the drive rotor 7 in the first posture shown in FIG. 3A is based on the contact position A between the teeth 7b and 9b and the contact position A between the teeth 7b and the casing 3. The direction of the perpendicular bisector of the connecting line segment and the direction of the torque Tm generated in the drive rotor 7 in the second posture shown in FIG. 3B is the same as the contact position d of the teeth 7b and 9b. 7b and the direction of the perpendicular bisector connecting the contact position o of the tooth 9b, and the direction of the torque Tm generated in the drive rotor 7 in the third posture shown in FIG. It is represented by the direction of the perpendicular bisector connecting the contact position F of the tooth 9b and the contact position K of the tooth 7b and the tooth 9b.

  On the other hand, the direction of the torque Tf generated in the driven rotor 9 is perpendicular to the line segment connecting the contact position A with the teeth 9b and the contact position U of the casing 3 in the first posture shown in FIG. The direction of the bisector, which is a direction that causes the driven rotor 9 to generate a moment opposite to the rotational direction of the driven rotor 9, and in the second posture shown in FIG. 3c is the direction of the perpendicular bisector connecting the contact position o and the axis 9c of the driven rotor 9, and in the third posture shown in FIG. This is a direction of a perpendicular bisector connecting a line and the contact position K, and a direction in which the driven rotor 9 generates a moment in the same direction as the rotational direction of the driven rotor 9.

  Here, the torque Tf for generating a moment in the driven rotor 9 in the same direction as the rotation direction of the driven rotor 9 is considered to be a negative value when it works to help the rotation, and conversely, it works to prevent the rotation. Is considered a positive value.

  At this time, the torque Tf generated in the driven rotor 9 has a positive value in the first posture, 0 in the second posture, and a negative value in the third posture. Since the driven rotor 9 changes in this order from the first posture, the second posture, and the third posture with rotation, the total torque value from the first posture to the third posture is made to approach zero. Is possible.

  The design of the tooth surfaces of the drive rotor 7 and the driven rotor 9 having such a configuration is performed as follows based on FIG.

  The shape of the tooth 7b of the drive rotor 7 has two different shapes, a rotation direction side tooth surface (X) and an anti-rotation direction side tooth surface (Y) across the tooth tip. When the surface (X) is defined as the first function (H), the tooth surface of the driven rotor 9 facing the surface (X) is a generating function of the first function (H) when the opposite drive rotor 7 rotates in the counter-rotating direction. It is defined by a certain second function (h). During the rotation, the pitch circles 7p and 9p are rotated so as not to slip. In the counter-rotation direction side tooth surface (Y), if the tooth tip side portion of the counter-rotation direction side tooth surface (Y) is defined as a third function (F), the tooth surface of the driven rotor 9 is driven on the other side. It is defined by a fourth function (f) that is a generating function of the third function (F) when the rotor 7 rotates in the counter-rotating direction, and the tooth profile region of the fourth function (f) is a pitch circle of the driven rotor 9. 9p is defined up to the tooth tip of the driven rotor 9 by the fifth function (g) smoothly connected to the fourth function (f) at the predetermined position. In the state where the sixth function (G), which is the creation function of the fifth function (g) when rotating in the rotation direction, follows the portion defined by the third function (F), Y) is defined. Also in this case, the rotation is performed so that the pitch circles 7p and 9p do not slip each other as before.

  Accordingly, in the third posture, as shown in FIGS. 4 and 5, the contact position between the first function (H) and the second function (h), the third function (F), and the fourth function (f ) And a contact position K between the fifth function (g) and the sixth function (G).

  By the way, in the third posture, there is an upstream space A surrounded by the contact position K and the contact position K in addition to the downstream space B surrounded by the contact position K and the contact position K.

In this state, the torque Tm acting on the drive rotor 7 is expressed by the following equation (1):
Tm = L × Km × Z × (Pd−Ps) (Formula 1)
Where, L: the length of the line segment connecting the contact position K and the contact position Km: the distance between the vertical bisector connecting the two position K and the key and the axis 7c of the drive rotor 7 Z: the drive rotor 7 Axial length Pd: Pressure in downstream space B Ps: Pressure in upstream space A

In the same state, the torque Tf acting on the driven rotor 9 acts in the same direction as the rotation direction of the driven rotor 9 as described above to assist the rotation, and therefore is expressed as a negative value as shown in the following two equations.

Tf = −L × Kf × Z × (Pd−Ps) (Formula 2)
Kf: distance between the vertical bisector connecting the two positions and the axis 9c of the driven rotor 9

FIG. 6 is a graph showing an example of the torque of the driving rotor (solid line) and the torque of the driven rotor (broken line), where the horizontal axis represents the rotor rotation angle (deg) and the vertical axis represents the torque.

  As understood from FIG. 6, the torque Tm generated in the drive rotor 7 is always a positive value. That is, as described above, the direction of the torque Tm generated in the drive rotor 7 is deviated from the axis 7c of the drive rotor 7 regardless of whether the direction is the first attitude, the second attitude, or the third attitude. This is a direction in which a moment in the direction opposite to the rotation direction is generated in the drive rotor 7. On the other hand, the torque Tf generated in the driven rotor 9 becomes a negative value after becoming 0 from the positive value. That is, as described above, the direction of the torque Tf generated in the driven rotor 9 is the direction of the perpendicular bisector between the contact position a and the contact position c in the first posture, and is driven. This is the direction in which a moment in the direction opposite to the rotational direction of the rotor 9 is generated in the driven rotor 9, which is a positive value. Then, in the second posture, it is generated in the driven rotor 9 in the direction of the perpendicular bisector of the line segment between the contact position d and the contact position o and in the direction of the axis 9c of the driven rotor 9. The torque is 0, and in the third posture, the moment in the same direction as the rotational direction of the driven rotor 9 is driven in the direction of the perpendicular bisector of the contact position force and the contact position key. The torque is generated in the rotor 9 and the torque Tf generated in the driven rotor 9 has a negative value.

  Therefore, in the third posture, the torque Tf generated in the driven rotor 9 can be set to a negative value, so that the driven rotor 9 can be idled, and this idle rotation reduces wear of both the rotors 7 and 9. obtain. Then, it is desirable to increase the torque at the idling state on the negative side. For this purpose, the value of Ps is made smaller than the value of Pd based on the above two formulas.

  Therefore, in the present embodiment, regarding the formation of the upstream space A, only the contact position key exists when the second posture (initial meshing posture) is reached as shown in FIG. ) So that two contact position keys are formed, and thereafter, the distance between the contact positions and the mark, that is, the volume of the upstream space A is increased. Designed to. In other words, the design is made such that the value of Ps is reduced, preferably close to 0, by increasing the upstream space A from the volume 0.

  In the gear pump 1 according to the present embodiment configured as described above, in the third posture (three-point meshing posture), the pressure in the downstream space B that is between the two positions at the downstream side in the rotational direction. Is higher than the pressure in the upstream space A between the two positions at the upstream side in the rotational direction, so that the pressure in the upstream space A does not significantly affect the rotation of the driven rotor 9, and The perpendicular bisector connecting the two positions K on the downstream side in the rotational direction is shifted from the axis 9 c of the driven rotor 9 so as to generate a rotational moment in the driven rotor 9. For this reason, it is possible to rotate the driven rotor 9 in an idle state in the three-point meshing posture. Thereby, even when a working fluid having a low viscosity is used, it is possible to suppress the occurrence of wear of both rotors 7 and 9.

  In the present embodiment, when the second posture (initial meshing posture) is changed to the third posture (three-point meshing posture), the upstream space A is formed from zero volume. The rotation direction of the rotor 9 can be prevented from being affected at all, and the driven rotor 9 can be rotated more reliably in the idling state in the third posture.

  Further, in this embodiment, as described above, the driving rotor 7 and the driven rotor 9 are used in which the teeth 7b and 9b of each rotor are twisted with respect to the shaft centers 7c and 9c of each rotor. It becomes possible to allow the liquid contained in the side space B to escape to the discharge chamber 17. This will be described with reference to FIG.

FIG. 8 shows a state in which the drive rotor 7 and the driven rotor 9 are engaged with each other and rotated, and FIGS. 8 (m), 8 (o), 8 (q), 8 (s), and 8 (u) are the first ones. FIG. 8 (n), FIG. 8 (p), FIG. 8 (r), FIG. 8 (t), and FIG. 8 (v) show the rotor end face on the second lid 3d side. Indicates. 8 (m) and FIG. 8 (n), when the rotation angle is 0 degree, FIG. 8 (o) and FIG. 8 (p), when the rotation angle is 7.2 degrees, FIG. 8 (r) is when the rotation angle is 14.4 degrees, FIG. 8 (s) and FIG. 8 (t) are when the rotation angle is 21.6 degrees, and FIG. 8 (u) and FIG. 8 (v) are This is when the rotation angle is 28.8 degrees. In addition, sa, shi, su and se in the figure are for showing that the tooth gap is connected at one end and the other end of each rotor. For example, in FIG. 8 (o) and FIG. 8 (p) 8 (o) represents the portion where the tooth gap is connected to the cell in FIG. 8 (p), and the tooth gap is connected to the tooth in FIG. 8 (o) and the tooth in FIG. 8 (p). Represents a part. The same applies to the other drawings.

  From FIG. 8, when the rotation angle is 14.4 degrees, 21.6 degrees, and 28.8 degrees, FIG. 8 (q), FIG. 8 (s), and FIG. It is understood that the downstream space B is connected to the discharge chamber 17 from the positional relationship with the cell shown in (r), FIG. 8 (t), and FIG. 8 (v). The twist angle of the drive rotor 7 and the driven rotor 9 described above is set to an angle range in which the downstream space B is connected to the discharge chamber 17 when the downstream space B is formed.

  Due to the twisting of the drive rotor 7 and the driven rotor 9, the meshing position of the teeth 7b and the teeth 9b is moved, so that the liquid contained in the downstream space B can be released to the discharge chamber 17, and the gear pump Breakage can be prevented.

  Further, in the present embodiment, as described above, the first groove 11 is formed on the rotor end surface 9d of the driven rotor 9, and the second groove 13 is formed on the casing 3, so that the downstream space B in the third posture is formed. Even if the volume of the gas decreases with the rotation of the rotor and the pressure in the downstream space B increases, the liquid in the downstream space B can escape to the discharge chamber 17 and damage to the gear pump can be prevented. In order to make this possible, as shown in FIG. 2, the first groove 11 is a portion where the downstream space B of the rotor end surface 9 d in the driven rotor 9 is formed in the third posture, and each tooth On the other hand, the second groove 13 is formed on the surface 3e facing the rotor end surface 9d of the casing 3 and discharges with the first groove 11 provided on the teeth 9b of the driven rotor 9 meshing with the teeth 7b of the drive rotor 7. It is formed so as to communicate with the chamber 17 when it is in the third posture. Due to the communication between the first groove 11 and the discharge chamber 17, the pressure in the downstream space B becomes equal to the pressure in the discharge chamber 17.

  The second groove 13 is provided so that one end communicates with the discharge chamber 17. The other end is immediately before the liquid causes a back flow from the discharge chamber 17 to the downstream space B as shown in FIG. 9. Thus, it is disposed at a position where the communication with the first groove 11 is released. On the other hand, the 1st groove | channel 11 is provided in the part in which the one end is formed in the downstream space B, and the other end is arrange | positioned in the position where communication with the 2nd groove | channel 13 is cancelled | released just before raising the said backflow. Further, the first groove 11 and the second groove 13 may be linear as shown in FIGS. 2 and 9 or may be curved although not shown.

  In the above-described embodiment, the drive rotor having 10 teeth and the driven rotor having 12 teeth are used, but the present invention is not limited to this. For example, a drive rotor having 4 teeth and a driven rotor having 6 teeth may be used, or a drive rotor and a follower rotor having other numbers of teeth may be used.

  In the above-described embodiment, the first groove 11 and the second groove 13 are used so that the pressure in the downstream space B becomes the pressure in the discharge chamber 17, and in addition, the downstream space B and the discharge chamber 17 communicate with each other. In this manner, the pressure of the downstream space B is made the pressure of the discharge chamber 17 by using the drive rotor 7 and the driven rotor 9 in which the teeth 7b and the teeth 9b of the rotors are twisted with respect to the shaft centers 7c and 9c of the rotors. However, the present invention is not limited to this. For example, the pressure in the downstream space B may be set to the pressure in the discharge chamber 17 only by using the first groove 11 and the second groove 13. Alternatively, by using the drive rotor 7 and the driven rotor 9 in which the teeth 7b and teeth 9b of each rotor are twisted with respect to the shaft centers 7c and 9c of each rotor so that the downstream space B and the discharge chamber 17 communicate with each other, The pressure in the downstream space B and the pressure in the discharge chamber 17 may be the same pressure. However, when the pressure in the downstream space B is made to coincide with the pressure in the discharge chamber 17 only by using the first groove 11 and the second groove 13 as in the former, the downstream space B and the discharge chamber Although it is not necessary to set the twist angle of the rotor teeth 7b, 9b with respect to the shaft centers 7c, 9c of the rotors so as to communicate with the rotor 17, the downstream space B can be obtained by setting a twist angle smaller than the twist angle. It is preferable that the liquid inside is moved to the first groove 11 side.

Furthermore, in the above-described embodiment, the first groove is formed in the driven rotor. However, the present invention is not limited to this, and the first groove may be formed in the drive rotor, or both the driven rotor and the drive rotor. A first groove may be formed. In this case, the second groove is provided at the position of the casing corresponding to the first groove.

DESCRIPTION OF SYMBOLS 1 Gear pump 3 Casing 7 Drive rotor 9 Driven rotor 7b, 9b Teeth 7c, 9c Axle 11 1st groove 13 2nd groove 15 Suction chamber 17 Discharge chamber B Downstream space A Upstream space

Claims (4)

A gear pump including a drive rotor and a driven rotor that are housed in a casing in a state of being engaged with each other,
The driving rotor and the driven rotor have an initial meshing posture in which the teeth of the driving rotor come into contact with two teeth spaced apart from the teeth of the driven rotor, and a posture rotated from the initial meshing posture, the two positions In addition to the two positions moved along with the rotation, there is a three-point meshing posture in which the teeth of the drive rotor come into contact with the teeth of the driven rotor at a position upstream of the two positions after the movement. Yes,
In the three-point meshing posture, the pressure in the downstream space between the two positions downstream in the rotation direction is higher than the pressure in the upstream space between the two positions upstream in the rotation direction, and the rotation direction A perpendicular bisector connecting two downstream positions deviates from the axis of the driven rotor so as to generate a rotational moment in the driven rotor ;
A working fluid discharge chamber is provided in the casing,
A first groove communicating with the downstream space is formed on at least one rotor end surface of the drive rotor and the driven rotor, and the three-point meshing is formed on the surface of the casing facing the rotor end surface having the first groove. A gear pump characterized in that a second groove is formed for communicating the first groove and the discharge chamber in the posture . The gear pump according to claim 1, wherein
The upstream space is a gear pump having a volume of zero when changing from the initial meshing posture to the three-point meshing posture. The gear pump according to claim 1 or 2,
A working fluid discharge chamber is provided in the casing,
The teeth of the drive rotor and the teeth of the driven rotor are twisted with respect to the respective rotor shaft centers, and the downstream space is connected to the discharge chamber by the twist, but the teeth of the drive rotor and the teeth of the driven rotor The gear pump is configured to be closed with respect to the suction chamber by a portion in close contact with the suction chamber . The gear pump according to any one of claims 1 to 3 ,
The tooth shape of the drive rotor has two different shapes, a rotational direction side tooth surface (X) and an anti-rotation direction side tooth surface (Y) across the tooth tip, and the rotational direction side tooth surface When (X) is defined as the first function (H), the tooth surface of the driven rotor facing the second function (H) is a generating function of the first function (H) when the drive rotor rotates in the counter-rotating direction ( h), the tooth surface of the driven rotor is defined as the third function (F) when the tooth tip side in the counter rotation direction side tooth surface (Y) is defined as the third function (F). It is defined by a fourth function (f) that is a generating function of the third function (F) when the driving rotor rotates in the counter-rotating direction, and the tooth profile region of the fourth function (f) is defined by the driven rotor. The fifth function (g) up to a predetermined position in the pitch circle and connected to this fourth function (f) And the sixth function (G), which is the creation function of the fifth function (g) when the driven rotor is rotated in the rotation direction, is defined by the third function (F). A gear pump characterized in that the anti-rotation direction side tooth surface (Y) is defined in a state following the formed portion.

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