Gear pump device

Abstract

To provide a gear pump device which enables further improvement of durability while inhibiting performance deterioration when used in a corrosive fluid.SOLUTION: A gear pump device sends a corrosive fluid having corrosiveness and includes: a housing having an inlet port and an outlet port; a driving gear which is housed in the housing and rotationally driven through a driving shaft; and a driven gear which engages with the driving gear, is rotatably housed in the housing, and sends the corrosive fluid from the inlet port to the outlet port with the driving gear. The driving gear and the driven gear are formed of high nitrogen martensitic stainless steel.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gear pump device for delivering corrosive fluids.

Background Art

[0002] A gear pump device is known as a device for delivering corrosive fluids such as molten resins like chemical fiber spinning solutions and plastic spinning solutions, liquid foods, and paints. And, as a gear pump device, there is a gear pump as described in Patent Document 1, for example. In the gear pump device of Patent Document 1, a corrosive fluid is delivered by a driving gear and a driven gear that follows it.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a gear pump device, corrosion resistance is ensured by using a material having corrosion resistance against a corrosive fluid having corrosiveness (for example, high-speed steel). Thereby, it is possible to suppress a decrease in the performance of the gear pump device and improve its durability. On the other hand, simply ensuring corrosion resistance in a gear pump device applied to a corrosive fluid has limitations in suppressing a decrease in performance and improving durability. However, in a gear pump device, further suppression of performance degradation and improvement of durability are required.

[0005] Therefore, an object of the present invention is to provide a gear pump device that can suppress a decrease in performance and further improve durability when applied to a corrosive fluid.

Means for Solving the Problems

[0006] The gear pump device of the present invention is a gear pump device for pumping corrosive fluid, a housing having an inlet port and an outlet port, a drive gear housed in the housing and rotationally driven via a drive shaft, and a driven gear meshing with the drive gear and rotatably housed in the housing, the driven gear sending out the corrosive fluid together with the drive gear from the inlet port to the outlet port, wherein the drive gear and the driven gear are made of high nitrogen martensitic stainless steel.

[0007] According to the present invention, since the drive gear and the driven gear are made of high nitrogen martensitic stainless steel, the drive gear and the driven gear can increase their hardness while ensuring corrosion resistance to corrosive fluid. And by increasing the hardness, wear between the meshing gears can be suppressed. Therefore, in addition to suppressing performance degradation due to corrosion resistance and improving durability, the drive gear and the driven gear can also suppress performance degradation due to wear resistance and improve durability. Thereby, the gear pump device can suppress performance degradation and further improve durability when applied to corrosive fluid.

Effect of the Invention

[0008] According to the present invention, performance degradation can be suppressed and durability can be further improved when applied to corrosive fluid.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0010] Hereinafter, the gear pump device 1 according to the embodiment of the present invention will be described with reference to the above-mentioned drawings. Note that the concept of direction used in the following description is for convenience in explanation and does not limit the orientation of the invention configuration or the like in that direction. In addition, the gear pump device 1 described below is only one embodiment of the present invention. Therefore, the present invention is not limited to the embodiment, and addition, deletion, and modification are possible without departing from the gist of the invention.

[0011] <Gear pump device> As a device for delivering a corrosive fluid, a gear pump device 1 as shown in FIG. 1 is used. In the present invention, the corrosive fluid is, for example, a corrosive liquid organic substance such as chemical fiber stock solution, molten resin such as plastic stock solution, chemicals, liquid food, and paint. In this embodiment, the chemical fiber stock solution includes aramid fiber stock solution and polyester fiber stock solution, etc. Also, the plastic stock solution is polyester stock solution, polyvinyl alcohol stock solution, etc. The gear pump device 1 is a precision gear pump device that can pressurize and deliver (i.e., pump) a fixed amount of corrosive fluid according to the rotation speed. The gear pump device 1 is connected to a supply source (for example, an extruder) and an output destination (for example, a die head and a die) (both not shown). Then, the gear pump device 1 pumps the corrosive fluid extruded from the extruder to the output destination. More specifically, as shown in FIG. 2, the gear pump device 1 includes a housing 11, an electric motor 12, a drive gear 13, and a driven gear 14.

[0012] <Housing> The housing 11 has an inlet port 11a and an outlet port 11b. The inlet port 11a is a port through which a corrosive fluid is introduced. Also, the outlet port 11b is a port through which the corrosive fluid is sent out. In the present embodiment, the inlet port 11a is connected to the supply source described above. And the outlet port 11b is connected to the output destination described above. Further, the housing 11 has two gear chambers 11c and 11d inside. Note that the housing 11 is formed in a rectangular parallelepiped shape having a thickness and a rectangular shape when viewed from the front in the present embodiment. However, the housing 11 may be circular or polygonal when viewed from the front, and its shape is not limited.

[0013] Explaining the configuration of the housing 11 in more detail, the housing 11 has a gear case 21 and a pair of plates 22 and 23. The gear case 21 has two gear chambers 11c and 11d. The two gear chambers 11c and 11d are rooms extending in a predetermined direction in the gear case 21. Also, the gear chambers 11c and 11d are formed in a substantially circular shape when viewed in a predetermined direction. In the present embodiment, the two gear chambers 11c and 11d penetrate the gear case 21 in the thickness direction, which is an example of a predetermined direction. Also, the two gear chambers 11c and 11d are arranged such that a part of them overlaps each other when viewed from the front in the thickness direction. And the gear case 21 has an inlet passage 21a and an outlet passage 21b formed at a portion where the peripheries of the two gear chambers 11c and 11d overlap each other.

[0014] The pair of plates 22 and 23 sandwich the gear chambers 11c and 11d of the gear case 21 from both sides in the thickness direction. That is, both sides in the thickness direction of the gear chambers 11c and 11d are covered by the pair of plates 22 and 23. Also, one of the two plates 22 and 23, the first plate 22, has a through hole 22a. The through hole 22a penetrates the first plate 22 in the thickness direction. Also, the through hole 22a is formed corresponding to one of the two gear chambers 11c and 11d. In the present embodiment, the through hole 22a is formed in the first plate 22 so that its axis coincides with the axis L1 of the drive gear chamber 11c, which is one of the two gear chambers 11c.

[0015] On the second plate 23, which is the other of the two plates 22 and 23, the aforementioned two ports 11a and 11b are formed. Each of the two ports 11a and 11b is connected to the inlet passage 21a and the outlet passage 21b of the gear case 21. Thus, the inlet port 11a is connected to the two gear chambers 11c and 11d via the inlet passage 21a, and the two gear chambers 11c and 11d are connected to the outlet port 11b via the outlet passage 21b.

[0016] <Electric motor> The electric motor 12 is provided on the main surface of the housing 11 (the first plate 22 in this embodiment). The electric motor 12 rotationally drives the drive gear 13, which will be described in detail later. And the electric motor 12 controls the rotational speed of the drive gear 13 according to the flow rate of the corrosive fluid to be pumped. More specifically, the electric motor 12 has a stator 12a, a rotor 12b, and a drive shaft 12c. The stator 12a rotatably houses the rotor 12b therein. Also, a drive shaft 12c is non-rotatably provided on the rotor 12b. The protruding portion of the drive shaft 12c from its intermediate portion to the tip side portion protrudes from the rotor 12b. The protruding portion of the drive shaft 12c is inserted through the through hole 22a. And the base end side and the tip side of the protruding portion of the drive shaft 12c are respectively pivotally supported by the plates 22 and 23. Note that what drives the drive shaft 12c is not limited to an electric motor, and a prime mover such as an engine may be used.

[0017] <Drive gear> The drive gear 13 is housed in the housing 11. Further, the drive gear 13 is rotationally driven via the drive shaft 12c. And, when the drive gear 13 is rotationally driven, it sends out the corrosive fluid from the inlet port 11a to the outlet port 11b. More specifically, the drive gear 13 is an external gear. In the present embodiment, the drive gear 13 is a spur gear. However, the drive gear 13 is not limited to a spur gear, and may be other gears such as a helical gear and a worm gear. The drive gear 13 is arranged such that its axis coincides with the axis L1 of the drive gear chamber 11c. And, the drive gear 13 is formed so as to leave predetermined side clearances c1, c2 between both its side surfaces and the housing 11 (more specifically, the two plates 22, 23) (see FIG. 3). The side clearances c1, c2 are, for example, 10 μm or more and 100 μm or less.

[0018] Also, as shown in FIG. 4, an insertion hole 13a is formed around the axis of the drive gear 13. The drive shaft 12c is inserted into the insertion hole 13a. More specifically, the insertion hole 13a is formed so as to leave a predetermined gap Δd1 between the drive gear 13 and the drive shaft 12c. The predetermined gap Δd1 is 9 μm or more and 100 μm or less. In the present embodiment, the predetermined gap Δd1 is preferably 15 μm or more and 100 μm or less.

[0019] Furthermore, the drive gear 13 is non-rotatable relative to the drive shaft 12c. More specifically, the drive gear 13 is non-rotatable relative to the drive shaft 12c by the key groove 13b of the insertion hole 13a and the key member 12d provided on the drive shaft 12c. Thereby, since the drive gear 13 rotates integrally with the drive shaft 12c, the electric motor 12 can rotationally drive the drive gear 13. Note that the connection between the drive shaft 12c and the drive gear 13 does not necessarily have to be the connection as described above. The connection between the drive shaft 12c and the drive gear 13 may be, for example, a spline connection, as long as the two are non-rotatable relative to each other.

[0020] <Driven Gear> The driven gear 14 meshes with the driving gear 13 as shown in Fig. 1 and is rotatably accommodated in the housing 11. Also, the driven gear 14, together with the driving gear 13, sends out the corrosive fluid from the inlet port 11a to the outlet port 11b. More specifically described, the driven gear 14 is an external gear. In the present embodiment, the driven gear 14 is a spur gear, the same as the driving gear 13. However, the driven gear 14 is not limited to a spur gear either, and may be other gears such as a helical gear and a herringbone gear. The driven gear 14 is arranged such that its axis coincides with the axis L2 of the driven gear chamber 11d and meshes with the driving gear 13. That is, the driving gear 13 and the driven gear 14 mesh with each other at the overlapping part of the two gear chambers 11c and 11d. Further, the driven gear 14 is formed so as to have predetermined side clearances c3 and c4 between both of its side surfaces and the housing 11 (more specifically, the two plates 22 and 23) (see Fig. 3). The side clearances c3 and c4 are, for example, 10 μm or more and 100 μm or less.

[0021] Also, as shown in Fig. 4, an insertion hole 14a is formed around the axis of the driven gear 14 as well. A driven shaft 24 is inserted through the insertion hole 14a so as to be relatively rotatable. The driven shaft 24 is installed between the two plates 22 and 23 (see Fig. 3). Therefore, the driven gear 14 rotates around the axis L2 following the meshing driving gear 13. Also, the insertion hole 14a is formed so as to have a predetermined gap Δd2 (not shown) between the driven gear 14 and the driven shaft 24. The predetermined gap Δd2 is 9 μm or more and 100 μm or less. In the present embodiment, the predetermined gap Δd2 is preferably 15 μm or more and 100 μm or less.

[0022] <Material of the gear> The driving gear 13 and the driven gear 14 are made of high-nitrogen martensitic stainless steel. Here, the high-nitrogen martensitic stainless steel is a stainless steel containing iron, carbon, chromium, molybdenum, and nitrogen, and the nitrogen content is 0.1% by weight or more. Further, the nitrogen content in the high-nitrogen martensitic stainless steel is preferably 0.15% by weight or more and 0.3% by weight or less. And the high-nitrogen martensitic stainless steel preferably has a Rockwell hardness of 40 or more. Such high-nitrogen martensitic stainless steel is produced, for example, by a method of pressurizing the atmosphere during melting of metal raw materials with nitrogen (for example, the pressurized dielectric melting method and the pressurized ESR method). Also, the high-nitrogen martensitic stainless steel may be produced by a method of increasing the nitrogen solubility by adding alloying elements such as chromium and manganese, and the production method is not limited. The driving gear 13 and the driven gear 14 made of such a material can increase the hardness while ensuring corrosion resistance against corrosive fluids.

[0023] <Operation of the gear pump device> In the gear pump device 1, the driving gear 13 is rotationally driven by the electric motor 12. Then, the driven gear 14 rotates following the driving gear 13. Also, the two gears 13, 14 form a plurality of chambers 13c, 14c (in FIG. 1, only the reference numerals of each one chamber 13c, 14c are shown) between two adjacent teeth and the peripheral surfaces of the respective gear chambers 11c, 11d (that is, the inner peripheral surface of the gear case 21). And the plurality of chambers 13c, 14c are sent from the inlet port 11a side to the outlet port 11b side along the peripheral surfaces of the respective gear chambers 11c, 11d as the two gears 13, 14 rotate. Thereby, each chamber 13c, 14c sucks the corrosive fluid led from the inlet port 11a into the gear chambers 11c, 11d when being sent. Then, each chamber 13c, 14c pumps the corrosive fluid to the outlet passage 21b by being sent to the outlet port 11b side. And the pumped corrosive fluid is discharged from the outlet port 11b.

[0024] In the gear pump device 1 configured as described above, since the driving gear 13 and the driven gear 14 are made of high nitrogen martensitic stainless steel, the driving gear 13 and the driven gear 14 can increase their hardness while ensuring corrosion resistance against corrosive fluids. And by increasing the hardness, wear between the meshing gears 13 and 14 can be suppressed. Therefore, the driving gear 13 and the driven gear 14 can suppress performance degradation and improve durability by having wear resistance in addition to suppressing performance degradation and improving durability by having corrosion resistance. As a result, the gear pump device 1 can suppress performance degradation and further improve durability when applied to a corrosive fluid.

[0025] Also, in the gear pump device 1 of the present embodiment, the nitrogen content of the high nitrogen martensitic stainless steel constituting the driving gear 13 and the driven gear 14 is 0.1% by weight or more. Therefore, the driving gear 13 and the driven gear 14 can increase their hardness while ensuring corrosion resistance against corrosive fluids. Therefore, the gear pump device 1 can suppress performance degradation and further improve durability when applied to a corrosive fluid.

[0026] Furthermore, in the gear pump device 1 of the present embodiment, since the high nitrogen martensitic stainless steel constituting the driving gear 13 and the driven gear 14 has a Rockwell hardness of 40 or more, wear resistance can be improved while having corrosion resistance. As a result, the gear pump device 1 can suppress performance degradation and further improve durability when applied to a corrosive fluid.

[0027] Also, in the gear pump device 1 of the present embodiment, each of the side clearances c1 to c4 between the driving gear 13 and the driven gear 14 is 10 μm or more and 100 μm or less. Therefore, it is possible to prevent malfunction caused by the driving gear 13 and the driven gear 14 hitting the housing 11 (more specifically, the plates 22 and 23) while suppressing a decrease in the volumetric efficiency of the gear pump device 1.

[0028] Furthermore, in the gear pump device 1 of the present embodiment, since a predetermined gap Δd1 between the drive gear 13 and the drive shaft 12c is 9 μm or more, relative movement of the drive gear 13 in the thrust direction with respect to the drive shaft 12c (hereinafter simply referred to as "relative movement") can be allowed. Thereby, it is possible to suppress the side surface of the drive gear 13 from constantly contacting the housing 11 (more specifically, the plates 22 and 23). Therefore, it is possible to prevent the drive gear 13 from malfunctioning. Further, even if the drive gear 13 can operate, it is possible to prevent the drive gear 13 from being worn by the plates 22 and 23. Then, since changes in the side clearances c1 and c2 are suppressed, changes in the discharge flow rate with respect to the rotational speed of the drive gear 13 are suppressed. That is, the discharge flow rate of the gear pump device 1 can be accurately controlled.

[0029] More specifically, the drive shaft 12c is made of a material different from that of the drive gear 13. In the present embodiment, the drive shaft 12c is, for example, austenitic stainless steel and has a larger expansion rate than the drive gear 13. Note that the material of the drive shaft 12c is not limited to the above-described material, and may be, for example, martensitic stainless steel. Further, the corrosive fluid to be pumped may be generated by thermal melting. Such a corrosive fluid may reach a high temperature of, for example, 100 degrees or more and 400 degrees or less. When the corrosive fluid is at such a high temperature as described above, if the predetermined gap Δd1 is small, the following occurs. That is, when the drive shaft 12c expands, the drive gear 13 is in a shrink-fit state with respect to the drive shaft 12c. Then, the drive gear 13 cannot move relatively. When the drive gear 13 cannot move relatively in a state where the side surface of the drive gear 13 is in contact with any of the plates 22 and 23, the gears 13 and 14 malfunction. Further, even if the drive gear 13 can operate, the plates 22 and 23 are worn by the drive gear 13. Then, the side clearances c1 and c2 between the side surface of the drive gear 13 and the housing 11 (more specifically, the plates 22 and 23) increase. As a result, the volumetric efficiency of the gear pump device 1 decreases, so the discharge flow rate changes.

[0030] On the other hand, in the gear pump device 1, since the predetermined gap Δd1 between the driving gear 13 and the driving shaft 12c is 9 μm or more, relative movement of the driving gear 13 is allowed even when the driving shaft 12c expands (see the two-dot chain line in FIG. 4). Therefore, it is possible to prevent the state where the side surface of the driving gear 13 abuts against the housing 11 from being maintained. Thereby, it is possible to prevent the driving gear 13 from malfunctioning or the driving gear 13 from wearing the plates 22 and 23. Therefore, the discharge flow rate of the gear pump device 1 can be suppressed from changing. That is, the discharge flow rate of the gear pump device 1 can be accurately controlled.

[0031] Further, since the predetermined gap Δd1 is 100 μm or less, it is possible to suppress the tip of the driving gear 13 from hitting the peripheral surface of the driving gear chamber 11c. Therefore, wear of the inner peripheral surface of the housing 11 can be suppressed. Thereby, since the change in the gap between the tip of the driving gear 13 and the inner peripheral surface of the housing 11 (more specifically, the peripheral surface of the driving gear chamber 11c), that is, the top clearance, can be suppressed, the discharge flow rate of the gear pump device 1 can be suppressed from changing. That is, the discharge flow rate of the gear pump device 1 can be accurately controlled. Further, since the predetermined gap Δd1 is 100 μm or less, it is possible to suppress the corrosive fluid from leaking between the driving gear 13 and the driving shaft 12c. Thereby, the discharge flow rate of the gear pump device 1 can be accurately controlled.

[0032] Further, the high-nitrogen martensitic stainless steel has a relatively small coefficient of thermal expansion. Therefore, even under high-temperature operating conditions where a high-temperature corrosive fluid is pumped, the driving gear 13 can satisfy the requirement for gap accuracy in the micron unit. Therefore, the discharge flow rate of the gear pump device 1 can be accurately controlled.

[0033] Furthermore, in the gear pump device 1, due to the difference in the expansion rates between austenitic stainless steel, martensitic stainless steel, and high-nitrogen martensitic stainless steel, the gap between the drive shaft 12c and the drive gear 13 can be appropriately filled during expansion. As a result, relative movement of the drive gear 13 with respect to the drive shaft 12c can be appropriately allowed, and leakage from the gap can be appropriately suppressed.

[0034] Regarding the driven gear 14 as well, since a predetermined gap Δd2 is provided between it and the driven shaft 24, the same effect as when a predetermined gap Δd1 is provided is achieved.

Explanation of Reference Numerals

[0035] 1 Gear pump device 11 Housing 11a Inlet port 11b Outlet port 12c Drive shaft 13 Drive gear 13a Insertion hole 14 Driven gear 14a Insertion hole Δd1 Gap

Claims

1. A gear pump device for delivering a corrosive fluid, comprising: a housing having an inlet port and an outlet port; a drive gear housed in the housing and rotationally driven via a drive shaft; a driven gear meshing with the drive gear and rotatably housed in the housing, the driven gear and the drive gear together delivering the corrosive fluid from the inlet port to the outlet port; wherein the drive gear and the driven gear are made of a high-nitrogen martensitic stainless steel having a nitrogen content of 0.15 wt% or more and 0.3 wt% or less.

2. The drive gear has an insertion hole through which the drive shaft is inserted non-rotatably. The insertion hole is formed so as to have a predetermined clearance from the drive shaft. The predetermined clearance is 9 μm or more and 100 μm or less. The gear pump device according to Claim 1.

3. The drive shaft is made of austenitic stainless steel or martensitic stainless steel. The gear pump device according to Claim 2.

4. Each of the drive gear and the driven gear is formed so as to have a predetermined side clearance between both side surfaces thereof and the housing. The side clearance is 10 μm or more and 100 μm or less. The gear pump device according to any one of Claims 1 to 3.

5. The high-nitrogen martensitic stainless steel constituting the drive gear and the driven gear has a Rockwell hardness of 40 or more. The gear pump device according to any one of Claims 1 to 4.

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