Gear pump

Abstract

To provide a gear pump generating high suction force by driving even without priming water.SOLUTION: A gear pump (1) comprises: a driving shaft (19a) rotated by driving force of a driving source; a driving gear (19) connected to the driving shaft to be rotated integrally therewith; a driven gear (21) connected to be rotated integrally with a driven shaft (21a) or rotated about the driven shaft by engagement with the driving gear; and a housing (3) provided with a pump chamber (5) for housing the driving gear and the driven gear. A fluid is sucked from a suction port (7) and discharged to a discharge port (9) by rotation of the driving gear and the driven gear. The suction port is offset to the driving gear side or the driven gear side. High suction force is exerted by generating imbalance of negative pressure by the offset.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a gear pump used for transporting liquids in, for example, cup-type vending machines (hereinafter referred to as "cup-type vending machines") that sell beverages in cups, beverage dispensers, dishwashers, private cleaning toilets, and other devices, which draws water that forms the basis of beverages, cleaning water, and other liquids to be transported into the gear pump through a suction port and sends it out through a discharge port. [Background technology]

[0002] The configuration of the hot water supply path of a conventional cup-type vending machine (hereinafter referred to as the "conventional cup-type vending machine") is as shown in Figure 10. Note that further detailed structure will be explained in the section on this embodiment described later. That is, conventional vending machine 201 first includes water tank 205 and gear pump 207 arranged at the bottom inside case 203, and control unit 209 that electrically controls gear pump 207 and the like. Water stored in water tank 205 is pumped (pushed up) by gear pump 207 to the top of case 203. The pushed-up water is heated in hot water tank 209 to become hot water, which is then dropped and supplied to extraction device 211. Extraction device 211 is configured to drop-supply a beverage made using hot water and ingredients supplied from ingredient supply device 210 into cup 213.

[0003] An example of a gear pump that can be used as the gear pump 107 is the gear pump described in Patent Document 1 (hereinafter referred to as "first conventional gear pump"). The first conventional gear pump includes a drive shaft that rotates by the driving force of a drive source (not shown), a drive gear connected to rotate integrally with the drive shaft, a driven gear connected to rotate around the driven shaft by meshing with the drive gear, and a housing in which a pump chamber is formed in which the drive gear and the driven gear are housed, and is configured to suck in a fluid from an intake port and discharge it to an outlet port by the rotation of the drive gear and the driven gear. In addition, there is generally a gap of several tens of microns between the pump chamber peripheral wall surrounding the pump chamber and the tips of the teeth of the gears (drive gear, driven gear). mSince there is a gap to ensure sufficient gear rotation, it is not completely sealed. However, if there is a gap, the pump pressure cannot be increased as desired, so this gap must be filled to create a seal. This gap is filled with priming water, which is filled into the pump chamber. Once operation begins and the pump chamber is filled with liquid, this liquid acts as priming water and seals the gap between the gear teeth and the peripheral wall of the pump chamber, creating a certain amount of suction pressure (negative pressure).

[0004] When operation is continued, the pump chamber is always filled with priming water, so this is not a problem, but the situation is different for cup-type vending machines. The interval between the sale of one cup drink and the sale of the next cup drink, i.e., the operation interval, may be long, for example, at night. In that case, the liquid (water in this case) filled at one end may flow out of the pump or evaporate and disappear. In other words, the issue is how to deal with the situation when the priming water runs out. This issue is common not only to the first conventional gear pump, but also to the gear pumps described in Patent Document 2 and Patent Document 3 described below.

[0005] To solve this problem, the first conventional gear pump mentioned above has annular water collecting grooves on both axial end faces (flat faces of the gears) of the drive gear and the driven gear. With this configuration, even if water flows out during a long stop, the water in the water collecting grooves will be ejected by the centrifugal force caused by the rotation of both gears and used as priming water.

[0006] Furthermore, the gear pump described in the aforementioned Patent Document 2 (hereinafter referred to as the "second conventional gear pump") has a basic structure in common with the first conventional gear pump, and attempts have been made to configure the dimensional accuracy of the gap between the tips of the gear teeth and the peripheral wall of the pump chamber to a level that enables air transport so as to eliminate the need for priming.

[0007] Furthermore, the gear pump described in the aforementioned Patent Document 3 (hereinafter referred to as the "third conventional gear pump") also shares the same basic structure as the first conventional gear pump, but has a priming chamber for storing priming water in a housing that communicates with the pump chamber via a plastic member. The gear rotates to generate negative pressure, which displaces the plastic member and draws the priming water from the priming chamber into the pump chamber. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Utility Model Application Publication No. 4-19681 (Figure 2, page 2, line 5 to page 3, line 16, page 6, line 5 to the last line of the same page) [Patent Document 2] JP 2016-118190 A (Fig. 3, paragraphs 0005, 0006, and 0033) [Patent Document 3] JP 2006-1201 A (Fig. 7, paragraphs 0003, 0007, and 0013) Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the first conventional gear pump, if the pump is stopped for such a long time that the water in the pump chamber evaporates, the water in the water collecting groove will also evaporate. Therefore, it is doubtful whether the water will remain as priming water until the next operation. Although it is possible to provide priming water to replace the water in the pump chamber that has flowed out in a short period of time, there is a problem in that it may not function sufficiently in situations where there is a possibility of a long-term stoppage.

[0010] The second conventional gear pump is said to be configured with a dimensional precision of the gap between the gear teeth and the pump chamber peripheral wall at a level that allows air transport, but it is clear that such a configuration is difficult to manufacture and involves cost difficulties. Issues remain in terms of the difficulty of manufacturing and the high costs.

[0011] The third conventional gear pump requires a priming chamber and a plastic member, and is structurally very complicated. This makes manufacturing and adjustment difficult, and is also disadvantageous in terms of cost. As with the first conventional gear pump, there is also a risk of the water in the priming chamber evaporating when the pump is stopped for an extended period of time. These are the issues with the third conventional gear pump.

[0012] The present invention has been made to solve the above-mentioned problems, and has an object to provide a gear pump that can increase the discharge volume per unit time without increasing the occupied space. [Means for solving the problem]

[0013] (Claim 1 Features of the Invention The gear pump according to the invention described in claim 2 (hereinafter referred to as "the gear pump of claim 2") comprises a drive shaft rotated by the driving force of a drive source, a drive gear connected to rotate integrally with the drive shaft, a driven gear connected to rotate integrally with or around the driven shaft by meshing with the drive gear, and a housing in which a pump chamber is formed in which the drive gear and the driven gear are accommodated, and the gear pump conveys liquid sucked in from an intake port by the rotation of the drive gear and the driven gear, and conveys the liquid to the drive gear side and the driven gear side, and then joins together just before the discharge port and discharges it from the discharge port. Here, the intake port and the discharge port are provided protruding in opposite directions from each other as viewed from the housing, and are spaced apart from each other by a suction side center line that passes at right angles to the center of the smallest circle that encloses the liquid path that passes through the intake port as viewed from the pump chamber side. Of the discharge-side center lines that pass through the center of the discharge port having a circular cross section, only the suction-side center line the intersection point with an axial center line that is perpendicular to the suction side center line and passes perpendicularly through the center line of the drive shaft and the center line of the driven shaft is located closer to the center of the drive shaft or closer to the center of the driven shaft than the midpoint between the center line of the drive shaft and the center line of the driven shaft.

[0014] Claim 1In the gear pump of the above, the driving gear rotates in the discharge direction due to the driving force of the driving source, and the driven gear meshing with the driving gear also rotates in the discharge direction in response to this rotation. The rotation of the driving gear generates negative pressure (negative pressure on the driving gear side) on the driving gear side (around the driving gear) in the pump chamber, and similarly generates negative pressure (negative pressure on the driven gear side) on the driven gear side (around the driven gear). These two negative pressures suck liquid from the suction port, and the sucked liquid is transported separately to the driving gear side and the driven gear side, and is discharged from the discharge port to the outside of the pump while merging just before the discharge port. Although the detailed causal relationship is unclear, experiments have shown that although the amount of protrusion may decrease compared to when the suction port is located in the center without offset, an improvement in suction power was observed, which is thought to be due to the negative pressure on the offset side being greater than the negative pressure on the other side, that is, negative pressure imbalance. As a result, it became possible to suck liquid not only when priming water was used, but also without priming water.

[0015] (Claim 2 Features of the Invention The pump includes a drive shaft that rotates by the driving force of a drive source, a drive gear connected to rotate integrally with the drive shaft, a driven gear connected to rotate integrally with the driven shaft or rotate around the driven shaft by meshing with the drive gear, and a housing in which a pump chamber is formed in which the drive gear and the driven gear are housed. The pump is sucked in from a suction port by the rotation of the drive gear and the driven gear. and trapped between the housing and the A gear pump which divides a fluid into a drive gear side and a driven gear side, conveys the fluid to be joined just before the discharge port, and discharges the fluid from the discharge port, wherein the suction port and the discharge port are provided protruding from the housing in a direction perpendicular to the thickness direction of the drive gear or the driven gear, respectively, and of the suction port and the discharge port, only the suction port is offset toward the drive gear side or the driven gear side.

[0016] Claim 2In the gear pump of the above, the driving gear rotates in the discharge direction due to the driving force of the driving source, and the driven gear meshing with the driving gear also rotates in the discharge direction in response to this rotation. The rotation of the driving gear generates negative pressure (negative pressure on the driving gear side) on the driving gear side (around the driving gear) in the pump chamber, and similarly generates negative pressure (negative pressure on the driven gear side) on the driven gear side (around the driven gear). These two negative pressures suck liquid from the suction port, and the sucked liquid is transported separately to the driving gear side and the driven gear side, and is discharged from the discharge port to the outside of the pump while merging just before the discharge port. Although the detailed causal relationship is unclear, experiments have shown that although the amount of protrusion may decrease compared to when the suction port is located in the center without offset, an improvement in suction power was observed, which is thought to be due to the negative pressure on the offset side being greater than the negative pressure on the other side, that is, negative pressure imbalance. As a result, it became possible to suck liquid not only when priming water was used, but also without priming water.

[0017] According to the present invention, the gear pump can be driven without priming to generate high suction power, so liquid can be transported to a higher position (farther in the case of horizontal transport), which expands the range of applications for the gear pump. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic internal view of a cup vending machine in which a gear pump according to the present invention is used. [Diagram 2] 1 is a perspective view of a gear pump according to the present invention; [Diagram 3] 1 is a perspective view of a gear pump according to the present invention; [Figure 4] FIG. 3 is an exploded perspective view of the gear pump shown in FIG. 2. [Diagram 5] 4 is a front view of the housing of the gear pump shown in FIG. 3 as viewed in the thickness direction from the panel side, with gears depicted by dashed two-dot lines. [Figure 6] FIG. 4 is a front view showing the housing of the gear pump shown in FIG. 3 in broken lines and showing a flow path and a pump chamber in solid lines. [Figure 7]FIG. 4 is a front view showing the housing of the gear pump shown in FIG. 3 in broken lines and showing a flow path and a pump chamber in solid lines. [Figure 8] FIG. 2 is a schematic front view of an experimental device used in the examples. [Figure 9] 1 is a table showing experimental results of an embodiment. [Figure 10] FIG. 1 is a schematic internal view of a conventional cup vending machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A preferred embodiment for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described below with reference to the drawings, starting with the internal structure of a cup vending machine and then the gear pump. Note that in the present embodiment, a cup vending machine is cited as one of the applications of the gear pump, but this is not intended to be a limitation. The gear pump described below can also be applied to types of vending machines other than cup vending machines, and can also be used for purposes other than vending machines, such as transporting and pumping cleaning liquid in a dishwasher.

[0020] (General structure of a cup vending machine) The cup-type vending machine is designated by the reference numeral 101 in FIG. 1. The cup-type vending machine 101 is a device capable of selling, for example, various kinds of regular coffee, cocoa, soup, fruit juice, carbonated drinks, etc., in cups. A preferred cup-type vending machine 1 is composed of a case body 103 that houses the main devices, and a case base 105 that holds the case body 103 on top. Only a water tank 115 is contained within the case base 105. Although not essential, the reason for separating the case body 103 and the case base 105 in this manner is to simplify the configuration of the case base 105 including the water tank 115, and to make it possible to move only the case body 103 or to replace it with another model.

[0021] The case body 103 constituting the cup vending machine 101 comprises as its main devices an extraction device 107, an ingredient supply device 109 and a hot water tank device 111 which respectively supply a predetermined amount of ground bean ingredient and hot water to the extraction device 107 at the time of sale, a gear pump 1 which draws up water from a water tank 113 and supplies it to the hot water tank device 111, a cup removal window 117 which opens to the outside, a cup supply device (not shown) which drops and places empty cups C one by one into the cup removal window 117, and a control device 119 consisting of a microcomputer which controls these devices. The water supplied to the hot water tank device 111 is heated and kept warm to a predetermined temperature (for example, 97°C) by a heater 113.

[0022] The extraction device 107 extracts coffee liquid by passing high-pressure hot water supplied from a hot water tank device 111 through ground bean raw material supplied from a raw material supply device 109. This coffee liquid is supplied to a cup C in a cup removal window 117, either directly or after being mixed with sugar, cream, etc. The raw material supply device 109 also has a mill (not shown) for grinding coffee beans, and supplies a predetermined amount of ground bean raw material ground by this mill to the extraction device 107.

[0023] (General structure of gear pump) The gear pump 1 will be described in detail. As shown in Figures 2 to 7, the housing 3 of the gear pump 1 includes a pump chamber 5 therein, a drive gear 19 and a driven gear 21 that are rotatably accommodated within the pump chamber 5 and mesh with each other, and a motor (drive source) 15 that drives the drive gear 19. The drive gear 19 has a drive shaft 19a for integral rotation, and the driven gear 21 has a passive shaft 21a for integral rotation, which protrude from both sides of the respective gears.

[0024] (Appearance of the housing and surrounding structure) The housing 3 has a box-shaped housing main body 3a and an attachment portion 3b protruding from one end of the housing main body 3a, a cover 11 fixed to one side of the housing main body 3a by a screw 33, and a bracket 13 fixed to the other side. In this specification, the direction from the one side (left side in FIG. 4) to the other side (right side in FIG. 4) is defined as the thickness direction of the housing main body 3a. Reference numeral 31 shown in FIG. 4 denotes an O-ring interposed between the cover 11 and the housing main body 3a. The bracket 13 has a cylindrical motor support portion 13a that houses and supports the motor 15, and a rectangular flange portion 13b that protrudes vertically from the periphery of the motor support portion 13a on the side closer to the housing main body 3a. The bracket 13 is fixed to the housing main body 3a by screws via the flange portion 13b. The attachment portion 3b is a portion that fixes the gear pump 1 to the case main body 103 of the cup-type vending machine 1 by screws.

[0025] The housing 3 may be made of metal or other materials, but in this embodiment, it is made of resin to reduce weight and cost. Although not specified in order, the members described below may also be made of metal or other materials, but for the same reasons as above, it is preferable to use resin to the extent possible.

[0026] (Pump room structure) The pump chamber 5 viewed from the front from the cover 11 side shown in Figures 4 to 7 has a basic shape similar to a gourd with parts of two circles of the same size overlapping. The pump chamber 5 has a triangular area 5c on the suction port 7 side, which is obtained by cutting off the part protruding into the gourd-like recess into a triangle, and a sector-shaped area 5d on the discharge port 9 side, which is similarly cut off into a sector-like shape, and the pump chamber 5 is formed in this shape leading to the rear wall 3c (Figure 3) of the housing main body 3a. One of the two circles corresponds to the drive gear chamber 5a that houses the drive gear 19, and the other circle corresponds to the driven gear chamber 5b that houses the driven gear 21. The gap between the pump chamber peripheral wall 5w that surrounds the pump chamber 5 and the tips of the teeth of the gears (drive gear 19, driven gear 21) is drawn large for convenience of drawing, but in reality, it is, for example, 10μ mThe gap is large enough to allow liquid to be transported while ensuring sufficient gear rotation. One side of the pump chamber 5 is closed by the slider 23 and the cover 11 covering the top of the slider 23, and the other side is closed by the back wall 3c. A bearing 29 is fixed to the back wall 3c, and the drive shaft is attached so as to be able to penetrate therethrough in the thickness direction, and an annular rib 3d for positioning the bracket 13 protrudes from the bracket 13 side.

[0027] The suction port 7 protrudes from one side of the housing body 3a in a lateral direction perpendicular to the thickness direction, and the discharge port 9 protrudes from the other side, and their respective hollow portions communicate with each other via the pump chamber 5, forming a liquid path 10 as a whole. The shape of the radial cross section of the liquid path 10 is generally circular, but is not limited to this. For example, it may be elliptical, polygonal, or other irregular shapes. The detailed relationship between the pump chamber 5 and the suction port 7 and discharge port 9 will be described later.

[0028] (Slider structure) 2 to 4, the pump chamber 5 is watertightly sealed on one side by a resin slider 23 and on the other side by a slider 25. Since the sliders 23 and 25 are made of the same material and have the same shape, the structure of only the slider 23 will be described, and overlapping parts of the structure of the slider 25 will be omitted. The driving gear 19 and the driven gear 21 in a meshed state are accommodated between the sliders 23 and 25 in a sandwiched state in which they can rotate while in contact with each other.

[0029] The slider 23 has a predetermined thickness and is capable of watertightly closing the pump chamber 5 as described above. For this reason, it has a shape that fits snugly into the pump chamber peripheral wall 5w. Furthermore, the slider 23 is formed with a drive hole 23a that passes through the center of one perfect circle and a follower hole 23b that passes through the center of the other perfect circle, penetrating in the thickness direction. Similarly, the slider 25 is formed with a drive hole 25a that passes through the center of one perfect circle and a follower hole 25b that passes through the center of the other perfect circle.

[0030] The drive hole 25a is a hole that rotatably supports the drive shaft 17 that passes therethrough, and the drive hole 23a is a hole that receives and rotatably supports the drive shaft 19a that protrudes from one end side of the drive gear 19. The driven hole 25b is a hole that receives and rotatably supports the other end side of the driven shaft 21a that protrudes from both sides of the driven gear 21, and the driven hole 23b is a hole that receives and rotatably supports one end side of the driven shaft 21a. The tip portion on one end side of the drive shaft 17 is formed in a D-shape in radial cross section, and is inserted into a D-shaped recess (not visible in FIG. 4, as it is behind the drive gear 19) formed on the surface of the drive gear 19 opposite the drive shaft 19a, so that they can rotate together.

[0031] The drive gear 19 is rotated by a drive shaft 17 driven by a motor 15 (shown by a two-dot chain line in FIG. 4), and the driven gear 21 rotates in response to the drive gear 19. As described above, the drive shaft 17 is rotatably supported by the bearing 29 .

[0032] (Relationship between pump chamber, suction port, and discharge port) The description will be given based on Figs. 5 to 7. Figs. 6 and 7 are the same, but in Fig. 6, the symbols are drawn around the components, and in Fig. 7, the diameter R and distance D, which will be described below, are shown for ease of viewing. For this reason, it is easier to understand by referring to Figs. 6 and 7 at the same time. The intersection C1 between the suction side center line L1, which passes through the center of the smallest circle (since the flow path 10 has a circular cross section, the circle has the same shape as the flow path 10) that encloses the liquid path 10 passing through the suction port 7 as viewed from the pump chamber 5 side (leftward in Figs. 6 and 7), and the shaft center line L2, which is perpendicular to the suction side center line L1 and passes through the center line 19c of the drive shaft 19a (perpendicular to the paper surface of Figs. 6 and 7) and the center line 21c of the driven shaft 21a (perpendicular to the paper surface of Figs. 6 and 7), is located closer to the center of the drive shaft 19 (or closer to the center of the driven shaft 21) than the midpoint C2 between the center line 19c of the drive shaft 19 and the center line 21c of the driven shaft 21. In other words, it is offset toward the drive gear 19 or the driven gear 21. In other words, although not limited to this relationship, when the diameter of the above-mentioned minimum circle is R, the distance D between the midpoint C2 and the intersection point C1 (the distance between the suction side center line L1 and the center of the discharge port 9 and the intersection point C2) is Center of discharge sideIt has become clear that more efficient liquid suction can be achieved by setting the following relationship for the distance between the nozzle and line L3: R / 2≦D≦R

[0033] When the motor 15 is energized and rotates, the drive shaft 17 to which the rotation is transmitted rotates the drive gear 19 in a predetermined direction. The driven gear 21 meshing with the drive gear 19 also rotates, and the drive gear 19 rotates in the drive gear chamber 5a of the pump chamber 5, and the driven gear 21 rotates in the driven gear chamber 5b, generating negative pressure in the triangular area 5c of the pump chamber 5, and sucking in the liquid shown by the arrow in FIG. 5 from the flow path 10 in the suction port 7. Since the suction port 7 is offset to the drive shaft 19 side, the negative pressure on the drive gear chamber 5a side is larger than the negative pressure on the driven gear chamber 5b, that is, the negative pressure becomes unbalanced. Although the detailed causal relationship is still being elucidated, it is presumed that this is the reason for the increased suction force compared to conventional gear pumps in which the two are balanced. If R / 2>D, the degree of negative pressure imbalance is not large enough, while if D>R, the negative pressure on the non-offset side becomes too small, which may cause inconvenience in driving without priming.

[0034] (Example) The number of teeth of the driving gear 19 used in the gear pump 1 is 10, and the number of teeth of the driven gear 21 is also 10, and the diameter of the tooth tip circle of both is 12.5 mm. The diameter of the flow passage 10 in the suction port 7 is 3.0 mm (therefore, the above-mentioned diameter R (FIG. 7) is also 3.0 mm), and the diameter of the flow passage 10 in the discharge port 9 is 4.0 mm. This gear pump 1 was tested in comparison with a conventional gear pump (not shown) that does not have an offset suction port using the device shown in FIG. 8. The test involved measuring the height that the gear pump vertically sucked up from the water surface in the water tank 113 through the pipe P. The pipe P was a polyvinyl chloride pipe manufactured by Sanyo Chemical Industries, with an outer diameter of 8.0 mm and an inner diameter of 6.0 mm, and was used in a state where it was upright on an upright stand.

[0035] (Consideration) The experimental results are shown in the table of Figure 8. In experiment 1, a gear pump with both suction and discharge in the center was used, in experiment 2, a gear pump with only the suction offset was used, and in experiment 3, a gear pump with both the suction and discharge offset was used. The gear pump used in experiments 2 and 3 was the gear pump of the present invention. The results are the average of three experiments each. In all cases, the inside of the gear pump was sufficiently air-blowed before the suction experiment to make it as dry as possible, i.e., without the presence of priming water.

[0036] The suction height H in experiment 1 was about 400 mm. In contrast, the suction height H in experiments 2 and 3 was about 1700 mm. This shows the advantage of the offset of the suction port. It is clear that offsetting the discharge port also provided good results. In the experiments with the gear pump according to this embodiment, priming was not necessary. Also, from Experiments 2 and 3, it was found that there was almost no difference between when the discharge port was located in the center and when it was offset. This also showed that offsetting the suction port side was important for improving the suction height. [Explanation of symbols]

[0037] 1 gear pump, 3 housing, 3a housing body, 3b mounting portion, 3c rear wall, 3d annular rib, 5 pump chamber, 5a drive gear chamber, 5b driven gear chamber, 5c triangular area, 5d sector area, 5d pump chamber peripheral wall, 7 suction port, 9 discharge port, 10 liquid path, 11 cover, 13 bracket, 13a motor support portion, 13b flange portion, 15 motor, 17 drive shaft, 19 drive gear, 19a drive shaft, 21 driven gear, 21a driven shaft, 23 slider, 23a drive hole, 23b driven hole, 23c triangular area, 23d sector area, 25 slider, 25a drive hole, 25b driven hole, 27 X ring, 29 bearing, 31 O ring, 33 screw, 35 screw, 101 Cup type vending machine, L1 suction side center line, L2 shaft center line, L3 discharge side center line, C1 intersection, C2 midpoint, D distance, 101 Cup type vending machine, L1 suction side center line, L2 shaft center line, L3 discharge side center line, C1 intersection, C2 midpoint, D distance

Claims

1. a gear pump including a drive shaft that rotates by the driving force of a drive source, a drive gear connected to rotate integrally with the drive shaft, a driven gear connected to rotate integrally with or around a driven shaft by meshing with the drive gear, and a housing in which a pump chamber is formed in which the drive gear and the driven gear are housed, the gear pump conveying fluid sucked in from a suction port by the rotation of the drive gear and the driven gear separately to a drive gear side and a driven gear side, and the fluids are joined just before a discharge port and discharged from the discharge port, The drive gear and the driven gear are accommodated in the pump chamber in a sandwich state in which they can rotate while being in contact with each other, with the slider on one side of the thickness direction of the drive gear and the slider on the other side of the thickness direction of the drive gear being in mesh with each other, the suction port and the discharge port are provided protruding from the housing in a direction perpendicular to a thickness direction of the drive gear or the driven gear, The suction port is offset toward the driving gear side or the driven gear side. A gear pump characterized by:

2. a gear pump including a drive shaft that rotates by the driving force of a drive source, a drive gear connected to rotate integrally with the drive shaft, a driven gear connected to rotate integrally with or around a driven shaft by meshing with the drive gear, and a housing in which a pump chamber is formed in which the drive gear and the driven gear are housed, the gear pump conveying liquid sucked in from a suction port by the rotation of the drive gear and the driven gear separately to a drive gear side and a driven gear side, and the liquids are joined just before a discharge port and discharged from the discharge port, The drive gear and the driven gear are accommodated in the pump chamber in a sandwich state in which they can rotate while being in contact with each other, with the slider on one side of the thickness direction of the drive gear and the slider on the other side of the thickness direction of the drive gear being in mesh with each other, the suction port and the discharge port are provided protruding in opposite directions from each other as seen from the housing, an intersection point between an intake side center line that passes orthogonally through the center of the smallest circle that encloses the liquid path passing through the intake port as viewed from the pump chamber side and an axis center line that is orthogonal to the intake side center line and passes orthogonally through the center line of the drive shaft and the center line of the driven shaft is located closer to the center of the drive shaft or closer to the center of the driven shaft than a midpoint between the center line of the drive shaft and the center line of the driven shaft; A gear pump characterized by:

3. a gear pump including a drive shaft that rotates by the driving force of a drive source, a drive gear connected to rotate integrally with the drive shaft, a driven gear connected to rotate integrally with or around a driven shaft by meshing with the drive gear, and a housing in which a pump chamber is formed in which the drive gear and the driven gear are housed, the gear pump conveying fluid sucked in from a suction port by the rotation of the drive gear and the driven gear separately to a drive gear side and a driven gear side, and the fluids are joined just before a discharge port and discharged from the discharge port, The drive gear and the driven gear are accommodated in the pump chamber in a sandwich state in which they can rotate while being in contact with each other, with the slider on one side of the thickness direction of the drive gear and the slider on the other side of the thickness direction of the drive gear being in mesh with each other, the suction port and the discharge port are provided protruding from the housing in a direction perpendicular to a thickness direction of the drive gear or the driven gear, respectively, and only the suction port of the suction port and the discharge port is offset toward the drive gear or the driven gear. A gear pump characterized by:

4. a gear pump including a drive shaft that rotates by the driving force of a drive source, a drive gear connected to rotate integrally with the drive shaft, a driven gear connected to rotate integrally with or around a driven shaft by meshing with the drive gear, and a housing in which a pump chamber is formed in which the drive gear and the driven gear are housed, the gear pump conveying liquid sucked in from a suction port by the rotation of the drive gear and the driven gear separately to a drive gear side and a driven gear side, and the liquids are joined just before a discharge port and discharged from the discharge port, The drive gear and the driven gear are accommodated in the pump chamber in a sandwich state in which they can rotate while being in contact with each other, with the slider on one side of the thickness direction of the drive gear and the slider on the other side of the thickness direction of the drive gear being in mesh with each other, the suction port and the discharge port are provided protruding in opposite directions from each other as seen from the housing, The suction port is offset toward the driving gear side or the driven gear side. A gear pump characterized by:

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