Plunger pump and paint supply device

Abstract

To provide a plunger pump capable of reducing pulsation during continuous discharge despite having a relatively simple configuration.SOLUTION: A plunger pump 11 causes a plunger 31 to reciprocate axially while rotating relative to a cylinder chamber 21. Suction ports 22, 24 and discharge ports 23, 25 are alternately connected to the cylinder chamber 21 to transfer fluid. A plurality of cutouts 41, 42 are formed at different positions on the outer surface of the plunger 31, and a plurality of liquid delivery parts 43, 44 are formed corresponding to them. While one of the plurality of liquid delivery part 43, 44 is connected to the discharge ports 23, 25 to discharge fluid, the others are connected to the suction ports 22, 24 to suction fluid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a valveless plunger pump and a paint supply device using the same. [Background technology]

[0002] Conventionally, devices known as plunger pumps have been known as a means for transferring fluids such as paints and cleaning fluids to coating machines and the like, and in recent years, valveless plunger pumps that do not include a valve have been proposed (see, for example, Patent Documents 1 and 2). This type of plunger pump has a configuration in which a plunger is inserted into a cylinder chamber of a cylinder, and a notch that serves as a fluid delivery section is formed in the plunger. During use, the plunger is rotated relative to the cylinder chamber while reciprocating axially. As a result of this rotational reciprocating movement, fluid is sucked in through communication between the fluid delivery section and the suction port, and discharged through communication between the fluid delivery section and the discharge port, thereby transferring the fluid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2931900 [Patent Document 2] Patent No. 5128415 [Patent Document 3] Patent No. 4230081 [Patent Document 4] Japanese Patent Application Publication No. 57-124079 Summary of the Invention [Problem to be solved by the invention]

[0004] While this type of plunger pump has the advantage of being capable of highly accurate liquid transfer, it has the disadvantage of generating pulsation during continuous discharge because its structure does not allow for simultaneous suction and discharge of fluid. In light of this pulsation problem, various valveless plunger pumps have been proposed (see, for example, Patent Documents 3 and 4). Patent Document 3 discloses a technology for reducing pulsation by arranging two pumps in parallel and having each perform the opposite actions of suction and discharge. Patent Document 4 discloses a technology for reducing pulsation by arranging two plungers in parallel in one cylinder and having each perform the opposite actions of suction and discharge.

[0005] However, the conventional devices of Patent Documents 3 and 4 have drawbacks such as a complicated device configuration, as well as unavoidable increases in size, weight, and cost of the device.

[0006] The present invention has been made in view of the above-mentioned problems, and its object is to provide a plunger pump that can reduce pulsation during continuous discharge despite having a relatively simple configuration, and a paint supply device using the same. [Means for solving the problem]

[0007] In order to solve the above problems, the invention described in Means 1 is a valveless plunger pump comprising: a cylinder having an internal cylinder chamber, and having an inlet and an outlet formed therein that communicate between the cylinder chamber and the outer surface of the cylinder; and a plunger having a drive unit on one end side protruding from the cylinder, and having a notch formed on the outer peripheral surface thereof, the plunger being inserted into the cylinder chamber with the outer peripheral surface in sliding contact with the inner surface of the cylinder; the plunger being caused to rotate relative to the cylinder chamber while being caused to reciprocate in the axial direction, thereby alternately connecting the inlet and the outlet to the cylinder chamber to transfer a fluid; a plurality of the notches are formed at different positions on the outer peripheral surface of the plunger, and a plurality of liquid delivery sections are formed corresponding to the plurality of notches; one of the plurality of liquid delivery sections is connected to the outlet port to perform a fluid delivery operation, while the others are connected to the suction port to perform a fluid delivery operation.

[0008] Therefore, according to the invention described in Means 1, while one of the multiple liquid delivery units formed in the cylinder chamber is performing a fluid delivery operation, the others are performing a fluid suction operation. This shortens the period during which delivery is interrupted, making it easier to maintain continuity of delivery. Therefore, unlike conventional devices having only one liquid delivery unit in the cylinder chamber, pulsation during continuous delivery can be reduced. In addition, by forming multiple notches at different positions on the outer circumferential surface of the plunger, multiple liquid delivery units are provided in the cylinder chamber, making it possible to create a device with a relatively simple configuration.

[0009] The invention described in Means 2 is summarized as follows: in Means 1, the plurality of notches are second notches formed in the outer peripheral surface of the plunger at an end opposite to the drive unit, and first notches formed in the outer peripheral surface of the plunger at a position axially spaced from the second notches, the portion of the plunger closer to the drive unit than the first notches is a first small diameter shaft portion, and a first insertion portion having a smaller diameter than the cylinder chamber is formed on the drive unit side of the cylinder chamber, and the first small diameter shaft portion is inserted into the first insertion portion. Therefore, with this configuration, by forming the first small diameter shaft portion on the plunger, a space is also formed on the drive unit side of the first notch, so that the liquid delivery portion formed corresponding to the first notch can be made larger.

[0010] The invention described in Measure 3 is characterized in that the volume of the first liquid delivery section formed corresponding to the first notch is equal to the volume of the second liquid delivery section formed corresponding to the second notch in Measure 2 or 3. Therefore, with this configuration, the difference in the volume fluctuation amount of the multiple liquid delivery sections is eliminated, and as a result, it is possible to further reduce pulsation during continuous discharge.

[0011] The invention described in means 4 is summarized as follows: in means 2, a second small diameter shaft portion is formed by extending from the end of the plunger opposite the drive portion, and a second insertion portion having a diameter smaller than that of the cylinder chamber is formed at a position opposite the drive portion in the cylinder chamber, and the second small diameter shaft portion is inserted into the second insertion portion. Therefore, with this configuration, it is relatively easy to form liquid delivery portions of the same volume at both ends of the plunger, and it is relatively easy to eliminate differences in volume fluctuations among multiple liquid delivery portions.

[0012] The invention described in Measure 5 is characterized in that the volume of the first liquid delivery section formed corresponding to the first notch is equal to the volume of the second liquid delivery section formed corresponding to the second notch in Measure 4. Therefore, with this configuration, the difference in the volume fluctuation amount of the multiple liquid delivery sections is eliminated, and as a result, it is possible to further reduce pulsation during continuous discharge.

[0013] The gist of the invention described in means 6 is a paint supply device configured to include one or more plunger pumps described in any one of means 1 to 5. [Effects of the Invention]

[0014] As described above in detail, according to the inventions described in claims 1 to 6, it is possible to provide a plunger pump that can reduce pulsation during continuous discharge despite having a relatively simple configuration, and a paint supply device using the same. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic view showing an installation state of a plunger pump according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a vertical cross-sectional view of a plunger pump according to a first embodiment. [Figure 3] 3A is a perspective view of a plunger constituting the plunger pump of the first embodiment, FIG. 3B is a cross-sectional view taken along line AA in FIG. 2, and FIG. 3C is a cross-sectional view taken along line BB in FIG. [Figure 4] 5(a) to 5(f) are schematic diagrams illustrating the operation of the plunger pump of the first embodiment. [Figure 5] 5(a) to 5(f) are schematic diagrams illustrating the operation of the plunger pump of the first embodiment. [Figure 6] FIG. 6 is a longitudinal sectional view of a plunger pump according to a second embodiment. [Figure 7] 7A is a perspective view of a plunger constituting a plunger pump of a second embodiment, FIG. 7B is a cross-sectional view taken along line CC in FIG. 6, and FIG. 7C is a cross-sectional view taken along line DD in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] [First embodiment]

[0017] A plunger pump 11 according to a first embodiment of the present invention will now be described in detail with reference to FIGS.

[0018] FIG. 1 is a schematic diagram showing a plunger pump 11 according to this embodiment installed on a painting robot R1. The painting robot R1 is installed in a painting booth used, for example, to paint automobiles. A paint sprayer 1, which atomizes and sprays paint, is supported at the tip of an arm 2 of the painting robot R1. A paint supply device 5 is installed in the painting booth. The paint supply device 5 includes a paint supply device main body 4 installed near the painting robot R1 and a plunger pump 11 installed midway along the arm 2. The paint supply device main body 4 is configured, for example, as a valve manifold with multiple color change valves connected to multiple paint tanks. A flow path 6 is formed in the arm 2 of the painting robot R1, and this flow path 6 connects the paint supply device main body 4 to the plunger pump 11 and the plunger pump 11 to the painting device 1. Therefore, when this flow path 6 is open, paint is supplied to the painting device 1 via the paint supply device main body 4 and the plunger pump 11.

[0019] The plunger pump 11 of this embodiment is a valveless type plunger pump configured without a valve body, and is a device for transferring paint supplied from the paint supply device main body 4 side to the sprayer 1 side. FIG. 2 is a vertical cross-sectional view showing the plunger pump 11 of this embodiment. This plunger pump 11 includes a cylinder 12, a plunger 31, and a motor M1 as a driving means. FIG. 3(a) is a perspective view of the plunger 31 that constitutes the plunger pump 11, FIG. 3(b) is a cross-sectional view taken along line AA in FIG. 2, and FIG. 3(c) is a cross-sectional view taken along line BB in FIG. 2.

[0020] As shown in Figure 2, the cylinder 12 constituting the plunger pump 11 is a vertically elongated member with a rectangular cross section formed by multiple metal members (upper end plate 12c, upper block 12d, lower block 12e, and lower end plate 12f). The upper end plate 12c and the upper block 12d are joined together, and a seal member is provided at the joint. The upper block 12d and the lower block 12e are joined together, and a seal member is also provided at the joint. The lower block 12e and the lower end plate 12f are joined together, and a seal member is also provided at the joint.

[0021] The cylinder 12 has a cylinder chamber 21 with a circular cross section inside. The cylinder chamber 21 is formed to extend along the longitudinal direction of the cylinder 12. In this embodiment, the lower end plate 12f does not have any particular hole formed therein, so the lower end of the cylinder 12 is closed. On the other hand, the upper end plate 12c has a first insertion portion 53, which is a hole, formed in the center thereof, so the upper end of the cylinder 12 is open.

[0022] A first suction port 22 and a first discharge port 23 are formed in the cylinder 12 at a position above the vertical center, i.e., in the upper block 12d constituting the cylinder 12, so as to penetrate the wall of the cylinder 12. The first suction port 22 and the first discharge port 23 face each other across the cylinder chamber 21 (see FIG. 3(b)), and both connect the cylinder chamber 21 to the cylinder outer surface 12a. A second suction port 24 and a second discharge port 25 are formed in the cylinder 12 at a position below the vertical center, i.e., in the lower block 12e constituting the cylinder 12, so as to penetrate the wall of the cylinder 12. The second suction port 24 and the second discharge port 25 face each other across the cylinder chamber 21 (see FIG. 3(c)), and both connect the cylinder chamber 21 to the cylinder outer surface 12a. The first suction port 22 and the second suction port 24 are connected to the flow path 6 on the paint supply device main body 4 side. The first discharge port 23 and the second discharge port 25 are connected to the flow path 6 on the coater 1 side.

[0023] As shown in FIG. 3(a) and other figures, the plunger 31 is a round-bar-shaped member made of a ceramic material (i.e., a highly slidable material) such as alumina. The plunger 31 is inserted into the cylinder chamber 21 of the cylinder 12 with its outer peripheral surface 31a in sliding contact with the cylinder inner surface 12b. That is, to allow the outer peripheral surface 31a of the plunger 31 to be in sliding contact with the cylinder inner surface 12b, the outer diameter of the plunger 31 is set to be essentially equal to the inner diameter of the cylinder chamber 21. The plunger 31 has an upper end T1 and a lower end T2. Almost the entire area of ​​the plunger 31, including the lower end T2, is disposed within the cylinder chamber 21, while the upper end T1 protrudes outside the cylinder chamber 21. The upper end T1 of the plunger 31 is provided with a drive unit 32.

[0024] As shown in FIG. 1 , a motor M1 is drivingly connected to the drive unit 32. The motor M1 generates a driving force for reciprocating the plunger 31 axially while rotating it relative to the cylinder chamber 21. In this embodiment, a servo motor or the like is used. A connecting jig 15, which rotates integrally with the motor M1 when driven, is attached to the output shaft 14 of the motor M1. The drive unit 32 of the plunger 31 is inserted into a hole in the connecting jig 15. The connecting jig 15 and the output shaft 14 of the motor M1 are arranged at a slight incline with respect to the axial direction of the plunger 31. A groove 16 is formed on the inner circumferential surface of the hole in the connecting jig 15, and a protrusion 33 protruding from the circumferential surface of the drive unit 32 is disposed in the groove 16. Therefore, when the motor M1 is driven, the protrusion 33 is guided by the groove 16 of the connecting jig 15, causing the plunger 31 to reciprocate axially while rotating.

[0025] As shown in FIGS. 2 and 3(a) to 3(c), the plunger 31 of this embodiment has a plurality of cutouts, specifically, two cutouts (a first cutout 41 and a second cutout 42). The first cutout 41 and the second cutout 42 are formed at different positions on the outer peripheral surface 31a of the plunger 31, more specifically, at two positions spaced apart along the axial direction of the plunger 31. The second cutout 42 is formed by cutting away a portion of the outer peripheral surface 31a of the plunger 31 at the lower end T2, i.e., the end opposite the drive unit 32. The first cutout 41 is formed by removing a portion of the outer peripheral surface 31a of the plunger 31 at a position spaced apart from the second cutout 42 in the axial direction. The first cutout 41 and the second cutout 42 are rotated 180° relative to each other with respect to the central axis of the plunger 31. The depth and length of the first cutout portion 41 and the second cutout portion 42 are not particularly limited and can be set arbitrarily, but in this embodiment, for example, the cutouts are made to approximately the same depth and length.

[0026] The plunger 31 has a first small-diameter shaft portion 51 formed thinner than the other portions at a portion closer to the drive unit than the first notch 41. The outer diameter of the first small-diameter shaft portion 51 is set to be 50% or more, preferably 60% or more, and more preferably 70% or more of the outer diameter of the thick portion in order to maintain the strength of the plunger 31. The first small-diameter shaft portion 51 may be formed integrally with or separately from the thick portion of the plunger 31, but here it is formed integrally. Furthermore, a first insertion portion 53 having a smaller diameter than the cylinder chamber 21 is formed in the cylinder 12 on the drive unit 32 side of the cylinder chamber 21, in other words, in the upper end center portion of the upper block 12d that constitutes the cylinder 12. The first small-diameter shaft portion 51 of the plunger 31 is inserted into this first insertion portion 53.

[0027] As shown in FIG. 2 and other figures, a plurality of liquid delivery sections are formed inside the cylinder 12 corresponding to the plurality of cutouts. In this embodiment, a first liquid delivery section 43 is formed corresponding to the first cutout 41, and a second liquid delivery section 44 is formed corresponding to the second cutout 42. More specifically, the first cutout 41 is disposed inside the upper block 12d, and the space defined by the surface of the first cutout 41, the surface of the first small-diameter shaft section 51, and the inner surface of the upper block 12d functions as the first liquid delivery section 43. The second cutout 42 is disposed inside the lower block 12e, and the space defined by the surface of the second cutout 42 and the inner surface of the lower block 12e functions as the second liquid delivery section 44. The volumes of the first liquid delivery section 43 and the second liquid delivery section 44 increase or decrease depending on the rotational position of the plunger 31. The maximum volumes of the first liquid delivery section 43 and the second liquid delivery section 44 are not particularly limited and can be set arbitrarily, but in this embodiment, the second liquid delivery section 44 is set to be slightly larger than the first liquid delivery section 43. Of course, the maximum volumes of the first liquid delivery section 43 and the second liquid delivery section 44 may also be set to be equal.

[0028] The first liquid delivery unit 43 can be connected to either the first suction port 22 or the first discharge port 23 formed in the upper block 12d, depending on the rotational position of the plunger 31. For example, when the first liquid delivery unit 43 is connected to the first suction port 22, the first liquid delivery unit 43 is not connected to the first discharge port 23. Conversely, when the first liquid delivery unit 43 is connected to the first discharge port 23, the first liquid delivery unit 43 is not connected to the first suction port 22. In other words, the first liquid delivery unit 43 is not connected to both the first suction port 22 and the first discharge port 23. However, when the plunger 31 is in a specific rotational position, the first liquid delivery unit 43 may be not connected to both the first suction port 22 and the first discharge port 23.

[0029] Meanwhile, the second liquid delivery unit 44 can communicate with either the second suction port 24 or the second discharge port 25 formed in the lower block 12e, depending on the rotational position of the plunger 31. For example, when the second liquid delivery unit 44 and the second suction port 24 are in communication with each other, the second liquid delivery unit 44 and the second discharge port 25 are not in communication with each other. Conversely, when the second liquid delivery unit 44 and the second discharge port 25 are in communication with each other, the second liquid delivery unit 44 and the second suction port 24 are not in communication with each other. In other words, the second liquid delivery unit 44 is not in communication with both the second suction port 24 and the second discharge port 25. However, when the plunger 31 is in a specific rotational position, the second liquid delivery unit 44 may be in communication with both the second suction port 24 and the second discharge port 25.

[0030] Next, the operation of the plunger pump 11 of this embodiment configured as described above will be described. FIGS. 4(a) to 4(f) are schematic diagrams showing a sequence for explaining the operation of the plunger pump 11, and FIGS. 5(a) to 5(f) are schematic diagrams showing a sequence for explaining the operation following the state shown in FIG. 4(f). In each of the above figures, the upper part is a vertical cross-sectional view showing the plunger pump 11. The middle part is a schematic cross-sectional view when the plunger pump 11 is cut at a height position where the first suction port 22 and the first discharge port 23 are located. The lower part is a schematic cross-sectional view when the plunger pump 11 is cut at a height position where the second suction port 24 and the second discharge port 25 are located. Note that hatching has been intentionally omitted from these figures.

[0031] The plunger pump 11 of this embodiment transfers paint by alternately connecting the suction port and the discharge port to the cylinder chamber 21 by rotating the plunger 31 relative to the cylinder chamber 21 while reciprocating in the axial direction. This device is particularly configured so that while one of the two liquid delivery sections is connected to the discharge port and performs a paint discharge operation, the other is connected to the suction port and performs a fluid suction operation. This will be described in detail below with reference to Figures 4(a) to 4(f) and 5(a) to 5(f).

[0032] In the initial state shown in Figure 4(a), the plunger 31 is fully recessed within the cylinder 12. At this time, the plunger 31 is defined as being at the "0° rotation position." The first liquid delivery section 43 holds paint therein (see the blackened area in the figure) and is not connected to either the first suction port 22 or the first discharge port 23. The second liquid delivery section 44 does not hold paint therein and is not connected to either the first suction port 22 or the first discharge port 23.

[0033] FIG. 4(b) shows the state in which the plunger 31 has moved to a 30° rotation position and slightly moved upward. At this time, the first liquid supply section 43 is not in communication with the first suction port 22 but is in communication with the first discharge port 23. The volume of the first liquid supply section 43 decreases slightly as the rotation position changes, so that paint is pushed out of the first liquid supply section 43 and begins to be discharged into the flow path 6 via the first discharge port 23. The second liquid supply section 44 is not in communication with the second discharge port 25 but is in communication with the second suction port 24. The volume of the second liquid supply section 44 increases slightly as the rotation position changes. Therefore, paint can be sucked into the second liquid supply section 44.

[0034] FIG. 4(c) shows the state in which the plunger 31 has moved to a 60° rotation position and then moved slightly upward. At this time, the first liquid supply section 43 maintains communication with the first suction port 22, causing paint to be discharged into the flow path 6 through the first discharge port 23. The volume of the second liquid supply section 44 increases slightly as the rotation position changes, causing paint to begin to be sucked into the interior through the second suction port 24. FIG. 4(d) shows the state in which the plunger 31 has moved to a 90° rotation position, FIG. 4(e) shows the state in which the plunger 31 has moved to a 120° rotation position, and FIG. 4(f) shows the state in which the plunger 31 has moved to a 150° rotation position. At these rotation positions, the suction and discharge operations continue essentially as described above.

[0035] In Figure 5(a), the plunger 31 has rotated 180 degrees and reached the position where it protrudes furthest from the cylinder 12. At this time, the first liquid delivery section 43, which has reached its maximum volume, holds paint therein and is no longer in communication with either the first suction port 22 or the first discharge port 23. On the other hand, the second liquid delivery section 44, which has reached its minimum volume, does not hold paint therein and is no longer in communication with either the first suction port 22 or the first discharge port 23. After this, the plunger 31 begins to move in the opposite direction (i.e., downward).

[0036] FIG. 5(b) shows the state in which the plunger 31 has moved to a rotational position of 210° and slightly moved downward. At this time, the second liquid supply section 44 is not in communication with the second suction port 24 but is in communication with the second discharge port 25. The volume of the second liquid supply section 44 decreases slightly as the rotational position changes, so that the paint is pushed out of the second liquid supply section 44 and begins to be discharged into the flow path 6 via the second discharge port 25. The first liquid supply section 43 is not in communication with the first discharge port 23 but is in communication with the first suction port 22. The volume of the first liquid supply section 43 increases slightly as the rotational position changes. Therefore, the first liquid supply section 43 is ready to draw paint.

[0037] FIG. 5(c) shows the state in which the plunger 31 has moved to the 240° rotation position and then slightly moved downward. At this time, the second liquid supply section 44 maintains communication with the second suction port 24, and paint is discharged into the flow path 6 through the second discharge port 25. The volume of the first liquid supply section 43 increases slightly with the change in rotation position, and paint begins to be sucked into the interior through the first suction port 22. FIG. 5(d) shows the state in which the plunger 31 has moved to the 270° rotation position, FIG. 5(e) shows the state in which the plunger 31 has moved to the 300° rotation position, and FIG. 5(f) shows the state in which the plunger 31 has moved to the 330° rotation position. At these rotation positions, the suction and discharge operations are essentially the same as those described above. The plunger 31 then returns to its initial state, the 0° rotation position.

[0038] Therefore, according to this embodiment, the following effects can be obtained.

[0039] (1) In the plunger pump 11 of this embodiment, the plunger 31 is caused to rotate relative to the cylinder chamber 21 while being reciprocated in the axial direction, thereby alternately connecting the suction ports (first suction port 22, second suction port 24) and the discharge ports (first discharge port 23, second discharge port 25) to the cylinder chamber 21 to transfer paint. Two notches (first notch 41 and second notch 42) are formed at different positions on the outer circumferential surface 31a of the plunger 31. A first liquid supply section 43 is formed corresponding to the first notch 41, and a second liquid supply section 44 is formed corresponding to the second notch 42.

[0040] Therefore, with the configuration of this plunger pump 11, while the first liquid supply section 43 formed within the cylinder chamber 21 discharges paint, the second liquid supply section 44 performs a paint suction operation. Furthermore, while the second liquid supply section 44 discharges paint, the first liquid supply section 43 performs a paint suction operation. This shortens the period during which discharge is interrupted, making it easier to maintain continuity of discharge. Therefore, unlike conventional devices having only one liquid supply section within the cylinder chamber 21, pulsation during continuous discharge can be reduced. Furthermore, by forming the first notch 41 and the second notch 42 at two different positions on the outer circumferential surface 31a of the plunger 31, the first liquid supply section 43 and the second liquid supply section 44 are formed within the cylinder chamber 21. This configuration eliminates the need for two pumps arranged in parallel, as in the device of Patent Document 3, and also eliminates the need for two plungers arranged in parallel in one cylinder, as in the device of Patent Document 4. Therefore, the device can be configured more simply than the prior art. Furthermore, according to this embodiment, a plunger pump 11 with a relatively simple configuration is realized, which facilitates miniaturization, weight reduction, and cost reduction of the device. When the plunger pump 11 of this embodiment is installed in the painting robot R1 shown in Fig. 1, paint is continuously supplied to the paint sprayer 1, which makes it possible to improve the painting quality. Furthermore, because this plunger pump 11 is lightweight and small, it is possible to improve the operability of the painting robot R1.

[0041] (2) In the plunger pump 11 of this embodiment, the portion of the plunger 31 closer to the drive unit 32 than the first notch 41 is the first small-diameter shaft portion 51. A first insertion portion 53 having a smaller diameter than the cylinder chamber 21 is formed on the drive unit 32 side of the cylinder chamber 21, and the first small-diameter shaft portion 51 is inserted into the first insertion portion 53. If the first notch 41 and the second notch 42 were formed with the same size without forming the small-diameter first insertion portion 53, the maximum volume of the first liquid delivery portion 43 would be smaller than the maximum volume of the second liquid delivery portion 43. To increase the maximum volume of the first liquid delivery portion 43 without forming the small-diameter first insertion portion 53, for example, it would be necessary to form the first notch 41 longer or deeper. However, forming the first notch 41 in this manner would result in disadvantages such as a decrease in the strength of the plunger 31 at the location of the first notch 41 or uneven sliding resistance. According to the configuration of this embodiment, the formation of the small-diameter first small-diameter shaft portion 51 also creates a space in the region of the first cutout portion 41 on the drive unit 32 side. Therefore, the maximum volume of the first liquid delivery portion 43 can be increased without causing the above-mentioned inconvenience.

[0042] [Second embodiment] A plunger pump 11A according to a second embodiment of the present invention will be described in detail below with reference to FIGS. 6 and 7. Here, configurations different from those of the first embodiment will be described, while configurations common to those of the first embodiment will be assigned the same component numbers and will not be described again. FIG. 6 is a vertical cross-sectional view showing the plunger pump 11A of this embodiment. FIG. 7(a) is a perspective view of a plunger 31A constituting the plunger pump 11A, FIG. 7(b) is a cross-sectional view taken along line CC in FIG. 6, and FIG. 7(c) is a cross-sectional view taken along line DD in FIG. 6.

[0043] While the plunger pump 11 of the first embodiment had only one structural portion where the first small diameter shaft portion 51 was inserted into the first insertion portion 53, the plunger pump 11A of the present embodiment differs in that it has such structural portions in two locations. A second small diameter shaft portion 52 is extended from the lower end portion T2 of the plunger 31A, i.e., the end opposite the drive portion 32. Here, the outer diameter of the second small diameter shaft portion 52 is set to be equal to the outer diameter of the first small diameter shaft portion 51. A second insertion portion 54 having a diameter smaller than that of the cylinder chamber 21 (the same diameter as the first insertion portion 53) is formed in the center of the lower end plate 12f that constitutes the lower end of the cylinder 12. The second small diameter shaft portion 52 is slidably inserted into this second insertion portion 54. Furthermore, the maximum volume of the first liquid supply section 43 formed corresponding to the first cutout section 41 and the maximum volume of the second liquid supply section 44 formed corresponding to the second cutout section 42 are approximately equal.

[0044] The plunger pump 11A configured in this manner, like the first embodiment, can reduce pulsation during continuous discharge despite its relatively simple configuration. Furthermore, in this embodiment, the maximum volume of the first liquid delivery section 43 and the maximum volume of the second liquid delivery section 44 are equal, eliminating the difference in volume fluctuation between the first liquid delivery section 43 and the second liquid delivery section 44, thereby further reducing pulsation during continuous discharge. Furthermore, the configuration of this embodiment makes it relatively easy to form liquid delivery sections (the first liquid delivery section 43 and the second liquid delivery section 44) with the same volume at both ends of the plunger 31A. This has the advantage of being relatively easy to eliminate the difference in volume fluctuation between the two liquid delivery sections.

[0045] Each embodiment of the present invention may be modified as follows.

[0046] In the above embodiment, two notches are formed at two different positions on the outer circumferential surface 31a of the plunger 31, 31A, and two liquid delivery sections are formed corresponding to the notches, but this is not limiting. In another embodiment, for example, three or more notches may be formed at three or more different positions on the outer circumferential surface 31a of the plunger 31, 31A, and three or more liquid delivery sections may be formed corresponding to the notches.

[0047] In the above embodiment, the plungers 31, 31A are driven using a driving means configured to include the motor M1, but this is not limiting. In another embodiment, the plungers 31, 31A may be driven using a driving means configured to include a torque generating device other than the motor M1.

[0048] In the above embodiment, the paint supply device 5 is configured to include one plunger pump 11, 11A, but is not limited to this. In another embodiment, the paint supply device 5 may be configured to include two or more plunger pumps 11, 11A.

[0049] In the above embodiment, the plunger pumps 11, 11A are applied to the paint supply device 5, but the present invention is not limited to this. In other embodiments, the plunger pumps 11, 11A may be applied to devices other than the paint supply device 5, such as a paint washing device or a paint refilling device. Furthermore, the plunger pumps 11, 11A may be applied to devices for continuously supplying fluids other than paint.

[0050] 5: Paint supply device 11, 11A: Plunger pump 12: Cylinder 12a: Cylinder outer surface 12b: Cylinder inner surface 21: Cylinder chamber 22, 24: Intake port 23, 25: Discharge port 31, 31A: Plunger 31a: Outer surface 32: Drive unit 41: (1st) Notch 42: (Second) Notch 43: (First) Liquid delivery section 44: (Second) Liquid Delivery Section 51: First small diameter shaft 52: Second small diameter shaft 53: First insertion part 54: Second insertion part T1: Top end as end T2: Lower end as end

Claims

1. a cylinder having a cylinder chamber therein, and a suction port and a discharge port formed therein, the suction port and the discharge port communicating with the cylinder chamber and an outer surface of the cylinder; a plunger having a drive portion on one end side protruding from the cylinder, a notch formed on the outer peripheral surface, and inserted into the cylinder chamber with the outer peripheral surface in sliding contact with the inner surface of the cylinder; a valveless plunger pump that transfers a fluid by alternately connecting the suction port and the discharge port to the cylinder chamber by causing the plunger to reciprocate in an axial direction while rotating relative to the cylinder chamber, a plurality of the notches are formed at different positions on the outer circumferential surface of the plunger, and a plurality of liquid delivery portions are formed corresponding to the plurality of notches, One of the plurality of liquid delivery units is connected to the discharge port to perform a fluid discharge operation, while the other liquid delivery units are connected to the suction port to perform a fluid suction operation. A plunger pump characterized by:

2. the plurality of notches include second notches formed on an outer peripheral surface of the plunger at an end opposite to the drive portion, and first notches formed on an outer peripheral surface of the plunger at a position spaced apart from the second notches in the axial direction, a portion of the plunger closer to the drive unit than the first notch is a first small diameter shaft portion; a first insertion portion having a smaller diameter than the cylinder chamber is formed on the drive portion side of the cylinder chamber; The first small diameter shaft portion is inserted into the first insertion portion.

2. The plunger pump according to claim 1.

3. 4. The plunger pump according to claim 2, wherein a volume of the first liquid delivery section formed corresponding to the first notch is equal to a volume of the second liquid delivery section formed corresponding to the second notch.

4. a second small diameter shaft portion extending from an end of the plunger opposite to the drive portion; a second insertion portion having a smaller diameter than the cylinder chamber is formed at a position on the opposite side of the cylinder chamber from the drive portion; The second small diameter shaft portion is inserted into the second insertion portion.

3. The plunger pump according to claim 2.

5. 5. The plunger pump according to claim 4, wherein a volume of the first liquid delivery portion formed corresponding to the first notch is equal to a volume of the second liquid delivery portion formed corresponding to the second notch.

6. A paint supply device comprising one or more plunger pumps according to any one of claims 1 to 5.

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