JP2722067B2 - Low pressure plunger pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a low-pressure plunger pump using a cap seal. [Prior Art] Plunger pumps are used in various fields, and their structures are slightly different depending on the intended use. For example, a plunger pump for high pressure uses a V-packing made of a member having high hardness as a sealing member, and the sealing pressure is strong, while the injection pressure is 1.5 kg / cm ^2.
The low-pressure plunger pump of less than about uses a cap seal made of soft rubber such as neoprene rubber or viton as the sealing member.
The life of the cap seal was extended. The piston and cylinder of the plunger pump are
A ceramic material was used in terms of abrasion resistance, corrosion resistance, and the like, and a sliding surface with a seal member was a mirror surface having a center line average roughness (Ra) of about 0.1 μm in order to enhance sealing performance. [Problems of the prior art] However, in the case of a plunger pump for high pressure, as the surface roughness of a sliding surface of a piston or a cylinder with a seal member is reduced, the sealing property is improved.
In the case of a low-pressure plunger pump using a cap seal, if the surface roughness of the sliding surface is fine, the sealing property tends to be rather deteriorated. For example, when the center line average roughness (Ra) of the sliding surface is 0.1 μm as described above, there is a disadvantage that the carrier fluid leaks from the seal portion. On the other hand, if the sliding surface is rough, the cap seal tends to be worn out and the life is shortened. [Means for Solving the Problems] In view of the above, the present invention relates to a low-pressure plunger pump using a cap seal, in which at least the sliding surface of the piston or cylinder with the cap seal is formed of alumina ceramics. The center line average roughness (Ra) of the sliding surface is 0.15 to 0.4 μm, and voids are present on the sliding surface at intervals of a maximum distance of 0.2 mm or less. [Examples] Hereinafter, examples of the present invention will be described. As shown in FIG. 1, a cross section of the main part of the low-pressure plunger pump, the piston 1 is a columnar body made of alumina ceramics, and reciprocates in the direction of the arrow to send out the fluid in the cylinder 2. I have. Also,
The cylinder 2 is provided with a cap seal 3 made of soft rubber such as neoprene rubber or viton. The cap seal 3 slides on the surface of the piston 1 to perform a sealing action. In the above embodiment, the cylinder 2 is provided with the cap seal 3 so that the cap seal 3 slides on the outer wall surface of the piston 1. However, in addition, the cap seal 3 is provided on the piston 1 side. May be provided so that the cap seal 3 slides on the inner wall surface of the cylinder 2. Hereinafter, only the structure shown in FIG. 1 will be described, but the same applies to the case where the cap seal 3 slides on the inner wall surface of the cylinder 2. In the plunger pump, the sealing property and the wear resistance of the cap seal 3 are determined by the cap seal 3 of the piston 1.
The following experiment was conducted to determine the optimum surface condition, which is determined by the surface condition of the sliding surface. Experiment 1 First, a piston 1 was formed from alumina, and a surface roughness was changed in various ways. A prototype was manufactured, assembled into a plunger pump using a cap seal 3 made of Viton, and subjected to a use test under the same conditions. Properties and wear resistance of the cap seals were examined. The results are shown in Table 1. As a result of the experiment, the surface roughness (Ra) of the sliding surface of piston 1 was
If the diameter is smaller than 0.15 μm, the sealing property is poor, and in a trial of about one hour, the transported fluid leaks as water drops and thus cannot be used in practice. Conversely, when the surface roughness (Ra) of the piston 1 was larger than 0.4 μm, the wear resistance of the cap seal 3 was particularly poor. That is, the surface roughness (Ra) of the piston 1 is 0.15 to 0.4 μm.
m were excellent. Experiment 2 The surface of the piston 1 made of alumina ceramics has a plurality of voids 1a as shown in FIG. 2 and a substantially flat surface 1b between the voids 1a. It was found that the distribution state of the void 1a was related to the sealing property. Therefore, the center line average roughness (Ra) of the sliding surface is 0.15 to 0.4.
The maximum distance r between the voids 1a adjacent to the sliding surface of the piston 1 in the range of μm was measured, and a sealing test was conducted by performing a use test in the same manner as the test 1. The smaller the maximum distance r between the adjacent voids 1a, the denser the distribution of the voids 1a. This maximum distance r represents the distribution density of the voids 1a. As shown in Table 2, those having a maximum distance r between adjacent voids 1a of 0.2 mm or less, preferably 0.1 mm or less, were excellent in sealing properties. In other words, it can be seen that the denser the voids 1a, the better the sealing property, and the better the distance between adjacent voids 1a is 0.2 mm or less. As shown in FIG. 3 which is a chart showing the surface roughness of the preferred piston 1 belonging to the range of No. 2 in Table 2, the voids are densely distributed. On the other hand, as shown in FIG. 4, a chart showing the surface roughness of the piston 1 belonging to the range of No. 5 has a sparse distribution of voids. Was inferior. In addition, the surface shape as shown in FIG.
Are densely distributed, so that the sealing property is good. However, since the flat surface 1b between the voids 1a does not exist, the wear resistance of the cap seal 3 is slightly inferior. Furthermore, the maximum depth d of the void 1a shown in FIG. 2 was examined in the same manner. As a result, the maximum depth d of 6 μm or less was excellent in terms of sealing performance. Summarizing the above experimental results, in order to improve the sealing performance and the wear resistance of the cap seal in the low pressure plunger pump, the center line average roughness of the sliding surface of the inner wall of the piston 1 or the cylinder 2 with the cap seal 3 is required. Sa (R
a) may be set to 0.15 to 0.4 μm. In particular, in order to enhance the sealing property, the maximum distance r between the voids 1a which are adjacent to the sliding surface may be set to 0.2 mm or less. Further, in order to obtain such a surface shape, the size and polishing time of abrasive grains used for polishing the inner wall surface of the piston 1 or the cylinder 2 may be adjusted. [Effects of the Invention] As described above, according to the present invention, in a low-pressure plunger pump using a cap seal, at least the surface of the piston or cylinder on which the cap seal slides is formed of alumina ceramic, The center line average roughness (Ra) of the surface is set to 0.15 to 0.4 μm, and the sliding surface has voids with a maximum distance of 0.2 mm or less. The plunger pump can provide a plunger pump having features such as high abrasion, excellent sealing performance, and low abrasion of the cap seal, so that excellent characteristics can be maintained for a long period of time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a main part of a low-pressure plunger pump according to an embodiment of the present invention, and FIG. 2 is a surface state of a piston of the low-pressure plunger pump according to the embodiment of the present invention. FIG. FIGS. 3 to 5 are charts showing the surface roughness of the piston of the low-pressure plunger pump according to the embodiment of the present invention. 1: Piston 2: Cylinder 3: Cap seal

Claims (1)

(57) [Claims] In a low-pressure plunger pump comprising a cylinder and a piston held reciprocally through a soft material cap seal in the cylinder, at least the cap seal of the inner wall surface of the cylinder or the outer wall surface of the piston is provided. The sliding surface is made of alumina ceramic, and the center line average roughness (Ra) on these sliding surfaces is
A plunger pump for low pressure, characterized in that voids are present at a distance of 0.15 to 0.4 μm and a maximum distance of 0.2 mm or less on said sliding surface.