JPH0985966A - Plunger pump for ink recovery of ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a plunger pump used for ink recovery of an ink jet recorder operate stably and with a low glide torque and make it perform its ink recovery function even if there is no grease in its seal. SOLUTION: In a plunger pump used for ink recovery of an ink jet printer equipped with sealing members 6, 8 which contact slidingly the outside face of a plunger 4 or the inside face of a cylinder 1 and seal airtightly the outside face of the plunger 4 or the inside face of the cylinder 1, the sealing members 6, 8 are composed of a lubricating rubber constituent containing 10 to 100 pts.wt. of a tetrafluoroethylene resin powder with a carbon material protruded onto the surface thereof and 5 to 80 pts.wt of a cubic graphite in relation in relation to 100 pts.wt. of an acrylonitrile-butadiene rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink collecting plunger pump of an ink jet recording apparatus for sucking and cleaning an ink ejection port of a recording head of the ink jet recording apparatus.

[0002]

2. Description of the Related Art Generally, high-viscosity ink or dust adhering to an ink ejection port of a recording head of an ink jet recording apparatus hinders the ink ejection function of the recording head. Must be
An ink recovery plunger pump for this purpose is attached.

The structure and function of such a suction plunger pump will be described with reference to FIGS. 1 and 2. In this structure, the suction port 3 communicating with the ink recovery passage 2 is opened in the middle of the cylinder 1. A discharge passage 5 communicating with a discharge tank (not shown) is arranged in front of the plunger 4, and a rear part of the reciprocating plunger 4 is slidably supported by a ring-shaped seal member 6 fixed to the inner surface of the cylinder 1. Along with
Two flange-shaped valve seats 7a, 7b are formed on the outer peripheral surface in front of the plunger 4 with an axial gap therebetween, and a second seal member 8 serving both as a piston seal and a valve body is provided between these valve seats. It is mounted on the inner surface of the cylinder so as to be slidable and in close contact with airtightness, and has a valve device function.

The second ring-shaped seal member 8 is formed so that its inner diameter is larger than the small diameter portion of the plunger 4, that is, between the inner peripheral surface of the seal member 8 and the outer peripheral surface of the plunger 4. The passage 9 is formed.

A through hole 10 is formed in the valve seat 7b located in front of the plunger 4 at a position where it can communicate with the passage 9.

Therefore, as shown in FIG. 1, when the plunger 4 is pulled in the A direction (retracting direction), the front end face of the seal member 8 is in close contact with the rear end face of the valve seat 7b and penetrates the passage 9. The holes 10 communicate with each other, and the ink in the space a moves to the front space b.

Then, as shown in FIG. 2, when the plunger is pushed out in the B direction (forward direction), the rear end face of the seal member 8 comes into close contact with the front end face of the valve seat 7a,
The seal member 8 acts only as a piston seal and further pushes the ink in the space b to the discharge path 5.

At this time, since the pressure in the space a sealed by the seal member 6 is reduced, the high-viscosity ink and dust adhering to the ink ejection port of the recording head is sucked and collected from the suction port 3 into the space a. Is done.

Then, the sucked ink and dust are returned to the plunger 4 in the A direction (retracting direction) as shown in FIG.
In the state where the ink is pulled in, the ink moves to the front space b, and the above operation is repeated to collect and discharge the ink.

Incidentally, the seal member of the conventional plunger pump in the above-mentioned ink jet recording apparatus is made of a rubber ring, and grease is applied to enhance slidability.

[0011]

However, as described above, the conventional plunger pump in the ink jet recording apparatus cannot exhibit sufficient sliding performance unless grease is supplied to the seal, and therefore it is in use. In addition, there are problems that the grease runs out and the sliding torque becomes large, and excess grease is mixed with the ink and the ink is hardened in the discharge path or the like.

Therefore, the object of the present invention is to solve the above-mentioned problems and to operate an ink recovery plunger pump of an ink jet recording apparatus stably with a low sliding torque even when there is no grease on the seal and to recover the ink. The challenge is to ensure that the functions are stable and well exhibited.

[0013]

In order to solve the above problems, according to the present invention, there is provided an ink jet recording apparatus provided with a seal for slidingly contacting an outer surface of a plunger or an inner surface of a cylinder to hermetically seal the outer surface of the plunger and the inner surface of the cylinder. In the plunger pump for ink recovery, the seal is formed of a lubricating rubber composition containing 10 to 100 parts by weight of tetrafluoroethylene resin powder and 5 to 80 parts by weight of spherical graphite with respect to 100 parts by weight of acrylonitrile butadiene rubber. I did.

Further, as the tetrafluoroethylene resin powder, a tetrafluoroethylene resin powder is used which is co-precipitated with a carbon material after the completion of emulsion polymerization so that the carbon material is projected on the surface.

Alternatively, as the tetrafluoroethylene resin powder, a tetrafluoroethylene resin powder in which a tetrafluoroethylene resin and a carbon material are dry-mixed and a carbon material is projected on the surface is adopted.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylonitrile butadiene rubber (hereinafter abbreviated as NBR) according to the present invention may be any one having a rubber-like elasticity at room temperature, and a wide range of compounds synthesized by a known synthesis method can be used. Can be adopted.

That is, since NBR is a copolymer of butadiene and acrylonitrile, its physical properties can be changed by adjusting the amount of acrylonitrile within the range of about 15 to 50%. The amount of such nitrile can be classified into, for example, less than 24% of low nitrile, 24 to 30% of medium nitrile, 30 to 36% of medium high nitrile, 36 to 42% of high nitrile, and 42% of extremely high nitrile. In order to increase the wear resistance, aging resistance, and tensile strength of rubber in such a range, it is preferable to increase the amount of nitrile, but rubber elasticity, cold resistance, and low temperature characteristics are not impaired. Nitrile content in the range of about 24% to 42%, or about 2
It is preferably in the range of more than 4% and less than 42%.

The molecular weight of such NBR is usually preferably 50,000 or more, and one having a high molecular weight is preferable, so that a good result is obtained, more preferably 70,000 or more, particularly preferably 10 to 50. Adopt about 10,000 items. The following are commercially available NBRs that satisfy the required conditions.

Nippon Synthetic Rubber Co., Ltd .: JSR-N Nippon Zeon Co., Ltd .: NIPOL Goodyear Co., Ltd .: CHEMIGUM Further, tetrafluoroethylene resin (hereinafter abbreviated as PTFE) powder in the present invention is suspended. Although either a molding powder produced by a polymerization method or a fine powder produced by an emulsion polymerization method may be used, it is crushed or crushed after being subjected to pressure / heat treatment, γ-ray irradiation treatment or electron beam irradiation. It is possible to use a treated product or a product having an average particle size of 20 μm or less which has been subjected to γ-ray irradiation treatment or electron beam irradiation treatment after polymerization.
Examples of commercially available products include the following.

Daikin Industries, Ltd .: Lubron L10 Asahi Glass: Fluon G163, Fluon CD1, Lubricant L169, L182J, Mitsui DuPont Fluorochemicals: Teflon 7J. Further, as a more preferable PTFE powder, its form is shown in FIG. Some are shown enlarged. This is one in which a carbon material 12 such as flake graphite is projected on the surface of PTFE powder 11, that is, the carbon material 12 is PTFE.
The surface of the powder 11 is pierced.

To produce such PTFE powder,
For example, at the end of emulsion polymerization in the production of fine powder, it is coprecipitated with a carbon material for coagulation, washed, and then dried.
As another manufacturing method, the carbon material may be dry mixed with the PTFE powder, and the PTFE material may be pierced on the surface of the PTFE powder.

As the carbon material, powder products in various crystal states from general carbon powder to graphite can be adopted.
Since it is expected that the crystal structure due to graphitization will improve the lubricity, it is particularly preferable to use graphite. Further, it may be HAF, SAF, FEF, MT, or the like, which is a carbon black having a large structure, which is generally used as a rubber material.

In the PTFE powder 11 used in the present invention, the carbon material 12 made of graphite or the like projects in all directions (radially) on the powder surface as shown in the figure, so that the physical pile effect in the rubber base material 13 is obtained. Since the rubber base material 13 and the carbon material 12 have a good affinity with each other, the composition obtained by kneading the rubber base material 13 and the PTFE powder 11 is a rubber compounded with the PTFE powder which does not hold the carbon material. Higher strength than the composition is obtained.

The spheroidal graphite used in the present invention is spheroidal graphite produced as a by-product in the step of spinning from pitch, or a sphere-shaped polymer obtained by reacting a phenol resin with paraformaldehyde under a catalyst to polymerize into spheres. Examples include spheroidal graphite that has been fired and crushed. As commercially available spherical graphite,
The following are mentioned.

Osaka Gas Chemical Co., Ltd .: Mesocarbon beads Kanebo Co., Ltd .: Bell Pearl, Unitika Co., Ltd .: Univex, Nippon Carbon Co., Ltd .: Microcarbon beads, NBR and PTFE powder are mixed in a weight ratio of NBR100.
It is preferable that the PTFE powder is 10 to 100 parts by weight with respect to parts by weight. If the PTFE powder is less than 10 parts by weight, sufficient frictional properties cannot be imparted to NBR, and if it is blended in a large amount in excess of 100 parts by weight, the rubber hardness becomes high and the elastic properties disappear, or the mechanical strength extremely decreases. It will not be practically applicable.

The compounding weight ratio of the spherical graphite used in the present invention is 5 to 80 parts by weight with respect to 100 parts by weight of NBR. The reason for this is that if the compounding ratio is less than 5 parts by weight, NB
A rubber composition which cannot impart sufficient wear resistance to R and is compounded in a large amount in excess of 80 parts by weight to increase rubber hardness and lose elastic properties, or to have mechanical strength extremely deteriorated, which cannot be practically used. Because it becomes a thing.

In the present invention, a known compounding agent for rubber or a known additive may be compounded in an amount that does not impair the object.

(1) Reinforcing agent: carbon black, silica, clay, calcium carbonate, magnesium hydroxide, aluminum hydroxide, aluminum oxide, talc, mica, kaolin, bentonite, shirasu, wollastonite, silicon carbide, glass powder, Carbon powder, boron fiber, aramid fiber, etc. (2) Vulcanization aid: zinc white, fatty acid, etc. (3) Vulcanization accelerator: guanidines, sulfur, aldehyde-amines, zinc, etc. (4) Plasticizers: dimethyl phthalate, dioctyl phthalate, etc. (5) Anti-aging agents: amines, phenols, etc. (6) Others, such as antioxidants, UV absorbers, flame retardants, colorants, etc. Oils, waxes and greases may be added to improve the moldability and the non-tackiness of the surface. The blending amount is such that it does not affect the mechanical strength of the rubber molded product, that is, NBR1
The amount is preferably 2 to 20 parts by weight, more preferably 5 to 10 parts by weight, based on 00 parts by weight.

As solid lubricants, in addition to PTFE, tetrafluoroethylene-ethylene copolymer (ETFE) which is a molten fluororesin, tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene. You may add a copolymer (FEP) etc.

The method of mixing the above various raw materials is not particularly limited, and a method that is generally widely used, for example, NBR as the main raw material and other fillers are individually and sequentially mixed or collectively roll-mixed. Machine, propeller mixer,
Mixing may be performed with a kneader mixer or other mixer. In addition,
At this time, it is desirable to provide a temperature controller to prevent heat generation due to friction. Further, when a roll mixer is used, it is preferable to carry out thin threading with a roll interval of 3 mm or less for finish mixing.

The seal according to the present invention does not require a particularly limited means in the molding step, and is temporarily vulcanized (for example, 140 to 170 ° C.) by an ordinary press molding method.
10 to 30 minutes at a pressure of 50 to 150 kgf / cm ² ) and then secondary vulcanization (for example, 2 to 20 at 150 to 180 ° C.).
It can be molded by applying pressure for no time.

[0032]

EXAMPLES The raw materials used in Examples and Comparative Examples are summarized below. The blending ratio of each component is shown in parts by weight based on 100 parts by weight of the following NBR basic blending.

[NBR basic compounding A] (high nitrile type, nitrile amount 36 to 42%) Japan Synthetic Rubber Co., Ltd .: JSR220S 100 parts by weight Sodium stearate: General industrial material 1 〃 Carbon black: FEF 30 〃 Vulcanization accelerator 1: Ouchi Shinko Chemical Industry Co., Ltd .: TT 2 vulcanization accelerator 2: Ouchi Shinko Chemical Industry Co., Ltd .: M 2 〃 Vulcanization aid: Zinc oxide (activated zinc white) 10 〃 Vulcanizing agent: Sulfur 1 0.0 〃 [NBR basic compounding B] (Medium nitrile type, nitrile amount 25-30%) Made by Japan Synthetic Rubber Co., Ltd .: JSR240S 100 parts by weight Sodium stearate: General industrial material 1 〃 Carbon black: FEF 30 〃 Vulcanization accelerator 1: Ouchi Shinko Chemical Co., Ltd .: TT 2 〃 Vulcanization accelerator 2: Ouchi Shinko Chemical Co., Ltd .: M 2 〃 Vulcanization aid: Zinc oxide (active zinc white) 10 〃 Vulcanization : Sulfur 1.0 〃 [lubricant] (1) graphite coprecipitation PTFE [PTFE-1] Graphite having an average particle size of 6μm after completion of polymerization by emulsion polymerization and 7:
It was obtained by coprecipitation in a weight ratio of 3, coagulation and washing.

(2) Dry blend PTFE with graphite
[PTFE-2] PTFE (Lubricant L182J) manufactured by Asahi Glass Co., Ltd. was dry blended with graphite having an average particle size of 6 μm at a weight ratio of 7: 3 by a Henschel mixer.

(3) PTFE [PTFE-3] Asahi Glass Co., Ltd .: PTFE Lubricant L182J (4) ETFE (Asahi Glass Co., Ltd .: Aflon COP Z88)
20) (5) Spherical graphite (Bellpearl C2000 manufactured by Kanebo) (6) Silicone oil (KF9 manufactured by Shin-Etsu Silicone)
6-300) [Examples 1 to 9, Comparative Examples 1 to 5] Roll interval 5 to 10 m
The NBR (220S or 240S) is wound around a roll mixer adjusted to about m, and the inorganic filler, the antioxidant, the carbon, and the sulfur are added in the proportions shown in the basic composition A or B.
The vulcanization accelerators were sequentially mixed, and finally PTFE and other fillers were kneaded in the proportions shown in Table 1 or Table 2.

Then, the roll interval was adjusted to 1 mm, and thin threading was performed 10 times. For the purpose of preventing frictional heat at this time, cooling water was constantly passed through the roll to keep the roll temperature at 60 ° C or lower. Next, the cooling water was stopped, steam was passed through the roll to adjust the rubber temperature to 70 ° C or higher and 90 ° C or lower, and then the roll interval was narrowed to 1 mm, and thin threading was performed 10 times, and 10 kg of compound was used for each. Obtained.

Then, each compound was molded into a seal that can be attached to the ink collecting plunger pump of the ink jet recording apparatus shown in FIGS. That is, a ring-shaped seal 6 for fixing having an inner diameter of 2.6 mm and an outer diameter of 5.2 mm and an inner diameter of 2.4 mm, an outer diameter of φ
The above compound was press-molded so as to form a ring-shaped seal 8 for both 5.0 mm piston seal and valve body, and primary vulcanization (160 ° C., 10 minutes, pressing pressure 120 k).
gf / cm ² ) and secondary vulcanization (free heating, 150
C., 4 hours).

The respective seals 6 and 8 obtained in this way
Is mounted on the ink collecting plunger pump of the ink jet recording apparatus shown in FIGS.
Attach a load cell not shown in the figure and reciprocate it,
Sliding torque after 5 reciprocations and 1000 reciprocations (g
f) is measured to evaluate the slidability, and the negative pressure (kgf / cm ² ) after 5 reciprocations and 1000 reciprocations is measured by the negative pressure sensor attached to the ink suction port 3. The sealing property was evaluated. These results are also shown in Table 1 or Table 2.

Further, according to JIS-K6301, the hardness (JIS-A) is applied to a separately formed sheet-shaped test piece,
Check tensile strength (kgf / cm ² ) and elongation (%),
The results are shown in Table 1 or Table 2.

[0040]

[Table 1]

[0041]

[Table 2]

As is clear from the results of Tables 1 and 2, the sliding torque was large in Comparative Example 1 containing only the general NBR compound, and the test of 1000 reciprocations could not be carried out. In addition, the sliding torques of 2 and 3 in which PTFE was added to NBR were slightly lower than those of Comparative Example 1 in which the rubber base material was used, but the plunger was abraded when the number of reciprocations reached 1000 times, resulting in sealability (negative pressure). Has dropped. Further, in Comparative Example 4 in which spherical graphite was mixed, the sliding torque was extremely increased. In Comparative Example 5 containing the silicone oil, the negative pressure (sealing property) was reduced when the plunger reciprocated 1000 times due to wear.

On the other hand, in the examples in which the powdery PTFE in which the carbon material is projected on the surface and the spherical graphite are added together and all the conditions are satisfied, the stability of sliding torque and negative pressure (sealability) is shown. It was found that such a seal sufficiently stabilizes the ink recovery function of the ink recovery plunger pump.

[0044]

As described above, according to the present invention, acrylonitrile butadiene rubber, tetrafluoroethylene resin powder having a carbon material projected on the surface thereof, and spherical graphite are used as a seal for an ink recovery plunger pump of an ink jet recording apparatus. Since a lubricating rubber composition containing a predetermined amount of is used, the ink-collecting plunger pump of this ink jet recording apparatus operates stably with a low sliding torque even when there is no grease on the seal, and also has an ink-collecting function. There is an advantage that it can be stably and satisfactorily exhibited.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a retracted state of a plunger in an ink recovery plunger pump of an inkjet recording apparatus.

FIG. 2 is a cross-sectional view showing a state in which the plunger of the ink recovery plunger pump of the inkjet recording apparatus has advanced.

FIG. 3 is a schematic diagram showing a tetrafluoroethylene resin powder in a rubber base material.

[Explanation of symbols]

 1 Cylinder 2 Ink Recovery Channel 3 Suction Port 5 Discharge Channel 6 Sealing Members 7a, 7b Valve Seat 8 Sealing Member 9 Passage 10 Through Hole 11 PTFE Powder 12 Carbon Material 13 Rubber Base Material

Claims (3)

[Claims] 1. A plunger pump for recovering ink in an ink jet recording apparatus, wherein a seal is provided so as to hermetically seal the outer surface of the plunger and the inner surface of the cylinder by slidingly contacting the outer surface of the plunger or the inner surface of the cylinder.
To 10 parts by weight of tetrafluoroethylene resin powder
A plunger pump for ink recovery of an ink jet recording apparatus, wherein the plunger pump is formed of a lubricating rubber composition containing -100 parts by weight and 5-80 parts by weight of spherical graphite. 2. The ink recovery of an ink jet recording apparatus according to claim 1, wherein the tetrafluoroethylene resin powder is a tetrafluoroethylene resin powder which is co-precipitated with a carbon material after the completion of emulsion polymerization so that the carbon material is projected on the surface. Plunger pump for. 3. The ink for an ink jet recording apparatus according to claim 1, wherein the tetrafluoroethylene resin powder is a tetrafluoroethylene resin powder obtained by dry-mixing a tetrafluoroethylene resin and a carbon material so that the carbon material is projected on the surface. Plunger pump for collection.