Abstract:
The electrically motorized pump has a low energy loss because it uses of the shaft and the sleeve made from synthetic resin composition obtained by uniformly dispersing fine powder of RBC or CRBC in a resin. The typical process for the production of a synthetic resin composition for making the sleeve bearing for the pump for use in water includes kneading with a resin the fine powder of RBC or CRBC at a temperature in the neighborhood of the melting point of the resin, and thereby uniformly dispersing the fine powder of RBC or CRBC in the resin.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This application claims priority based on Japanese patent application No. 2002-069357, filed Mar. 13, 2002.  
           [0003]    The present invention relates to an electrically motorized pump for circulating cooling water in a water-cooled engine. More particularly, the present invention relates to an electrically motorized water pump that uses a sleeve bearing which offers a low frictional coefficient in water.  
           [0004]    2. Description of the Related Art  
           [0005]    A conventional water pump for pumping cooling water in a closed cooling water circuit is driven by a crank shaft of an engine. The cooling water circuit includes a water jacket of the engine connected to a radiator of the engine. Such a conventional pump&#39;s rotation corresponds to the number of revolutions of the engine. The number of revolutions of such pump could not be controlled in a fine manner. Furthermore, when the engine stops, the pump stops immediately thereby causing troubles.  
           [0006]    On the other hand, if a pump for use with water is driven by an electric motor, it is possible to arbitrarily control the number of revolutions and keep it running even when the engine is stopped. It is also possible to arbitrarily control the flow volume of cooling water passing through a radiator by electrically varying the degree of opening of a thermostatically controlled valve. Such a cooling control device for an engine has been disclosed in Japanese Laid Open Patent Gazette, Laid Open Publication No. Hei 5/1993-231148.  
           [0007]    The conventional electrically motorized pump for use with water has a structure in which the impeller side and the rotor side of a pump are sealed to prevent water from flowing through. An O ring made of rubber is placed between the impeller side and the rotor side or a sealing material is allowed to be in close contact with a rotary shaft. When the rotor is used at high revolutions for a long period of time, the O ring deteriorates causing a loss in energy, also the sealing material, which is in close contact with the shaft causes a loss in energy.  
           [0008]    One object of the present invention is to provide an electrically motorized pump for use in water which does not require any seal between the impeller side and the rotor side of a pump, allows water to freely flow therethrough, has low power consumption, and allows cooling water to circulate efficiently in a water-cooled engine.  
           [0009]    The objects are achieved by improving upon materials described in an article by Mr. Kazuo Horikirigawa (Kinou Zairyou (Functional Materials), May 1997 issue, Vol. 17, No. 5, pp 24 to 28) that discloses a porous carbon material made by using rice bran, which is called “RB ceramic” (hereinafter referred to as “RBC”). RBC is a carbon material obtained by mixing and kneading defatted rice bran and a thermosetting resin, and then by molding the mixture and sintering it in an inert gas atmosphere after drying the compact. Any thermosetting resin including a phenol resin, a diaryl phthalate resin, an unsaturated polyester resin, an epoxy resin, a poly imide resin, or a triazine resin may be used. Phenol resin being the preferred material. The mixing ratio between defatted rice bran and the thermosetting resin is 50 to 90:50 to 10 by mass, 75:25 being the preferred ratio. Sintering is done at 700° C. to 1000° C. for about 40 minutes to 120 minutes using, for example, a rotary kiln.  
           [0010]    CRB ceramic (hereinafter referred to as “CRBC”) is a black colored porous ceramic obtained by further improving RBC as follows: after mixing and kneading defatted rice bran and a thermosetting resin, and then preliminarily sintering the mixture at a temperature of 700° C. to 1000° C. in an inert gas atmosphere, the mixture is pulverized to about 100 mesh or less to generate a carbonized powder. Next, the carbonized powder and a thermosetting resin are mixed and kneaded, and after molding it under pressure of 20 Mpa to 30 Mpa, the molded substance is again heat treated at a temperature of 500° C. to 1100° C. in an inert gas atmosphere to obtain CRBC.  
           [0011]    RBC and CRBC have the following excellent characteristics:  
           [0012]    High hardness.  
           [0013]    The surface of each particle is irregular.  
           [0014]    Extremely small coefficient of thermal expansion.  
           [0015]    The textural constitution is porous.  
           [0016]    Conducts electricity.  
           [0017]    The specific gravity is low and it is light in weight.  
           [0018]    Extremely small coefficient of friction.  
           [0019]    Excellent anti-wearing property.  
           [0020]    As the raw material is rice bran, its adverse effects on the earth&#39;s environment are minor, and it leads to the resource saving.  
         SUMMARY OF THE INVENTION  
         [0021]    The shortcomings of the prior art are overcome by the present invention by providing an electrically motorized pump for use in water. The pump has a stator accommodated in an outer peripheral space between a housing with a collar and a can seal with a collar. A rotor, a rotary shaft, and a sleeve bearing are accommodated in the inner space of the can seal. The sleeve bearing is attached to a central hole of a base plate of a pump casing. Said base plate, a collar section of the housing and the can seal are attached to each other. An impeller attached to a tip section of the rotary shaft is located in the inner side of the pump casing. The electrically motorized pump has a low energy loss because it uses a shaft and a sleeve made from a synthetic resin composition obtained by uniformly dispersing a fine powder of RBC or CRBC in a resin.  
           [0022]    The synthetic resin composition obtained by mixing the RBC or CRBC in form of fine a powder of an average particle diameter of 300 μm or less, preferably 10 to 100 μm, more preferably 10 to 50 μm, and a resin displays specific desirable sliding motion characteristics. In particular the synthetic resin composition obtained by uniformly dispersing a fine powder of RBC or CRBC, especially at a ratio by mass of the fine powder of RBC or CRBC:resin, of 30 to 90:70 to 10 displays surprisingly good wear characteristics with anti-rust property in water, alcohol, ethylene glycol and a mixture thereof.  
           [0023]    The typical process for the production of a synthetic resin composition for making the sleeve bearing for the pump for use in water includes kneading with a resin the fine powder of RBC or CRBC at a temperature in the neighborhood of the melting point of the resin, and thereby uniformly dispersing the fine powder of RBC or CRBC in the resin. The RBC can also be made using materials other than rice bran that can be a source of carbon. One example of such material is bran of another grain such as oat.  
           [0024]    Further features and advantages will appear more clearly on a reading of the detailed description, which is given below by way of example only and with reference to the accompanying drawings wherein corresponding reference characters on different drawings indicate corresponding parts. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 is a schematic drawing showing the assembly of a pump for use in water.  
         [0026]    [0026]FIG. 2 is a cross sectional view of the pump for use in.  
         [0027]    [0027]FIG. 3 is one example of a shaft of a sleeve bearing.  
         [0028]    [0028]FIG. 4 is one example of a shaft of a sleeve bearing. 
     
    
     DETAILED DESCRIPTION  
       [0029]    [0029]FIG. 1 is a schematic drawing showing the assembly of a pump for use in water. Sleeve bearings  2  and  2 ′ are slidably Mounted a the rotary shaft  1 - 1 . A rotor  1 ′ is attached to rotary shaft  1 - 1  to form a rotor assembly  1 . An impeller  4  is mounted at the tip section of rotary shaft  1 - 1  and protrudes into pump easing  5  from a central section  3  of pump casing  5  through an O-ring  11 . On the other hand, a stator assembly  8  for the rotation of rotor  1  is tightly sealed in a water tight outer peripheral space formed by a can seal  9  with a collar and a housing  6  with a collar so as to prevent water from penetrating. A hole sensor assembly  7  is placed within housing  6 . Rotor assembly  1  is placed within can seal  9 . A pump assembly is made by attaching together housing  6 , central section  3  and pump casing  5  through O-ring  11  by means of a fixing means such as a screw, or a bolt and a nut. The pump assembly so formed allows fluid from impeller side to flow to the rotor side.  
         [0030]    [0030]FIG. 2 shows the cross sectional view of the pump for use with water. When an electric current is allowed to flow through stator assembly  8 , rotor  1  rotates, thereby rotating rotary shaft  1 - 1  and impeller  4  and thus water is taken in and sent to the cooling section of an engine. Sleeve bearing  2  consists of shaft  1 - 1  and sleeve  2 - 2 . Either one or both of Shaft  1 - 1  and Sleeve  2 - 2  are formed by molding a synthetic resin composition obtained by uniformly dispersing fine powder of RBC or CRBC in a resin.  
         [0031]    In one embodiment shaft  1 - 1  is made of an alloy from the stainless steel family. If a hard shaft is required, quenching is carried out. As shown in FIG. 4, if necessary, it is permissible to press a hard anti-rusting alloy sleeve  1 - 2  in portion of shaft  1 - 1 . Non limiting examples of steel series metal that may be used for making shaft  1 - 1  or sleeve  2 - 2  are stainless steel type alloy of iron, nickel, chrome, and molybdenum. Any alloy, as long as it is hard and difficult to rust, can be used. Furthermore, it is also permissible to make shaft  1 - 1  with the above-mentioned synthetic resin composition.  
         [0032]    The RBC or CRBC has an average particle diameter of 300 μm or less. Average particle diameter of 10 to 100 μm, more preferably 10 to 50 μm, allows a surface condition of a good frictional coefficient to be formed, and is appropriate as a material for a sleeve bearing for sliding motion in water.  
         [0033]    Resins such as, for example, poly amide, polyester, and poly olefin can be used with RBC or CRBC to obtain synthetic resin composition. Thermoplastic resins such as nylon 66 (poly hexa- methylene adipamide), nylon 6 (poly capramide), nylon 11 (poly undecane amide), nylon 12, poly acetal, poly butylenes terephthalate, poly ethylene terephthalate, poly propylene, poly ethylene, and poly phenylene sulfide can also be used with RBC or CRBC to obtain the synthetic resin composition, nylon 66 being preferred. These thermoplastic resins can be used alone or a mixture of two or more may be used. Thermosetting resin alone or in combination with other resins can be used with RBC or CRBC to obtain synthetic resin composition. Non-limiting examples of such thermosetting resins are diaryl phthalate resin, an unsaturated polyester resin, an epoxy resin, a poly imide resin, or a triazine resin. RBC can also be made from materials other than rice bran that can be source of carbon. One example of such material is bran of another grain such as oat. The ratio by mass of fine powder of RBC or CRBC to resin is 30 to 90:70 to 10. If the amount of a resin or a combination of resins exceeds 70% by mass, the low frictional characteristics can not be achieved, on the other hand, if a resin or a combination of resins is 10% by mass or less, the molding becomes difficult.  
         [0034]    The molding is in general done by extrusion molding or injection molding. The preferred temperature of the mold die is on a slightly lower side between the glass transition point and the melting point of the resin. Furthermore, good frictional property can be obtained by gradual cooling of the mold die.  
         [0035]    The following examples explain the details of the present invention.  
       EXAMPLE 1  
       [0036]    Manufacturing Example of RBC Fine Powder  
         [0037]    750 grams of defatted rice bran and 250 grams of a phenol resin in liquid form (Resol) were mixed and kneaded while heating them at a temperature of 50° C. to 60° C. A uniform mixture having plasticity was obtained. The mixture was baked for 100 minutes at a temperature of 900° C. in a nitrogen atmosphere in a rotary kiln, and the carbonated baked product thus obtained was pulverized in a pulverizing machine. The pulverized product was sieved through a sieve of 150 mesh to obtain a fine powder of RBC having an average particle diameter of 140 to 160 μm.  
         [0038]    Example of Preparation 1 of a Composition of RBC Fine Powder and a Resin  
         [0039]    While heating at a temperature of 240° C. to 290° C., 500 grams of the RBC fine powder thus obtained and 500 grams of nylon 66 powder were mixed and kneaded. Thus a uniform plastic mixture having 50% by mass of the RBC fine powder was obtained.  
         [0040]    Preparation of a Sleeve Bearing and Application Thereof to a Pump for Use in Water  
         [0041]    The synthetic resin composition obtained by melting and mixing the RBC fine powder and nylon 66 was injection molded, thereby preparing a sleeve of 22 mm in outer diameter, 8 mm in inner diameter, and 20 mm in length. A shaft of 7.95 mm in outer diameter and 200 mm in length made of SUS 303 stainless alloy was inserted into the molded sleeve, thereby preparing a sleeve bearing as shown in FIG. 3. As shown in FIG. 1 and FIG. 2, this sleeve was used in the sleeve bearings  2  and  2 ′ for a rotor assembly.  
       EXAMPLE 2  
       [0042]    By using the method described in Example 1, RBC fine powder of an average particle diameter of 140 to 160 μm was obtained.  
         [0043]    Example of Preparation 2 of a Composition of RBC Fine Powder and a Resin  
         [0044]    While heating at a temperature of 240° C. to 290° C., 700 grams of the RBC fine powder thus obtained and 300 grams of nylon 66 powder were mixed and kneaded. Thus a uniform plastic mixture having 70% by mass of the RBC fine powder was obtained.  
         [0045]    Preparation of a Sleeve Bearing and Application Thereof to a Pump for Use in Water  
         [0046]    The synthetic resin composition obtained by melting and mixing the RBC fine powder and nylon 66 was injection molded, thereby preparing a sleeve of 22 mm in outer diameter, 8 mm in inner diameter, and 20 mm in length. A shaft of 7.95 mm in outer diameter and 200 mm in length made of SUS 304 stainless alloy was inserted into the molded sleeve, thereby preparing a sleeve bearing as shown in FIG. 3. As shown in FIG. 1 and FIG. 2, this sleeve was used in sleeve bearings  2  and  2 ′ of a rotor assembly.  
       EXAMPLE 3  
       [0047]    Manufacturing Example 3 of RBC Fine Powder  
         [0048]    750 grams of defatted rice bran and 250 grams of a phenol resin in a liquid form (Resol) were mixed and kneaded while heating them at a temperature of 50° C. to 60° C. A uniform mixture having plasticity was obtained. The mixture was baked for 100 minutes at a temperature of 1000° C. in a nitrogen atmosphere in a rotary kiln, and the carbonated baked product thus obtained was pulverized in a pulverizing machine, followed by sieving with a sieve of 400 mesh, and thus fine powder of RBC having an average particle diameter of 40 to 50 μm was obtained.  
         [0049]    Example of Preparation 3 of a Composition of RBC Fine Powder and a Resin  
         [0050]    While heating at a temperature of 240° C. to 290° C., 700 grams of the RBC fine powder thus obtained and 300 grams of nylon 66 powder were mixed and kneaded. Thus a uniform plastic mixture having 70% by mass of the RBC fine powder was obtained.  
         [0051]    Preparation of a Sleeve Bearing and Application Thereof to Pump for Use in Water  
         [0052]    The synthetic resin composition obtained by melting and mixing the RBC fine powder and nylon 66 was injection molded, thereby preparing a sleeve of 22 mm in outer diameter, 8 mm in inner diameter, and 20 mm in length. A shaft of 7.95 mm in outer diameter and 200 mm in length made of SUS bearing steel was inserted into the molded sleeve, thereby preparing a sleeve bearing as shown in FIG. 3. As shown in FIG. 1 and FIG. 2, it was used as sleeve bearings  2  and  2 ′ of a rotor assembly.  
       EXAMPLE 4  
       [0053]    Manufacturing Example of CRBC Fine Powder  
         [0054]    750 grams of defatted rice bran and 250 grams of a phenol resin in a liquid form (Resol) were mixed and kneaded while heating them at a temperature of 50° C. to 60° C. A uniform mixture having plasticity was obtained. The mixture was baked for 60 minutes at a temperature of 900° C. in a nitrogen atmosphere in a rotary kiln. And the carbonated baked product thus obtained was pulverized in a pulverizing machine, followed by sieving with a sieve of 200 mesh, and thus fine powder of RBC having an average particle diameter of 100 to 120 μm was obtained.  
         [0055]    While heating at a temperature of 100° C. to 150° C., 750 grams of the RBC fine powder thus obtained and 500 grams of a phenol resin in a solid form (Resol) were mixed and kneaded. Thus a uniform mixture having plasticity was obtained. Then, the plastic material was molded under pressure into a sphere of about 1 cm in diameter under a pressure of 22 Mpa. The temperature of the mold die was 150° C. The molded product was taken out from the mold die and placed in a kiln, the temperature of the molded product was raised to 500° C. in a nitrogen atmosphere at a rate of 1° C. per minute, and it was kept at 500° C. for 60 minutes, and then sintered at 900° C. for about 120 minutes. Then, the temperature was lowered to 500° C. at a rate of 2 to 3° C. per minute, and after reaching 500° C. or lower, it was cooled naturally while leaving it undisturbed. The CRBC molded product thus obtained was pulverized in a pulverizing machine, followed by sieving with a sieve of 500 mesh to obtain CRBC fine powder having an average particle diameter of 20 to 30 μm.  
         [0056]    Example of Preparation of a Composition of CRBC Fine Powder and a Resin  
         [0057]    While heating at a temperature of 240° C. to 290° C., 500 grams of the CRBC fine powder thus obtained and 500 grams of nylon 66 powder were mixed and kneaded. Thus a uniform plastic mixture having 50% by mass of the CRBC fine powder was obtained.  
         [0058]    Preparation of a Sleeve Bearing and Application Thereof to a Pump for Use in Water  
         [0059]    The synthetic resin composition obtained by melting and mixing the CRBC fine powder and nylon 66 was injection molded into a sleeve of 22 mm in outer diameter, 8 mm in inner diameter, and 20 mm in length. A 200 mm long shaft is made by pressing two cylindrical members of 7.95 mm in outer diameter, 5.00 in inner diameter and 20 mm in length and made of SUS 304 stainless alloy into both ends of the shaft. The shaft was inserted into the molded sleeves, thereby preparing a sleeve bearing as shown in FIG. 4. It was used for sleeve bearings  2  and  2 ′ of the rotor assembly shown in FIG. 1 and FIG. 2.  
         [0060]    The compositions of RBC or CRBC and resins used in Example 5 through Example 9 were prepared by using the same RBC or CRBC fine powder as produced in Example 1 through Example 4 and by dispersing the fine powder of the RBC or the CRBC in resins under the conditions as indicated in Table 1. In addition, for the sake of comparison, commercially available PPS resin for pumps used in water (made by Idemitsu Sekiyu Kagaku K., K. Co., Ltd.) was used.  
                                                                         TABLE 1                                   Composition   Composition   Composition   Composition   Composition               5   6   7   8   9   Ex. For comp.                                    Types of RBC   One used in   One used in   One used in   One used in   One used in   —       and CRBC   Ex. 4   Ex. 3   Ex. 1   Ex. 2   Ex. 2       fine powder       Synthetic   Nylon 66   PBT   PP   PPS   Nylon 66   PPS       resin       Finepowder:   70:30   50:50   70:30   50:50   30:70   —       resin (ratio by       mass)                                          
 
         [0061]    The characteristics of the compositions of the RBC or CRBC fine power, and resins, and the PPS resin used in the sleeve bearing for use in water of Example 1 through Example 9 are summarized in Table 2.  
                                                                 TABLE 2                                   Tensile strength   Bending strength   Bending   Resistivity (ohm   Specific           (MPa)   (MPa)   elasticity (GPa)   cm)   gravity                                    Composition of Ex. 1   64.6   98.6   6.12   4.9 E+01   1.35       Composition of Ex. 2   61.4   97.6   6.14   3.2E+01   1.38       Composition of Ex. 3   76.5   120   8.85   2.1E+01   1.43       Composition of Ex. 4   75.9   117   8.56   3.4E+01   1.38       Composition of Ex. 5   58.2   105   4.12   3.3E+01   1.27       Composition of Ex. 6   49.6   72.3   7.5   3.3E+01   1.46       Composition of Ex. 7   22.7   44.3   6.5   3.8E+01   1.32       Composition of Ex. 8   79.2   121   7.6   4.0E+01   1.48       Composition of Ex. 9   57.3   101   4.3   2.7E+01   1.24       PPS in Ex. For compar.   159   235   14.1   1.0E+16   1.75                  
 
       EXAMPLE 5  
       [0062]    The synthetic resin composition 5 listed in Table 1 was injection molded, thereby preparing a sleeve of 22 mm in outer diameter, 8 mm in inner diameter, and 20 mm in length having a spiral groove of 0.1 mm in depth on the inner side. A shaft of 7.95 mm in outer diameter and 200 mm in length made of SUS bearing steel was inserted into the molded sleeves, thereby preparing sleeve bearings shown in FIG. 3. These sleeve bearings were used for sleeve bearings  2  and  2 ′ of the rotor assembly shown in FIG. 1 and FIG. 2.  
       EXAMPLE 6  
       [0063]    The synthetic resin composition 6 listed in Table 1 was injection molded, thereby preparing a shaft of 7.95 mm in outer diameter, and 200 mm in length. Sleeves  22  mm in outer diameter, 8 mm in inner diameter, and 120 mm in length were made from SUS bearing steel. The sleeves were inserted on the shaft to form sleeve bearings as shown in FIG. 3. These sleeve bearings were used for sleeve bearings  2  and  2 ′ of the rotor assembly shown in FIG. 1 and FIG. 2.  
       EXAMPLE 7  
       [0064]    The synthetic resin composition 7 listed in Table 1 was injection molded, thereby preparing a shaft of 7.95 mm in outer diameter, and 200 mm in length having a spiral groove of 0.1 mm in depth. Sleeves 22 mm in outer diameter, 8 mm in inner diameter and 20 mm in length were made from SUS bearing steel. The sleeves were inserted on the shaft to form sleeve bearings as shown in FIG. 3. These sleeve bearings were used for sleeve bearings  2  and  2 ′ of the rotor assembly shown in FIG. 1 and FIG. 2.  
       EXAMPLE 8  
       [0065]    The synthetic resin composition 8 listed in Table 1 was injection molded, to prepare two sleeves of 22 mm in outer diameter, 8 mm in inner diameter, and 20 mm in length. A shaft of 7.95 mm in outer diameter and 200 mm in length made of SUS bearing steel having a spiral groove of 0.1 mm in depth was inserted into the sleeves, thereby preparing sleeve bearings as shown in FIG. 3. These sleeve bearings were used for sleeve bearings  2  and  2 ′ of the rotor assembly shown in FIG. 1 and FIG. 2.  
       EXAMPLE 9  
       [0066]    The synthetic resin composition 9 listed in Table 1 was injection molded, thereby preparing a shaft of 7.95 mm in outer diameter, and 200 mm in length having a spiral groove of 0.1 mm in depth. Sleeves 22 mm in outer diameter, 8 mm in inner diameter and 20 mm in length were made from SUS bearing steel. The sleeves were inserted on the shaft to form sleeve bearings as shown in FIG. 3. These sleeve bearings were used for sleeve bearings  2  and  2 ′ of the rotor assembly shown in FIG. 1 and FIG. 2.  
         [0067]    Example for Comparison  
         [0068]    The commercially available PPS resin for pump for use with water (made by Idemitsu Sekiyu Kagaku K., K., Co., Ltd.) was injection molded, thereby preparing sleeves 22 mm in outer diameter, 8 mm in inner diameter and 20 mm in length. A shaft of 7.95 mm in outer diameter and 200 mm in length made of SUS 303 stainless alloy was inserted into the sleeves, thereby preparing a sleeve bearing as shown in FIG. 3. These sleeve bearings were used for sleeve bearings  2  and  2 ′ of the rotor assembly shown in FIG. 1 and FIG. 2.  
         [0069]    The frictional characteristics in water of the sleeve bearings for sliding motion in water obtained in Example 1 through Example 9 and in Example for Comparison are summarized in Table 3.  
                                                                                                         TABLE 3                                                                       Ex. For           Ex. 1   Ex. 2   Ex. 3   Ex. 4   Ex. 5   Ex. 6   Ex. 7   Ex. 8   Ex. 9   compare                                    Shape of                   Sleeve                           bearing                   helix       Frictiona   0.212   0.198   0.259   0.221   0.231   0.288   0.232   0.288   0.268   0.406       1 coeff. μ       A       Frictiona   0.182   0.212   0.234   0.209   0.239   0.268   0.195   0.259   0.252   0.413       1 coeff. μ       B       Frictiona   0.194   0.195   0.238   0.184   0.228   0.268   0.188   0.213   0.244   0.388       1 coeff. μ       C       Frictiona   0.138   0.167   0.211   0.177   0.172   0.229   0.162   0.198   0.212   0.259       1 coeff. μ       D       Frictiona   0.156   0.182   0.204   0.195   0.172   0.213   0.159   0.156   0.218   0.213       1 coeff. μ       E       Frictiona   0.148   0.153   0.204   0.152   0.153   0.187   0.168   0.177   0.196   0.248       1 coeff. μ       F                                                                  
 
         [0070]    As can be clearly seen from the results given in Table 3, the pumps for use with water which use the sleeve bearings made from the synthetic resin compositions of fine powder of RBC and CRBC and the resins are markedly excellent in frictional characteristics in water. Additionally, an electrically motorized pump for use in water which does not require any seal between the impeller side and the rotor side of a pump, allows a water fluid to freely flow, saves power consumption, allows cooling water for a water-cooled engine to be effectively circulated and is low in energy loss.  
         [0071]    While a preferred embodiment of the invention has been described, various modifications will be apparent to one skilled in the art in light of this disclosure and are intended to fall within the scope of the appended claims.