JP5925553B2 - Variable displacement axial piston pump cradle guide and variable displacement axial piston pump - Google Patents

Description

  The present invention relates to a cradle guide that slides in contact with a cradle that changes the stroke of a piston of a variable displacement axial piston pump and holds the cradle in a swingable manner, and a variable displacement axial piston pump using the cradle guide.

  For example, a structure of a so-called cradle type pump (hereinafter also simply referred to as “pump”) is well known as a variable displacement type piston pump used as a hydraulic pressure generation source of a hydraulic circuit. In the cradle type pump, a cylinder block that accommodates a piston is integrally rotated together with a rotating shaft, and the cradle is slidably contacted with the cradle guide and supported so as to be inclined with respect to the rotating shaft. It contacts the inclined surface of the cradle via the connected shoe. Therefore, the piston reciprocates with a stroke defined according to the inclination angle of the cradle with the rotation of the rotating shaft, and has a pump action. The discharge capacity of the pump due to the stroke difference can be constantly changed by controlling the inclination angle of the cradle with respect to the rotation axis by hydraulic pressure or the like.

  However, for example, when a cradle made of an aluminum material (including an aluminum alloy) is held in sliding contact with a cradle guide made of the same aluminum material, the tilt angle of the cradle with respect to the rotation axis is constantly controlled by hydraulic pressure or the like. Both cause sliding wear and cause problems such as seizure. For this reason, a means has been adopted in which a synthetic resin thrust bushing is interposed between the cradle and the cradle guide.

  For example, as a thrust bush serving as a cradle guide, a metal thrust bushing having a sliding surface provided with a resin film, a nylon (polyamide resin), a polyacetal resin, a polytetrafluoroethylene (hereinafter referred to as PTFE) resin, or the like is used. A thrust bush made of a dynamic resin is known (see Patent Document 1).

  At least one of an aluminum material cradle or a cradle guide is coated with a fluorine resin coating such as an ethylene-tetrafluoroethylene copolymer (ETFE) resin, a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, or a PTFE resin. An applied variable displacement piston pump is also known (see Patent Document 2).

  Further, as a thrust bush serving as a cradle guide, there are known a thrust bush in which a copper-based sintered film is formed on the surface of an iron base, and a thrust bush in which a resin film is further applied to the surface of the sintered film (see Patent Document 3). ).

Utility Model Registration No. 2559510 JP-A-08-334081 Utility Model Registration No. 2584135

  However, when the cradle normally slides in contact with the cradle guide at a high surface pressure of about 30 MPa, the cradle guide (thrust bush) described in Patent Document 1 satisfies the load resistance due to the resin film. There is a problem that you can not.

  The problem regarding the load resistance in this application is that a fluororesin coating such as PTFE resin described in Patent Document 2 is formed on the surface of a cradle guide made of aluminum, or the iron base material described in Patent Document 3 is used. If a fluororesin coating is formed on the surface via a copper-based sintered film, the coating is improved, but in that case, the wear resistance and the low friction characteristics are not sufficient.

  In addition, when forming a coating (coating) layer on a steel sheet, spraying, drying, firing and the like are necessary, and processing with a lathe or a polishing machine is necessary after the formation, resulting in an increase in manufacturing cost.

  The present invention has been made to cope with such problems, and is a variable capacity type axial which can satisfy all of load resistance, wear resistance and low friction characteristics of 30 MPa or more while being easy to manufacture and low cost. An object of the present invention is to provide a cradle guide for a piston pump and a variable displacement axial piston pump using the cradle guide.

  A cradle guide according to the present invention is a cradle guide that is slidably contacted with a cradle that adjusts a piston stroke in a variable displacement axial piston pump and holds the cradle so that the cradle can swing. And a resin layer made of a resin composition having an aromatic polyetherketone resin as a base resin, and the resin layer has a surface in contact with at least the cradle of the sintered metal member. It has a thickness of 1 to 0.7 mm and is integrally provided by injection molding.

  The resin composition includes a fibrous filler, and in the resin layer, the fibrous filler is oriented so that the length direction of the fiber intersects 45 to 90 degrees with respect to the sliding direction of the cradle guide. It is characterized by being.

  The sintered metal member is a cradle guide body. As another aspect, the cradle guide has a cradle guide main body made of molten metal, and the sintered metal member is installed on the cradle guide main body.

  The sintered metal member has a theoretical density ratio of 0.7 to 0.9. The sintered metal member is made of a sintered metal containing iron as a main component.

The fibrous filler is a carbon fiber. Moreover, the said resin composition contains 5-30 volume% of said carbon fibers, and 1-30 volume% of PTFE resin with respect to this resin composition whole, It is characterized by the above-mentioned. The resin composition is a resin composition having a melt temperature of 50 to 200 Pa · s at a resin temperature of 380 ° C. and a shear rate of 1000 s ⁻¹ .

  A variable displacement axial piston pump according to the present invention includes the cradle guide according to the present invention.

  The cradle guide of the variable capacity type piston pump of the present invention is based on a sintered metal member and an aromatic polyether ketone resin formed on the surface of the sintered metal member that is in sliding contact with at least the cradle. Therefore, there is an advantage that the cradle guide is excellent in heat resistance, low friction and wear resistance. In addition, since the resin layer is integrally formed by injection molding with a thickness of 0.1 to 0.7 mm on the surface of the sintered metal member, it is excellent in load resistance and creep resistance, It is possible to stably obtain a low torque without changing dimensions even under surface pressure. As a result, there is an advantage that the cradle guide can be used for a long period of time by satisfying all of the load resistance, wear resistance and low friction characteristics even in a high-pressure sliding state of 30 MPa or more. Further, the resin layer is integrally provided on the surface of the sintered metal member by injection molding, that is, the resin layer is formed by injection molding by inserting the sintered metal member into the mold. There is no need to form a coating layer (spraying, drying, firing, etc.) on a steel plate like a cradle guide, and there is no need for processing with a lathe or a polishing machine. The sliding surface has high dimensional accuracy.

  Since a fibrous filler is included in the resin composition, the heat resistance, wear resistance, load resistance, and creep resistance of the resin layer can be further increased. Further, since the fibrous filler in the resin layer is oriented so that the length direction of the fiber intersects 45 to 90 degrees with respect to the sliding direction of the cradle guide, the both ends of the fibrous filler Aggressiveness to the mating material surface can be reduced, and fluctuations in sliding torque can be prevented.

  Since the sintered metal member is a cradle guide body, the number of parts is small, the structure is simple, and the manufacturing cost is low.

  Further, as another aspect, further comprising a cradle guide body made of molten metal, by installing the sintered metal member in the cradle guide body, while ensuring high mechanical strength as a whole cradle guide, The above-mentioned effect can be obtained by using a sintered metal member and a thin-walled injection molded resin layer. Moreover, in this aspect, since the conventional cradle guide main body can be used, a design change etc. are unnecessary and it can prevent a cost increase.

  Since the theoretical density ratio of the sintered metal member is 0.7 to 0.9, the resin layer is sintered with the required denseness to ensure the structural strength of the sintered metal member. Unevenness on the surface can be ensured for tight adhesion to the metal member. Moreover, it is possible to hold | maintain lubricating oil to a sintered metal member. Furthermore, the thermal conductivity of the sintered metal member can be ensured.

  Since the sintered metal member is made of a sintered metal containing iron as a main component, higher mechanical strength can be obtained.

  Since the fibrous filler is carbon fiber, the reinforcing effect, abrasion resistance, and low friction properties of the resin layer are particularly excellent.

  Since the resin composition forming the resin layer contains 5 to 30% by volume of carbon fiber and 1 to 30% by volume of PTFE resin as a fibrous filler with respect to the entire resin composition, even under high PV conditions, The deformation and wear of the resin layer, the aggressiveness to the mating material surface are small, and the resistance to oil and the like is high.

Since the resin composition forming the resin layer is a resin composition having a melt temperature of 50 to 200 Pa · s at a resin temperature of 380 ° C. and a shear rate of 1000 s ⁻¹ , the surface of the sintered metal member is 0.1 to 0.00. 7mm thin insert molding can be performed smoothly.

  Since the variable displacement axial piston pump of the present invention includes the cradle guide of the present invention, it is possible to precisely control the tilt angle of the cradle, thereby performing a precise hydraulic control operation, etc. Become a high pump.

It is a longitudinal section of a variable capacity type axial piston pump using a cradle guide of the present invention. It is a perspective view which shows an example of the cradle guide of this invention. It is a perspective view which shows the other example of the cradle guide of this invention. FIG. 4 is an exploded perspective view of the cradle guide of FIG. 3. It is a perspective view which shows the other example of the cradle guide of this invention. It is sectional drawing of a cradle guide.

  An embodiment of a variable displacement axial piston pump using the cradle guide of the present invention will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of a variable displacement axial piston pump. As shown in FIG. 1, a cradle guide 1 of a variable displacement axial piston pump is in sliding contact with a cradle 3 that adjusts the stroke of a piston 2 and holds the cradle 3 so that it can swing. Here, the cradle guide 1 has a resin layer 1b made of a resin composition containing an aromatic polyetherketone resin as a base resin on the surface side of the sintered metal member 1a, that is, the sliding surface with respect to the cradle 3. The thickness is 1 to 0.7 mm and is provided integrally by injection molding. In addition, although the resin layer 1b is thin with the thickness of the said range, in FIG. 1, it has described thicker than actual for description.

  In the variable displacement axial piston pump of this embodiment, a rotary shaft 7 is rotatably supported between end walls of a pair of housings 5 and 6 joined together. A cylinder block 8 is supported on the rotating shaft 7 so as not to be relatively rotatable. A plurality of pistons 2 are accommodated in a cylinder block 8 that rotates integrally with the rotary shaft 7 so as to be slidable in the axial direction of the rotary shaft 7. The piston accommodating chamber 8a in the cylinder block 8 is alternately connected to the arc-shaped suction port 9a and discharge port 9b formed in the valve plate 9 in conjunction with the rotation of the rotary shaft 7. As a result, the hydraulic oil is sucked into the piston accommodating chambers 8a from the suction ports 9a, and the hydraulic oil in the piston accommodating chambers 8a in the cylinder block 8 rotated together with the rotary shaft 7 is discharged to the discharge port 9b.

  The pressing spring 10 biases the cylinder block 8 toward the cradle 3 side. Accordingly, the shoe 12 made of an aluminum material held by the retainer 11 is in close contact with the flat portion of the cradle 3 around the rotation shaft 7. The piston 2 fitted to the shoe 12 is reciprocated with a stroke corresponding to the inclination angle of the cradle 3 as the rotary shaft 7 rotates. The tilt angle of the cradle 3 is always controlled to an appropriate angle by the pressing force of the pressing spring 13 in the housing 5 and the hydraulic pressure from the cylinder 15 adjusted by the hydraulic control device 14.

  FIG. 2 is a perspective view of the cradle guide 1. As shown in FIGS. 1 and 2, two cradle guides 1 are fixed and provided in a housing 5 made of an aluminum alloy. A rotating shaft 7 is disposed between the two cradle guides 1 so as to penetrate the shaft hole of the cradle 3.

  In the embodiment shown in FIG. 2, the main body of the cradle guide 1 is composed of a sintered metal member 1a. In this main body, the support surface of the cradle 3 is formed in an arcuate shape, and a resin layer 1b having a predetermined composition is formed on the support surface with a thin wall and a constant thickness by injection molding. The arc surface on which the resin layer 1b is formed becomes a sliding surface with respect to the cradle 3. By making the cradle guide body a sintered metal member, the number of parts is small, the structure is simple, and the manufacturing cost is low.

  Another embodiment of the cradle guide will be described with reference to FIGS. FIG. 3 is a perspective view of another embodiment of the cradle guide 1, and FIG. 4 is an exploded perspective view of the cradle guide of FIG. As shown in FIG. 3, the cradle guide 1 includes a molten metal main body 1c, and a sintered metal member 1a in which a resin layer 1b is formed is installed on the main body 1c. The sintered metal member 1a is an arc-shaped (partially cylindrical) sintered bush formed with a resin layer 1b, and is set on the support surface of the cradle 3 formed in an arc surface shape in the main body 1c. . The surface on the main body 1c side of the sintered metal member 1a is formed in the same shape corresponding to the arc surface shape of the support surface of the main body 1c. The arc surface on which the resin layer 1b of the sintered bush is formed becomes a sliding surface with respect to the cradle 3. Further, as shown in FIG. 4, the pair of concave portions 1f and convex portions 1g are fitted so that the pair of sintered bushes (1a + 1b) does not deviate from the support surfaces 1d and 1e of the cradle guide of the main body 1c. It is fixed with. In addition, the uneven | corrugated | grooved part for fixing a sintered bush may make the uneven | corrugated relationship opposite to what is shown in FIG. 4, and the shape can also be made into arbitrary shapes. Alternatively, it is most desirable to insert the pin into the recess 1 f and fit the sintered bush by providing a pin hole in consideration of the manufacturing cost.

  The cradle 3 is formed of, for example, a silicon-containing aluminum alloy, and a pair of arcuate sliding contact portions 3a and 3b corresponding to the support surfaces 1d and 1e of the cradle guides are provided on the back surface thereof. In the embodiment shown in FIGS. 3 and 4, the sliding contact portions 3a and 3b are assembled so as to be in contact with the support surfaces 1d and 1e through a pair of sintered bushes (1a + 1b).

  3 and FIG. 4, the material of the cradle guide body 1c is not particularly limited as long as it is a molten metal. For example, high carbon chromium bearing steel, chromium molybdenum steel, carbon steel for machine structure, stainless steel, cast iron, aluminum alloy, brass and the like can be used. By making the main body 1c made of molten metal, the mechanical strength of the entire cradle guide can be increased as compared with the case where the whole main body is made of a sintered metal member.

  The resin layer 1b is made of a resin composition having an aromatic polyetherketone resin as a base resin, and is formed by injection molding at a thickness of 0.1 to 0.7 mm on the surface in sliding contact with the cradle of the sintered metal member 1a. It is formed by overlapping and providing integrally.

  Since the resin layer 1b is formed on the surface of the sintered metal member 1a, the molten resin of the aromatic polyether ketone resin penetrates deeply into the irregularities on the surface of the sintered metal member 1a during the injection molding, and the resin layer 1b Can be firmly attached to the member 1a. In injection molding, the molten resin is poured at a high speed and high pressure, so the aromatic polyetherketone resin is used as the base resin, but the resin easily enters the irregularities (voids) of the porous sintered layer due to the shearing force. . Therefore, the adhesion strength between the sintered metal member 1a and the resin layer 1b can be secured.

  By using a resin composition based on an aromatic polyether ketone resin as the resin layer 1b, the continuous use temperature is 250 ° C., heat resistance, oil / chemical resistance, creep resistance, friction wear It becomes a cradle guide for variable displacement axial piston pumps with excellent characteristics. In addition, aromatic polyetherketone-based resins have high toughness, high mechanical properties at high temperatures, and excellent fatigue resistance and impact resistance, so when frictional force, impact, vibration, etc. are applied during use, The resin layer is difficult to peel from the sintered metal member. In the cradle guide of the conventional variable capacity type axial piston pump, since the resin composition mainly composed of a fluororesin such as PTFE resin is a sliding surface, the resin composition peels off from the porous sintered layer at the time of abnormality. I couldn't prevent that.

  Examples of the aromatic polyether ketone resin that can be used in the present invention include polyether ether ketone (PEEK) resin, polyether ketone (PEK) resin, and polyether ketone ether ketone ketone (PEKEKK) resin. Examples of commercially available PEEK resins that can be used in the present invention include: Victorex: PEEK (90P, 150P, 380P, 450P, 90G, 150G, etc.), Solvay Advanced Polymers: KetaSpire (KT-820P, KT-880P) Etc., manufactured by Daicel Degussa, Inc .: VESTAKEEEP (1000G, 2000G, 3000G, 4000G, etc.). Examples of the PEK resin include Victrex-HT manufactured by Victrex, and examples of the PEKKK resin include Victrex-ST manufactured by Victrex.

  The thickness of the resin layer 1b is set to 0.1 to 0.7 mm. The “resin layer thickness” in the present invention is the thickness of the surface portion that does not enter the sintered metal member. This thickness range is set in consideration of the insert molding surface and physical properties. When the thickness of the resin layer is less than 0.1 mm, insert molding is difficult. In addition, durability during long-term use, that is, life may be shortened. On the other hand, if the thickness of the resin layer exceeds 0.7 mm, sink marks may occur and dimensional accuracy may be reduced. In addition, heat due to friction is difficult to escape from the friction surface to the sintered metal member, and the friction surface temperature increases. Further, the amount of deformation due to the load increases, the true contact area on the friction surface also increases, the frictional force and the frictional heat generation increase, and the seizure resistance may decrease. In consideration of heat dissipation of the frictional heat generation to the sintered metal member, the thickness of the resin layer is preferably 0.2 to 0.5 mm.

  Moreover, in the aspect using a sintered bush as shown in FIG. 3, it is preferable that the thickness of the resin layer 1b is 1/8 to 1/2 of the thickness of the sintered metal member 1a. If the thickness of the resin layer is less than 1/8 of the thickness of the sintered metal member, the resin layer becomes too thin relative to the sintered metal member, which may be inferior in durability during long-term use. . On the other hand, if the thickness of the resin layer exceeds ½ of the thickness of the sintered metal member, the resin layer becomes too thick relative to the sintered metal member, and heat due to friction is burned from the friction surface. It is difficult to escape to the metal member, and the friction surface temperature becomes high. Further, the amount of deformation due to the load increases, the true contact area on the friction surface also increases, the frictional force and the frictional heat generation increase, and the seizure resistance may decrease.

  Examples of the material of the sintered metal member 1a include iron, copper iron, copper, and stainless steel. Since the adhesion between the sintered metal member and the resin layer is excellent, it is preferable to employ a sintered metal whose main component is iron (which may include copper). In addition, since copper is inferior to adhesiveness (adhesiveness) with resin rather than iron, when copper is included, content of copper is 10 weight% or less. More preferably, the copper content is 5% by weight or less.

  When there is oil adhesion or oil impregnation on the sintered metal member, oil residue decomposed and gasified at the time of injection molding of the resin layer is present at the interface, so the adhesion between the resin layer and the sintered metal member May decrease. Therefore, it is preferable to use a sintered metal not impregnated with oil for the sintered metal member before the resin layer is formed. Moreover, when using oil in the process of shaping | molding or re-pressing (sizing) of a sintered metal, it is preferable to set it as the non-oil-containing sintered metal which removed oil by solvent washing etc.

  Sintered metal components mainly composed of iron are treated with a steam treatment to remove oil or deposits that have unintentionally adhered to the sintered surface or penetrated inside during the molding or re-pressure (sizing) process. Therefore, variation in adhesion with the resin layer is small and stable. Moreover, antirust property can also be provided to a sintered metal member. The conditions for the steam treatment are not particularly limited, but a method of spraying steam heated to about 500 ° C. is common.

  The theoretical density ratio of the sintered metal member is preferably 0.7 to 0.9. The theoretical density ratio of the material is the ratio of the density of the sintered metal member when the theoretical density of the material (density when the porosity is 0%) is 1. If the theoretical density ratio is less than 0.7, the strength of the sintered metal member becomes low, and the member may be broken by the injection molding pressure at the time of insert molding. On the other hand, when the theoretical density ratio exceeds 0.9, the unevenness is reduced, so that the surface area and the anchor effect are lowered, and the adhesion with the resin layer is lowered. More preferably, the theoretical density ratio of the materials is 0.72 to 0.84. In this way, by setting the theoretical density ratio of the sintered metal member to 0.7 to 0.9, the strength of the cradle guide carried by the sintered metal member (particularly, the entire body is composed of the sintered metal member). In the case where the resin layer is sufficiently dense, and the unevenness of the surface for firmly attaching the resin layer to the sintered metal member can be ensured. It is also possible to hold the lubricating oil on the sintered metal member. Furthermore, the thermal conductivity of the sintered metal member can be ensured.

  The resin composition forming the resin layer uses an aromatic polyether ketone-based resin as a base resin, and a fibrous filler such as glass fiber, carbon fiber, aramid fiber, or whisker can be blended in a dispersed state. . Thereby, the mechanical strength of the resin layer can be further improved. In particular, in the cradle guide of the variable displacement axial piston pump of the present invention, since the resin layer is thin with a thickness of 0.1 to 0.7 mm, it is desirable to improve the mechanical strength.

  In addition to the fibrous filler, a solid lubricant such as PTFE resin, graphite, and molybdenum disulfide, and an inorganic filler such as calcium carbonate, calcium sulfate, mica, and talc can be blended. By blending the above-mentioned solid lubricant, it is possible to improve the seizure resistance by reducing friction even under non-lubricated conditions and even when the lubricating oil is dilute. Moreover, creep resistance can be improved by mix | blending the said inorganic filler.

  Fibrous fillers, inorganic solid lubricants (such as graphite and molybdenum disulfide), and inorganic fillers have the effect of reducing the molding shrinkage of aromatic polyether ketone resins. Therefore, there is also an effect of suppressing the internal stress of the resin layer at the time of insert molding with a sintered metal member.

  FIG. 5 shows a cradle guide having an embodiment having a resin layer made of a resin composition containing a fibrous filler. FIG. 5 is a perspective view of a cradle guide (containing a fibrous filler in a resin layer). The cradle guide 1 has the same configuration as that of FIG. 2 except that the fibrous filler 4 is blended in the resin layer 1b.

  In forming the resin layer 1b by injection molding, by adjusting the melt flow direction of the resin composition, the fibrous filler 4 (in its length direction) is moved with respect to the sliding direction of the cradle guide 1 (arrow in the figure). It is preferable to align at an intersecting angle as close to a right angle as possible at least 45 degrees. In order to improve the mechanical strength of the resin layer 1b, it is preferable to blend a fibrous filler. However, since the end of the fiber of the fibrous filler has an edge shape, the end of the fiber is used as a counterpart material. The cradle 3 is easily subject to physical wear damage and the friction coefficient is difficult to stabilize. By orienting the fibrous filler (in its length direction) so as to intersect at 45 to 90 degrees with respect to the sliding direction of the cradle guide, the edges at both ends of the fiber are 45 to 90 with respect to the sliding direction. Suitable for degrees. As a result, it is possible to reduce wear damage of the mating member due to the edges at both ends of the fiber and stabilize the friction coefficient. It should be noted that the orientation of the fibrous filler is preferably closer to 90 degrees because there is less abrasion damage due to the fiber edge and the friction coefficient is stabilized. If it is 80-90 degree | times, it is especially preferable.

  The average fiber length of the fibrous filler is preferably 0.02 to 0.2 mm. If the thickness is less than 0.02 mm, a sufficient reinforcing effect cannot be obtained, and creep resistance and wear resistance may not be satisfied. When the thickness exceeds 0.2 mm, the ratio of the fiber length to the layer thickness of the resin layer becomes large, so that the thin moldability is poor. In particular, when insert molding is performed with a resin thickness of 0.2 to 0.7 mm, if the fiber length exceeds 0.2 mm, the thin moldability is impaired. In order to further improve the stability of thin-wall molding, an average fiber length of 0.02 to 0.1 mm is desirable.

  Among the fibrous fillers, it is preferable to use carbon fibers. Carbon fiber has a strong orientation in the melt flow direction of the resin when the resin layer is molded. In particular, a carbon fiber having a small diameter and a relatively short length is selected, and in this case, the edges at both ends of the carbon fiber are along the sliding direction of the cradle guide, for example, the orientation direction is 0 to less than 45 degrees. The opponent's cradle may be damaged. Therefore, when thin and short carbon fibers are used, when the resin is injection molded, the flow direction of the molten resin is set to a right angle or a near right angle with the sliding direction of the cradle guide, and the length direction of the fiber is set to the cradle. It is extremely advantageous to orient the guides so as to be 45 to 90 degrees with respect to the sliding direction in order to stabilize the durability and sliding torque.

  The carbon fibers used in the present invention may be either pitch-based or PAN-based ones classified from raw materials, but PAN-based carbon fibers having a high elastic modulus are preferred. The firing temperature is not particularly limited, but a carbonized product fired at about 1000 to 1500 ° C. is higher than that fired at a high temperature of 2000 ° C. or higher and converted to graphite (graphite). Even under PV, it is preferable because the mating material is hardly damaged by wear.

  The average fiber diameter of the carbon fibers is 20 μm or less, preferably 5 to 15 μm. Thick carbon fiber exceeding this range generates extreme pressure, so the effect of improving load resistance is poor, and when the cradle, which is the counterpart material, is an aluminum alloy or non-quenched steel material, the wear damage of the counterpart material increases. Therefore, it is not preferable. The carbon fiber may be a chopped fiber or a milled fiber, but a milled fiber having a fiber length of less than 1 mm is preferable in order to obtain stable thin-wall formability.

  Examples of commercially available carbon fibers that can be used in the present invention include pitch-based carbon fibers manufactured by Kureha Co., Ltd .: Kureka M-101S, M-107S, M-101F, M-201S, M-207S, M-2007S, C- 103S, C-106S, C-203S and the like. Moreover, as a similar PAN-based carbon fiber, manufactured by Toho Tenax Co., Ltd .: Besfight HTA-CMF0160-0H, HTA-CMF0040-0H, HTA-C6, HTA-C6-S, or Toray Industries, Inc .: Torayca MLD-30 , MLD-300, T008, T010, and the like.

  The resin composition forming the resin layer preferably uses an aromatic polyether ketone resin as a base resin, and contains the carbon fiber and a PTFE resin as a solid lubricant as essential components.

  As the PTFE resin, any of molding powder by suspension polymerization, fine powder by emulsion polymerization, and recycled PTFE may be used. In order to stabilize the fluidity of a resin composition comprising an aromatic polyetherketone resin as a base resin, it is preferable to employ regenerated PTFE which is difficult to be fiberized by shearing during molding and hardly increases the melt viscosity.

  Regenerated PTFE is a powder that has been irradiated with a heat-treated powder (heated history added), γ-rays or electron beams. For example, a powder obtained by heat-treating molding powder or fine powder, a powder obtained by further irradiating this powder with γ-rays or an electron beam, a powder obtained by pulverizing a molding powder or a molded product of fine powder, and then a γ-ray or electron beam. There are types such as irradiated powder, molding powder or fine powder irradiated with gamma rays or electron beams. Among the regenerated PTFE, a resin composition comprising an aromatic polyether ketone resin as a base resin that does not aggregate, does not fiberize at the melting temperature of the aromatic polyether ketone resin, has an internal lubricating effect, and Since fluidity can be stably improved, it is more preferable to use PTFE resin irradiated with γ rays or electron beams.

  Examples of commercially available PTFE resins that can be used in the present invention include Kitamura Co., Ltd .: KTL-610, KTL-450, KTL-350, KTL-8N, KTL-400H, Mitsui DuPont Fluorochemical Co., Ltd .: Teflon (registered trademark). 7-J, TLP-10, Asahi Glass Co., Ltd .: Fullon G163, L150J, L169J, L170J, L172J, L173J, Daikin Industries, Ltd .: Polyflon M-15, Lubron L-5, Hoechst: Hostaflon TF9205, TF9207, etc. Can be mentioned. Further, it may be a PTFE resin modified with a perfluoroalkyl ether group, a fluoroalkyl group, or another side chain group having a fluoroalkyl group. Among the PTFE resins irradiated with γ rays or electron beams among the above, Kitamura Co., Ltd .: KTL-610, KTL-450, KTL-350, KTL-8N, KTL-8F, Asahi Glass Co., Ltd .: Fullon L169J, L170J , L172J, L173J, and the like.

  In addition, you may mix | blend a well-known resin additive with respect to a resin composition to such an extent that the effect of this invention is not inhibited. Examples of the additive include friction property improvers such as boron nitride, colorants such as carbon powder, iron oxide, and titanium oxide, and thermal conductivity improvers such as graphite and metal oxide powder.

  The resin composition for forming the resin layer preferably includes an aromatic polyether ketone resin as a base resin, 5 to 30% by volume of carbon fiber, and 1 to 30% by volume of PTFE resin as essential components. The balance excluding this essential component and other additives is an aromatic polyether ketone resin. By adopting this blending ratio, even under high PV conditions, the deformation and wear of the resin layer, the aggressiveness to the cradle surface as the counterpart material are small, and the resistance to oil and the like is also high. Further, the carbon fiber is more preferably 5 to 20% by volume, and the PTFE resin is more preferably 2 to 25% by volume.

  If the mixing ratio of the carbon fiber exceeds 30% by volume, the melt fluidity is remarkably lowered, making it difficult to form a thin wall, and when the cradle as the counterpart material is an aluminum alloy or non-quenched steel, there is a risk of wear damage. is there. Moreover, when the blending ratio of the carbon fiber is less than 5% by volume, the effect of reinforcing the resin layer is poor, and sufficient creep resistance and wear resistance may not be obtained.

  If the blending ratio of the PTFE resin exceeds 30% by volume, the wear resistance and creep resistance may be lowered from the required levels. In addition, when the blending ratio of the PTFE resin is less than 1% by volume, the effect of imparting the required lubricity to the composition is poor, and sufficient sliding characteristics may not be obtained.

  The means for mixing and kneading the above raw materials is not particularly limited, and only the powder raw material is dry-mixed with a Henschel mixer, ball mixer, ribbon blender, ladyge mixer, ultra Henschel mixer, etc. Melting and kneading can be performed with a melt extruder such as an extruder to obtain molding pellets (granules). In addition, a side feed may be used for charging the filler when melt kneading with a twin screw extruder or the like. Using this pellet for molding, a resin layer is injection-molded by insert molding on a sintered metal member. By adopting injection molding, it is excellent in precision moldability and manufacturing efficiency. Moreover, you may employ | adopt treatments, such as an annealing process, for physical property improvement.

The resin composition forming the resin layer preferably has a melt viscosity of 50 to 200 Pa · s at a resin temperature of 380 ° C. and a shear rate of 1000 s ⁻¹ . When the melt viscosity is within this range, precise molding and fibrous filler can be oriented at a predetermined angle, and thin insert molding of 0.1 to 0.7 mm can be smoothly performed on the surface of a sintered metal member. It can be done. If the melt viscosity is less than the predetermined range or exceeds the predetermined range, it is not easy to reliably obtain a precise moldability and to orient the fibrous filler at a predetermined angle. By making thin insert molding possible and making post-processing after insert molding unnecessary, manufacturing becomes easy and manufacturing costs can be reduced.

In order to set the melt viscosity at a resin temperature of 380 ° C. and a shear rate of 1000 s ⁻¹ to 50 to 200 Pa · s, it is preferable to employ an aromatic polyether ketone resin having a melt viscosity of 130 Pa · s or less under these conditions. An example of such an aromatic polyether ketone resin is PEEK (90P, 90G) manufactured by Victrex.

  In order to obtain sufficient adhesion strength against the frictional force during use, the shear adhesion strength between the sintered metal member and the resin layer is preferably 2 MPa or more. Furthermore, in order to raise a safety factor, 3 Mpa or more is preferable. Further, in order to further increase the shear adhesion strength between the sintered metal member and the resin layer, physical peeling measures such as unevenness and grooves may be taken on the sintered metal surface on which the resin layer is formed.

  For example, in order to prevent the resin layer 1b from being peeled off from the sintered metal member 1a during sliding with the cradle, as shown in FIG. 6, irregularities can be provided on the boundary surface. 6A is a cross-sectional view of the cradle guide of the embodiment shown in FIG. 2, and FIG. 6B is a cross-sectional view of the cradle guide of the embodiment shown in FIG. In FIG. 6, by providing a concave portion in the sintered metal member 1a, a convex portion corresponding to this is formed in the resin layer 1b to be injection molded. In addition, the said uneven | corrugated | grooved part may make the uneven | corrugated relationship opposite to what is shown in FIG. 6, and can also make an arbitrary shape.

  Table 1 shows the sintered metal substrates used in the examples and comparative examples.

Moreover, the raw material of the resin layer used for the Example and the comparative example is shown below.
The melt viscosity of the aromatic polyether ketone resin is a measured value at a Capillograph manufactured by Toyo Seiki Co., Ltd., φ1 × 10 mm capillary, a resin temperature of 380 ° C., and a shear rate of 1000 s ⁻¹ .
(1) Aromatic polyether ketone resin [PEK-1]: PEEK 90P (melt viscosity: 105 Pa · s) manufactured by Victrex
(2) Aromatic polyetherketone resin [PEK-2]: PEEK 150P (melt viscosity 145 Pa · s) manufactured by Victrex
(3) PAN-based carbon fiber [CF-1]: Torayca MLD-30 manufactured by Toray Industries, Inc. (average fiber length 0.03 mm, average fiber diameter 7 μm)
(4) PAN-based carbon fiber [CF-2]: Besfight HTA-CMF0160-0H manufactured by Toho Tenax Co., Ltd. (fiber length 0.16 mm, fiber diameter 7 μm)
(5) Pitch-based carbon fiber [CF-3]: Kureha Kureka M-101S (average fiber length 0.1 / 2 mm, average fiber diameter 14.5 μm)
(6) Pitch-based carbon fiber [CF-4]: Kureha Kureka M-107S (average fiber length 0.7 mm, average fiber diameter 14.5 μm)
(7) Calcium carbonate powder [CaCO ₃ ]: NA600 (average particle size: 3 μm) manufactured by Nittsu Kogyo Co., Ltd.
(8) Graphite [GRP]: TIMEX KS6 (average particle size 6 μm) manufactured by Timcal Japan
(9) PTFE resin [PTFE]: Kitamura KTL-610 (regenerated PTFE)

  The raw materials for the resin layer were dry blended using a Henschel dry mixer at the blending ratio (volume%) shown in Table 2, and melt-kneaded using a twin screw extruder to produce pellets for injection molding.

(1) Shear adhesion strength test (Examples 1 to 9, Comparative Example 1)
The shear adhesion strength test was performed using a cylindrical test piece. A cylindrical test piece is formed from a base material A to a base material J shown in Table 1 and a cylindrical base material of φ31 × φ35 × 20 (mm) is formed, and pellets shown in Table 2 are used for this inner diameter. The resin layer has a thickness of 0.5 mm and is manufactured by insert molding. At the time of insert molding, nine pin gates were provided on the end surface of the cylindrical test piece so that the melt flow direction of the resin layer was the axial direction of the cylindrical test piece.

  In the shear adhesion strength test, this cylindrical test piece is fixed, an axial shear force is applied to the resin layer, the load at which the resin layer peels from the sintered metal substrate is measured, and the resin layer Table 3 shows the value obtained by dividing the apparent bonding area of the sintered metal substrate and the shear adhesion strength. In addition, 30 cylindrical test pieces were insert-molded, and the presence or absence of cracks in the cylindrical base material due to the molding pressure was confirmed.

  As shown in Table 3, Examples 1 to 9 were free from cracks in the sintered metal substrate during insert molding, and had a shear adhesion strength of 1.5 MPa or more. In particular, in Examples 1 to 8 using the base materials A to H in which the density of the sintered metal base material is 0.7 to 0.9 of the theoretical density ratio of the materials, the shear adhesion strength was 2 MPa or more. It was. On the other hand, in the steel machined product, the shear adhesion strength was very low (Comparative Example 1).

(2) Seizure resistance test (Examples 10 to 20, Comparative Examples 2 to 3)
The seizure resistance test using an in-oil radial type tester was performed using a cylindrical test piece. The cylindrical test piece is manufactured in the same manner as the cylindrical test piece used for the shear adhesion strength test. Comparative Example 3 is a three-layer type sliding bearing (φ30 × φ35 × 20 mm, resin, in which a porous sintered layer (Cu + Sn) with a back metal (SPCC) is impregnated with a PTFE resin composition (10% by volume of carbon fiber). Layer 0.05 mm). After running-in for 30 minutes under the oil supply conditions shown in Table 4, the time from oil supply stop / oil discharge to seizure was measured. The seizure is shown in Table 5 as the time until the temperature of the outer diameter of the cylindrical test piece increases by 20 ° C. or the torque increases twice.

(3) Wear test About the same cylindrical test piece as the seizure resistance test, the wear amount after operating for 30 hours under the oil supply conditions shown in Table 4 was measured using a radial in-oil tester.

(4) Melt viscosity The melt viscosity at Toyo Seiki Co., Ltd. Capiragraph, φ1 × 10 (mm) capillary, resin temperature 380 ° C., shear rate 1000 s ⁻¹ was measured.

  In Examples 10 to 20, the seizure time was 30 minutes or more, the wear amount was 10 μm or less, and the seizure resistance and the wear resistance were excellent. On the other hand, in Comparative Example 2 in which the thickness of the resin layer exceeded 0.7 mm, the seizure time was less than 1 minute and the amount of wear was very large. Further, in Comparative Example 3, the seizure time was less than 1 minute, and seizure occurred immediately and the amount of wear was large.

(5) Reciprocating test (Example 21, Comparative Example 4)
In Example 21, a test piece was manufactured by forming a resin layer of the resin composition d by insert molding on the surface of a base material E molded into a length of 25 mm, a width of 50 mm, and a height of 20 mm. A reciprocating test was conducted under the following conditions, and the results are shown in Table 6. In insert molding, the melt flow direction of the resin layer was perpendicular to the direction of movement of the test piece. Comparative Example 4 is a three-layer sliding bearing (plate thickness 2.5 mm, resin, impregnated with PTFE resin composition (10% by volume carbon fiber) in a porous sintered layer (Cu + Sn) with a back metal (SPCC). A test piece was manufactured by fixing a layer (0.05 mm) to a pedestal having a length of 25 mm, a width of 50 mm, and a height of 17 mm, and a similar reciprocating test was performed using an aluminum alloy mating member. The results are shown in Table 6. It was.

[Test conditions]
Testing machine: NTN reciprocating testing machine Surface pressure: 45MPa
Maximum excitation speed: 3m / min
Amplitude: + -50mm
Temperature: Room temperature (25 ° C)
Lubrication conditions: Oil lubrication Test time: 2000 reciprocations (initially, 500 times, 1000 times, coefficient of friction is measured)

  In Example 21 according to the present invention, in the reciprocating test, the coefficient of friction was low until the end of the test, and no change was observed in the state of the resin layer. As a result, it was confirmed that the cradle guide of the example can withstand long-term use of the variable displacement piston pump and can satisfy all of the load resistance, wear resistance and low friction characteristics of 30 MPa or more. . On the other hand, in Comparative Example 4, the test was stopped because the friction coefficient increased after 1000 reciprocations.

  The cradle guide of the present invention is easy to manufacture and low in cost, and can satisfy all of load resistance, wear resistance and low friction characteristics of 30 MPa or more. Therefore, the hydraulic source of construction machinery such as a hydraulic excavator and general industrial machinery Can be suitably used in a variable displacement type axial piston pump used for a hydraulic pump or a hydraulic motor provided as the above.

DESCRIPTION OF SYMBOLS 1 Cradle guide 1a Sintered metal member 1b Resin layer 1c Cradle guide main body 1d, 1e Support surface 1f Concave 1g Convex part 2 Piston 3 Cradle 4 Fibrous filler 5, 6 Housing 7 Rotating shaft 8 Cylinder block 8a Piston accommodating chamber 9 Valve plate 9a Suction port 9b Discharge port 10, 13 Press spring 11 Retainer 12 Shoe 14 Hydraulic control device 15 Cylinder

Claims (9)

A cradle guide that slides in contact with a cradle that adjusts a piston stroke in a variable displacement axial piston pump and holds the cradle so that it can swing.
The cradle guide has a sintered metal member and a resin layer made of a resin composition based on an aromatic polyetherketone resin,
The resin composition includes a fibrous filler, and in the resin layer, the fibrous filler is oriented so that the length direction of the fiber intersects 45 to 90 degrees with respect to the sliding direction of the cradle guide. And
The variable capacity is characterized in that the resin layer is an injection-molded layer provided integrally with a thickness of 0.1 to 0.7 mm on the surface of the sintered metal member which is in sliding contact with at least the cradle. Cradle guide for type axial piston pumps.   The cradle guide for a variable displacement axial piston pump according to claim 1, wherein the sintered metal member is a cradle guide body.   2. The variable capacity axial piston pump according to claim 1, wherein the cradle guide has a cradle guide body made of molten metal, and the sintered metal member is installed in the cradle guide body. 3. Cradle guide. Wherein the sintering theoretical density ratio of sintered metal member, cradle guide variable displacement axial piston pump according to any one of claims 1 to 3, characterized in that 0.7 to 0.9. The cradle guide for a variable displacement axial piston pump according to any one of claims 1 to 4 , wherein the sintered metal member is made of a sintered metal containing iron as a main component. The fibrous filler, cradle guide variable displacement axial piston pump according to any one of claims 1 to 5, characterized in that a carbon fiber. 7. The variable capacity type according to claim 6 , wherein the resin composition contains 5 to 30% by volume of the carbon fiber and 1 to 30% by volume of a polytetrafluoroethylene resin with respect to the entire resin composition. Cradle guide for axial piston pumps. Said resin composition is a resin temperature of 380 ° C., variable according to any one of claims 1 to 7, characterized in that a resin composition melt viscosity 50~200Pa · s at a shear rate of 1000 s ^-1 Cradle guide for displacement axial piston pumps. A variable displacement axial piston pump comprising the cradle guide according to any one of claims 1 to 8 .

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