Plastic spacer bush of engine rocker shaft and manufacturing method thereof
阅读说明：本技术 发动机摇臂轴塑料隔套及其制造方法 (Plastic spacer bush of engine rocker shaft and manufacturing method thereof ) 是由 刘伟 杨丹 李鲲 马华跃 徐亚东 于 2019-09-24 设计创作，主要内容包括：发动机摇臂轴塑料隔套,为圆管状结构,塑料隔套由玻纤增强的热塑性材料PA6T经注塑成型、热处理和机加工等工序制造而成,经本发明方法所制成的塑料隔套在发动机冷热工况下,其轴向长度和内径尺寸精度的稳定性很好,可完全替代钢制隔套,且相比传统钢制隔套具有价格低、重量小、刚度好的优势。(The plastic spacer bush of the rocker arm shaft of the engine is of a circular tubular structure, is manufactured by the procedures of injection molding, heat treatment, machining and the like of a glass fiber reinforced thermoplastic material PA6T, has good stability of dimensional accuracy of axial length and inner diameter under the working conditions of cold and heat of the engine, can completely replace a steel spacer bush, and has the advantages of low price, light weight and good rigidity compared with the traditional steel spacer bush.)
1. The engine rocker shaft plastic spacer bush is of a circular tubular structure; the method is characterized in that: the spacer bush is manufactured by the steps of injection molding, heat treatment, machining and the like of glass fiber reinforced thermoplastic material PA 6T.
2. The engine rocker shaft spacer of claim 1, wherein: an axially-through opening is formed in the side wall of the spacer bush, the cross section of the spacer bush is C-shaped, and the angle of the opening is 60-120 degrees; or a plurality of axial strip-shaped lightening holes are equally distributed on the side wall of the spacer bush along the circumferential surface.
3. The engine rocker shaft plastic spacer of claim 1 or 2, wherein: the raw material of the spacer can be replaced by thermoplastic materials PA4T, PA9T, PA10T, PPS, PEEK, PI, LCP and PSU.
4. A method of manufacturing a plastic spacer as claimed in claim 1 or 2, comprising the steps of:
a. preparing a raw material, namely preparing a glass fiber reinforced thermoplastic material PA6T with the density of 1.40-1.80, the linear expansion coefficient of the material in the flowing direction of less than or equal to 3 multiplied by 10 < -5 > and the linear expansion coefficient of the material in the vertical flowing direction of less than or equal to 8 multiplied by 10 < -5 >;
b. injection molding, wherein a gate of an adopted mold is positioned right ahead one annular end face of the spacer bush, and during injection molding, PA6T melt flows from one end of the spacer bush to the other end along the axial direction through the gate;
c. heat treatment, placing the injection molded spacer bush in hot air at 150-240 ℃ for standing treatment for 2-16 hours, and then naturally cooling;
d. and (4) machining, namely performing micro turning and grinding machining on the end surfaces and the inner holes on the two sides of the spacer bush by adopting a conventional plastic part machining mode.
5. The manufacturing method according to claim 4, characterized in that: in the step a, the thermoplastic material adopted is a glass fiber reinforced thermoplastic resin PA6T with the density of 1.65, the linear expansion coefficient of the material in the flowing direction of 1.3 multiplied by 10-5 and the vertical flowing direction of 4.2 multiplied by 10-5.
6. The manufacturing method according to claim 4, characterized in that: in the step b, 3 gates are uniformly distributed right in front of the annular end face of the spacer sleeve along the circumference, and a circle formed by the 3 gates and the annular end face are coaxial.
7. The manufacturing method according to claim 4, characterized in that: in the step c, the temperature of the heat treatment is 210 +/-5 ℃, and the duration time is 2.5 +/-0.5 hours.
Technical Field
The invention relates to a spacer bush of a rocker arm shaft of a heavy diesel engine and a manufacturing method of the spacer bush, belonging to the technical field of spacer bushes of the rocker arm shaft of the engine.
Background
The commercial vehicle diesel engine air intake and exhaust integrated rocker arm shaft is sleeved with a spacer sleeve, the spacer sleeve and the rocker arm seat form a rotating friction pair, and the functions of positioning the air intake and exhaust rocker arms and preventing axial movement are achieved. Because the opening and closing actions of the air inlet valve and the exhaust valve are related, the size precision of the axial length and the inner diameter of the spacer sleeve is high, and the change of the axial length is small when the spacer sleeve expands with heat and contracts with cold. At present, a steel spacer bush is adopted by a rocker shaft spacer bush of an engine, and the weight of the steel spacer bush is large, so that the light weight of the engine is restricted.
Taking an integral air inlet rocker shaft spacer bush of a certain high-horsepower diesel engine as an example, the axial length tolerance of the spacer bush is 49 +/-0.05 mm, the inner diameter phi 31.08 mm-phi 31.18mm is required to endure an oil-moisture environment at the temperature of-40 ℃ to +150 ℃, the thermal expansion amount at the temperature of 25 ℃ to 150 ℃ is less than or equal to 0.10mm, and the abrasion loss of a reinforced rack spacer bush of the engine in 1000 hours is less than or equal to 0.06 mm.
At present, no case or report that a rocker arm shaft adopts a plastic spacer sleeve is found, and the reason is that: 1. the dimensional accuracy of common plastics (such as PA6 and PA66) and the dimensional stability under cold and hot environments are far from the difference of steel products, so that the common plastics cannot replace the steel products; 2. some advanced special plastics (such as PEEK and PI) are too expensive in material price, and have extremely low value in commercial application.
Chinese patent application "application number: 201811592842, name: the processing method of the crusher shaft sleeve provides a processing method of a crusher plastic shaft sleeve, and the shaft sleeve is a cylindrical mechanical part sleeved on a crusher rotating shaft and plays a role in adjusting the operation of equipment. The parts are formed by polymerization of caprolactam, heat treatment and machining, and are suitable for processing large shaft sleeves (commonly known as MC nylon sleeves and cast nylon sleeves), wherein the heat treatment is to carry out oil bath treatment on blank pieces of cast nylon, the oil temperature is kept at 175-180 ℃, then the blank pieces are slowly cooled, the heat treatment time is 15 minutes per 1mm thickness of oil bath, the preferential heat treatment also comprises the water bath treatment in 95 ℃ of water after the oil bath, and the heat treatment time is 15 minutes per 1mm thickness of water bath. However, such plastic sleeves have low rigidity, large linear thermal expansion and high price, and are not suitable for replacing steel rocker arm shaft spacers. The oil bath and water bath heat treatment process is mainly used for filling oil and water to the cast nylon parts, improving the water absorption of the cast nylon to achieve the purpose of stabilizing the geometric dimensions of the parts, and improving the mechanical properties and the lubricity of the parts. The process is not suitable for parts like an engine spacer bush with repeatedly alternated cold and heat, the evaporation of water and oil gas in the spacer bush is promoted by high temperature, the fluctuation of the inner diameter size is still overlarge, and the requirement of the performance of the engine spacer bush is not met.
Disclosure of Invention
The invention aims to provide a spacer bush made of plastic and a method for manufacturing the spacer bush, aiming at the defects of the prior art of the spacer bush of the rocker arm shaft of the diesel engine.
In order to achieve the purpose, the technical solution of the invention is as follows:
the engine rocker shaft plastic spacer bush is of a circular tubular structure; the spacer bush is manufactured by the steps of injection molding, heat treatment, machining and the like of glass fiber reinforced thermoplastic material PA 6T.
Preferably, the outer rings of the front end and the rear end of the spacer bush are respectively provided with an annular side flange, the side wall of the spacer bush is provided with an axially-penetrating opening, the cross section of the spacer bush is C-shaped at the moment, and the angle of the opening is 60-120 degrees; or a plurality of axial strip-shaped lightening holes are equally distributed on the side wall of the spacer bush along the circumferential surface.
Preferably, the raw material of the spacer is replaced by thermoplastic materials PA4T, PA9T, PA10T, PPS, PEEK, PI, LCP and PSU.
The method for manufacturing the plastic spacer comprises the following steps:
a. preparing a raw material, namely preparing a glass fiber reinforced thermoplastic material PA6T with the density of 1.40-1.80, the linear expansion coefficient of the material in the flowing direction of less than or equal to 3 multiplied by 10 < -5 > and the linear expansion coefficient of the material in the vertical flowing direction of less than or equal to 8 multiplied by 10 < -5 >;
b. injection molding, wherein a sprue of a mold is positioned right in front of one annular end face of the spacer bush, and during injection molding, PA6T melt flows from one end of the spacer bush to the other end along the axial direction through the sprue, so that the axial length expansion of the spacer bush can be minimized;
c. heat treatment, namely placing the injection-molded spacer bush in hot air at the temperature of 150-240 ℃ for standing treatment for 2-16 hours, so that the crystal form of the PA6T material is stable, and the residual stress in the product is eliminated; then naturally cooling to ensure that the spacer sleeve obtains an ideal size stabilizing effect;
d. and (4) machining, namely performing micro turning and grinding machining on the end surfaces and the inner holes on the two sides of the spacer bush by adopting a conventional plastic part machining mode.
Preferably, the thermoplastic material used in step a is a glass fiber reinforced thermoplastic resin PA6T having a density of 1.65, a coefficient of linear expansion of the material in the flow direction of 1.3X 10-5 and a coefficient of linear expansion of 4.2X 10-5 in the direction perpendicular to the flow direction.
Preferably, 3 gates are uniformly distributed right in front of the annular end face of the spacer sleeve along the circumference, and a circle formed by the 3 gates and the annular end face are coaxial.
Preferably, the temperature of the heat treatment in step c is 210 ℃. + -. 5 ℃ and the duration is 2.5 hours. + -. 0.5 hours.
Compared with the prior art, the invention has the beneficial effects that:
1. the plastic spacer bush has good stability of dimensional accuracy of axial length and inner diameter under the cold and hot working conditions of the engine, can completely replace a steel spacer bush, and has the advantages of low price, light weight and good rigidity compared with the traditional steel spacer bush.
2. The plastic spacer bush is provided with the axially-through opening on the side wall, so that the material is saved, the weight is reduced, and the assembly and the replacement of the spacer bush are facilitated.
3. The side wall of the plastic spacer bush is provided with the axial strip-shaped lightening hole, so that the material is further saved, and the weight is reduced.
Drawings
FIG. 1 is a schematic view of a first construction of a spacer according to the present invention;
FIG. 2 is a schematic view of a second construction of the spacer of the present invention;
FIG. 3 is a schematic view of a third construction of the spacer of the present invention.
In the figure: the
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
Referring to fig. 1 to 3, the engine rocker shaft plastic spacer bush is of a circular tubular structure; the spacer bush is manufactured by the steps of injection molding, heat treatment, machining and the like of glass fiber reinforced thermoplastic material PA 6T.
As a preferable technical scheme, an
As a preferable technical scheme, the outer rings of the front end and the rear end of the spacer bush are respectively provided with an
As a preferable technical scheme, the raw materials of the spacer can be replaced by thermoplastic materials PA4T, PA9T, PA10T, PPS, PEEK, PI, LCP and PSU.
The method for manufacturing the plastic spacer comprises the following steps:
a. preparing a raw material, namely preparing a glass fiber reinforced thermoplastic material PA6T with the density of 1.40-1.80, the linear expansion coefficient of the material in the flowing direction of less than or equal to 3 multiplied by 10 < -5 > and the linear expansion coefficient of the material in the vertical flowing direction of less than or equal to 8 multiplied by 10 < -5 >;
b. injection molding, wherein a gate of an adopted mold is positioned right ahead of one annular end face of the spacer sleeve, 3 gates are uniformly distributed right ahead of the annular end face of the spacer sleeve along the circumference, and a circle formed by the 3 gates and the annular end face are coaxial; thus, PA6T melt can flow from one side of the spacer to the other along the axis along the 3-point gate, which can minimize the axial length expansion of the spacer; the arrangement position of the pouring gate is the condition that the front end and the rear end of the spacer bush are not provided with the annular side flanges, and when the front end and the rear end of the spacer bush are provided with the annular side flanges, the pouring gate is specifically positioned at the position which is right in front of the annular end surface of the spacer bush and close to the inner hole wall of the spacer bush.
c. Heat treatment, namely placing the injection-molded spacer bush in hot air at the temperature of 150-240 ℃ for standing treatment for 2-16 hours, so that the crystal form of the PA6T material is stable, and the residual stress in the product is eliminated; then naturally cooling to ensure that the spacer sleeve obtains an ideal size stabilizing effect;
d. and (4) machining, namely performing micro turning and grinding machining on the end surfaces and the inner holes on the two sides of the spacer bush by adopting a conventional plastic part machining mode.
As a preferred technical proposal, the thermoplastic material adopted in the step a is a glass fiber reinforced thermoplastic resin PA6T with the density of 1.65, the linear expansion coefficient of the material in the flowing direction of 1.3 multiplied by 10-5 and the vertical flowing direction of 4.2 multiplied by 10-5.
As a preferred technical scheme, the temperature of the heat treatment in the step c is 210 +/-5 ℃, and the duration time is 2.5 hours +/-0.5 hour.
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