Created on:2021-04-20 08:50

Manufacturing technology of multi action radial piston motor

Manufacturing technology of multi action radial piston motor

The radial ball plug low speed high torque hydraulic motor (QJM hydraulic motor) is introduced as an example.

(1) The structure and technical requirements are shown in Figure R. the ball plug pair composed of several steel balls 1 and ball bracket 5 is evenly installed on the rotor 2 of QJM hydraulic motor, and the force is transmitted through the ball bracket. The valve distribution mechanism of the motor is valve distribution shaft 4.

R.jpg

Compared with other types of hydraulic motors, this type of motor has the characteristics of compact structure, light weight, small volume, good stability at low speed and high efficiency. The rated working pressure is 20MPa and the peak working pressure can reach 31mpa 5 MPa. Therefore, the parts must have the conditions of high strength, wear resistance and tight matching, which brings some difficulties to the processing.

The material and technology of the stator, rotor and distribution shaft directly affect the performance and life of the motor.

(2) Material and process requirements of key parts

① The stator is as shown in Figure S. when the hydraulic motor is working, the high-pressure oil enters into the oil chamber at the lower end of the steel ball through the valve distribution shaft, and the pressure oil forms the hydraulic pressure P, which pushes the steel ball upward to make it contact with the curve of the Neiyi line body. At the contact point, the component force PE formed by the P force presses the inner curve stator, which gives the steel ball a positive pressure PC of equal size and opposite direction. The force acting on the steel ball can be divided into radial component force N and tangential component force t, in which the radial component force n is in balance with the hydraulic pressure P, and the tangential component force t acts on the tangent direction of rotor 4 through the steel ball, forcing rotor 4 to rotate in the counterclockwise direction, and rotor 4 will rotate It is directly connected with the drive shaft, so the drive shaft rotates. It can be seen that the tangential component t depends on the shape of the inner curve. Because the contact stress between the steel ball and the stator is much greater than that between the general roller or beam and the stator, the stator is required not only to have accurate inner curve shape, but also to have high hardness, high wear resistance and fatigue resistance.

According to the above requirements, the material of stator is bearing steel GCr15SiMn, which is required to be spheroidized annealed for more than 2 grades, and the overall quenching hardness is 60-63hrc.

The inner curve is traditionally processed by cam profiling, but in order to ensure the smooth transition of the inner curve, the advanced inner curve machining center is recommended.

The machining process of stator is as follows: blanking → die forging → spheroidizing annealing level 1 ~ 2 → rough and finish turning inner stop and two planes, leaving grinding allowance of 0.4 ~ 0.6mm → drilling → milling curved surface, leaving grinding allowance of 0.4 ~ 0.6mm → deburring → overall quenching (60 ~ 63hrc) The deformation shall not be greater than 0.3mm, the two planes shall be ground to meet the requirements of the drawing, the two ends shall be ground to meet the requirements of the drawing, the inner curved surface shall be ground to meet the requirements of the drawing, the inner curved raceway shall meet the requirements of the drawing, the flaw detection and demagnetization bucket shall be cleaned, and the inspection shall be conducted.

② The main function of the rotor is to transmit torque, but it is also the concentrated place of all friction pairs in this type of hydraulic motor. It forms a rotating friction pair with the port shaft and a reciprocating friction pair with the ball bracket. Therefore, the rotor should have enough strength and high wear resistance.

According to the above requirements, the rotor is made of nodular cast iron QT600, and the normalized hardness is 230-260hb after heat treatment.

In addition, the clearance between the rotor and the distribution shaft and piston directly affects the internal leakage and volumetric efficiency of the hydraulic motor, which requires high machining accuracy.

The machining process of the rotor is as follows: Casting → annealing to eliminate internal stress → rough turning, allowance of 2 ~ 3mm → rough boring, allowance of 3 ~ 4mm → normalizing (230 ~ 260hb) Finish turning inner hole and small end, leaving grinding allowance of 0.3-0.4mm → drilling Φ 10mm process positioning hole → boring, leaving fine reaming allowance of 0.01-0.03mm → reaming → deburring inner piston hole after reaming → inserting rectangular spline of inner hole → grinding outer circle of small end → grinding inner port hole → deburring inner hole → cleaning and inspection.

③ Distribution shaft has three functions in this type of hydraulic motor: one is distribution; the other is connection of oil circuit; the third is radial support of rotor. The machining accuracy of its flow distribution angle directly affects the total efficiency, impact and noise of the hydraulic motor; as an external connection, it must have enough rigidity; as a support, it directly forms a rotating friction pair with the rotor, which needs high wear resistance.

Considering all factors, the material of valve plate is ductile cast iron QT600, the normalized hardness of heat treatment is 230-260hb, the cylindricity of the cylindrical surface matched with the rotor is not more than 0.005mm, the surface roughness is ≤ 0.8 μ m, and the Graduation Error of valve plate angle is ± 10 '.

The processing process of valve distribution shaft is: Casting → annealing to eliminate internal stress → rough turning, 2 ~ 3mm allowance → normalizing (230 ~ 260hb) Finish turning inner hole and outer circle with grinding allowance of 0.3-0.4mm → drilling and bottom hole of oil outlet → turning screw hole of oil inlet and outlet → connecting eccentric groove of inner hole with oil outlet → milling distribution groove to meet design requirements → deburring inner hole groove and distribution groove, but no chamfering is allowed → grinding inner hole to meet design requirements → deburring inner hole after grinding → grinding outer circle according to drawing requirements, matching clearance → Generally 0.015-0.03mm → deburring after cylindrical grinding → cleaning and drying → inspection.

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