Method for self-compensation structure of cam-lobe hydraulic motor plate distribution system

Abstract

Provided is a design method for a self-compensation structure of a cam-lobe hydraulic motor plate distribution system, which comprises that follow steps: firstly, establishing a force balance equation, a pressure distribution equation and a flow balance equation for each balance chamber, setting a boundary condition, and setting an expected nominal clearance; selecting a fit clearance for simultaneous solutions, and obtaining a set of solutions of areas; taking a maximum value in this set of solutions as the median, and setting a set of area values in the optimization design; further solving changing curves of the nominal clearance and the total leakage of the distribution system with the rotation angle of the cylinder block, and calculating the average value of various curves after the operation is smooth, and designing the self-compensation structure based on selection of the optimal combination of the fit clearance and area.

Claims

1. A hydraulic motor with a self-compensation structure, comprising a self-compensation structure and a distribution plate; wherein one side of the distribution plate is a distribution end face, and the other side of the distribution plate is provided with an oil inlet and an oil discharge port, the distribution end face of the distribution plate is pressed against a piston port end face of a cylinder block; the self-compensation structure is a cylindrical cover structure, a right end of the self-compensation structure is pressed against a fixed shell of the hydraulic motor to achieve sealing of a balance chamber and to maintain internal pressure of the balance chamber, the oil in a high-pressure distribution window and a low-pressure oil distribution window of the distribution plate periodically enters the balance chamber to provide a leftwards pressing force for the distribution plate, the pressing force reduces a fit clearance between the distribution end face of the distribution plate and the piston port end face of the cylinder block, ensuring a sealing between the distribution plate and the cylinder block, the distribution plate moves along the self-compensation structure according to the force difference between left and right sides of the distribution plate to automatically adjust the distance between the distribution end face of the distribution plate and the piston port end face of the cylinder block, realizing the automatic compensation.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a flow chart of a design method for a self-compensation structure.

(2) FIG. 2 is a structural principle and stress diagram of a self-compensation distribution system.

(3) FIG. 3 is a schematic diagram of a distribution end face.

(4) FIG. 4 is a schematic diagram of a piston port end face.

(5) FIG. 5 is a schematic diagram of the oil film pressure distribution at the distribution end face and fit clearance.

(6) FIG. 6 is a changing curve of a nominal clearance h.sub.0 with the rotation angle of a motor when the fit clearance is 5 microns and the diameter d is 16 mm.

(7) FIG. 7 is a changing curve of a total leakage Q.sub.3 with the rotation angle of a motor when the fit clearance is 5 microns and the diameter d is 16 mm.

(8) FIG. 8 is a changing curve of an average nominal clearance h.sub.0 with the fit clearance c when the diameter is D.sub.1.

(9) FIG. 9 is a changing curve of an average total leakage Q.sub.3 with the fit clearance c when the diameter is D.sub.1.

(10) The reference signs in the attached drawings: 1Cylinder block, 2Piston chamber oil port, 3Self-compensation structure, 4Distribution plate, 5Shell, 6Floating sealing sleeve, 7Low pressure oil distribution window, 8Balance chamber, 9High pressure oil distribution window and 10Spring.

DESCRIPTION OF EMBODIMENTS

(11) In order to explain the embodiment of the present application more clearly, the present application will be further explained with the attached drawings and specific embodiments.

(12) As shown in FIG. 1, the present application provides a design method for a self-compensation structure of a cam-lobe hydraulic motor plate distribution system, which reduces the leakage and wear of the distribution system by optimizing the projected area of the self-compensation structure on the distribution end face and the fit clearance between the self-compensation structure and the distribution plate. In the distribution system, one side of the distribution plate is the distribution end face, and the back side is an oil inlet and an oil discharge port of the distribution plate. With the changes of the oil pressure, the rotation speed and wear during the rotation of the motor, the distribution plate moves along the self-compensation structure, and the distance between the distribution end face of the distribution plate and the piston port end face of the cylinder block is automatically adjusted to realize automatic compensation. The oil in the high-pressure oil distribution window and the low-pressure oil distribution window of the distribution plate will periodically enter the balance chambers of the self-compensation structure to provide a pressing force for the distribution plate; and the pressing force reduces the fit clearance between the distribution end face of the distribution plate and the piston port end face of the cylinder block, thus ensuring the sealing between the distribution plate and the cylinder block.

(13) The specific design step of the present application are as follows:

(14) Taking a self-compensation distribution system of an eight-acting fourteen-piston hydraulic motor as an example, as shown in FIG. 2, the partial sectional view of the distribution system consists of a distribution plate 4, a self-compensation structure 3, a spring 10 and a floating sealing sleeve 6; the complete distribution end face 12 of the distribution plate 4 is shown in FIG. 3, and the distribution end face 12 is pressed against the piston port end face 13 of the cylinder block 1, which is shown in FIG. 4.

(15) The self-compensation structure 3 is a cylindrical cover structure, which realizes the sealing of the balance chamber 8, maintains the internal pressure of the balance chamber 8, and provides the leftwards pressing force F.sub.ci for the distribution plate 4; the right end of the self-compensation structure 3 is pressed against the fixed shell 11 of the motor, and the distribution plate 4 can move along the self-compensation structure 3 according to the force difference between the left and right sides to realize the self-compensation function; since the self-compensation structure 3 is cylindrical, its projected area S on the distribution end face of the distribution plate can be represented by a diameter D, and thus the two key dimensions of the self-compensation structure 3 are its outer cylindrical diameter D and the fit clearance c between the self-compensation structure 3 and the distribution plate 4, both of which will affect the leftward pressing force and leakage of the distribution plate; The excircle diameter D and the fit clearance c are the parameters to be optimized for the self-compensation structure of this embodiment.

(16) Step 1: a mechanical analysis is carried out for the distribution plate; as shown in FIG. 2, the distribution plate 4 is subjected to an oil film force F.sub.film, a hydraulic pressure F.sub.p of the piston chamber oil port 2, a hydraulic pressure F.sub.h on the transition inclined plane of eight high-pressure oil distribution windows 9, a hydraulic pressure F.sub.1 on the transition inclined plane of eight low-pressure oil distribution windows 7, a hydraulic pressure F.sub.ci of sixteen balance chambers 8, an elastic force F.sub.k of sixteen springs 10, a pressing force F.sub.in of the floating sealing sleeve 6 at eight high-pressure oil inlets, a pressing force F.sub.out of the floating sealing sleeve 6 at eight low-pressure oil outlets, and an acting force F.sub.x of the internal pressure of the motor shell on the distribution plate 4; a force balance equation of the distribution plate is established, and the resultant force F is 0:

(17) $.Math.F=F_{\mathrm{film}}+F_p+F_h+F_1+F_x-F_{\mathrm{ci}}-F_k-F_{\mathrm{in}}-F_{\mathrm{out}}=0$

(18) The oil film force F.sub.film in step 1 is obtained by integrating the oil film pressure p distributed on the distribution end face; the hydraulic pressure F.sub.p is the total acting force generated by the oil of fourteen piston chamber oil ports 2 on the distribution end face 12, and the acting force of each piston chamber oil port 2 is calculated by multiplying the pressure p.sub.p of the piston chamber with the overlapping area S.sub.p; the overlapping area S.sub.p is the area of the overlapping area between the piston chamber oil port 2 and the distribution end face 12; the hydraulic pressure F.sub.ci is the product of the pressure p.sub.ci in the balance chamber 8 and the projected area S of the self-compensation structure 3 on the distribution end face 12; for this embodiment, the projected area S is calculated from the diameter D of the self-compensation structure 3.

(19) Step 2: an oil film pressure distribution equation (a lubrication model) on the distribution plate end face 12 is established to calculate the supporting force between the distribution plate end face and the piston port end face of the cylinder block and the leakage of the distribution pair, and the supporting force separates the distribution plate from the cylinder block;

(20) $\frac{p}{x}\left(\frac{h^3}{12}\frac{p}{x}\right)+\frac{p}{y}\left(\frac{h^3}{12}\frac{p}{y}\right)=\frac{1}{2}\frac{\mathrm{uh}}{x}+\frac{1}{2}\frac{\mathrm{vh}}{y}+\frac{h}{t}$

(21) where p represents the oil film pressure at a certain point on the distribution end face 12, and x represents the horizontal coordinate of each point on the distribution end face 12; as shown in FIG. 3, y represents the vertical coordinate of each point on the distribution end face 12, is the oil density at each point on the distribution end face, t is the time, is the oil viscosity, h is the oil film thickness at a certain point of the friction pair, u is the speed of a certain point on the piston port end face 13 relative to the x axis, and v is the velocity of a point on the piston port end face 13 relative to the y axis.

(22) The thickness of the oil film is calculated by the following equation:

(23) $h=h_0+h$

(24) where h.sub.0 is the nominal clearance between the distribution end face 12 and the piston port end face 13, and h is the deformation caused by pressure at a certain point between the distribution end face 12 and the piston port end face 13.

(25) Step 3: a flow balance equation is established for the balance chamber where the self-compensation structure is located, and the pressure p.sub.ci in the balance chamber 8 in a transitional state is calculated, wherein the net flow Q of the balance chamber 8 is 0:

(26) $.Math.Q=Q_1-Q_2-V_0\left(p_{\mathrm{ci}}-p_{\mathrm{ci}0}\right)/K_{\mathrm{oil}}$

(27) As shown in FIG. 2, in the formula, Q is the net flow of the balance chamber, Q.sub.1 is the flow flowing into the balance chamber 8 from the distribution end face, Q.sub.2 is the flow of the balance chamber 8 leaking from the fit clearance c, V.sub.0 is the volume of the balance chamber 8, p.sub.ci0 is the pressure of the balance chamber 8 at a previous moment, and K.sub.oil is the volume elastic modulus of the oil; the transitional state of the balance chamber 8 is the state when the balance chamber 8 is not communicated with the piston chamber oil port 2, at which time, the pressure p.sub.ci of the balance chamber is unknown and changes with time, which needs to be calculated according to the above flow balance equation; when the balance chamber 8 is communicated with the piston chamber oil port 2, the pressure p.sub.ci of the balance chamber is equal to the pressure of the communicated piston chamber oil port, which is a known quantity and does not need to be calculated by the flow balance equation.

(28) Step 4: a boundary condition for solving the pressure distribution equation in step 2 is set by combining the flow balance equations in step 3; the boundary condition is as follows: the pressure on the boundary connected with the high-pressure distribution window 9 is set as the oil inlet pressure p.sub.H of the motor, the pressure on the boundary connected with the low-pressure distribution window 7 is set as the oil discharge pressure p.sub.L of the motor, the pressure on the boundary connected with the internal chamber of the motor is set as the oil discharge pressure p.sub.x of the motor, and the pressure on the boundary connected with the balance chamber 8 is set as p.sub.ci.

(29) Step 5: the desired nominal clearance h.sub.0 on the distribution end face 12 is determined according to the surface roughness of the distribution end face 12 and the piston port end face 13; in this embodiment, h.sub.0 is 2{square root over (f.sub.1.sup.2+f.sub.2.sup.2)}, where f.sub.1 and f.sub.2 are the surface roughness of the distribution end face 12 and the piston port end face 13 respectively.

(30) Step 6: the set of values of the fit clearance c is set as C={2, 2.5, 3, 3.5, . . . , 21.5, 22} microns, and in this step, the fit clearance c=2 microns is selected; the equations in steps 2 and 3 are solved by combining the h.sub.0 determined in step 5 and the boundary condition in step 4 to obtain a set S of solutions of the area S when the cylinder block rotates at different angles relative to the distribution plate; the maximum value S.sub.max in S is set as the median of a value range of the area S in the optimization design; and the values of the area S before and after the median are designed according to actual requirements, that is, the set of values of the area S is SS={S.sub.1, S.sub.2, S.sub.3, . . . , S.sub.m, S.sub.max, S.sub.m+2, . . . , S.sub.2m+1}, where S.sub.1 . . . S.sub.2m+1 gradually increases; in this embodiment, the oil film pressure c and the balance chamber pressure p.sub.ci when the cylinder block 1 rotates at different angles relative to the distribution plate 4 are obtained, and the result when the cylinder block 1 rotates at 270 degrees relative to the distribution plate 4 is shown in FIG. 5, in which the denser the lines, the greater the pressure; based on the oil film pressure v and the balance chamber pressure p.sub.ci at different angles, the force balance equation in step 1 is solved; and a set D of solutions for the diameter D at different angles is obtained, the maximum value in D is D.sub.t=16 mm, and the set of values of the diameter D for optimization is set as DD={9, 10, 11, . . . , 16, 21, 22, 23} mm.

(31) Step 7: the values of 41 fit clearances c in the set C are combined with the values of 15 diameters D in the DD set in pairs, and the equations in step 2 and step 3 are solved in combination with the boundary condition in step 4, so as to simulate the changes of the oil film pressure p and balance chamber pressure p.sub.ci on the distribution plate 12 when the cylinder block 1 rotates at different angles relative to the distribution plate 4; the calculation result for each angle should ensure that the force balance equation in step 1 is established; after post-processing the simulation results, the change curves of the nominal clearance h.sub.0 and the leakage Q.sub.3 of the distribution plate end face 12 when the cylinder block 1 rotates at different angles relative to the distribution plate 4 for 4115 combinations of the fit clearances c and diameters D are obtained, where the changing curves of the nominal clearance h.sub.0 and the leakage Q.sub.3 for the combination of c=5 and D=16 are shown in FIGS. 6 and 7 respectively; the leakage Q.sub.3 is the sum of the leakage of the distribution system, including the leakage flow Q.sub.0 of the distribution end face 12 and the leakage flow Q.sub.2 of the self-compensation structure 3.

(32) Step 8: an average value of the curves obtained in step 7 after the distribution plate 4 works smoothly is obtained, and an average value of the data in the range of 175-270 degrees is taken for the data in FIG. 6 and FIG. 7 to obtain the changing curves of the average nominal clearance h.sub.0 and the average leakage Q.sub.3 with the fit clearance c and the diameter D; when the diameter D=16 mm, the changing curves of the average nominal clearance h.sub.0 and the average leakage Q.sub.3 with the fit clearance c are shown in FIGS. 8 and 9; a combination of the fit clearance c=5 microns and D=16 mm that has a minimum average leakage is selected as the final optimization result under a condition that h.sub.0 is ensured to be greater than 2{square root over (f.sub.1.sup.2+f.sub.2.sup.2)}, and the design of the self-compensation structure is completed according to the final optimization result.

(33) The above-mentioned examples are only used to describe the preferred embodiments of the present application, and do not limit the scope of the present application. Under the premise of not departing from the design spirit of the present application, various modifications and improvements made by ordinary technicians in the field to the technical solution of the present application shall fall within the protection scope determined by the claims of the present application.