A design method of additional angle of swash plate of constant pressure variable plunger pump

Abstract

This invention discloses a method for designing the additional angle of the swashplate in a constant pressure variable displacement piston pump, comprising the following steps: A. When the additional angle β is 0, based on the inlet pressure P of the variable displacement pump... 始 Constant pressure P 终 Given the maximum swashplate angle α, determine the compression angle B. Based on equations 1 and 2), calculate the corresponding additional angle β at the maximum swashplate angle α. Then, using equation 3), calculate the angle C between the z-axis and the low-pressure zone oil window of the distributor plate. Calculate the curves showing the volume ratio changing with the additional angle β at different swashplate angles α. The intersection of these curves represents the optimal design value for the additional angle β under different operating conditions. This invention enables the variable pump to minimize pressure pulsation under any operating condition, thereby improving the performance of the constant pressure variable piston pump and the reliability and lifespan of the onboard hydraulic system.

Description

Technical Field

[0001] This invention relates to a swashplate for a constant pressure variable displacement piston pump, and more particularly to a method for designing an additional angle for the swashplate of a constant pressure variable displacement piston pump. Background Technology

[0002] With the development of science and technology, high-speed and heavy-duty operation is an inevitable trend in the development of aviation hydraulic pumps. However, the increase in pump speed, flow rate, and pressure inevitably leads to an increase in outlet pressure pulsation. For aviation hydraulic pumps, high-frequency pressure pulsation may cause fluid-structure interaction vibration in the hydraulic pipeline system, leading to pipeline system failure or damage, and in severe cases, even safety accidents. Therefore, the magnitude of outlet pressure pulsation is one of the key performance indicators for evaluating the functional performance of a hydraulic pump. According to aircraft hydraulic specifications, the outlet pressure pulsation index for aviation hydraulic pumps is ±10% of the rated pressure, and new-generation aircraft can reach ±5%, while foreign civil aircraft pressure pulsation can even reach below ±2.5%.

[0003] Constant pressure variable displacement piston pumps are used as the main pumps in aircraft hydraulic systems due to their compact structure, high power density, low noise, and good dynamic characteristics. The root cause of pressure pulsation is the flow pulsation in the piston chamber, and the main factor affecting the magnitude of this pulsation is the structural dimensions of the distributor plate's oil window. However, the required flow rate of the aircraft hydraulic system varies under different operating conditions, resulting in different displacements for the variable displacement pump. A specific distributor plate structure can only optimize the flow pulsation at a certain operating point, and cannot achieve optimal flow pulsation design for all operating conditions. This leads to increased pressure pulsation amplitude under certain conditions, resulting in increased system pipeline vibration amplitude and ultimately reducing the reliability of the airborne hydraulic system. Therefore, there is an urgent need to develop a design method for the swashplate additional angle of a constant pressure variable displacement piston pump to minimize pressure pulsation under any operating condition. Summary of the Invention

[0004] The purpose of this invention is to provide a design method for the additional angle of the swashplate in a constant-pressure variable displacement piston pump. This invention enables the variable displacement pump to minimize pressure pulsation under any operating condition, thereby improving the functional performance of the constant-pressure variable displacement piston pump and the reliability and lifespan of the onboard hydraulic system.

[0005] The technical solution of this invention: A method for designing the additional angle of the swashplate in a constant pressure variable displacement piston pump, comprising the following steps:

[0006] A. When the additional angle β is 0, according to the inlet pressure P of the variable pump 始 Constant pressure P 终 Determine the compression angle based on the maximum swing angle α of the swashplate.

[0007] B. Based on equations 1) and 2), calculate the corresponding additional angle β below the maximum swashplate angle α. Then, calculate the angle between the z-axis and the oil window in the low-pressure zone of the distribution plate using equation 3). fixed

[0008] Equation 1) is The angle between the oil window in the low-pressure zone of the distribution plate and the z-axis is... The angle between the projection of the plunger cavity's oblong orifice onto the distribution plate is θ0, and the angle between the oil window in the high-pressure zone of the distribution plate and the z-axis is...

[0009] Equation 2) is Where γ is the deflection angle at the top and bottom dead points;

[0010] Equation 3) is θ0 is the angle between the projection of the waist-shaped orifice of the plunger cavity onto the distribution plate;

[0011] C. Calculate the curves of volume ratio as a function of additional angle β under different swashplate angles α. The intersection of different curves is the optimal design value of additional angle β under different working conditions.

[0012] In the aforementioned design method for the additional angle of the swashplate of a constant pressure variable displacement piston pump, the compression angle in step A... The specific calculation method is as follows: When β = 0, the total volume of the plunger cavity after sucking up the oil is V. 始 The pressure is P 始 The compressed volume is V. 终 The pressure is P 终 The compression angle is Then there is Then through The inverse solution can realize the pressure from P 始 Increase to V 终 of In the formula, d p Let be the plunger diameter, E be the elastic modulus of the oil, V be the initial volume of the oil in the plunger cavity, ΔV be the volume change of the oil in the plunger cavity, and r be the radius of the plunger distribution circle.

[0013] In the aforementioned design method for the additional angle of the swashplate of a constant pressure variable displacement piston pump, step C, specifically the method for solving the curve of the volume ratio changing with the additional angle β under the swashplate swing angle α, is as follows:

[0014] Formula for calculating the pressure change amplitude in the transition zone of the plunger cavity Integrating, we get:

[0015] Among them, V 始 =V0-x 始 A p V 终 =V0-x 终 Ap Ap is the cross-sectional area of ​​the plunger.

[0016] Compared with existing technologies, this invention is based on fluid mechanics and the working principle of constant pressure variable displacement piston pumps. It establishes a mathematical relationship for the flow pulsation of variable displacement pumps and adopts a unique design method for the additional angle of the swashplate of constant pressure variable displacement piston pumps. This scientifically guides the design of the additional angle of the swashplate of constant pressure variable displacement piston pumps, so that the outlet pressure pulsation of the variable displacement pump is minimized under any working condition. This improves the functional performance of constant pressure variable displacement piston pumps and the reliability and lifespan of the onboard hydraulic system.

[0017] In summary, this invention enables the variable pump to minimize pressure pulsation under any operating condition, thereby improving the functional performance of the constant pressure variable piston pump and the reliability and lifespan of the onboard hydraulic system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of swashplate motion;

[0019] Figure 2 This is a schematic diagram of the movement trajectory of the sliding track-plunger assembly and the structure of the oil distributor plate;

[0020] Figure 3 This is a schematic diagram of the optimal additional angle design for a certain type of variable pump.

[0021] The markings in the attached diagram are: 1-swashplate; 2-slipper; 3-plunger; 4-yaw shaft; 5-swashplate rotation axis. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0023] Example. A method for designing the additional angle of the swashplate in a constant pressure variable displacement piston pump, such as... Figure 1 As shown, the plane corresponding to the swashplate plane and rotating along the swashplate axis 5 is defined as the swashplate reference plane. The inner shaft axis is taken as the x-axis, the direction from the inner shaft extension to the tail end is the positive x-axis, and the swashplate rotation axis is taken as the y-axis. The z-axis direction is determined according to the right-hand rule, establishing a basic coordinate system. The angle of rotation around the y-axis is the variable pump's swing angle α, and the angle of rotation around the z-axis is the additional angle β. When the constant-pressure variable pump is working, according to the changes in the hydraulic system's flow demand, the variable mechanism drives the swashplate to rotate around the y-axis, causing the swing angle α to change accordingly, thereby controlling the output flow rate of the variable pump. The additional angle β, as a structural dimension of the swashplate, remains unchanged. Simultaneously, this additional angle causes the upper and lower dead points of the sliding shoe-piston assembly to shift to the deflection axis 4, thus altering the flow field characteristics of the aviation hydraulic pump.

[0024] like Figure 2 As shown, θn is the rotation angle of the nth plunger, and r is the radius of the plunger distribution circle. The equations of motion for the plunger ball head in each direction are:

[0025]

[0026] The deflection angles γ of the upper and lower dead points of the sliding shoe-plunger assembly are:

[0027]

[0028] Assume the angle between the oil window in the low-pressure zone of the distributor plate and the z-axis is... The angle between the z-axis and the oil window in the high-pressure zone of the distributor plate is The angle between the projection of the plunger cavity's oblong orifice onto the distribution plate is θ0, and the angle between the oil window in the high-pressure zone of the distribution plate and the z-axis is... The angle between the z-axis and the oil window in the low-pressure zone of the distributor plate is To improve the volumetric efficiency of a constant-pressure variable displacement piston pump under high-flow conditions, it is necessary to ensure that:

[0029]

[0030] At this point, the plunger cavity rotates at the angle before communicating with the high-pressure zone oil window of the distribution plate. (i.e., the compression angle) is:

[0031]

[0032] The initial rotation angle of the plunger in the x-axis direction is: The angle when communicating with the oil window in the high-pressure zone of the distribution plate is

[0033] At this moment, the plunger's position in the x-axis direction is:

[0034]

[0035]

[0036] According to the fluid dynamics equations, the pressure change amplitude of the plunger cavity in the transition zone (i.e., the region that is not connected to either the high or low pressure oil windows of the distribution plate) is:

[0037]

[0038] In the formula, E is the elastic modulus of the oil, V is the initial volume of the oil in the plunger cavity, and ΔV is the volume change of the oil in the plunger cavity.

[0039] Integrating the above equation, we get:

[0040]

[0041] The volume change of the oil in the plunger cavity during the transition zone can be derived from the plunger's motion equation. The volume of the plunger cavity at its initial position is:

[0042] V 始 =V0-x 始 A p (9)

[0043] The volume of the plunger cavity when communicating with the oil window in the high-pressure zone of the distribution plate is:

[0044] V 终 =V0-x 终 A p (10)

[0045] In the formula, V0 is the volume of the plunger cavity when the swashplate angle α is zero. Ap is the cross-sectional area of ​​the plunger.

[0046] When the temperature is constant, the elastic modulus E of the oil is a function of the pressure. For a constant pressure variable piston pump, P_initial is the inlet pressure of the variable pump and P_final is the constant pressure of the variable pump. Then, the left side of equation (8) is a constant. In order to make the pressure increase effect of the piston cavity in the variable process the same, it can be achieved by adjusting the ratio of the initial piston cavity volume V_initial to the final piston cavity volume V_final at the end of the pressure increase. The adjustment of this volume ratio can be achieved by adjusting the additional angle β.

[0047] In summary, the design method for the additional angle β of the swashplate in a constant-pressure variable displacement piston pump is as follows:

[0048] First, when the additional angle β is 0, according to the inlet pressure P of the variable pump... 始 Constant pressure P 终 The maximum swing angle α of the swashplate determines the compression angle. Compression angle in step A The specific calculation method is as follows: When β = 0, the total volume of the plunger cavity after sucking up the oil is V. 始 The pressure is P 始 The compressed volume is V. 终 The pressure is P 终 The compression angle is Then there is Then through The inverse solution can realize the pressure from P 始 Increase to V 终 of In the formula, d p Let be the plunger diameter, E be the elastic modulus of the oil, V be the initial volume of the oil in the plunger cavity, ΔV be the volume change of the oil in the plunger cavity, and r be the radius of the plunger distribution circle.

[0049] Secondly, based on equations (2) and (3), the corresponding additional angle β under the maximum swashplate angle α is calculated. φ4 can be calculated using equation (4), and is fixed.

[0050] Finally, the curves of volume ratio versus additional angle β under different swashplate angles α are obtained, and their intersection points are the optimal design values ​​of additional angle β under different working conditions.

[0051] As shown in Table 1, taking the design of the additional swashplate angle of a certain type of constant pressure variable displacement piston pump as an example, its main technical parameters are as follows:

[0052] Table 1 Main Technical Parameters of a Certain Type of Constant Pressure Variable Variable Plunger Pump

[0053]

[0054] Based on the above design method, the curves showing the rate of volume change versus the additional angle β under different swashplate angles α are attached. Figure 3 As shown, the value at the intersection point, 3°7′~3°15′, is the optimal additional angle design value for the variable pump, which minimizes the backflow of the plunger cavity flow under any swing angle of the swashplate, that is, minimizes the pressure pulsation amplitude under all operating conditions.

Claims

1. A method for designing the additional angle of the swashplate in a constant-pressure variable displacement piston pump, characterized in that, Includes the following steps: A. When the additional angle β is 0, according to the inlet pressure P of the variable pump 始 Constant pressure P 终 Determine the compression angle based on the maximum swing angle α of the swashplate. B. Based on equations 1) and 2), calculate the corresponding additional angle β below the maximum swashplate angle α. Then, calculate the angle between the z-axis and the oil window in the low-pressure zone of the distribution plate using equation 3). fixed Equation 1) is The angle between the oil window in the low-pressure zone of the distribution plate and the z-axis is... The angle between the projection of the plunger cavity's oblong orifice onto the distribution plate is θ0, and the angle between the oil window in the high-pressure zone of the distribution plate and the z-axis is... Equation 2) is Where γ is the deflection angle at the top and bottom dead points; Equation 3) is θ0 is the angle between the projection of the waist-shaped orifice of the plunger cavity onto the distribution plate; C. Calculate the curves of volume ratio as a function of additional angle β under different swashplate angles α. The intersection of different curves is the optimal design value of additional angle β under different working conditions.

2. The method for designing the additional angle of the swashplate in a constant pressure variable displacement piston pump according to claim 1, characterized in that, Compression angle in step A The specific calculation method is as follows: When β = 0, the total volume of the plunger cavity after sucking up the oil is V. 始 The pressure is P 始 The compressed volume is V. 终 The pressure is P 终 The compression angle is Then there is Then through The inverse solution can realize the pressure from P 始 Increase to V 终 of In the formula, d p Let be the plunger diameter, E be the elastic modulus of the oil, V be the initial volume of the oil in the plunger cavity, ΔV be the volume change of the oil in the plunger cavity, and r be the radius of the plunger distribution circle.

3. The method for designing the additional angle of the swashplate in a constant pressure variable displacement piston pump according to claim 2, characterized in that, In step C, the specific method for solving the curve of the volume ratio as a function of the additional angle β under the swashplate angle α is as follows: Formula for calculating the pressure change amplitude in the transition zone of the plunger cavity Integrating, we get: Among them, V 始 =V0-x 始 A p V 终 =V0-x 终 A p Ap is the cross-sectional area of ​​the plunger.

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