A transition zone biasing design method for increasing the limit speed of an asymmetric plunger pump

Abstract

The application discloses a transition zone biasing design method for improving the limit rotating speed of an asymmetric plunger pump, which comprises the following steps: firstly, determining the overall structure size and the asymmetric flow ratio; secondly, calculating the azimuth angle of the asymmetric transition zone based on the kinematic analysis of the plunger pump; thirdly, considering the limitation of the maximum oil suction speed of the valve plate window, judging whether the limit rotating speed of the asymmetric plunger pump can meet the design requirements; if yes, the design of the asymmetric plunger pump is completed; if not, the asymmetric transition zone needs to be subjected to biasing design. The transition zone biasing design method is convenient and fast, compact in design and wide in application range, and can significantly improve the limit rotating speed of the asymmetric plunger pump and broaden the application scenarios of the asymmetric plunger pump.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of axial piston pumps, and particularly relates to a transition zone biasing design method for improving the limit speed of an asymmetric piston pump. BACKGROUND

[0002] In a closed hydraulic system, auxiliary devices such as one-way valves are often added to the circuit to compensate for the asymmetric flow of the two chambers of the asymmetric cylinder to ensure the normal extension and retraction of the asymmetric cylinder, which not only increases the complexity of the circuit, but also inevitably causes energy loss of the system. The system configuration of the asymmetric piston pump controlling the asymmetric cylinder can effectively solve the problem of asymmetric flow of the pump controlling the asymmetric cylinder system by changing the flow ratio of the pump inlet and outlet to match the area ratio of the asymmetric cylinder. Compared with the traditional piston pump, the main difference in structure is the design of the asymmetric valve plate.

[0003] As shown in Figure 1 , when the asymmetric cylinder extends, the asymmetric piston pump supplies oil to the rodless chamber 5 through the flow distribution window A1, and the flow distribution windows B2 and C3 return oil from the rod chamber 4 and the accumulator 6, respectively; when the asymmetric cylinder retracts, the asymmetric piston pump outputs a part of the flow to supply oil to the rod chamber 4 through the flow distribution window B2, and another part of the flow to supply oil to the accumulator 6 through the flow distribution window C3, and the oil in the rodless chamber 5 returns through the flow distribution window A1. Under the condition of neglecting leakage and manufacturing error, the inlet and outlet flow rates of the asymmetric piston pump and the asymmetric cylinder will always match, and the asymmetric cylinder can be directly driven by the asymmetric piston pump for actuation, which not only reduces the throttling loss caused by valve port compensation and improves the efficiency, but also has good speed control characteristics. The flow ratio of the flow distribution windows A and B is equal to the area ratio of the rodless chamber and the rod chamber of the asymmetric cylinder, i.e. Q A :Q B =A C :A D =1:k, k is the asymmetric flow ratio.

[0004] The conventional asymmetric flow distribution structure is shown in Figure 2 , the high and low pressure transition zones of the piston chamber are arranged at the inner and outer dead point positions, and the non-dead point transition zone inevitably occupies the position of the flow distribution window, resulting in excessive compression of the flow area and difficulty in oil suction and discharge. Especially for the piston pump with high asymmetric ratio and high speed requirement, the small structure size and small number of pistons make the flow area of the C window often very small, and when the speed of the piston pump reaches the limit speed, the oil suction pressure of the C window cannot match the oil suction speed, the piston chamber on the oil suction side is not filled with oil in time, the continuity of the oil is destroyed, the outlet flow of the piston pump decreases, and the outlet flow will no longer increase with the increase of the speed of the piston pump. Therefore, the existing asymmetric flow distribution design method severely limits the improvement of the limit speed of the piston pump. SUMMARY

[0005] The present application aims at the deficiency of the existing asymmetric plunger pump valve distribution structure, and provides a transition zone bias design method for improving the limit speed of the asymmetric plunger pump.

[0006] The present application aims at providing a transition zone bias design method for improving the limit speed of the asymmetric plunger pump, comprising the following steps:

[0007] determining the main structure size of the asymmetric plunger pump and the asymmetric flow ratio value;

[0008] constructing the kinematic equation of the asymmetric plunger pump based on the asymmetric flow ratio value of the asymmetric plunger pump, to obtain the azimuth angle of the BC transition zone of the asymmetric plunger pump;

[0009] constructing the limit speed equation of the asymmetric plunger pump that can be reached based on the main structure size of the asymmetric plunger pump and the azimuth angle of the BC transition zone of the asymmetric plunger pump and considering the maximum oil suction speed limit of the valve distribution window, to obtain the limit speed of the asymmetric plunger pump that can be reached;

[0010] judging whether the limit speed meets the design requirement of the limit speed of the asymmetric plunger pump; if the requirement is met, the limit speed design of the asymmetric plunger pump is completed; if the requirement is not met, the limit speed of the asymmetric plunger pump is subjected to transition zone bias design, and the transition zone bias design is to offset the AC transition zone of the asymmetric plunger pump by a certain angle away from the dead point, so as to make the limit speed of the asymmetric plunger pump reach the design limit speed by losing a certain nominal displacement, wherein the nominal displacement loss should not exceed the design displacement loss.

[0011] Further, the transition zone bias design specifically comprises the following steps:

[0012] obtaining the constraint condition of the transition zone azimuth angle based on the kinematic analysis of the asymmetric plunger pump and considering the limit of the maximum oil suction speed and the design displacement loss, to solve the value range of the BC transition zone azimuth angle the AC transition zone azimuth angle .

[0013]

[0014] determining the parameters of the BC transition zone azimuth angle the AC transition zone azimuth angle in the value range of the BC transition zone azimuth angle the AC transition zone azimuth angle based on the size of the valve distribution disc in the asymmetric plunger pump and the machinability;

[0015] constructing the kinematic equation of the asymmetric plunger pump based on the asymmetric flow ratio value of the asymmetric plunger pump, to obtain the azimuth angle of the BC transition zone of the asymmetric plunger pump; the parameter of the AC transition zone azimuth angle the parameter of the AC transition zone, the equation of the limit speed of the symmetric pump and the equation of the nominal displacement loss are constructed, and the limit speed N of the asymmetric plunger pump is obtained d and the nominal displacement loss

[0016]

[0017] The transition zone bias design of the limit speed of the asymmetric plunger pump is completed.

[0018] Further, the porting structure of the asymmetric plunger pump meets the zero-shading design criterion, the asymmetric plunger pump cavity is always and only connected with one porting window, and the structure without oil trapping and oil stringing is constructed.

[0019] Further, in the kinematic equation of the asymmetric plunger pump, the flow rate of the porting window is equal to the change rate of the volume of the asymmetric plunger pump cavity.

[0020] Further, the porting window limited by the maximum oil suction speed is the C window with the smallest flow area, and the oil suction speed of the C window can be obtained by dividing the instantaneous flow rate of the C window when the asymmetric plunger pump cavity is fully connected with the C window by the flow area of the C window.

[0021] Further, the parameters in the range of the transition zone azimuth angle can meet the design requirements, and with the increase of the bias angle, the nominal displacement reduced by the unit bias angle also increases.

[0022] Further, the BC transition zone is the transition zone between the porting window corresponding to the rodless cavity of the asymmetric cylinder of the asymmetric plunger pump and the porting window corresponding to the accumulator.

[0023] Further, the AC transition zone is the transition zone between the porting window corresponding to the rod cavity of the asymmetric cylinder of the asymmetric plunger pump and the porting window corresponding to the accumulator.

[0024] The beneficial effects of the present application are as follows:

[0025] 1. The design method of the transition zone bias can greatly improve the flow area of the porting window, significantly improve the limit speed of the asymmetric plunger pump, and broaden the application scenarios of the closed pump control system in the fields of engineering machinery, aerospace, etc.

[0026] 2. Compared with the traditional ways of improving the limit speed of the plunger pump, such as arranging a booster tank and a booster impeller, the present application does not need to add additional auxiliary devices, has low optimization cost, and has compact structure and high integration degree.

[0027] 3. The conventional design method will completely cover the C window when the asymmetric flow ratio k exceeds a certain size, causing the asymmetric mechanism to fail. Compared with the conventional design method, the present application can complete the design of a high-asymmetry plunger pump and meet the matching needs of more asymmetric actuators. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic diagram of a non-symmetrical plunger pump control system;

[0029] Figure 2 is a conventional asymmetric flow distribution structure;

[0030] Figure 3 is a non-symmetrical flow distribution structure with transition zone biasing design;

[0031] Figure 4 is the instantaneous flow of a plunger cavity with a conventional flow distribution structure;

[0032] Figure 5 is the instantaneous flow of a plunger cavity with a transition zone biasing flow distribution structure;

[0033] Figure 6 is a comparison chart of plunger cavity flow area before and after transition zone biasing design;

[0034] Figure 7 is a flow chart of the transition zone biasing design method. DETAILED DESCRIPTION

[0035] To more clearly illustrate the embodiments of the present application, the present application will be further described below in conjunction with the drawings and specific embodiments.

[0036] As shown in Figure 3 , the present application provides a transition zone biasing design method for improving the limit speed of an asymmetric plunger pump. By shifting the AC transition zone by a certain angle away from the dead center, the flow distribution angle of the A window is appropriately reduced to increase the flow distribution area of the C window and improve the self-priming ability of the pump under high-speed working conditions. Thanks to the low compression and expansion rate of the plunger cavity near the inner and outer dead centers, a certain nominal displacement can be lost to expand the flow distribution area of the C window, which can significantly improve the limit speed of the asymmetric plunger pump.

[0037] The transition zone biasing design method for improving the limit speed of an asymmetric plunger pump includes the following steps:

[0038] Taking a 9-plunger 3.2mL / r asymmetric plunger pump as an example, the conventional asymmetric flow distribution structure is as shown in Figure 2As shown, including: flow distribution window A1, flow distribution window B2, flow distribution window C3, AB transition zone 7, BC transition zone 8, AC transition zone 9, small damping groove 10 and large damping groove 11. The plunger cavity rotates clockwise, in turn, through flow distribution window B2, flow distribution window C3 to complete the oil discharge (oil suction) action, and then through flow distribution window A1 to complete the oil suction (oil discharge) action. Among them, the BC transition zone is the transition zone between the corresponding flow distribution window of the non-symmetrical cylinder rodless cavity of the non-symmetrical plunger pump and the corresponding flow distribution window of the accumulator. The AC transition zone is the transition zone between the corresponding flow distribution window of the non-symmetrical cylinder rod cavity of the non-symmetrical plunger pump and the corresponding flow distribution window of the accumulator.

[0039] Step 1: Design the limit speed of the non-symmetrical plunger pump as 10000r / min, first determine the main structure size of the plunger pump and the required non-symmetrical flow ratio k, the main parameters are shown in the following table:

[0040] Table 1 Main structure size of plunger pump

[0041]

[0042] In an embodiment, the flow distribution structure of the non-symmetrical plunger pump meets the zero cover design criterion, the non-symmetrical plunger pump cavity is always and only connected with one flow distribution window, and the oil blocking and oil stringing structure is constructed.

[0043] Step 2: Based on the non-symmetrical flow ratio of the non-symmetrical plunger pump, the kinematic equation of the non-symmetrical plunger pump is constructed, in an embodiment, in the kinematic equation of the non-symmetrical plunger pump, the flow rate of the flow distribution window is equal to the change rate of the volume of the non-symmetrical plunger pump cavity;

[0044] Specifically, the kinematic analysis is carried out on the plunger pump, taking the position of the plunger at the top dead center as the starting point, for any angle of rotation The axial displacement L of a single plunger p Can be expressed as:

[0045]

[0046] The plunger reciprocates in the cylinder hole with the rotation of the cylinder body, periodically changes the plunger cavity volume to complete the oil suction and discharge action, and the plunger cavity volume V p At different positions is:

[0047]

[0048] In the formula The dead zone volume S when the plunger is at the inner dead point, S p Is the acting area of the plunger.

[0049] The derivative of the plunger cavity volume can obtain the instantaneous flow rate q of a single plunger i Is:

[0050]

[0051] As shown in Figure 4 , let the azimuth angle of BC transition zone be Integrating the instantaneous flow rate of each rotation interval can respectively obtain the suction and discharge oil volume V A , V B , V C of A window, B window, C window, and the ratio of the suction and discharge oil volume of each valve distribution window is:

[0052]

[0053] For the asymmetric flow ratio parameter k, the ratio of the suction and discharge oil volume of A window, B window, C window should also satisfy:

[0054] V A :V B :V c =1:k:(1-k) (5)

[0055] By combining equation (4) and equation (5), the azimuth angle of BC transition zone is:

[0056]

[0057] Solving the azimuth angle of asymmetric BC transition zone

[0058] Step 3: Based on the main structural size of the asymmetric plunger pump and the azimuth angle of BC transition zone of the asymmetric plunger pump, and considering that the limit rotation speed of the plunger pump is limited by the maximum suction speed of the valve distribution window, in an embodiment, the valve distribution window limited by the maximum suction speed is the C window with the smallest flow area, wherein the suction speed of the C window can be obtained by dividing the instantaneous flow rate when the asymmetric plunger pump cavity is completely connected with the C window by the flow area of the C window.

[0059] The suction speed v oil of the valve distribution window should satisfy:

[0060]

[0061] In the formula, v critical is the maximum suction speed allowed by the plunger pump, which is generally 3 m / s.

[0062] q max,c is the maximum instantaneous flow rate of the C window:

[0063]

[0064] In the formula, n is the rotation speed of the plunger pump.

[0065] A C For C window flow area:

[0066]

[0067] Simultaneous equations (7), (8), (9), the asymmetric plunger pump limit speed n critical For:

[0068]

[0069] Solve the asymmetric plunger pump limit speed n critical = 3535 r / min.

[0070] Step 4: determine whether the plunger pump limit speed can meet the design requirements:

[0071] n critical = 3535 r / min < N = 1000 r / min (11)

[0072] In the formula, N is the design limit speed.

[0073] If the requirements are met, the limit speed design of the asymmetric plunger pump is completed.

[0074] Step 5: offset design for asymmetric transition area, offset the AC transition area azimuth to the direction away from the dead point, improve the limit speed while the nominal displacement loss should not exceed the design value, the design maximum nominal displacement loss is 1%.

[0075] Step 6: as Figure 5 shown, the offset design BC transition area azimuth AC transition area azimuth Determine the constraint condition of the transition area azimuth. In an embodiment, the parameters in the range of the transition area azimuth value can meet the design requirements, with the increase of the offset angle, the nominal displacement reduced by unit offset angle also increases; integral for each rotation interval can get A window, B window, C window suction and discharge oil volume V A , V B , V C The ratio of the suction and discharge oil volume of each flow distribution window is:

[0076]

[0077] Meet the asymmetric flow ratio parameter k, simultaneous equations (5), (12) can be obtained:

[0078]

[0079] Maximum instantaneous flow rate of oil suction by C window of bias design q max,c is:

[0080]

[0081] where N is the design limit speed of the plunger pump.

[0082] Flow distribution area A of C window of bias design C is:

[0083]

[0084] Simultaneous equations (7), (13), and (14) give the constraint condition for meeting the design limit speed N requirement:

[0085]

[0086] Loss D of nominal displacement caused by transition zone bias loss is:

[0087]

[0088] Design value of nominal displacement loss D loss needs to be considered comprehensively. The transition zone bias will reduce the nominal displacement of the plunger pump to a certain extent, resulting in a decrease in output flow rate, but the improvement in oil suction capacity can effectively improve the volumetric efficiency of the plunger pump. The nominal displacement loss D loss should be within the design range:

[0089] D loss ≤ D critical (18)

[0090] where D critical is the design maximum nominal displacement loss.

[0091] Simultaneous equations (17) and (18) give the constraint condition for the transition zone azimuth angle:

[0092]

[0093] Therefore, the BC transition zone azimuth angle and the AC transition zone azimuth angle have the constraint condition:

[0094]

[0095] The value range of the BC transition zone azimuth angle is 141.44° to 142.18°, and the value range of the AC transition zone azimuth angle is 188.58° to 191.48°.

[0096] Step 7: According to the size and machinability of the distribution plate, the azimuth angle of the BC transition zone AC transition zone azimuth Determine the BC transition zone azimuth within the range of The AC transition zone azimuth is 142° It is 189.5°.

[0097] Step 8: Limiting speed N of asymmetric plunger pump after transition zone offset design d for:

[0098]

[0099] Nominal displacement loss of asymmetric plunger pump after transition zone offset design for:

[0100]

[0101] The comparison of the flow area of ​​the plunger cavity before and after the offset is as follows: Figure 6 As shown in the figure, the transition zone offset flow distribution design method increases the limiting speed from 3535r / min to 10926r / min compared with the existing asymmetric design method, and the limiting speed is increased by 209.1%, while the nominal displacement of the plunger pump is only lost by 0.69%. Therefore, the transition zone offset design method can significantly improve the limiting speed of the asymmetric plunger pump.

[0102] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A transition zone bias design method for increasing the limiting speed of an asymmetric plunger pump, characterized in that: The following steps are involved: Determine the main structural dimensions and asymmetric flow ratio of the asymmetric plunger pump; Based on the asymmetric flow ratio of the asymmetric plunger pump, a kinematic equation of the asymmetric plunger pump is constructed to obtain the azimuth angle of the BC transition zone of the asymmetric plunger pump; Based on the main structural dimensions of the asymmetric plunger pump and the azimuth angle of the BC transition zone of the asymmetric plunger pump and considering the maximum oil suction speed limit of the flow distribution window, a maximum speed equation that the asymmetric plunger pump can achieve is constructed to obtain the maximum speed that the asymmetric plunger pump can achieve; Determining whether the limit speed meets the limit speed design requirement of the asymmetric plunger pump; If the requirements are met, the limiting speed design of the asymmetric plunger pump is completed; If the requirements are not met, the maximum speed of the asymmetric plunger pump will be designed with a transition zone offset. The transition zone offset design is to offset the AC transition zone of the asymmetric plunger pump away from the dead point by a certain angle, so that the maximum speed of the asymmetric plunger pump reaches the designed maximum speed by losing a certain nominal displacement. Among them, the nominal displacement loss should not exceed the designed displacement loss.

2. A transition zone offset design method for increasing the limiting speed of an asymmetric plunger pump according to claim 1, characterized in that: The transition zone bias design specifically includes the following steps: Based on the kinematic analysis of the asymmetric plunger pump and considering the limitations of the maximum oil suction speed and the design displacement loss, the constraints of the transition zone azimuth angle are obtained, and the BC transition zone azimuth angle is solved. AC transition zone azimuth The value range of is: Where, k is the asymmetric flow ratio of the distribution windows A and B, N is the design limit speed, R1 is the inner diameter of the waist groove of the distribution plate, R2 is the outer diameter of the waist groove of the distribution plate, R is the radius of the plunger distribution circle, d p is the plunger diameter, v critical The maximum oil suction speed allowed for the plunger pump. D is the cylinder waist groove angle, critical is the maximum displacement loss, β is the swash plate inclination angle; According to the size and machinability of the distribution plate in the asymmetric plunger pump, the azimuth angle of the BC transition zone AC transition zone azimuth Determine the BC transition zone azimuth within the range of AC transition zone azimuth Parameters; Based on the BC transition zone azimuth Parameters and AC transition zone azimuth The parameters of the symmetrical pump are used to construct the limiting speed equation and the nominal displacement loss equation, and the limiting speed N of the asymmetrical plunger pump is obtained. d and nominal displacement loss Complete the transition zone offset design for the limiting speed of the asymmetric plunger pump.

3. The transition zone offset design method for increasing the limiting speed of an asymmetric plunger pump according to claim 1, characterized in that: The flow distribution structure of the asymmetric plunger pump complies with the zero-cover design principle. The asymmetric plunger pump cavity is always and only connected to one flow distribution window, thereby forming a structure without oil entrapment and oil cross-contamination.

4. The transition zone offset design method for increasing the limiting speed of an asymmetric plunger pump according to claim 1, characterized in that: In the kinematic equation of the asymmetric plunger pump, the flow rate of the flow distribution window is equal to the rate of change of the volume of the asymmetric plunger pump cavity.

5. The transition zone offset design method for increasing the limiting speed of an asymmetric plunger pump according to claim 1, characterized in that: The flow distribution window limited by the maximum oil suction speed is the C window with the smallest flow area. The oil suction speed of the C window can be obtained by dividing the instantaneous flow when the asymmetric plunger pump cavity is fully connected to the C window by the flow area of ​​the C window.

6. The transition zone offset design method for increasing the limiting speed of an asymmetric plunger pump according to claim 2, characterized in that: The parameters within the range of the transition zone azimuth angle values ​​can all meet the design requirements. As the offset angle increases, the nominal displacement reduced by a unit offset angle also increases.

7. The transition zone offset design method for increasing the limiting speed of an asymmetric plunger pump according to claim 1, characterized in that: The BC transition zone is a transition zone between the flow distribution window corresponding to the rodless chamber of the asymmetric cylinder of the asymmetric plunger pump and the flow distribution window corresponding to the accumulator.

8. The transition zone offset design method for increasing the limiting speed of an asymmetric plunger pump according to claim 1, characterized in that: The AC transition zone is a transition zone between the flow distribution window corresponding to the rod chamber of the asymmetric cylinder of the asymmetric plunger pump and the flow distribution window corresponding to the accumulator.

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