A new design method of positive displacement rotor pump mechanism

Abstract

The application discloses a design method of a novel positive displacement rotor pump mechanism.Compared with similar pump mechanisms, the positive displacement rotor pump mechanism has simple structure, does not need gears and crankshafts in a transmission mechanism, is convenient to manufacture, and is not limited by the size of the overall structure.The inner cavity of a pump body is composed of four tangent circular arcs.The outer shape of a rotor is mainly composed of two symmetrical conjugate curved surfaces, and the rotor is composed of a needle bearing, a circular arc, a light shaft or a long groove, and a spring-loaded isolation sliding block.A rotating shaft is composed of a cross sliding block mechanism composed of a shaft sleeve and a light shaft or a needle bearing and a long groove on the rotor.The pump mechanism finds an intersection point of a connecting line between a center of a small circular arc of the inner cavity and the small circular arc as a conjugate curve to isolate the inlet and outlet cavities of the sealed cavity, so that a volume effect is formed.The mechanism is widely applied, and the rotor is driven by the rotating shaft to be a pump, or the rotor is driven by fluid to be a flowmeter.Both the pump and the flowmeter can realize high-speed and high-efficiency operation under harsh working conditions.

Description

Technical Field

[0001] This invention relates to the technical field of mechanical equipment, and to a novel positive displacement rotor pump mechanism that can be applied in both industrial and daily life, such as pumps, compressors, boosters, industrial flow meters, household water meters, gas meters, etc., with wide applications. Background Technology

[0002] To address some of the shortcomings of traditional positive displacement rotary pumps, such as their complex structure leading to increased manufacturing difficulty, high transmission precision requirements (most rotary pumps require a pair of high-precision transmission gears to ensure the movement trajectory of the sealing curve), and the presence of large reciprocating motion mechanisms within their working area, which can easily lead to jamming during operation and subsequent "crash" or limited usage conditions, these solutions are needed. Summary of the Invention

[0003] This invention presents a novel positive displacement rotor pump mechanism with a simple cavity structure composed of four tangent circular arcs, facilitating manufacturing. It has few sealing points, requiring a maximum of three line seals, easily ensuring sealing accuracy and achieving high volumetric efficiency. The transmission mechanism is simple and reliable, cleverly utilizing a cross-slider mechanism composed of a shaft and rotor as the transmission mechanism for rotor operation. This not only ensures accurate synchronous and in-phase movement of the shaft and rotor but also enables reversible, high-speed, and high-efficiency operation.

[0004] This novel positive displacement rotor pump mechanism of the present invention places the long-stroke reciprocating linear motion mechanism within the sealed area, while the isolated micro-motion slider in the working area has a stroke approximately 1 / 7 of the rotor slider's linear motion stroke. This significantly improves the reliability of the mechanism's operation.

[0005] 1. Design of the pump body cavity

[0006] To simplify design parameters, the concept of a base circle is introduced as a primary parameter. The minimum length along the rotor's axis of symmetry is assumed to be the diameter of two base circles, and its center of rotation lies at the point of tangency between the two base circles. For example... Figure 1 , Figure 2 As shown, the known parameters are: base circle diameter D, small arc radius R1, transition arc radius R2, and large arc radius R3.

[0007] When the center line of symmetry of the rotor coincides with the center line of symmetry of the pump body, the center distance H from the tangent points of the two base circles to the shaft is crucial. H is a key dimension for the volumetric effect; the larger this center distance, the higher the volumetric efficiency. However, this center distance is also twice the sliding distance of the rotor on the shaft. Therefore, the size of this center distance is determined by the pump structural design.

[0008] In addition, the central angle θ of the small arc. Based on experience, it is best to keep it between 20° < θ < 30° to ensure that the rotor is not easily interfered with when moving in the cavity.

[0009] Assuming the base circle lies on the horizontal line of the cavity, one side is at the center of the rotation axis, and the other side is tangent to the great circle arc, let the radius of the great circle arc be R3. Then we have the formula...

[0010]

[0011] After calculating R3, round it to the smaller value (based on experience) to determine the radius of the large arc R3.

[0012] like Figure 1 , Figure 2 As shown, the radius R2 of the transition arc connecting and tangent to the two arcs of different sizes has the formula...

[0013]

[0014] After calculating R2, round it off. In fact, provided the four arcs are tangent, R1, R2, and R3 can all be adjusted as needed. However, after adjustment, the semi-circular central angle θ must be verified using the formula to ensure it is within the specified range. This ensures that the rotor does not interfere during operation.

[0015] 2. Rotor Design

[0016] A rotor is a composite moving component, such as Figure 1 and Figure 2 The rollers sliding within the pump body cavity on the rotor shown have two forms: one where the rotor's own arc slides within the cavity, and the other where rollers installed on the rotor roll within the cavity. The structure should be selected based on the specific requirements. Another moving component is the reciprocating slider, which also has two forms: one is a smooth shaft mounted on the rotor's center line of symmetry, and the other can be a long groove formed on the center line of symmetry. The choice should be made based on the specific circumstances.

[0017] The rotor is equipped with a moving component called a micro-motion isolation slider. It is called micro-motion because the stroke of the isolation slider is about 1 / 3.5 times the distance H between the center of the rotating shaft and the tangent point of the two base circles.

[0018] The calculation method for the conjugate curve on the rotor is based on the instantaneous center point p generated when the needle rollers or the rotor's own circular arc contact the transition arc or the large circular arc during their movement within the cavity. The distance between point p and the center of the small circular arc is a definite value. Furthermore, the intersection of this line with the small circular arc is the coordinate point with the rotor center as the origin.

[0019] To ensure the accuracy of the curve, we first need to find the point of tangency between the transition arc and the great arc on the rotor, and then set the angle of rotation of the shaft as α.

[0020] In the formula, R4 is the radius of the needle roller. C = D + H - R3 is the center distance between the center of the great arc and the center of the shaft, and δ is the angle between the line connecting the center of the transition arc and the center of the great arc and the center line of symmetry of the cavity; all are known parameters. The formula determines the shaft rotation angle when the needle rollers on the rotor reach the intersection of the transition arc and the great arc. We discuss the formula for the conjugate curve in two segments. Note that to ensure the accuracy of the conjugate curve, this rotation angle value must be taken as a curve point; the same value can be obtained regardless of which segment of the formula is used.

[0021] First, we discuss the case of the needle roller on the transition arc. Draw a line connecting the center of the needle roller to the center of the transition arc, and a perpendicular line from the center of the shaft to the rotor's line of symmetry. Extend these two lines to intersect at point p, which is the instantaneous center point. Next, draw a line connecting point p to the center of the smaller arc. The intersection of this line and the smaller arc is the point of the conjugate curve. Calculate the length of the line connecting this point to the center of the shaft to determine the coordinates of the conjugate curve on the rotor. The following uses formulas to derive these points one by one. Distance between the center of the shaft and the center of the roller.

[0022]

[0023] In the formula, R2 is the radius of the transition arc, R4 is the radius of the needle roller, δ is the angle between the center of the shaft and the center line of the transition arc and the center line of symmetry of the pump body, α is the angle between the shaft and the center line of symmetry of the pump body during rotation, and J is the distance between the center of the shaft and the center of the transition arc. Except for angle α, all other parameters are known. The distance between the center of the shaft and point p can be calculated.

[0024]

[0025] Distance from point p to the center of the small arc

[0026] The point where the line connecting the instantaneous center point p and the center of the small arc intersects the arc, and the distance E between this intersection point and the center of the rotation axis.

[0027]

[0028] After finding line segment E, find the angle β between line segment E and the center line of symmetry of the rotor.

[0029]

[0030] Therefore, the formula for the coordinate points of the conjugate curve with the rotor center as the origin can be derived when the rotor needle roller is on the transition arc:

[0031] X = Ecosβ + (D - R⁴ - L) Y = Esinβ

[0032] By analogy, we can derive the coordinate formula for the needle roller on the great circle arc. The only difference is that the instantaneous center point p is on the line connecting the center of the great circle arc and the center of the needle roller on the rotor.

[0033] Distance between the center of the rotating shaft and the center of the needle roller

[0034] In the formula, R3 is the radius of the large arc, R4 is the radius of the needle roller, and C is the center distance between the center of the large arc and the center of the rotating shaft.

[0035] Similarly, the distance from the center of the axis of rotation to point p can be calculated.

[0036]

[0037] With the distance N from the center of the pivot to point p, we can use the previous formula to calculate the distance from point p to the center of the small arc and the distance from the center of the pivot to the intersection of the small arc.

[0038] Finally, the coordinates of the needle rollers on the rotor as they move on the large circular arc are determined, and the endpoint is identified based on the structure. Note that when the rotor rotates to 90 degrees, the sign of the addition and subtraction of the angles needs to be changed due to the change in the position of angle β. Since each rotation of the rotor within the cavity corresponds to a conjugate point on the small circular arc, connecting these conjugate points naturally yields the required conjugate curve. As a continuous curve, regardless of whether the needle rollers on the rotor move on the transition circular arc or the large circular arc, this conjugate curve will always remain tangent to the small circular arc, forming a sealing line that divides the cavity inlet and outlet into two chambers, creating a conjugate surface during solid machining.

[0039] In fact, the above method can be extended to design a positive displacement pump mechanism with a symmetrical pump body cavity structure composed of multiple circular arcs, which is perfectly applicable. However, it reverts to the shortcomings of traditional positive displacement pump mechanisms, increasing manufacturing difficulties, requiring more sealing lines, increasing the number of isolation sliders, and changing its stroke size.

[0040] 3. Kinematic and force analysis of the mechanism

[0041] When the rotor's center line of symmetry coincides with the pump body's center line of symmetry, the rotor's center is below the shaft's center. If used as a flow meter, the rotor is driven by an external force, and fluid enters from the right. The rotor will rotate clockwise under the external force because the longer arm, with the shaft as its fulcrum, is below the pump body (e.g.,...). Figure 1 (As shown).

[0042] When the rotor's center line of symmetry is approximately 90° to the pump body's center line of symmetry, the engagement line between the rotor's needle rollers and the cavity's arc has closed the inlet, while the engagement line between the micro-movement slider's arc and the needle rollers on the rotor has not yet reached the outlet position. At this point, the enclosed volume within the pump body is the volume discharged in one rotor rotation. Simultaneously, because the inlet fluid continues to push the rotor, under the external force generated by the inlet fluid, the rotor still rotates clockwise. Therefore, when this mechanism is used as a flow meter, the rotor's rotation direction is the opposite of the fluid inlet direction. Conversely, when used as a pump or compressor mechanism, the shaft's rotation direction is the same as the rotor's rotation direction.

[0043] Figure 1 , Figure 2 As can be seen, the angle ψ between the sliding velocity direction of the shaft and the force direction along the line connecting the center of the needle rollers on the rotor and the center of the arc where the pump body is located is very small. Therefore, the mechanism moves very smoothly. Attached Figure Description

[0044] Figure 1 This diagram illustrates the working principle of a cross-slider mechanism, where needle rollers on the rotor rotate within the pump body cavity. The fixed optical axis along the rotor's symmetrical center line and the rotating shaft sleeve (not shown in the diagram) constitute this mechanism. This mechanism is suitable for high-speed operation.

[0045] Figure 2 This diagram illustrates the working principle of a cross-slider mechanism, where the rotor's own circular arc rotates within the pump's internal cavity. The long groove along the rotor's symmetrical center line and the fixed needle rollers on the rotor form this mechanism. This mechanism has a simple structure and is suitable for harsh working environments.

[0046] In the diagram, α represents the angle of rotation of the shaft.

[0047] In the diagram, D represents the diameter of the base circle.

[0048] In the diagram, C represents the distance between the center of the great circle arc and the center of the axis of rotation.

[0049] In the figure, δ is the angle between the line connecting the center of the transition arc and the center of the great arc and the center line of symmetry of the cavity.

[0050] In the figure, H is the distance from the point of tangency to the center of the rotating shaft when the centers of the two tangent base circles are both on the symmetrical center line of the pump body and are tangent to the large and small circular arcs.

[0051] In the diagram, θ is the central angle of the small arc.

[0052] In the figure, ψ represents the pressure angle.

[0053] In the diagram, J represents the distance between the center of the rotating shaft and the center of the transition arc.

[0054] In the diagram, L represents the distance between the center of the rotating shaft and the center of the needle roller.

[0055] In the diagram, N represents the distance from the center of the axis of rotation to point p.

[0056] In the figure, F is the distance from the instantaneous center point p to the center of the small circular arc.

[0057] In the diagram, E represents the distance between the intersection of the line connecting the center of the rotation axis to the instantaneous center point p and the center of the small arc, and the point on the arc.

[0058] In the figure, β is the angle between the line connecting the center of the shaft and the center of the small arc and the center line of the rotor's symmetry.

[0059] In addition, considering the problem of "trapped oil" at the outlet, a venting groove needs to be opened on the end cap, which is not shown in the figure. Detailed Implementation

[0060] To design an ideal positive displacement pump mechanism, we first model it using 3D software, in this case, Autodesk Inventor. We create the individual components and finally the rotor's outline. The formula for the conjugate curve and all known parameters are input into Excel, with rotation angles increasing in increments of 1° or less, to calculate the curve's coordinates. Then, we open the rotor model in Autodesk Inventor, using the rotor center as the origin of the coordinate system.

[0061] Select the curve to insert into the rotor coordinate system, adjust its connection position, and extrude it into the rotor's conjugate curve surface to complete the rotor modeling. Assemble according to the pump mechanism's technical requirements, providing two transition constraints: one is the arc surface of the rollers or arc surface on the rotor and the arc surface of the pump body cavity, and the other is the arc surface of the micro-motion isolation slider and the arc surface of the pump body cavity.

[0062] After assembly, the rotor is rotated using a drive angle constraint. Simultaneously, a collision check is enabled in the drive interface to verify whether interference occurs during rotor movement. The rotor can be driven in two ways: one is by rotating the shaft (simulating pump operation), and the other is by rotating the rotor itself (simulating flow meter operation), both achieving rotor rotation within the pump body cavity. During rotation, interference at a specific location can be detected, along with the magnitude of the interference fit. If interference is present, some parameters can be adjusted or the curved surface can be slightly modified as needed. This is because our conjugate curve is designed based on a fully contact small circular arc, and in engineering applications, the sealing gap during movement only needs to be within 0.02mm.

Claims

1. A positive displacement rotor pump mechanism, comprising a pump body, wherein the inner cavity of the pump body is composed of four tangent circular arcs forming a symmetrical heart-shaped cavity, the four tangent circular arcs being a small circular arc, a transition circular arc located inside the small circular arc, and a large circular arc located between two of the transition circular arcs; a rotor is disposed within the inner cavity of the pump body, the rotor having two symmetrical conjugate curved surfaces corresponding to the inner cavity of the pump body, a needle roller disposed at one end of the rotor or an arc integrally formed with the rotor, a spring-loaded isolation slider disposed at the other end of the rotor, and a light shaft mounted on the symmetrical center line of the rotor. The rotating shaft is mounted on the optical shaft via a bushing or roller; when the rotor rotates in the internal cavity of the pump body, the position where the rotor contacts the transition arc or the large arc will generate a corresponding instantaneous center point p. The point where the line connecting the instantaneous center point p to the center of the small arc intersects the small arc is the conjugate point. The rotor has a corresponding conjugate point for each rotation angle. With the rotation center of the rotor as the origin of the coordinate system, connecting the conjugate points determines the conjugate curve of the rotor. The conjugate curve is machined to form a conjugate surface. Let the lengths of the two ends on the axis of symmetry of the rotor be the diameters of the two base circles, and let the center of rotation of the rotor be at the point of tangency of the two base circles, with the diameter of the base circles being D, and the radius of the smaller arc being... The radius of the transition arc The radius of the great circle arc ; +(D / 2)； ； in, H is the center distance from the point of tangency of the two base circles to the center of the rotating shaft, and θ is the central angle of the small arc. The bushing or roller sliding on the rotating shaft is used as a cross-slider mechanism to match the optical axis of the rotor. The rotor is driven to rotate in the pump body cavity while sliding on the rotating shaft. In this way, the synchronous and co-directional movement of the rotating shaft and the rotor is determined.

2. The positive displacement rotor pump mechanism according to claim 1, characterized in that: The central angle of the small arc is between 20° and 30°.

3. The positive displacement rotor pump mechanism according to claim 1, characterized in that: The spring in the isolation slider functions to form two sealing lines at both ends of the rotor within the pump body cavity.

4. The positive displacement rotor pump mechanism according to claim 1, characterized in that: The cross-slider mechanism is located inside the rotor and is sealed and isolated from the working area of ​​the pump body cavity.

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