A low noise, variable flow internal meshing gear pump with built-in single / dual suction switching structure

Abstract

This invention discloses a low-noise, variable-flow internal gear pump with a built-in single / double suction switching structure. The pump body has two adjacent chambers, each housing an external gear and an internal gear ring, which, together with upper and lower bearings, form upper and lower gear pairs. The upper and lower gear pairs rotate coaxially, with the direction of rotation being the same as the rotational speed. Each gear pair has an independent inlet and an independent outlet. The inlet pipe merges the independent inlets into one inlet, and the outlet pipe merges the two independent outlets into one outlet. The pump body also contains a reciprocating push-pull slide valve. When the slide valve is pulled outward to its full position, it guides the medium from the lower gear pair into the outlet pipe, and the upper and lower gear pairs are in parallel mode, with an internal double suction structure, which can meet the requirements of high flow rate conditions. When the slide valve is pushed inward to its full position, it guides the medium from the lower gear pair into the inlet chamber of the upper gear pair, and the check valve closes, and the upper and lower gear pairs are in series mode, with an internal single suction structure, which can meet the requirements of low flow rate conditions.

Description

Technical Field

[0001] This invention belongs to the technical field of internal gear pumps for conveying clean media with a certain degree of lubrication, specifically a low-noise, variable-flow internal gear pump with a built-in single / double suction switching structure. Background Technology

[0002] Internal gear pumps utilize one or more meshing gear pairs (external gear and internal gear ring) sealed within the pump body to operate based on changes in the volume of the medium. These meshing gear pairs are the core components of the gear pump. The small center distance and compact structure of internal gear pairs result in small size, light weight, and less material usage in internal gear pumps. Because the external gear and internal gear ring rotate in the same direction, the relative sliding speed between the tooth profiles is low, leading to less wear on the tooth surfaces and a longer service life for internal gear pumps. Furthermore, the high overlap ratio of internal gear pairs and the low contact stress between the tooth surfaces contribute to smoother transmission in internal gear pumps.

[0003] Internal gear pumps have many advantages, such as high discharge pressure, low flow pulsation, low pressure pulsation, low noise, high volumetric efficiency, reliable operation, resistance to contamination, easy processing and manufacturing, and low cost. They are widely used in the field of pumping media with high discharge pressure.

[0004] Internal gear pumps have various types of gear tooth profiles. Traditional tooth profiles are involute, but during meshing, a portion of the liquid medium is trapped between the teeth. The trapped volume changes with gear rotation. Since the liquid has a high elastic modulus, this change in trapped volume leads to a sharp increase in pressure, which is a major source of vibration, noise, and energy loss. Straight-tooth conjugate tooth profiles have a trapped volume approximately 1 / 10 that of involute tooth profiles, essentially solving the oil trapping problem. Therefore, straight-tooth conjugate tooth profile internal gear pumps can simultaneously meet requirements for extremely high discharge pressure (e.g., around 32 MPa), extremely high volumetric efficiency, and lower vibration and noise.

[0005] Once the structural parameters are determined, the flow rate of a spur gear conjugate internal gear pump is often linearly proportional to its rotational speed. Variable speed drive is typically used to achieve variable flow rate adjustment under extremely high discharge pressures. However, when an internal gear pump operates at high speeds, its inherent vibration and noise increase rapidly and are not reduced by improving tooth surface machining accuracy or tooth profile correction; spur gear conjugate internal gear pumps are no exception. Therefore, the most reliable way to achieve low-noise operation is still to maintain low speed, but this does not allow for variable flow rate adjustment.

[0006] The reliable and stable way to simultaneously achieve variable flow regulation under high discharge pressure and low noise operation is to control the gear speed to a minimum (e.g., not exceeding 7000 r / min) through overall rational design, thereby satisfying variable flow regulation under high discharge pressure while maintaining low noise operation. This is the problem that this invention aims to solve. Clean fluid media include, but are not limited to, fuels, lubricating oils, and hydraulic oils.

[0007] To achieve variable flow rate regulation and low noise operation under high discharge pressure, spur gear pumps with conjugate internal meshing are typically implemented by using multiple pumps in series or parallel configurations with integrated piping and control logic. However, this approach involves numerous issues related to pipeline connections, control logic, space, and weight, and its overall effectiveness often falls short of expectations due to its excessive complexity.

[0008] Among existing related patent technologies, such as the double external gear pump disclosed in patent document (CN112879281A), this patent uses an external gear structure. During gear meshing, there will inevitably be changes in the trapped oil volume, generating periodic pressure shocks. Although the patent mentions that "increasing the number of driven gears can reduce flow pulsation," it does not detail the specific design of the trapped oil unloading groove. At high speeds, the peak trapped oil pressure may still cause strong noise. The phase coupling of the double-stage gear meshing poses a risk: the first and second stage driven gear sets are driven by the same driving gear. If the meshing phase of the two stages of gears is not optimally matched, a vibration superposition effect may occur, which will exacerbate the overall noise of the machine. At high speeds, the gear meshing frequency increases, and the pressure pulsation frequency may be close to the natural frequency of the plunger, causing fluid-structure coupled vibration.

[0009] Therefore, through searching the patent network and relevant domestic and foreign materials, no low-noise, variable-flow, high-pressure internal gear pump with built-in single and double suction switching structure described in this invention has been found. Summary of the Invention

[0010] The present invention provides a low-noise, variable-flow, high-pressure internal gear pump with a built-in single / double suction switching structure. The design concept of the present invention is to integrate two sets of external gears and an internal gear ring, i.e., two gear pairs, inside a vertical pump body of an internal gear pump. The two gear pairs are adjacent to each other but independently handle suction and discharge.

[0011] In this invention, the upper gear pair is equipped with a one-way valve at the inlet to control the on / off state; the lower gear pair has no one-way valve at the inlet and is always connected to the inlet pipe of the internal meshing gear pump.

[0012] In this invention, a reciprocating or rotating slide valve is installed inside the pump body as a single / double suction switching structure. The slide valve is located near the pump body outlet pipeline. Moving or rotating the slide valve can guide the medium discharged from the lower gear pair to the pump outlet or into the inlet area of ​​the upper gear pair. When the lower gear pair guides the medium to the pump outlet, the upper and lower gear pairs form a parallel double suction structure, suitable for high flow conditions. When the lower gear pair guides the medium to the inlet area of ​​the upper gear pair, the one-way valve in the inlet of the upper gear pair closes, and the upper and lower gear pairs form a series single suction structure, suitable for low flow conditions.

[0013] In this invention, both the upper and lower gear pairs adopt a spur tooth conjugate structure, and the characteristic parameters of the two gear pairs are the same, which ensures high volumetric efficiency at high discharge pressure. The flow rate and rotational speed are basically linearly proportional, and the flow pulsation and pressure pulsation remain synchronized. Since the upper and lower gear pairs are coaxial and rotate at the same speed, the flow rate of the double-suction structure is basically twice that of the single-suction structure when the discharge pressure is the same.

[0014] In this invention, by controlling the movement or rotation of the slide valve, the flow direction of the upper and lower gear pairs can be switched, enabling rapid switching between low-flow conditions in a series single-suction structure and high-flow conditions in a parallel double-suction structure. However, the actual rotational speed in the high-flow condition is slightly higher than that in the low-flow condition, but not twice as high. Effectively controlling the rotational speed at a lower value can simultaneously meet the requirements of high discharge pressure, variable flow regulation, and low-noise operation, solving the aforementioned problems. This has significant practical implications.

[0015] To achieve the above objectives, the technical solution adopted by this invention is: a low-noise, variable-flow internal gear pump with a built-in single / double suction switching structure, comprising a pump body, an external gear, and an internal gear ring. The pump body has two adjacent chambers, each housing an external gear and an internal gear ring, which, together with an upper bearing and a lower bearing, form an upper and lower gear pair. The upper and lower gear pairs rotate coaxially, with the direction of rotation being the same as the rotational speed. Each upper and lower gear pair has an independent inlet and an independent outlet. The inlet pipe merges the independent inlets into one inlet, and the outlet pipe merges the two independent outlets into one outlet. The pump body also contains a reciprocating push-pull slide valve. When the slide valve is pulled outward to its final position, it guides the medium from the lower gear pair into the outlet pipe, and the upper and lower gear pairs are in parallel mode, with an internal double suction structure, which can meet the requirements of high-flow conditions. When the slide valve is pushed inward to its final position, it guides the medium from the lower gear pair into the inlet chamber of the upper gear pair, and the check valve closes, and the upper and lower gear pairs are in series mode, with an internal single suction structure, which can meet the requirements of low-flow conditions.

[0016] Furthermore, the pump body houses two sets of external gears and an internal gear ring, equipped with upper and lower bearings. The shaft holes and outer circles of the upper and lower bearings are eccentric, which can prevent the bearings from rotating with the shaft. The shaft hole in the middle of the pump body acts as a sliding bearing. The shaft hole in the middle has a radial hole that connects to the inlet cavity of the lower gear pair, guiding the medium in the middle shaft hole into the inlet cavity to form a flow for heat dissipation.

[0017] Furthermore, the inlet cavity of the upper gear pair of the pump body is equipped with two one-way valves to ensure that the medium can only flow into the inlet cavity in one direction. The two one-way valves work together with the slide valve to form a single and double suction structure inside the pump body. The slide valve hole on the outlet side of the pump body is equipped with a slide valve that can be reciprocated and pushed and pulled, which improves the structural foundation for the built-in single and double suction structure.

[0018] Furthermore, the slide valve is a reciprocating push-pull structure, and the valve wall of the slide valve has three sets of holes. The first set of holes is a single-hole structure, which is always connected to the outlet cavity of the lower gear pair. When the slide valve is pulled outward to the end, the second set of holes connects the outlet cavity and the outlet pipe. When the slide valve is pushed inward to the end, the third set of holes connects the outlet cavity to the inlet cavity of the upper gear pair through the internal channel. The second set of holes and the third set of holes are both parallel double-hole structures with equal flow area.

[0019] Furthermore, the radial clearance between the slide valve and the slide valve orifice on one side is 0.02mm~0.06mm, balancing sealing effect and slide valve push-pull speed; to improve the sealing effect of the double orifice, after the double orifice is pushed and pulled closed, the double orifice of the slide valve and the double orifice of the slide valve are not closely attached to the boundary but are offset by a certain distance, ensuring better sealing in the closed state and reducing leakage; to improve the push-pull response speed of the slide valve, the pump body is provided with a channel at the top of the slide valve orifice to avoid liquid entrapment causing slide valve jamming.

[0020] Furthermore, in addition to the reciprocating push-pull structure, the slide valve also adopts a rotary slide valve structure. The slide valve rotates back and forth around its own axis with a limited range. The first set of holes remains unchanged, while the second and third sets of holes are both rectangular single-hole structures. The length direction of the single hole is the axis direction of the slide valve, and the width direction is the circumferential direction.

[0021] Furthermore, the valve port of the pump body is provided with an axial side hole to improve the response speed when the check valve is opened and closed.

[0022] Furthermore, the one-way valve is a cone valve, a flat valve, or a ball valve.

[0023] Furthermore, the gear pump adopts a spur tooth conjugate structure, which reduces oil trapping and flow pulsation. Two external gears and two internal gear rings serve as rotating components. The internal gear rings and external gears also adopt a helical tooth structure, but the axial inclination angle of the helical teeth is limited to not connecting the pump inlet and outlet, further reducing vibration and noise.

[0024] Furthermore, the external gear is a straight line, and the internal gear ring is a straight conjugate tooth profile curve. The straight conjugate tooth profile curve is composed of discrete points, or is composed of multiple spline curves that have been smoothly fitted through error control.

[0025] Compared with the prior art, the present invention has the following significant advantages:

[0026] 1. The internal gear pump of this invention can achieve variable flow rate adjustment under extremely high discharge pressure, and also features low noise operation.

[0027] 2. The internal gear pump of this invention has a simple structure, few parts, and light weight; it is suitable for low-noise and low-vibration conveying of lubricating media, and the flow rate and speed are basically linearly related.

[0028] 3. The overall structure has a small size, making it easy to disassemble and maintain; it operates smoothly and is suitable for environments with strict space restrictions and strict requirements for disassembly and maintenance. 4. The tooth profile of the internal gear ring can be smoothly fitted into a combination of multiple circular arcs, which not only reduces the machining difficulty of the internal gear ring, but also results in good tooth profile smoothness and high surface finish, greatly simplifying the machining and inspection methods. This is beneficial to improving machining efficiency. Attached Figure Description

[0029] Figure 1 This is an external view of the low-noise, variable-flow internal gear pump with built-in single / double suction switching structure of the present invention. Figure 2 This is a cross-sectional view of the low-noise, variable-flow internal gear pump with built-in single / double suction switching structure of the present invention. Figure 3 An explosion diagram of the low-noise, variable-flow internal gear pump with built-in single / double suction switching structure of the present invention. Figure 4 Schematic diagram of slide valve, sealing ring and cap; Figure 5 This is a schematic diagram showing the slide valve switching to the double-suction structure state; Figure 6 This is a schematic diagram showing the slide valve switching to the single-suction structure state. Figure 7 This is a schematic diagram of a one-way valve structure; Figures 8-1 to 8-8 Schematic diagram of multiple cross-sections of the pump body; Figure 9 Schematic diagram of mechanical seal and shaft retaining ring; Figure 10 This is a schematic diagram of the pump cover. Figure 11 This is a schematic diagram of the upper and lower bearings; Figure 12 Schematic diagram of bearing, adjusting shim, internal gear ring, external gear, shaft and key; Figure 13 This is a schematic diagram illustrating the meshing principle of the external gear with a straight line g1 and the internal gear ring with a straight line conjugate curve g2. Figure 14 This is an enlarged schematic diagram of the external gear straight line g1 and the internal gear ring tooth profile g2. Figure 15 This is a schematic diagram of the smooth fitting of the straight line conjugate curve circular arc of the internal gear tooth profile. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0031] For ease of description, this invention is assumed to be a vertical structure, with the two gear pairs located in adjacent upper and lower pump chambers. If a horizontal structure is used, "front and back" or "left and right" should be used to refer to it, without affecting the essential content of this invention.

[0032] like Figures 1 to 3 As shown, the low-noise, variable-flow internal gear pump with built-in single / double suction switching structure of the present invention includes a mechanical seal 1, a pump cover 3, a rolling bearing 5, an upper bearing 7, an internal gear ring 8, an external gear 9, a shaft 10, a slide valve 11, a sealing ring 12, a sealing cap 13, an inlet pipe 14, a valve core 15, a spring 16, a lower bearing 18, a pump lower cover 19, an internal gear ring 20, an external gear 21, an outlet pipe 22, and a pump body 25.

[0033] The pump upper cover 3, pump body 25, and pump lower cover 19 form the main structure of the internal gear pump. Screws 3a and 19a are used for connection and fastening between the pump upper cover 3 and pump body 25, and between the pump lower cover 19 and pump body 25, respectively. An internal gear ring 8 and an external gear 9 form the upper gear pair on the upper part of the pump body 25; an internal gear ring 20 and an external gear 21 form the lower gear pair on the lower part of the pump body 25. The external gears 9 and 21 of both gear pairs rotate together with the shaft 10, with the direction of rotation being the same as the rotational speed. Both external gears 9 and 21 have double keyways, which engage with the flat keys 10a and 10c and 10b and 10d on the shaft 10 for transmission.

[0034] The upper bearing 7 and the lower bearing 18 are sliding bearings that bear the radial force of the shaft 10. They are also essential components of the enclosed volume formed by the upper and lower gear pairs. The rolling bearing 5 provides axial positioning of the shaft 10 and bears the axial force. An adjusting shim 6 separates the rolling bearing 5 from the upper bearing 7. A shaft retaining ring 4 locks the rolling bearing 5 onto the shaft 10.

[0035] The inlet pipe 14, outlet pipe 22, and pump body 25 are connected and fastened by screws 14a and 23, respectively. Gaskets 17 and 24 provide static sealing between the inlet pipe 14, outlet pipe 22, and pump body 25. The valve core 15, spring 16, inlet pipe 14, and pump body 25 form a one-way valve structure, ensuring that the medium can only flow unidirectionally from the inlet pipe 14 into the inlet area of ​​the upper gear pair. There is no one-way valve structure at the inlet of the lower gear pair.

[0036] The slide valve 11, sealing ring 12, sealing cap 13 and pump body 25 form a built-in single and double suction switching structure. The movement of slide valve 11 can realize the series and parallel connection of the upper gear pair and the lower gear pair in the working mode, that is, the single and double suction structure in the flow.

[0037] The upper and lower gear pairs each have their own independent inlet and outlet, with both inlets on the same side and both outlets on the same side. Inlet pipe 14 connects the two inlets into a single main inlet, and outlet pipe 22 connects the two outlets into a single main outlet.

[0038] Mechanical seal 1 is fastened to pump cover 3 by screw 1a. The positioning of mechanical seal 1 on shaft 10 is achieved by shaft retaining ring 2.

[0039] like Figure 4 As shown, the slide valve 11 has a hollow structure and a sealing groove 11a is machined on its surface to accommodate the sealing ring 12. Because of the high sealing pressure, the present invention provides two sealing rings 12. The slide valve 11 is placed in the slide valve hole 2503 of the pump body 25.

[0040] The cap 13 is also a hollow structure, but the side with the smaller diameter of the cap 13 is machined with an external thread, which is screwed into the internal thread of the pump body 25 to limit the slide valve 11 and prevent it from being pulled out. A threaded hole 11e is machined on the outer end face of the slide valve 11. The drive mechanism passes through the cap 13 and connects with the threaded hole 11e to pull the slide valve 11 out or push it in from the slide valve hole 2503.

[0041] The valve wall of the slide valve 11 has three sets of holes. The first set of holes 11b is a single hole structure with a large axial opening length, which ensures that the slide valve 11 is always connected to the channel 2504 of the pump body 25 during the pushing and pulling process, that is, connected to the outlet cavity 2505 of the gear pair below.

[0042] When the slide valve 11 is pulled out to its full position, the second set of holes 11d connects to the outlet pipe 22 through the channel 2521 of the pump body 25. See the detailed assembly diagram for reference. Figure 5 .like Figure 5 As shown, the first set of holes 11b is always connected to the outlet cavity of the lower gear pair. The medium in the outlet cavity of the lower gear pair is introduced into the outlet pipe 22 through the channel 2521, while the third set of holes 11c and the channel 2515 of the pump body 25 are in the closed state.

[0043] like Figure 4 As shown, when the slide valve 11 is pushed in to its full position, the third set of holes 11c and the channel 2515 of the pump body 25 are connected. For a detailed assembly diagram, please refer to [reference needed]. Figure 6 .like Figure 6 As shown, the first set of holes 11b is always connected to the outlet cavity of the lower gear pair. The medium in the outlet cavity of the lower gear pair is connected to the inlet cavity 2508 of the upper gear pump through channels 2515, 2502 and 2506. The second set of holes 11d and channel 2521 are in the closed state.

[0044] like Figure 4 As shown, when the second group of holes 11d is connected, the third group of holes 11c is not connected; when the third group of holes 11c is connected, the second group of holes 11d is not connected.

[0045] like Figure 7 As shown, the valve stem portion of the valve core 15 is inserted into the valve hole 2510 of the pump body 25. The valve hole 2510 has an axial side hole 2510a leading to the bottom, ensuring a consistent pressure difference between the inside and outside of the valve core 15 within the valve hole 2510, thus guaranteeing smooth reciprocating movement of the valve core 15 within the valve hole 2510. The spring 16 presses the valve surface 15a of the valve core 15 tightly against the valve hole surface 14a of the inlet pipe 14. The valve surface 15a is a conical surface, and the valve hole surface 14a is either a conical surface or a flat surface.

[0046] Figure 7 The gasket 17, which serves as a seal between the pump body 25 and the inlet pipe 14, is also shown and labeled.

[0047] To facilitate the description of the invention, multiple cross-sections were taken from the pump body 25. These cross-sections are either parallel to the axis or perpendicular to the axis. See Figure 8 for details.

[0048] like Figures 8-1 to 8-8 As shown, the pump body 25 has a cuboid structure. The upper gear pair has an inlet cavity 2508, an outlet cavity 2501, a gear cavity 2517, a buffer groove 2516, and an inlet channel 2518. The lower gear pair has an inlet cavity 2507, an outlet cavity 2505, a gear cavity 2513, a buffer groove 2514, and an inlet channel 2512.

[0049] The upper gear pair has an inlet 2508 with a one-way valve port 2510, and an outlet 2501 is connected to the outlet pipe 22 through a pump body port 2509.

[0050] The channel 2521 of the pump body 25 is connected to the outlet pipe 22. When Figure 2 When the slide valve 11 is pulled outward to its position, the second set of holes 11d and the channel 2521 are aligned and connected, and the medium in the outlet cavity 2505 of the lower gear pair enters the outlet pipe 22 through the channel 2521.

[0051] The channels 2515, 2502, and 2506 inside the pump body 25 are connected to the inlet cavity 2508 of the upper gear pair. When Figure 2 When the third set of holes 11c and the channel 2515 inside the pump body are aligned and connected, the medium in the outlet chamber 2505 of the lower gear pair no longer enters the outlet pipe 22 through the channel 2521, but reaches the inlet chamber 2508 of the upper gear pair through the internal channels 2502 and 2506 of the pump body.

[0052] The radial hole 2511 connects the intermediate shaft hole and the inlet cavity 2507 of the lower gear pair, allowing the medium in the intermediate shaft hole to be introduced into the inlet cavity 2507, so that when the shaft 10 rotates in the intermediate shaft hole, the medium can flow and heat dissipation can be achieved.

[0053] The slide valve 11 is housed in the slide valve hole 2503 on the outlet side of the pump body 25. The slide valve hole 2503 is machined with an internal thread hole, which mates with the external thread of the cap 13 to prevent the slide valve 11 from coming out.

[0054] The channel 2520 inside the pump body 25 introduces the medium from the outlet 2505 of the lower gear pair into the end of the slide valve 11, so that the pressure at the front and back of the end of the slide valve 11 is the same, which facilitates the smooth reciprocating movement of the slide valve 11.

[0055] The buffer grooves 2516 and 2514, together with the upper gear pair and the lower gear pair, form a closed chamber. The large oil storage volume of the buffer grooves provides buffering, lubrication and heat dissipation for the operation of the upper and lower gear pairs.

[0056] The inlet channels 2518 and 2512 guide the medium from the upper and lower inlet chambers 2508 and 2507 into the upper and lower gear pump pairs.

[0057] like Figure 9 As shown, the function of mechanical seal 1 is to prevent the medium from leaking to the outside of the pump. The function of shaft retaining ring 2 is to be clamped on shaft 10 to provide axial positioning for mechanical seal 1, so that the dynamic ring seat 1d and the stationary ring seat 1e are disengaged, similar to a shaft shoulder.

[0058] Mechanical seal 1 is a cartridge mechanical seal. Gasket 1b separates the rotating ring seat 1d and the stationary ring seat 1e to prevent them from falling off; screw 1a fixes gasket 1b to the rotating ring seat 1d; set screw 1c is used to lock the rotating ring seat 1d onto the shaft 10.

[0059] When the rotating ring seat 1d and the stationary ring seat 1e of the mechanical seal 1 disengage, the set screw 1c on the rotating ring seat 1d is radially locked onto the shaft 10. The screw 1a and the washer 1b can be removed, or the washer 1b can be folded over the rotating ring seat 1d.

[0060] like Figure 10As shown, the pump cover 3 houses the mechanical seal 1, and the pump cover 3 is also designed with a return channel 3a. The medium in the mechanical seal cavity is introduced into the inlet cavity of the lower gear pump through the return channel 3a and the return channel 2519 of the pump body 25.

[0061] like Figure 11 As shown, the upper bearing 7 and the lower bearing 18 are respectively placed in the pump body holes 2517 and 2513. The shaft holes of the upper bearing 7 and the lower bearing 18 are both eccentric structures, so the upper bearing 7 and the lower bearing 18 will not follow the rotating shaft 10. The upper bearing 7 and the lower bearing 18 are designed with channels 7a, 7b, 18a, and 18b, which are connected to the outlet and buffer grooves 2516 and 2514 on the pump body, respectively.

[0062] like Figure 12 As shown, the rolling bearing 5 is a deep groove ball bearing, which is separated from the upper bearing 7 by an adjusting shim 6, and the rolling bearing is locked on the shaft 10 by a retaining ring 4.

[0063] The internal gear pump in this invention is a linear conjugate internal gear pump. The external gear has a linear tooth profile, and the internal gear ring has a linear conjugate curve tooth profile. It has side inlet and side outlet, and the inlet and outlet flanges are coaxial.

[0064] like Figure 13 As shown in Figure 14, the meshing tooth profiles in a linear conjugate internal gear pump conform to the basic principle of tooth profile meshing: the common normal of the conjugate tooth profiles at the contact point must pass through the instantaneous meshing node. The instantaneous meshing node of the straight line g1 and the linear conjugate curve g2 is the tangent point of the two pitch circles. That is, the tangent point P of the external gear pitch circle r1 and the internal gear ring pitch circle r2.

[0065] Figure 13 The coordinate system for the external gear is X1O1Y1, and the coordinate system for the internal gear ring is X2O2Y2. The vertical axes Y1 and Y2 are collinear, and the horizontal axes X1 and X2 are parallel, with a distance e between them, which is also the center distance e between the external gear and the internal gear ring.

[0066] Figure 13 In this context, C1(x1,y1) is any point on the straight line g1 of the external gear, and C2(x2,y2) is any point on the conjugate curve g2 of the straight line of the internal gear ring.

[0067] Figure 13 The straight line g1 of the external gear intersects the longitudinal axis Y1 at point A, with an included angle β. The line connecting the intersection of straight line g1 and the pitch circle r1 to the circle O1 and the central angle θ of the longitudinal axis Y1 is given. The tooth profile equation of the external gear straight line g1 is given by y1=k The slope is represented by x1+b, where the slope is k=cotβ and the intercept is b= O1A=r1. cosθ+r1 sinθ cotβ.

[0068] Figure 13 Any point C2(x2,y2) on the linear conjugate curve g2 of the internal gear ring can be expressed by the following formula through coordinate transformation: x2=x1 cos(φ1-i12 φ1)-y1 sin(φ1-i12 φ1) + e sin(i12 φ1); y2=x1 sin(φ1-i12 φ1)+y1 cos(φ1-i12 φ1) + e cos(i12) φ1).

[0069] Where i12 is the reduction ratio, i12 = r1 / r2. The turning angle φ1 of straight line g1 is β - arccos((y1) / r2). cosβ+x1 sinβ) / r1)。

[0070] Figure 14 The straight line g1 and the conjugate curve g2 in the equation are derived from... Figure 11 The above formula is programmed and then drawn. The straight line g1 is simple and intuitive, and is relatively easy to use when machining the tooth profile 51 of the external gear. However, the conjugate curve g2 is composed of a series of discrete points and is a slightly convex curve in shape. When machining the tooth profile of the internal gear ring, CNC machine tools or wire cutting methods are usually used, and the specific coordinate points are transmitted before machining.

[0071] The tooth profile of the internal gear ring belongs to the straight conjugate curve g2, which is composed of a set of discrete data points. When machining with CNC machine tools and wire EDM, although interpolation or increasing the number of discrete points can be used to improve machining accuracy, this method is difficult to meet the surface finish that can be achieved by grinding or precision machining, and there is no good way to check the error.

[0072] Figure 15 This is the internal gear ring profile generated using spline smoothing fitting. Specifically, a series of discrete points on the conjugate curve g2 of a straight line are fitted using spline smoothing. The specific stage from the discrete points to the spline curve can be controlled by setting an error, which can be checked by measuring the error in AutoCAD. Mathematically, spline curve fitting typically achieves at least second-order smoothness, meaning the curve is continuous and has continuous second derivatives. This ensures that the internal gear ring profile 921 achieves the expected machining accuracy, smoothness, and surface finish during CNC machine tool processing or wire EDM.

[0073] This invention offers advantages in low-noise transport environments with strict space and weight constraints. The internal gear pump utilizes one or more meshing gear pairs (external gear and internal gear ring) sealed within the pump body, operating through changes in media volume. These meshing gear pairs are the core components of the gear pump. The small center distance and compact structure of the internal gear pairs result in a small size, light weight, and minimal material usage for the internal gear pump. Because the external gear and internal gear ring rotate in the same direction, the relative sliding speed between the tooth profiles is low, leading to less tooth surface wear and a longer service life. Furthermore, the large overlap ratio of the internal gear pairs results in low contact stress between the tooth surfaces, thus ensuring smoother transmission in the internal gear pump.

[0074] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the concept and scope of the present invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A low-noise, variable-flow internal gear pump with a built-in single / double suction switching structure, characterized in that: The pump includes a pump body, an external gear, and an internal gear ring. The pump body has two adjacent chambers, each housing an external gear and an internal gear ring. These, along with upper and lower bearings, form upper and lower gear pairs. The upper and lower gear pairs rotate coaxially, with the direction of rotation matching the rotational speed. Each gear pair has an independent inlet and outlet. The inlet pipe merges the independent inlets into one, and the outlet pipe merges the two independent outlets into one. The pump body also contains a reciprocating slide valve. When the slide valve is pulled outward, it guides the medium from the lower gear pair into the outlet pipe, resulting in a parallel configuration of the upper and lower gear pairs with a double-suction structure, suitable for high-flow-rate conditions. When the slide valve is pushed inward, it guides the medium from the lower gear pair into the inlet of the upper gear pair, closing the check valve. In this configuration, the upper and lower gear pairs are connected in series with a single-suction structure, suitable for low-flow-rate conditions.

2. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 1, characterized in that: The pump body houses two sets of external gears and an internal gear ring, equipped with upper and lower bearings. The shaft holes and outer circles of the upper and lower bearings are eccentric to prevent the bearings from rotating with the shaft. The shaft hole in the middle of the pump body acts as a sliding bearing. The shaft hole in the middle has a radial hole that connects to the inlet cavity of the lower gear pair, guiding the medium in the middle shaft hole into the inlet cavity to form a flow for heat dissipation.

3. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 1, characterized in that: The inlet cavity of the upper gear pair of the pump body is equipped with two one-way valves to ensure that the medium can only flow into the inlet cavity in one direction. The two one-way valves work together with the slide valve to form a single and double suction structure inside the pump body. The slide valve hole on the outlet side of the pump body is equipped with a slide valve that can be pushed and pulled back, which improves the structural foundation for the built-in single and double suction structure.

4. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 1, characterized in that: The slide valve has a reciprocating push-pull structure. The valve wall of the slide valve has three sets of holes. The first set of holes is a single hole structure and is always connected to the outlet cavity of the lower gear pair. The second set of holes connects the outlet cavity and the outlet pipe when the slide valve is pulled out to the end. When the third set of holes is pushed inward, the outlet cavity is connected to the inlet cavity of the upper gear pair through the internal channel; the second and third sets of holes are both parallel double-hole structures with equal flow area.

5. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 4, characterized in that: The radial clearance between the slide valve and the slide valve orifice on one side is 0.02mm~0.06mm, balancing sealing effect and slide valve push-pull speed. To improve the sealing effect of the double orifice, after the double orifice is closed by push-pull, the double orifice of the slide valve and the double orifice of the slide valve are not closely attached to the boundary, but are offset by a certain distance, ensuring better sealing in the closed state and reducing leakage. To improve the push-pull response speed of the slide valve, the pump body is provided with a channel at the top of the slide valve orifice to avoid liquid entrapment causing slide valve jamming.

6. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 4, characterized in that: In addition to the reciprocating push-pull structure, the slide valve also adopts a rotary slide valve structure. The slide valve rotates back and forth around its own axis with a limited range. The first set of holes remains unchanged, while the second and third sets of holes are rectangular single-hole structures. The length direction of the single hole is the axis direction of the slide valve, and the width direction is the circumferential direction.

7. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 1, characterized in that: The valve hole of the pump body is provided with an axial side hole to improve the response speed when the check valve is opened and closed.

8. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 1, characterized in that: The one-way valve is a cone valve, a flat valve, or a ball valve.

9. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 1, characterized in that: This gear pump adopts a spur tooth conjugate structure, which reduces oil trapping and flow pulsation. Two external gears and two internal gear rings are used as rotating components. The internal gear rings and external gears also adopt a helical tooth structure, but the axial inclination angle of the helical teeth is limited to not connecting the pump inlet and outlet, which further reduces vibration and noise.

10. The low-noise, variable-flow internal gear pump with built-in single / double suction switching structure according to claim 1, characterized in that: The external gear is a straight line, and the internal gear ring is a straight conjugate tooth profile curve. The straight conjugate tooth profile curve is composed of discrete points, or is composed of multiple spline curves that have been smoothly fitted after error control.

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