A variable gear pump

Abstract

The present invention discloses a variable gear pump, which includes a pump body, a pump cover, a driving shaft, a driven shaft and a gear pair. The gear pair includes a set of fixed-displacement gear pairs and several sets of variable gear pairs. The fixed-displacement gear pair consists of two meshing plain-hole gears, and each set of variable gear pairs consists of two meshing spline-hole gears. The spline shaft holes of all spline-hole gears are tapered holes that are larger at the top and smaller at the bottom. The driving shaft and the driven shaft are both composite shafts, and each composite shaft is composed of a fixed shaft, a movable shaft, an upper sleeve, a lower sleeve and a spring assembly. The fixed shafts of the two composite shafts are fixedly connected to the plain-hole gears, and their function is to serve as a fixed-displacement pump and also the minimum flow rate of this oil pump. Then, by establishing or disconnecting the connection between the movable shaft and the spline-hole gears, the variability of the flow rate is achieved. When the movable shaft is connected to all spline-hole gears, it is the maximum flow rate of this oil pump.

Description

Technical Field

[0001] The present invention belongs to the technical field of gear pumps, and particularly relates to a variable displacement gear pump. Background Art

[0002] The oil pump is an important component of the lubrication system. Its function is to continuously and forcibly supply oil to each friction surface, reduce the friction between components, and enable the engine to work safely and reliably. The oil pump is directly driven by the engine. With the increase in the engine speed, the oil supply of the traditional oil pump almost linearly increases. At high speeds, the traditional oil pump outputs excess flow, and the excess oil must be drained through a pressure relief valve, which is equivalent to wasting the engine's power consumption.

[0003] The traditional oil pump cannot meet the ideal design requirements, while the variable displacement oil pump can meet the ideal requirements. From relevant foreign research reports, the variable displacement oil pump can generally reduce the fuel consumption of vehicle engines by 0.5% - 2%. Especially for engines operating under high-speed conditions for a long time, using a variable displacement oil pump can reduce fuel consumption by 3%.

[0004] In the automotive field, due to the advantages of simple structure, small size, light weight, reliable operation, strong anti-pollution ability, and easy maintenance of gear pumps, they are widely used. With the increasingly strict requirements for energy conservation and emission reduction, traditional gear pumps can no longer meet the needs of future society. Therefore, it is urgent to develop a new gear pump system - variable displacement gear pump.

[0005] The current methods for realizing variable flow in variable displacement gear pumps mainly include: changing the axial meshing length of the gears, changing the center distance of gear meshing, sliding of steel sheets between limit slots (upper and lower limit slots are opened from the tooth root to the tooth space), and multiple gear meshing (changing the gear mating shape or controlling the on-off relationship between the oil suction chamber and the oil discharge chamber surplus outlet).

[0006] The variable displacement gear pumps disclosed in Chinese Patent Publication Nos. CN106989013A, CN105782019A, CN105041639A, etc. change the axial meshing length of the gears through a stretching mechanism, a gear sliding mechanism along a keyway, a disc spring, etc. to achieve variable displacement of the gear pump. Although the above patents achieve variable displacement of the gear pump, they will also waste too much power of the engine and are not conducive to improving the working efficiency of the engine.

[0007] The variable displacement gear pumps disclosed in Chinese Patent Publication Nos. CN107061261A, CN106246536A, etc. achieve the purpose of controlling variables by changing the center distance of gear meshing or changing the movement of steel sheets between gears. Although the above patents achieve variable displacement of the gear pump, it is difficult to achieve relatively linear control of the flow output of the gear pump.

[0008] Variable gear pumps such as those disclosed in Chinese Patent Publication Nos. CN112879281A and CN112855527A achieve variable displacement by controlling the engagement of multiple gears (changing the gear mating shape or controlling the on-off relationship between the oil suction chamber and the oil pressure chamber and the outlet). Although the above patents achieve variable displacement of the gear pump, due to the need for multiple sets of gears to engage, the volume of the pump will increase, and the manufacturing cost of the pump will also increase sharply. Summary of the Invention

[0009] The object of the present invention is to provide a variable gear pump in view of the deficiencies of the prior art, which can quickly and accurately control the output flow rate to meet the flow rate requirements of the engine under various working conditions.

[0010] To achieve the above object, the technical solution of the present invention is: a variable gear pump, comprising a pump body, a pump cover, a driving shaft, a driven shaft and a gear pair. The gear pair includes a set of fixed-displacement gear pairs and several sets of variable-displacement gear pairs. The fixed-displacement gear pair consists of two smooth-hole gears that mesh with each other. Each set of variable-displacement gear pairs consists of two splined-hole gears that mesh with each other. The splined shaft holes of all splined-hole gears are tapered holes that are larger at the top and smaller at the bottom; both the driving shaft and the driven shaft are combined shafts, and each combined shaft is composed of a fixed shaft, a moving shaft, an upper sleeve, a lower sleeve and a spring assembly. The moving shaft is a hollow splined shaft, and the moving shaft and the spring are movably sleeved on the fixed shaft. The upper sleeve and the lower sleeve are respectively fixedly arranged at both ends of the fixed shaft; there is an annular sealing cavity between the upper sleeve and the fixed shaft that can accommodate the moving shaft, and the inner wall of the upper sleeve is provided with internal splines that cooperate with the moving shaft. There is an annular cavity between the lower sleeve and the fixed shaft that can accommodate the spring; a smooth-hole gear is fixedly installed on each upper sleeve of the two combined shafts, and the same number of splined-hole gears are sleeved on the fixed shafts of the two combined shafts. The minimum inner diameter of the tapered holes of all splined-hole gears is larger than the outer diameter of the spring; the lower end surface of the spring abuts against the inner bottom surface of the lower sleeve, and the upper end of the spring passes through the tapered holes of multiple splined-hole gears and its upper end surface is in contact and cooperation with the lower end surface of the moving shaft. The pre-tightening force of the spring can completely push the moving shaft into the annular sealing cavity between the upper sleeve and the fixed shaft; an annular groove is provided on the outer peripheral surface of the upper part of the upper sleeve, and a plurality of radial through holes communicating with the annular sealing cavity are provided in the annular groove; the part of the upper sleeve provided with the annular groove is installed in the shaft hole of the pump cover, and a hydraulic oil passage communicating with the annular groove of the upper sleeve is provided on the pump cover; when the hydraulic oil from the hydraulic mechanism passes through the hydraulic oil passage provided on the pump cover and then flows into the annular sealing cavity of the upper sleeve through the annular groove and the radial through holes, the hydraulic oil can exert a downward pressure on the upper end surface of the moving shaft, causing the moving shaft to overcome the pre-tightening force of the spring and insert downward into the tapered holes of the splined-hole gears.

[0011] In one embodiment, a rotary joint is installed in each of the two shaft holes of the pump cover. Each of the two rotary joints is provided with a plurality of radial through holes. The hydraulic flow channels on the pump cover include a main flow channel, two sub-flow channels and two annular flow channels. Each of the main flow channel and the two annular flow channels is communicated through a sub-flow channel. The two annular flow channels are respectively located on the inner walls of the two shaft holes and correspond to the radial through holes of the rotary joints. The parts of the two upper sleeves with annular grooves are installed in the rotary joints. The hydraulic oil flows from the hydraulic drive device through the hydraulic oil channel of the pump cover into the rotary joint, and then enters the annular sealing cavity through the radial through holes of the upper sleeve. By quantifying the displacement of the piston rod of the oil cylinder in the hydraulic drive device, the axial displacement of the two moving shafts can be controlled.

[0012] In one embodiment, the upper sleeves of the two combined shafts and the upper ends of the fixed shafts are integrally formed, and the lower sleeves are fixed to the lower ends of the fixed shafts by screws.

[0013] When the moving shafts of the two combined shafts are completely contracted into the annular sealing cavity of the upper sleeve under the pre-tightening force of the spring, at this time, the driving shaft can only drive the fixed displacement gear pair to rotate and do work, so that the oil pump outputs the minimum flow rate. Only when the hydraulic mechanism drives the hydraulic oil to push the two moving shafts downward axially from above, so that the two moving shafts are inserted into the tapered holes of the spline hole gears to form spline connections, can one or more variable gear pairs be driven to rotate and do work, thereby gradually increasing the output flow rate of the oil pump. Until the two moving shafts form spline connections with all the spline hole gears, the oil pump outputs the maximum flow rate.

[0014] Compared with the prior art, the variable gear pump of the present invention realizes the change of flow rate by controlling the number of groups of meshing gears, so as to meet the flow rate requirements of the engine under different working conditions. Specifically, by controlling the axial displacement of the moving shafts of the driving shaft and the driven shaft, it is determined how many groups of gears are in the working state and how many groups of gears are in the non-working state. Therefore, it has the characteristics of high efficiency and energy saving. By calibrating the relationship between the displacement of the piston rod of the oil cylinder in the hydraulic mechanism, the moving amount of the moving shaft and the pump outlet flow rate under each working condition, the gear pump can quickly and accurately control the output flow rate according to the change of the engine speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic cross-sectional structure diagram of the gear pump in the minimum displacement state in the embodiment of the present invention;

[0016] Figure 2 is Figure 1 a partial enlarged view of part B in

[0017] Figure 3 is Figure 1 a partial enlarged view of part C in

[0018] Figure 4Schematic cross-sectional structure diagram of the gear pump in the maximum displacement in the embodiment of the present invention;

[0019] Figure 5 is Figure 4 Partial enlarged view of part B in;

[0020] Figure 6 is Figure 4 Partial enlarged view of part C in;

[0021] Figure 7 Schematic internal structure diagram of the gear pump after removing the pump body and pump cover in the embodiment of the present invention;

[0022] Figure 8 Schematic structure diagram of the driving shaft and the driven shaft in the embodiment of the present invention;

[0023] Figure 9 is Figure 8 Schematic structure diagram after removing the spring and the lower sleeve;

[0024] Figure 10 is Figure 8 Schematic structure diagram after removing the upper sleeve and the fixed shaft;

[0025] Figure 11 Schematic three-dimensional structure diagram of the driving shaft and the driven shaft after installing the pump cover in the embodiment of the present invention;

[0026] Figure 12 Schematic installation structure diagram between the driving shaft and the driven shaft and the shaft hole of the pump cover in the embodiment of the present invention;

[0027] Reference numerals are:

[0028] 1 - pump cover 1a - main flow channel 1b - sub-flow channel

[0029] 1c - annular flow channel 2 - pump body 3 - screw

[0030] 4 - rotary joint 5 - smooth hole gear 6 - spline hole gear

[0031] 7 - fixed shaft 8 - moving shaft 9 - spring

[0032] 10 - upper sleeve 11 - lower sleeve 10a - annular sealing cavity

[0033] 10b - annular groove A - driving shaft D - driven shaft. Detailed implementation manners

[0034] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with the embodiments and the drawings. The content mentioned in the implementation manners does not limit the present invention.

[0035] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0036] In the description of the present invention, it should be noted that unless otherwise specified and defined, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two elements. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0037] As Figures 1 to 12 shown, a variable gear pump includes a pump cover 1, a pump body 2, a driving shaft A, a driven shaft D, and a gear pair. The gear pair includes a set of fixed-displacement gear pairs and five sets of stacked variable gear pairs. The fixed-displacement gear pair consists of two meshing plain-hole gears 5. Each set of variable gear pairs consists of two meshing spline-hole gears 6. The spline shaft holes of all the spline-hole gears 6 are tapered holes that are larger at the top and smaller at the bottom. As Figures 1 to 10 shown, both the driving shaft A and the driven shaft D are composite shafts. Each composite shaft is composed of a fixed shaft 7, a moving shaft 8, an upper sleeve 10, a lower sleeve 11, and a spring 9. The moving shaft 8 is a hollow spline shaft. The moving shaft 8 and the spring 9 are movably sleeved on the fixed shaft 7. The upper sleeve 10 is integrally formed with the upper end of the fixed shaft 7, and the lower sleeve 11 is fixed to the lower end of the fixed shaft 7 by screws 3. There is an annular sealing cavity 10a between the upper sleeve 10 and the fixed shaft 7 that can accommodate the moving shaft. The inner wall of the upper sleeve 10 is provided with internal splines that cooperate with the moving shaft 7. There is an annular cavity between the lower sleeve 11 and the fixed shaft 7 that can accommodate the spring 9. One plain-hole gear 5 is fixedly installed on each of the upper sleeves 10 of the two composite shafts. Five spline-hole gears 6 are sleeved on each of the fixed shafts 7 of the two composite shafts. The minimum inner diameter of the tapered holes of all the spline-hole gears 6 is larger than the outer diameter of the spring 9. The lower end face of the spring 9 abuts against the inner bottom surface of the lower sleeve 11. The upper end of the spring 9 passes through the tapered holes of multiple spline-hole gears 6 and its upper end face is in contact and cooperation with the lower end face of the moving shaft 8. The pre-tightening force of the spring 9 can completely push the moving shaft 8 into the annular sealing cavity 10a between the upper sleeve 10 and the fixed shaft 7. There is an annular groove 10b on the outer peripheral surface of the upper part of the upper sleeve 10. A plurality of radial through holes communicating with the annular sealing cavity 10a are provided in the annular groove 10b. As Figure 1 、 4, as shown in Fig. 12, a rotary joint 4 is installed in each of the two shaft holes of the pump cover 1. The parts of the two upper sleeves 10 with annular grooves 10b are all installed in the rotary joint 4. The two rotary joints 4 are each provided with a plurality of radial through holes. The pump cover 1 is provided with a hydraulic oil passage communicating with the radial through holes of the rotary joint 4. The hydraulic flow passage includes a main flow passage 1a, two sub-flow passages 1b and two annular flow passages 1c. The main flow passage 1a and the two annular flow passages 1c are each connected through a sub-flow passage 1b. The two annular flow passages 1c are respectively located on the inner walls of the two shaft holes and correspond to the radial through holes of the rotary joint 4. When the hydraulic oil from the hydraulic mechanism passes through the hydraulic oil passage provided on the pump cover 1 and then flows into the annular sealing cavity 10a of the upper sleeve through the annular groove 10b and the radial through hole, the hydraulic oil can exert a downward pressure on the upper end face of the moving shaft 8, so that the moving shaft 8 overcomes the pre-tightening force of the spring 9 and inserts downward into the tapered hole of the spline hole gear 6. By quantifying the displacement of the piston rod of the oil cylinder in the hydraulic drive device, the axial displacement of the two moving shafts 8 can be controlled.

[0038] As Figures 1 to 3 shown, when the moving shafts 8 of the two combined shafts are completely contracted into the annular sealing cavity 10a of the upper sleeve 10 under the pre-tightening force of the spring 9, at this time, the driving shaft A can only drive the fixed displacement gear pair to rotate and do work, so that the oil pump outputs the minimum flow rate. Only when the hydraulic mechanism drives the hydraulic oil to push the two moving shafts 8 downward axially from above, so that the two moving shafts 8 are inserted into the tapered holes of the spline hole gears 6 to form a spline connection, can one or more variable gear pairs be driven to rotate and do work, thereby gradually increasing the output flow rate of the oil pump. As Figures 4 to 6 shown, until the two moving shafts 8 form a spline connection with all the spline hole gears 6, the oil pump outputs the maximum flow rate.

[0039] In this embodiment, the fixed shafts 7 of the two combined shafts are fixedly connected to the plain hole gears 5. Its function is to act as a fixed displacement pump, which is also the minimum flow rate of this oil pump. Then, by establishing a connection or disconnection between the moving shaft 8 and the spline hole gear 6, the variability of the flow rate is realized. When the moving shaft 8 is connected to all the spline hole gears 6, it is the maximum flow rate of this oil pump.

[0040] Since the outer part of the moving shaft 8 adopts a spline structure, and the inner wall of the upper sleeve 10 adopts an internal spline matching with the moving shaft 8, the moving shaft 8 can axially expand and contract along the fixed shaft 7. For the spline hole gear matched with the moving shaft 8, its shaft hole presents a tapered structure with a larger upper part and a smaller lower part in the axial direction. This structure can facilitate the rapid insertion and withdrawal of the moving shaft 8 rotating at high speed into and out of the shaft hole of the spline hole gear 6.

[0041] In order to enable the hydraulic mechanism to accurately control the displacement of the moving shaft, it is necessary to calibrate the relationship between the displacement of the cylinder piston rod in the hydraulic mechanism, the displacement of the moving shaft 8, and the pump outlet flow rate under various operating conditions of the engine, store this data in the control system, and generate different drive signals for different data. During operation, the control system sends drive signals to the hydraulic mechanism according to the engine speed and flow rate requirements, uses hydraulic oil to drive the moving shaft to quickly move to the target position, and realizes the flow rate required by the engine.

[0042] Calibration work of the variable gear pump: According to the engine speed and flow rate requirements, the control system drives the hydraulic mechanism to work. Hydraulic oil enters the annular sealing cavity, thereby pushing the moving shaft 8 downward to generate a quantitative displacement. When the flow rate at the pump outlet meets the requirements, the control system stops driving the hydraulic mechanism. At this time, the stroke sensor converts the displacement of the cylinder piston rod into an electrical signal, and the AD module converts the electrical signal into a digital quantity, thereby establishing a corresponding relationship between the pump flow rate and the piston rod displacement. Then, the next operating condition point is calibrated. After calibration, the calibration data is stored in the control system.

[0043] Working principle of the hydraulic mechanism for accurately controlling the displacement: The control system constantly monitors the engine speed and flow rate. According to the calibrated data, the control system quickly and accurately drives the displacement of the piston rod of the hydraulic mechanism, and then accurately controls the displacement of the moving shaft, so that when the engine operating condition changes, the oil pump can quickly and accurately provide the required target flow rate.

[0044] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the technical solution of the present invention is within the protection scope of the present invention.

[0045] In order to make it more convenient for those of ordinary skill in the art to understand the improvements of the present invention over the prior art, some drawings and descriptions of the present invention have been simplified, and for the sake of clarity, some other elements have also been omitted in this application document. Those of ordinary skill in the art should be aware that these omitted elements may also constitute the content of the present invention.

Claims

1. A variable gear pump, comprising a pump cover (1), a pump body (2), a driving shaft (A), a driven shaft (B) and a gear pair, Characterized in that: The gear pair includes a set of fixed-displacement gear pairs and several sets of variable-displacement gear pairs. The fixed-displacement gear pair is composed of two meshing plain-hole gears (5). Each set of variable-displacement gear pairs is composed of two meshing spline-hole gears (6). The spline shaft holes of all the spline-hole gears (6) are tapered holes with larger diameters at the top and smaller diameters at the bottom; The driving shaft (A) and the driven shaft (B) are both composite shafts. Each composite shaft is composed of a fixed shaft (7), a movable shaft (8), an upper sleeve (10), a lower sleeve (11) and a spring (9). The movable shaft (8) is a hollow spline shaft. The movable shaft (8) and the spring (9) are movably sleeved on the fixed shaft (8). The upper sleeve (10) and the lower sleeve (11) are respectively fixedly arranged at both ends of the fixed shaft (7). There is an annular sealing cavity (10a) capable of accommodating the movable shaft between the upper sleeve (10) and the fixed shaft (7). The inner wall of the upper sleeve (10) is provided with internal splines matching the movable shaft (8). There is an annular cavity capable of accommodating the spring (9) between the lower sleeve (11) and the fixed shaft. One plain-hole gear (5) is fixedly installed on each upper sleeve (10) of the two composite shafts. The same number of spline-hole gears (6) are sleeved on the fixed shafts (7) of the two composite shafts. The minimum inner diameter of the tapered holes of all the spline-hole gears (6) is larger than the outer diameter of the spring (9). The lower end surface of the spring (9) abuts against the inner bottom surface of the lower sleeve (11). After the upper end of the spring (9) passes through the tapered holes of multiple spline-hole gears (6), its upper end surface is in contact and cooperation with the lower end surface of the movable shaft (8). The pre-tightening force of the spring (9) can completely push the movable shaft (8) into the annular sealing cavity (10a) between the upper sleeve (10) and the fixed shaft (7). An annular groove (10b) is provided on the outer peripheral surface of the upper part of the upper sleeve (10). A plurality of radial through holes communicating with the annular sealing cavity (10a) are provided in the annular groove (10b); The part of the upper sleeve (10) provided with the annular groove (10b) is installed in the shaft hole of the pump cover (1). A hydraulic oil passage communicating with the annular groove (10b) of the upper sleeve is provided on the pump cover (1). When the hydraulic oil from the hydraulic mechanism passes through the hydraulic oil passage provided on the pump cover (1) and then flows into the annular sealing cavity (10a) of the upper sleeve through the annular groove (10b) and the radial through holes, the hydraulic oil can apply a downward pressure on the upper end surface of the movable shaft (8), so that the movable shaft (8) overcomes the pre-tightening force of the spring (9) and inserts downward into the tapered hole of the spline-hole gear (6).

2. The variable gear pump and variable method according to claim 1, Characterized in that: One rotary joint (4) is installed in each of the two shaft holes of the pump cover (1). Each of the two rotary joints (4) is provided with a plurality of radial through holes. The hydraulic flow channels on the pump cover (1) include a main flow channel (1a), two sub-flow channels (1b) and two annular flow channels (1c). The main flow channel (1a) is communicated with each of the two annular flow channels (1c) through a sub-flow channel (1b). The two annular flow channels (1c) are respectively located on the inner walls of the two shaft holes and correspond to the radial through holes of the rotary joint (4). The parts of the two upper sleeves (10) provided with annular grooves (10b) are installed in the rotary joint (4). The hydraulic oil from the hydraulic mechanism flows into the rotary joint (4) through the hydraulic oil channel of the pump cover (1), then enters the annular sealing cavity (10a) through the radial through holes of the upper sleeve (10), and the axial displacement of the two moving shafts (8) can be controlled by quantifying the displacement of the piston rod of the oil cylinder in the hydraulic drive device.

3. The variable gear pump according to claim 1 or 2, characterized in that: The upper sleeves (10) of the two combined shafts and the upper end of the fixed shaft (7) are integrally formed, and the lower sleeves (11) are fixed to the lower end of the fixed shaft (7) by screws (3).

4. The variable gear pump according to claim 1 or 2, characterized in that: When the moving shafts (8) of the two combined shafts are completely contracted into the annular sealing cavity (10a) of the upper sleeve under the pre-tightening force of the spring (9), at this time, the driving shaft (A) can only drive the fixed displacement gear pair to rotate and do work, so that the oil pump outputs the minimum flow rate; only when the hydraulic mechanism drives the hydraulic oil to push the two moving shafts (8) downward axially from above, so that the two moving shafts (8) are inserted into the tapered holes of the spline hole gears (6) to form spline connections, can one or more variable gear pairs be driven to rotate and do work, so that the output flow rate of the oil pump increases step by step; until the two moving shafts (8) form spline connections with all the spline hole gears (6), the oil pump outputs the maximum flow rate.

5. The variable gear pump according to claim 1 or 2, characterized in that: The gear pair includes a set of fixed displacement gear pairs and five sets of variable gear pairs stacked together.

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