Variable speed device and mechanically driven gear pump comprising same

Abstract

The utility model provides a kind of variable speed device and the mechanical drive gear pump containing it, a kind of variable speed device, including shift fork mechanism, first and second driving gear on input shaft, first and second driven gear on output shaft. By shift fork mechanism driven driven gear set or driving gear set axial sliding, realize the switching of two sets of gear pairs: first state, first driving gear and first driven gear mesh, form first speed ratio, second group separates;Second state, second driving gear and second driven gear mesh, form second speed ratio, first group separates. Two groups of different speed ratio, widen the adaptation speed range of power source, avoid gear pump overload or pump oil deficiency, improve system reliability. Shift fork mechanism only drives single group gear (driving or driven), another group is fixed, simple structure and prevent interference, improve the reliability of gear engagement.

Description

Technical Field

[0001] This utility model relates to the field of mechanically driven gear pumps, and in particular to a speed change device and a mechanically driven gear pump including the same. Background Technology

[0002] Gear pumps, as fluid conveying devices, are widely used in hydraulic or lubrication systems in engineering machinery, industrial equipment, and other fields. Their basic principle is that the rotation of a pair of meshing gears within the pump casing creates a volume change, thereby drawing in and discharging fluid.

[0003] Currently, conventional mechanically driven gear pumps typically consist of a pump body, a driving gear, and a driven gear. The driving gear is mounted on the input shaft of the power source, while the driven gear is mounted on the output shaft of the gear pump. The driving gear meshes with the driven gear at a fixed speed ratio, driving the driven gear to rotate and thus powering the gear pump.

[0004] To ensure the proper functioning of gear pumps, on the one hand, in existing fixed-ratio structures, the input speed of the power source is often limited to a fixed and narrow range. However, in practical applications, the input speed of the power source is not constant and often fluctuates within a wider range depending on the operating conditions. This can lead to the gear pump's speed being lower than the design allowable range, resulting in inability to pump oil normally or insufficient oil volume, failing to meet system requirements, or exceeding the design allowable range, causing gear pump overload, abnormal bearing wear, excessive stress leading to breakage, or cavitation within the pump, affecting the stability and lifespan of the entire system. On the other hand, some gear pumps with multiple speed ratios have sliding gears and other gears in fixed positions. A shifting fork mechanism is used to engage the sliding gear with other gears of different speed ratios to achieve switching between them. However, frequent sliding and engagement of the sliding gear with different gears easily leads to wear on the sliding gear and the shifting fork mechanism, affecting their service life. Furthermore, the sliding gear requires machining multiple tooth segments to engage with different gears, making the process complex and difficult to manufacture. Utility Model Content

[0005] The technical problem this utility model aims to solve is to overcome the limitations of existing technologies where, under a fixed speed ratio structure, the input speed of the power source is often limited to a fixed and narrow range. In actual application scenarios, the input speed of the power source is not constant and often needs to fluctuate within a wide range depending on the operating conditions. This may result in the gear pump speed being lower than the design allowable range, failing to pump oil normally or pumping insufficient oil, failing to meet system requirements, or exceeding the design allowable range, leading to gear pump overload, abnormal bearing wear, or excessive stress causing breakage, or cavitation in the pump, affecting the stability and lifespan of the entire system. This utility model provides a speed change device and a mechanically driven gear pump containing the same.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution:

[0007] A speed change device includes a shift fork mechanism, a first driving gear and a second driving gear disposed on the input shaft of a power source, and a first driven gear and a second driven gear disposed on the output shaft of a gear pump, characterized in that the speed change device includes a first state or a second state.

[0008] In the first state, the shift fork mechanism drives the first driven gear and the second driven gear to slide along the axial direction of the output shaft, and the first driving gear and the second driving gear are fixed to the input shaft; or the shift fork mechanism drives the first driving gear and the second driving gear to slide along the axial direction of the input shaft, and the first driven gear and the second driven gear are fixed to the output shaft, so that the first driven gear meshes with the first driving gear, and the ratio of the number of teeth of the first driven gear to the number of teeth of the first driving gear is configured as a first speed ratio, and the second driven gear disengages from the second driving gear.

[0009] In the second state, the shift fork mechanism drives the first driven gear and the second driven gear to slide along the axial direction of the output shaft, and the first driving gear and the second driving gear are fixed to the input shaft; or the shift fork mechanism drives the first driving gear and the second driving gear to slide along the axial direction of the input shaft, and the first driven gear and the second driven gear are fixed to the output shaft, so that the second driven gear meshes with the second driving gear, and the ratio of the number of teeth of the second driven gear to the number of teeth of the second driving gear is configured as a second speed ratio, and the first driven gear disengages from the first driving gear.

[0010] The first speed ratio and the second speed ratio are different.

[0011] In this solution, the above-mentioned structural form is adopted, and two independent gear sets are set up, namely the first driving gear and the first driven gear, the second driving gear and the second driven gear. The meshing and disengagement of the two different gear sets form two different speed ratios, which solves the problem of the original fixed speed ratio. When the speed of the power source is too high, it can switch to a high speed ratio, and when the speed of the power source is too low, it can switch to a low speed ratio, thus ensuring the stability of the gear pump system. When the shift fork mechanism drives the first and second driven gears to slide axially along the output shaft, the first and second driving gears are fixed to the input shaft. Alternatively, the shift fork mechanism can drive the first and second driving gears to slide axially along the input shaft, while the first and second driven gears are fixed to the output shaft. On one hand, this allows the shift fork mechanism to drive only one set of driving or driven gears simultaneously, reducing the complexity of the connection between the shift fork mechanism and the driven object. It also eliminates the need for a separate shift fork mechanism, making the structure more compact. On the other hand, driving only one set of driving or driven gears while the other set is fixedly connected prevents the driven gear set from sliding and pushing the driving gear set (or vice versa), which could prevent the target gear pair from fully meshing. This ensures speed ratio switching while improving the reliability of gear meshing. In either the first or second state, one set of driving and driven gears meshes while the other set disengages, preventing simultaneous meshing of both sets and avoiding gear jamming, thus improving the stability of speed ratio switching.

[0012] Preferably, the first distance and the second distance are different, wherein the first distance is the distance between the tooth surfaces of the first driven gear and the second driven gear along the axial direction of the output shaft; the second distance is the distance between the tooth surfaces of the first driving gear and the second driving gear along the axial direction of the input shaft; the input shaft and the output shaft are parallel, and the sum of the tooth surface radii of the first driven gear and the tooth surface radii of the first driving gear is equal to the sum of the tooth surface radii of the second driven gear and the tooth surface radii of the second driving gear.

[0013] In this scheme, the aforementioned structural form is adopted. The different first and second distances ensure that the meshing positions of the two sets of gears along the input or output shaft are staggered, preventing simultaneous meshing and ensuring that the two sets of gears do not interfere with each other. The sum of the tooth surface radii of the two sets of gears is equal, enabling the first driving gear and the first driven gear to mesh, or the second driving gear and the second driven gear to mesh, when the transmission device switches to the first or second state.

[0014] Preferably, both the first driven gear and the second driven gear include a driven body, and both the first driving gear and the second driving gear include a driving body. The tooth surface is disposed on the outer peripheral surface of the driven body and the driving body. The thickness of the driven body is the same as the thickness of the driving body. The distance between the two driven bodies along the axial direction of the output shaft is different from the distance between the two driving bodies along the axial direction of the input shaft, or the distance between the two driven bodies along the axial direction of the output shaft is the same as the distance between the two driving bodies along the axial direction of the input shaft, and the thickness of the driven body is different from the thickness of the driving body.

[0015] In this solution, using the aforementioned structural form, if the thickness of the gear body remains the same, the tooth surface spacing is controlled by changing the distance between the gear bodies. This requires only adjusting the position of the gear bodies on the shaft to achieve the change in tooth surface spacing. All gear bodies can be machined using standardized processes, eliminating the need for custom-made gear bodies and reducing manufacturing costs. If the gear body thickness is changed while maintaining the same axial spacing, then there is no need to adjust the gear position during installation, improving assembly efficiency.

[0016] Preferably, when the shift fork mechanism drives the first driven gear and the second driven gear to slide along the axial direction of the output shaft, the output shaft is slidably connected to the connecting member, one end of the connecting member along the axial direction of the output shaft is connected to the first driven gear, and the other end of the connecting member along the axial direction of the output shaft is connected to the second driven gear; or when the shift fork mechanism drives the first driving gear and the second driving gear to slide along the axial direction of the input shaft, the input shaft is slidably connected to the connecting member, one end of the connecting member along the axial direction of the input shaft is connected to the first driving gear, and the other end of the connecting member along the axial direction of the input shaft is connected to the second driving gear.

[0017] In this solution, the above-mentioned structural form is adopted, and the two ends of the connector are respectively connected to the driven gear on the output shaft or to the driving gear on the input shaft, so as to ensure that when the shift fork mechanism drives one of the first driven gear and the second driven gear, the other can slide synchronously.

[0018] Preferably, the shift fork mechanism is disposed between the first driven gear and the second driven gear, or the shift fork mechanism is disposed between the first driving gear and the second driving gear.

[0019] In this solution, the above-mentioned structural form is adopted, and the shift fork mechanism is set between the first driven gear and the second driven gear, or the shift fork mechanism is set between the first driving gear and the second driving gear, so that when the two sets of gears switch to different states, the sliding stroke of the shift fork mechanism driving the gear set is reduced, thereby improving the switching rate of different states.

[0020] Preferably, the shift fork mechanism is disposed on the side of the output shaft opposite to the input shaft, or the shift fork mechanism is disposed on the side of the input shaft opposite to the output shaft.

[0021] In this solution, the above-mentioned structural form is adopted. When the shift fork mechanism drives the first driving gear and the second driving gear on the input shaft, the shift fork mechanism is located on the side of the input shaft away from the output shaft. Alternatively, when the shift fork mechanism drives the first driven gear and the second driven gear on the output shaft, the shift fork mechanism is located on the side of the output shaft away from the input shaft. This ensures that when switching between different states, the shift fork mechanism is always located on the non-meshing side of the gear, avoiding interference between the shift fork mechanism and the meshing area of ​​the gear set when switching between different states, and improving the reliability of the shift fork mechanism.

[0022] Preferably, the shift fork mechanism includes a drive unit and a shift fork component, one end of the shift fork component is disposed between the first driven gear and the second driven gear, and the other end of the shift fork component is connected to the drive unit; or one end of the shift fork component is disposed between the first driving gear and the second driving gear, and the other end of the shift fork component is connected to the drive unit.

[0023] In this solution, the above-mentioned structural form is adopted. The shift fork mechanism adopts a split design of the drive unit and the shift fork component, which allows the same drive unit to be matched with different models of shift fork components and to be adapted to passive or active gears. The modular design can more flexibly adapt to different needs. When the shift fork component wears out, there is no need to replace the entire drive unit, reducing maintenance costs.

[0024] Preferably, the end of the shift fork component facing the first driven gear and the second driven gear is provided with a rolling element, or the end of the shift fork component facing the first driving gear and the second driving gear is provided with a rolling element.

[0025] In this solution, the above-mentioned structural form is adopted, and a rolling element is provided at the end of the shift fork component, so that when the shift fork component drives the driving gear or the driven gear, the contact between the shift fork component and the side of the gear is a rolling contact, which avoids the gear side from being scratched when the shift fork component pushes the gear side, reduces the wear of the gear side and the shift fork component, and extends the service life of the gear and the shift fork component.

[0026] Preferably, the design range of the first speed ratio and the second speed ratio is 0.1-10.

[0027] In this scheme, the above-mentioned structural form is adopted so that when the allowable speed range of the gear pump is fixed, the design range of the first speed ratio and the second speed ratio is 0.1-10, which greatly expands the allowable input speed range of the power source. Regardless of whether the speed of the power source is too high or too low, it can be adjusted by a specific speed ratio, and the gear pump is in the designed operating speed range, ensuring the reliable and efficient operation of the gear pump.

[0028] A mechanically driven gear pump, characterized in that it includes a speed-changing device as described above.

[0029] The positive and progressive effects of this utility model are as follows:

[0030] The system is configured with a first driving gear and a first driven gear, a second driving gear and a second driven gear to form two independent gear sets. By meshing and disengaging the two different gear sets, two different speed ratios are formed, which solves the problem of the original fixed speed ratio and increases the allowable speed range of the power source. When the speed of the power source is too high, it can switch to a high speed ratio, and when the speed of the power source is too low, it can switch to a low speed ratio, thus ensuring the stability of the gear pump system. When the shift fork mechanism drives the first and second driven gears to slide axially along the output shaft, the first and second driving gears are fixed to the input shaft. Alternatively, the shift fork mechanism can drive the first and second driving gears to slide axially along the input shaft, while the first and second driven gears are fixed to the output shaft. On one hand, this allows the shift fork mechanism to drive only one set of driving or driven gears simultaneously, reducing the complexity of the connection between the shift fork mechanism and the driven object. It also eliminates the need for a separate shift fork mechanism, making the structure more compact. On the other hand, driving only one set of driving or driven gears while the other set is fixedly connected prevents the driven gear set from sliding and pushing the driving gear set (or vice versa), which could prevent the target gear pair from fully meshing. This ensures speed ratio switching while improving the reliability of gear meshing. In either the first or second state, one set of driving and driven gears meshes while the other set disengages, preventing simultaneous meshing of both sets and avoiding gear jamming, thus improving the stability of speed ratio switching. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the first state of the speed change device according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the second state of the speed change device according to an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] Shift fork mechanism 1

[0035] Input axis 2

[0036] First driving gear 21

[0037] Active entity 211

[0038] Second drive gear 22

[0039] Output shaft 3

[0040] First passive gear 31

[0041] Passive Body 311

[0042] Second passive gear 32

[0043] Gear pump 4

[0044] First State 5

[0045] Second state 6

[0046] Tooth surface 7

[0047] Connector 8 Detailed Implementation

[0048] The present invention will be described more clearly and completely below with reference to the accompanying drawings, using a preferred embodiment.

[0049] This embodiment provides a mechanically driven gear pump 4, which includes a speed change device.

[0050] like Figures 1 to 2 As shown, the transmission device includes a shift fork mechanism 1, a first driving gear 21 and a second driving gear 22 disposed on the input shaft 2 of the power source, and a first driven gear 31 and a second driven gear 32 disposed on the output shaft 3 of the gear pump 4. The transmission device includes a first state 5 or a second state 6.

[0051] In the first state 5, the first driven gear 31 and the second driven gear 32 are sleeved on the output shaft 3. The inner surfaces of the first driven gear 31 and the second driven gear 32 are slidably connected to the outer surface of the output shaft 3. The shift fork mechanism 1 drives the first driven gear 31 and the second driven gear 32 to slide along the axial direction of the output shaft 3. The first driving gear 21 and the second driving gear 22 are fixed to the input shaft 2 so that the first driven gear 31 meshes with the first driving gear 21. The ratio of the number of teeth of the first driven gear 31 to the number of teeth of the first driving gear 21 is configured as the first speed ratio. The second driven gear 32 disengages from the second driving gear 22.

[0052] In the second state 6, the first driven gear 31 and the second driven gear 32 are sleeved on the output shaft 3. The inner surfaces of the first driven gear 31 and the second driven gear 32 are slidably connected to the outer surface of the output shaft 3. The shift fork mechanism 1 drives the first driven gear 31 and the second driven gear 32 to slide along the axial direction of the output shaft 3. The first driving gear 21 and the second driving gear 22 are fixed to the input shaft 2 so that the second driven gear 32 meshes with the second driving gear 22. The ratio of the number of teeth of the second driven gear 32 to the number of teeth of the second driving gear 22 is configured as the second speed ratio. The first driven gear 31 disengages from the first driving gear 21. The first speed ratio and the second speed ratio are different.

[0053] In this embodiment, the first driving gear 21 and the first driven gear 31, the second driving gear 22 and the second driven gear 32 are set to form two independent gear sets. The meshing and disengagement of the two different gear sets form two different speed ratios, which solves the problem of the original fixed speed ratio and improves the allowable speed range of the power source. When the speed of the power source is too high, it can switch to a high speed ratio, and when the speed of the power source is too low, it can switch to a low speed ratio, thus ensuring the stability of the gear pump 4 system. When the shift fork mechanism 1 drives the first driven gear 31 and the second driven gear 32 to slide along the axial direction of the output shaft 3, the first driving gear 21 and the second driving gear 22 are fixed to the input shaft 2. Alternatively, when the shift fork mechanism 1 drives the first driving gear 21 and the second driving gear 22 to slide along the axial direction of the input shaft 2, the first driven gear 31 and the second driven gear 32 are fixed to the output shaft 3. On the one hand, this allows the shift fork mechanism 1 to drive only one set of driving gears or driven gears, without driving them simultaneously, reducing the complexity of the connection between the shift fork mechanism 1 and the driven object. At the same time, there is no need to set up another shift fork mechanism 1, making the structure more compact. On the other hand, driving only one set of driving gears or driven gears, with the other set fixedly connected, can prevent the driven gear set from moving (or vice versa) when the driven gear set slides, causing the target gear pair to fail to mesh completely. This improves the reliability of gear meshing while ensuring speed ratio switching. In either state 5 or state 6, one set of driving gears and driven gears meshes while the other set disengages, preventing both sets of driving gears and driven gears from meshing simultaneously. This prevents gear jamming caused by simultaneous meshing and improves the stability of speed ratio switching.

[0054] In other embodiments, the first driving gear 21 and the second driving gear 22 are sleeved on the input shaft 2, and the inner surfaces of the first driving gear 21 and the second driving gear 22 are slidably connected to the outer surface of the input shaft 2. The shift fork mechanism 1 drives the first driving gear 21 and the second driving gear 22 to slide along the axial direction of the input shaft 2. The first driven gear 31 and the second driven gear 32 are fixed to the output shaft 3.

[0055] The first distance and the second distance are different. The first distance is the distance between the tooth surface 7 of the first driven gear 31 and the tooth surface 7 of the second driven gear 32 along the axial direction of the output shaft 3. The second distance is the distance between the tooth surface 7 of the first driving gear 21 and the tooth surface 7 of the second driving gear 22 along the axial direction of the input shaft 2. The input shaft 2 and the output shaft 3 are parallel, and the sum of the radius of the tooth surface 7 of the first driven gear 31 and the radius of the tooth surface 7 of the first driving gear 21 is equal to the sum of the radius of the tooth surface 7 of the second driven gear 32 and the radius of the tooth surface 7 of the second driving gear 22.

[0056] like Figure 1 and Figure 2 As shown, in this embodiment, the gear is a perfect circle, and the radius of the tooth surface 7 is the distance between the tooth surface 7 and the center of the gear. In other embodiments, the radius of the tooth surface 7 may have other boundary shapes, which are not limited here.

[0057] When the shift fork mechanism 1 drives the first driven gear 31 and the second driven gear 32 to slide along the axial direction of the output shaft 3, the output shaft 3 is slidably connected to the connecting member 8. One end of the connecting member 8 along the axial direction of the output shaft 3 is connected to the first driven gear 31, and the other end of the connecting member 8 along the axial direction of the output shaft 3 is connected to the second driven gear 32.

[0058] like Figure 1 and Figure 2 As shown, in this embodiment, the connector 8 is a cylindrical sleeve that is slidably fitted onto the output shaft 3. The two ends of the sleeve are welded and fixed to the first driven gear 31 and the second driven gear 32, respectively. The gear pump 4 is fixedly connected to the speed change device by bolts.

[0059] In other embodiments, when the shift fork mechanism 1 drives the first drive gear 21 and the second drive gear 22 to slide along the axial direction of the input shaft 2, the input shaft 2 is slidably connected to the connector 8. One end of the connector 8 along the axial direction of the input shaft 2 is connected to the first drive gear 21, and the other end of the connector 8 along the axial direction of the input shaft 2 is connected to the second drive gear 22. The sleeve is slidably sleeved on the input shaft 2, and both ends of the sleeve are welded and fixed to the first drive gear 21 and the second drive gear 22, respectively.

[0060] like Figure 1 and Figure 2 As shown, in this embodiment, the shift fork mechanism 1 is disposed on the side of the output shaft 3 opposite to the input shaft 2. In other embodiments, the shift fork mechanism 1 is disposed on the side of the input shaft 2 opposite to the output shaft 3.

[0061] The design range for the first and second speed ratios is 0.1-10.

[0062] like Figure 1 and Figure 2As shown, in this embodiment, the first speed ratio of the first state 5 is 2, the second speed ratio of the second state 6 is 0.5, the gear pump 4 is designed to allow a speed range of 200-1800 rpm, the power source is allowed to input a speed range of 100-3600 rpm, and the power source is an electric motor or a diesel engine.

[0063] The first driven gear 31 and the second driven gear 32 both include a driven body 311, and the first driving gear 21 and the second driving gear 22 both include a driving body 211. The tooth surface 7 is disposed on the outer peripheral surface of the driven body 311 and the driving body 211. The thickness of the driven body 311 is the same as the thickness of the driving body 211. The distance between the two driven bodies 311 along the axial direction of the output shaft 3 is different from the distance between the two driving bodies 211 along the axial direction of the input shaft 2.

[0064] like Figure 1 and Figure 2 As shown, in this embodiment, the width of the tooth surface 7, the thickness of the active body 211 and the thickness of the passive body 311 are the same, and the distance between the two passive bodies 311 along the axis of the output shaft 3 is different from the distance between the two active bodies 211 along the axis of the input shaft 2.

[0065] In other embodiments, the distance between the two passive bodies 311 along the axis of the output shaft 3 is the same as the distance between the two active bodies 211 along the axis of the input shaft 2, and the thickness of the active body 211 is different from the thickness of the passive body 311.

[0066] like Figure 1 and Figure 2 As shown, in this embodiment, the shift fork mechanism 1 is disposed between the first driven gear 31 and the second driven gear 32. In other embodiments, the shift fork mechanism 1 may be disposed between the first driving gear 21 and the second driving gear 22.

[0067] The shift fork mechanism 1 includes a drive unit and a shift fork component. One end of the shift fork component is disposed between the first driven gear 31 and the second driven gear 32, and the other end of the shift fork component is connected to the drive unit.

[0068] In this embodiment, the drive component and the shift fork component are not shown in the drawings. The drive component can be manually driven or motor driven. In other embodiments, one end of the shift fork component is disposed between the first drive gear 21 and the second drive gear 22, and the other end of the shift fork component is connected to the drive unit. The drive component can be manually driven or motor driven.

[0069] In this embodiment, a rolling element is provided at the end of the shift fork component facing the first driven gear 31 and the second driven gear 32. In other embodiments, a rolling element is provided at the end of the shift fork component facing the first driving gear 21 and the second driving gear 22; and an arc surface adapted to the side of the passive body 311 or the driving body 211 is provided at the end of the shift fork component facing the passive body 311 or the driving body 211.

[0070] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. A speed change device, comprising a shift fork mechanism, a first driving gear and a second driving gear disposed on the input shaft of a power source, and a first driven gear and a second driven gear disposed on the output shaft of a gear pump, characterized in that, The speed change device includes a first state or a second state; In the first state, the shift fork mechanism drives the first driven gear and the second driven gear to slide along the axial direction of the output shaft, and the first driving gear and the second driving gear are fixed to the input shaft; or the shift fork mechanism drives the first driving gear and the second driving gear to slide along the axial direction of the input shaft, and the first driven gear and the second driven gear are fixed to the output shaft, so that the first driven gear meshes with the first driving gear, and the ratio of the number of teeth of the first driven gear to the number of teeth of the first driving gear is configured as a first speed ratio, and the second driven gear disengages from the second driving gear. In the second state, the shift fork mechanism drives the first driven gear and the second driven gear to slide along the axial direction of the output shaft, and the first driving gear and the second driving gear are fixed to the input shaft; or the shift fork mechanism drives the first driving gear and the second driving gear to slide along the axial direction of the input shaft, and the first driven gear and the second driven gear are fixed to the output shaft, so that the second driven gear meshes with the second driving gear, and the ratio of the number of teeth of the second driven gear to the number of teeth of the second driving gear is configured as a second speed ratio, and the first driven gear disengages from the first driving gear. The first speed ratio and the second speed ratio are different.

2. The speed change device as described in claim 1, characterized in that, The first distance and the second distance are different. The first distance is the distance between the tooth surfaces of the first driven gear and the second driven gear along the axial direction of the output shaft; the second distance is the distance between the tooth surfaces of the first driving gear and the second driving gear along the axial direction of the input shaft. The input shaft and the output shaft are parallel, and the sum of the tooth surface radius of the first driven gear and the tooth surface radius of the first driving gear is equal to the sum of the tooth surface radius of the second driven gear and the tooth surface radius of the second driving gear.

3. The speed change device as described in claim 2, characterized in that, Both the first driven gear and the second driven gear include a driven body, and both the first driving gear and the second driving gear include a driving body. The tooth surface is disposed on the outer peripheral surface of the driven body and the driving body. The thickness of the driven body is the same as the thickness of the driving body. The distance between the two driven bodies along the axial direction of the output shaft is different from the distance between the two driving bodies along the axial direction of the input shaft, or the distance between the two driven bodies along the axial direction of the output shaft is the same as the distance between the two driving bodies along the axial direction of the input shaft. The thickness of the driven body is different from the thickness of the driving body.

4. The speed change device as described in claim 1, characterized in that, When the shift fork mechanism drives the first driven gear and the second driven gear to slide along the axial direction of the output shaft, the output shaft is slidably connected to the connecting member. One end of the connecting member along the axial direction of the output shaft is connected to the first driven gear, and the other end of the connecting member along the axial direction of the output shaft is connected to the second driven gear. Alternatively, when the shift fork mechanism drives the first drive gear and the second drive gear to slide along the axial direction of the input shaft, the input shaft is slidably connected to the connecting member, one end of the connecting member along the axial direction of the input shaft is connected to the first drive gear, and the other end of the connecting member along the axial direction of the input shaft is connected to the second drive gear.

5. The speed change device as described in claim 4, characterized in that, The shift fork mechanism is disposed between the first driven gear and the second driven gear, or the shift fork mechanism is disposed between the first driving gear and the second driving gear.

6. The speed change device as described in claim 1, characterized in that, The shift fork mechanism is located on the side of the output shaft opposite to the input shaft, or the shift fork mechanism is located on the side of the input shaft opposite to the output shaft.

7. The speed change device as described in claim 5, characterized in that, The shift fork mechanism includes a drive unit and a shift fork component; One end of the shift fork component is disposed between the first driven gear and the second driven gear, and the other end of the shift fork component is connected to the drive unit; Alternatively, one end of the shift fork component may be disposed between the first drive gear and the second drive gear, and the other end of the shift fork component may be connected to the drive unit.

8. The speed change device as described in claim 7, characterized in that, The shift fork component has a rolling element at the end facing the first driven gear and the second driven gear, or the shift fork component has a rolling element at the end facing the first driving gear and the second driving gear.

9. The speed change device as described in claim 1, characterized in that, The design range for the first speed ratio and the second speed ratio is 0.1-10.

10. A mechanically driven gear pump, characterized in that, It includes the speed change device as described in any one of claims 1-9.

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