Hydraulic mechanical continuously variable transmission

Abstract

The utility model discloses a hydraulic mechanical continuously variable transmission which comprises an input shaft, a variable pump, a constant displacement motor, a double-planetary-gear mechanism, a gear shifting shaft, an output shaft and a brake. The variable pump is provided with an input shaft which is connected with the constant displacement motor in a hydrostatic transmission mode, and the constant displacement motor is provided with an output shaft. The double-planetary-gear mechanism comprises a front-row planetary gear system and a rear-row planetary gear system, and sun gears of the two planetary gear systems are fixed to a motor output shaft. An input shaft is provided with a forward gear clutch, an output shaft of the forward gear clutch is coaxially and fixedly connected with a front-row planet carrier and a rear-row planet gear ring, the front-row planet gear ring and the rear-row planet carrier are both provided with coaxial gear driving gears which are meshed with gear driven gears, and a synchronizer is arranged on a gear shifting shaft and used for achieving section shifting work of the transmission. The input shaft, the variable pump input shaft, the gear shifting shaft and the output shaft are in gear transmission, and the brake brakes the rear-row planetary gear ring. The speed changer is compact in structure, the section changing work of the speed changer is achieved through the synchronizer, and the sealing performance requirement and the manufacturing cost are reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to a continuously variable transmission belongs to transmission device technical field. BACKGROUND

[0002] The working condition of agricultural machinery and engineering machinery is poor, the load changes randomly and the amplitude is large, and high requirements are put forward to the speed changing device. The hydraulic mechanical continuously variable transmission is an ideal speed changing device for agricultural machinery and engineering machinery. However, there is a contradiction between the complexity of the hydraulic system and the number of working modes. Using fewer hydraulic components to realize as many working modes as possible while limiting the size of the transmission is one of the key design goals.

[0003] Most hydraulic mechanical continuously variable transmissions use wet clutches, which have relatively high sealing requirements for parts. The reverse mode of some transmissions is realized at the rear end, and the reverse mechanism bears a large torque. When the transmission pump and motor are integrated, the flexibility of space arrangement is poor. SUMMARY

[0004] In view of the above technical problems, the task of the utility model is to provide a hydraulic mechanical continuously variable transmission, which aims to increase the working mode, reduce the sealing requirement and manufacturing cost under the premise of reducing the number of clutches.

[0005] The technical scheme of the utility model is as follows: a hydraulic mechanical continuously variable transmission, comprising an input shaft, a variable pump, a constant displacement motor, a double planetary gear mechanism, a shift shaft, an output shaft and a brake;

[0006] The variable pump is provided with a variable pump input shaft, the variable pump is connected with the constant displacement motor in a hydrostatic transmission mode, the constant displacement motor is provided with a motor output shaft, the double planetary gear mechanism comprises a front planetary gear system and a rear planetary gear system, the sun gears of the front planetary gear system and the rear planetary gear system are fixed on the motor output shaft, the input shaft is provided with a forward gear clutch, the output shaft of the forward gear clutch is coaxially fixed with the planet carrier of the front planetary gear system and the ring gear of the rear planetary gear system, the ring gear of the front planetary gear system and the planet carrier of the rear planetary gear system are provided with coaxial gear shifting driving gears, the gear shifting driving gears are engaged with gear shifting driven gears, the shift shaft is provided with a synchronizer for selecting the gear shifting driven gears and synchronizing the rotation of the gear shifting driven gears with the shift shaft.

[0007] The input shaft and the variable pump input shaft are driven by gears, the shift shaft and the output shaft are driven by gears, and the brake is used to brake the ring gear of the rear planetary gear system.

[0008] Further, a reverse shaft is provided with a brake gear and a reverse clutch for determining whether to be in gear with the variable pump input shaft, the brake gear is engaged with the ring gear of the rear planetary gear system, and the brake is used to brake the brake gear.

[0009] Further, the ring gear of the front planetary gear system is provided with an even number of gear driving gears, and two groups of gear driven gears are engaged with the gear driving gears arranged on the ring gear of the front planetary gear system, and the synchronizer is used to select one or zero of the gear driven gears in a group to be combined.

[0010] Further, the ring gear of the front planetary gear system is provided with a two-gear driving gear and a four-gear driving gear, the shift shaft is provided with a two-gear driven gear and a four-gear driven gear, the shift shaft is provided with a two-four-gear synchronizer, and the two-four-gear synchronizer is used to select whether the two-gear driven gear or the four-gear driven gear is combined with the shift shaft.

[0011] Further, the planet carrier of the rear planetary gear system is provided with an even number of gear driving gears, and two groups of gear driven gears are engaged with the gear driving gears arranged on the ring gear of the rear planetary gear system, and the synchronizer is used to select one or zero of the gear driven gears in a group to be combined.

[0012] Further, the planet carrier of the rear planetary gear system is provided with a one-gear driving gear and a three-gear driving gear, the shift shaft is provided with a one-gear driven gear and a three-gear driven gear, the shift shaft is provided with a one-three-gear synchronizer, and the one-three-gear synchronizer is used to select whether the one-gear driven gear or the three-gear driven gear is combined with the shift shaft.

[0013] Further, the output shaft is provided with an output shaft gear, and the shift shaft is provided with a shift output gear, and the output shaft gear is engaged with the shift output gear.

[0014] Further, the variable pump and the constant motor are separately arranged.

[0015] The utility model has the advantages compared with prior art:

[0016] In the pure hydraulic working mode, the hydraulic transmission form can fully play the advantages of effectively transmitting low speed and large torque, and the starting performance of the agricultural or engineering machinery equipped with the transmission can be improved; when the transmission ratios of two adjacent working modes are equal, the corresponding synchronizer is controlled to be engaged and separated, the transformation between multiple working modes in the forward or reverse mode can be realized without power interruption, and the sealing requirement of the parts of the shift element is reduced, the motor power is directly output to the planetary gear mechanism, and the transmission efficiency is improved.

[0017] In the preferred technical solution, the engagement or disengagement of the clutch is used to switch the forward and reverse modes at the front end of the power transmission route, and the pump and motor are designed as a split structure, which reduces the difficulty of arranging the hydraulic transmission system and the manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Structure diagram of the hydraulic mechanical continuously variable transmission of Example 1.

[0019] Figure 2 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 0V mode at the start of forward movement.

[0020] Figure 3 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 1V mode at the forward movement.

[0021] Figure 4 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 2V mode at the forward movement.

[0022] Figure 5 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 3V mode at the forward movement.

[0023] Figure 6 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 4V mode at the forward movement.

[0024] Figure 7 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 0R mode at the start of reverse movement.

[0025] Figure 8 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 1R mode at the reverse movement.

[0026] Figure 9 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 2R mode at the reverse movement.

[0027] Figure 10 Power transmission route diagram when the hydraulic mechanical continuously variable transmission of Example 1 is running in the H 3R mode at the reverse movement.

[0028] Figure 11The hydraulic mechanical continuously variable transmission of Example 1 is operated in H 4R The schematic diagram of the transmission route of power when the hydraulic mechanical continuously variable transmission of Example 1 is operated in R

[0029] Figure 12 The speed regulation characteristic diagram when the hydraulic mechanical continuously variable transmission of Example 1 is operated in F

[0030] Figure 13 The speed regulation characteristic diagram when the hydraulic mechanical continuously variable transmission of Example 1 is operated in R

[0031] Figure 14 The schematic diagram of the structure of the hydraulic mechanical continuously variable transmission of Example 2 DETAILED DESCRIPTION

[0032] The utility model will be further described in connection with the examples below, but not as the limitation of the utility model.

[0033] Example 1, please combine Figure 1 The hydraulic mechanical continuously variable transmission of the example relates to a kind of, including input shaft 2, variable pump input shaft 4, reverse shaft 5, output shaft 22, shift shaft 24, motor output shaft 31, forward gear clutch output shaft 37 in space mutually parallel.

[0034] Drive device 1 output shaft is connected with forward gear clutch 38 by input shaft 2.

[0035] Power split gear 39 is fixed on input shaft 2, and is engaged with variable pump input end gear 3.Variable pump input end gear 3 is fixed on variable pump input shaft 4, and variable pump input shaft 4 is connected with variable pump 8.Variable pump 8 is connected with fixed displacement motor 20 by volumetric speed regulation circuit 19 in static liquid pressure transmission mode.Power of fixed displacement motor 20 is output through motor output shaft 31, and rear sun gear 30 and front sun gear 33 are fixed on motor output shaft 31, and rotate with motor output shaft 31.

[0036] Reverse gear 6 is engaged with variable pump input end gear 3.Reverse gear 6 is sleeved on reverse shaft 5, and reverse gear 6 is connected with reverse shaft 5 by reverse clutch 7.The driving part of reverse clutch 7 is connected with reverse gear 6, and the driven part of reverse clutch 7 is connected with reverse shaft 5.When reverse clutch 7 is engaged, reverse shaft 5 rotates with reverse gear 6.Brake gear 15 is fixed on reverse shaft 5, and rotates with reverse shaft 5.Brake gear 15 is engaged with the tooth made on the outer circle of rear gear ring 13.Brake 14 is fixed on frame or transmission housing, and brake gear 15 and the parts connected with brake gear 15 can be braked when necessary.

[0037] The forward gear clutch 38 outputs a forward gear clutch output shaft 37, which is integrated with the front planetary carrier 12 and the rear ring gear 13. The front planetary gear 32 is loosely fitted on the front planetary carrier 12 and meshes with the front ring gear 11 and the front sun gear 33. The front ring gear 11, the front planetary carrier 12, the front planetary gear 32 and the front sun gear 33 together form a front planetary gear train.

[0038] The rear planetary gear 29 is loosely fitted on the rear planetary carrier 16 and meshes with the rear ring gear 13 and the rear sun gear 30. The rear ring gear 13, the rear planetary carrier 16, the rear planetary gear 29 and the rear sun gear 30 together form a rear planetary gear train.

[0039] The hydraulic mechanical continuously variable transmission of the embodiment has four gears for selection, which are realized by four pairs of gears, i.e., the two-gear driving gear 9 and the two-gear driven gear 36, the one-gear driving gear 17 and the one-gear driven gear 28, the four-gear driving gear 10 and the four-gear driven gear 34, and the three-gear driving gear 18 and the three-gear driven gear 26. The two-gear driving gear 9 and the four-gear driving gear 10 are integrated with the front ring gear 11, and the one-gear driving gear 17 and the three-gear driving gear 18 are integrated with the rear planetary carrier 16. The three-gear driven gear 26, the one-gear driven gear 28, the four-gear driven gear 34 and the two-gear driven gear 36 are loosely fitted on the gear shift shaft 24. The three-gear synchronizer 27 and the two-four-gear synchronizer 35 are gear shift devices, and through the left and right actuation of the synchronizer rings thereof, the three-gear driven gear 26 or the one-gear driven gear 28 and the four-gear driven gear 34 or the two-gear driven gear 36 can be connected to the power transmission route, thereby completing the gear shift between gears.

[0040] The gear shift output gear 25 is fixed on the gear shift shaft 24 and meshes with the output shaft gear 21. The output shaft gear 21 is fixed on the output shaft 22, and the end of the output shaft 22 is the main reducer driving bevel gear 23.

[0041] The hydraulic mechanical continuously variable transmission of the embodiment uses two clutches, one brake and two synchronizers to control the gear shift, thereby realizing 10 different working modes. Among them, there are one pure hydraulic forward / reverse mode and four hydraulic-mechanical coupled forward / reverse modes, including the following modes:

[0042] Starting forward mode H 0V : The mode is a pure hydraulic mode, and the power transmission route is shown in Figure 2 : i 01 is the transmission ratio between the variable pump input gear 3 and the reverse gear 6; i 02 is the transmission ratio between the brake gear 15 and the rear ring gear 13; i pis the transmission ratio between the power split gear 39 and the variable pump input gear 3; k1 is the planetary gear set characteristic parameter of the front planetary gear set, and its value is equal to the gear ratio of the front ring gear 11 and the front sun gear 33; k2 is the planetary gear set characteristic parameter of the rear planetary gear set, and its value is equal to the gear ratio of the rear ring gear 13 inner ring and the front sun gear 33; i 11 is the transmission ratio between the second drive gear 9 and the second driven gear 36; i 12 is the transmission ratio between the fourth drive gear 10 and the fourth driven gear 34; i 21 is the transmission ratio between the first drive gear 17 and the first driven gear 28; i 22 is the transmission ratio between the third drive gear 18 and the third driven gear 26; i3 is the transmission ratio between the shift output gear 25 and the output shaft gear 21. In this mode, the forward clutch 38 is not engaged, the brake 14 generates a brake, and the brake gear 15 is locked, so that the brake gear 15, the rear ring gear 13, the front carrier 12 and the forward clutch output shaft 37 stop rotating, the engagement sleeve of the two-four synchronizer 35 moves to the left, and the engagement sleeve of the one-three synchronizer 27 is in the middle position and does not move. The system power is output along the driving device 1, the input shaft 2, the power split gear 39, the variable pump input gear 3, the variable pump input shaft 4, the variable pump 8, the positive displacement speed regulating circuit 19, the constant displacement motor 20, the motor output shaft 31, the front sun gear 33, the front planetary gear 32, the front ring gear 11, the second drive gear 9, the second driven gear 36, the two-four synchronizer 35, the shift shaft 24, the shift output gear 25, the output shaft gear 21, the output shaft 22.

[0043] Forward mode H 1V This mode is a hydraulic power flow and mechanical power flow coupled working gear, and the power transmission route is as follows Figure 3The power of the system is transmitted from the driving device 1 to the power split gear 39 through the input shaft 2, and split occurs at the power split gear 39. One part is transmitted along the power split gear 39, the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulation circuit 19, the fixed displacement motor 20, the motor output shaft 31, the front row sun gear 30 to the front row planet gear 29, and this part is the hydraulic power flow route; the other part is transmitted along the forward gear clutch 38, the forward gear clutch output shaft 37, the front row planet carrier 12, the rear row ring gear 13 to the rear row planet gear 29, and this part is the mechanical power flow route. The two parts of power are combined at the rear row planet gear 29, and then output through the rear row planet carrier 16, the first gear driving gear 17, the first gear driven gear 28, the third gear synchronizer 27, the shift shaft 24, the shift output gear 25, the output shaft gear 21, and the output shaft 22.

[0044] Forward mode H 2V This mode is a hydraulic power flow and mechanical power flow coupled working gear, and the power transmission route is as shown in Figure 4 The power of the system is transmitted from the driving device 1 to the power split gear 39 through the input shaft 2, and split occurs at the power split gear 39. One part is transmitted along the power split gear 39, the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulation circuit 19, the fixed displacement motor 20, the motor output shaft 31, the front row sun gear 30 to the front row planet gear 29, and this part is the hydraulic power flow route; the other part is transmitted along the forward gear clutch 38, the forward gear clutch output shaft 37, the front row planet carrier 12, the rear row ring gear 13 to the rear row planet gear 29, and this part is the mechanical power flow route. The two parts of power are combined at the rear row planet gear 29, and then output through the rear row planet carrier 16, the first gear driving gear 17, the first gear driven gear 28, the third gear synchronizer 27, the shift shaft 24, the shift output gear 25, the output shaft gear 21, and the output shaft 22.

[0045] Forward mode H 3V This mode is a hydraulic power flow and mechanical power flow coupled working gear, and the power transmission route is as shown in Figure 5The power of the system is transmitted from the driving device 1 to the power split gear 39 through the input shaft 2, and split occurs at the power split gear 39. One part is transmitted along the power split gear 39, the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulation circuit 19, the fixed displacement motor 20, the motor output shaft 31, the front row sun gear 33 to the front row planet gear 32, and this part is the hydraulic power flow route; the other part is transmitted along the forward gear clutch 38, the forward gear clutch output shaft 37, the front row planet carrier 12 to the front row planet gear 32, and this part is the mechanical power flow route. The two parts of power are combined at the front row planet gear 32, and then output through the front row ring gear 11, the fourth gear driving gear 10, the fourth gear driven gear 34, the two-four gear synchronizer 35, the shift shaft 24, the shift output gear 25, the output shaft gear 21, and the output shaft 22.

[0046] Forward mode H 4V This mode is a hydraulic power flow and mechanical power flow coupled working gear, and the power transmission route is as shown in Figure 6 The power of the system is transmitted from the driving device 1 to the power split gear 39 through the input shaft 2, and split occurs at the power split gear 39. One part is transmitted along the power split gear 39, the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulation circuit 19, the fixed displacement motor 20, the motor output shaft 31, the front row sun gear 33 to the front row planet gear 32, and this part is the hydraulic power flow route; the other part is transmitted along the forward gear clutch 38, the forward gear clutch output shaft 37, the front row planet carrier 12 to the front row planet gear 32, and this part is the mechanical power flow route. The two parts of power are combined at the front row planet gear 32, and then output through the front row ring gear 11, the fourth gear driving gear 10, the fourth gear driven gear 34, the two-four gear synchronizer 35, the shift shaft 24, the shift output gear 25, the output shaft gear 21, and the output shaft 22.

[0047] Starting reverse mode H 0R This mode is a pure hydraulic mode, and the power transmission route is as shown in Figure 7The power of the system is transmitted from the driving device 1 through the input shaft 2 to the power split gear 39, and then to the variable pump input end gear 3. The power is split at the variable pump input end gear 3. One part is transmitted along the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulation circuit 19, the fixed displacement motor 20, the motor output shaft 31, the front sun gear 33, the front planetary gear 32, the front gear ring 11, the second gear driving gear 9, the second gear driven gear 36, the second and fourth gear synchronizer 35, the shift shaft 24, the shift output gear 25, the output shaft gear 21, and the output shaft 22. The other part is transmitted along the variable pump input end gear 3, the reverse gear 6, the reverse clutch 7, the reverse shaft 5, the brake gear 15, the rear gear ring 13, the rear planetary gear 29, the rear planetary carrier 16, the first gear driving gear 17, the first gear driven gear 28, the first and third gear synchronizer 27, the shift shaft 24, the shift output gear 25, the output shaft gear 21, and the output shaft 22.

[0048] Reverse mode H 1R This mode is a hydraulic power flow and mechanical power flow coupling working gear position. The power transmission route is shown in Figure 8 The power of the system is transmitted from the driving device 1 through the input shaft 2 to the power split gear 39, and then to the variable pump input end gear 3. The power is split at the variable pump input end gear 3. One part is transmitted along the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulation circuit 19, the fixed displacement motor 20, the motor output shaft 31, the rear sun gear 30, and the rear planetary gear 29. The other part is transmitted along the variable pump input end gear 3, the reverse gear 6, the reverse clutch 7, the reverse shaft 5, the brake gear 15, and the rear gear ring 13. The two parts of power are combined at the rear planetary gear 29, and then output through the rear planetary carrier 16, the first gear driving gear 17, the first gear driven gear 28, the first and third gear synchronizer 27, the shift shaft 24, the shift output gear 25, the output shaft gear 21, and the output shaft 22.

[0049] Reverse mode H 2R This mode is a hydraulic power flow and mechanical power flow coupling working gear position. The power transmission route is shown in Figure 9The system power is transmitted from the driving device 1 to the power split gear 39 through the input shaft 2, and then transmitted to the variable pump input end gear 3. The power is split at the variable pump input end gear 3. One part is transmitted along the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulation circuit 19, the fixed displacement motor 20, the motor output shaft 31, the front row sun gear 33 to the front row planetary gear 32, which is the hydraulic power flow route; the other part is transmitted along the variable pump input end gear 3, the reverse gear 6, the reverse clutch 7, the reverse shaft 5, the brake gear 15, the rear row gear ring 13 to the front row planetary gear 32, which is the mechanical power flow route. The two parts of power are combined at the front row planetary gear 32, and then output through the front row gear ring 11, the second gear driving gear 9, the second gear driven gear 36, the second-fourth gear synchronizer 35, the shift output gear 25, the output shaft gear 21 and the output shaft 22.

[0050] Rearward mode H 3R The mode is a hydraulic power flow and mechanical power flow coupled working gear, and the power transmission route is as shown in Figure 10 The system power is transmitted from the driving device 1 to the power split gear 39 through the input shaft 2, and then transmitted to the variable pump input end gear 3. The power is split at the variable pump input end gear 3. One part is transmitted along the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulation circuit 19, the fixed displacement motor 20, the motor output shaft 31, the rear row sun gear 30 to the rear row planetary gear 29, which is the hydraulic power flow route; the other part is transmitted along the variable pump input end gear 3, the reverse gear 6, the reverse clutch 7, the reverse shaft 5, the brake gear 15, the rear row gear ring 13 to the rear row planetary gear 29, which is the mechanical power flow route. The two parts of power are combined at the rear row planetary gear 29, and then output through the rear row planetary carrier 16, the third gear driving gear 18, the third gear driven gear 26, the first-third gear synchronizer 27, the shift output gear 25, the output shaft gear 21 and the output shaft 22.

[0051] Rearward mode H 4R The mode is a hydraulic power flow and mechanical power flow coupled working gear, and the power transmission route is as shown in Figure 11The system power is transmitted from the driving device 1 to the power split gear 39 through the input shaft 2, and then transmitted from the power split gear 39 to the variable pump input end gear 3. The power is split at the variable pump input end gear 3. One part is transmitted along the variable pump input end gear 3, the variable pump input shaft 4, the variable pump 8, the volumetric speed regulating circuit 19, the constant flow motor 20, the motor output shaft 31, the front sun gear 33 to the front planetary gear 32, which is the hydraulic power flow route; the other part is transmitted along the variable pump input end gear 3, the reverse gear 6, the reverse clutch 7, the reverse shaft 5, the brake gear 15, the rear ring gear 13, the front planetary carrier 12 to the front planetary gear 32, which is the mechanical power flow route. The two parts of power are combined at the front planetary gear 32, and then output through the front ring gear 11, the fourth gear driving gear 10, the fourth gear driven gear 34, the two-four gear synchronizer 35, the shift shaft 24, the shift output gear 25, the output shaft gear 21, and the output shaft 22.

[0052] The total transmission ratio of the transmission and the working condition of the actuators in each mode are shown in Table 1, the actuator numbers are consistent with those in the drawings, and the speed regulating characteristics in forward and reverse are shown in Figure 12 and Figure 13 .

[0053] Table 1 Total transmission ratio of the transmission and working condition of the actuators in each mode

[0054]

[0055] Note: ε in the formula in the table is the ratio of the actual displacement of the variable pump to its rated displacement.

[0056] Example 2, as shown in Figure 14 , the hydraulic mechanical continuously variable transmission of the present example removes the reverse shaft 5, the reverse gear 6, the reverse clutch 7, and the brake gear 15 on the basis of Example 1. The brake 40 is arranged on the rear ring gear 13, and the hydraulic mechanical continuously variable transmission of the present example realizes reverse only through the adjustment of the hydraulic circuit. In reverse, the forward clutch 38 of the present example is not engaged, the rear ring gear 13 is locked by the brake 40, and the working of the four reverse modes is realized by controlling the rotational speed of the hydraulic motor 20 and the actuation of the one-three gear synchronizer 27 and the two-four gear synchronizer 35.

Claims

1. A hydraulic mechanical continuously variable transmission characterized by, The transmission comprises an input shaft, a variable pump, a fixed displacement motor, a double planetary gear mechanism, a shift shaft, an output shaft and a brake. The variable pump is provided with a variable pump input shaft, and is connected to the fixed displacement motor in a hydrostatic transmission mode, the fixed displacement motor is provided with a motor output shaft, the double planetary gear mechanism comprises a front planetary gear system and a rear planetary gear system, the sun gears of the front planetary gear system and the rear planetary gear system are fixed on the motor output shaft, the input shaft is provided with a forward gear clutch, the output shaft of the forward gear clutch is coaxially fixedly connected to the planet carrier of the front planetary gear system and the ring gear of the rear planetary gear system, the ring gear of the front planetary gear system and the planet carrier of the rear planetary gear system are both provided with coaxial gear driving gears, the gear driving gears are engaged with gear driven gears, the shift shaft is provided with a synchronizer for selecting the gear driven gears and synchronizing the gear driven gears with the shift shaft. The input shaft is in gear transmission with the variable pump input shaft, the shift shaft is in gear transmission with the output shaft, and the brake is used to brake the ring gear of the rear planetary gear system.

2. The hydraulic mechanical continuously variable transmission according to claim 1, characterized by The transmission comprises a reverse gear shaft, the reverse gear shaft is provided with a brake gear and a reverse gear clutch for determining whether to be in gear transmission with the variable pump input shaft, the brake gear is engaged with the ring gear of the rear planetary gear system, and the brake is used to brake the brake gear.

3. The hydraulic mechanical continuously variable transmission according to claim 1 or 2, characterized by, The ring gear of the front planetary gear system is provided with an even number of gear driving gears, the gear driven gears engaged with the gear driving gears of the ring gear of the front planetary gear system are two in a group, and the synchronizer is used to select one or zero gear driven gears in a group to be combined.

4. The hydraulic mechanical continuously variable transmission according to claim 3, characterized by The ring gear of the front planetary gear system is provided with a second gear driving gear and a fourth gear driving gear, the shift shaft is provided with a second gear driven gear and a fourth gear driven gear which are sleeved, the shift shaft is provided with a second-fourth gear synchronizer, and the second-fourth gear synchronizer is used to select whether the second gear driven gear or the fourth gear driven gear is combined with the shift shaft.

5. The hydraulic mechanical continuously variable transmission according to claim 1 or 2, characterized by, The planet carrier of the rear planetary gear system is provided with an even number of gear driving gears, the gear driven gears engaged with the gear driving gears of the planet carrier of the rear planetary gear system are two in a group, and the synchronizer is used to select one or zero gear driven gears in a group to be combined.

6. The hydraulic mechanical continuously variable transmission according to claim 5, characterized by The planet carrier of the rear planetary gear system is provided with a first gear driving gear and a third gear driving gear, the shift shaft is provided with a first gear driven gear and a third gear driven gear which are sleeved, the shift shaft is provided with a first-third gear synchronizer, and the first-third gear synchronizer is used to select whether the first gear driven gear or the third gear driven gear is combined with the shift shaft.

7. The hydraulic mechanical continuously variable transmission according to claim 1 or 2, characterized by, The output shaft is provided with an output shaft gear, and the shift shaft is provided with a shift output gear, the output shaft gear is engaged with the shift output gear.

8. The hydraulic mechanical continuously variable transmission according to claim 1 or 2, characterized by, The variable pump and the fixed displacement motor are separately arranged.

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