CN105114488B - A kind of temperature control method of water and its control system of AMT vehicles Retarder - Google Patents

Abstract

The invention discloses a water temperature control method and a control system for a hydraulic retarder of an AMT vehicle type, which includes a body controller BCU, an engine electronic control unit ECU, an automatic transmission electronic control unit TCU, a gearbox actuator and a hydraulic retarder. The retarder, the engine electronic control unit ECU, the automatic transmission electronic control unit TCU and the hydraulic retarder are all connected to the body controller BCU. The beneficial effects of the present invention are: ensuring reliable safety performance when going downhill; at the same time ensuring that the engine works within a reasonable working temperature range and ensuring fuel economy of the engine; when going downhill when the retarder has sufficient braking torque , without or less use of the main brake, the loss of the friction plate is reduced, and at the same time, the water tank that pours water on the friction plate can be abandoned when going downhill, and more goods can be carried; the present invention has high safety and economical aspects the value of.

Description

Water temperature control method and control system for AMT vehicle hydraulic retarder

technical field

The invention relates to the technical field of water temperature control of a hydraulic retarder of an AMT vehicle, in particular to a water temperature control method and a control system of a hydraulic retarder of an AMT vehicle.

Background technique

At present, the safety of vehicles is getting more and more attention, and hydraulic retarders are also widely used in heavy-duty commercial vehicles and passenger vehicles. For commercial vehicles, the assembled hydraulic retarder can abandon the water tank that sprays water on the friction plate, which increases the weight of the cargo, reduces the wear of the friction plate, and increases the economic performance and safety performance; It is said that reducing the wear of the friction plate can ensure the safety of passengers, and also increase the economic performance and safety performance. However, when the retarder is braking, it will generate a lot of heat, especially when going downhill. The heat will be dissipated by the cooling module of the engine through the water pipe. However, if the heat dissipation power of the cooling module is not enough, the engine water temperature will continue to rise. When the warning temperature is exceeded, the braking capacity of the retarder itself will be reduced, the engine power will be limited, and the function of the retarder will be reduced.

Contents of the invention

In order to solve the problem that the hydraulic retarder on the AMT model will generate a lot of heat when braking, which will cause the engine water temperature to be too high, resulting in the retarder's own braking ability becoming smaller and engine power limited, the invention provides A safe and reliable water temperature control method and control system for the hydraulic retarder of AMT vehicles are proposed.

In order to achieve the above-mentioned purpose of the invention, the invention provides a water temperature control method of a hydraulic retarder of an AMT vehicle, comprising the following steps:

(1) The hydraulic retarder starts to work and sends its status to the CAN bus. After receiving the status, the BCU starts to query the current water temperature value T ₁ ℃. If the water temperature value T ₁ is higher than the set warning temperature value T ₂ ℃, that is, when T ₁ >T ₂ , execute step (2); if the water temperature value T ₁ is lower than the warning temperature value T ₂ , execute step (5);

(2) The BCU receives the current engine speed value r ₁ , the rated speed value R ₃ , the current gear n ₁ , and calculates whether to downshift and the number of gears that can be downshifted in combination with the speed ratio difference g of the transmission in each gear n; if it is possible to downshift, send a downshift request to the TCU through the CAN bus;

(3) After receiving the request, the TCU controls the selector shift solenoid valve and the clutch booster cylinder to switch the transmission from n ₁ to the lower gear n ₂ ;

(4) The TCU sends a speed-up request to the engine ECU when downshifting, so that the engine speed increases from r ₁ to r ₂ , and then the engine fan speed also increases, and the cooling capacity is enhanced, so the engine water temperature can drop;

(5) The BCU continuously monitors the working status of the hydraulic retarder. If the hydraulic retarder continues to work, perform step (1), and if the hydraulic retarder stops working, perform step (6);

(6) End the operation, exit this mode, and the BCU performs other tasks.

Specifically, the water temperature control method of the AMT model hydraulic retarder includes the following steps:

(1) The hydraulic retarder starts to work and sends its status to the CAN bus. After receiving the status, the BCU starts to query the current water temperature value T ₁ ℃. If the water temperature value T ₁ is higher than the set warning temperature value T ₂ ℃, that is, when T ₁ >T ₂ , execute step (2), if the water temperature value T ₁ is lower than the warning temperature value T ₂ , execute the device of step (5);

The current water temperature T ₁ °C refers to the normal operating temperature of the engine, which is 85-103 °C; the warning temperature T ₂ °C is 95-103 °C.

(2) The BCU receives the current engine speed value r ₁ , the rated speed value R ₃ , the current gear n ₁ , and calculates whether to downshift and the number of gears that can be downshifted in combination with the speed ratio difference g of the transmission in each gear n; if it is possible to downshift, the device that sends a downshift request to the TCU through the device that controls the CAN bus;

The engine speed value r ₁ is 500-2600rpm and the rated speed value _R3 is 1900-2300rpm.

The speed ratio difference g of the transmission in different gears is 0.743-16.085.

(3) After the TCU receives the request, it controls the action of the selector shift solenoid valve and the clutch booster cylinder to switch the transmission from n ₁ to the lower gear n ₂ ;

The transmission n ₁ refers to the forward gear of the automatic transmission, the gear range of the 16-speed gearbox is 1≤n ₁ ≤16; the gear range of the 10-speed gearbox is 1≤n ₁ ≤10; the lower gear n ₂ means n ₂ <n ₁ ;

(4) The TCU sends a speed-up request to the engine ECU when downshifting, and the device controlling the engine speed increases the engine speed from r ₁ to r ₂ , and then the engine fan speed also rises accordingly, and the cooling capacity is enhanced, so the engine water temperature devices capable of descending;

(6) End the operation, exit this mode, and the BCU performs other tasks.

In order to better realize the above-mentioned invention object, the present invention also provides a kind of control system of the water temperature of AMT vehicle type hydraulic retarder, comprises following device: comprises following device:

(1) The hydraulic retarder starts to work and sends its status to the CAN bus. After receiving the status, the BCU starts to query the current water temperature value T ₁ ℃. If the water temperature value T ₁ is higher than the set warning temperature value T ₂ ℃, that is, when T ₁ >T ₂ , execute step (2), if the water temperature value T ₁ is lower than the warning temperature value T ₂ , execute the device of step (5);

(2) The BCU receives the current engine speed value r ₁ , the rated speed value R ₃ , the current gear n ₁ , and calculates whether to downshift and the number of gears that can be downshifted in combination with the speed ratio difference g of the transmission in each gear n; if it is possible to downshift, the device that sends a downshift request to the TCU through the device that controls the CAN bus;

(3) After the TCU receives the request, it controls the action of the selector shift solenoid valve and the clutch booster cylinder to switch the transmission from n ₁ to the lower gear n ₂ ;

(4) The TCU sends a speed-up request to the engine ECU when downshifting, and the device controlling the engine speed increases the engine speed from r ₁ to r ₂ , and then the engine fan speed also rises accordingly, and the cooling capacity is enhanced, so the engine water temperature devices capable of descending;

(5) The BCU continuously monitors the working status of the hydraulic retarder. If the hydraulic retarder continues to work, execute step (1), and if the hydraulic retarder stops working, execute the device in step (6);

(6) End operation, exit this mode, and BCU executes other tasks.

Specifically, a water temperature control system of a hydraulic retarder of an AMT model includes a body controller BCU, an engine electronic control unit ECU, an automatic transmission electronic control unit TCU, a gearbox actuator and a hydraulic retarder. The engine electronic control unit ECU, the automatic transmission electronic control unit TCU and the hydraulic retarder are all connected to the body controller BCU;

The body controller BCU is respectively connected with the engine electronic control unit ECU, the automatic transmission electronic control unit TCU and the hydraulic retarder through the CAN bus; it is used to send the working state of the hydraulic retarder to the CAN On the bus, when the BCU receives its status, it starts to query the current water temperature value. If the water temperature is higher than the set warning temperature, the BCU receives the current engine speed value and the rated speed value, and combines the gear ratio difference of the transmission to calculate whether to downshift. And the number of gears that can be downshifted. If it is possible to downshift, a downshift request will be sent to the TCU through the CAN bus; if the water temperature is lower than the warning temperature, the BCU will continue to monitor the working status of the hydraulic retarder. If the hydraulic retarder continues to If it is working, execute the state of the hydraulic retarder, send it to the CAN bus, and the BCU receives its state; if the hydraulic retarder stops working, end the operation, exit this mode, and the BCU performs other tasks.

The output port and the input port of the electronic control unit TCU of the automatic transmission are respectively connected to the input port and the output port of the body controller BCU; used to send the working state of the hydraulic retarder to the CAN bus, and the BCU receives it state, the BCU receives the current engine speed value and rated speed value, combined with the transmission speed ratio difference, calculates whether to downshift, and the number of gears that can be downshifted; after receiving the request, the TCU controls the shift solenoid valve and the clutch booster cylinder Action, so that the transmission is switched to low gear; TCU sends a speed-up request to the engine ECU at the same time, after the engine speed rises, the fan speed connected to it also rises, the cooling capacity is improved, and the water temperature is lowered; BCU continuously monitors the working status of the hydraulic retarder , if the hydraulic retarder continues to work, it will be sent to the CAN bus, and the BCU will receive its status. If the hydraulic retarder stops working, it will execute the end operation, exit this mode, and the BCU will perform other tasks.

The input port of the gearbox actuator is connected to the output port of the automatic transmission electronic control unit TCU; after the TCU receives the request, it controls the action of the selector shift solenoid valve and the clutch booster cylinder, so that the transmission is switched to a low gear; At the same time, the TCU sends a speed-up request to the engine ECU. After the engine speed rises, the speed of the fan connected to it also rises, the cooling capacity is improved, and the water temperature is lowered;

The engine electronic control unit ECU is used to receive the speed-up request sent by the TCU to the engine ECU. After the engine speed rises, the speed of the fan connected to it also rises, the cooling capacity is improved, and the water temperature is lowered;

The automatic transmission electronic control unit TCU is used to control the action of the selector shift solenoid valve and the clutch booster cylinder after receiving the request from the BCU, so that the transmission is switched to a low gear; at the same time, the TCU sends a speed-up request to the engine ECU. , the speed of the fan connected to it also increases, the cooling capacity increases, and the water temperature decreases;

The hydraulic retarder starts to work and sends its state to the CAN bus.

The working method of the water temperature control system of the hydraulic retarder of the above-mentioned AMT vehicle type comprises the following steps:

(1) The hydraulic retarder starts to work and sends its status to the CAN bus. After receiving the status, the BCU starts to query the current water temperature value T ₁ ℃. If the water temperature value T ₁ is higher than the set warning temperature value T ₂ ℃, that is, when T ₁ >T ₂ , execute step (2); if the water temperature value T ₁ is lower than the warning temperature value T ₂ , execute step (5);

(2) The BCU receives the current engine speed value r ₁ , the rated speed value R ₃ , the current gear n ₁ , and calculates whether to downshift and the number of gears that can be downshifted in combination with the speed ratio difference g of the transmission in each gear n; if it is possible to downshift, send a downshift request to the TCU through the CAN bus;

(3) After receiving the request, the TCU controls the selector shift solenoid valve and the clutch booster cylinder to switch the transmission from n ₁ to the lower gear n ₂ ;

(4) The TCU sends a speed-up request to the engine ECU when downshifting, so that the engine speed increases from r ₁ to r ₂ , and then the engine fan speed also increases, and the cooling capacity is enhanced, so the engine water temperature can drop;

(5) The BCU continuously monitors the working status of the hydraulic retarder. If the hydraulic retarder continues to work, perform step (1), and if the hydraulic retarder stops working, perform step (6);

(6) End the operation, exit this mode, and the BCU performs other tasks.

Specifically, the water temperature control method of the AMT model hydraulic retarder includes the following steps:

(1) The hydraulic retarder starts to work and sends its status to the CAN bus. After receiving the status, the BCU starts to query the current water temperature value T ₁ ℃. If the water temperature value T ₁ is higher than the set warning temperature value T ₂ ℃, that is, when T ₁ >T ₂ , execute step (2); if the water temperature value T ₁ is lower than the warning temperature value T ₂ , execute step (5);

The current water temperature T ₁ °C refers to the normal operating temperature of the engine, which is 85-103 °C; the warning temperature T ₂ °C is 95-103 °C.

(2) The BCU receives the current engine speed value r ₁ , the rated speed value R ₃ , the current gear n ₁ , and calculates whether to downshift and the number of gears that can be downshifted in combination with the speed ratio difference g of the transmission in each gear n; if it is possible to downshift, send a downshift request to the TCU through the CAN bus; the engine speed value r ₁ , the rated speed value R ₃ , the current gear n ₁ , combined with the speed ratio difference g of the transmission in different gears, Calculate whether to downshift and the number of gears n that can be downshifted; if downshifting is possible, send a downshift request to the TCU through the CAN bus;

The engine speed value r ₁ is 500-2600rpm and the rated speed value _R3 is 1900-2300rpm.

The speed ratio difference g of the transmission in different gears is 0.743-16.085.

(3) After receiving the request, the TCU controls the selector shift solenoid valve and the clutch booster cylinder to switch the transmission from n ₁ to a lower gear n ₂ ; the transmission n ₁ refers to the forward gear of the automatic transmission, 16 Gearbox gear range is 1≤n1≤16; ₁₀ -speed gearbox gear range is _1≤n1≤10 ; said lower gear _n2 means _n2 <n1 _;

(4) The TCU sends a speed-up request to the engine ECU when downshifting, so that the engine speed increases from r ₁ to r ₂ , and then the engine fan speed also increases, and the cooling capacity is enhanced, so the engine water temperature can drop;

(5) The BCU continuously monitors the working status of the hydraulic retarder. If the hydraulic retarder continues to work, perform step (1), and if the hydraulic retarder stops working, perform step (6);

(6) End the operation, exit this mode, and the BCU performs other tasks.

The beneficial effects of the present invention are: In the present invention, the vehicle control unit (BCU) continuously monitors the water temperature value sent by the engine ECU, and when the water temperature reaches the warning temperature, it combines the current engine speed value, engine rated speed value, transmission low gear ratio Calculate the number of gears that may be downshifted. If downshifting is possible, a downshift request will be sent to the automatic transmission electronic control unit (TCU), which will control the work of the selector shift solenoid valve and the clutch booster cylinder to automatically complete the downshift action. The speed of the engine after the gear is increased, and the speed of the fan connected to it is also increased. The heat dissipation capacity of the cooling module becomes larger, and the heat generated will be taken away in time, thereby reducing the water temperature. After the water temperature is lowered, the retarder can maintain sufficient braking torque, thereby ensuring reliable safety performance when going downhill; at the same time, ensuring that the engine works within a reasonable operating temperature range and ensuring engine fuel economy; when going downhill, the retarder When the gearbox has sufficient braking torque, the main brake is not used or used less, which reduces the loss of the friction plate. At the same time, it can abandon the water tank that pours water on the friction plate when going downhill, and can carry more goods. High security and economical value.

Description of drawings

Fig. 1 is a structural block diagram of Embodiment 1 of the present invention.

Fig. 2 is a flowchart of Embodiment 1 and Embodiment 2 of the present invention.

detailed description

Example 1

Referring to Fig. 1 and Fig. 2, embodiment 1 of the present invention provides a kind of water temperature control system of hydraulic retarder of AMT vehicle type, comprises body controller BCU, engine electronic control unit ECU, automatic transmission electronic control unit TCU, gearbox The actuator and the hydraulic retarder, the engine electronic control unit ECU, the automatic transmission electronic control unit TCU and the hydraulic retarder are all connected to the body controller BCU;

The body controller BCU is respectively connected with the engine electronic control unit ECU, the automatic transmission electronic control unit TCU and the hydraulic retarder through the CAN bus; it is used to send the working state of the hydraulic retarder to the CAN On the bus, when the BCU receives its status, it starts to query the current water temperature value. If the water temperature is higher than the set warning temperature, the BCU receives the current engine speed value and the rated speed value, and combines the gear ratio difference of the transmission to calculate whether to downshift. And the number of gears that can be downshifted. If it is possible to downshift, a downshift request will be sent to the TCU through the CAN bus; if the water temperature is lower than the warning temperature, the BCU will continue to monitor the working status of the hydraulic retarder. If the hydraulic retarder continues to If it is working, execute the state of the hydraulic retarder, send it to the CAN bus, and the BCU receives its state; if the hydraulic retarder stops working, end the operation, exit this mode, and the BCU performs other tasks.

The output port and the input port of the electronic control unit TCU of the automatic transmission are respectively connected to the input port and the output port of the body controller BCU; used to send the working state of the hydraulic retarder to the CAN bus, and the BCU receives it state, the BCU receives the current engine speed value and rated speed value, combined with the transmission speed ratio difference, calculates whether to downshift, and the number of gears that can be downshifted; after receiving the request, the TCU controls the shift solenoid valve and the clutch booster cylinder Action, so that the transmission is switched to low gear; TCU sends a speed-up request to the engine ECU at the same time, after the engine speed rises, the fan speed connected to it also rises, the cooling capacity is improved, and the water temperature is lowered; BCU continuously monitors the working status of the hydraulic retarder , if the hydraulic retarder continues to work, it will be sent to the CAN bus, and the BCU will receive its status. If the hydraulic retarder stops working, it will execute the end operation, exit this mode, and the BCU will perform other tasks.

The input port of the gearbox actuator is connected to the output port of the automatic transmission electronic control unit TCU; after the TCU receives the request, it controls the action of the selector shift solenoid valve and the clutch booster cylinder, so that the transmission is switched to a low gear; At the same time, the TCU sends a speed-up request to the engine ECU. After the engine speed rises, the speed of the fan connected to it also rises, the cooling capacity is improved, and the water temperature is lowered;

The engine electronic control unit ECU is used to receive the speed-up request sent by the TCU to the engine ECU. After the engine speed rises, the speed of the fan connected to it also rises, the cooling capacity is improved, and the water temperature is lowered;

The automatic transmission electronic control unit TCU is used to control the action of the selector shift solenoid valve and the clutch booster cylinder after receiving the request from the BCU, so that the transmission is switched to a low gear; at the same time, the TCU sends a speed-up request to the engine ECU. , the speed of the fan connected to it also increases, the cooling capacity increases, and the water temperature decreases;

The hydraulic retarder starts to work and sends its state to the CAN bus.

The working method of the water temperature control system of the hydraulic retarder of the above-mentioned AMT vehicle type comprises the following steps:

(1) After the engine ECU is powered on, it collects the current coolant temperature t ₁ (unit: °C) through the water temperature sensor, and sends it to the CAN bus through CAN information ET1. The sending cycle is 1000ms. The specific content is as follows .

The body controller (BCU) can read the information of ET1 from the CAN line to know the current water temperature value.

(2) When the hydraulic retarder starts to work, it will send its status to the CAN bus through the message ERC1, and the sending cycle is 100ms.

When a ₁ =0, it means that the retarder is not acting on braking; if a ₁ >0, it means that the retarder is acting on braking.

(3) The BCU checks the content of ERC1. When a ₁ >0 is found, it starts to query the current water temperature t ₁ ℃, and the alert temperature t ₂ is 100 ℃. If the current water temperature t ₁ ≥ t _2, execute the step ( 4), if t ₁ <t ₂ , execute step (9);

(4) The BCU obtains the current engine speed value r ₁ and the current gear n ₁ of the AMT transmission from the EEC1 information and ETC2 information respectively through the CAN bus. The specific messages are shown in the table below, and the sending cycles are 20ms and 100ms respectively.

(5) The BCU recalls the stored current transmission in gear n ₁ with speed ratio g ₁ . The speed ratio of each gear can be obtained after the transmission is designed. The 10-speed AMT gearbox installed on a heavy-duty vehicle directly shifts the speed See the table below:

The engine rated speed of MC07 loaded on a heavy-duty vehicle is 2300rpm. The BCU receives EC1 message from the CAN bus, and the rated engine speed _R3 is 2300rpm. The specific message is shown in the table below, and the sending cycle is 1000ms.

Assuming that the speed after shifting to n ₂ is r ₂ , then:

r ₂ =r ₁ *g ₂ /g ₁ (1)

Compare _r2 with engine rated speed _R3 . If r ₂ <R ₃ , it means that the gear shift can be performed; if r ₂ >R ₃ , it means that the speed r ₂ after the gear shift has exceeded the rated speed R ₃ of the engine, and the gear shift cannot be performed. If it is possible to shift gears, go to step (6), otherwise go to step (9);

(6) During the downhill process, the gearbox power system is interrupted, and the TCU keeps the gear unchanged. The BCU sends the TC1 signal through the CAN bus to request the AMT downshift request. The specific content is shown in the table below, and the sending cycle is 10ms.

(7) After the TCU receives the shift request, it controls the clutch booster cylinder and the selector shift solenoid valve to operate, so that the transmission automatically shifts to the target gear g ₂ .

(8) When the engine fan silicone oil clutch is fully engaged, the fan speed is directly related to the engine speed, and the speed ratio is 1.25:1. When the engine speed increases, the fan speed also increases to 1.25 times, and the cooling speed of the engine water temperature is greatly enhanced, so that the water temperature can be lowered rapidly, ensuring that the retarder has sufficient braking capacity all the time.

(9) The BCU continuously monitors the working status of the retarder. If the retarder continues to work, execute step (1), and if the retarder stops working, execute step (10);

(10) End the operation, exit this mode, and the BCU performs other tasks.

Example 2

Referring to Fig. 2, the embodiment of the present invention provides a kind of control method of AMT heavy-duty special vehicle transfer gear shifting, comprises the following steps:

(1) After the engine ECU is powered on, it collects the current coolant temperature t ₁ (unit: °C) through the water temperature sensor, and sends it to the CAN bus through CAN information ET1. The sending cycle is 1000ms. The specific content is as follows .

The body controller (BCU) can read the information of ET1 from the CAN line to know the current water temperature value.

(2) When the hydraulic retarder starts to work, it will send its status to the CAN bus through the message ERC1, and the sending cycle is 100ms.

When a ₁ =0, it means that the retarder is not acting on braking; if a ₁ >0, it means that the retarder is acting on braking.

(3) The BCU checks the content of ERC1. When a ₁ >0 is found, it starts to query the current water temperature t ₁ , and the alert temperature t ₂ is 100°C. If the current water temperature t ₁ ≥ t ₂ , execute step (4 ), if t ₁ <t ₂ , then execute step (9).

(4) The BCU obtains the heavy-duty vehicle MC11 engine with the current engine speed value r ₁ from the EEC1 information and the ETC2 information through the CAN bus, and the current gear n ₁ of the AMT transmission. See the table below for each specific message, and the sending cycle is 20ms, 100ms.

(5) The BCU recalls the stored speed ratio g ₁ of the current transmission at n _1. The overdrive speed ratio of the 16-speed AMT transmission loaded on a heavy-duty vehicle is shown in the following table:

Assembled on the MC11 engine of the heavy-duty vehicle, the BCU receives the EC1 message from the CAN bus, and obtains that the rated speed _R3 of the engine is 1900rpm. The specific message is shown in the table below, and the sending cycle is 1000ms.

message name SPN name Message content EC1 Engine Speed At Point 2 R ₃ (rpm)

Assuming that the speed after shifting to n ₂ is r ₂ , then:

r ₂ =r ₁ *g ₂ /g ₁ (1)

Compare _r2 with engine rated speed _R3 . If r ₂ <R ₃ , it means that the gear shift can be performed; if r ₂ >R ₃ , it means that the speed r ₂ after the gear shift has exceeded the rated speed R ₃ of the engine, and the gear shift cannot be performed. If it is possible to shift gears, go to step (6), otherwise go to step (9);

(6) During the downhill process, the transmission power system is interrupted, and the TCU keeps the gear unchanged, unless external factors cause the automatic transmission to downshift. BCU sends TC1 signal to request AMT downshift request through CAN bus, the specific content is shown in the table below, and the sending cycle is 10ms.

(7) After the TCU receives the shift request, it controls the clutch booster cylinder and the selector shift solenoid valve to operate, so that the transmission automatically shifts to the target gear g ₂ .

(8) When the engine fan silicone oil clutch is fully engaged, the fan speed is directly related to the engine speed, and the speed ratio is 1.25:1. When the engine speed increases, the fan speed also increases to 1.25 times, and the cooling speed of the engine water temperature is greatly enhanced, so that the water temperature can be lowered rapidly, ensuring that the retarder has sufficient braking capacity all the time.

(9) The BCU continuously monitors the working status of the retarder. If the retarder continues to work, execute step (1), and if the retarder stops working, execute step (10);

(10) End the operation, exit this mode, and the BCU performs other tasks.

The undescribed technical features of the present invention can be realized by or using the prior art, and will not be repeated here. Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Those of ordinary skill in the art Changes, modifications, additions or substitutions made within the essential scope of the present invention shall also belong to the present invention.

Claims (2)

1. A water temperature control system of a hydraulic retarder of an AMT vehicle type, comprising a vehicle body controller BCU, an engine electronic control unit ECU, an automatic transmission electronic control unit TCU, a gearbox actuator and a hydraulic retarder, the engine electronic The control unit ECU, the automatic transmission electronic control unit TCU and the hydraulic retarder are all connected to the body controller BCU; The body controller BCU is respectively connected with the engine electronic control unit ECU, the automatic transmission electronic control unit TCU and the hydraulic retarder through the CAN bus; it is used to send the working state of the hydraulic retarder to the CAN On the bus, when the BCU receives its status, it starts to query the current water temperature value. If the water temperature is higher than the set warning temperature, the BCU receives the current engine speed value and the rated speed value, and combines the gear ratio difference of the transmission to calculate whether to downshift. And the number of gears that can be downshifted. If it is possible to downshift, a downshift request will be sent to the TCU through the CAN bus; if the water temperature is lower than the warning temperature, the BCU will continue to monitor the working status of the hydraulic retarder. If the hydraulic retarder continues to If it is working, execute the status of the hydraulic retarder, send it to the CAN bus, and the BCU will receive its status; if the hydraulic retarder stops working, the operation will end; The output port and the input port of the electronic control unit TCU of the automatic transmission are respectively connected to the input port and the output port of the body controller BCU; used to send the working state of the hydraulic retarder to the CAN bus, and the BCU receives it state, the BCU receives the current engine speed value and rated speed value, combined with the transmission speed ratio difference, calculates whether to downshift, and the number of gears that can be downshifted; after receiving the request, the TCU controls the shift solenoid valve and the clutch booster cylinder Action, so that the transmission is switched to low gear; TCU sends a speed-up request to the engine ECU at the same time, after the engine speed rises, the fan speed connected to it also rises, the cooling capacity is improved, and the water temperature is lowered; BCU continuously monitors the working status of the hydraulic retarder , if the hydraulic retarder continues to work, it will be sent to the CAN bus, and the BCU will receive its status, and if the hydraulic retarder stops working, it will execute the end operation; The input port of the gearbox actuator is connected to the output port of the automatic transmission electronic control unit TCU; after the TCU receives the request, it controls the action of the selector shift solenoid valve and the clutch booster cylinder, so that the transmission is switched to a low gear; At the same time, the TCU sends a speed-up request to the engine ECU. After the engine speed rises, the speed of the fan connected to it also rises, the cooling capacity is improved, and the water temperature is lowered; The engine electronic control unit ECU is used to receive the speed-up request sent by the TCU to the engine ECU. After the engine speed rises, the speed of the fan connected to it also rises, the cooling capacity is improved, and the water temperature is lowered; The automatic transmission electronic control unit TCU is used to control the action of the selector shift solenoid valve and the clutch booster cylinder after receiving the request from the BCU, so that the transmission is switched to a low gear; at the same time, the TCU sends a speed-up request to the engine ECU. , the speed of the fan connected to it also increases, the cooling capacity increases, and the water temperature decreases; The hydraulic retarder starts to work and sends its state to the CAN bus. 2. the control method of the water temperature control system of AMT vehicle type hydraulic retarder according to claim 1, is characterized in that, described control method comprises the following steps: (1) The hydraulic retarder starts to work and sends its status to the CAN bus. After receiving the status, the BCU starts to query the current water temperature value T1°C. If the water temperature value T1 is higher than the set warning temperature value T2°C , that is, when T1>T2, execute step (2), if the water temperature value T1 is lower than the warning temperature value T2, execute step (5); The current water temperature value T1°C refers to the normal operating temperature of the engine, which is 85-103°C; the warning temperature value T2°C is 95-103°C; (2) The BCU receives the current engine speed value r1, the rated speed value R3, and the current gear position n1, and combines the speed ratio difference g of the transmission in each gear position to calculate whether to downshift and the number of gears n that can be downshifted; if If it is possible to downshift, then a downshift request is sent to the TCU through the CAN bus; the engine speed value r1, the rated speed value R3, the current gear position n1, combined with the speed ratio difference g of the transmission in different gear positions, calculate whether to downshift and The number of gears that can be downshifted is n; if it is possible to downshift, a downshift request is sent to the TCU through the CAN bus; The engine speed value r1 is 500-2600rpm, and the rated speed value R3 is 1900-2300rpm; The speed ratio difference g of the transmission in different gears is 0.743-16.085; (3) After receiving the request, the TCU controls the selector shift solenoid valve and the clutch booster cylinder to switch the transmission from n1 to the lower gear n2; the transmission n1 refers to the forward gear of the automatic transmission, a 16-speed transmission The gear range is 1≤n1≤16; the gear range of the 10-speed gearbox is 1≤n1≤10; the lower gear n2 refers to n2<n1; (4) The TCU sends a speed-up request to the engine ECU when downshifting, so that the engine speed increases from r1 to r2, and then the engine fan speed also increases, and the cooling capacity is enhanced, so the engine water temperature can drop; (5) The BCU continuously monitors the working status of the hydraulic retarder. If the hydraulic retarder continues to work, perform step (1), and if the hydraulic retarder stops working, perform step (6); (6) End operation.