Power matching method and system of hydraulic mechanical stepless speed change tractor

Abstract

The invention discloses a power matching method and system for a hydraulic mechanical stepless speed change tractor, and relates to the field of stepless speed change tractors, and the power matching method comprises the following steps: obtaining the vehicle speed requested by a driver for the whole tractor, and calculating the required torque of an engine at the vehicle speed requested; the actual minimum rotating speed and the theoretical minimum engine rotating speed of the engine at the requested vehicle speed are calculated, and the larger value of the actual minimum rotating speed and the theoretical minimum engine rotating speed is taken as the required rotating speed of the engine; and the required rotating speed serves as the initial requested rotating speed of the engine, and the maximum driving torque of the engine at the initial requested rotating speed is calculated. According to the power matching method and system, under the condition that when the stepless speed change tractor works in a heavy-load mode, a driver rapidly increases and decreases the speed of the whole tractor or suddenly changes the load, the conditions that the rotating speed of an engine is reduced and even flameout and parking are even are avoided through the reasonable power matching method, and meanwhile the comfort of the driver is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of continuously variable transmission tractor, in particular to a power matching method and system of hydraulic mechanical continuously variable transmission tractor. BACKGROUND

[0002] In the process of continuous high production and efficiency operation, machine protection becomes a basic requirement of modern intelligent tractor, at the same time, the driver's comfort requirement of agricultural machinery is also increasing, which has higher requirements on the intelligent degree of agricultural machinery, how to improve the intelligent level of agricultural machinery and reduce the labor intensity of agricultural machinery driver is one of the important trends of agricultural machinery development, tractor working condition is complex and diverse, and the power source is generally diesel engine, due to the limitation of its own external characteristics (the engine external characteristic curve is the curve of engine output power (torque) changing with speed when the engine throttle opening is 100%), when the load torque exceeds the maximum torque at this speed, the engine will slow down or even stall, and the tractor will appear impact speed reduction or even stop phenomenon. This situation not only affects the driving experience, but also causes damage to the transmission system of the whole machine.

[0003] The hydraulic mechanical continuously variable transmission tractor can realize stepless speed regulation, and the speed of the tractor can be raised or lowered by adjusting the transmission ratio of the gearbox under the condition that the engine speed is unchanged, and the driving comfort of the whole machine is high. However, the power source of the hydraulic mechanical continuously variable transmission tractor is also generally a diesel engine, and the whole machine will stall and stop when the load exceeds the maximum torque of the engine at this speed. The transmission ratio of the hydraulic mechanical continuously variable transmission tractor is continuously adjustable, and the whole machine adopts an electronic control system, so it is necessary to develop a power matching method and system which can avoid the stall and stop of the whole tractor and improve the comfort of the driver. SUMMARY

[0004] The present application aims to provide a power matching method and system of hydraulic mechanical continuously variable transmission tractor, which can avoid the situation of engine speed reduction or even stall and stop under the condition that the driver quickly raises or lowers the speed of the whole machine or the load of the whole machine suddenly changes under heavy load working of the continuously variable transmission tractor, and ensure the comfort of the driver.

[0005] The technical scheme adopted by the present application is as follows: a power matching method of hydraulic mechanical continuously variable transmission tractor, comprising the following steps:

[0006] Obtaining the requested speed of the whole machine by the driver, and calculating the required torque of the engine at the requested speed;

[0007] Calculating the actual minimum speed of the engine at the requested speed and the theoretical minimum engine speed, and taking the larger value of the actual minimum speed and the theoretical minimum engine speed as the required speed of the engine;

[0008] The demand rotating speed is taken as an initial request rotating speed of the engine, and the maximum driving torque of the engine at the initial request rotating speed is calculated;

[0009] If the maximum driving torque at the initial request rotating speed is greater than or equal to the demand torque of the engine, the engine is controlled according to the initial request rotating speed;

[0010] If the maximum driving torque at the initial request rotating speed is less than the demand torque of the engine, the demand rotating speed of the engine is compensated step by step within the range of the maximum rotating speed of the engine, and the compensated demand rotating speed is taken as a request rotating speed to control the engine, and the gear ratio is reduced until the whole machine maintains at the request vehicle speed, at which time the maximum driving torque of the engine at the request vehicle speed is greater than or equal to the demand torque.

[0011] As a preferred solution, the calculation of the demand torque of the engine at the request vehicle speed comprises:

[0012] The load torque when the acceleration of the whole machine is zero is obtained;

[0013] The request vehicle speed input by the driver and the current vehicle speed of the whole machine are obtained, and the request acceleration is calculated according to the request vehicle speed and the current vehicle speed;

[0014] The demand torque of the engine at the request vehicle speed is calculated according to the request acceleration, the load of the whole machine and the load torque.

[0015] As a preferred solution, the calculation of the actual minimum rotating speed of the engine at the request vehicle speed comprises:

[0016] The demand power is calculated based on the request vehicle speed, and the engine external characteristic table of the whole machine is inquired to obtain the actual minimum rotating speed of the engine at the demand power.

[0017] As a preferred solution, the theoretical minimum engine rotating speed is calculated according to the request vehicle speed and the maximum gear ratio of the whole machine, wherein the maximum gear ratio of the whole machine is the product of the central transmission ratio and the maximum gear ratio of the gearbox.

[0018] As a preferred solution, the calculation of the maximum driving torque of the engine at the request rotating speed comprises:

[0019] The maximum torque of the engine at the request rotating speed is obtained by inquiring the engine external characteristic table of the whole machine, and the request gear ratio is obtained by the request vehicle speed and the request rotating speed;

[0020] The maximum driving torque at the request rotating speed is obtained according to the maximum torque at the request rotating speed and the request gear ratio.

[0021] As a preferred solution, the actual torque T ac at the current vehicle speed is periodically obtained and compared with the maximum torque T re at the request rotating speed, and if T ac ≥ t*Tre Wherein t is the engine torque safety factor, 0 ac If T re No speed compensation is needed.

[0022] As a preferred solution, before the compensated demand speed is used to control the engine, if the compensated demand speed exceeds the maximum speed of the engine, the lift arm is lifted step by step within the working range of the lift arm to reduce the load until the machine maintains the requested speed and the maximum driving torque of the engine is greater than or equal to the demand torque; if the compensated demand speed does not exceed the maximum speed of the engine, the height of the lift arm does not need to be changed.

[0023] As a preferred solution, the speed ratio is reduced in coordination until the machine maintains the requested speed, including:

[0024] The actual acceleration and the requested acceleration of the machine are obtained.

[0025] The requested speed ratio is adjusted step by step according to the requested acceleration of the machine and the actual speed change rate of the engine until the actual acceleration of the machine is equal to the requested acceleration.

[0026] A power matching system of a hydraulic mechanical stepless variable speed tractor, comprising:

[0027] A driver control module: used to obtain the requested speed of the machine by the driver and transmit the obtained signal data to the TCU control module;

[0028] A sensing module: used to obtain the load, speed and torque of the machine and transmit the obtained signal data to the TCU control module;

[0029] An execution module: used to receive and execute the speed ratio sent by the TCU control module to make the machine maintain the requested speed;

[0030] An engine control module: used to receive and execute the requested speed sent by the TCU control module, and feed back the obtained current speed and torque of the engine to the TCU control module;

[0031] A TCU control module: used to receive the signal data sent by the driver control module, the sensing module and the engine control module, and send the speed ratio and the requested speed of the engine determined by the power matching method to the execution module and the engine control module respectively.

[0032] Compared with the prior art, the power matching system has the following beneficial effects:

[0033] The power matching method of the hydraulic mechanical continuously variable transmission tractor and the system applying the power matching method can control the engine speed and the transmission ratio of the whole machine through control logic under the premise that engine stall is avoided, meet the control requirements of the driver control system, avoid the whole machine stall caused by operation error and load mutation, and avoid damage to the transmission system caused by abnormal parking, thereby improving driving comfort. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0035] Figure 1 The power distribution system control principle diagram of the present application;

[0036] Figure 2 The working principle diagram of the hydraulic mechanical continuously variable transmission tractor of the present application;

[0037] Figure 3 The schematic diagram of the transmission route of a certain hydraulic mechanical continuously variable transmission tractor;

[0038] Figure 4 The working state schematic diagram of a single planetary gear train in a composite planetary gear train;

[0039] Figure 5 The dynamics model schematic diagram of the tractor when working;

[0040] Figure 6 The schematic diagram of the driver intention conversion;

[0041] Figure 7 The power matching method schematic diagram of the present application. DETAILED DESCRIPTION

[0042] The present application will be described in detail below through exemplary embodiments. However, it should be understood that the elements, structures and features in one embodiment can also be beneficially combined into other embodiments without further description.

[0043] It should be noted that: unless otherwise defined, the technical terms or scientific terms used herein should be understood as the usual meaning understood by those skilled in the art to which the present application belongs. The "one", "a" or "the" and similar words used in the patent application description and claims of the present application do not represent quantity limitation, but indicate the existence of at least one; The "first", "second" and "third" used in the present application should not be regarded as a limitation of the order of components, but only as a distinction between different components; The "includes" or "contains" and similar words indicate that the elements or objects appearing before "includes" or "contains" cover the elements or objects listed after "includes" or "contains" and their equivalents, but do not exclude other elements or objects with the same function.

[0044] In order to more clearly describe the specific composition of the power matching method and system of the hydraulic mechanical continuously variable transmission tractor, the attached Figures 1-7 The present embodiment is described:

[0045] The principle of the power matching method in the hydraulic mechanical continuously variable transmission tractor is:

[0046] The working principle of the continuously variable transmission tractor is shown in Figure 2 . The power of the engine is first divided into one way through the pump motor end hydraulic transmission and the other way through the gear mechanical transmission. The two power is output through the composite planetary array and output through the multi-stage gear box to drive the whole machine.

[0047] The whole machine is not shut down and parked by not exceeding the maximum torque of the engine working speed, so the speed and torque characteristics of the transmission system are calculated first.

[0048] The power distribution of the whole machine during operation is analyzed taking the power transmission system of a certain type of hydraulic mechanical continuously variable transmission tractor as an example. The route of the power transmission system is shown in Figure 3 . Ne and Te are the input speed and torque of the engine respectively; e is the displacement ratio of the pump motor system (e is defined as the output speed ratio of the constant motor to the input speed of the variable pump); K1 and K2 are clutches;

[0049] S1, S2, S3 and S4 are synchronizers; i1, i2, i3, i4, i5, i6, i7, i8, i9, i 10 , i 11 , i 12 are the speed ratio of each pair of gear (speed ratio is defined as the output speed ratio of the gear pair to the input speed of the gear pair), i c is the central transmission ratio (central transmission ratio is defined as the output speed ratio of the drive shaft to the output speed of the transmission), R w is the radius of the drive wheel.

[0050] The hydraulic mechanical continuously variable transmission realizes continuous transformation of transmission by adjusting the displacement ratio of the pump motor system and switching the composite planetary gear, and a single planetary gear working state diagram of the composite planetary gear is shown in Figure 4 s1, r1 and c1 are respectively the sun gear, ring gear and carrier of the planetary gear P1; s2, r2 and c2 are respectively the sun gear, ring gear and carrier of the planetary gear P2. Figure 4 The red component is a component for transmitting power in the working state of the planetary gear.

[0051] When the planetary gear P1 works alone, the rotational speed relationship of the sun gear s1, ring gear r1 and carrier c1 of the planetary gear P1 is as shown in formula 1:

[0052] n [5] +p1*n s1 =(1+p1)*n r1 (1)

[0053] n c1 , n s1 , n r1 are the rotational speeds of the sun gear s1, ring gear r1 and carrier c1, r / min; p1 is a constant of the planetary gear P1, and the size is the product of the ratio of the number of teeth of the ring gear r1 to the number of teeth of the gear engaged therewith and the ratio of the number of teeth of the gear engaged with the sun gear s1 to the number of teeth of the sun gear.

[0054] When the sun gear of the planetary gear P2 is the only output, the rotational speed relationship of the sun gear s2, ring gear r2 and carrier c2 of the planetary gear P2 is as shown in formula 2:

[0055] n c1 +p2*n s2 =(1+p2)*n r2 (2)

[0056] n c2 , n s2 , n r2 are the rotational speeds of the sun gear s2, ring gear r2 and carrier c2, r / min; p2 is a constant of the planetary gear P2; and the size is the ratio of the number of teeth of the ring gear r2 to the number of teeth of the sun gear s2.

[0057] When the sun gear of the planetary gear P2 is the only output, the rotational speeds on the carrier and ring gear of the planetary gear P2 are the same in size and direction as the rotational speed on the planetary gear P1, i.e. n c2 n c2＝ , n c1 , n r2＝ n r1 The rotational speed relationship of the sun gear, ring gear of the planetary gear P2 and the sun gear of the planetary gear P1 is as shown in formula 3:

[0058]

[0059] Table 1 Transmission ratio of each gear position r1 r2 r3 r4 out e n where i = i1*i2*i3*i4*i5.

[0060] Table 1 Transmission ratio of each gear position

[0061]

[0062] Transmission ratio S r＝ r (d, e), d is the gear position of the transmission.

[0063] Ignoring the friction of the transmission and the power loss of the pump motor system, the output torque of each gear position of the transmission is shown in Table 2, where T out1 out2 out3 out4 is the output torque of each gear position.

[0064] Table 2 Torque characteristics of the HMCVT

[0065]

[0066]

[0067] Transmission ratio T out＝ t (d, e, T e ), d is the gear position of the transmission.

[0068] The relationship between the vehicle speed v t and the engine speed n e is shown in Equation 4:

[0069]

[0070] where v t = f v( (d, e, n e ).

[0071] The relationship between the driving torque T t of the whole machine and the output torque T out of the transmission is shown in Equation 5:

[0072]

[0073] ​​​​​​​​​​​The whole machine driving torque T t = f t (d, e, T e ).

[0074] When the tractor is working normally, the dynamic model is as shown in Figure 5 The relationship between the driving torque T t of the tractor, the load torque T f of the tractor, the mass m of the tractor, and the acceleration a = dv t / dt of the whole machine is shown in the figure.

[0075] ma+T f =T t (6)

[0076] According to the working principle and transmission characteristics of the hydraulic mechanical continuously variable transmission tractor, a scheme for power distribution of the whole machine of the tractor is designed, which is divided into two parts: driver intention conversion and power distribution. The first part of the driver intention conversion is as shown in Figure 6 , and the steps are a, b, c, and d:

[0077] When the driver pushes the speed lever to accelerate during heavy load work, the whole machine can be accelerated by increasing the engine speed and the speed ratio of the transmission. When the engine speed is constant, the speed ratio of the transmission is increased to achieve a faster response within the performance range of the whole machine.

[0078] As shown in Figures 1-7 , a power matching method for a hydraulic mechanical continuously variable transmission tractor includes the following steps:

[0079] S1, obtaining the requested speed v r of the whole machine requested by the driver, and calculating the required torque T tr of the engine under the requested speed;

[0080] Specifically, after the tractor is powered on, the current load torque T f of the whole machine is obtained by the sensing system when the acceleration of the whole machine is zero; when the driver accelerates the whole machine through the driver control system (multifunctional handrail or accelerator pedal), the requested speed v r of the whole machine is obtained, and the requested acceleration a r is calculated according to the current requested speed v t and the current speed v r of the whole machine;

[0081] The required torque T tr of the engine under the requested speed v r is calculated according to the requested acceleration a r , the load m (mass) of the whole machine, and the load torque T f , and Ttr =k(ma r+ T f In considering the overall dynamics model, wind resistance, rolling resistance, and frictional resistance are ignored. k is the compensation coefficient for calculating the required driving torque of the whole machine. f The value of T is obtained by combining the engine torque and the actual gear ratio when the machine is moving at a constant speed. f =T ef *(i c *S rac ), S rac T represents the actual gear ratio of the transmission; ef The engine torque represents the engine torque when the entire machine was in a stable state during the previous cycle.

[0082] S2, Calculate the engine speed at the requested vehicle speed v. r The actual minimum rotational speed n pmix and the theoretical minimum engine speed n rmix Take the actual minimum speed n pmix and the theoretical minimum engine speed n rmix The larger value in n is used as the required engine speed n d ;

[0083] Among them, based on the requested vehicle speed v r Calculate the required power P r By consulting the engine external characteristics table for the entire machine, the required power P can be obtained. r The actual minimum speed n of the engine pmix n pmix =f mix (P r );

[0084] Theoretical minimum engine speed n rmix Based on the requested vehicle speed v r And the maximum gear ratio of the whole machine i c *S rmax Calculate the maximum gear ratio i of the entire machine. c *S rmax For the central transmission ratio i c and the maximum gear ratio S of the transmission rmax The product;

[0085] S3, the required rotational speed n d The initial requested engine speed n r Calculate the engine's initial requested speed n. r Maximum driving torque T rmax ;

[0086] The engine's external characteristics table is consulted to obtain the engine's speed at the requested speed n. r Maximum torque Tre , by requesting vehicle speed v r and requesting rotational speed n r , a requested gear ratio S rn is obtained; according to maximum torque T r at the requested rotational speed n re and the requested gear ratio S rn , maximum driving torque T rmax at the requested rotational speed is obtained = T re / (S rn *i c ).

[0087] S4, if maximum driving torque T r at the initial requested rotational speed n rmax is greater than or equal to the required torque T tr of the engine, it indicates that the maximum driving torque of the engine at the requested gear ratio S rn can meet the speed regulation requirement of the whole machine at the working condition, so no rotational speed compensation is needed, and the engine can be controlled according to the initial requested rotational speed n r (this time n r =n d );

[0088] If maximum driving torque T r at the initial requested rotational speed n rmax is less than the required torque T tr of the engine, it indicates that the maximum driving torque of the engine at the requested gear ratio S rn cannot meet the speed regulation requirement of the whole machine at the working condition, and rotational speed compensation is needed, if no compensation adjustment is made, the engine will be decelerated or even stalled, and the whole machine will stop, sudden stop at this state will cause damage to the engine and the transmission system, in order to avoid this phenomenon, the required rotational speed n d of the engine is compensated step by step (exemplarily, one level is divided every 1%) within the range of the maximum rotational speed of the engine (the engine has a rotational speed limit), after each level of compensation, the vehicle speed of the whole machine is made close to the requested vehicle speed n rn by reducing the requested gear ratio S r , until the vehicle speed of the whole machine is equal to the requested vehicle speed n r , then the corresponding compensated required rotational speed n d is taken as the requested rotational speed n r to control the engine, and the gear ratio is reduced until the whole machine is maintained at the requested vehicle speed n r .

[0089] According to the engine characteristics, the maximum power of the engine will also increase with the increase of the rotational speed, when the requested vehicle speed is unchanged, after the gear ratio is reduced, the maximum driving torque T rmaxThe torque will increase when the engine's maximum drive torque at the requested vehicle speed is greater than or equal to the required torque, thus preventing torque build-up due to T. rmax <T tr The engine stalled and the car stopped.

[0090] Reduce the gear ratio until the entire machine maintains the requested speed n. r The method is as follows: obtain the actual acceleration and requested acceleration of the entire machine; adjust the requested gear ratio step by step according to the requested acceleration of the entire machine and the actual rate of change of engine speed until the actual acceleration of the entire machine equals the requested acceleration; specifically, it includes the following steps:

[0091] Overall acceleration control is achieved by controlling the engine's actual speed n. ac The change yields the engine speed change rate a n =dn ac / dt, through the actual gear ratio S of the whole machine rac The change yields the actual speed ratio change rate a s =dS rac / dt, the actual acceleration S of the whole machine rac =n ac *a s +a n *S rac The entire machine requests acceleration a. r and actual acceleration a ac Feedback adjustment request speed ratio change rate a rs a rs =dS rn / dt is a method used to ensure consistency between the requested acceleration and the actual acceleration of the entire machine. Adjustment stops when the requested acceleration and the actual acceleration are consistent.

[0092] The requested gear ratio is achieved by the corresponding requested gear position and the requested displacement ratio of the pump motor (the requested displacement ratio of the pump motor is the ratio of the motor speed to the pump speed).

[0093] To cope with sudden changes and temporary increases in load, the actual torque T at the current vehicle speed is periodically acquired and compared. ac The maximum torque T at the requested speed re If T ac ≥t*T re Where t is the engine torque safety factor, 0 < t < 1, indicating that the load exceeds the control limit, then the engine speed is compensated step by step within the maximum engine speed range; if T ac <t*T re Then no speed compensation is needed.

[0094] If the compensated demand rotating speed exceeds the maximum rotating speed of the engine before the engine is controlled by the request rotating speed, the lift arm is lifted step by step (for example, one step is 10% of the range from low to high) in the working range of the lift arm to reduce the load until the whole machine maintains the request vehicle speed and the maximum driving torque of the engine is greater than or equal to the demand torque; if the compensated demand rotating speed does not exceed the maximum rotating speed of the engine, the height of the lift arm does not need to be changed.

[0095] A power matching system of a hydraulic mechanical continuously variable transmission tractor, comprising:

[0096] The driver control module mainly comprises a multifunctional control handrail and an accelerator pedal, and is used for obtaining the request vehicle speed of the driver to the whole machine and transmitting the obtained signal data to the TCU control module.

[0097] The sensing module is a sensor, and is used for obtaining the load, vehicle speed and torque of the whole machine and transmitting the obtained signal data to the TCU control module.

[0098] The execution module mainly comprises an electromagnetic valve of a clutch, a synchronizer and a variable pump, and is used for receiving and executing the transmission ratio sent by the TCU control module to maintain the whole machine at the request vehicle speed.

[0099] The engine control module is used for receiving and executing the request rotating speed sent by the TCU control module, and feeding back the current rotating speed and torque of the engine to the TCU control module.

[0100] The TCU control module is used for receiving the signal data sent by the driver control module, the sensing module and the engine control module, and sending the transmission ratio determined by any power matching method and the request rotating speed of the engine to the execution module and the engine control module respectively.

[0101] The parts not described in detail in the above embodiments are prior art.

[0102] It should be noted that although the present application is described by the above embodiments, the present application can have other various embodiments. Those skilled in the art can make various corresponding changes and modifications to the present application without departing from the spirit and scope of the present application, and these changes and modifications should belong to the scope of the appended claims and equivalents thereof.

Claims

1. A power matching method for a hydraulic mechanical continuously variable transmission tractor, characterized in that: Obtain the driver's requested vehicle speed and calculate the engine's required torque at that speed; Calculate the actual minimum engine speed and the theoretical minimum engine speed at the requested vehicle speed, and take the larger value between the actual minimum engine speed and the theoretical minimum engine speed as the required engine speed. The required speed is used as the initial requested speed of the engine, and the maximum driving torque of the engine at the initial requested speed is calculated. If the maximum drive torque at the initial requested speed is greater than or equal to the engine's required torque, then the engine is controlled according to the initial requested speed. If the maximum driving torque at the initial requested speed is less than the engine's required torque, then the engine's required speed is compensated step by step within the engine's maximum speed range, and the compensated required speed is used as the requested speed to control the engine, and the gear ratio is reduced in coordination until the whole machine is maintained at the requested vehicle speed. At this time, the engine's maximum driving torque at the requested vehicle speed is greater than or equal to the required torque.

2. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 1, characterized in that, The calculation of the engine torque required at the requested vehicle speed includes: Obtain the load torque when the overall machine acceleration is zero; Get the requested vehicle speed input by the driver and the current vehicle speed of the whole machine, and calculate the requested acceleration based on the requested vehicle speed and the current vehicle speed; Calculate the engine's required torque at the requested vehicle speed based on the requested acceleration, total load, and load torque.

3. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 1, characterized in that, The calculation of the engine's actual minimum speed at the requested vehicle speed includes: Calculate the required power based on the requested vehicle speed, and then query the engine external characteristic table of the whole machine to obtain the actual minimum speed of the engine under the required power.

4. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 1, characterized in that: The theoretical minimum engine speed is calculated based on the requested vehicle speed and the maximum gear ratio of the whole machine, where the maximum gear ratio of the whole machine is the product of the central transmission ratio and the maximum gear ratio of the gearbox.

5. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 1, characterized in that, The calculation of the engine's maximum drive torque at the requested speed includes: Query the engine external characteristics table of the whole machine to obtain the maximum torque of the engine at the requested speed, and obtain the requested gear ratio by using the requested vehicle speed and the requested speed; The maximum drive torque at the requested speed is obtained by using the maximum torque at the requested speed and the requested gear ratio.

6. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 5, characterized in that: Periodically acquire and compare the actual torque T at the current vehicle speed ac The maximum torque T at the requested speed re If T ac ≥t*T re Where t is the engine torque safety factor, 0 < t < 1, then the engine speed compensation is performed step by step within the range of the engine's maximum speed; if T ac <t*T re Then no speed compensation is needed.

7. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 1, characterized in that: Before controlling the engine with the compensated required speed as the requested speed, if the compensated required speed exceeds the engine's maximum speed, the lifting arm is raised step by step within the working stroke range of the lifting arm to reduce the load until the whole machine maintains the requested speed and the engine's maximum drive torque is greater than or equal to the required torque; if the compensated required speed does not exceed the engine's maximum speed, there is no need to change the lifting arm height.

8. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 5, characterized in that, Collaboratively reduce the gear ratio until the entire machine maintains the requested speed, including: Obtain the actual acceleration and requested acceleration of the entire machine; The requested gear ratio is adjusted step by step according to the requested acceleration of the whole machine and the actual rate of change of engine speed, until the actual acceleration of the whole machine equals the requested acceleration.

9. A power matching system for a hydraulic mechanical continuously variable transmission tractor, characterized in that, include: Driver control module: used to acquire the driver's requested vehicle speed and transmit the acquired signal data to the TCU control module; Sensing module: Used to acquire the load, speed and torque of the whole machine, and transmit the acquired signal data to the TCU control module; Execution module: Used to receive and execute the gear ratio sent by the TCU control module, so that the whole machine maintains the requested speed; Engine control module: Used to receive and execute the requested speed sent by the TCU control module, and at the same time feed back the current engine speed and torque to the TCU control module; TCU control module: used to receive signal data from the driver control module, the sensing module and the engine control module, and send the gear ratio determined by the power matching method as described in any one of claims 1-8 and the requested engine speed to the execution module and the engine control module respectively.

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