阅读说明：本技术 一种用于轮式拖拉机耕作作业的变速控制方法 (Speed change control method for tillage operation of wheeled tractor ) 是由 夏光 杨猛 张亮 王跃强 纵华宇 李嘉诚 于星海 钱峰 陈建杉 夏岩 于 2020-05-28 设计创作，主要内容包括：本发明公开了一种用于轮式拖拉机耕作作业的变速控制方法,是根据拖拉机作业时不同的驱动轮滑转率,进行变速器动力换挡与耕深调节控制；当驱动轮滑转率处在正常范围时,通过对拖拉机变速器进行动力换挡调节驱动力从而控制滑转率处于最佳范围；当驱动轮滑转率超出合理的范围时,通过机具耕深调节控制,使驱动轮滑转率保持在正常范围。本发明能使驱动轮滑转率处于最佳范围,从而使拖拉机具有较高的牵引效率,同时避免产生过大的摩擦功率损失、驱动轮磨损和田间土壤结构破坏。(The invention discloses a variable speed control method for tillage operation of a wheeled tractor, which is used for carrying out power gear shifting and tillage depth adjustment control on a transmission according to different driving wheel slip rates during the operation of the tractor; when the slip ratio of the driving wheel is in a normal range, the slip ratio is controlled to be in an optimal range by performing power gear shifting on a transmission of the tractor to adjust driving force; when the slip ratio of the driving wheel exceeds a reasonable range, the slip ratio of the driving wheel is kept in a normal range through the tillage depth adjustment control of the machine tool. The invention can make the slip ratio of the driving wheel in the optimum range, thereby the tractor has higher traction efficiency, and simultaneously avoids generating excessive friction power loss, driving wheel abrasion and field soil structure damage.)

1. A shift control method for a wheeled tractor tilling operation, comprising:

when the slip ratio a of the driving wheel is less than or equal to d, performing transmission power gear shifting control on the wheel-type tractor according to the opening degree alpha of an engine accelerator and the slip ratio of the driving wheel, and maintaining the slip ratio of the driving wheel within an optimal interval [ b, c ] to achieve high traction efficiency;

when the slip ratio of the driving wheel is larger than d, the machine depth of tillage of the wheeled tractor is adjusted and controlled, so that the slip ratio of the driving wheel is reduced to a reasonable interval [ a, d ];

wherein, the lower limit b in the optimal interval [ b, c ] has a value range of [ 8%, 10% ], and the upper limit c has a value range of [ 12%, 15% ];

the lower limit of the reasonable interval [ a, d ] is 0%, and the upper limit d is in the range of [ 20%, 25% ].

2. The shift control method according to claim 1, characterized in that: the transmission power shift control includes:

when the opening of the engine throttle α∈ [ α ]₁，α₂) And the drive wheel slip ratio ∈ [ a, b), then the transmission power shift control is held in gear;

when the opening of the engine throttle α∈ [ α ]₂，α₄]And the drive wheel slip ratio is ∈ [ a, b), then the transmission power shift control is to implement a power downshift control;

when the opening of the engine throttle α∈ [ α ]₁，α₄]And the drive wheel slip ratio is ∈ [ b, c), then the transmission power shift control is to maintain gear;

when the opening of the engine throttle α∈ [ α ]₁，α₃) And the slip ratio of the driving wheels ∈ [ c, d]If so, the power gear shifting control of the transmission is to implement power gear-up control;

when the opening of the engine throttle α∈ [ α ]₃，α₄]Said drive wheel slip ratio ∈ [ c, d]When the gear is in the shift range, the power shift control of the transmission is to keep the gear;

wherein, the value ranges of four parameters in the interval to which the engine throttle opening α belongs are α₁∈[25％，30％]，α₂∈[50％，55％]，α₃∈[75％，80％]，α₄＝100％。

3. The shift control method according to claim 1, characterized in that: the tilling depth adjustment control of the machine tool is as follows:

when the slip ratio of the driving wheel is larger than d, the tilling depth of the machine tool is reduced by lifting the position of the machine tool so as to reduce the operation resistance and further reduce the slip ratio of the driving wheel.

4. The shift control method according to claim 2, wherein the execution of the power upshift control is performed as follows:

step (ii) of1. At a time period t_u1～t_u2Internal high clutch oil pressure is shifted from upshift start oil pressure p_u0Up to the upshift contact oil pressure p_u1And the low range clutch oil pressure is maintained at the lockup oil pressure p_lock(ii) a Wherein, t_u1，t_u2For upshifting the first and second time nodes, and t_u2>t_u1(ii) a The starting oil pressure p of the upshift_u0Oil pressure balanced with the return spring force; the upshift contact oil pressure p_u1The pressure required for the clutch to eliminate the clearance of the driving plate and the driven plate; the lock oil pressure p_lockOil pressure to prevent accidental slipping of the clutch;

step 2, in the time period t_u2～t_u3Internally, the high clutch oil pressure is brought into contact with the oil pressure p from the upshift_u1Transition oil pressure p for upshift_u2And the low clutch oil pressure is maintained at the lockup oil pressure p_lock；

At t_u3At the moment, the low clutch oil pressure is driven to the lockup oil pressure p_lockSuddenly dropping to the initial oil pressure p of gear-up_u0；

Wherein, t_u3Is an upshift of a third time node, and t_u3>t_u2(ii) a The upshift transition oil pressure p_u2Friction torque transmitted for upshifting clutch is equal to load torque T of speed changer_LClutch pressure required;

step 3, in the time period t_u3～t_u4Internal, upshift transition oil pressure p for high clutch oil pressure_u2Oil pressure p to the end of upshift_u3And the low clutch oil pressure is maintained at the upshift start oil pressure p_u0；

At t_u4At the moment, the high clutch oil pressure is changed from the upshift end oil pressure p_u3Jump to lock-up oil pressure p_lock(ii) a Wherein, t_u4Is to upshift the fourth time node, and t_u4>t_u3。

5. The shift control method according to claim 2, wherein the execution of the power downshift control is performed by:

step 1, at t_d1Constantly slave lock-up clutch pressure p to high range clutch pressure_lockSuddenly dropping to gear-down critical oil pressure p_d2；

At a time period t_d1～t_d2Internally, the low clutch oil pressure is maintained at the downshift start oil pressure p_d0And the oil pressure of the high-gear clutch is continuously reduced; wherein, t_d1，t_d2For downshifting first and second time nodes, and t_d2>t_d1(ii) a The downshift critical oil pressure p_d2Oil pressure for bringing the high clutch into a critical state of engagement and slipping;

step 2, in the time period t_d2～t_d3Internally, the low clutch oil pressure is reduced from the initial oil pressure p_d0Up to the downshift contact oil pressure p_d1And the oil pressure of the high-gear clutch is continuously reduced; wherein, t_d3A third time node for downshift, and t_d3>t_d2；

Step 3, in the time period t_d3～t_d4In the inner part, the low clutch oil pressure is continuously increased, and the high clutch oil pressure is t_d4Constantly decreasing to the downshift start oil pressure p_d0(ii) a Wherein, t_d4Is a fourth time node of downshift, and t_d4>t_d3；

Step 4, in the time period t_d4～t_d5Internally raising the low range clutch oil pressure to the downshift terminal oil pressure p_d3And the high clutch is maintained at the downshift start oil pressure p_d0The change is not changed;

at t_d5At the moment, the low clutch oil pressure is controlled to be the final oil pressure p of the downshift_d3Jump to lock-up oil pressure p_lock(ii) a Wherein, t_d5Is a downshift at a fifth time node, and t_d5>t_d4。

Technical Field

The invention relates to the field of power transmission control of tractors, in particular to a speed change control method for ensuring continuous high-quality farming operation of a wheeled tractor.

Technical Field

The method improves the agricultural production efficiency and quality, and has great significance for guaranteeing the national basic material living demand and improving the material living level.

When the tractor operates in the field, the driving wheel generates shear strain to soil, so that the driving wheel always has certain slip rate when the tractor operates. When the slip rate is too high, the friction between the driving wheels and the ground can generate power loss, and meanwhile, the abrasion of the driving wheels is aggravated, the soil structure in the field is damaged, the wheels sink, and the rolling resistance of the tractor is increased. In addition, a certain relation exists between the slip ratio of the driving wheels and the traction efficiency of the tractor, and if the slip ratio of the driving wheels is in an unreasonable range, the traction efficiency of the tractor is low, so that the economy and the dynamic performance of the tractor are poor.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a speed change control method for the tillage operation of a wheeled tractor, so that the slip ratio of a driving wheel is in an optimal range, the tractor has higher traction efficiency, and excessive friction power loss, driving wheel abrasion and field soil structure damage can be avoided.

The invention adopts the following technical scheme for solving the technical problems:

the invention relates to a speed change control method for tillage operation of a wheeled tractor, which is characterized by comprising the following steps:

when the slip ratio a of the driving wheel is less than or equal to d, performing transmission power gear shifting control on the wheel-type tractor according to the opening degree alpha of an engine accelerator and the slip ratio of the driving wheel, and maintaining the slip ratio of the driving wheel within an optimal interval [ b, c ] to achieve high traction efficiency;

when the slip ratio of the driving wheel is larger than d, the machine depth of tillage of the wheeled tractor is adjusted and controlled, so that the slip ratio of the driving wheel is reduced to a reasonable interval [ a, d ];

wherein, the lower limit b in the optimal interval [ b, c ] has a value range of [ 8%, 10% ], and the upper limit c has a value range of [ 12%, 15% ];

the lower limit of the reasonable interval [ a, d ] is 0%, and the upper limit d is in the range of [ 20%, 25% ].

The shift control method according to the present invention is also characterized in that: the transmission power shift control includes:

when the opening of the engine throttle α∈ [ α ]₁，α₂) And the drive wheel slip ratio ∈ [ a, b), then the transmission power shift control is held in gear;

when the opening of the engine throttle α∈ [ α ]₂，α₄]And the drive wheel slip ratio is ∈ [ a, b), then the transmission power shift control is to implement a power downshift control;

when the opening of the engine throttle α∈ [ α ]₁，α₄]And the drive wheel slip ratio is ∈ [ b, c), then the transmission power shift control is to maintain gear;

when the opening of the engine throttle α∈ [ α ]₁，α₃) And the slip ratio of the driving wheels ∈ [ c, d]If so, the power gear shifting control of the transmission is to implement power gear-up control;

when the opening of the engine throttle α∈ [ α ]₃，α₄]Said drive wheel slip ratio ∈ [ c, d]When the gear is in the shift range, the power shift control of the transmission is to keep the gear;

wherein, the value ranges of four parameters in the interval to which the engine throttle opening α belongs are α₁∈[25％，30％]，α₂∈[50％，55％]，α₃∈[75％，80％]，α₄＝100％。

The tilling depth adjustment control of the machine tool is as follows:

when the slip ratio of the driving wheel is larger than d, the tilling depth of the machine tool is reduced by lifting the position of the machine tool so as to reduce the operation resistance and further reduce the slip ratio of the driving wheel.

The implementation of the power upshift control is performed according to the following steps:

step 1, in a time period t_u1～t_u2Internal high clutch oil pressure is shifted from upshift start oil pressure p_u0Up to the upshift contact oil pressure p_u1And the low range clutch oil pressure is maintained at the lockup oil pressure p_lock(ii) a Wherein, t_u1，t_u2For upshifting the first and second time nodes, and t_u2>t_u1(ii) a The starting oil pressure p of the upshift_u0Oil pressure balanced with the return spring force; the upshift contact oil pressure p_u1The pressure required for the clutch to eliminate the clearance of the driving plate and the driven plate; the lock oil pressure p_lockOil pressure to prevent accidental slipping of the clutch;

step 2, in the time period t_u2～t_u3Internally, the high clutch oil pressure is brought into contact with the oil pressure p from the upshift_u1Transition oil pressure p for upshift_u2And the low clutch oil pressure is maintained at the lockup oil pressure p_lock；

At t_u3At the moment, the low clutch oil pressure is driven to the lockup oil pressure p_lockSuddenly dropping to the initial oil pressure p of gear-up_u0；

Wherein, t_u3Is an upshift of a third time node, and t_u3>t_u2(ii) a The upshift transition oil pressure p_u2For upshifting high gearThe slip torque transmitted by the clutch is equal to the variator load torque T_LClutch pressure required;

step 3, in the time period t_u3～t_u4Internal, upshift transition oil pressure p for high clutch oil pressure_u2Oil pressure p to the end of upshift_u3And the low clutch oil pressure is maintained at the upshift start oil pressure p_u0；

At t_u4At the moment, the high clutch oil pressure is changed from the upshift end oil pressure p_u3Jump to lock-up oil pressure p_lock(ii) a Wherein, t_u4Is to upshift the fourth time node, and t_u4>t_u3。

The implementation of the power downshift control is performed according to the following steps:

step 1, at t_d1Constantly slave lock-up clutch pressure p to high range clutch pressure_lockSuddenly dropping to gear-down critical oil pressure p_d2；

At a time period t_d1～t_d2Internally, the low clutch oil pressure is maintained at the downshift start oil pressure p_d0And the oil pressure of the high-gear clutch is continuously reduced; wherein, t_d1，t_d2For downshifting first and second time nodes, and t_d2>t_d1(ii) a The downshift critical oil pressure p_d2Oil pressure for bringing the high clutch into a critical state of engagement and slipping;

step 2, in the time period t_d2～t_d3Internally, the low clutch oil pressure is reduced from the initial oil pressure p_d0Up to the downshift contact oil pressure p_d1And the oil pressure of the high-gear clutch is continuously reduced; wherein, t_d3A third time node for downshift, and t_d3>t_d2；

Step 3, in the time period t_d3～t_d4In the inner part, the low clutch oil pressure is continuously increased, and the high clutch oil pressure is t_d4Constantly decreasing to the downshift start oil pressure p_d0(ii) a Wherein, t_d4Is a fourth time node of downshift, and t_d4>t_d3；

Step 4, in the time period t_d4～t_d5Internal low clutch oilPressure rise to downshift terminal oil pressure p_d3And the high clutch is maintained at the downshift start oil pressure p_d0The change is not changed;

at t_d5At the moment, the low clutch oil pressure is controlled to be the final oil pressure p of the downshift_d3Jump to lock-up oil pressure p_lock(ii) a Wherein, t_d5Is a downshift at a fifth time node, and t_d5>t_d4。

Compared with the prior art, the invention has the beneficial effects that:

1. the invention grades the slip ratio of the driving wheel of the tractor, and ensures the passing performance of the tractor by adjusting the tilling depth of the tractor when the slip ratio is in an unreasonable interval; when the slip ratio is in a reasonable interval but not in an optimal interval, the power gear shifting operation is carried out on the tractor to enable the slip ratio of the driving wheel to be in the optimal interval, so that the tractor has higher traction efficiency, and the tilling depth of the tractor is not adjusted at the moment, and the operation quality of the tractor is improved.

2. The invention adopts two parameters of the slip ratio of the driving wheel and the opening degree of the accelerator of the engine, and accurately judges the ground adhesion condition of the tractor during operation, thereby formulating a reasonable power gear shifting control scheme and controlling the slip ratio of the driving wheel in an optimal interval on the premise of ensuring the dynamic property of the tractor.

3. According to the invention, the actuating time sequence of the clutch in the gear shifting process of the power gear shifting transmission is reasonably controlled, so that the rotating speed of the driving disc is always greater than that of the driven disc when the clutch slides, and the power circulation phenomenon in the gear shifting process is effectively avoided.

Drawings

FIG. 1 is a graph of driving force versus drive wheel slip ratio in accordance with the present invention;

FIG. 2 is a graph of slip rate versus traction efficiency for different soil conditions in accordance with the present invention;

FIG. 3 is a schematic representation of a powershift transmission of the present invention;

FIG. 4 is a graph of clutch actuation pressure change during a power upshift in accordance with the present invention.

FIG. 5 is a graph showing the variation of clutch actuation pressure during a power downshift according to the present invention.

Detailed Description

In the embodiment, the speed change control method for the tillage operation of the wheeled tractor divides the slip ratio of the driving wheels of the tractor into a reasonable interval and an optimal interval, judges the operation resistance of the tractor and the ground adhesion condition according to the opening degree alpha of an accelerator and the slip ratio of the driving wheels when the slip ratio is in the reasonable interval, performs power gear shift control capable of avoiding power circulation on the tractor, and controls the slip ratio of the driving wheels in the optimal interval on the premise of ensuring the dynamic property of the tractor, so that the tractor has higher traction efficiency; when the slip rate exceeds a reasonable interval, the tilling depth of the tractor is adjusted, so that the slip rate of the driving wheel is reduced to be within the reasonable interval, the power loss generated by friction between the driving wheel and the ground is reduced, and the driving wheel is prevented from being excessively abraded.

Specifically, referring to fig. 1-5, the shift control method is performed as follows:

as can be seen from figure 1, when the slip ratio of the driving wheel is smaller, the slip ratio and the driving force are approximately in a direct proportion relation, therefore, when the slip ratio a of the driving wheel is less than or equal to d, the operation resistance and the ground adhesion condition of the tractor can be judged according to the opening degree alpha of the accelerator of the engine and the slip ratio of the driving wheel, and the power gear shifting control of the transmission is carried out on the wheel type tractor, so that the driving force of the driving wheel can be adjusted, and the slip ratio of the driving wheel can be maintained in an optimal interval [ b, c ] through reasonable control, so as to achieve high traction efficiency;

specifically, the transmission power shift control includes:

when the engine throttle opening α∈ [ α ]₁，α₂) When the driving wheel slip ratio ∈ [ a, b) is in small throttle opening and small slip ratio, which shows that the tractor has small working resistance and good ground adhesion condition, if the down shift control is carried out, the driving force can be increased and the slip ratio can be increased to the optimum range, however, because the current working resistance is small, the driving force is increased and the tractor is accelerated to the up shift working speed, so as to cause the shift cycle, and the comprehensive consideration is that the power of the speed changerThe gear shifting control is to keep a gear;

when the engine throttle opening α∈ [ α ]₂，α₄]And when the slip ratio of the driving wheel ∈ [ a, b) is, the tractor is in the opening of the throttle valve with medium or large opening and small slip ratio, the working resistance is medium and large under the working condition, the ground attachment condition is good, the downshift control can be carried out, namely, the dynamic property of the tractor is improved, the tractor is helped to overcome the working resistance, and the slip ratio of the tractor can be in the best interval, the power shift control of the transmission is the power downshift control, referring to fig. 3, the H gear downshift and the L gear downshift are taken as examples, and the power downshift control is carried out according to the following steps by combining with fig. 5:

step 1, at t_d1At the moment, to shorten the shift time, the D oil pressure of the high clutch is changed from the lockup oil pressure p_lockSuddenly dropping to gear-down critical oil pressure p_d2Switching the clutch D from the combination state to the friction state;

the rotation speed omega of the driven disc of the low-gear clutch C at the beginning of the gear reduction_C2Greater than the rotation speed omega of the driving disk_C1To prevent the driven disk of the low clutch C from rotating the driving disk, a power cycle is generated, so that the time period t is set_d1～t_d2The oil pressure of the low clutch C is maintained at the downshift start oil pressure p_d0Keeping the low clutch C in a disengaged state; in order to increase the rotation speed of the driving disk of the low-gear clutch C, decrease the rotation speed of the driven disk, continuously decrease the oil pressure of the high-gear clutch D, and output rotation speed omega of the transmission along with the fact that the friction torque transmitted by the clutch D cannot overcome the load torque_vThe rotation speed omega of the driven disc of the low-gear clutch C begins to fall_C2Then the speed is reduced; engine speed omega_eGradually increased low-gear clutch C driving disc rotating speed omega_C1With a consequent increase in t_d2Time omega_C1＝ω_C2Proceed to step 2. Wherein, t_d1，t_d2Is a first, a second time node, and t_d2>t_d1(ii) a Lock-up oil pressure p_lockOil pressure to prevent accidental slipping of the clutch; downshift critical oil pressure p_d2Oil pressure for bringing the high clutch into a critical state of engagement and slipping;

step 2, since at t_d2The rotation speeds of the main plate and the auxiliary plate of the low-gear clutch C are synchronous at the moment, so that the power cycle cannot be generated when the clutch C is contacted at the moment, and the time period t_d2～t_d3Internal low clutch C oil pressure is reduced from the downshift start oil pressure p_d0Up to the downshift contact oil pressure p_d1At this time, because the oil pressure of the low-gear clutch C is low, although the rotation speeds of the main disc and the auxiliary disc of the low-gear clutch C are synchronous at this time, the low-gear clutch C cannot be switched to the engaged state, so that the low-gear clutch C is switched from the disengaged state to the slipping state at this stage, and the oil pressure D of the high-gear clutch continues to be reduced; wherein, t_d3Is a third time node, and t_d3>t_d2；

Step 3, in the time period t_d3～t_d4In the initial stage, because the oil pressure on the low-gear clutch C is low, the sum of the friction torque transmitted by the low-gear clutch C and the friction torque transmitted by the high-gear clutch D can not overcome the load torque, and therefore the rotating speed omega of the driving disk of the low-gear clutch C is higher than the rotating speed omega of the driving disk of the high-gear clutch D_C1Continuously increasing the rotating speed omega of the driven disc_C2Continue to decrease, ω_C1＞ω_C2When the sum of the slip torques transmitted by the low clutch C and the high clutch D exceeds the transmission load torque, the clutch C driving disc rotation speed ω is set to be higher than the transmission load torque_C1Starting to decrease, the speed of rotation omega of the driven disk_C2The speed difference of the main driving disk and the driven disk of the low-gear clutch C is gradually reduced after the speed is increased, and the oil pressure of the high-gear clutch is t_d4Constantly decreasing to the downshift start oil pressure p_d0The high-gear clutch D is switched from a friction sliding state to a separation state, and the low-gear clutch C starts to transmit power before the high-gear clutch D is separated, so that the power of the transmission is not interrupted in the gear shifting process; wherein, t_d4Is a fourth time node, and t_d4>t_d3；

Step 4, in the time period t_d4～t_d5And when the oil pressure of the low-gear clutch C rises to the gear-down terminal oil pressure p, the rotation speed difference of the main driving disc and the driven disc of the low-gear clutch C is smaller and smaller_d3Time, low clutch CThe rotation speeds of the main driving plate and the driven plate are synchronous, the low-gear clutch C is switched to a combined state from a friction state, and the high-gear clutch is kept at a gear-down starting oil pressure p_d0Keeping the high clutch D in a separated state;

at t_d5At the moment, in order to prevent the accidental slipping of the clutch caused by the sudden change of the engine torque, the low-gear clutch oil pressure is changed from the downshift terminal oil pressure p_d3Jump to lock-up oil pressure p_lock(ii) a Wherein, t_d5Is a fifth time node, and t_d5>t_d4；

When the engine throttle opening α∈ [ α ]₁，α₄]When the slip ratio of the driving wheels is ∈ [ b, c), the tractor is in the optimal slip ratio range and has higher traction efficiency, and the power shift of the transmission is controlled to be kept in a gear;

when the engine throttle opening α∈ [ α ]₁，α₃) And the slip ratio of the driving wheels ∈ [ c, d ]]When the tractor is in a middle and small accelerator opening degree and a large slip ratio, the working resistance is medium and small, the ground adhesion condition is poor, the gear is shifted up to reduce the driving force, the slip ratio is further reduced to an optimal interval to fully exert the traction efficiency of the tractor, and the power gear shifting control of the transmission is the power gear shifting control; referring to fig. 3, taking the L-range upshift and the H-range upshift as an example, in combination with fig. 4, specifically, the power upshift control is implemented according to the following steps:

step 1, in a time period t_u1～t_u2Internal high clutch D oil pressure is shifted from the starting oil pressure p_u0Up to the upshift contact oil pressure p_u1The high-gear clutch D is switched from a disengaged state to a slipping state, and the low-gear clutch C is maintained at a lock-up oil pressure p to avoid a power circulation phenomenon caused by the simultaneous slipping of the low-gear clutch C and the high-gear clutch D_lockThe low clutch C is kept in the engaged state; wherein, t_u1，t_u2For upshifting the first and second time nodes, and t_u2>t_u1(ii) a Starting oil pressure p of gear-up_u0Oil pressure balanced with the return spring force; upshift contact oil pressure p_u1For clutches with elimination of driving and driven platesThe pressure required for the gap; lock-up oil pressure p_lockOil pressure to prevent accidental slipping of the clutch;

step 2, in the time period t_u2～t_u3Internal high clutch D oil pressure is contacted with oil pressure p from upshift_u1Transition oil pressure p for upshift_u2The control oil pressure of the high clutch D is gradually increased, the slip torque transmitted is gradually increased, the power flow is shifted from the low clutch C to the high clutch D, and the oil pressure of the low clutch C is maintained at the lockup oil pressure p_lockThe low clutch C is kept in the engaged state;

t_u3the slip torque delivered by the time-high clutch D is equal to the transmission load torque T_LAt this time, the low clutch C transmission torque is reduced to 0, and the power transfer is completed, at t_u3At that time, the low clutch C oil pressure is driven from the lockup oil pressure p_lockSuddenly dropping to the initial oil pressure p of gear-up_u0The low-gear clutch C is directly switched to a separation state from a combination state, and because the condition that the low-gear clutch C and the high-gear clutch D are simultaneously worn does not exist, the power circulation phenomenon cannot be generated in the power upshift process;

wherein, t_u3Is an upshift of a third time node, and t_u3>t_u2(ii) a Upshift transition oil pressure p_u2Friction torque transmitted for upshifting clutch is equal to load torque T of speed changer_LClutch pressure required;

step 3, in the time period t_u3～t_u4And continuously increasing the control oil pressure of the high-gear clutch D to enable the torque transmitted by the high-gear clutch D to be larger than the load torque T of the transmission_LThe operation speed of the tractor rises, and the rotating speed omega of the driven disc of the high-gear clutch_D2Then the size is increased; at this time, the engine torque cannot overcome the slip torque transmitted by the high-gear clutch D, and the engine speed ω is_eDescending and high-gear clutch driving disc rotating speed omega_D1The rotation speed of the master/slave disk of the high clutch D is gradually made to be consistent with the rotation speed of the slave disk, and when the oil pressure of the high clutch is increased from the upshift to the transition oil pressure p_u2Oil pressure p to the end of upshift_u3In time, the high-gear clutch D synchronizes the rotating speeds of the main and the secondary driving disks, and the high gear isThe clutch D is switched from the slipping state to the engaged state, and the oil pressure of the low clutch C is maintained at the upshift start oil pressure p_d0The low clutch C is kept in a disengaged state;

at t_u4At the moment, in order to prevent the unexpected sliding friction of the clutch caused by the sudden change of the engine torque, the oil pressure of the high-gear clutch D is increased from the gear-up terminal oil pressure p_u3Jump to lock-up oil pressure p_lock(ii) a Wherein, t_u4Is to upshift the fourth time node, and t_u4>t_u3。

When the engine throttle opening α∈ [ α ]₃，α₄]Drive wheel slip ratio ∈ [ c, d [ ]]When the tractor is in a large throttle opening and a large slip ratio, the operation resistance is large, if the tractor is subjected to upshift control, the tractor can not overcome the operation resistance, and if the tractor is subjected to downshift control, the slip ratio of a driving wheel can exceed a reasonable range, so that the power gear shifting of the transmission is controlled to keep the gear;

the four parameters in the interval of the engine accelerator opening α are selected from the group consisting of tractor operation resistance, resistance which cannot be overcome if the accelerator opening is small, and the lower limit α of the small accelerator opening₁α according to soil conditions₁∈[25％，30％]α are provided for dividing the accelerator opening into three levels of large, medium and small₂∈[50％，55％]，α₃∈[75％，80％]，α₄In the present example, α₁、α₂And α₃Is preferably α₁＝30％，α₂＝50％，α₃＝80％。

As can be seen from fig. 1, when the slip ratio of the driving wheel exceeds a certain value, the slight increase of the driving force will result in a sharp increase of the slip ratio, which indicates that the ground is damaged at the slip ratio and is no longer suitable for the operation of the tractor, and at this time, the transmission is controlled so as not to meet the requirement, so that when the slip ratio of the driving wheel is greater than d, in order to reduce the slip ratio of the driving wheel to within the reasonable interval [ a, d ] and thereby reduce the power loss and the tire wear, the machine and tool tilling depth adjustment control is performed on the wheel tractor so as to reduce the slip ratio of the driving wheel to within the reasonable interval [ a, d ];

specifically, the machine tool tilling depth adjustment control means: when the slip ratio of the driving wheel is larger than d, the slip ratio of the driving wheel exceeds a reasonable interval, the soil structure is damaged, the tire is seriously worn, and the tilling depth of the machine tool is reduced by lifting the position of the machine tool so as to reduce the operation resistance and further reduce the slip ratio of the driving wheel.

According to the method shown in fig. 2, according to the slip ratio intervals corresponding to high traction efficiency under different soil conditions during field cultivation of the tractor, the lower limit b value range and the upper limit c value range in the optimal interval [ b, c ] are set to be [ 8% and 10% ], and the upper limit c value range is set to be [ 12% and 15% ]; in this embodiment, the optimal values of b and c are b 10% and c 15%.

Because the soil can produce shear strain when the tractor drives, the slip rate of the tractor is always more than or equal to 0 when the tractor works, the lower limit a in the reasonable interval [ a, d ] is set to be 0%, because the slip rate of the driving wheel of the tractor when the tractor works in dry farmland should not exceed 20%, and the slip rate of the driving wheel when the tractor works in paddy field should not exceed 25%, the upper limit d in the reasonable interval [ a, d ] has a value range of [ 20%, 25% ]accordingto the difference of soil humidity. In this embodiment, the optimal value of d is 20%.