Power shifting gearbox gear control method, power control system and tractor

Abstract

The invention provides a power shifting gearbox gear control method, a power control system and a tractor. In the gear control process, a TCU (Transmission Control Unit) can calculate the theoretical engine rotating speed under each gear under the real-time vehicle speed according to the real-time vehicle speed, and select the optimal gear based on the theoretical engine rotating speed under each gear and the real-time engine rotating speed; after the gearbox is reengaged, the rotating speed fluctuation of the engine is small, the whole vehicle has no obvious impact, and the problem of overspeed or flameout of the engine is avoided; meanwhile, through cab instrument display or a light buzzer and the like, a driver is reminded of the whole vehicle state, next manual operation is guided, an engine and a gearbox are protected, and the safety of whole vehicle running and operation is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural engineering machinery control, and in particular to a power shift gearbox gear control method, a power control system and a tractor. Background Art

[0002] With the full domestication of automation and the electrification and intellectualization of agricultural engineering machinery, higher requirements are put forward for its performance. As a core component of the transmission system, the power shift gearbox can support the tractor to achieve shift without power interruption, improve the operation efficiency of the tractor, and interact with the whole vehicle through the TCU to realize the intelligent control of the whole vehicle. However, at present, tractors equipped with power shift gearboxes basically retain the clutch pedal. Under certain specific working conditions, the clutch pedal can assist the driver to cut off the power of the whole vehicle or precisely control the vehicle speed. However, when the tractor is driving on a slope or under the condition of load change, when the clutch pedal is disengaged and engaged again, it may cause the engine to overspeed or stall, thus affecting the driving safety and the smoothness of power connection.

[0003] Chinese Patent Publication No. CN114347989A discloses a vehicle speed control method and device. When a sudden increase in load is detected, the required vehicle speed is reduced to reduce the transmission ratio, so that the engine provides more power to the load for dragging, realizing the smoothness of the whole vehicle under the condition of sudden increase in load, and avoiding the whole vehicle returning to neutral gear due to the rapid change of the engine speed triggering the anti-stall function. After the load decreases, the required vehicle speed of the whole vehicle is restored to resume normal operation.

[0004] Chinese Patent Publication No. CN117901872A discloses a protection method for a tractor under a heavy load state and related equipment. By detecting the real-time engine speed under the heavy load state, when reaching the stall threshold, the gearbox state is obtained, and it is determined that the operating state meets the preset state, and then the gearbox gear is switched to the target value, and the connection between the gearbox and the engine is disconnected, so that the engine enters a stalled state, thereby preventing the engine from stalling. However, after the driver manually operates, the vehicle can resume driving and operating.

[0005] Chinese Patent Publication No. CN118548326A discloses a vehicle shift control method, device, vehicle and electronic equipment for uphill and downhill conditions. By obtaining the current driving slope, current throttle opening, current brake pedal opening, current vehicle speed and current vehicle acceleration of the vehicle, the power state of the vehicle under the uphill condition or the braking state of the vehicle under the downhill condition is detected, so as to control the gearbox to downshift and send a command to prohibit upshifting, ensuring the reliability and stability of the vehicle.

[0006] Existing technologies mostly adopt the solutions of downshifting and decelerating or forcing the gearbox to return to neutral to prevent the engine from stalling due to insufficient vehicle power, and there is no working condition of secondary engagement and separation of the clutch pedal. In fact, due to operating habits, when the driver operates the tractor to drive or work, the driver will use the clutch pedal to cut off the vehicle power in time or precisely control the vehicle speed. At this time, it is necessary to pay attention to the engagement state of the gearbox gears after the clutch pedal is separated again. If the direction clutch engages after the clutch pedal returns, at the current gear, the engine speed will rise or fall greatly, which will cause a large impact on the whole vehicle, and may even cause the gearbox to drag the engine in reverse, resulting in overspeeding or stalling problems. Summary of the Invention

[0007] The purpose of the present invention is to provide a power shift gearbox gear control method, a power control system and a tractor. When the clutch pedal acts, the power between the engine and the gearbox is interrupted. At this time, according to the real-time vehicle speed, the theoretical engine speed at each gear when the pedal returns is calculated and compared with the real-time engine speed to accurately match the optimal gear to maintain the engine speed stable and avoid the engine from overspeed or stalling.

[0008] To achieve the above object, the present invention is implemented by the following technical solutions: In the first aspect, the present invention provides a power shift gearbox gear control method, which includes: Judge the state of the clutch pedal and perform the action of disengaging the direction clutch; Collect the output shaft speed in the neutral state and convert it to the real-time vehicle speed; Based on the real-time vehicle speed and the speed ratios at each gear of the gearbox, calculate the theoretical engine speed at each gear at the real-time vehicle speed; Select the optimal gear based on the theoretical engine speed and the real-time engine speed at each gear; After engaging the clutch of the optimal gear, perform the reset of the clutch pedal.

[0009] Preferably, the step of judging the state of the clutch pedal and performing the action of disengaging the direction clutch includes: The transmission control unit collects the clutch pedal depth through a hard wire. When the clutch pedal depth D cp ≥ 90%, issue an instruction to request the clutch actuator to act and disengage the direction clutch.

[0010] Preferably, the step of collecting the output shaft speed in the neutral state and converting it to the real-time vehicle speed includes: V rw =(0.377 × n out × R) / (0.377 × i RR × i MGR ), where Vrw is the real-time vehicle speed, n out is the rotational speed of the output shaft of the power shift transmission, R is the tire radius, i RR is the main reduction ratio, i MGR is the speed ratio of the section shift box.

[0011] Preferably, calculating the theoretical engine speed at each gear under the real-time vehicle speed based on the real-time vehicle speed and the speed ratios at each gear of the transmission includes: n te = (V rw × i RR × i GR × i MGR ) / (0.377 × R), where n te is the theoretical engine speed, i GR is the gear speed ratio.

[0012] Preferably, selecting the optimal gear based on the theoretical engine speed and the real-time engine speed at each gear includes: Calculating the difference between the theoretical engine speed and the real-time engine speed at each gear to obtain the engine speed difference at each gear, denoted as Δ1, Δ2, Δ3, Δ4, and taking the absolute value of the engine speed difference at each gear; Selecting the gear corresponding to the minimum absolute value of the engine speed difference as the optimal gear; Sending an instruction through the transmission control unit to quickly disengage the currently engaged gear clutch and simultaneously cross-engage the selected optimal gear clutch.

[0013] Preferably, before performing the clutch pedal reset, it further includes: If the engaged optimal gear clutch is the maximum gear C4, comparing the absolute value |Δ4| of the engine speed difference with a preset first threshold and a second threshold, When |Δ4| ≥ the first threshold, the transmission control unit sends an upcoming overspeed signal to the cab; When |Δ4| ≥ the second threshold, the transmission control unit sends an overspeed signal to the cab to remind to take braking measures; wherein, the second threshold is greater than the first threshold.

[0014] Preferably, before performing the clutch pedal reset, it further includes: If the engaged optimal gear clutch is the minimum gear C1, comparing the absolute value |Δ1| of the engine speed difference with a preset fourth threshold and a fifth threshold, When |Δ1| ≥ the fourth threshold, the transmission control unit sends an early warning of engine speed drop and automatically cuts off the PTO output; When |Δ1| ≥ the fifth threshold value, the transmission control unit sends an engine speed too low alarm signal to the cab to remind to increase the engine speed; Among them, the fifth threshold value is greater than the fourth threshold value.

[0015] Preferably, after the clutch pedal is reset, the following is further included: If the clutch of the optimal gear combined is the maximum gear C4 and there is no accelerator pedal operation, and the increase value of the engine speed within the set time is greater than or equal to the third threshold value, the transmission control unit continues to send an overspeed signal until the engine speed is stable.

[0016] Preferably, after the clutch pedal is reset, the following is further included: If the clutch of the optimal gear combined is the minimum gear C1 and the decrease value of the engine speed within the set time is greater than or equal to the sixth threshold value, the transmission control unit continues to send an engine speed too low alarm signal until the engine speed is stable.

[0017] In a second aspect, the present invention provides a power control system, including: an engine control unit and a transmission control unit. The engine control unit and the transmission control unit communicate with cab equipment through a CAN bus, and the control system performs gear control by using the above-mentioned power shift transmission gear control method.

[0018] In a third aspect, the present invention provides a tractor, including the above-mentioned power control system.

[0019] The beneficial effects brought by the technical solution of the present invention are as follows: The present invention proposes a power shift transmission gear control method, a power control system and a tractor, which can realize that after the clutch pedal returns to its original position, the vehicle power is safely, smoothly and quickly transmitted from the engine to the wheels through the transmission. During the gear control process, the TCU can accurately select the optimal gear according to the real-time vehicle speed, ensure that after the transmission is re-engaged, the engine speed fluctuates less, there is no obvious impact on the whole vehicle, and the problems of engine overspeed or flameout are avoided; at the same time, through the cab instrument display or the light buzzer, etc., the driver is reminded of the vehicle state to guide the next manual operation, protect the engine and the transmission, and improve the driving and operation safety of the whole vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the tractor power transmission system; Figure 2 It is a schematic diagram of the tractor power control system; Figure 3 It is a schematic flow chart of the tractor power shift transmission gear control method provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings. Herein, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0022] Herein, it should also be noted that in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0023] It should be emphasized that the term "comprising / including" as used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0024] Herein, it should also be noted that if not otherwise specified, the term "connection" as used herein can refer not only to direct connection, but also to indirect connection with an intermediate.

[0025] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0026] It should be emphasized here that the step labels mentioned hereinafter are not intended to limit the order of the steps. Instead, it should be understood that the steps can be executed in the order mentioned in the embodiments, or different from the order in the embodiments, or several steps can be executed simultaneously.

[0027] The present invention takes a typical tractor power transmission system as an example, as Figure 1 shown. It mainly consists of an engine, a main box of a power shift transmission, a sectional mechanical shift box and a PTO device. Among them, the engine provides power for the whole vehicle, transmits the power to the main box of the power shift transmission, then to the sectional mechanical shift box, and finally the power is output to the wheels by the PTO device to realize the running of the whole vehicle. The main box mainly includes direction clutches (CF, CR) and gear clutches (C1, C2, C3, C4). On the other hand, after passing through the PTO clutch, the engine directly transmits the power to the PTO device for the tractor to carry out field operations.

[0028] The tractor power control system mainly includes an ECU (engine control unit), a TCU (transmission control unit), etc., and communicates with cab equipment (such as instruments) through a CAN bus, as Figure 2 shown.

[0029] During the tractor's driving process, when the driver fully depresses the clutch pedal, after the TCU receives the signal, it sends an instruction to the clutch actuator to disengage the CF or CR clutch, disconnecting the power link between the engine and the transmission. The whole vehicle enters the neutral state, and the state of the transmission at this time is sent to the CAN bus for the ECU, instrument, etc. to retrieve and use. At the same time, the TCU reads the engine speed signal from the CAN bus, selects the optimal gear before the clutch pedal returns, engages the corresponding gear clutch, and stabilizes the engine speed.

[0030] When the clutch pedal returns to its original position, if the current gear is relatively low at this vehicle speed, after the direction clutch engages, the transmission drags the engine speed to increase, affecting the driving experience, and at the same time seriously damaging the service life of the transmission and the engine. If the current gear is relatively high at this vehicle speed, after the direction clutch engages, the transmission drags the engine speed to decrease, and in severe cases, it will cause the engine to stall, affecting the normal driving and operation of the tractor. Therefore, it is particularly important to select the appropriate gear before the clutch pedal returns to its original position.

[0031] Embodiment 1

[0032] Based on the above-mentioned working conditions of depressing the clutch pedal during the tractor's driving or operation process, Embodiment 1 of the present invention provides a method for controlling the gear of a power shift transmission, as Figure 3 shown, the specific process is as follows: (1) Judge the state of the clutch pedal. The TCU collects the depth of the clutch pedal through a hard wire. When the depth D of the clutch pedal cp ≥90%, step (2) is executed.

[0033] (2) The TCU judges that the driver requests to cut off the power transmission between the engine and the transmission. Then the TCU issues an instruction to request the clutch actuator to act and disengage the direction clutch. At this time, the gear clutch is still in the engaged state, and step (3) is executed.

[0034] (3) The whole vehicle enters the neutral state, collects the output shaft speed, converts the real-time vehicle speed V rw , according to the speed ratios of each gear of the transmission, calculate the theoretical engine speeds n te1 , n te2 , n te3 , n te4 corresponding to the vehicle speed at each gear at this real-time vehicle speed, Make a difference between the theoretical engine speed and the real-time engine speed n re to obtain Δ1, Δ2, Δ3, Δ4, and execute step (4); Among them, the real-time vehicle speed is calculated as follows: V rw =(0.377×n out ×R) / (0.377×i RR×i MGR ), where V rw is the real-time vehicle speed, in km / h, n out is the rotational speed of the output shaft of the power shift transmission, in rpm, R is the tire radius, in m, i RR is the main reduction ratio, i MGR is the speed ratio of the section shift gearbox.

[0035] The theoretical engine speed corresponding to the vehicle speed in each gear is calculated as follows: n te = (V rw × i RR × i GR × i MGR ) / (0.377 × R), where n te is the theoretical engine speed, in rpm, i GR is the gear ratio.

[0036] (4) Calculate the absolute value of the difference between the theoretical engine speed and the real-time engine speed, and select the gear clutch corresponding to the minimum absolute value. Then, the TCU issues a command to quickly disengage the currently engaged gear clutch and simultaneously cross-engage the selected gear clutch.

[0037] (5) According to the currently engaged gear clutch, different control measures are executed, specifically: If the currently engaged gear clutch is the maximum gear C4, execute step (6); if the currently engaged clutch is the minimum gear C1, execute step (8); otherwise, execute step (10).

[0038] (6) When the currently engaged gear clutch is C4, compare the absolute value of the engine speed difference with a pre-set first threshold and a second threshold. When |Δ4| ≥ the first threshold, the TCU sends an upcoming overspeed signal to the CAN bus. After the cab receives the signal, a lighting alarm indication is issued; when |Δ4| continues to rise and when |Δ4| ≥ the second threshold, the TCU sends an overspeed signal to the CAN bus. After the cab receives the signal, a buzzer alarm indication is issued and it is displayed on the instrument interface to remind the driver to take braking measures; then, transfer to step (7); if |Δ4| < the first threshold, directly transfer to step (7); it should be noted that in this embodiment, the second threshold is greater than the first threshold, but the specific difference between the first threshold and the second threshold needs to be determined during the vehicle debugging process, and the parameter characteristics of different tractors are different.

[0039] (7) Perform the clutch pedal reset, engage the direction clutch, and restore the power transmission between the engine and the gearbox. At this time, the real-time engine speed is equal to the theoretical real-time engine speed. If there is no throttle pedal operation and the increase value of the engine speed within the set time is greater than or equal to the third threshold, the TCU continues to send an overspeed signal to the CAN bus to remind the driver to take braking measures until the engine speed stabilizes, and then perform step (11).

[0040] It should be noted that the set time is set according to the parameter characteristics of different tractors, which can be 1 s or 0.1 s.

[0041] (8) The currently engaged clutch is C1. Compare the absolute value of the engine speed difference with the pre-set fourth threshold and fifth threshold. When |Δ1| ≥ the fourth threshold, the TCU sends an engine speed decrease warning to the CAN bus and automatically cuts off the PTO output; when |Δ1| continues to rise and |Δ1| ≥ the fifth threshold, the TCU sends an engine speed too low alarm signal to the CAN bus. After receiving the signal in the cab, a buzzer alarm indication is issued, and the driver is reminded to increase the engine speed on the instrument display interface; then transfer to step (9). It should be noted that the fifth threshold is greater than the fourth threshold, but the specific difference between the fifth threshold and the fourth threshold needs to be determined during the vehicle commissioning process, and the parameter characteristics of different tractors are different.

[0042] (9) Perform the clutch pedal reset, engage the direction clutch, and restore the power transmission between the engine and the gearbox. At this time, the real-time engine speed is equal to the theoretical real-time engine speed. If the decrease value of the engine speed within the set time is greater than or equal to the sixth threshold, the TCU continues to send an engine speed too low alarm to the CAN bus to remind the driver to perform an operation to increase the engine speed until the engine speed stabilizes, and then perform step (11).

[0043] It should be noted that the set time is set according to the parameter characteristics of different tractors, which can be 1 s or 0.1 s.

[0044] (10) Perform the clutch pedal reset, engage the direction clutch, and restore the power transmission between the engine and the gearbox. At this time, the real-time engine speed is equal to the theoretical real-time engine speed; the engine speed transitions smoothly, and then perform step (11).

[0045] (11) Complete the gear control under the condition of secondary separation and engagement of the clutch pedal. Embodiment 2

[0046] Based on the gear control method of the above-mentioned Embodiment 1, when the tractor is on a downhill slope and the current gear is F2, at this time, the driver fully depresses the clutch pedal, the CF clutch disengages, the C2 clutch remains engaged, and the TCU starts to calculate the difference Δ between the theoretical engine speed and the actual engine speed at each gear. Since the vehicle is on a downhill slope, at this time, as the vehicle speed increases, the TCU selects the optimal gear. If the absolute value of Δ3 is the smallest, the C2 clutch quickly disengages, and at the same time, the C3 clutch is cross-engaged, the clutch pedal returns to its original position, the direction clutch engages, and the whole vehicle continues to travel on the slope in F3 gear. Embodiment 3

[0047] Based on the gear control method of the above-mentioned Embodiment 1, when the tractor is operating in F3 gear with the PTO turned on, at this time, the driver needs to decelerate in advance to adjust the operating state, fully depress the clutch pedal, the CF clutch disengages, the C3 clutch remains engaged, and the TCU starts to calculate the difference Δ between the theoretical engine speed and the actual engine speed at each gear. Since the vehicle is in a power-off state and the PTO device is still operating, the vehicle speed decreases. At this time, the TCU selects the optimal gear to C1, but the vehicle speed still decreases, resulting in |Δ1|≥the fourth threshold, but |Δ1|≤the fifth threshold, then the PTO device is cut off. If the engine speed continues to decrease when the clutch pedal is restored and the transmission is in F1 gear, a beeping sound is emitted in the cab, and the instrument reminds the driver to increase the engine speed.

[0048] Through the above method, the gear control of the tractor when the clutch pedal is disengaged and engaged for the second time can be realized, and the problems of possible engine overspeed and flameout can be solved. Embodiment 4

[0049] Embodiment 4 of the present invention provides a power control system, including: an engine control unit and a transmission control unit. The engine control unit and the transmission control unit communicate with the cab equipment through the CAN bus. The control system uses the power shift transmission gear control method of the above-mentioned embodiment for gear control. Embodiment 5

[0050] Embodiment 5 of the present invention provides a tractor, including the power control system of the above-mentioned embodiment.

[0051] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can still be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A gear control method for a power shift transmission, characterized in that Including: Judge the state of the clutch pedal and perform the action of disengaging the directional clutch; Collect the rotational speed of the output shaft in the neutral state and convert it to obtain the real-time vehicle speed; Based on the real-time vehicle speed and the gear ratios at each gear of the transmission, calculate the theoretical engine speed at each gear at the real-time vehicle speed; Select the optimal gear based on the theoretical engine speed and the real-time engine speed at each gear; After engaging the clutch of the optimal gear, perform the reset of the clutch pedal.

2. The gear control method of a power shift transmission according to claim 1, characterized in that, The judging the state of the clutch pedal and performing the action of disengaging the directional clutch includes: The transmission control unit collects the depth of the clutch pedal through a hard wire. When the depth D of the clutch pedal cp ≥ 90%, it issues an instruction to request the clutch actuator to act and disengage the directional clutch.

3. A gear control method for a power shift transmission according to claim 1, characterized in that, The collecting the rotational speed of the output shaft in the neutral state and converting it to obtain the real-time vehicle speed includes: V rw =(0.377 × n out × R) / (0.377 × i RR × i MGR ), Where V rw is the real-time vehicle speed, n out is the rotational speed of the output shaft of the power shift transmission, R is the tire radius, i RR is the main reduction ratio, i MGR is the speed ratio of the section shift transmission.

4. A gear control method for a power shift transmission according to claim 3, characterized in that, The calculating the theoretical engine speed at each gear at the real-time vehicle speed based on the real-time vehicle speed and the gear ratios at each gear of the transmission includes: n te = (V rw × i RR × i GR × i MGR ) / (0.377 × R), where n te is the theoretical engine speed, and i GR is the gear ratio.

5. A power shift transmission gear control method according to claim 1, characterized in that, The selecting the optimal gear based on the theoretical engine speed and the real-time engine speed at each gear includes: Calculate the difference between the theoretical engine speed and the real-time engine speed at each gear to obtain the engine speed difference at each gear, denoted as Δ1, Δ2, Δ3, Δ4, and take the absolute value of the engine speed difference at each gear; Select the gear corresponding to the minimum absolute value of the engine speed difference as the optimal gear; Send an instruction through the transmission control unit to quickly disengage the currently engaged gear clutch and simultaneously cross-engage the selected optimal gear clutch.

6. A method for controlling gear positions of a power shift transmission according to claim 5, characterized in that, Before performing the reset of the clutch pedal, it further includes: If the engaged optimal gear clutch is the maximum gear C4, compare the absolute value of the engine speed difference |Δ4| with a preset first threshold and a second threshold; When |Δ4| ≥ the first threshold, the transmission control unit sends an upcoming overspeed signal to the cab; When |Δ4| ≥ the second threshold, the transmission control unit sends an overspeed signal to the cab to remind to take braking measures; Wherein, the second threshold is greater than the first threshold.

7. A method for controlling gear shifting of a power shift transmission according to claim 5, characterized in that Before performing the reset of the clutch pedal, it further includes: If the engaged optimal gear clutch is the minimum gear C1, compare the absolute value of the engine speed difference |Δ1| with a preset fourth threshold and a fifth threshold; When |Δ1| ≥ the fourth threshold, the transmission control unit sends a warning of engine speed drop and automatically cuts off the PTO output; When |Δ1| ≥ the fifth threshold, the transmission control unit sends an alarm signal of too low engine speed to the cab to remind to increase the engine speed; Wherein, the fifth threshold is greater than the fourth threshold.

8. A gear control method for a power shift transmission according to claim 6, characterized in that, After performing the reset of the clutch pedal, it further includes: If the engaged optimal gear clutch is the maximum gear C4 and there is no throttle pedal operation, and the rising value of the engine speed within the set time is greater than or equal to the third threshold, the transmission control unit continues to send an overspeed signal until the engine speed is stable.

9. A gear control method for a power shift transmission according to claim 7, characterized in that, After performing the reset of the clutch pedal, it further includes: If the engaged optimal gear clutch is the minimum gear C1 and the dropping value of the engine speed within the set time is greater than or equal to the sixth threshold, the transmission control unit continues to send an alarm signal of too low engine speed until the engine speed is stable.

10. A power control system, comprising: An engine control unit and a transmission control unit, the engine control unit and the transmission control unit communicate with the cab equipment through a CAN bus, characterized in that the power control system uses the power shift transmission gear control method described in any one of claims 1 to 9 for gear control.

11. A tractor, characterized in that, It includes the power control system described in claim 10.

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