JP4894169B2 - Shift control device for work vehicle - Google Patents

Description

  The present invention relates to a shift control device for a work vehicle that performs automatic switching control of a shift speed of a multi-speed shift transmission section.

  As shown in Patent Document 1, there is known a shift control device that automatically switches a shift transmission that can switch a gear ratio in multiple stages. The speed change transmission unit is appropriately controlled in accordance with the driving load situation in the high-speed driving area for road driving by the controller that performs the switching control processing according to the switching condition according to the engine speed and the accelerator operation. Thus, automatic up-shift running with excellent operability is possible by shifting up and down down, reflecting the operator's intention.

However, when the shift control device is shifted to the downshift side in response to an increase in travel load, for example, when climbing on the road, the shift control device is again switched to the upshift side as the engine speed increases. Therefore, if the shift operation by the operator is continued, there is a problem that hunting occurs due to frequent repetition of the shift control device upshifting and downshifting, leading to a decrease in operability of the vehicle.
Japanese Patent Laid-Open No. 2003-278903

A problem to be solved is, when it is shifted down automatically with the increase of the running load, without repeating the shea Futodaun and upshift be continued shifting operator, in the case of constant load It is an object of the present invention to provide a shift control device for a work vehicle that can automatically shift while ensuring the same excellent operability.

The invention according to claim 1 is an engine in which the output rotation speed can be increased or decreased by depressing the accelerator pedal from the holding position of the accelerator lever, a throttle opening sensor for detecting the accelerator operation of the engine, and the output rotation speed of the engine. An engine rotation sensor for detecting the engine speed, a shift transmission unit capable of switching the gear ratio of the driving power received from the engine in multiple stages, and a reference engine speed set for each shift speed of the engine. A shift control device for a work vehicle having a control unit that shifts up / down the shift stage of the shift transmission unit one by one when exceeding or below, wherein the control unit includes the same shift stage. A first shift condition for shifting up one step at a time, and a shift down condition without the accelerator operation. A second shift condition that suppresses re-shifting after shifting, and the reference engine speed value related to the upshift of the second shift condition is set to be larger than the reference engine speed value related to the upshift of the first shift condition. The re-shift up is suppressed, and the control unit switches the first speed change condition to the second speed change condition, and then the second opening until the throttle opening position of the engine is operated to a predetermined low speed position. The control unit is configured to continue the determination based on the speed change condition. Further, the control unit cancels the accelerator depression when the engine rotation is equal to or lower than the lower limit value of the automatic shift up, and the accelerator opening instruction is a predetermined value near the engine idle rotation. When the engine speed is below a certain level, the accelerator pedal is depressed to the maximum position and the throttle opening sensor When Le opening detects a condition that the maximum opening degree, if any of the time actually upshifting by the second shift condition is executed, the first shift condition to release the operation of the second shift condition It is characterized by returning to.

According to a second aspect of the present invention, in the configuration of the first aspect, the sub-shift is located at a shift position suitable for traveling on the road and increases in speed, and the generated vehicle acceleration is calculated and the shift of the shift transmission unit is The control unit controls the initial pressure and the half-clutch pressure to be applied to the clutch immediately after the occurrence based on the vehicle acceleration in the case of the control for shifting up / down the stage by one stage .

With the above configuration, when the traveling load increases, the shift transmission unit is controlled to be switched to the low speed stage side, and the switching reference for switching to the high speed stage side is changed to the high load side (second shift condition), thereby increasing the speed. Switching to the stage side is suppressed. As the second speed change condition, for example, the reference engine rotation value can be set as the high load side .

The above-described shift control device for a work vehicle performs a shift stage switching process in response to an operator operation such as a throttle opening based on a switching criterion set in the control unit, so that the shift transmission unit responds to the operator operation and the traveling load. Is switched to the selected gear. When the traveling load increases, the speed is switched to the low speed side, and the switching reference for switching to the high speed side, for example, the reference engine rotation value is changed to the high load side (second shift condition), so that the high speed stage is changed. Switching is suppressed.
Therefore, when the shift transmission is switched to the low speed side in response to an increase in the travel load in automatic shift driving, the shift to the high speed side is suppressed even if the operator's shift operation is continued, so the shift is performed thereafter. The same excellent operability as in the case of a constant load can be ensured without repeating down and up-shifting.
In addition, when the operator cancels the accelerator depression below the lower limit value of the rotation at which the engine rotation is automatically shifted up and the accelerator opening instruction is less than the predetermined rotation number near the engine idle rotation, the accelerator pedal is The second shift is performed when either the maximum shift position is detected and the throttle position sensor detects that the throttle position is at the maximum position, or when the actual shift up is performed due to the second shift condition. Since the operation of the condition is canceled and the first shift condition is restored, the situation in which the gear is not shifted up is improved unless there is an operator's operation, and an automatic shift up without a sense of incongruity becomes possible.
According to the second aspect of the present invention, since the acceleration close to the vehicle acceleration generated by the accelerator operation at the current generation position can be continued immediately after the generation, the generated feeling is improved, and the problem of shock at the time of shifting is solved. be able to.

Embodiments specifically configured based on the above technical idea will be described below with reference to the drawings.
FIG. 1 is a side view of an agricultural tractor showing an example of a work vehicle according to the present invention.
The agricultural tractor 1 has an engine 4 mounted in a bonnet at the front of an airframe having front wheels 2, 2 and rear wheels 3, 3, and rotational power of the engine 4 is transmitted to a transmission gear transmission 5 a in a mission case 5. The power transmitted and appropriately decelerated by the speed change transmission portion 5a is transmitted to the front wheels 2, 2 and the rear wheels 3, 3, and output to the working machine 6a via the rear PTO shaft 6. Yes.

In addition, a control seat 7 is provided at the top of the mission case 5 to constitute an operation unit.
Specifically, as shown in FIG. 2, a monitor 12 for displaying the driving state is provided on the front side of the steering handle 11, and a forward / reverse switching lever 13 and an accelerator lever 14 for forward / reverse switching are provided below the handle 11, and the steering handle. 11, a clutch pedal 15 and an accelerator pedal 16, left and right brake pedals 17 a and 17 b, and a speed change lever 18 serving as an operation tool for selecting a speed range on the side of the cockpit 7 are arranged and controlled by an HH position described later. The unit (controller) 8 is configured to be capable of automatic shifting according to the operation of the accelerator pedal 16 and the like. In addition, a work machine lifting / lowering one-touch lever 19c, a parking brake lever 19d, a PTO speed change lever 19e, and the like are disposed in the vicinity of the steering handle 11.

  The speed change transmission unit 5a is a gear mechanism that transmits travel power and work machine power. As shown in FIG. 3, the forward / reverse switching unit 22 that receives power from the engine 4 via the main clutch 21, and travel power from the subsequent stage. Receiving and transmitting to the front wheels 2, 2 and the rear wheels 3, 3, the main transmission 23, the auxiliary transmission 24 and the front wheel transmission clutch (2WD 4WD switching clutch) 25 for 2WD 4WD switching control, and forward / reverse It comprises a PTO reverse clutch 26, a PTO transmission unit 27, and the like that control transmission of work machine power branched by the switching unit 22 to the rear PTO shaft 6. In the two-wheel drive / four-wheel drive switching control by the front wheel transmission clutch 25, the control unit 8 detects the rotational speeds of the front wheels and the rear wheels, and is performed according to the difference, that is, the slip state. One wheel drive (2WD, rear wheel drive in the illustrated example) is switched.

  The main transmission unit 23 includes, for example, a first main transmission mechanism capable of switching between high and low speed clutches and a second main transmission mechanism capable of switching between four speed gears connected in series, and in accordance with commands from the control unit 8, It is configured to be switchable within the speed range. The auxiliary transmission unit 24 is configured to be able to select three speed ranges of high, medium and low.

  The gear ratio of all 24 speeds shown in FIG. 4 can be selected by the combination of the main transmission 23 and the sub-transmission 24. The combination is determined by the control unit 8 in accordance with the lever position for shifting. Automatic shift control is performed as a road speed range for a range of four stages from the high speed side.

  More specifically, the lever position for switching the sub-transmission unit 24 corresponds to the high, middle and low speed ranges for work travel, as shown in the operation unit (side) device arrangement perspective view of FIG. Three positions (sub-shift positions) of M and “L” are set in the lever guide 18g, and a shift up switch 18u and a shift down switch 18d for switching the main transmission unit 23 one step at a time are arranged in the shift lever 18. Furthermore, an “HH” subposition for traveling on the road is added to the “H” position. This “HH” sub-position allows the switching position of the main transmission unit 23 to be limited to the 5th to 8th speeds while maintaining the sub-shift “H”, that is, it is possible to switch only the shift positions suitable for road driving. To do. In the “HH” sub-position, automatic transmission control is performed in which the main transmission unit 23 is switched one step at a time by the control unit 8 in accordance with the accelerator position and the throttle position.

  As shown in the input / output configuration diagram of FIG. 6, the structure of the speed change control system for the speed change transmission part 5 a having the above-described structure is connected to the input part of the control part 8 at the sub-lease for detecting the operation position of the speed change lever of the sub-transmission part 24. Switch groups 24L, 24m, 24h, 24hh for shift SW1-4, shift up switch 18u for speed increase / decrease operation, shift down switch 18d, automatic shift switch (shift control switch) 8a, and gear position detection for main transmission 23 The main transmission sensor group 23p, the throttle sensor 4t and the like are connected. The output section includes a boost control valve solenoid 22b for connecting / disconnecting the clutch, main shift switching control valve solenoid groups 23a, 23b for switching between the first and second speeds and the third to fourth speeds of the main transmission section 23, and forward / reverse switching. The control valve solenoid group 22a for forward / reverse switching for switching the portion 22 and the Hi-Lo switching control valve solenoid 23c for Hi-Lo switching driving of the main transmission 23 are connected.

  The automatic transmission switch 8a is a switch for operating selection of automatic transmission processing by the control unit 8. The automatic transmission switch 8a is "ON", the auxiliary transmission unit 24 is "HH position", and the forward / reverse switching unit 22 is "forward". ”, A main shift switching process based on the accelerator operation and the engine load condition is performed.

An example of the switching criterion of the main transmission unit 23 for the automatic transmission process is shown in FIG. In other words, the main transmission 23 is switched one step at a time in the range of the fourth speed on the condition of the engine speed, the throttle opening degree, the margin degree α, the vehicle speed, and the duration.
The margin degree α is a switching criterion to be compared with “throttle opening−engine rotation”, and the switching condition is α> throttle opening−engine rotation at acceleration and α <throttle opening−engine rotation at deceleration. . Since the engine rotation corresponds to the traveling load and the throttle opening corresponds to the accelerator pedal 16, automatic shift control is performed in response to the operator's operation instruction via the depression of the accelerator pedal 16.

The control process by the control unit 8 is configured to change the condition for the next upshift to the high load side when the downshift due to the running load occurs further on the premise of the automatic shift control. Here, the engine is configured to shift up on the condition that the throttle command is in the vicinity of the engine rated speed or more and the actual engine speed is in the vicinity of the engine rated speed or more in a certain time.
With this configuration, when downshifting due to traveling load, the engine is automatically shifted down when the engine speed is away from the throttle command (when the engine speed does not increase even when the accelerator is depressed). By changing the next shift-up condition to the high load side, the shift-up can be suppressed even if the operator's shift operation is maintained.

The control procedure of the automatic shift control will be described in detail. As shown in the flowchart of FIG. 8, first, various sensors such as a shift control switch 8a, an auxiliary shift switch group 24P, a forward / reverse switching lever switch, and a throttle opening sensor 4t. Reading of values and setter values (S1) and failure determination processing (S2) described later are performed. Subsequently, the predetermined conditions are checked (S3 to S6). If all the conditions are satisfied, that is, the shift control switch is turned on, the shift lever is on the road, the forward / reverse switching lever is the forward position, and the throttle setting position is the predetermined rotation. Only when all the above conditions are satisfied, the automatic main shift switching process (S7) according to the accelerator operation and the engine load condition is performed.
In any case, the main shift switching process (S8) by the shift lever 18, the shift up switch 18u, and the shift down switch 18d is applied.

  As for a specific example of the automatic main shift switching process (S7) by the accelerator operation or the like, as shown in the flowchart of FIG. Only when the gear is downshifted, the shift condition (second shift condition) assuming a large load is set (S11, S12a), otherwise the normal shift condition (first shift condition) is set (S12b), In response to the up / down request (S13), the control valve solenoid energization is controlled (S14a, 14b), that is, the forward / reverse switching clutch is disengaged, the first speed increase / deceleration at the main shift position, and the forward / reverse switching clutch is engaged. Drive the equipment. S15 is a determination of “operation release”, and the determination returns to the original shift condition (first shift condition).

The above control process establishes a condition for 4th speed when traveling in the 3rd speed, and when the gear is automatically shifted up to the 4th speed, the switching standard is constant in a situation where the travel load is considerably high in the 4th speed travel (such as a slope). If it remains, there is a possibility of shifting down to the third speed. As a result, the switching between the third speed and the fourth speed is repeated, but this phenomenon can be solved and stable running can be achieved.
In addition, it is good also as a structure which replaces with the structure which makes a reference | standard engine speed different value, makes a vehicle speed value large, or lengthens continuation time.

Further, as in S15 of FIG. 9, the “automatic release” can restore the normal automatic upshift condition (first shift condition) even after the downshift due to the traveling load. Control processing for returning to the original shift condition (first shift condition) is as follows.
Here, when the engine speed is equal to or lower than the lower limit value of the automatic shift up speed (for example, 2000 rpm or less in the case of the third speed), the operator releases the accelerator depression and the accelerator opening instruction is a predetermined rotational speed near the engine idle speed. When the following state has elapsed for a certain period of time, or when the accelerator pedal is depressed to the maximum position and the throttle opening degree sensor (4t) detects that the throttle opening is at the maximum opening degree , the actual condition depends on the second shift condition. When the upshift is executed, the normal automatic upshift condition is restored.
This control process improves the situation where no shift is performed unless there is an operator's operation, and allows automatic shift up without any sense of incongruity.

  Further, when the operator operates the increase / decrease speed change up switch 18u and the speed change down switch 18d, the same effect can be obtained by setting a normal automatic upshift condition. In addition, when the main shift target position is other than the adaptive main shift position, for example, when the travel load is changed from the fourth speed to the third speed, and further from the third speed to the second speed, the shift from the next third speed to the fourth speed is performed. The normal shift-up condition is restored also by setting up as a normal shift-up condition.

  Of the four speeds of the main transmission 23, the combination of the speed changes to which the automatic speed change is applied is constituted by the combination of the high speed second speed (third speed and fourth speed) and the Hi-Lo clutch as the maximum vehicle speed. That is, from the low speed side, the first speed Lo, the first speed Hi, the second speed Lo, the second speed Hi, the third speed Lo, the third speed Hi, the fourth speed Lo, and the fourth speed Hi Therefore, smooth automatic transmission can be achieved by using the upper four speeds.

  Next, the switching clutch pressure of the main transmission 23 using the Hi-Lo clutch will be described. At the time of automatic shifting, the switching by only the Hi-Lo clutch is configured such that the time corresponding to the switching of the main shifting (assumed time) is increased after the main clutch is turned off.

  Specifically, after the automatic shift instruction is generated, the main clutch pressure is turned off for an estimated time (for example, 300 to 400 msec) for switching to the main shift, and then the main clutch is connected in a normal automatic shift boost pattern. By controlling the pressure in this way, it is possible to change the speed almost in the same manner as the feeling of automatic shifting by switching the main shift between the second speed and the third speed.

  Further, in the automatic shift control, when the main shift does not enter the lowest position on the road speed, it is shifted down to the lower speed side from the road speed range by shifting to the fourth speed position (the main transmission gear is at the second speed). It is configured to automatically decelerate to the fourth stage from the low speed side in all eight-stage shifts by Hi clutch on. By shifting the speed in this way, it is possible to avoid the stoppage of traveling due to the fact that the second gear does not enter even if the second gear does not enter the first gear under the same gear. In this case, the main shift monitor display is a four-stage display, similar to the road speed, and the first-speed character is blinking (or reversed). As a result, it is possible to make it easier for the operator to recognize that the main shift is abnormal.

Next, an example of controlling the clutch pressure of the forward / reverse switching clutch will be described.
The pressure applied to the clutch is proportional to the torque applied to the clutch shaft, and is converted into the acceleration applied to the vehicle. On the other hand, the actual engine speed that changes by the accelerator operation changes the acceleration of the vehicle at a certain main shift position. Will be. Therefore, if there is a large difference between this acceleration and the acceleration immediately after the shift, a shock at the time of the shift will occur, and thus such a problem can be solved by controlling the energization to the clutch boost solenoid 22b by the control unit 8. .

  That is, the main shift can be shifted by hydraulic control, the sub-shift position has a shift position suitable for road travel, and the main shift 23 when the sub-shift is at a shift position HH suitable for road travel. As shown in FIG. 11, when the vehicle is automatically shifted in conjunction with the accelerator operation, when increasing the speed, the generated vehicle acceleration is calculated (A), and the timing for increasing the speed is generated. At the time t1, the initial pressure and the half-clutch pressure applied to the clutch immediately after the occurrence are changed by the calculated acceleration as shown in FIG. 10 (B to C).

  As described above, the acceleration handling process at the time of acceleration allows the acceleration near the vehicle acceleration generated by the accelerator operation at the current generation position to be continued immediately after generation, so that the generated feeling is improved, so the shock during shifting is improved. Can solve the problem.

  Next, the configuration of a partial hydraulic circuit diagram of the tractor will be described. As shown in FIG. 12, the pressure reducing valve 31 used in the traveling / mission system is arranged independently, while the main relief valve 32 is configured separately. By configuring in this way, it is possible to ensure the differential pressure intensity during the relief operation by increasing the flow rate of the line filter 33 (mainly for contamination to the proportional valve) at the inlet of the pressure reducing valve 31.

Further, a neutral valve (electromagnetic proportional pressure reducing valve) 34 for forcibly releasing the pressure is provided at the clutch port of the forward / reverse switching clutch. With this configuration, it is possible to reliably release the clutch pressure of the forward / reverse switching 22 by stepping on the clutch pedal and the neutral operation of the forward / reverse switching lever.
Therefore, it is safe even if malfunctions of the electromagnetic proportional pressure reducing valves 22v and 22v occur.

  The 3rd and 4th speed switching hydraulic clutch 23b and the Hi-Lo speed switching hydraulic clutch 23c are configured to release the rear lubricating oil at a fixed flow rate through the valve. With this configuration, the lubricating oil for the hydraulic clutch is secured, and a flow rate capable of maintaining the pressure on the secondary pressure side can be supplied as the lubricating oil.

  The hydraulic clutch 22a for forward / reverse switching and the hydraulic clutch 23a for 1st and 2nd speed switching have a return pressure of the power steering 36 (power steering) pressurized by the low pressure relief valve 35, and the flow rate corresponding to the differential pressure by the orifice 35a is on the front side. The oil is discharged as lubricating oil. Further, unnecessary oil at this time is returned to the suction side of the pump P. With this configuration, it is possible to reduce the pump negative pressure while ensuring a large flow rate lubrication of the hydraulic clutch.

Next, the failure display in FIG. 8 will be described. Using the hydraulic clutch, Oite the forward-reverse switching capable tractors, provided with a pressure sensor for detecting the clutch pressure, a configuration to be displayed on the liquid crystal display unit that is provided on the meter panel when the following conditions are satisfied . The above condition is, for example, that a pressure sensor has applied a pressure value of 10 kgf / square cm or less for 10 seconds or more in a state where 60 seconds or more have elapsed since the engine was started, the forward / reverse shift is started, and the pressure increase to the hydraulic clutch is completed. This is the time when it is continuously detected, and engine start is determined at 800 rpm or higher.

With the above configuration, when an abnormality occurs, the operator can be warned at an initial stage, so that the time for which the clutch continues to be used in a situation where the clutch is slipping can be shortened, and repair can be made before the clutch burns out.
Therefore, if the pressure is low due to a slight abnormality related to hydraulic pressure (such as clogging) that can be dealt with by cleaning the valve, etc., the clutch will burn if you continue to use it without knowing the abnormality. It is possible to prevent a situation in which a large amount of money is required due to the replacement of ASSY.

It is a side view of an agricultural tractor. It is an operation part (front side) apparatus arrangement block diagram. It is a transmission system expansion | deployment figure of a transmission transmission part. 4 is a combination configuration table of gear positions. It is an operation part (side part) apparatus arrangement | positioning perspective view. It is a control system input / output diagram. It is a structure list | wrist of the switching conditions according to gear stage. It is a flowchart of a speed change process. It is a flowchart of main shift switching. It is a clutch pressure characteristic figure. It is a flowchart of clutch pressure control. It is a hydraulic circuit diagram of an automatic transmission.

1 Agricultural tractor (work vehicle)
2 Front wheel 2s Vehicle speed sensor 3 Rear wheel 4 Engine 4s Engine rotation sensor 4t Throttle opening sensor 5a Shift transmission unit 8 Control unit 8a Shift control switch (automatic shift switch)
14 Accelerator lever 16 Accelerator pedal 18d Shift down switch (shift switch)
18u Shift up switch (shift switch)
18 Transmission lever 22 Forward / reverse switching section 23 Main transmission section 23a Main transmission solenoid group 23p Main transmission sensor group 23b Hydraulic clutch 23c Hydraulic clutch 24 Sub transmission section 25 Front wheel transmission clutch α Margin

Claims (2)

An engine (4) whose output rotation speed can be increased or decreased by depressing the accelerator pedal (16) from the holding position of the accelerator lever (14), and a throttle opening sensor (4t) for detecting the accelerator operation of the engine (4) And an engine rotation sensor (4s) for detecting the output rotational speed of the engine (4), a shift transmission section (5a) capable of switching the speed ratio of the traveling power received from the engine (4) in multiple stages, When the output rotational speed of the engine (4) exceeds or falls below the reference engine rotational speed set for each shift speed, the shift speed of the shift transmission section (5a) is shifted up / down by one speed. A shift control apparatus for a work vehicle including a control unit (8) for causing
The control unit (8) suppresses re-shift-up after a first shift condition for shifting up one by one as a shift-up condition over the same shift stage, and after a shift-down without the accelerator operation. Having a second speed change condition,
The reference engine speed value related to the upshift in the second speed change condition is set to be larger than the reference engine speed value related to the upshift in the first speed change condition to suppress the re-shift up,
In the control unit (8), after the first shift condition is switched to the second shift condition, the determination based on the second shift condition is performed until the throttle opening position of the engine (4) is operated to a predetermined low rotation position. Is configured to continue,
Further, in the control unit (8), when the engine speed is equal to or lower than the lower limit value of the automatic shift up, the operator releases the accelerator depression and the accelerator opening instruction is constant below the predetermined speed near the engine idle speed. When the time has elapsed, when the accelerator pedal is depressed to the maximum position and the throttle opening sensor (4t) detects that the throttle opening is at the maximum opening , the actual shift up is executed according to the second shift condition. In any case, the shift control device for a work vehicle releases the operation of the second shift condition and returns to the first shift condition.   Control in which the sub-shift is at a shift position suitable for traveling on the road and the speed is increased, the generated vehicle acceleration is calculated, and the shift stage of the shift transmission section (5a) is shifted up / down by one stage. In this case, the control unit (8) controls the initial pressure and the half-clutch pressure applied to the clutch immediately after the generation based on the vehicle acceleration.

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