JPH07266911A - Four-wheel driving force control device - Google Patents

Abstract

PURPOSE:To reduce a speed change shock generated at the time of changeover operation of a main transmission and to prevent chipping of a farm surface. CONSTITUTION:When there is a changeover operation command of a main transmission, a driving method is changed over to 2WD in a four-wheel drive vehicle free to change one of the driving methods of a rear two-wheel driving state (2WD), a front and rear four-wheel driving state (4WD), a front wheel speed increasing four-wheel driving state (4WDD) by automatic control. Thereafter, the driving state is held as 2WD for a specified period of time until changeover operation of the main transmission is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive force control device for a four-wheel drive vehicle, and more particularly to a four-wheel drive vehicle for a four-wheel drive vehicle in which a main transmission gear is switched by automatically turning a reverser clutch on and off. The present invention relates to a driving force control device.

[0002]

2. Description of the Related Art A conventional four-wheel drive vehicle transmits engine power to a rear wheel and a front wheel via a reverser clutch, a main transmission, and an auxiliary transmission. In addition, a front and rear four-wheel drive system (4WD) that drives the front and rear wheels at substantially constant speed,
A rear two-wheel drive system (2WD) in which the drive of the front wheels is stopped and only the rear wheels are driven, and the front wheel speed-increasing four that increases the average peripheral speed of the front wheels to about twice the average peripheral speed of the rear wheels when turning. There is known a four-wheel drive vehicle in which any one of a wheel drive system (4WDD) is automatically switchable.

In the four-wheel drive vehicle main transmission, the speed-increasing push button or the decelerating push button is operated, the reverser clutch is automatically disengaged, and the main transmission gear is automatically switched by the hydraulic actuator. After that, the reverser clutch is automatically turned on again.

[0004]

As described above, the conventional four-wheel drive force control system of the present invention detects a slip with the ground or the two-wheel drive state (2WD) during the turn as described above. Then, the front wheel speed-increasing four-wheel drive state (4WDD) is automatically switched. Therefore, in a working state in which a rotation difference is likely to occur between the front and rear wheels, the driving state of front and rear four-wheel drive (4WD) or front wheel speed-increasing four-wheel drive (4WDD) is mainly used.
In such a state, the efficiency of the transmission of the ground driving force is high, and therefore, when the main transmission is switched, a shift shock occurs when the reverser clutch is automatically engaged. If the shift shock becomes large, the automatic control may malfunction, and the driving force of the wheels may suddenly change to scrape off the field surface.

Therefore, there arises a technical problem to be solved in order to reduce the shift shock when the main transmission is switched, and an object of the present invention is to solve this problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been proposed in order to achieve the above object, and transfers engine power to a rear wheel and a front wheel via a reverser clutch, a main transmission, and an auxiliary transmission. Transmission, rear two-wheel drive,
In a four-wheel drive vehicle in which either the front-rear four-wheel drive or the front wheel speed-increasing four-wheel drive can be switched by automatic control, when there is a switching operation command for the main transmission, The present invention provides a four-wheel drive force control device characterized in that a control means for holding the drive system in the rear two-wheel drive is provided.

[0007]

When there is a switching operation command for the main transmission, the drive system at that time is temporarily stored, and then the drive force transmission to the front drive shaft is cut off for a certain period of time to maintain the rear two-wheel drive state. Then, the reverser clutch is automatically disengaged, and the main shift gear is switched to the speed increasing side or the speed reducing side by the shifter. After that, the reverser clutch is automatically turned on again, and after the switching operation of the main transmission is completed, the rear two-wheel drive state is released and the stored previous drive system is restored.

[0008]

An embodiment of the present invention will be described in detail below with reference to the drawings. The illustrated example is an agricultural tractor 14, and the present invention is folded into the front wheels 4, 4 drive section of this agricultural tractor 14. The four-wheel drive vehicle that is the agricultural tractor 14 has front and rear wheels 4, 4, 3, 3 attached to front and rear four corners of the machine body, and is driven by using the power of the engine 1.

The front and rear wheels 4, 4, 3 and 3 are respectively connected to the front and rear axle cases 15 and 16 and project outwardly, and the base ends thereof are attached to the front frame 17 and the gear case 18 which is the main frame. It is attached. The rear end of the front frame 17 is a machine frame integrally assembled to the main frame side, and the engine 1 is detachably attached to the front portion of the front frame 17 which is the machine frame.

The central portion of the front axle case 15 in the left-right direction is pivotally attached 19 to the front frame 17 so as to be able to swing left and right, and the front wheels 4, 4 move up and down due to the unevenness of the ground. A front differential device 20 that adjusts the peripheral speed difference between the left and right front wheels 4 and 4 is provided in the center of the front axle case 15 in the left-right direction, and the front drive device 21 projects outside from a transmission case 21 to be described later. It is input via the axis 6.

A radiator 22 and a cooling fan 23 are arranged in front of the engine 1. Reference numeral 12 denotes an engine rotation sensor, which is provided in the vicinity of the cooling fan 23 in the illustrated example to measure the rotation speed of the engine 1 and transmit it to the controller 13 which is the control means. Then, the rotation of the crankshaft (not shown) and other rotating parts may be detected.

Reference numeral 24 is a bonnet which covers the front and sides of the engine 1 and auxiliary devices (not shown). Reference numeral 26 denotes a clutch housing, which is attached to the rear portion of the engine 1 and internally houses the main clutch 27, and transmits the driving force to the rear transmission case 21 portion.

Reference numeral 28 is a handle, and 29 is a handle post. The lower end of the handle post 29 is attached to the machine frame. When the handle 28 is rotated left and right, the front wheels 4 and 4 are steered left and right. And this front wheel 4,
Read the left and right steering angle of 4 with the steering angle sensor 11,
It is transmitted to the controller 13.

Fenders 30, 30 are attached from the front of the left and right rear wheels 3, 3 to the upper side, and a seat 31 is provided between the left and right fenders 30, 30. The left and right rear wheels 3, 3 are connected left and right by a rear axle case 16, and a rear differential device 25 is provided in the middle portion between the left and right. Gear case 1 that houses the rear differential device 25
8 is attached to the rear portion of the transmission case 21 described above, and the transmission case 21 is integrally connected to the rear end portion of the clutch housing 26.

A substantially flat floor 32 is attached to the seat 31 from the foot portion of the lower driver to both sides of the lower portion of the handle post 29. The floor 32 is substantially flat in the left-right direction and has an outer width that is close to the outer edge portions of the left and right fenders 30, 30, that is, a width close to the entire width of the body. The driving force from the engine 1 through the main clutch 27 is transmitted to the transmission case 21.
Enter from the front of.

The input driving force is transmitted to the rear differential device 2 via the speed change mechanism 2 including a reverser device 33 for performing forward and backward shifting, a main transmission device 34, an auxiliary transmission device 35, and the like.
It is divided into two systems: a traveling wheel drive system that reaches 5 and a PTO drive system 36 that is an external power take-out unit that is branched at the entrance of the transmission case 21. The reverser device 33
The transmission / reception of the driving force obtained from the main clutch 27 to the main transmission 34 is performed by turning on / off the hydraulic reverser clutch, and the driving force of the main clutch 27 is reversed in the forward / reverse direction. It is formed so as to switch.

The auxiliary transmission device 35 includes an auxiliary transmission lever 64.
It is possible to change gears in four stages of high speed, middle speed, low speed, and ultra low speed by the operation of, and the auxiliary shift lever position sensor 80 can detect which position the shift is made.
Further, an up / down push button is provided on the knob of the sub-transmission lever 64 or an operation panel, and the gear of the main transmission 34 is automatically switched by the operation of the push button.

That is, when the up button or the down button provided on the knob of the auxiliary shift lever 64 is pressed, the reverser clutch is automatically disengaged and the shifter is actuated by the operation of the hydraulic (or electric) actuator 81 or 82. When the vehicle moves, the gear of the main transmission 34 is automatically switched to the speed increasing side or the speed reducing side. After that, the reversing clutch is re-engaged, and the driving force obtained from the main clutch 27 is transmitted to the sub transmission 35 while being shifted by the main transmission 34.

A rotation sensor 83 is provided on the input side of the reverser device 33, and a rotation sensor 84 is provided on the output side of the reverser device 33. The rotation difference between the input and output sides is read based on the detection values of both rotation sensors 83 and 84, and the controller 13 determines whether the reverser clutch is in the engaged state or the disengaged state.

In place of the rotation sensors 83 and 84, a pressure detecting device (not shown) is provided in the hydraulic pipe to the reverser clutch, and the pressure detecting device detects the pressure rising state of the reverser clutch and the reversing clutch is engaged. It may be formed so as to determine whether it is in the state or the cut state. 37 is a PTO shaft, and a gear case 18
A universal joint (not shown), which projects rearward from the PTO shaft 37 and drives various working machines, is detachably attached to the PTO shaft 37.

Left and right rear wheels 3, 3 are attached to the rear of the transmission path from the rear differential device 25. The left and right rear wheels 3, 3 are individually or simultaneously braked by independent left and right brake petals (not shown).
The rear differential device 25 outputs from the speed change mechanism 2
The output gear 38 and the counter gear 39 are provided on the drive shaft during the input to the main gear 40 to transmit the drive force of the rear wheel drive rotary shaft 5 to the main gear 40.

The main gear 40 is engaged with the spline portion of the first clutch boss 41 and rotates integrally with the first clutch boss 41. Further, another sub gear 42 is attached by engaging with this spline portion, and the main and sub gears 40, 42 rotate simultaneously. These are two gears in the illustrated example, but the main and sub gears 40 and 42 may be one if there is no problem in the number of teeth.

A counter inlet gear 43 is always meshed with the sub gear 42, and a counter outlet gear 45 connected by a connecting drive shaft 44 is also integrally rotatable. The counter exit gear 45 is the second clutch gear 4
6 always meshes with this second clutch gear 46
The second clutch boss 47, which is integral with, can be simultaneously rotated.

That is, when the main gear 40 rotates, the first clutch boss 41 and the second clutch boss 47, which are rotatably provided so as to face each other on the front drive clutch shaft 48, rotate at the same time although their rotational speeds are different. When the gear 40 stops, the first and second clutch bosses 41 and 47 also stop at the same time. The counter inlet gear 43 is accelerated by the sub gear 42, and the second clutch gear 46 is accelerated by the counter outlet gear 45. When the first clutch boss 41 makes one rotation, the second clutch boss 47 is substantially two. Rotate.

A first piston 49 and a second piston 50 are disposed between the first and second clutch bosses 41 and 47, and a drive drum 52 containing a plurality of friction plates 51 and 51 is mounted on the outer circumference thereof. Is covered. The drive drum 52 is divided into front and rear by a partition wall 53, and the first clutch boss 41 at the rear portion, the friction plate 51 and the first piston 49 constitute a direct coupling clutch 7, and the drive drum 52 frictions at the second clutch boss 47 at the front portion. Board 5
1 and the second piston 50 constitute the speed increasing clutch 8.

The drive drum 52 has a front drive clutch shaft 48.
It is integrated into the spline part of the. Lubricating oil 54 is held in the transmission case 21 to lubricate each transmission gear and shafts. A part of the lubricating oil 54 is sucked and pressurized by the oil pump 55, and the first piston 49 of the direct coupling clutch 7 and the partition wall 5 are connected via the oil passage switching valve 58.
It is supplied to either one of the first oil chamber 56 between the three and the second oil chamber 57 between the second piston 50 of the speed increasing clutch 8 and the partition wall 53.

The oil passage switching valve 58 of FIG. 2 shows a neutral state. In this neutral state, both the direct coupling clutch 7 and the speed increasing clutch 8 are in the OFF state. Next, when the first solenoid 59 is energized, the oil passage switching valve 58 switches to the valve 58a portion, the high pressure oil flows into the first oil chamber 56, the direct coupling clutch 7 is connected, and the rotational power of the rear wheel drive rotating shaft 5 is transferred. It is transmitted to the front drive clutch shaft 48 as it is.

When the second solenoid 60 is energized, the oil passage switching valve 58 is switched to the valve 58b portion, and the high pressure oil is transferred to the second oil chamber 5
7, the speed increasing clutch 8 is connected, and the rotation of the rear wheel drive rotary shaft 5 is almost doubled and transmitted to the front drive clutch shaft 48. The rotation of the rear wheel drive rotary shaft 5 input to the front drive clutch shaft 48 is interlocked with the front drive shaft 6 described above, and drives the front wheels 4, 4 via the front differential device 20.

In this way, when the direct coupling clutch 7 is ON and the speed increasing clutch 8 is OFF, the rotation of the front drive shaft 6 is driven at a substantially constant speed with respect to the rear wheel drive rotary shaft 5, and the front and rear four-wheel drive state ( 4WD), the rotation of the front drive shaft 6 when the direct coupling clutch 7 is OFF and the speed increasing clutch 8 is ON is driven at approximately double speed with respect to the rear wheel drive rotating shaft 5, and the front wheel speed-increasing four-wheel drive state (4WDD ). Further, when both the clutches 7 and 8 are both in the OFF state, the front drive shaft 6 is simply in the rolling wheel state and is in the rear two-wheel drive state (2WD). (The rolling wheel state means that the front wheels 4 are pulled and rotated when the machine body moves and stopped when the machine body is stopped.) 61 is a drain oil passage, and the oil passage switching valve 58 is switched. And clutch 7,
The pressure oil in the oil chambers 56 and 57 of No. 8 escapes to the transmission case 21 which also serves as a hydraulic tank.

In the illustrated example, the transmission case 21 is used as an oil sump, but a separate oil tank may be provided exclusively. A rear shaft rotation sensor 9 is arranged near the counter outlet gear 45, and a front shaft rotation sensor 10 is arranged near the driving drum 52, and is a controller which is a control means for detecting the rotation speed of each rotating portion. I have told 13.

The agricultural tractor 14 of the present invention first travels in a "rear two-wheel drive state" (2WD) in which only the rear wheels 3 are driven, and the steering angle sensor 11 detects the steering angle of the steering wheel 28 during this traveling. When the set angle "α" (probably 5 degrees) is exceeded, the "turning control F" 62 is controlled, and when it is not exceeded, the "straight ahead control G" 63 is controlled. The "turning control F" 62 controls the "turn control" 67 at a large steering angle when all the conditions shown in FIG. 6 are satisfied, and the "turn control at a small steering angle" when a part of the conditions is denied. The control is changed to "control" 68.

The "turn control" 67 at the large steering angle of the "turning control F" 62 will be described later with reference to FIG. 7, and the "turn control" 68 at the small steering angle will be described later with reference to FIG. The "straight ahead control G" 63 is divided into "slip control" 71 or "brake control" 77 depending on various conditions as shown in FIG. "Slip control" 71 is "front and rear four-wheel drive state"
It is to determine whether or not to continue (4WD).

The "brake control" 77 detects a change in the rotation of the front wheel 4 by the front shaft rotation sensor 10 when the rear wheel 3 of the agricultural tractor 14 running in the "rear two-wheel drive state" (2WD) is braked. However, when the rotation of the front wheels 4 does not drop, the direct coupling clutch 7 is turned on and the "front and rear four-wheel drive state" (4
WD) improves the braking performance.

In any of the driving states, when the up button or the down button provided on the sub speed change lever 64 is pressed, the main speed change control shown in FIG. Two-wheel drive system "(2WD). Next, the details of the four-wheel drive force control of the present invention will be described in more detail. First, as shown in FIG. 5, while the agricultural tractor 14 is traveling in the “rear two-wheel drive state” (2WD) described above, the steering amount of the steering wheel 28 changes the set angle “α” (5 degrees) of the steering angle sensor 11 to the predetermined value. "Turning control F" depending on whether or not it exceeds
Alternatively, the control shifts to "straight ahead control G". in this way,
The control is divided into two large subroutines depending on the detection value of the steering angle sensor 11.

"Turning control F" which is one of the subroutines
As shown in FIG. 6, when all of the following conditions are satisfied, "turn control" is controlled, and when a part of the conditions is denied, "turn control" is controlled. When the "turning control F" starts, first, as initialization, the data in the "straight ahead control G" described later is initialized, that is, the first solenoid 59.
Then, the second solenoid 60 is turned off to start traveling in the "rear two-wheel drive state" (2WD) in which the driving force to the front wheels 4 and 4 is cut off.

Next, the shift position of the sub-transmission lever 64 is read, and when the sub-transmission lever 64 is in the high speed position, it is regarded as a traveling mode such as road traveling or trailer towing, and the sub-transmission lever 64 is in the middle speed or the low speed. , When it is in any position of ultra-low speed, it is regarded as a working mode such as rotary tilling or scraping. Then, when the auxiliary transmission lever 64 is at a position lower than the middle speed, the vehicle speed averaged between the left and right rear wheels 3 and 3 read by the rear axle rotation sensor 9 is the set vehicle speed "V" (4 km /
It has not reached the set vehicle speed "V", and the steering angle of the front wheels 4, 4 read by the steering angle sensor 11 is ± γ (approximately 40 degrees to one side from the straight traveling state). ) And the position lever 66 for operating the elevating position of a working machine (not shown) attached to the end of the body of the agricultural tractor 14 so as to be able to move up and down is operated to raise It activates "turn control" for traveling in "wheel drive state" (4WD).

Further, the condition of "turn control", that is, the case where the auxiliary transmission lever 64 is not lower than the medium speed position (that is, the high speed position), and the rear wheels 3, 3 read by the rear shaft rotation sensor 9 are used. When the vehicle speed averaged over the left and right exceeds the set vehicle speed “V”, and when the steering angles of the front wheels 4 and 4 read by the steering angle sensor 11 do not reach ± γ, the position lever 66 keeps the lowered position operation. If
If all or any of the conditions are met,
Activate "turn control".

It should be noted that the actual vehicle speed calculated based on the detection value of the front axle rotation sensor 10 or the rear axle rotation sensor 9 is not used to judge the traveling mode and the working mode by the shift position of the auxiliary transmission lever 64. The traveling mode and the work mode may be determined based on the theoretical vehicle speed calculated based on the detected value. Then, in the case of the traveling mode, the process shifts to "turn control".

Next, the operation of the "turn control" will be described with reference to FIG. First of all after starting, it is judged whether or not the full turn flag is ON. If not, the vehicle is traveling in the "rear two-wheel drive state" (2WD), and the front axle rotation sensor 10 and the rear axle rotation sensor The detected value of 9 is read, and it is determined whether or not there is a difference in the average peripheral speeds of the left and right wheels of the front wheels 4, 4 and the rear wheels 3, 3.

That is, the front axle rotation sensor 10 detects the moving speed of the machine body running in the "rear two-wheel drive state" (2WD), and the rear wheel rotation sensor 9 detects the drive speed of the rear wheels 3.
Then, it is judged whether the front wheel 4 is overrun with respect to the rear wheel 3 by judging whether the speed difference between them is large or small. One of the preconditions is that the front wheels 4 always exceed the steering angle γ when the "turn control" is activated, so it can be seen that the vehicle is turning. If the rear wheels 3 do not cause a ground slip during driving due to the difference in the turning radii of the respective wheels, the front wheels 4 have the turning radii even if the "rear two-wheel drive state" (2WD). The larger the amount, the faster the vehicle is pushed by the machine body, and the peripheral speed of the front wheels becomes an overrun than the peripheral speed of the rear wheels 3, and the next overrun rate is determined.

When the overrun rate of the front wheels 4 exceeds a predetermined value "B" (about 180% as an experimental value for the rear wheels), that is, the rear wheels 3 and 3 reliably transmit the driving force to the ground. At this time, the operation of the "front wheel speed-increasing four-wheel drive state" (4WDD) for increasing the speed of driving the front wheels 4 is unnecessary, the full turn flag is not turned on, and the "rear two-wheel drive state" (2W
Turn in D).

During this turning, if the rear wheel 3 slips to the ground due to soft ground or the like and the force pushing the vehicle body is weakened, the overrun rate of the front wheel 4 does not reach the predetermined value "B". The full turn flag, which is a flag of "front wheel speed-increasing four-wheel drive state" (4WDD), is turned on, then the second solenoid 60 is turned on, and the second oil chamber 57 on the speed increasing clutch 8 side is turned on.
The pressure oil flows into the front wheels 4 and the front wheels 4 are driven by increased speed rotation.

From the time the second solenoid 60 is turned on to the time when the speed increasing clutch 8 actually operates, 0.4 to
There is a time lag of 0.5 seconds. During this time lag, the overrun rate did not reach "B", and the time lag of 0.4-
When 0.5 seconds has elapsed, the front wheels 4 are speed-up driven by the operation of the speed increasing clutch 8, the overrun rate of the front wheels 4 exceeds a predetermined numerical value "B", and the process proceeds to the next weight processing. .

First, since the weight process is not being performed at the first time, the result is NO, and the number of changes in the count number of "2WD and full turn" is checked next. The number of changes in the count number of "2WD and full turn" means that the overrun rate of the front wheels 4 reaches a predetermined value "B" and the vehicle travels in the "rear two-wheel drive state" (2WD), or This is the number of fluctuations of switching to the "front wheel speed-increasing four-wheel drive state" (4WDD), which is a full turn without the overrun rate reaching the predetermined value "B", and the count number of one round trip is the predetermined number of times. N ”(probably 3 times) is determined.
At the first time, since the count number of “2WD and full turn” is not counted, first, the wait process 70 for T seconds (approximately 1 second) is started.

The weight processing 70 in this case is to confirm the ON state of the second solenoid 60 for T seconds, and when the weight processing 70 has elapsed, the count of the number of fluctuations of "2WD and full turn" is added once. And continue turning. If the wait processing 70 does not continue for T seconds, the count is not added. When the count of the number of fluctuations of "2WD and full turn" is 3 or less, the full turn flab is cleared once, the "rear two-wheel drive state" (2WD) is restored, and turning is continued.

The time required for the agricultural tractor 14 to turn at the field end is about 6 to 8 seconds at a speed of about 3 km / hour,
If the overrun rate cannot exceed the predetermined value "B" for 6 to 8 seconds, "rear two-wheel drive state"
(2WD) and full turn “front wheel speed-increasing four-wheel drive state” (4
WDD) changes at any time. Therefore, while the count of the number of fluctuations of "2WD and full turn" does not exceed the set number N (3 times), it is determined that the traveling field surface is difficult to slip, the full turn flag is cleared each time, and "rear two-wheel drive state" Turn at (2WD).

On the other hand, when the number of fluctuations of "2WD and full turn" exceeds 4 times the set number N during this turning, it is determined that the surface of the traveling field is slippery, and the full turn flag is cleared. Without "front wheel speed-up four-wheel drive state"
(4WDD) control is performed to forcibly pull the machine body by the front wheels 4 and the rear wheels 3. Agricultural tractor 1 at the end of the field
When the turning of No. 4 is completed, the driver gradually returns the steering wheel 28 to the straight running state side, and shifts from the "turn control" to the "turn control".

Next, "turn control" will be described with reference to FIG. After the control is started, the data in the "turn control" is initialized, the first and second solenoids 59 and 60 are turned off, and the control is started from the "rear two-wheel drive state" (2WD). First, determine whether the 4WD flag is ON,
If it is not ON, the process proceeds to the determination of whether or not the rear wheels 3 are slipping in the "rear two-wheel drive state" (2WD).

The slip of the rear wheels 3 is determined as the "rear two-wheel drive state" (2WD) using the rear axle rotation sensor 9 and the front axle rotation sensor 10 as described above, and the average rotation of the front and rear wheels 4, 3 is determined. Determine based on the difference in peripheral speed. If there is slip on the rear wheel 3, turn on the 4WD flag,
The first solenoid 59 is turned on to bring the front and rear wheels 4, 3 into the "front and rear four-wheel drive state" (4WD) at substantially the same speed at the same time, and the "slip control" subroutine is entered. If the rear wheels 3 do not slip, the vehicle continues to travel in the "rear two-wheel drive state" (2WD).

Next, the "slip control" will be described with reference to FIG. In this case, the "slip control" is a "front and rear four-wheel drive state" (4
WD) to decide whether to continue,
When the 4WD lock flag is ON, this "slip control" is not performed. The 4WD lock flag means that the direct coupling clutch 7 is actuated by turning on the first solenoid 59, and the front wheels 4 and 4 and the rear wheels 3 and 3 are always driven at four wheels at substantially the same speed. (4WD) is a flag for traveling while being locked.

When the 4WD lock flag is not ON,
When the traveling field surface is difficult to slip, the vehicle travels in the "rear two-wheel drive state" (2WD) even if there is a control instruction of "front and rear four-wheel drive state" (4WD). It is intended to run in the "wheel drive state" (4WD). If the 4WD lock flag is not ON,
It is determined whether or not the counting of the time "S" seconds (approximately 30 seconds) is started, and if it is not counted, the counting is started for "S" seconds.

Next, it is judged whether or not the rear wheels 3 are slipping, and if they are slipping, the slip control is terminated and the "front and rear four-wheel drive state" (4WD) is continued.
The first one is "front and rear four-wheel drive state" depending on the prerequisites.
Since the vehicle is traveling at (4WD), it is considered that the rear wheels 3 are not slipping, and the weight process is started. First, it is determined whether or not the weight processing is being performed. If the weight processing is not being performed, it is determined whether or not “S” seconds have elapsed, and if the “S” seconds have not yet been reached, the weight processing is started. To do.

In the weight processing, "R" seconds (approximately 2
It is determined whether the control in the 4WD state has continued for 2 seconds), and when "R" seconds have elapsed, the number of drive changes between "2WD and 4WD" is added once and the 4WD flag is cleared. Both the one solenoid 59 and the second solenoid 60 are turned off to travel in the "rear two-wheel drive state" (2WD), and during the "S" second travel, the rotational speeds of the front and rear wheels 4, 3 have a certain difference or more. And again "front and rear four-wheel drive state" (4W
Wait for the control instruction of D).

When the count of "S" seconds (approximately 30 seconds) elapses during traveling, the count of the time "S" seconds is cleared and the count number of drive change between "2WD and 4WD" is "S". It is determined whether or not a constant “M” (provisionally 10 times) is exceeded in a second. When it is determined that the number of drive changes between “2WD and 4WD” does not exceed the constant “M”,
The count of the drive change between "2WD and 4WD" is cleared, the "slip control" is terminated, and the "straight ahead control G" described later.
Etc. continue to be controlled.

When it is determined that the count number of drive changes between "2WD and 4WD" exceeds the constant "M", it is determined that the field has a lot of slips, and the count of drive changes between "2WD and 4WD" is determined. While clearing, the 4WD lock flag is turned ON to end the "slip control", and the 4WD lock is continued for a certain period of time. Next, the "straight ahead control G" will be described with reference to FIG.

As described above with reference to FIG. 5, the "straight ahead control G" is a control when the steering angle of the agricultural tractor 14 is "α" (5 degrees) or less, and a "brake flag" described later.
Then, the slip of the rear wheels 3 in the “rear two-wheel drive state” (2WD) in which the “4WD flag” is not turned on is detected, and when there is a certain amount of slip (probably about 8% reduction) (rear) (While the wheels have not completely transmitted the driving force to the ground), the 4WD flag is turned on, the first solenoid 59 is turned on, and the vehicle travels in the "front-rear four-wheel drive state" (4WD). The "straight ahead control G" is continued after "slip control".

When the rear wheel 3 does not slip more than a certain amount (for example, about 8% reduction), it is determined whether the front wheel 4 is rotating faster than the rear wheel 3 at the average peripheral speed.
If the overrun rate of the front wheels 4 exceeds a predetermined numerical value "A" (probably about 5% increase), the brake flag is turned on and the necessity of braking the front wheels 4 is determined by the controller 1.
3, the first solenoid 59 is turned on to drive the vehicle in the "front-rear four-wheel drive state" (4WD), and the process proceeds to "brake control" described later. In this way, the "straight ahead control G" is divided into two types of control, "slip control" and "brake control", and continues.

When the overrun rate of the front wheels 4 is equal to or smaller than the predetermined value "A", the "straight ahead control G" is continued as it is. If the brake flag is ON at the start of the "straight ahead control G", the process immediately shifts to the "brake control". Next, the operation of the "brake control" will be described with reference to FIG. First, when the above-mentioned 4WD lock flag is ON, this "brake control" ends as it is. If the 4WD lock flag is not ON, it is judged whether or not the counting of the time "X" seconds (approximately 30 seconds) is started. If not, the counting of the "X" seconds is started and the front wheels are also started. It is determined whether or not the overrun rate of 4 has reached a predetermined numerical value "A" (probably increased by about 5%). As described above, when the "brake control" is started, the vehicle is traveling in the "front-rear four-wheel drive state" (4WD). Therefore, it is considered that the rear wheels 4 are not slipping, and the weight process is started.

First, it is judged whether or not the time "Y" seconds (approximately 2 seconds) is being counted (whether the weight processing is started?). If not, the count of "X" seconds is counted. It is determined whether or not the time has elapsed, and if the time has not yet reached "X" seconds, the weight process is started. This weight processing is to detect whether or not a control command has been issued for the "front and rear four-wheel drive state" (4WD) for a time of "Y" seconds (approximately 2 seconds). After a while, "2WD and 4W
The number of drive changes between "D" is counted once, the 4WD flag is cleared, and then both the first solenoid 59 and the second solenoid 60 are turned off to set the "rear two-wheel drive state" (2W
The vehicle travels in D) and waits for an instruction of "front-rear four-wheel drive state" (4WD) again while traveling for "X" seconds.

When the count of "X" seconds (approximately 30 seconds) has elapsed, the count of time "X" seconds is cleared and
It is determined whether or not the count number of drive changes between "2WD and 4WD" exceeds a constant "M" (provisionally 5 times).
When it is determined that the drive change count between "2WD and 4WD" does not exceed the constant "M", the drive change count between "2WD and 4WD" is cleared and "brake control" ends. .

When it is determined that the drive change count between "2WD and 4WD" exceeds the constant "M", "2W
The drive change count between "D and 4WD" is cleared and the 4WD lock flag is turned on to perform "brake control".
And the control in the "straight ahead control G" described above is continued. For example, when the driver suddenly brakes while traveling with the agricultural tractor 14, the brakes of the rear wheels 3 and 3 are braked and the aircraft tries to stop. However, when the front wheels 4 and 4 are not simultaneously braked, the aircraft is Since the front wheel 4 side of the vehicle advances at the same traveling speed, the braking effect becomes poor.

In the "brake control", such a state is automatically judged to instantly drive the vehicle in a 4WD lock state, and the braking force of the rear wheel 3 is also driven and interlocked with the front wheel 4. It will increase the power. For example, when traveling on a steep downhill in the “rear two-wheel drive state” (2WD), the rear wheels 3
Even when traveling with the transmission mechanism 2 at a low speed position, the ground may be slippery and the aircraft may slide at a speed higher than the traveling speed of the wheels. In that case, the overrun of the front wheels 4 is determined by the front and rear axis rotation sensors 10 and 9, and the "front and rear four-wheel drive state" (4W
Control to D) to prevent runaway.

When this control operation is a run in which it is determined that the control operation is performed six times or more in "X" seconds, the "front-rear four-wheel drive state" (4WD) is first held. Here, when a switching operation of the main transmission device 34 is performed during the control of FIGS. 5 to 11, the main shift control shown in FIG. 12 is operated in preference to other controls. When the up button or the down button provided on the auxiliary shift lever 64 is pressed, the controller 13
Stores the current drive method (DM).

Then, both the first solenoid 59 and the second solenoid 60 are turned off in response to a command from the controller 13.
Then, it switches to the "rear two-wheel drive state" (2WD). This drive state is maintained for a fixed time (approximately 1-2 seconds).
Next, the reverser clutch is automatically disengaged, at this time,
Rotation sensor 83 provided on the input side of the reverser device 34
Then, the detected values of the rotation sensor 84 provided on the output side are different from each other.

Then, the shifter is moved by the operation of the hydraulic (or electric) actuator 81 or 82, and the main transmission gear is switched to the speed increasing side or the speed reducing side. After the main transmission gear is switched, the reverser clutch is automatically turned on again, and the detected values of the rotation sensors 83 and 84 of both the input and the output match, and the controller 13 recognizes that the reverser clutch is connected.

As described above, the rotation sensor 83,
It is also possible to provide a pressure detecting device instead of 84, detect the pressure rising state of the reverser clutch by the pressure detecting device, and determine that the reverser clutch is connected.
It usually takes 1 to 2 seconds until the reverser clutch is automatically disengaged, the main transmission gear is switched, and the reverser clutch is automatically switched on again. According to the present invention, the rear two-wheel drive state is maintained for a certain period of time after the switching operation command is issued to the main transmission until the switching operation is completed.

Therefore, "front and rear four-wheel drive state" (4WD)
Alternatively, as compared with the “front wheel speed-increasing four-wheel drive state” (4WDD), it is possible to prevent the problem that the efficiency of transmission of the driving force to the ground is reduced, the shift shock is reduced, and the field surface is scraped off. After the "rear two-wheel drive state" (2WD) is maintained for a certain period of time, the stored drive system (DM) is restored, the main shift control subroutine is terminated, and the original control is continued.

[0068]

As described in detail in the above one embodiment, the present invention maintains the rear two-wheel drive state for a certain period of time when the main transmission is switched, regardless of the drive system. Therefore, the rear two-wheel drive state is set during the switching operation of the main transmission, and the shift shock is reduced.

Thus, the abrupt change of the ground driving force at the time of the switching operation of the main transmission is reduced, the surface of the field is not scraped off, and the fine control corresponding to the change of the ground condition during traveling can be performed. As a result, damage to the ground can be minimized, and good ground drive transmission performance can be exhibited during traveling.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a transmission system according to an embodiment of the present invention.

FIG. 2 is a side sectional view of main parts of a direct coupling clutch and a speed increasing clutch.

FIG. 3 is a side view of the entire tractor.

FIG. 4 is a transmission plane diagram in which the whole is developed.

FIG. 5 is a flowchart of the entire four-wheel drive control.

FIG. 6 is a flowchart of turning control F that is a subroutine.

FIG. 7 is a flowchart of turn control that is a subroutine.

FIG. 8 is a flowchart of turn control that is a subroutine.

FIG. 9 is a flowchart of slip control that is a subroutine.

FIG. 10 is a flowchart of a straight ahead control G that is a subroutine.

FIG. 11 is a flowchart of brake control that is a subroutine.

FIG. 12 is a flowchart of a main shift control that is a subroutine.

[Explanation of symbols]

 1 Engine 2 Transmission Mechanism 3 Rear Wheel 4 Front Wheel 5 Rear Wheel Drive Rotation Shaft 6 Front Drive Shaft 7 Direct Connection Clutch 8 Speed-up Clutch 9 Rear Shaft Rotation Sensor 10 Front Shaft Rotation Sensor 11 Steering Angle Sensor 13 Controller 33 Reverser Device 34 Main Shift Device 35 Auxiliary transmission device 64 Auxiliary transmission lever 80 Auxiliary transmission lever position sensor 81,82 Hydraulic actuator 83,84 Rotation sensor

Claims (1)

[Claims] 1. A reverser clutch for powering an engine,
It is transmitted to the rear wheels and front wheels via the main transmission and the auxiliary transmission, and it is possible to automatically switch between the rear two-wheel drive, front-rear four-wheel drive, and front-wheel speed-increasing four-wheel drive. In a four-wheel drive vehicle, a four-wheel drive force is provided, which is provided with control means for holding the drive system to rear two-wheel drive for a certain period of time when a switching operation command of the main transmission is given. Control device.