JP6380019B2 - Work vehicle - Google Patents

Description

  The present invention relates to a four-wheel drive work vehicle used for agriculture, construction, transportation and the like.

  Conventionally, a standard four-wheel drive clutch that switches whether or not the rotation of the rear wheel drive shaft is transmitted to the front wheel drive shaft at the same rotation ratio, and the rotation of the rear wheel drive shaft is increased to the front wheel drive shaft. 2. Description of the Related Art A work vehicle having a speed-up four-wheel drive clutch that switches between transmission and non-transmission is known (see, for example, Patent Document 1).

  In the work vehicle, even if there is a control operation command from the two-wheel drive to the four-wheel drive, the command is not immediately executed, but the rotation speed of the rear wheel drive rotation shaft and the rotation of the front wheel drive rotation shaft are not executed. It is configured to detect the number and the like to determine the road surface condition and determine whether or not the control operation is necessary.

Japanese Patent No. 2536369

  However, the work vehicle described in Patent Document 1 has a problem in that when the vehicle is automatically switched from four-wheel drive to two-wheel drive, the configuration is immediately switched to two-wheel drive, which may give the passenger a sense of incongruity. .

  An object of the present invention is to provide a work vehicle that does not give a sense of incongruity to a passenger when automatically switching from four-wheel drive to two-wheel drive in view of the above-described problems in conventional work vehicles.

In order to achieve the above object, the first present invention provides:
Engine and
A pair of left and right front wheels;
A pair of left and right rear wheels,
A four-wheel drive clutch for switching whether or not to transmit the driving force from the engine to the front wheels;
A rear shaft rotation sensor that detects the number of rotations on the input shaft side of the four-wheel drive clutch;
A front shaft rotation sensor for detecting the rotation speed on the output shaft side of the four-wheel drive clutch;
If the ratio or difference based on the detection result of the rear shaft rotation sensor and the detection result of the front shaft rotation sensor is outside the first specified range in the rear wheel two-wheel drive state, the four wheel drive state is set. When a four-wheel drive clutch is engaged, and the ratio or difference is within the first specified range, a control unit that gradually reduces the connection pressure of the four-wheel drive clutch so as to be in the rear-wheel two-wheel drive state;
Comprising a brake operation detector for detecting the presence or absence of braking operation for stopping the travel of the aircraft, and
The controller, when the brake operation detector detects the brake operation, instead of controlling the connection pressure of the four-wheel drive clutch based on the ratio or difference, controls the connection pressure of the four-wheel drive clutch, it is work vehicle you characterized.

As a result, when the work vehicle is traveling straight in a two-wheel drive state, for example, the ratio or difference between the detection result of the rear axle rotation sensor and the detection result of the front axle rotation sensor deviates more than a specified range. In this state, that is, in a state where one of the front and rear wheels is rotating excessively, tire wear or mud winding occurs on the wheel. Therefore, this can be prevented by switching to four-wheel drive in such a state.
Furthermore, since the vehicle was originally running in a two-wheel drive state, when the abnormality in the ratio or difference in the rotation speed disappears, the connection pressure of the four-wheel drive clutch is gradually lowered to give the passenger a sense of incongruity. Without being able to return to the two-wheel drive state.
This also, when the brake operation irrespective of the ratio or difference of the rotation of the front and rear wheels, and controls the connection pressure such as whole pressure so as to obtain four-wheel drive state for generating a higher braking force.

The second aspect of the present invention
Engine and
A pair of left and right front wheels;
A pair of left and right rear wheels,
A four-wheel drive clutch for switching whether or not to transmit the driving force from the engine to the front wheels;
A rear shaft rotation sensor that detects the number of rotations on the input shaft side of the four-wheel drive clutch;
A front shaft rotation sensor for detecting the rotation speed on the output shaft side of the four-wheel drive clutch;
If the ratio or difference based on the detection result of the rear shaft rotation sensor and the detection result of the front shaft rotation sensor is outside the first specified range in the rear wheel two-wheel drive state, the four wheel drive state is set. A controller that gradually reduces the connection pressure of the four-wheel drive clutch so as to enter the rear-wheel two-wheel drive state when the four-wheel drive clutch is engaged and the ratio or difference falls within the first prescribed range. ,
The ratio or difference based on the detection result of the rear shaft rotation sensor and the detection result of the front shaft rotation sensor is calculated based on the rear shaft rotation speed obtained from the detection result of the rear shaft rotation sensor and the front shaft rotation sensor. It is the ratio or difference with the average front shaft speed obtained from the detection result,
The controller is
When the ratio or difference between the instantaneous value detected by the rear shaft rotation sensor and the instantaneous value detected by the front shaft rotation sensor is within a second specified range including the first specified range, Based on the ratio or difference between the rear shaft rotation speed obtained from the detection result of the rear shaft rotation sensor and the front shaft average rotation speed obtained from the detection result of the front shaft rotation sensor, the four-wheel drive clutch Control the connection pressure,
If the ratio or difference between the instantaneous value detected by the rear shaft rotation sensor and the instantaneous value detected by the front shaft rotation sensor is outside the second specified range, it is detected by the rear shaft rotation sensor. Controlling the connection pressure of the four-wheel drive clutch for a predetermined time based on the ratio or difference between the instantaneous value and the instantaneous value detected by the front shaft rotation sensor;
It is a work vehicle you said.

As a result, when the work vehicle is traveling straight in a two-wheel drive state, for example, the ratio or difference between the detection result of the rear axle rotation sensor and the detection result of the front axle rotation sensor deviates more than a specified range. In this state, that is, in a state where one of the front and rear wheels is rotating excessively, tire wear or mud winding occurs on the wheel. Therefore, this can be prevented by switching to four-wheel drive in such a state.
Furthermore, since the vehicle was originally running in a two-wheel drive state, when the abnormality in the ratio or difference in the rotation speed disappears, the connection pressure of the four-wheel drive clutch is gradually lowered to give the passenger a sense of incongruity. Without being able to return to the two-wheel drive state.
In addition, for example, when the ratio or difference between the instantaneous values of the rear shaft rotational speed and the front shaft rotational speed is within the second specified range, the average rotational speed is obtained for the front shaft rotational speed, and the rear shaft By controlling the connection pressure of the four-wheel drive clutch based on the ratio or difference between the rotational speed and the average rotational speed, the control is stable because it reacts only to continuous causes. If the rear wheel is locked, or if the rear wheel slips when the connection pressure is close to the two-wheel drive state, the instantaneous value ratio or difference between the rear shaft speed and the front shaft speed is outside the second specified range. When this happens, the connection pressure of the four-wheel drive clutch is controlled based on the ratio or difference between the instantaneous values of the rear shaft speed and the front shaft speed instead of the average so that the rear wheel lock and slip can be instantaneously applied. I can respond.

  According to the present invention, it is possible to provide a work vehicle that does not give a sense of incongruity to a passenger when the vehicle is automatically switched from four-wheel drive to two-wheel drive.

Left side view of an agricultural tractor according to an embodiment of the present invention Transmission diagram of the power transmission mechanism of the agricultural tractor of this embodiment Schematic hydraulic circuit diagram for explaining the constant speed switching proportional solenoid valve and the speed increasing switching proportional solenoid valve of the agricultural tractor of the present embodiment The block diagram explaining the control part of the agricultural tractor of embodiment of this invention The schematic diagram which shows the correspondence of the peripheral speed ratio and connection pressure previously stored in the memory part of the control part of the agricultural tractor of this Embodiment Schematic showing the appropriate range of the peripheral speed ratio between the peripheral speed of the front wheel and the peripheral speed of the rear wheel of the agricultural tractor of the present embodiment The schematic diagram which shows the correspondence of the peripheral speed ratio in turning driving | running | working, and the connection pressure previously stored in the memory part of the control part of the agricultural tractor of this Embodiment The figure explaining the optimal state of the circumferential speed ratio Ds between the circumferential speed of the rear wheel of the turning outer side of the agricultural tractor of this embodiment, and the circumferential speed of a front wheel The schematic diagram which shows the operation condition of the various clutches in the agricultural tractor of this Embodiment The schematic diagram of another example which shows the correspondence of the peripheral speed ratio and connection pressure previously stored in the memory part of the control part of the agricultural tractor of this Embodiment Schematic diagram showing an example of the relationship between the peripheral speed ratio of the agricultural tractor of this embodiment and the connection pressure of the constant-speed four-wheel drive clutch in time series

  An embodiment of a work vehicle according to the present invention will be described with reference to the drawings.

  Hereinafter, the agricultural tractor 1 which is an example of the work vehicle of the present invention will be described in detail.

  FIG. 1 is a schematic left side view of an agricultural tractor 1 according to the present embodiment.

  FIG. 2 is a transmission diagram of the power transmission mechanism of the agricultural tractor 1 of the present embodiment.

  As shown in FIG. 1, the agricultural tractor 1 of the present embodiment includes a pair of left and right front wheels 2 and a pair of left and right rear wheels 3, and an engine 5 is installed in the front part of the traveling vehicle body 1 a and a cabin 4 is provided in the rear part. It is the composition provided.

  In the cabin 4, a driver's seat 6, a steering handle 7 and the like are provided.

  Further, the driving force of the engine 5 is appropriately decelerated via the transmission mechanism shown in FIG. 2, and the reduced rotational power is transmitted to the pair of left and right rear wheels 3 and 3 to cause the traveling vehicle body 1a to travel.

  Further, the rotational power transmitted to the rear wheels 3 and 3 is configured to be transmitted to the pair of left and right front wheels 2 and 2 via the constant-speed four-wheel drive clutch 110 or the speed-increasing four-wheel drive clutch 120. . In the present embodiment, the constant-speed four-wheel drive clutch 110 and the speed-increasing four-wheel drive clutch 120 are collectively referred to as a front wheel transmission clutch device 100.

  As shown in FIG. 2, the transmission mechanism of the agricultural tractor 1 according to the present embodiment includes a high / low transmission 11 that shifts in two stages at low speed and high speed, and a main transmission that shifts the low speed into four stages and the high speed into four stages. 12, a forward / reverse clutch device 13 that switches between forward and reverse, a sub-transmission device 14 that performs a four-speed shift for each of the low-speed four-speed rotation and the high-speed four-speed rotation, the above-described front wheel transmission clutch device 100, This is a configuration provided with a PTO transmission transmission 16 that reverses the rotation of the PTO shaft 15 and changes the speed from the first speed to the third speed.

  Further, as shown in FIG. 2, the power that has passed through the auxiliary transmission 14 drives the drive shaft 46, drives the right rear wheel rotation shaft 53R and the left rear wheel rotation shaft 53L via the rear wheel differential mechanism 49 and the like, In this configuration, the pair of left and right rear wheels 3, 3 are rotationally driven.

  Further, the rotation of the drive shaft 46 is caused by an input cylinder shaft 64 that externally fits to the front wheel transmission shaft 62 and supports the input gear 63 via a two-stage gear 61 supported from the take-out gear 60 to the rear PTO transmission shaft 58. Interlock.

  Between the input cylinder shaft 64 and the front wheel transmission shaft 62, a constant speed four-wheel drive clutch 110 in the form of a hydraulic clutch, a speed-up four-wheel drive clutch 120, and speed-up gear sets 67a and 67b are disposed. ing.

  When the constant speed four-wheel drive clutch 110 is connected (engaged), the front wheel transmission shaft 62 is driven integrally with the input cylinder shaft 64, and when the speed-up four-wheel drive clutch 120 is connected (engaged), the speed-up gear In this configuration, the front wheel transmission shaft 62 is driven in an increased speed transmission state via the sets 67a and 67b.

  Further, when the constant speed four-wheel drive clutch 110 is disconnected (disengaged) and the speed-up four-wheel drive clutch 120 is disconnected (disengaged), the input cylinder shaft 64 and the speed increasing gear set 67b are both front wheel transmission shafts. The rotation of the drive shaft 46 is not transmitted to the front wheel transmission shaft 62 because the drive shaft 46 is loosely fitted to the front wheel 62. In this case, only the pair of left and right rear wheels 3 and 3 are driven, and the pair of left and right front wheels 2 and 2 are driven.

  The driving force of the front wheel transmission shaft 62 is configured to rotationally drive the pair of left and right front wheels 2 and 2 via the front wheel differential mechanism 70 and the like.

  The connection pressures of the constant speed four-wheel drive clutch 110 and the speed increase four wheel drive clutch 120 are configured to be changeable and controlled by a constant speed switching proportional solenoid valve 111 and an acceleration switching proportional solenoid valve 121, respectively. (See FIG. 3). Here, FIG. 3 is a schematic hydraulic circuit diagram illustrating the constant speed switching proportional solenoid valve 111 and the speed increasing switching proportional solenoid valve 121.

  That is, the pressure control of the constant-speed four-wheel drive clutch 110 and the speed-up four-wheel drive clutch 120 is configured to variably control the control pressure of the clutch pressing piston (not shown) by the proportional pressure control valve.

  Next, various sensors provided in the power transmission mechanism of the agricultural tractor 1 according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 2, the power transmission mechanism includes a rear shaft rotation sensor 101 that detects the rotational speed of the input cylinder shaft 64 on the input shaft side of the front wheel transmission clutch device 100, and a front wheel on the output shaft side of the front wheel transmission clutch device 100. Front shaft rotation sensor 102 that detects the rotation speed of the transmission shaft 62, left rear wheel rotation sensor 153L that detects the rotation speed of the left rear wheel rotation shaft 53L, and right rear that detects the rotation speed of the right rear wheel rotation shaft 53R. A wheel rotation sensor 153R.

  In addition, a brake operation detection sensor 160 that detects the presence or absence of a “brake operation” that depresses a brake pedal (not shown) to stop traveling, and a steering angle sensor 170 that detects the steering angle of the front wheels 2 by the operation of the steering handle 7 ( 4).

  The brake operation detection sensor 160 of the present embodiment is an example of the brake operation detector of the present invention, and the steering angle sensor 170 of the present embodiment is an example of the steering angle detector of the present invention.

  Next, the control unit 200 that controls the connection pressure of the constant-speed four-wheel drive clutch 110 and the connection pressure of the speed-up four-wheel drive clutch 120 based on the detection results from the various sensors described above will be described with reference to FIGS. 8 will be used for explanation.

  FIG. 4 is a block diagram illustrating the control unit 200 of the agricultural tractor 1 according to the present embodiment.

  FIG. 5 is a schematic diagram showing a correspondence relationship between the peripheral speed ratio Ds and the connection pressure P, which is stored in the memory unit 210 of the control unit 200 in advance.

  Here, the peripheral speed of the rear wheel 3 is the ratio of the rotational speed of the rear wheel 3 when the rotational speed of the input cylindrical shaft 64 is based on the rotational speed of the input cylindrical shaft 64 detected by the rear shaft rotation sensor 101. And the peripheral speed of the front wheel 2 is obtained by multiplying the rotation speed of the front wheel transmission shaft 62 with the rotation speed of the front wheel transmission shaft 62 as a reference. This is obtained by multiplying the rotation speed ratio of the front wheel 2 by the diameter of the front wheel 2.

  FIG. 6 is a schematic diagram showing an appropriate range of the peripheral speed ratio between the peripheral speed of the front wheels and the peripheral speed of the rear wheels.

  As shown in FIG. 4, with respect to the control unit 200, the rear shaft rotation sensor 101, the front shaft rotation sensor 102, the left rear wheel rotation sensor 153 </ b> L, the right rear wheel rotation sensor 153 </ b> R, the brake operation detection sensor 160, and the steering angle sensor 170. The detection result from is sent.

  Here, (1) when the agricultural tractor 1 is traveling straight forward at 2WD (two-wheel drive), for example, on a road outside the field, the controller 200 travels straight from 2WD to constant speed 4WD (constant speed four-wheel drive). And (2) when the agricultural tractor 1 starts traveling forward at a constant speed 4WD (constant speed four-wheel drive) and then turning at the end of the field, for example, during a tilling operation on the field The control unit 200 automatically switches from the constant speed 4WD to the increased speed 4WD (accelerated four-wheel drive), and after returning to the straight traveling after turning, it automatically switches to the constant speed 4WD again. explain.

(1) For straight running:
Here, the case where the brake operation is not performed and the case where the brake operation is performed will be described separately.

  (1-1) When the control unit 200 determines from the detection results of the steering angle sensor 170 and the brake operation detection sensor 160 that the agricultural tractor 1 is traveling forward and the brake operation is not performed, FIG. The following control is performed using the first control characteristic line 501 in the middle.

  That is, the control unit 200 calculates the peripheral speed ratio Ds based on the number of rotations detected by the rear shaft rotation sensor 101 and the number of rotations detected by the front shaft rotation sensor 102, and the value is within an appropriate range. Determine if it is within. If the peripheral speed ratio Ds is within an appropriate range (in the range where the peripheral speed ratio Ds shown in FIG. 5 is greater than or equal to D1 and less than D2, it is indicated as “first specified range” in the figure), 2WD is set. For example, if it is determined that the peripheral speed ratio Ds is Dα (Dα> D2), the constant-speed four-wheel drive clutch 110 is connected (entered) to switch from 2WD to constant-speed 4WD. The connection pressure P in this case is the total pressure P1 of the constant-speed four-wheel drive clutch 110 as shown by the first control characteristic line 501 in FIG.

  The appropriate range of the present embodiment corresponds to an example of the first specified range of the present invention.

  Thereafter, the control unit 200 calculates the peripheral speed ratio Ds based on the number of rotations detected by the rear shaft rotation sensor 101 and the number of rotations detected by the front shaft rotation sensor 102, and the value is within an appropriate range. It is determined whether or not it is within the appropriate range, and the same control as described above is repeated until it falls within the proper range.

  The pressure increase from the connection pressure P0 to P1 when switching from 2WD to constant speed 4WD and the pressure decrease from the connection pressure P1 to P0 when switching from constant speed 4WD to 2WD may be performed gradually or suddenly. However, it is more preferable to increase and decrease pressure smoothly so that the passenger does not feel shock (discomfort).

  As a result, the driving state of the front wheels 2 can be made appropriate, excessive rotation of the front wheels 2 can be suppressed, and mud wrapping and tire wear can be prevented.

  Here, the appropriate range of the peripheral speed ratio between the peripheral speed of the front wheel 2 and the peripheral speed of the rear wheel 3 will be described with reference to FIG. FIG. 6 is a diagram illustrating an appropriate range of the peripheral speed ratio between the peripheral speed of the front wheels and the peripheral speed of the rear wheels.

  The horizontal axis in FIG. 6 indicates the peripheral speed of the rear wheel, and the vertical axis indicates the peripheral speed of the front wheel. The solid line in FIG. 6 is an optimum state line 300 that shows the optimum state in which the peripheral speed of the rear wheel and the peripheral speed of the front wheel coincide with each other, and the broken line in FIG. 6 is a front wheel overrun appropriate limit line 310 indicating an appropriate limit in a state in which the rear wheel slips, and a one-dot chain line in FIG. 6 indicates a rear wheel slip indicating the appropriate limit in a state in which the rear wheel 3 is rotated too much compared to the front wheel 2. This is the appropriate limit line 320.

  That is, the peripheral speed ratio between the peripheral speed of the front wheels and the peripheral speed of the rear wheels is determined by the front wheel overrun appropriate limit line 310 indicating the appropriate limit of the front wheel overrun state shown in FIG. If it is within the range between the rear wheel slip appropriate limit line 320 shown, it can be said that the driving state of the front wheels is appropriate.

  Here, the lower limit reference value D1 of the first specified range (the above appropriate range) shown in FIG. 5 is based on the slope of the rear wheel slip limit line 320, and the upper limit reference value D2 is the slope of the front wheel overrun appropriate limit line 310. It is a fixed value determined based on each.

  The reference values D1 and D2 may be configured to change corresponding to the peripheral speed of the rear wheels.

  (1-2) When the control unit 200 determines from the detection results of the steering angle sensor 170 and the brake operation detection sensor 160 that the agricultural tractor 1 is traveling forward and the brake operation is performed, the second part in FIG. The following control is performed using the control characteristic line 502.

  During the brake operation, it is required to smoothly and reliably stop the traveling vehicle body 1a. For this reason, the control unit 200 controls the constant-speed four-wheel to switch from 2WD to constant-speed 4WD regardless of the rotational speed detected by the rear-axis rotational sensor 101 and the rotational speed detected by the front-axis rotational sensor 102. The drive clutch 110 is connected (engaged), and the connection pressure P is determined as the total pressure P1 using the second control characteristic line 502 (see FIG. 5) stored in the memory unit 210 in advance. A command is issued to the constant velocity switching proportional solenoid valve 111 to output the connection pressure of the total pressure P1.

  In FIG. 5, the second control characteristic line 502 is represented by a one-dot chain line in which the connection pressure P shown on the vertical axis is the total pressure P1 regardless of the peripheral speed ratio Ds, but the peripheral speed ratio Ds is from 0 to D1. The first control characteristic line 501 represented by a solid line overlaps between the two and the range exceeding D2.

  Note that, when the pressure is increased toward the connection pressure P1, the impact at the time of stopping is less when the pressure is increased by drawing a smoother curve than when the pressure is increased rapidly.

  As a result, the connection pressure P can be variably controlled along a predetermined first control characteristic line 501 so that the driving state of the front wheels 2 is appropriate when the brake is not operated, and the connection pressure is increased to increase the braking force when the brake is operated. Can be controlled to the total pressure P1 (see FIG. 5).

(2) About turning:
When it is determined from the detection result of the steering angle sensor 170 that the traveling vehicle body 1a has started turning counterclockwise, for example, the control unit 200 uses the third control characteristic line 503 in FIG. Take control. FIG. 7 shows the correspondence between the peripheral speed ratio Ds and the connection pressure P of the speed-up four-wheel drive clutch 120 stored in advance in the memory unit 210 of the control unit 200 of the agricultural tractor 1 of the present embodiment. It is a schematic diagram which shows.

  In the present embodiment, in the case of turning, the optimum state of the peripheral speed ratio between the peripheral speed of the rear wheel outside the turn and the peripheral speed of the front wheel is the case of the straight traveling described in item (1). Since this is different from the optimum state (see reference numeral 300 in FIG. 6), this point will be described with reference to FIG.

  FIG. 8 is a diagram for explaining an optimum state of the peripheral speed ratio Ds (see FIG. 7) between the peripheral speed of the rear wheel and the peripheral speed of the front wheel.

  That is, in this embodiment, in the case of turning, as shown in FIG. 8, the state in which the peripheral speed of the front wheels is always slightly higher than the peripheral speed of the rear wheels outside the turn is determined as the optimum state. The time optimum state line 400 was used.

  A line indicating a peripheral speed matching state in which the peripheral speed of the front wheel and the peripheral speed of the rear wheel outside the turn coincide with each other is referred to as a peripheral speed matching state line 410.

  Further, in the present embodiment, in FIG. 8, the inclination of the turning optimum state line 400 at the peripheral speed of the rear wheel outside the turn is determined as the reference value D3. Here, although the reference value D3 is a fixed value, it may be configured to change in accordance with the peripheral speed of the rear wheel on the outside of the turn.

  Then, the control unit 200 increases the connection pressure P of the speed-up four-wheel drive clutch 120 if the peripheral speed ratio Ds (see FIG. 7) is less than D3, and if it is greater than or equal to D3, the speed-up four-wheel drive clutch. The connection pressure P of 120 was made low.

  According to this, since the connection pressure is controlled so that the circumferential speed ratio Ds moves on the optimum state line 400 at the time of turning, the behavior of the front wheel always outputs a driving force and slightly pulls the rear wheel, and the turning performance. Will improve.

  The connection pressure P3 corresponding to the optimum circumferential speed ratio D3 may be configured to vary depending on the road surface condition.

  Here, the description returns to the control unit 200 using the third control characteristic line 503 in FIG. 7 again.

  When it is determined from the detection result of the steering angle sensor 170 that the traveling vehicle body 1a has started to turn counterclockwise, the control unit 200 switches the constant speed 4WD from the constant speed 4WD to the speed increase 4WD in the front wheel transmission clutch device 100. The wheel drive clutch 110 is disconnected and the speed-up four-wheel drive clutch 120 is connected. Then, the third control characteristic line 503 (see FIG. 7) stored in advance in the memory unit 210 is used to determine the connection pressure Pβ corresponding to the peripheral speed ratio Dβ, and to the speed increasing switching proportional solenoid valve 121. Command to output the connection pressure Pβ.

  When calculating the peripheral speed ratio Ds in counterclockwise turning, the control unit 200 multiplies the rotational speed of the right rear wheel detected by the right rear wheel rotation sensor 153R by the diameter of the rear wheel 3. To obtain the peripheral speed Sr of the right rear wheel and the ratio of the rotational speed of the front wheel 2 to the rotational speed of the front wheel transmission shaft 62 detected by the front shaft rotation sensor 102 based on the rotational speed of the front wheel transmission shaft 62. Then, the peripheral speed Sf of the front wheel is obtained by multiplying the diameter of the front wheel 2 and calculated by calculating Ds = Sf / Sr.

  Subsequently, during the counterclockwise turn, the control unit 200 determines a fixed time interval based on the rotation speed detected by the right rear wheel rotation sensor 153R outside the turn and the rotation speed detected by the front shaft rotation sensor 102. Then, the peripheral speed ratio Ds is calculated, and the same control as described above is repeated so that Ds = D3. If the peripheral speed ratio Ds <D3, the connection pressure P of the speed-up four-wheel drive clutch 120 is increased. If the peripheral speed ratio Ds> D3, the connection pressure P of the speed-up four-wheel drive clutch 120 is lowered.

  The method of increasing or decreasing pressure toward the determined connection pressure Pβ may be increased to draw a smooth curve or may be increased rapidly.

  As a result, when turning, the appropriate driving torque in the accelerated state is given to the front wheels 2, so that the front wheels 2 act like a brake or are idle due to the field conditions (a state where the driving force is low). It can be prevented.

  Next, the operation in the case where the agricultural tractor 1 according to the present embodiment travels straight on the road, enters the field, and performs the cultivation work in the field will be described with reference to FIG.

  FIG. 9 is a schematic diagram illustrating an example of the operation state of the above-described various clutches in the agricultural tractor 1.

  As shown in FIG. 9, in the road travel distance 600, since the vehicle travels substantially straight, the control unit 200 determines that the peripheral speed ratio Ds is, for example, Dα (Dα> D2) during travel by 2WD (FIG. 9). 5) The constant-speed four-wheel drive clutch 110 is connected (engaged) to switch from 2WD to constant-speed 4WD. In this case, how to determine the connection pressure P is as described with reference to FIG.

  Thereafter, in the farm field entry process 610 that enters the farm field and travels to the tillage start position, the control unit 200 determines that the peripheral speed ratio Ds is substantially larger than D2, and therefore, the constant speed is set to switch from 2WD to constant speed 4WD. The four-wheel drive clutch 110 is connected (engaged), and the connected state is maintained up to, for example, a tilling start position while performing the determination described in FIG.

  Next, in the tilling work process 620, when the work implement (not shown) is lowered by the operator's operation and the tilling work is started, the control unit 200 performs, for example, the determination described in FIG. During straight running, plowing work is performed at a constant speed of 4WD, and when turning to the end of the field starts turning, the turning direction is determined based on the detection result of the steering angle sensor 170, and as described with reference to FIG. In order to switch to the speed increase 4WD, the speed increase four-wheel drive clutch 120 is connected (engaged), and the connection pressure P is feedback-controlled so that the peripheral speed ratio Ds matches D3.

  Then, when the turn is completed and the straight traveling is resumed, the control unit 200 determines the peripheral speed ratio Ds (see FIG. 5) and switches from the increased speed 4WD to the constant speed 4WD. The above operation is repeated during tillage work.

  Thereby, when the agricultural tractor 1 is traveling straight, for example, if a difference occurs between the peripheral speeds of the front wheels and the rear wheels, the connection pressure of the four-wheel drive clutch corresponds to the magnitude of the difference. By controlling the value, the driving state of the front wheels can be made appropriate, excessive rotation of the front wheels can be suppressed, and mud wrapping and tire wear can be prevented.

  When it is determined from the detection result of the steering angle sensor 170 that the agricultural tractor 1 is turning, the front wheel transmission clutch device 100 is switched to transmit the driving force at an increased speed to the front wheels, and the front wheels are appropriate for the front wheels. Can provide a stable driving torque and can perform stable turning.

  In the above embodiment, as indicated by the first control characteristic line 501 in FIG. 5, the control unit 200 determines the value of the peripheral speed ratio Ds when the peripheral speed ratio Ds is outside the first specified range. Regardless, the configuration in which the total pressure P1 is uniformly applied as the connection pressure P of the constant-speed four-wheel drive clutch 110 has been described. However, the present invention is not limited to this. For example, as shown in FIG. Is equal to or greater than D1 and less than D2, by setting the connection pressure P of the constant-speed four-wheel drive clutch 110 to P0, the constant-speed four-wheel drive clutch 110 is set to the “disengaged” state and 2WD running is maintained, but less than D1 Alternatively, if it is D2 or more, the 2WD is switched to the constant speed 4WD, the connection pressure P corresponding to the value of the peripheral speed ratio Ds is determined, and the constant speed four-wheel drive clutch is determined using the determined connection pressure P. It is a configuration that maintains the connection state of 110 It may be. For example, in FIG. 10, when the peripheral speed ratio is Dα, the control unit 200 uses the fourth control characteristic line 504 determined in advance to set the connection pressure P to Pα (Pα <P1). Here, FIG. 10 is a schematic diagram of another example showing a correspondence relationship between the peripheral speed ratio and the connection pressure, which is stored in advance in the memory unit 210 of the control unit 200 of the agricultural tractor 1 of the present embodiment. .

  In the above embodiment, the reference values D1 and D2 (see FIG. 5) for determining whether the constant-speed four-wheel drive clutch 110 is connected or disconnected have been described as being fixed values. The values D1 and D2 may be fixed values such as the average value of D1 and D2, the maximum value of D1 and D2, or other values, and are determined according to the peripheral speed of the rear wheels. It is good also as a structure to be made.

  In the above-described embodiment, the reference value D3 (see FIG. 7) for determining the connection pressure P of the speed-up four-wheel drive clutch 120 has been described as being a fixed value. May be a fixed value such as the average value of D3, the maximum value of D3, or other values, or may be determined according to the peripheral speed of the rear wheel outside the turn.

  Moreover, in the said embodiment, the control part 200 of the agricultural tractor 1 controls the connection pressure of the constant speed four-wheel drive clutch 110 at the time of switching from 2WD to constant speed 4WD based on a predetermined rule at the time of straight traveling. Configuration (see FIGS. 5 and 10), and a configuration for controlling the connection pressure of the speed-up four-wheel drive clutch 120 based on another predetermined rule when switching from the constant speed 4WD to the speed-up 4WD during turning. However, the present invention is not limited to this. For example, a configuration that realizes either one of the control during straight traveling and the control during turning traveling may be adopted. .

  In the above-described embodiment, the configuration in which 2WD is executed if the circumferential speed ratio Ds is within the appropriate range, that is, if the reference value D1 is less than D2 has been described. Until the ratio Ds reaches the optimum state line 300 (see FIG. 6), the constant speed 4WD may be executed and the control for setting the connection pressure lower may be performed. Further, in this configuration, the relationship between the front wheel peripheral speed and the rear wheel peripheral speed is above the front wheel overrun appropriate limit line 310 shown in FIG. 6 (ie, the overrun large zone), and the rear wheel When it is below the slip appropriate limit line 320 (that is, the large slip zone), the connection pressure of the constant-speed four-wheel drive clutch 110 is set higher. Furthermore, in this configuration, the clutch material of the constant-speed four-wheel drive clutch 110 may be made of a material that is resistant to sliding such as carbon, and the rotation speed can be controlled while generating a sliding torque. As a result, by controlling the appropriate driving force in relation to the road surface while sliding the clutch surface, it is possible to always realize a drive with less wear with the appropriate driving force.

  In the above-described embodiment, in the straight traveling, the peripheral speed ratio Ds between the peripheral speed of the rear wheels and the peripheral speed of the front wheels is calculated, and the connection pressure of the constant-speed four-wheel drive clutch 110 is calculated based on the peripheral speed ratio Ds. However, the present invention is not limited to this. For example, even if the constant pressure four-wheel drive clutch 110 connection pressure is determined using the ratio or difference between the rotational speed of the rear wheels and the rotational speed of the front wheels, good. Further, in this case, as long as the number of rotations of the rear wheel and the number of rotations of the front wheel are required, a configuration using the number of rotations at any location may be used.

  Further, in the above-described embodiment, during turning, the peripheral speed ratio Ds between the peripheral speed of the rear wheels outside the turn and the peripheral speed of the front wheels is calculated, and the speed-up four-wheel drive clutch 120 is calculated based on the peripheral speed ratio Ds. However, the present invention is not limited to this. For example, the connection pressure of the speed-up four-wheel drive clutch 120 is determined using the ratio or difference between the rotation speed of the rear wheel and the rotation speed of the front wheel. It may be configured to determine. Further, in this case, as long as the rotation speed of the rear wheel and the rotation speed of the front wheel are calculated, the rotation speed at any place may be used.

  Further, in the above-described embodiment, the description has been made centering on the configuration for calculating the peripheral speed ratio based on the rotational speed of the instantaneous value of the rear wheel and the front wheel detected at a certain point in straight traveling, but the present invention is not limited to this. For example, the constant-speed four-wheel drive clutch is based on the ratio or difference between the rear shaft rotation speed obtained from the detection result of the rear shaft rotation sensor 101 and the front shaft average rotation speed obtained from the detection result of the front shaft rotation sensor 102. The structure which controls the connection pressure of 110 may be sufficient. As a result, the connection pressure can be stably controlled even with respect to frequent fluctuations in the rotational speed of the front wheels 2.

  Further, in the above-described embodiment, the description has been made centering on the configuration for calculating the peripheral speed ratio based on the rotational speed of the instantaneous value of the rear wheel and the front wheel detected at a certain point in straight traveling, but the present invention is not limited to this. For example, as shown in FIG. 11, the control unit 200 (1) a ratio or difference between the instantaneous value detected by the rear shaft rotation sensor 101 and the instantaneous value detected by the front shaft rotation sensor 102 (reference numeral 710 in FIG. 11). Reference) is within a predetermined second specified range (see FIG. 11) including the first specified range (see FIG. 11), the rear shaft rotation speed obtained from the detection result of the rear shaft rotation sensor 101 And the connection pressure of the constant-speed four-wheel drive clutch 110 is controlled based on the ratio or difference (see reference numeral 720 in FIG. 11) between the average rotational speed of the front shafts obtained from the detection result of the front shaft rotation sensor 102 and (2 ) By rear shaft rotation sensor 101 If the ratio or difference (see reference numeral 710 in FIG. 11) between the detected instantaneous value and the instantaneous value detected by the front shaft rotation sensor 102 is outside the second specified range, it is detected by the rear shaft rotation sensor 101. Constant-speed four-wheel drive clutch for a predetermined time (see Tw in FIG. 11) based on the ratio or difference (see reference numeral 710 in FIG. 11) between the instantaneous value detected and the instantaneous value detected by the front shaft rotation sensor 102 The structure which controls the connection pressure of 110 may be sufficient.

  Here, FIG. 11 is a schematic diagram showing an example of the relationship between the peripheral speed ratio Ds (front wheel / rear wheel) of the agricultural tractor 1 of this embodiment and the connection pressure P of the constant speed four-wheel drive clutch 110 in time series. FIG.

  Thereby, for example, when the ratio or difference (see reference numeral 710 in FIG. 11) of the instantaneous value between the rear shaft rotational speed and the front shaft rotational speed is within the second specified range, the average rotational speed with respect to the front shaft rotational speed. And the connection pressure of the constant-speed four-wheel drive clutch 110 is controlled based on the ratio or difference (see reference numeral 720 in FIG. 11) between the rear shaft rotational speed and the front shaft average rotational speed. When the driving state is appropriate and the rear wheel 3 is locked during brake operation, or when the rear wheel 3 slips when the connection pressure is close to two-wheel driving, the instantaneous rotation speed between the rear axle and the front axle When the value ratio or difference (see reference numeral 710 in FIG. 11) is outside the second specified range, it is not an average, but the instantaneous value ratio or difference between the rear shaft speed and the front shaft speed (FIG. 11). The reference pressure of the constant-speed four-wheel drive clutch is controlled based on And in, it can respond instantly to the rear wheels lock and slip.

  Here, the first specified range of the present embodiment corresponds to an example of the first specified range of the present invention, and the second specified range of the present embodiment corresponds to an example of the second specified range of the present invention.

  Here, in the above configuration, an example of control of the connection pressure P of the constant-speed four-wheel drive clutch 110 based on the peripheral speed ratio Ds (front wheel / rear wheel) by the control unit 200 will be described with reference to FIG. This will be explained in series.

  In FIG. 11, the change curve of the front wheel rotational speed is indicated by a solid line for the instantaneous value curve 701 of the front wheel rotational speed, and is indicated by a broken line for the average value curve 702 of the front wheel rotational speed. The change curve of the peripheral speed ratio Ds (front wheel peripheral speed / rear wheel peripheral speed) is a solid line for the instantaneous value peripheral speed ratio curve 710 based on the instantaneous value of the rear wheel speed and the instantaneous value of the front wheel speed. The average peripheral speed ratio curve 720 based on the instantaneous value of the rear wheel rotational speed and the average rotational speed of the front wheel rotational speed is indicated by a broken line. The first specified range is a range of 1.1 to 1.6, and the second specified range is a range of 0.4 to 2.0.

  As shown in FIG. 11, at the time t1, the instantaneous value peripheral speed ratio curve 710 is within the second specified range, and the average value peripheral speed ratio curve 720 is not outside the first specified range. The wheel drive clutch 110 remains in the “disengaged” state, that is, the connection pressure is P0.

  Next, at the time t2, since the instantaneous value peripheral speed ratio curve 710 is within the second specified range and the average value peripheral speed ratio curve 720 is outside the first specified range, the constant speed four-wheel drive clutch 110 enters the “ON” state and reaches the connection pressure P1 at time t3.

  Thereafter, at time t4, the average peripheral speed ratio curve 720 falls within the first specified range, so that the connection pressure of the constant-speed four-wheel drive clutch 110 is from time t4 to time t5 in order to set the two-wheel drive state. It gradually decreases during the period of time and becomes completely “OFF” at time t5.

  Next, since the instantaneous value circumferential speed ratio curve 710 is outside the second specified range at time t6, the constant speed regardless of whether the average value circumferential speed ratio curve 720 is outside the first specified range or not. The four-wheel drive clutch 110 enters the “ON” state and reaches the connection pressure P1 at time t7. Thereafter, at time t8, the connection pressure gradually decreases from time t8 to time t9, and is completely turned off at time t9. In this case, during a predetermined time Tw, that is, from time t6 to t8, the constant-speed four-wheel drive clutch 110 is substantially applied with P1 as the connection pressure, and after time t9, returns to the two-wheel drive state.

  Here, around the time t6, the instantaneous value peripheral speed ratio curve 710 suddenly falls below the lower limit value 0.4 of the second specified range because the rear wheel is rotating, but the instantaneous value of the rotational speed of the front wheel is Is extremely reduced (see instantaneous value curve 701 around time t6 in FIG. 11), that is, the rear wheels are in a slip state.

  In FIG. 11, since the cornering is started slightly before time t9, the constant-speed four-wheel drive clutch 110 based on the first prescribed range and the second prescribed range, which has been used in the straight traveling, is used. The connection pressure is not controlled during turning. Instead, as explained in the above item (2), if the peripheral speed ratio Ds <D3 in order to make the peripheral speed ratio Ds coincide with the optimal peripheral speed ratio D3, the connection pressure P of the speed-up four-wheel drive clutch 120 is increased. If the peripheral speed ratio Ds> D3, the feedback control is performed to lower the connection pressure P of the speed-up four-wheel drive clutch 120. As a result, after time t9, the peripheral speed ratio Ds (front wheel peripheral speed / rear wheel peripheral speed) maintains a high value.

  In the configuration example described with reference to FIG. 11, when the instantaneous value peripheral speed ratio curve 710 is outside the second specified range, whether the average value peripheral speed ratio curve 720 is outside the first specified range or not. Regardless, the control in which P1 is substantially applied as the connection pressure to the constant-speed four-wheel drive clutch 110 for a certain time Tw has been described. However, the present invention is not limited to this. For example, the instantaneous value peripheral speed ratio curve 710 is the second specified range. If the average value circumferential speed ratio curve 720 goes out of the first specified range at the same time when the average value peripheral speed ratio curve 720 goes out of the first specified range, the average value peripheral speed ratio curve 720 falls within the predetermined time Tw. It is also possible to perform a control in which P1 is substantially applied as the connection pressure of the constant velocity four-wheel drive clutch 110, whichever is longer.

  In the configuration example described with reference to FIG. 11, the configuration in which the total pressure P1 is uniformly applied as the connection pressure to the constant-speed four-wheel drive clutch 110 if the condition is satisfied regardless of the value of the peripheral speed ratio Ds has been described. For example, the connection pressure corresponding to the value of the peripheral speed ratio Ds is determined, and the connection state of the constant-speed four-wheel drive clutch 110 is maintained using the determined connection pressure P. Also good.

  In the above embodiment, the configuration in which the turning direction is detected by the steering angle sensor 170 has been described. However, the present invention is not limited to this, and for example, the right rear wheel rotation sensor 153R and the left rear wheel rotation are not provided without the steering angle sensor 170 being provided. The configuration may be such that the rear wheel having the higher rotation speed is obtained from the respective detection results of the sensor 153L, and the turning direction is determined to be the direction opposite to the obtained position of the rear wheel.

  Further, in the above embodiment, in the turning traveling, the configuration for determining the connection pressure of the speed-up four-wheel drive clutch 120 so as to turn in a state in which the front wheels always output driving force and slightly pull the rear wheels has been described. Not limited to this, for example, immediately after the start of turning, the connection pressure of the speed-up four-wheel drive clutch 120 is determined so as to turn in a state in which the front wheels output driving force and slightly pull the rear wheels. The connection pressure may be controlled so that the peripheral speed of the rear wheel and the peripheral speed of the rear wheel outside the turn coincide with each other. As a result, the shock of switching to the increased speed 4WD at the start of turning is eased.

  Further, in the above embodiment, during turning, the peripheral speed of the front wheels is always kept slightly higher than the peripheral speed of the rear wheels outside the turn, that is, the peripheral speed ratio Ds is the optimum state during turning. Although the configuration has been described in which the connection pressure of the speed-up four-wheel drive clutch 120 is controlled so as to be on the line 400 (see FIG. 8), the present invention is not limited to this. A configuration in which the connection pressure is controlled so as to move in a range surrounded by the fast coincidence state line 410 may be used. In this configuration, the connection pressure P is different from the above configuration in that the connection pressure P shows the same value in the range of the peripheral speed ratio of 1 to D3 in FIG.

  Further, in the above-described embodiment, the configuration in which the connection pressure of the speed-up four-wheel drive clutch 120 is controlled so that the peripheral speed ratio Ds is on the turning optimum state line 400 during turning (see FIG. 8) will be described. However, the present invention is not limited to this. For example, the connection pressure of the speed-up four-wheel drive clutch 120 is controlled so that the peripheral speed ratio Ds becomes 1, that is, the peripheral speed of the front wheels matches the peripheral speed of the rear wheels outside the turn. The structure which is made may be sufficient.

  Further, the front wheel speed increasing gear of the speed increasing four-wheel drive clutch 120 of the above-described embodiment may be configured with a gear having a rotation ratio of twice or more. In other words, by configuring the maximum with a gear that generates twice or more the number of revolutions, torque control by controlling the connection pressure of the four-wheel drive clutch 120 can be controlled with appropriate torque depending on the road surface condition. It becomes possible.

  Further, the clutch material of the constant speed four-wheel drive clutch 110 and the speed-increasing four-wheel drive clutch 120 of the above embodiment is made of a material that is resistant to slip such as carbon, and can control the rotation speed while generating a sliding torque. It is also good.

  As a result, by controlling the appropriate driving force in relation to the road surface while sliding the clutch surface, it is possible to always realize a drive with less wear with the appropriate driving force.

  Moreover, in the said embodiment, although the agricultural tractor was demonstrated as an example of a working vehicle, it is not restricted to this, For example, it may be a tractor used for construction, conveyance, etc. besides agriculture, It is restricted to a tractor For example, other work vehicles may be used.

  The work vehicle of the present invention has an effect that the driving state of the front wheels can be made appropriate, and is useful as a work vehicle such as a tractor used for agriculture, construction, transportation, or the like.

DESCRIPTION OF SYMBOLS 1 Agricultural tractor 1a Traveling vehicle body 2 Front wheel 3 Rear wheel 4 Cabin 5 Engine 11 High / low-speed transmission 12 Main transmission 13 Forward / reverse clutch device 14 Subtransmission 15 PTO shaft 16 PTO system transmission transmission 100 Front wheel transmission clutch device 101 Rear shaft rotation Sensor 102 Front shaft rotation sensor 110 Constant speed four-wheel drive clutch 120 Increased speed four-wheel drive clutch 200 Control unit

Claims (2)

Engine and
A pair of left and right front wheels;
A pair of left and right rear wheels,
A four-wheel drive clutch for switching whether or not to transmit the driving force from the engine to the front wheels;
A rear shaft rotation sensor that detects the number of rotations on the input shaft side of the four-wheel drive clutch;
A front shaft rotation sensor for detecting the rotation speed on the output shaft side of the four-wheel drive clutch;
If the ratio or difference based on the detection result of the rear shaft rotation sensor and the detection result of the front shaft rotation sensor is outside the first specified range in the rear wheel two-wheel drive state, the four wheel drive state is set. When a four-wheel drive clutch is engaged, and the ratio or difference is within the first specified range, a control unit that gradually reduces the connection pressure of the four-wheel drive clutch so as to be in the rear-wheel two-wheel drive state;
Comprising a brake operation detector for detecting the presence or absence of braking operation for stopping the travel of the aircraft, and
The controller, when the brake operation detector detects the brake operation, instead of controlling the connection pressure of the four-wheel drive clutch based on the ratio or difference, It controls the connection pressure of the four-wheel drive clutch, work vehicle you wherein a. Engine and
A pair of left and right front wheels;
A pair of left and right rear wheels,
A four-wheel drive clutch for switching whether or not to transmit the driving force from the engine to the front wheels;
A rear shaft rotation sensor that detects the number of rotations on the input shaft side of the four-wheel drive clutch;
A front shaft rotation sensor for detecting the rotation speed on the output shaft side of the four-wheel drive clutch;
If the ratio or difference based on the detection result of the rear shaft rotation sensor and the detection result of the front shaft rotation sensor is outside the first specified range in the rear wheel two-wheel drive state, the four wheel drive state is set. A controller that gradually reduces the connection pressure of the four-wheel drive clutch so as to enter the rear-wheel two-wheel drive state when the four-wheel drive clutch is engaged and the ratio or difference falls within the first prescribed range. ,
The ratio or difference based on the detection result of the rear shaft rotation sensor and the detection result of the front shaft rotation sensor is calculated based on the rear shaft rotation speed obtained from the detection result of the rear shaft rotation sensor and the front shaft rotation sensor. It is the ratio or difference with the average front shaft speed obtained from the detection result,
The controller is
When the ratio or difference between the instantaneous value detected by the rear shaft rotation sensor and the instantaneous value detected by the front shaft rotation sensor is within a second specified range including the first specified range, Based on the ratio or difference between the rear shaft rotation speed obtained from the detection result of the rear shaft rotation sensor and the front shaft average rotation speed obtained from the detection result of the front shaft rotation sensor, the four-wheel drive clutch Control the connection pressure,
If the ratio or difference between the instantaneous value detected by the rear shaft rotation sensor and the instantaneous value detected by the front shaft rotation sensor is outside the second specified range, it is detected by the rear shaft rotation sensor. Controlling the connection pressure of the four-wheel drive clutch for a predetermined time based on the ratio or difference between the instantaneous value and the instantaneous value detected by the front shaft rotation sensor;
Work vehicle you, characterized in that.

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