JP2018154253A - Differential restriction device for wheel loader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential restriction device for a wheel loader having an automatic diff-lock control function for slip prevention in each of a travel operation and a digging operation.SOLUTION: With a wheel loader 1 of the present invention, a torque value of each of left and right axle shafts 31a and 31b included in an axle device 12 is measured by a torque measuring device. An axle control device 50 performs variable control of amount of differential restriction (lock rate) of a differential restriction mechanism 40 so that wheels attached to the axle shafts 31a and 31b which have a smaller or greater torque value do not slip and break in a travel state or digging state of the wheel loader 1.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a differential limiting device for a wheel loader used for excavation work at a construction site or a mine.

  The wheel loader is connected to the front side of the rear vehicle body so that the front vehicle body can swing in the left-right direction, and a work device including an arm, a bucket, and the like is attached to the front vehicle body. On the other hand, an engine, a torque converter, a transmission, a hydraulic pump, and the like are mounted on the rear body, and engine power is transmitted to the transmission via the torque converter. Further, the front body and the rear body are provided with axle devices that rotate the left and right wheels by being connected to the output shaft of the transmission via a probra shaft.

  In this type of wheel loader, a differential mechanism that distributes the driving force from the engine to the left and right wheels is equipped with a differential limiting mechanism that limits the differential according to the magnitude of the driving torque. It has been. This differential limiting mechanism is configured such that the differential is limited as the drive torque increases, and the differential limit is released as the drive torque decreases. The limiting torque is uniquely determined.

  However, with a wheel loader, the road surface condition and the driving condition vary greatly depending on the work site and work contents, so when the vehicle is in a state where it is likely to slip, the differential limit torque set assuming normal driving is not sufficient. A slip will occur. Therefore, in a construction vehicle such as a wheel loader, it is desirable that the differential control torque can be appropriately adjusted according to the road surface state and the driving state. As such a differential limiting device, Patent Document 1 discloses a drive from an engine. A differential mechanism that distributes force to the left and right drive wheels, a differential limiting mechanism that limits the differential of the differential mechanism, and a controller that controls the differential limiting mechanism, and the hydraulic pressure detected by the controller with a pressure sensor , Which is configured to control the differential limiting mechanism is disclosed.

Japanese Patent No. 5256067

  In the differential limiting device disclosed in Patent Document 1, it is possible to perform automatic differential limiting (diff lock) control in order to prevent slipping in a state where the wheel loader is performing excavation work. There is no slip prevention function during traveling other than excavation, and slipping occurs when traveling on soft ground with a small road surface friction coefficient.

  For example, even when the wheel loader is excavated, if the rear axle is lifted and one wheel (tire) of the front axle is slipped, the engine output is applied to the other wheel. Slips in an overload condition that is equal to or greater than (heavy x friction coefficient). The slip at this time is a slip under a state of high frictional force, and the wear of the tire is much greater than that of a normal slip, and the life of the tire is shortened. Further, in such a slip state, an overload state in which the entire output of the engine is applied to the front wheel single wheel may result in damage to the axle shaft (axle). In addition, if the strength of the axle is increased to prevent such a situation, the axle becomes larger than necessary, which is not economical.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wheel loader differential control device having an automatic differential lock control function for preventing slipping in both running and excavation work. There is.

  In order to achieve the above-described object, a representative present invention provides a wheel loader differential equipped with a differential limiting mechanism for controlling a differential device of a traveling axle on one or both of a front shaft and a rear shaft. In the control device, a proportional hydraulic device that adjusts a differential limiting amount of the differential limiting mechanism, a torque measuring device that measures torque acting on two axle shafts extending from the differential device of each wheel, A controller for controlling the differential limiting mechanism based on a detection value of the torque measuring device, and the controller is configured to generate a torque on a wheel side having a smaller torque among left and right wheels detected by the torque measuring device. When the state is less than the first threshold in the state, the differential limiting amount is maintained at a constant value, and the torque on the wheel side having the smaller torque among the left and right wheels detected by the torque measuring device is the first torque in the traveling state. When the value is less than the second threshold and less than the second threshold value, the differential limiting amount is continuously reduced according to the increase in torque, and the torque on the wheel side with the smaller torque among the left and right wheels detected by the torque measuring device is The left and right wheels are respectively controlled so that the differential limiting amount is maintained at 0 when the traveling state is equal to or more than the second threshold value and less than the third threshold value.

  The differential limiting device for a wheel loader according to the present invention can have an automatic differential lock control function for preventing slipping in both the traveling and excavation work of the wheel loader. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

The side view of the wheel loader concerning the embodiment of the present invention. The perspective view of the front side axle apparatus with which the wheel loader of FIG. 1 is equipped. Sectional drawing which shows the internal structure of an axle apparatus. The block diagram of the axle control apparatus (CNT) provided in the axle apparatus. The block diagram of the axle control program performed by an axle control apparatus. Explanatory drawing which shows the relationship between the torque value which acts on an axle shaft, and a differential limiting amount. The flowchart which shows the operation | movement procedure of an axle control apparatus.

  Hereinafter, a wheel loader differential control device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the wheel loader 1 according to the embodiment includes a rear vehicle body 2, a front vehicle body 3 connected to the front side of the rear vehicle body 2 so as to be swingable in the left-right direction, A rear wheel 4 (shown on the right side only) provided on both sides, a front wheel 5 (shown only on the right side) provided on both sides in the left-right direction of the front vehicle body 3, and a front side of the front vehicle body 3 are attached so as to be able to move up and down. The working device 6 and axle devices 11 and 12, which will be described later.

  The rear vehicle body 2 is equipped with an engine 7, a torque converter 8, a transmission 9, a hydraulic pump (not shown), and the like as drive sources. The transmission 9 is connected to the rear axle device 11 via one propeller shaft 9a extending in the front-rear direction, and is connected to the front axle device 12 via the other propeller shaft 9b. Further, on the upper side of the rear body 2, a cab 10 on which an operator gets on is provided.

  The rear axle device 11 provided at the lower side of the rear vehicle body 2 is formed to extend in the left-right direction, and the rear wheels 4 (tires) are respectively attached to the left and right ends thereof. On the other hand, the front axle device 12 provided on the lower side of the front vehicle body 3 is formed to extend in the left-right direction, and front wheels 5 (tires) are respectively attached to the left and right ends thereof. Here, since the rear axle device 11 and the front axle device 12 are configured substantially the same, only the configuration of the front axle device 12 will be described in detail below, and the description of the configuration of the rear axle device 11 will be omitted. .

  The front axle device 12 is connected to the propeller shaft 9b (see FIG. 1) to rotationally drive the left and right front wheels 5, and as shown in FIGS. 2 and 3, the front axle device 12 includes a casing 13 The input shaft 18, the pinion gear 20, the rotary shafts 25a and 25b, the differential mechanism 21, the brake mechanism 27, the axle shafts 31a and 31b, and the like.

  The casing 13 forms the outer shape of the front axle device 12, and the casing 13 is a cylinder extending in the left-right direction along an axis that serves as a rotation axis (rotation center line) of the rotation shafts 25a and 25b and the axle shafts 31a and 31b. It is formed as a body. The casing 13 is disposed in an intermediate portion in the left-right direction, and includes a differential case 14 (hereinafter referred to as a differential case 14) and left and right axle tubes 17.

  The differential case 14 is constituted by a main body case 15 and a lid 16, and a differential mechanism 21 and the like are accommodated in the differential case 14. The main body case 15 constitutes a main body portion of the differential case 14 and is formed as a substantially cylindrical hollow body. The lid body 16 closes the upper side of the main body case 15 and is formed as a substantially rectangular plate. The periphery of the lid body 16 is attached to the upper surface of the main body case 15 and is bolted so as to be removable.

  The axle tube 17 extends from the differential case 14 toward the outer side in the left-right direction, and is formed so as to be gradually narrowed from the base end side on the differential case 14 side toward the front end side on the front wheel 5 side. The left and right axle tubes 17 are provided with axle shafts 31a, 31b and the like, and are formed as cylindrical bodies extending in the left-right direction. The base end side of each axle tube 17 is bolted to a main body case 15 constituting the differential case 14, and the inside of the base end side of the axle tube 17 is a reduction gear mechanism chamber that houses a planetary gear reduction mechanism 33 described later. It has become.

  The input shaft 18 is rotatably provided in the main body case 15 via a bearing 19, and the input shaft 18 is connected to the propeller shaft 9b at a flange portion protruding outward. The tip of the input shaft 18 disposed in the gear chamber 15 a of the main body case 15 is a pinion gear 20, and the pinion gear 20 is rotatably attached to the main body case 15 via the input shaft 18. Here, the pinion gear 20 (input shaft 18) is disposed so as to extend rearward in the front-rear direction from the rotation center of a ring gear 26 described later.

  The differential mechanism 21 housed in the differential case 14 (main body case 15) distributes the rotational force of the output shaft of the transmission 9 transmitted through the input shaft 18 and the pinion gear 20 to the left and right front wheels 5. That is, the differential mechanism 21 meshes with each pinion gear 23 and a gear case 22 rotatably supported by the main body case 15, a plurality of pinion gears 23 rotatably provided on a spider 22 a fixed in the gear case 22. The two side gears 24, the base end side (one end side) are splined with the side gear 24, and the tip end side (the other end side) are two rotating shafts 25a, 25b extending in the left-right direction toward the axle shafts 31a, 31b. It consists of and. Further, a mounting flange 22b is provided on the outer peripheral side of the gear case 22 with an enlarged diameter, and a ring gear 26 is mounted on the mounting flange 22b.

  The rotary shafts 25a and 25b extend in the differential case 14 from the side gear 24 to the axle tube 17, and a sun gear 34 to be described later is provided on the tip side of the rotary shafts 25a and 25b. The rotary shafts 25a and 25b are connected to the engine 7 serving as a drive source, and transmit the rotational force of the engine 7 to the axle shafts 31a and 31b by rotating the above-described axis as the rotation axis (rotation center axis). .

  The ring gear 26 is a bevel gear constituting a part of the differential mechanism 21, and the ring gear 26 is connected to the transmission 9 by meshing with the pinion gear 20. The ring gear 26 is disposed on the left side of the main body case 15 and is bolted to the mounting flange 22 b of the gear case 22.

  The differential mechanism 21 configured as described above is arranged in the left-right direction via the pinion gears 23 and the side gears 24 when the rotational force of the transmission 9 is transmitted to the gear case 22 via the input shaft 18 (pinion gear 20) and the ring gear 26. The left and right front wheels 5 are driven by being distributed to the rotary shafts 25a and 25b.

  The brake mechanisms 27 are provided in the left and right brake chambers 15b of the main body case 15, respectively. Each of these brake mechanisms 27 is configured as a wet multi-plate brake mechanism, for example. The brake mechanism 27 is spline-coupled to the outer peripheral sides of the rotary shafts 25a and 25b, and a plurality of brake discs 28 made of an annular plate centering on the axis, and the brake mechanism 27 located on the outer peripheral side of the brake discs 28 The brake plate 29 includes a brake plate 29 that faces the brake disk 28 and is non-rotatably attached to the main body case 15, and a piston 30 that presses the brake plate 29 against the brake disk 28 by external hydraulic pressure.

  Each brake mechanism 27 configured as described above is such that an operator steps on a brake pedal (not shown) in the cab 10 to move the piston 30 by hydraulic pressure and press the brake plate 29 against the brake disk 28. The front wheel 5 can be braked by generating a braking force with a frictional force.

  The axle shafts 31 a and 31 b extend in the left-right direction in the left and right axle tubes 17, and are rotatably supported by the corresponding axle tubes 17 via hub bearings 32. A carrier 38 is splined to the base end side of each axle shaft 31a, 31b. On the other hand, the front end side of each axle shaft 31a, 31b protrudes from the axle tube 17, and a front wheel 5 is attached to the end thereof. . Thereby, the axle shafts 31a and 31b can transmit the rotation decelerated by the planetary gear reduction mechanism 33 described later to the front wheels 5.

  The planetary gear reduction mechanism 33 decelerates the rotation of the rotary shafts 25a and 25b and transmits it to the axle shafts 31a and 31b. As described above, the planetary gear reduction mechanism 33 is provided in the reduction gear mechanism chamber of the axle tube 17. It has been. The planetary gear reduction mechanism 33 includes a sun gear (sun gear) 34, an internal gear (ring gear) 35, a planetary gear (planet gear) 36, a carrier (planetary carrier) 38, and a retainer plate 39. ing.

  The sun gear 34 is provided on the front end side of the rotary shafts 25a and 25b and rotates integrally with the rotary shafts 25a and 25b. The sun gear 34 is located in the sun gear insertion hole of the carrier 38, and the sun gear 34 meshes with the planetary gear 36. The internal gear 35 is provided on the inner peripheral surface of the axle tube 17, and the planetary gear 36 meshes with the internal gear 35. The internal gear 35 is attached with an annular ring member having a gear (internal teeth) formed on the inner peripheral side thereof around the entire circumference in a state of being prevented from rotating by a key connection or the like on the proximal end side of the axle tube 17. It is comprised by.

  A plurality of (for example, three) planetary gears 36 (only one is shown) mesh with the internal gear 35 and the sun gear 34, and each planetary gear 36 is circumferentially connected between the internal gear 35 and the sun gear 34. Are provided at predetermined intervals. Each planetary gear 36 is configured as a cylindrical member in which gears (external teeth) are formed on the outer peripheral side over the entire circumference, and is rotatably supported by the carrier 38.

  The carrier 38 supports the planetary gear 36, and axle shafts 31a and 31b are splined to the inner peripheral side. The carrier 38 includes a cylindrical support portion having a diameter smaller than the diameter of the tip of the internal gear 35 and a cylindrical portion protruding from the support portion toward the outer side in the left-right direction (the vehicle body outer side, the front wheel 5 side). ing.

  The retainer plate 39 is positioned between the rotary shafts 25a and 25b and the axle shafts 31a and 31b. The retainer plate 39 is formed in a substantially disc shape and is seated on the step portion on the inner peripheral side of the carrier 38. It has become.

  The front axle device 12 is provided with a differential limiting mechanism 40, and the detailed configuration is omitted in the drawing, but this differential limiting mechanism 40 is composed of a multi-plate clutch, a pressure ring, a reaction plate, a piston, an oil chamber. , An oil passage 42, a hydraulic device 44, and the like. The multi-plate clutch has a first friction plate fixed in the rotation direction of the side gear 24 and a second friction plate fixed in the rotation direction with respect to the gear case 22. Pressure rings and reaction plates are arranged on both sides in the direction. When hydraulic pressure is supplied from the hydraulic device 44 to the oil chamber via the oil passage 42, the piston moves so as to push the reaction plate, and the multi-plate clutch is fastened. The hydraulic device 44 changes the pressure of the pressure oil supplied to the piston of the differential limiting mechanism 40 according to the control of an axle control device (controller) 50 described later, and sets the differential limiting amount by a multi-plate clutch that operates accordingly. To do.

  That is, when the pressure of the pressure oil supplied from the hydraulic device 44 to the differential limiting mechanism 40 increases in accordance with the control of the axle control program 60 executed on the axle control device 50, the first and second of the multi-plate clutch. Since the frictional force between the friction plates increases, the amount of torque distributed to the axle shaft 31b via one of the rotating shafts, for example, the rotating shaft 25b, increases and is distributed to the axle shaft 31a via the rotating shaft 25a. Torque amount decreases.

  On the other hand, when the pressure of the pressure oil supplied from the hydraulic device 44 to the differential limiting mechanism 40 decreases, the frictional force between the first and second friction plates of the multi-plate clutch decreases. When the difference in torque distributed to the left and right rotating shafts is small and the pressure oil pressure is zero, the torque distributed to the axle shaft 31b side via the rotating shaft 25b and the axle shaft via the rotating shaft 25a The torque distributed to the 31a side becomes equal. Thus, the differential control of the front axle device 12 is executed by the cooperative operation of the axle control device 50, the axle control program 60, the differential limiting mechanism 40, the oil passage 42, the hydraulic device 44, and the like.

  Both end portions in the longitudinal direction of the axle shafts 31a and 31b are rotatably supported by the axle tube 17 via a pair of hub bearings 32. Among these hub bearings 32, an outer bearing of the outer hub bearing 32 has a sensor 120a. 120b and sensors 122a and 122b are attached to the inner bearings of the inner hub bearing 32. These sensors 120a, 120b, 122a, 122b constitute a torque measuring device, and this torque measuring device has one axle based on the phase difference between the signals output from the outer and inner sensors 120a, 122a. The torque on the shaft 31a side is calculated, and the calculated torque is output to the axle control device 50. Similarly, the torque measurement device calculates the torque on the other axle shaft 31b side based on the phase difference between the signals output from the outer side and inner side sensors 120b and 122b, and sends the calculated torque to the axle control device 50. Output.

  Next, the configuration of the aforementioned axle control device (CNT) 50 will be described with reference to FIG. As shown in FIG. 4, when the front axle device 12 is controlled by software, the axle control device 50 includes a main body 500, an input / output device 506, a recording device 514, a sensor interface (IF) 510, and a hydraulic device IF 512. Is done.

  The main body 500 includes a CPU 502, a memory 504 such as a RAM, and peripheral circuits thereof. The input / output device 506 is a liquid crystal display device with a touch panel provided in the cab 10. The recording device 514 includes a DVD device, an HDD, a nonvolatile memory, and the like.

  That is, the axle control device 50 includes components as a normal computer and components for controlling the hydraulic device 44. The sensor IF 510 is connected to each sensor 120a, 120b, 122a, 122b for torque measurement, and receives the value of torque measured by these sensors. The hydraulic device IF 512 controls the hydraulic device 44 according to the operation of the axle control program 60 and adjusts the pressure oil supply pressure supplied to the differential limiting mechanism 40.

  FIG. 5 is a configuration diagram of an axle control program 60 executed by the axle control device 50. As shown in FIG. 5, the axle control program 60 includes an operation control unit 600, a sensor control unit 602, a measured value reading unit 604, A table storage unit 606, a data comparison unit 608, a control amount determination unit 610, and a hydraulic device control unit 612 are configured. The operation control unit 600 is loaded into the memory 504 of the axle control device 50 via, for example, the recording medium 516 or a network (not shown), and is executed under the control of the CPU 502.

  In the axle control program 60, the operation control unit 600 controls the operation of the axle control program 60, for example, initialization, activation, and exception handling of each component of the axle control program 60 (error display to the input / output device 506, etc.) )I do. The sensor control unit 602 outputs an operation signal to each of the sensors 120a, 120b, 122a, and 122b for torque measurement, and outputs the signals output from the pair of outer side sensors 120a and 120b and the inner side sensors 122a and 120b. Based on the phase difference, torque values applied to the left and right axle shafts 31a and 31b are calculated. The measurement value reading unit 604 reads the torque value measured by each sensor 120 a, 120 b, 122 a, 122 b under the control of the sensor control unit 602, and outputs this to the data comparison unit 608.

  FIG. 6 is an explanatory diagram showing the relationship between the torque value stored in the table storage unit 606 and the differential limiting amount (lock rate) of the differential limiting mechanism 40. As shown in FIG. The larger (solid line) and the smaller (broken line) of the average torque values applied to the axle shafts 31a and 31b measured by the torque measuring device, and the differential limiting amount of the differential limiting mechanism 40 Data indicating the relationship is stored in a table format. As shown in FIG. 6, the relationship between the magnitudes of the first threshold value to the fifth threshold value of the torque is as follows: first threshold value <second threshold value <third threshold value <fourth threshold value <fifth threshold value.

  Here, the region A less than the first threshold is a region where the wheel having the smaller torque value is more likely to slip in the running state. The torque required to drive the vehicle body is determined by the vehicle body mass, the load mass, and the efficiency of the drive line from the engine to the axle, and is affected by the accuracy of the parts and the oil viscosity (oil temperature). The first threshold value is a lower limit value of torque required when the vehicle body is driven at the lowest load. A region B from the first threshold value to the third threshold value corresponds to a normal traveling state of the wheel loader 1, and a region C that is greater than or equal to the first threshold value and less than the second threshold value is that the wheel having the smaller torque value is in the traveling state. This is an area where there is a low possibility of slipping, and the second threshold value is an upper limit value of torque necessary for running the vehicle body with the lowest load. Region D that is greater than or equal to the second threshold value and less than the third threshold value is a region in which the wheel with the smaller torque value is unlikely to slip in the running state. The third threshold is an upper limit value of torque generated when the vehicle body is driven with the highest load.

  An area E between the third threshold value and the fifth threshold value corresponds to the excavation state of the wheel loader 1, and an area F that is greater than or equal to the third threshold value and less than the fourth threshold value is excavated by the wheel having the larger torque value. The fourth threshold value is a lower limit value of the torque generated when excavating at the highest load. A region G that is greater than or equal to the fourth threshold value and less than the fifth threshold value is a region in which the wheel with the larger torque value may be overloaded when excavated, and the fifth threshold value occurs when excavating at the highest load. This is the upper limit value of torque. Further, the region H equal to or greater than the fifth threshold is a region in which the wheel having the larger torque value is damaged by exceeding the maximum load in the excavation state.

  Hereinafter, the “average value of torque applied to the axle shaft 31a” is referred to as “torque value of the axle shaft 31a”, and the average value of torque applied to the axle shaft 31b is referred to as “torque value of the axle shaft 31b”. That is, as shown in FIG. 6, the table storage unit 606 is provided in the front axle device 12 when the smaller torque value of the axle shafts 31 a and 31 b is less than the first threshold value. Data for setting the differential limiting amount of the differential limiting mechanism 40 to be kept at a constant value (for example, the first stage) is stored. Note that the smaller torque value of the axle shafts 31a and 31b being less than the first threshold means that the wheel loader 1 is in the state of the region A shown in FIG.

  Further, the table storage unit 606 continuously sets the differential limiting amount according to the torque increase when the smaller torque value of the axle shafts 31a and 31b is not less than the first threshold value and less than the second threshold value. Therefore, the data for setting the differential limit amount to be continuously increased from 0 to the first stage according to the torque reduction is stored. Note that the smaller torque value of the axle shafts 31a and 31b being greater than or equal to the first threshold and less than the second threshold means that the wheel loader 1 is in the state of the region C in the region B shown in FIG. .

  Further, the table storage unit 606 sets the differential limiting amount of the differential limiting mechanism 40 when the smaller torque value among the torque values of the axle shafts 31a and 31b is greater than or equal to the second threshold value and less than the third threshold value. Data for setting to 0 is stored. Note that the smaller value of the torque values of the axle shafts 31a and 31b being greater than or equal to the second threshold value and less than the third threshold value means that the wheel loader 1 is in the state of the region D in the region B shown in FIG. To do.

  On the other hand, as shown in FIG. 6, the table storage unit 606 responds to the torque increase when the larger torque value of the axle shafts 31a and 31b is greater than or equal to the third threshold value and less than the fourth threshold value. The differential limit amount is continuously increased from 0 to the maximum, and data for setting the differential limit amount to continuously decrease from the maximum to 0 as the torque decreases is stored. Note that the larger torque value of the axle shafts 31a and 31b being not less than the third threshold value and less than the fourth threshold value means that the wheel loader 1 is in the state of the region F in the region E shown in FIG.

  Further, the table storage unit 606 maximizes the differential limiting amount according to the torque increase when the larger torque value of the axle shafts 31a and 31b is not less than the fourth threshold value and less than the fifth threshold value. Data for setting to continuously decrease from 0 to 0 and to continuously increase the differential limiting amount from 0 to the maximum in accordance with torque reduction is stored. Note that the larger torque value of the axle shafts 31a and 31b being greater than or equal to the fourth threshold value and less than the fifth threshold value means that the wheel loader 1 is in the state of the region G in the region E shown in FIG.

  Further, the table storage unit 606 sets the differential limiting amount of the differential limiting mechanism 40 to 0 when the larger torque value among the torque values of the axle shafts 31a and 31b is greater than or equal to the fifth threshold value. Stores data for setting. Note that the larger torque value of the axle shafts 31a and 31b being equal to or greater than the fifth threshold means that the wheel loader 1 is in the region H shown in FIG. The table storage unit 606 outputs the data stored as described above to the data comparison unit 608 and the control amount determination unit 610 for processing in the data comparison unit 608.

  The data comparison unit 608 compares the data stored in the table storage unit 606 with the larger or smaller torque value of the axle shafts 31a and 31b. Further, the data comparison unit 608 determines whether the torque applied to the axle shafts 31a, 31b of the wheel loader 1 is in any of the regions A to H shown in FIG. 6, and the torque value used for the determination. Is output to the control amount determination unit 610.

  The control amount determination unit 610 is provided with the differential provided in the axle device 12 according to the determination results of the areas A to H received from the data comparison unit 608 and the torque value used for the determination in the data comparison unit 608. The differential limiting amount (lock rate) of the limiting mechanism 40 is determined, and a control signal is output to the hydraulic control unit 612 so as to set the determined differential limiting amount. The hydraulic device control unit 612 controls the hydraulic device 44 based on an instruction from the control amount determination unit 610 and, as shown in FIG. 6, the difference between the differential limiting mechanism 40 according to the torque amount of the axle shafts 31a and 31b. Variable adjustment of dynamic control amount.

  Next, the differential control processing of the axle device 12 will be described with reference to FIG. FIG. 7 is a flowchart showing the differential control operation (S10) of the differential limiting mechanism 40 provided in the front axle device 12. As shown in FIG. 7, in step 100 (S100), the operation of the axle control program 60 is performed. The control unit 600 initializes and starts each component of the axle control program 60 at regular intervals (for example, every 10 ms) to control these operations.

  In step 102 (S102), the sensor control unit 602 outputs an operation signal to each of the sensors 120a, 120b, 122a, 122b for torque measurement, and forms a pair of outer side sensors 120a, 120b and inner side sensors 122a, Based on the phase difference of the signal output from 120b, the torque value applied to the left and right axle shafts 31a, 31b is calculated. In step 104 (S104), the measured value reading unit 604 reads the torque value applied to the axle shafts 31a and 31b measured by the sensors 120a, 120b, 122a, and 122b, and outputs this to the data comparing unit 608. .

  In step 106 (S106), the data comparison unit 608 compares the data included in the table stored in the table storage unit 606 with the larger or smaller of the torque values of the axle shafts 31a and 31b. Further, the data comparison unit 608 determines whether the torque applied to the axle shafts 31a and 31b of the wheel loader 1 is in any of the regions A to H shown in FIG. The limit amount is output to the control amount determination unit 610. Specifically, the determination as to which state of the regions A to H shown in FIG. 6 the torque applied to the axle shafts 31a and 31b of the wheel loader 1 is in the following S108, S110, S112, S116, and S120. Realized by processing. Further, the determination of the differential limiting amount to be set is realized by the processes of S114, S118, S122, and S124.

  That is, in step 108 (S108), the data comparison unit 608 determines whether or not the larger torque value among the torque values of the axle shafts 31a and 31b is greater than or equal to the fifth threshold value. The axle control program 60 proceeds to the process of S118 when the larger torque value of the axle shafts 31a and 31b is not less than the fifth threshold value (YES) and the wheel loader 1 is in the region H, and otherwise (NO). Proceeds to S110.

  In step 110 (S110), the data comparison unit 608 determines whether or not the larger torque value among the torque values of the axle shafts 31a and 31b is greater than or equal to the fourth threshold value. The axle control program 60 proceeds to the processing of S114 when the larger torque value of the axle shafts 31a and 31b is not less than the fourth threshold (YES) and the wheel loader 1 is in the region G, and otherwise (NO). Proceeds to S112.

  In step 112 (S112), the data comparison unit 608 determines whether or not the larger torque value among the torque values of the axle shafts 31a and 31b is greater than or equal to the third threshold value. The axle control program 60 proceeds to the processing of S114 when the larger torque value of the axle shafts 31a and 31b is equal to or greater than the third threshold value (YES) and the wheel loader 1 is in the region F, and otherwise (NO). Proceeds to S116.

  In step 114 (S114), when the control amount determination unit 610 determines that the wheel loader 1 is in the region F shown in FIG. 6, the differential amount of the differential limiting mechanism 40 is changed from 0 according to the increase or decrease of the torque. A control signal is output to the hydraulic device control unit 612 so as to increase or decrease between the maximum second stages (for example, lock rate 2). On the other hand, when the control amount determination unit 610 determines that the wheel loader 1 is in the region G shown in FIG. 6, the control amount determination unit 610 increases or decreases the differential limit amount between the second stage and 0 according to the increase or decrease of the torque. A control signal is output to the hydraulic device control unit 612. The hydraulic device control unit 612 controls the hydraulic device 44 based on a command from the control amount determination unit 610, and sets the differential control amount as shown in FIG. Further, when the torque value of each axle shaft 31a, 31b having the larger torque value is the fourth threshold value, the control amount determination unit 610 sets the differential control amount to the maximum second stage (lock rate). 2).

  In step 116 (S116), the data comparison unit 608 determines whether or not the smaller value of the torque values of the axle shafts 31a and 31b is greater than or equal to the second threshold value. The axle control program 60 proceeds to the processing of S118 when the smaller torque value of the axle shafts 31a and 31b is equal to or greater than the second threshold value (YES) and the wheel loader 1 is in the region D, and otherwise (NO). Proceeds to S120.

  In Step 118 (S118), when the control amount determination unit 610 determines that the wheel loader 1 is in the regions D and H shown in FIG. 6, the control amount determination unit 610 instructs the hydraulic device control unit 612 to set the differential limit amount to zero. Output a control signal. The hydraulic device control unit 612 controls the hydraulic device 44 based on a command from the control amount determination unit 610, and sets the differential control amount as shown in FIG.

  In step 120 (S120), the data comparison unit 608 determines whether the smaller torque value of the torque values of the axle shafts 31a and 31b is greater than or equal to the first threshold value. The axle control program 60 proceeds to the processing of S124 when the smaller torque value of the axle shafts 31a and 31b is equal to or greater than the first threshold (YES) and the wheel loader 1 is in the region C, and otherwise (NO). Advances to the process of S122.

  In step 122 (S122), when the control amount determination unit 610 determines that the wheel loader 1 is in the region C shown in FIG. 6, the control amount determination unit 610 determines the differential limit amount in the first stage (for example, lock rate 1). ) To 0 to output a control signal to the hydraulic control unit 612. The hydraulic device control unit 612 controls the hydraulic device 44 based on a command from the control amount determination unit 610, and sets the differential control amount as shown in FIG.

  In step 124 (S124), when the control amount determination unit 610 determines that the wheel loader 1 is in the region A shown in FIG. 6, the hydraulic pressure is controlled so that the differential limit amount is set to the first stage (lock ratio 1). A control signal is output to the device controller 612. The hydraulic device control unit 612 controls the hydraulic device 44 based on a command from the control amount determination unit 610, and sets the differential control amount as shown in FIG.

  In step 126 (S126), the operation control unit 600 performs exception processing (for example, a warning display to the input / output device 506 and an input request) when a failure occurs in a component part of the axle control program 60 or the wheel loader 1. Display) is determined. The axle control program 60 returns to S100 when exception processing is not required (NO), and proceeds to S128 when exception processing is required (YES), and is determined in advance according to the type of failure. Exception processing is performed and the processing ends.

  As described above, in the differential limiting device of the wheel loader 1 according to the present embodiment, the torque values of the left and right axle shafts 31a and 31b provided in the axle device 12 are measured by the torque measuring device, and the detected value and the wheel are measured. Since the axle control device (controller) 50 variably controls the differential limiting amount (lock rate) of the differential limiting mechanism 40 according to the operating state of the loader 1, as shown in regions A and B of FIG. In addition, even when the wheel loader 1 is in a traveling state, it has a slip prevention function and can prevent slipping when traveling on soft ground or the like having a small road surface friction coefficient.

  Further, even when the rear wheel 4 is lifted and one wheel of the front wheel 5 is in a slip state in the excavation state of the wheel loader 1, as shown by regions G and H in FIG. Since the differential limiting amount of the dynamic limiting mechanism 40 is continuously reduced from the maximum to zero, it does not become an overload state in which the entire output of the engine 7 is applied to one wheel, and the axle shafts 31a and 31b are prevented from being damaged. can do.

  In the above-described embodiment, the case where the present invention is realized by software executed in the axle control device 50 is illustrated. However, the functions of the axle control program 60 may be performed using dedicated hardware or dedicated hardware. You may make it implement | achieve together using software.

  In the above embodiment, the case where the axle controller 50 linearly and variably controls the differential limiting amount of the differential limiting mechanism 40 between the first threshold value to the fifth threshold value illustrated in FIG. The differential limit amount shown in FIG. 6 may be changed in a curve according to the running path state of the wheel loader 1, the excavation site, and the like, and the values of the first threshold value to the fifth threshold value are arbitrarily set. Is possible.

  Further, in the above embodiment, the torque configured to measure the torque values of the axle shafts 31a and 31b based on the phase difference between the sensors 120a, 120b, 122a, and 122b attached to the inner bearing and the outer bearing of the hub bearing 32. Although the measurement device is illustrated, the configuration of the torque measurement device is not limited to this, and a torque measurement device including a magnetostrictive torque sensor, a contact torque sensor, or the like can be used.

  Moreover, embodiment mentioned above is an illustration for description of this invention, and is not the meaning which limits the scope of the present invention only to those embodiment. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Wheel loader 2 Rear vehicle body 3 Front vehicle body 4 Rear wheel 5 Front wheel 6 Working device 7 Engine 8 Torque converter 9 Transmission 9a, 9b Propeller shaft 11, 12 Axle device 17 Axle tube 18 Input shaft 21 Differential mechanism 25a, 25b Rotating shaft 27 Brake mechanism 31a, 31b Axle shaft 32 Hub bearing 33 Planetary gear reduction mechanism 40 Differential limiting mechanism 42 Oil passage 44 Hydraulic device 50 Axle control device (controller)
60 Axle control program 120a, 120b, 122a, 122b Sensor (torque measuring device)

Claims (3)

In the differential limiting device of the wheel loader provided with a differential limiting mechanism for controlling the differential device of the traveling axle on either or both of the front shaft and the rear shaft,
A proportional hydraulic device that adjusts a differential limiting amount of the differential limiting mechanism, a torque measuring device that measures torque acting on two axle shafts extending from the differential device of each wheel, and a torque measuring device A controller that controls the differential limiting mechanism based on a detection value;
The controller is
When the torque on the wheel side having a small torque among the left and right wheels detected by the torque measuring device is less than the first threshold in the running state, the differential limiting amount is kept at a constant value,
When the torque on the wheel side having the smaller torque among the left and right wheels detected by the torque measuring device is not less than the first threshold value and less than the second threshold value in the running state, the differential limit amount is increased according to the torque increase. Lower continuously,
In order to keep the differential limiting amount at 0 when the torque on the wheel side having a small torque among the left and right wheels detected by the torque measuring device is not less than the second threshold and less than the third threshold in the running state,
A differential limiting device for a wheel loader, wherein the left and right wheels are respectively controlled. The differential limiting device for a wheel loader according to claim 1,
The controller is
When the torque on the wheel side having the larger torque among the left and right wheels detected by the torque measuring device is not less than the third threshold value and less than the fourth threshold value in the excavation state, the differential limiting amount is increased according to the torque increase. Raise continuously,
When the torque on the wheel side having the larger torque among the left and right wheels detected by the torque measuring device is not less than the fourth threshold value and less than the fifth threshold value in the excavation state, the differential limit amount is increased according to the torque increase. Lower continuously,
Of the left and right wheels detected by the torque measuring device, when the torque on the wheel side with the larger torque becomes the fifth threshold value in the excavation state, the differential limiting amount is set to 0 and the torque is the fifth threshold value. So as not to become larger
A differential limiting device for a wheel loader, wherein the left and right wheels are respectively controlled. In the wheel loader differential limiting device according to claim 1 or 2,
The torque measuring device is attached to a sensor attached to an inner bearing of one hub bearing and an outer bearing of the other hub bearing out of a pair of hub bearings supporting both longitudinal ends of the axle shaft. A differential limiting device for a wheel loader, characterized in that a torque acting on the axle shaft is calculated based on a phase difference between sensors.