JP6660904B2 - Wheel loader differential limiting device - Google Patents

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 has a front vehicle body connected to the front side of the rear vehicle body so as to swing in the left-right direction, and a working 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 the power of the engine is transmitted to the transmission via the torque converter. Further, an axle device that rotates the left and right wheels by being connected to the output shaft of the transmission via a prob shaft is provided on the front vehicle body and the rear vehicle body.

  In this type of wheel loader, there is known a differential mechanism for distributing a driving force from an engine to left and right wheels (wheels) and a differential limiting mechanism for limiting a differential according to the magnitude of a driving torque. Have been. This differential limiting mechanism is configured such that the differential is limited as the driving torque increases, and the differential restriction is released as the driving torque decreases, and the differential is limited according to the magnitude of the driving torque. The limiting torque is uniquely determined.

  However, with a wheel loader, the road surface conditions and driving conditions vary greatly depending on the work site and work content, so when the vehicle is in a state that is likely to slip, the differential limiting torque set for normal driving is not enough. , Causing a slip. 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 condition and the driving condition. A differential mechanism for distributing the force to the left and right drive wheels, a differential limiting mechanism for limiting the differential of the differential mechanism, and a controller for controlling the differential limiting mechanism. , A device configured to control the differential limiting mechanism is disclosed.

Japanese Patent No. 5256067

  In the differential limiting device disclosed in Patent Literature 1, it is possible to perform automatic differential limiting (diff lock) control in order to prevent slippage when the wheel loader is performing excavation work. There is no slip prevention function during traveling other than the excavation state, and the vehicle slips when traveling on a soft ground having a low coefficient of road surface friction.

  Further, for example, even in the excavation state of the wheel loader, if one wheel (tire) of the front shaft is slipped due to the rear shaft floating, the entire output of the engine is applied to the other wheel, so that the frictional force of the tire (shaft) is increased. (Stress x friction coefficient) or more. The slip at this time is a slip under a state of high frictional force, and the wear of the tire becomes much larger than the normal slip, and the life of the tire is shortened. Furthermore, in such a slip state, an overload state occurs in which the entire output of the engine is applied to one wheel of the front axle, so that the axle shaft (axle) may be damaged. If the strength of the axle is increased to prevent such a situation, the axle becomes unnecessarily large, which is not economical.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a differential control device for a wheel loader having an automatic differential lock control function for preventing slippage in both running and excavating work. It is in.

  In order to achieve the above object, a typical present invention relates to a differential of a wheel loader having 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 the detected value of the torque measuring device, wherein the controller detects that the torque of the wheel with the smaller torque among the left and right wheels detected by the torque measuring device is running. When the difference 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 with the smaller torque among the left and right wheels detected by the torque measuring device is the first torque in the running state. When the value is not less than the value and less than the second threshold, the differential limiting amount is continuously reduced according to the increase in the torque, and the torque of the wheel having a smaller torque among the left and right wheels detected by the torque measuring device is In the running state, the left and right wheels are controlled such that the differential limiting amount is kept at 0 when the difference is equal to or more than the second threshold and less than the third threshold.

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

FIG. 2 is a side view of the wheel loader according to the embodiment of the present invention. FIG. 2 is a perspective view of a front axle device provided in the wheel loader of FIG. 1. Sectional drawing which shows the internal structure of an axle apparatus. FIG. 2 is a configuration diagram of an axle control device (CNT) provided in the axle device. FIG. 2 is a block diagram of an axle control program executed by the axle control device. FIG. 4 is an explanatory diagram showing a relationship between a torque value acting on an axle shaft and a differential limiting amount. 5 is a flowchart illustrating an operation procedure of the axle control device.

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

  As shown in FIG. 1, a 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 and right direction, and a left and right direction of the rear vehicle body 2. Rear wheels 4 (only the right side is shown) provided on both sides, front wheels 5 (only the right side is shown) provided on both sides in the left-right direction of the front body 3, and are mounted on the front side of the front body 3 so as to be capable of elevating. Working device 6 and axle devices 11 and 12 to be described later.

  An engine 7, a torque converter 8, a transmission 9, a hydraulic pump (not shown), and the like, which are driving sources, are mounted on the rear body 2. 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. A cab 10 on which an operator rides is provided above the rear vehicle body 2.

  A rear axle device 11 provided below the rear vehicle body 2 is formed to extend in the left-right direction, and rear wheels 4 (tires) are respectively attached to left and right ends thereof. On the other hand, a front axle device 12 provided below the front vehicle body 3 is formed to extend in the left-right direction, and front wheels 5 (tires) are respectively attached to left and right ends thereof. Here, since the rear axle device 11 and the front axle device 12 have substantially the same configuration, 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. As shown in FIGS. 2 and 3, the front axle device 12 includes a casing 13 , An input shaft 18, a pinion gear 20, rotating shafts 25a and 25b, a differential mechanism 21, a brake mechanism 27, and axle shafts 31a and 31b.

  The casing 13 forms an outer shape of the front axle device 12, and the casing 13 extends in the left-right direction along an axis that is a rotation axis (rotation center line) of the rotation shafts 25 a and 25 b and the axle shafts 31 a and 31 b. It is formed as a shape. The casing 13 is disposed at 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 housed inside 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 16 closes the upper side of the main body case 15 and is formed as a substantially rectangular plate. The periphery of the lid 16 is attached to the upper surface of the main body case 15 and is detachably bolted.

  The axle tube 17 extends outward from the differential case 14 in the left-right direction, and is formed so as to be gradually tapered from a base end side, which is the differential case 14 side, to a front end side, which is the front wheel 5 side. The left and right axle tubes 17 have axle shafts 31a, 31b and the like disposed therein, and are formed as tubular bodies extending in the left-right direction. Each axle tube 17 has its proximal end bolted to a main body case 15 that constitutes the differential case 14. The proximal end of the axle tube 17 has a reduction gear mechanism chamber accommodating a planetary gear reduction mechanism 33 described later. Has become.

  The input shaft 18 is rotatably provided on the main body case 15 via a bearing 19, and the input shaft 18 has a flange portion protruding outside connected to the propeller shaft 9b. A distal end of an input shaft 18 disposed in the gear chamber 15a 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 (the input shaft 18) is arranged to extend rearward in the front-rear direction from a 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 via 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 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, and each pinion gear 23. Two side gears 24 and two rotating shafts 25a, 25b whose base end (one end) is spline-coupled to the side gear 24 and whose front end (the other end) extends in the left-right direction toward the axle shafts 31a, 31b. It is composed of 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 rotating shafts 25a and 25b extend from the side gear 24 to the inside of the axle tube 17 in the differential case 14, and a sun gear 34 to be described later is provided on the tip side of the rotating shafts 25a and 25b. The rotating shafts 25a and 25b are connected to the engine 7 serving as a driving source, and transmit the rotational force of the engine 7 to the axle shafts 31a and 31b by rotating with the above-mentioned axis as a rotating axis (rotating center axis). .

  The ring gear 26 is a bevel gear that forms 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 arranged on the left side of the main body case 15 and is bolted to a mounting flange 22 b of the gear case 22.

  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 differential mechanism 21 configured as described above is disposed in the left-right direction via the respective pinion gears 23 and the side gears 24. The left and right front wheels 5 are distributed to the rotation 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 the brake mechanisms 27 is configured as, for example, a wet-type multi-plate type brake mechanism. The brake mechanism 27 is spline-coupled to the outer peripheral sides of the rotating shafts 25a and 25b, and includes a plurality of brake disks 28 formed of an annular plate around the axis. It comprises a brake plate 29 facing the brake disk 28 and non-rotatably attached to the main body case 15, and a piston 30 for pressing the brake plate 29 against the brake disk 28 by external oil pressure.

  In each of the brake mechanisms 27 configured as described above, an operator steps on a brake pedal (not shown) in the cab 10, moves the piston 30 by hydraulic pressure, and presses the brake plate 29 against the brake disc 28. The brake can be applied to the front wheels 5 by generating a braking force by frictional force.

  The axle shafts 31a and 31b extend in the left and right axle tubes 17 in the left-right direction, and are rotatably supported by the corresponding axle tubes 17 via hub bearings 32. A carrier 38 is spline-coupled to the proximal end of each axle shaft 31a, 31b, while the distal end of each axle shaft 31a, 31b projects from the axle tube 17, and the front wheel 5 is attached to the end. . Thus, the axle shafts 31a and 31b can transmit the rotation reduced by the later-described planetary gear reduction mechanism 33 to the front wheels 5.

  The planetary gear reduction mechanism 33 reduces the rotation of the rotating shafts 25a and 25b and transmits the reduced rotation 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. Have been. The planetary gear reduction mechanism 33 includes a sun gear (sun gear) 34, an internal gear (ring gear) 35, a planet gear (planet gear) 36, a carrier (planetary carrier) 38, and a retainer plate 39. ing.

  The sun gear 34 is provided on the tip side of the rotating shafts 25a and 25b, and rotates integrally with the rotating 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. For the internal gear 35, an annular ring member having gears (internal teeth) formed on the entire inner circumference is attached to the base end of the axle tube 17 while being prevented from rotating by a key connection or the like. It consists of.

  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 of the planetary gears 36 has a circumferential direction between the internal gear 35 and the sun gear 34. Are provided at predetermined intervals. Each of the planetary gears 36 is configured as a cylindrical member having gears (external teeth) formed on the entire outer circumference, and is rotatably supported by the carrier 38.

  The carrier 38 supports the planetary gear 36, and axle shafts 31a and 31b are spline-coupled to the inner peripheral side. The carrier 38 is composed of a cylindrical support portion having a diameter smaller than the diameter of the addendum of the internal gear 35, and a cylindrical portion projecting outward from the support portion in the left-right direction (outside the vehicle body, toward the front wheel 5). ing.

  The retainer plate 39 is located between the rotating shafts 25a and 25b and the axle shafts 31a and 31b. The retainer plate 39 is formed in a substantially disk shape and is seated on a step 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, the detailed configuration of which is omitted from the drawing. The differential limiting mechanism 40 includes 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 press the reaction plate, and the multi-plate clutch is engaged. The hydraulic device 44 changes the pressure of the pressure oil supplied to the piston of the differential limiting mechanism 40 under 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. I do.

  That is, according to the control of the axle control program 60 executed on the axle control device 50, when the pressure of the pressure oil supplied from the hydraulic device 44 to the differential limiting mechanism 40 increases, the first and second multi-plate clutches are switched. 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 distributed to the axle shaft 31a via the rotating shaft 25a. The amount of torque to be reduced.

  Conversely, 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 between the torques distributed to the left and right rotating shafts becomes small and the pressure of the pressure oil is 0, the torque distributed to the axle shaft 31b via the rotating shaft 25b and the axle shaft via the rotating shaft 25a The torque distributed to the 31a side becomes equal. As described above, 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 operate in cooperation to perform the differential control of the front axle device 12.

  Both ends of the axle shafts 31a and 31b in the longitudinal direction are rotatably supported by the axle tube 17 via a pair of hub bearings 32. Of these hub bearings 32, the outer bearings of the outer hub bearing 32 are provided with sensors 120a. , 120b are attached, and sensors 122a, 122b are attached to the inner bearing of the inner hub bearing 32. These sensors 120a, 120b, 122a, and 122b constitute a torque measuring device, and this torque measuring device uses one axle based on a phase difference between signals output from the outer and inner sensors 120a and 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 measuring device calculates the torque on the other axle shaft 31b side based on the phase difference between the signals output from the outer and inner side sensors 120b and 122b, and sends the calculated torque to the axle control device 50. Output to

  Next, the configuration of the axle control device (CNT) 50 described above 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 or the like. 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 of the torque measurement sensors 120a, 120b, 122a, 122b, and receives the torque value measured by the sensors. The hydraulic device IF 512 controls the hydraulic device 44 in accordance with 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, It comprises a table storage unit 606, a data comparison unit 608, a control amount determination unit 610, and a hydraulic device control unit 612. The operation control unit 600 is loaded into the memory 504 of the axle control device 50 via the recording medium 516 or a network (not shown), for example, 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, initializes and activates each component of the axle control program 60, and performs exception processing (error display to the input / output device 506, etc.). )I do. The sensor control unit 602 outputs an operation signal to each of the torque measurement sensors 120a, 120b, 122a, and 122b, and outputs a signal output from the pair of outer-side sensors 120a and 120b and inner-side sensors 122a and 120b. Based on the phase difference, a torque value applied to the left and right axle shafts 31a, 31b is calculated. The measured value reading unit 604 reads the torque value measured by each of the sensors 120a, 120b, 122a, 122b under the control of the sensor control unit 602, and outputs this to the data comparing 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 ratio) of the differential limiting mechanism 40. As shown in FIG. Of the larger (solid line) and smaller (broken line) of the average of the 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 to fifth threshold values of torque is as follows: first threshold value <second threshold value <third threshold value <fourth threshold value <fifth threshold value.

  Here, the area A smaller than the first threshold value is an area in which a wheel having a smaller torque value is more likely to slip in a running state. The torque required for running 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 has a receiving width that is affected by component precision and oil viscosity (oil temperature). The first threshold value is a lower limit value of the torque required when running the vehicle body with the lowest load. An area B from the first threshold to the third threshold corresponds to a normal traveling state of the wheel loader 1, and an area C that is equal to or more than the first threshold and less than the second threshold is a state where the wheel having the smaller torque value is in the traveling state. The second threshold value is an upper limit value of the torque required for running the vehicle body with the lowest load. A region D that is equal to or larger than the second threshold and smaller than the third threshold is a region in which the wheel with the smaller torque value is unlikely to slip in the traveling state. The third threshold value is an upper limit value of a torque generated when the vehicle body runs at 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 equal to or more than the third threshold value and less than the fourth threshold value indicates that the wheel having the larger torque value is excavated. The fourth threshold is a lower limit of the torque generated when excavating with the highest load. An area G that is equal to or more than the fourth threshold and less than the fifth threshold is an area where the wheel with the larger torque value may be overloaded in the excavation state, and the fifth threshold is generated when excavating with the highest load. This is the upper limit of torque. Further, a region H equal to or larger than the fifth threshold value is a region in which the wheel having the larger torque value exceeds the maximum load and is damaged in the excavation state.

  Hereinafter, the “average value of the torque applied to the axle shaft 31a” is referred to as “the torque value of the axle shaft 31a”, and the average value of the torque applied to the axle shaft 31b is referred to as “the 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 one of the torque values of the axle shafts 31a and 31b is less than the first threshold value. Data for setting the differential limiting amount of the differential limiting mechanism 40 to a constant value (for example, the first stage) is stored. The smaller torque value of the axle shafts 31a, 31b is less than the first threshold value means that the wheel loader 1 is in the state of the area A shown in FIG.

  Further, when the smaller one of the torque values of the axle shafts 31a and 31b is equal to or greater than the first threshold and less than the second threshold, the table storage unit 606 continuously sets the differential limiting amount in accordance with the increase in torque. Data for setting the first stage to be reduced from 0 to 0 and the differential limiting amount to be continuously increased from 0 to the first stage according to the torque decrease is stored. The smaller torque value of the axle shafts 31a and 31b is equal to or greater than the first threshold and less than the second threshold, which means that the wheel loader 1 is in a state of a region C in a region B shown in FIG. .

  Further, the table storage unit 606 stores the differential limiting amount of the differential limiting mechanism 40 when the smaller one of the torque values of the axle shafts 31a and 31b is equal to or more than the second threshold and less than the third threshold. Data for setting to 0 is stored. In addition, that the smaller of the torque values of the axle shafts 31a and 31b is equal to or more than the second threshold and less than the third threshold means that the wheel loader 1 is in the state of the area D in the area B shown in FIG. I do.

  On the other hand, as shown in FIG. 6, when the larger one of the torque values of the axle shafts 31a and 31b is equal to or greater than the third threshold and less than the fourth threshold, the table storage unit 606 responds to the torque increase. Then, data for setting the differential limiting amount to be continuously increased from 0 to the maximum and the differential limiting amount to be continuously reduced from the maximum to 0 according to the decrease in torque is stored. The fact that the larger the torque value of the axle shafts 31a and 31b is equal to or larger than the third threshold and smaller than the fourth threshold means that the wheel loader 1 is in the state of the area F in the area E shown in FIG.

  Further, when the larger one of the torque values of the axle shafts 31a and 31b is greater than or equal to the fourth threshold value and less than the fifth threshold value, the table storage unit 606 increases the differential limiting amount in accordance with the torque increase. From 0 to 0, and the data for setting the differential limiting amount to continuously increase from 0 to the maximum according to the torque decrease are stored. The fact that the larger torque value of the axle shafts 31a and 31b is equal to or greater than the fourth threshold and less than the fifth threshold means that the wheel loader 1 is in the state of the area G in the area 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 one of the torque values of the axle shafts 31a and 31b is equal to or greater than the fifth threshold value. The data for setting is stored. The larger torque value of the axle shafts 31a and 31b is equal to or larger than the fifth threshold value, which 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 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. 6, and the value of the torque used for the determination. Is output to the control amount determination unit 610.

  The control amount determination unit 610 determines the differential value provided in the axle device 12 according to the determination result 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 device controller 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, determines the difference between the differential limiting mechanisms 40 according to the torque amounts of the axle shafts 31a and 31b. Variablely adjust the dynamic control amount.

  Next, a differential control process 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 executed. The control unit 600 initializes and activates each component of the axle control program 60 at a fixed period (for example, every 10 ms), and controls 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 the outer-side sensors 120a, 120b and the inner-side sensors 122a, 122a. Based on the phase difference of the signal output from 120b, the torque value applied to 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, 31b measured by the sensors 120a, 120b, 122a, 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 which state of 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 control amount is output to control amount determination section 610. Specifically, it is determined which 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. It is realized by processing. Further, the determination of the differential limit to be set is realized by the processing of S114, S118, S122, and S124.

  That is, in step 108 (S108), the data comparison unit 608 determines whether the larger one of the torque values of the axle shafts 31a and 31b is equal to or greater than 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 equal to or greater than the fifth threshold value (YES), and when the wheel loader 1 is in the region H, and otherwise (NO). Proceeds to the process of S110.

  In step 110 (S110), the data comparing unit 608 determines whether the larger one of the torque values of the axle shafts 31a and 31b is equal to or greater than a fourth threshold value. The axle control program 60 determines that the larger torque value of the axle shafts 31a, 31b is greater than or equal to the fourth threshold value (YES), proceeds to S114 when the wheel loader 1 is in the area G, and otherwise (NO). Goes to the processing of S112.

  In step 112 (S112), the data comparison unit 608 determines whether the larger one of the torque values of the axle shafts 31a and 31b is equal to or greater than the third threshold. The axle control program 60 determines that the larger torque value of the axle shafts 31a, 31b is greater than or equal to the third threshold value (YES), proceeds to S114 when the wheel loader 1 is in the area F, and otherwise (NO). Goes to the processing of 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 control amount determination unit 610 increases the differential limit amount of the differential limit mechanism 40 from 0 in accordance with the increase or decrease of the torque. A control signal is output to the hydraulic control unit 612 so as to increase or decrease during the maximum second stage (for example, the lock ratio 2). On the other hand, when it is determined 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 limiting amount from the second stage to 0 according to the increase or decrease of the torque. A control signal is output 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 a differential control amount as shown in FIG. Further, when the larger of the torque values of the torque values of the axle shafts 31a and 31b is the fourth threshold value, the control amount determination unit 610 determines the differential control amount in the second stage (the lock ratio). 2).

  In step 116 (S116), the data comparison unit 608 determines whether the smaller of the torque values of the axle shafts 31a and 31b is equal to or greater than the second threshold. The axle control program 60 proceeds to the process 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 when the wheel loader 1 is in the area D, and otherwise (NO). Goes to the processing of 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. Outputs 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 a differential control amount as shown in FIG.

  In step 120 (S120), the data comparison unit 608 determines whether the smaller of the torque values of the axle shafts 31a and 31b is equal to or greater than the first threshold. The axle control program 60 determines that the smaller torque value of the axle shafts 31a and 31b is equal to or greater than the first threshold (YES), proceeds to S124 when the wheel loader 1 is in the area C, and otherwise (NO). Proceeds 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. A control signal is output to the hydraulic device controller 612 so as to increase or decrease from 0) to 0. The hydraulic device control unit 612 controls the hydraulic device 44 based on a command from the control amount determination unit 610, and sets a 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 area A shown in FIG. 6, the control amount determination unit 610 controls the hydraulic pressure to set the differential limit amount to the first stage (lock ratio 1). A control signal is output to the 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 a differential control amount as shown in FIG.

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

  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 value are measured. Since the axle control device (controller) 50 variably controls the differential limiting amount (lock ratio) of the differential limiting mechanism 40 according to the operating state of the loader 1, as shown in regions A and B in FIG. In addition, even when the wheel loader 1 is running, the wheel loader 1 has a slip prevention function, and can prevent slippage during running on a soft ground having a low coefficient of road surface friction.

  Further, in the excavation state of the wheel loader 1, even when the rear wheel 4 floats and one of the front wheels 5 is in a slip state, 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, the overload state in which the full output of the engine 7 is applied to one wheel is prevented, 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 has been exemplified. However, the function of the axle control program 60 may be realized by using dedicated hardware or by using dedicated hardware. You may make it implement | achieve using software together.

  Further, in the above embodiment, the case where the axle control device 50 linearly 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 limiting amount shown in FIG. 6 may change in a curved manner according to the road condition of the wheel loader 1 or the excavation site, and the first to fifth threshold values may be set arbitrarily. Is possible.

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

  The above-described embodiments are merely examples for describing the present invention, and are not intended to limit the scope of the present invention only to those embodiments. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

Reference Signs List 1 wheel loader 2 rear body 3 front body 4 rear wheel 5 front wheel 6 work 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 limit 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 one or both of the front axle and the rear axle, in a differential limiting device of a wheel loader having a differential limiting mechanism for controlling a differential device of a traveling axle,
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 that controls the differential limiting mechanism based on the detected value,
The controller is
Among the left and right wheels detected by the torque measuring device, the torque of the wheel with the smaller torque is maintained in a running state and the differential limiting amount is kept at a constant value when the torque is less than a first threshold value.
When the torque on the wheel with the smaller torque among the left and right wheels detected by the torque measuring device is greater than or equal to the first threshold and less than the second threshold in a running state, the differential limiting amount is increased in accordance with an increase in the torque. Continuously lower,
Among the left and right wheels detected by the torque measuring device, the torque on the wheel side with a smaller torque is such that the differential limiting amount is kept at 0 when the running state is equal to or more than the second threshold and less than the third threshold,
A differential limiting device for a wheel loader, wherein each of the right and left wheels is controlled. The differential limiting device for a wheel loader according to claim 1,
The controller is
When the torque of the wheel with the larger torque of the left and right wheels detected by the torque measuring device is greater than or equal to the third threshold and less than the fourth threshold in the excavation state, the differential limiting amount is increased in accordance with the increase in the torque. Continuously raised,
When the torque on the wheel with the larger torque among the left and right wheels detected by the torque measuring device is greater than or equal to the fourth threshold and less than the fifth threshold in the excavation state, the differential limiting amount is increased in accordance with the increase in the torque. Continuously lower,
When the torque of the wheel with the larger torque among the left and right wheels detected by the torque measuring device reaches the fifth threshold value in the excavation state, the differential limiting amount is set to 0 and the torque is reduced to the fifth threshold value. Not to be bigger,
A differential limiting device for a wheel loader, wherein each of the right and left wheels is controlled. The differential limiting device for a wheel loader according to claim 1 or 2,
Among the pair of hub bearings that support both ends in the longitudinal direction of the axle shaft, the torque measuring device is provided with a sensor attached to an inner bearing of one hub bearing and an outer bearing of the other hub bearing. A differential limiting device for a wheel loader, wherein a torque acting on the axle shaft is calculated based on a phase difference between sensors.