JP6683664B2 - Wheel loader - Google Patents

Description

  The present invention relates to a wheel loader.

  In a wheel loader, during excavation work or cargo handling work, the front working device may be operated at the same time as or immediately after the accelerator pedal is depressed. is there.

  For example, in Patent Document 1, a traveling drive device that transmits the rotation of the engine to the tires through a torque converter and a transmission, a front work device that includes a lift arm that is vertically rotatable, and a front work device that is driven by the engine A wheel loader is disclosed that includes a variable displacement hydraulic pump that supplies pressure oil to an actuator that drives the device, and a controller that controls each part of the vehicle body.

  With this wheel loader, the maximum absorption torque (maximum input torque) of the hydraulic pump with respect to the actual engine speed is changed according to the amount of depression of the accelerator pedal, thereby increasing the rate of increase in the actual engine speed and increasing the engine speed. It has improved climbing performance.

JP, 2005-86575, A

  However, in the wheel loader described in Patent Document 1, the increase rate of the actual rotation speed of the engine is high even in the so-called rise run operation in which the lift arm is moved upward during forward traveling of the vehicle body. For this reason, the traveling speed of the vehicle body increases faster, and the raising speed of the lift arm becomes slower than the traveling speed. Then, it takes a long time for the lift arm to move upward, and it becomes necessary to set a long travel distance for the rise run operation. In addition, as the traveling distance increases, the fuel consumption of the wheel loader also increases.

  Therefore, an object of the present invention is to provide a wheel loader capable of reducing the fuel consumption by shortening the traveling distance required for the rise run operation.

  In order to achieve the above object, the present invention is a wheel loader including a front working machine provided at a front portion of a vehicle body and having a lift arm that is rotatable in the up-down direction. A variable displacement hydraulic pump that is driven to supply hydraulic oil to the front working machine; a traveling state detector that detects a traveling state of the vehicle body; an operation detector that detects a lifting operation of the lift arm; A controller that controls the maximum input torque of the hydraulic pump with respect to the actual rotation speed of the engine, the controller comprising: a traveling state detected by the traveling state detector; and the lift arm detected by the operation detector. Whether a specific condition for specifying the upward movement of the lift arm during forward traveling of the vehicle body is satisfied based on the state of the raising motion of the vehicle. And determining that when the specific condition is satisfied, the maximum input torque of the hydraulic pump with respect to the actual rotation speed of the engine is changed to a value larger than the maximum input torque when the specific condition is not satisfied. To do.

  According to the present invention, it is possible to shorten the travel distance required for the rise run operation and suppress fuel consumption. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is a side view which shows the external appearance of the wheel loader which concerns on embodiment of this invention. It is explanatory drawing explaining V shape loading by a wheel loader. It is explanatory drawing explaining the rise run operation of a wheel loader. It is a figure which shows the hydraulic circuit and electric circuit of a wheel loader. 6 is a graph showing the relationship between the maximum vehicle speed and the driving force for each speed stage. 6 is a graph showing a relationship between an accelerator pedal depression amount and a target engine rotation speed. 6 is a graph showing a relationship between a lift operation amount of a lift arm and an opening area of a spool. 4 is a graph showing the relationship between the actual engine speed and torque. It is a functional block diagram which shows the function which a controller has. It is a flowchart which shows the flow of the process performed by a controller. It is a graph which shows the relationship between the discharge pressure of a hydraulic pump, and the displacement volume of a hydraulic pump.

  The overall configuration and operation of the wheel loader according to the embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a side view showing the outer appearance of a wheel loader 1 according to each embodiment of the present invention.

  The wheel loader 1 includes a vehicle body including a front frame 1A and a rear frame 1B, and a front working machine 2 provided at a front portion of the vehicle body. The wheel loader 1 is an articulation type working machine that steers a vehicle body by bending around the center. The front frame 1A and the rear frame 1B are connected by a center joint 10 so as to be rotatable in the left-right direction, and the front frame 1A is bent in the left-right direction with respect to the rear frame 1B.

  The front frame 1A is provided with a pair of left and right front wheels 11A and a front working machine 2. The rear frame 1B has a pair of left and right rear wheels 11B, an operator's cab 12 on which an operator rides, a machine room 13 for accommodating components such as an engine, a controller, and a cooler, and a balance for keeping the vehicle body from tilting. A counter weight 14 is provided. In FIG. 1, only the left front wheel 11A and the rear wheel 11B are shown among the pair of left and right front wheels 11A and the rear wheels 11B.

  The front working machine 2 includes a lift arm 21 that is vertically rotatable, a pair of lift arm cylinders 22 that expand and contract to drive the lift arm 21, and a bucket 23 attached to the tip end of the lift arm 21. A bucket cylinder 24 that expands and contracts to rotate the bucket 23 in the vertical direction with respect to the lift arm 21, and a bell crank that is rotatably connected to the lift arm 21 and forms a link mechanism between the bucket 23 and the bucket cylinder 24. 25, and a plurality of pipes (not shown) for guiding the pressure oil to the pair of lift arm cylinders 22 and the bucket cylinders 24. In FIG. 1, only the lift arm cylinder 22 arranged on the left side of the pair of lift arm cylinders 22 is shown by a broken line.

  The lift arms 21 rotate upward when the rods 220 of the lift arm cylinders 22 extend, and rotate downward when the rods 220 contract. The bucket 23 rotates upward (tilt) with respect to the lift arm 21 when the rod 240 of the bucket cylinder 24 extends, and rotates downward (dump) with respect to the lift arm 21 when the rod 240 contracts. To do.

  This wheel loader 1 is a working machine for excavating earth and sand and minerals and loading them on a dump truck in an open pit mine, for example. Next, V shape loading, which is one of the methods when the wheel loader 1 performs the excavation work and the loading work, will be described with reference to FIGS. 2 and 3.

  FIG. 2 is an explanatory diagram illustrating V shape loading by the wheel loader 1. FIG. 3 is an explanatory diagram illustrating a rise run operation of the wheel loader 1.

  First, as shown by the arrow X1, the wheel loader 1 advances toward the rock mass 100A to be excavated and causes the bucket 23 to enter the rock mass 100A to perform the excavation work. When the excavation work is completed, the wheel loader 1 temporarily retreats to its original position, as indicated by the arrow X2.

  Next, the wheel loader 1 advances toward the dump truck 100B and stops before the dump truck 100B, as indicated by an arrow Y1. In FIG. 2, the wheel loader 1 in a state of being stopped before the dump truck 100B is shown by a broken line.

  Specifically, as shown in FIG. 3, the operator fully depresses the accelerator pedal (full accelerator) and raises the lift arm 21 (state shown on the right side in FIG. 3). Next, the lift arm 21 is further raised in the full accelerator state (state shown in the center of FIG. 3). Then, the operator operates the brake to stop before the dump truck 100B, dumps the bucket 23, and loads the load (earth and sand, minerals, etc.) in the bucket 23 onto the dump truck 100B. The series of operations shown in FIG. 3 is referred to as a "rise run operation".

  When the loading operation is completed, the wheel loader 1 retracts to the original place as indicated by the arrow Y2 in FIG. In this way, the wheel loader 1 travels back and forth in a V shape between the natural ground 100A and the dump truck 100B to perform excavation work and loading work.

(About the drive system of the wheel loader 1)
Next, the drive system of the wheel loader 1 will be described with reference to FIGS.

  FIG. 4 is a diagram showing a hydraulic circuit and an electric circuit of the wheel loader 1. FIG. 5 is a graph showing the relationship between the maximum vehicle speed and the driving force for each speed stage. FIG. 6 is a graph showing the relationship between the depression amount of the accelerator pedal 61 and the target engine rotation speed. FIG. 7 is a graph showing the relationship between the lifting operation amount of the lift arm 21 and the opening area of the spool. FIG. 8 is a graph showing the relationship between the actual rotation speed of the engine 3 and the torque.

  In the wheel loader 1 according to the present embodiment, the traveling of the vehicle body is controlled by a torque converter type traveling drive system, and as shown in FIG. 4, an engine 3 and an input shaft are connected to an output shaft of the engine 3. A torque converter 41 (hereinafter referred to as “torque converter 41”), a transmission 42 connected to the output shaft of the torque converter 41, and a controller 5 for controlling each device such as the engine 3 are provided.

  The torque converter 41 is a fluid clutch including an impeller, a turbine, and a stator, and has a function of increasing an output torque with respect to an input torque, that is, a function of setting a torque ratio (= output torque / input torque) to 1 or more. . This torque ratio decreases as the torque converter speed ratio (= output shaft rotation speed / input shaft rotation speed), which is the ratio of the rotation speed of the input shaft of the torque converter 41 to the rotation speed of the output shaft, increases. As a result, the rotation of the engine 3 is changed and then transmitted to the transmission 42.

  The transmission 42 is a transmission having a plurality of solenoid valves whose maximum vehicle speed corresponds to the first to fourth speed stages as shown in FIG. 5, and changes the rotation of the output shaft of the torque converter 41. The selection of the first to fourth speed stages is performed by the speed stage switch 63 (see FIG. 4) provided in the operator's cab 12.

  When the operator selects a desired speed stage with the speed stage switch 63, a speed stage signal relating to the selected speed stage is output from the speed stage switch 63 to the controller 5. Then, the controller 5 outputs the speed stage signal to the transmission control unit 420, and each of the plurality of solenoid valves of the transmission 42 is driven according to the speed stage signal.

  As shown in FIG. 5, the maximum vehicle speed is set to S1 for the first speed stage, S2 for the second speed stage, S3 for the third speed stage, and S4 for the fourth speed stage. ing. The magnitude relationship among S1, S2, S3, and S4 is S1 <S2 <S3 <S4. In FIG. 5, the first speed stage is shown by a solid line, the second speed stage is shown by a broken line, the third speed stage is shown by a one-dot chain line, and the fourth speed stage is shown by a two-dot chain line.

  In the present embodiment, the “1st speed stage” is the speed stage selected during the excavation work of the wheel loader 1. The "2nd speed stage" corresponds to the low speed stage selected during the rise run operation when the wheel loader 1 travels toward the dump truck 100B in the loading operation (indicated by the arrow Y1 in Fig. 2), and is the highest. The vehicle speed is set to 9 to 15 km / hour, for example. The “third speed stage” and the “fourth speed stage” are the speed stages selected when the wheel loader 1 travels on the conveyance path or the like.

  The traveling direction of the wheel loader 1, that is, the selection of forward or reverse is performed by a forward / reverse selector switch 62 (see FIG. 4) provided in the operator's cab 12. Specifically, when the operator switches to the forward position with the forward / backward changeover switch 62, a forward / backward changeover signal indicating forward movement is output to the controller 5, and the controller 5 sets the forward clutch of the transmission 42 to the engaged state. The command signal is output to the transmission control unit 420. When the transmission control unit 420 receives the command signal relating to the forward movement, the clutch control valve provided in the transmission control unit 420 is activated to bring the forward clutch into the engaged state, and the traveling direction of the vehicle body is switched to the forward direction. The reverse of the vehicle body is also switched by the same mechanism.

  In the torque converter type traveling drive system, first, when the operator depresses the accelerator pedal 61 provided in the cab 12, the engine 3 rotates, and the input shaft of the torque converter 41 rotates as the engine 3 rotates. Then, the output shaft of the torque converter 41 rotates according to the set torque converter speed ratio, and the output torque from the torque converter 41 is transmitted to the front wheels 11A and the rear wheels 11B via the transmission 42, the propeller shaft 16, and the axle 15. As a result, the wheel loader 1 runs.

  Specifically, the depression amount of the accelerator pedal 61 detected by the depression amount detector 610 is input to the controller 5, and the target engine rotation speed is output from the controller 5 to the engine 3 as a command signal. The rotation speed of the engine 3 is controlled according to this target engine rotation speed. As shown in FIG. 4, the rotation speed of the engine 3 is detected by a first rotation speed sensor 71 provided on the output shaft side of the engine 3.

  As shown in FIG. 6, the depression amount of the accelerator pedal 61 and the target engine rotation speed are in a proportional relationship, and the larger the depression amount of the accelerator pedal 61, the faster the target engine rotation speed. As a result, the rotation speed of the output shaft of the torque converter 41 increases and the vehicle speed increases. As shown in FIG. 4, the vehicle speed is detected by the second rotation speed sensor 72 as the rotation speed of the propeller shaft 16.

  Note that in FIG. 6, the target engine rotation speed is constant at the minimum target engine rotation speed Vmin regardless of the depression amount of the accelerator pedal 61 in the range of 0% to 20% or 30% of the depression amount of the accelerator pedal 61. . Further, in the range of the depression amount of the accelerator pedal 61 of 70 or 80% to 100%, the target engine rotation speed is constant at the maximum target engine rotation speed Vmax regardless of the depression amount of the accelerator pedal 61.

  As described above, in the relationship between the depression amount of the accelerator pedal 61 and the target engine rotation speed, the target engine rotation speed is maintained at the minimum target engine rotation speed Vmin in the predetermined region where the depression amount of the accelerator pedal 61 is small. The target engine rotation speed is set to the maximum target engine rotation speed Vmax in a predetermined region where the accelerator pedal 61 is depressed a large amount. Note that these settings can be changed arbitrarily.

  As shown in FIG. 4, the wheel loader 1 is driven by the engine 3 to supply a hydraulic oil to the front working machine 2, a hydraulic pump 43 for storing the hydraulic oil, and a lift arm 21. A lift arm operating lever 210 for operating the bucket, a bucket operating lever 230 for operating the bucket 23, and a control for controlling the flow of pressure oil supplied from the hydraulic pump 43 to the lift arm cylinder 22 and the bucket cylinder 24, respectively. And a valve 64.

  The hydraulic pump 43 is a swash plate type or swash shaft type variable displacement hydraulic pump whose displacement volume is controlled according to the tilt angle. The tilt angle is adjusted by the regulator 430 according to the command signal output from the controller 5. The discharge pressure from the hydraulic pump 43 is detected by the pressure detector 73, and a signal related to the detected discharge pressure is output to the controller 5.

  When the operator operates the lift arm operation lever 210 in the direction of raising the lift arm 21, for example, a pilot pressure corresponding to the operation amount is generated. This pilot pressure is detected by the operation amount detector 74 as the amount of lift operation of the lift arm 21 by the lift arm operation lever 210, and a signal related to the detected operation amount is output to the controller 5.

  Then, the generated pilot pressure acts on the control valve 64, and the spool in the control valve 64 strokes according to the pilot pressure. The hydraulic fluid discharged from the hydraulic pump 43 flows into the lift arm cylinder 22 via the control valve 64, whereby the rod 220 of the lift arm cylinder 22 extends.

  As shown in FIG. 7, the lifting operation amount [%] of the lift arm 21 and the opening area [%] of the spool of the control valve 64 are in a proportional relationship, and when the lifting operation amount of the lift arm 21 increases, the opening area of the spool increases. Also grows. Therefore, when the lift arm operating lever 210 is operated to a large extent in the direction of raising the lift arm 21, the amount of hydraulic oil flowing into the lift arm cylinder 22 increases, and the rod 220 extends rapidly.

  In FIG. 7, the spool does not open and the opening area is 0% (dead zone) in the range of 0 to 20% of the lifting operation amount of the lift arm 21. Further, in the range of the lift operation amount of the lift arm 21 of 85 to 100%, the opening area of the spool is constant at 100%, and the full lever operation state is maintained.

  As for the operation of the bucket 23, as in the case of the operation of the lift arm 21, the pilot pressure generated according to the operation amount of the bucket operation lever 230 acts on the control valve 64 to control the opening area of the spool of the control valve 64. Then, the amount of hydraulic oil flowing in and out of the bucket cylinder 24 is adjusted.

  Although not shown in FIG. 4, operation amount (pilot pressure) detectors for detecting the lowering operation amount of the lift arm 21 and the tilting and dumping operation amounts of the bucket 23 are also included in the hydraulic circuit. It is provided on the pipeline.

  Here, regarding the relationship between the output torque and the actual rotation speed of the engine 3, the relationship between the actual rotation speed of the engine 3 and the input torque of the hydraulic pump 43, and the relationship between the actual rotation speed of the engine 3 and the input torque of the torque converter 41, FIG. Each will be described with reference to. In the following, the "actual rotation speed of the engine 3" is simply referred to as "engine actual rotation speed".

  A characteristic line E in FIG. 8 shows the characteristic of the output torque with respect to the actual rotation speed of the engine 3. In the characteristic line E, as the engine actual rotation speed Vi increases as the engine actual rotation speed Vi increases in the range from the low idle rotation speed (minimum rotation speed) Va to the predetermined rotation speed Vb (Va ≦ Vi ≦ Vb). The output torque of the engine 3 also increases, and the output torque of the engine 3 reaches the maximum value Nmax when the actual engine rotation speed Vi is the predetermined rotation speed Vb. That is, the “predetermined rotation speed Vb” becomes the “rotation speed at the maximum output torque”. The “low idle rotation speed” is the actual engine rotation speed when the accelerator pedal 61 is not operated.

  In the characteristic line E, when the actual engine speed Vi is higher than the predetermined engine speed Vb (Vi> Vb), the output torque of the engine 3 decreases when the actual engine speed Vi increases, and the rated point R is reached. When it reaches, the rated output is obtained. When the actual engine rotation speed Vi increases beyond the rated rotation speed Vr at the rated point R (Vi> Vr), the output torque of the engine 3 sharply decreases (droop characteristic).

  Characteristic lines A and B in FIG. 8 show the characteristics of the input torque of the hydraulic pump 43 with respect to the actual engine speed. The characteristic line A indicates the characteristic when the lift arm 21 is largely lifted and operated, and in the present embodiment, the lift operation amount of the lift arm 21 is 75% or more. The characteristic line B shows the characteristic when the lift arm 21 is operated small or not operated, and in the present embodiment, the lift operation amount of the lift arm 21 is less than 75%. In addition, in FIG. 8, the characteristic line B is shown by a dashed-dotted line. In addition, "when the lift arm 21 is largely lifted" means that the lift arm 21 is lifted at least from the horizontal posture.

  Each of the characteristic lines A and B is set with a plurality of characteristic lines corresponding to the amount of depression of the accelerator pedal 61. In the present embodiment, the depression amount of the accelerator pedal 61 is divided into three stages of "small", "medium", and "large", and when the depression amount is small, the characteristic line A1 and the characteristic line B1 and the depression amount are medium. The characteristic line A2 and the characteristic line B2 are in the case of, and the characteristic line A3 and the characteristic line B3 are in the case of a large depression amount.

  The predetermined engine actual rotation speed when the depression amount of the accelerator pedal 61 is small is V1, the predetermined engine actual rotation speed when the depression amount is medium is V2, and the predetermined engine actual rotation speed when the depression amount is large. Is V3. At this time, the magnitude relationship among V1, V2, and V3 is Va <V1 <V2 <V3 <Vb.

  Regarding the characteristic line A1, in the range where the actual engine rotation speed Vi is smaller than V1 (Vi <V1), the input torque of the hydraulic pump 43 is constant at the minimum input torque Nmin regardless of the actual engine rotation speed Vi. In the range where the engine actual rotation speed Vi is V1 or more (Vi ≧ V1), the input torque of the hydraulic pump 43 also increases to the maximum input torque NAmax as the engine actual rotation speed Vi increases, and the input torque of the hydraulic pump 43 reaches the maximum input. When the torque reaches the NAmax, the maximum input torque NAmax becomes constant regardless of the actual engine speed Vi.

  Regarding the characteristic line A2, as in the case of the characteristic line A1, when the actual engine rotation speed Vi is smaller than V2 (Vi <V2), the input torque of the hydraulic pump 43 is the minimum input torque Nmin regardless of the actual engine rotation speed Vi. It will be constant. In the range where the engine actual rotation speed Vi is V2 or more (Vi ≧ V2), the input torque of the hydraulic pump 43 also increases to the maximum input torque NAmax as the engine actual rotation speed Vi increases, and the input torque of the hydraulic pump 43 reaches the maximum input. When the torque reaches the NAmax, the maximum input torque NAmax becomes constant regardless of the actual engine speed Vi.

  Regarding the characteristic line A3, like the characteristic lines A1 and A2, in the range where the actual engine speed Vi is smaller than V3 (Vi <V3), the input torque of the hydraulic pump 43 is the minimum input torque regardless of the actual engine speed Vi. It becomes constant at Nmin. In the range where the engine actual rotation speed Vi is V3 or higher (Vi ≧ V3), the input torque of the hydraulic pump 43 also increases to the maximum input torque NAmax as the engine actual rotation speed Vi increases, and the input torque of the hydraulic pump 43 reaches the maximum input. When the torque reaches the NAmax, the maximum input torque NAmax becomes constant regardless of the actual engine speed Vi.

  Regarding the characteristic line B1, in the range where the actual engine rotation speed Vi is smaller than V1 (Vi <V1), as with the characteristic line A1, the input torque of the hydraulic pump 43 is the minimum input torque Nmin regardless of the actual engine rotation speed Vi. It will be constant. In the range where the engine actual rotation speed Vi is V1 or more (Vi ≧ V1), the input torque of the hydraulic pump 43 also increases to the maximum input torque NBmax as the engine actual rotation speed Vi increases, and the input torque of the hydraulic pump 43 reaches the maximum input. When the torque reaches NBmax, the maximum input torque NBmax becomes constant regardless of the actual engine speed Vi.

  Regarding the characteristic line B2, as in the case of the characteristic line B1, in the range where the actual engine rotation speed Vi is smaller than V2 (Vi <V2), the input torque of the hydraulic pump 43 is the minimum input torque Nmin regardless of the actual engine rotation speed Vi. It will be constant. In the range where the engine actual rotation speed Vi is V2 or more (Vi ≧ V2), the input torque of the hydraulic pump 43 also increases to the maximum input torque NBmax as the engine actual rotation speed Vi increases, and the input torque of the hydraulic pump 43 reaches the maximum input. When the torque reaches NBmax, the maximum input torque NBmax becomes constant regardless of the actual engine speed Vi.

  Regarding the characteristic line B3, like the characteristic lines B1 and B2, in the range where the actual engine rotation speed Vi is smaller than V3 (Vi <V3), the input torque of the hydraulic pump 43 is the minimum input torque regardless of the actual engine rotation speed Vi. It becomes constant at Nmin. In the range where the engine actual rotation speed Vi is V3 or more (Vi ≧ V3), the input torque of the hydraulic pump 43 also increases to the maximum input torque NBmax as the engine actual rotation speed Vi increases, and the input torque of the hydraulic pump 43 reaches the maximum input. When the torque reaches NBmax, the maximum input torque NBmax becomes constant regardless of the actual engine speed Vi.

  As shown in FIG. 8, the maximum input torque NAmax of the hydraulic pump 43 on the characteristic line A (characteristic lines A1, A2, A3) is equal to the maximum input torque NAmax of the hydraulic pump 43 on the characteristic line B (characteristic lines B1, B2, B3). It is set to a value larger than NBmax (NAmax> NBmax).

  Further, in the present embodiment, the range of the actual engine rotation speed Vi is divided into three rotation speed regions of "low speed rotation region Z1", "medium speed rotation region Z2", and "high speed rotation region Z3", In the characteristic line A, the input torque of the hydraulic pump 43 reaches the maximum input torque NAmax in the range of the medium speed rotation range Z2 or the high speed rotation range Z3. The "medium speed rotation range Z2" includes the actual engine rotation speed Vb (the rotation speed Vb at the maximum output torque) at which the output torque of the engine 3 reaches the maximum value Nmax.

  A characteristic line C in FIG. 8 shows the characteristic of the input torque of the torque converter 41 with respect to the actual engine speed. In the characteristic line C, the input torque of the torque converter 41 increases to a power as the actual engine speed Vi increases. As described above, in FIG. 8, the characteristic line E is a combination of the characteristic line A or the characteristic line B and the characteristic line C (characteristic line E = characteristic line A or characteristic line B + characteristic line C).

(Structure and function of controller 5)
Next, the configuration and function of the controller 5 will be described with reference to FIGS.

  FIG. 9 is a functional block diagram showing functions of the controller 5. FIG. 10 is a flowchart showing the flow of processing executed by the controller 5. FIG. 11 is a graph showing the relationship between the discharge pressure of the hydraulic pump 43 and the displacement volume of the hydraulic pump.

  The controller 5 is configured by connecting a CPU, a RAM, a ROM, a HDD, an input I / F, and an output I / F to each other via a bus. Then, various operation devices such as the forward / reverse switching switch 62 and the speed stage switch 63, and various detectors such as the stepping amount detector 610 and the operation amount detector 74 (see FIG. 4) are connected to the input I / F, The engine 3, the transmission control unit 420 of the transmission 42, the regulator 430 of the hydraulic pump 43, and the like are connected to the output I / F.

  In such a hardware configuration, the CPU reads an arithmetic program (software) stored in a recording medium such as a ROM, an HDD, or an optical disk, expands the arithmetic program on the RAM, and executes the expanded arithmetic program to perform an arithmetic operation. The program and the hardware work together to realize the function of the controller 5.

  In the present embodiment, the configuration of the controller 5 is described as a combination of software and hardware, but the present invention is not limited to this, and an integrated circuit that realizes the function of the arithmetic program executed on the side of the wheel loader 1 is used. It may be configured by using.

  As shown in FIG. 9, the controller 5 includes a data acquisition unit 51, a storage unit 52, a determination unit 53, a setting unit 54, and a command signal output unit 55.

  The data acquisition unit 51 includes a forward / reverse forward / backward switching signal output from the forward / backward changeover switch 62, a depression amount of the accelerator pedal 61 detected by a depression amount detector 610, and a lift detected by an operation amount detector 74. Data concerning the pilot pressure Pi as the operation amount for raising the arm 21, the actual engine rotation speed Vi detected by the first rotation speed sensor 71, and the speed stage signal output from the speed stage switch 63 are acquired.

  The storage unit 52 stores the maximum input torque NAmax on the characteristic line A and the maximum input torque NBmax on the characteristic line B shown in FIG. 8, and also stores the first pilot threshold P1 and the second pilot as the thresholds related to the lifting operation of the lift arm 21. The threshold value P2 is stored.

  The first pilot threshold P1 is the pilot pressure when the lift arm 21 is raised above the horizontal posture, and is, for example, 75% (P1 = 75%). The first pilot threshold value P1 may be at least the pilot pressure when the lift arm 21 is in the horizontal posture in the situation where the lift arm 21 is performing the raising operation. The second pilot threshold value P2 is the pilot pressure when the lift arm 21 is fully raised, that is, 100% (P2 = 100%).

  The determination unit 53 determines whether or not the wheel loader 1 is traveling forward based on the forward / reverse switching signal acquired by the data acquisition unit 51 and the depression amount of the accelerator pedal 61, and the data acquisition unit 51 Based on the acquired pilot pressure Pi, it is determined whether or not the lift arm 21 is in the raising operation. Hereinafter, the condition for specifying the upward movement of the lift arm 21 during the forward traveling of the wheel loader 1 is referred to as a “specific condition”, and the case of satisfying this “specific condition” means performing the above-mentioned rise run operation. If there is.

  Here, the forward / rearward travel changeover switch 62 and the stepping amount detector 610 are each an aspect of a running state detector that detects the running state of the vehicle body of the wheel loader 1, and the operation amount detector 74 is a lift of the lift arm 21. It is one mode of a motion detector that detects motion.

  In the present embodiment, the forward traveling of the vehicle body is determined based on the forward / reverse switching signal output from the forward / reverse switching switch 62 indicating the forward movement and the depression amount of the accelerator pedal 61 detected by the depression amount detector 610. However, the present invention is not limited to this, and forward traveling of the vehicle body may be comprehensively determined based on the respective traveling states detected by the other traveling state detectors mounted on the vehicle body.

  Further, in the present embodiment, the determination unit 53, when it is determined that the specific condition is satisfied (during the rise run operation), the pilot pressure Pi acquired by the data acquisition unit 51 and the first pilot read from the storage unit 52. Based on the threshold P1 and the second pilot threshold P2, the magnitude relationship between the pilot pressure Pi and the first pilot threshold P1 and the second pilot threshold P2 is determined.

  Further, the determination unit 53 determines whether the actual engine rotation speed Vi acquired by the data acquisition unit 51 is included in the “medium speed rotation region” or the “high speed rotation region” (see FIG. 8). Furthermore, the determination unit 53 determines whether the low speed stage (corresponding to the second speed stage shown in FIG. 5 in the present embodiment) is selected based on the speed stage signal acquired by the data acquisition unit 51. judge.

  When the determination unit 53 determines that the specific condition is not satisfied (during the operation other than the rise run operation), the setting unit 54 outputs the maximum input torque of the hydraulic pump 43 with respect to the actual engine rotation speed Vi (hereinafter, simply “the maximum input of the hydraulic pump”). Torque ”) is set to a predetermined value NBmax, and when the determination unit 53 determines that the specific condition is satisfied (during the rise run operation), the hydraulic pump maximum input torque is changed from the predetermined value NBmax to the predetermined value NAmax. (Set to a predetermined value NAmax).

  As shown in FIG. 8, the hydraulic pump maximum input torque NAmax set when the specific condition is satisfied is larger than the hydraulic pump maximum input torque NBmax set when the specific condition is not satisfied (NAmax> NBmax). That is, the setting unit 54 changes the hydraulic pump maximum input torque to a value larger than the hydraulic pump maximum input torque when the specific condition is not satisfied, at least when the specific condition is satisfied.

  The command signal output unit 55 outputs a command signal related to the hydraulic pump maximum input torque (NAmax or NBmax) set by the setting unit 54 to the regulator 430 of the hydraulic pump 43.

  The controller 5 is based on the depression amount of the accelerator pedal 61 acquired by the data acquisition unit 51, the characteristic lines A1 and B1, the characteristic lines A2 and B2, and the characteristic line A3 of the input torque of the hydraulic pump 43 shown in FIG. , B3, a selection section for selecting a characteristic line according to the amount of depression can be included. For example, when the detection value detected by the depression amount detector 610 is 85%, it means that the depression amount of the accelerator pedal 61 is large, the selection unit selects the characteristic lines A3 and B3, and the setting unit 54 sets , The maximum input torque value of the hydraulic pump based on the characteristic lines A3 and B3 is set.

  Next, a specific processing flow executed in the controller 5 will be described.

  As shown in FIG. 10, first, the data acquisition unit 51 determines that the forward / reverse switching signal from the forward / reverse switching switch 62, the depression amount of the accelerator pedal 61 from the depression amount detector 610, and the pilot pressure from the operation amount detector 74. Pi, the actual engine rotation speed Vi from the first rotation speed sensor 71, and the speed stage signal from the speed stage switch 63 are acquired (step S501).

  Next, the determination unit 53 determines whether the wheel loader 1 is traveling forward based on the forward / reverse switching signal and the depression amount of the accelerator pedal 61 acquired in step S501, and also acquired in step S501. Based on the pilot pressure Pi, it is determined whether or not the lift arm 21 is performing a raising operation (step S502). That is, in step 502, it is determined whether the specific condition is satisfied.

  When it is determined in step S502 that the specific condition is satisfied (step S502 / YES), the determination unit 53 determines that the pilot pressure Pi acquired in step S501 is equal to or higher than the first pilot threshold P1 read from the storage unit 52, and It is determined whether it is smaller than the second pilot threshold P2 (step S503).

  When it is determined in step S503 that the pilot pressure Pi is equal to or higher than the first pilot threshold P1 and smaller than the second pilot threshold P2 (P1 ≦ Pi <P2) (step S503 / YES), the determination unit 53 determines It is determined whether the actual engine rotation speed Vi acquired in step S501 is included in the "medium speed rotation region Z2" or the "high speed rotation region Z3" shown in FIG. 8 (step S504).

  When it is determined in step S504 that the actual engine rotation speed Vi is included in the "medium speed rotation region Z2" or the "high speed rotation region Z3" (step S504 / YES), the determination unit 53 determines the speed acquired in step S501. It is determined whether or not the stage signal is "low speed stage" (step S505).

  When it is determined in step S505 that the speed stage is the "low speed stage" (step S505 / YES), the setting unit 54 sets the hydraulic pump maximum input torque to NAmax (> NBmax) (step S506). Therefore, if YES in any of steps S502, S503, S504, and S505, the hydraulic pump maximum input torque is changed from NBmax to NAmax, and the input torque characteristic line of the hydraulic pump 43 shown in FIG. To characteristic line A.

  On the other hand, if it is not determined in step S503 that the pilot pressure Pi is greater than or equal to the first pilot threshold P1 and smaller than the second pilot threshold P2 (P1 ≦ Pi <P2) (step S503 / NO), the determination unit 53 determines whether or not the pilot pressure Pi is the second pilot threshold P2 (step S503A). In step S503A, when the pilot pressure Pi is the second pilot threshold value P2 (Pi = P2) (step S503A / YES), the lift arm 21 is in a state of being fully lifted upward, and therefore the controller 5 performs the process. finish.

  Here, if it is determined in step S502 that the specific condition is not satisfied (step S502 / NO), if it is determined in step S503A that the pilot pressure Pi is not the second pilot threshold P2 (step S503A / NO), that is, the pilot When the pressure Pi is smaller than the first pilot threshold value P1 (Pi <P1), the actual engine rotation speed Vi is not included in the “medium speed rotation range Z2” or the “high speed rotation range Z3” (“low speed rotation range” in step S504). Z1 ”) (step S504 / NO), and when it is determined in step S505 that the speed stage is not the“ low speed stage ”(step S505 / NO), the setting unit 54 , Set the maximum input torque of the hydraulic pump to NBmax (<NAmax). -Up S507).

  In the present embodiment, if the specific condition is satisfied in step S502 (step S502 / YES), and if “YES” is determined in each of step S503, step S504, and step S505, the setting unit 54 sets the hydraulic pump. The maximum input torque is set to a value NAmax larger than the hydraulic pump maximum input torque NBmax when the specific condition is not satisfied (step S506), but steps S503, S504, and S505 are omitted and step S506 is omitted. You may proceed to. That is, at least when the specific condition is satisfied in step S502 (step S502 / YES), the setting unit 54 sets the hydraulic pump maximum input torque to a value NAmax larger than the hydraulic pump maximum input torque NBmax when the specific condition is not satisfied. May be set to (step S506).

  In the processing in the controller 5, if the processing in step S503, step S504, and step S505 is omitted, the termination condition of the processing in the controller 5 is the processing in step S503A.

  The command signal output unit 55 outputs a command signal to the regulator 430 based on the hydraulic pump maximum input torque (NAmax or NBmax) set in step S506 or step S507 (step S508). After the command signal output unit 55 outputs the command signal to the regulator 430 in step S508, the process returns to step S501 and the process is repeated.

  Therefore, when the operation other than the rise-run operation (or when the lift arm 21 is operated to be raised slightly in the rise-run operation) is switched to the rise-run operation (or when the lift arm 21 is operated to be raised largely in the rise-run operation), the controller 5 causes the hydraulic pressure to change. The pump maximum input torque is changed from NBmax to NAmax which is a larger value than NBmax (NBmax → NAmax, NAmax> NBmax). That is, the controller 5 controls the hydraulic pump maximum input torque so as to shift the characteristic line of the input torque of the hydraulic pump 43 from the characteristic line B to the characteristic line A, as shown in FIG. 8.

  At this time, as shown in FIG. 8, the torque (intersection point E2 shown in FIG. 8) obtained by adding the maximum input torque of the hydraulic pump (characteristic line A) and the input torque of the torque converter 41 (characteristic line C) during the rise-run operation is , The hydraulic pump maximum input torque (characteristic line B) during operation other than the rise-run operation and the input torque of the torque converter 41 (characteristic line C) are larger than the combined torque (intersection point E1 shown in FIG. 8). Therefore, the actual engine rotation speed Vy2 during the rise run operation becomes smaller than the actual engine rotation speed Vy1 during the operation other than the rise run operation (Vy2 <Vy1). As a result, the efficiency of the engine 3 is improved and the fuel consumption can be reduced.

  Here, since the input torque of the hydraulic pump 43 is represented by the product of the discharge pressure of the hydraulic pump 43 and the displacement volume (input torque = discharge pressure x displacement volume), the characteristic line of the input torque of the hydraulic pump 43 is When the characteristic line B is shifted to the characteristic line A, as shown in FIG. 11, the value of the displacement volume with respect to the discharge pressure Pa of the hydraulic pump 43 increases from q1 to q2 (q1 → q2, q2> q1).

  Further, since the discharge flow rate Qi of the pressure oil discharged from the hydraulic pump 43 is expressed by the product of the displacement volume qi and the actual engine rotation speed Vi (discharge volume = displacement volume × actual engine rotation speed), the rise run operation is performed. The ratio (q2 / q1) between the displacement volume q2 of the hydraulic pump 43 during operation and the displacement volume q1 of the hydraulic pump during operation other than the rise run operation is equal to the actual engine speed Vy2 during the rise run operation and during the operation other than the rise run operation. The controller 5 controls the maximum input torque of the hydraulic pump (shifts from the characteristic line B to the characteristic line A) so that the ratio (Vy1 / Vy2) with respect to the actual engine rotation speed Vy1 becomes equal to or more (q2 × Vy2 ≧ q1 × Vy1). ).

  As a result, the discharge flow rate Q2 of the hydraulic pump 43 during the rise run operation becomes equal to or higher than the discharge flow rate Q1 of the hydraulic pump 43 during the operation other than the rise run operation (Q2 ≧ Q1). Therefore, the time (rise time) t2 until the discharge amount of the hydraulic pump 43 increases during the rise run operation and the lift arm 21 is fully lifted upward is less than the rise time t1 of the lift arm 21 during the operation other than the rise run operation. (T2 ≦ t1).

  As described above, during the operation other than the rise-run operation, the discharge flow rate Q1 from the hydraulic pump 43 becomes equal to or less than the discharge flow rate Q2 from the hydraulic pump 43 during the rise-run operation (Q1 ≦ Q2). It is possible to reduce the amount of pressure oil that is squeezed out by, and to suppress energy loss (fuel consumption).

  In the present embodiment, when the pilot pressure Pi related to the lifting operation of the lift arm 21 is equal to or higher than the first pilot threshold P1 and smaller than the second pilot threshold P2 (P1 ≦ Pi <P2), the controller 5 is set. The unit 54 sets the maximum input torque of the hydraulic pump to NAmax. In this case, since the opening area of the spool of the control valve 64 is as large as 75% or more, for example, even if the discharge flow rate Qi of the pressure oil discharged from the hydraulic pump 43 is large, the spool of the control valve 64 throttles. The amount of pressure oil to be discarded can be reduced. This makes it possible to minimize energy loss (fuel consumption).

  Further, the actual engine rotation speed Vy2 during the rise run operation is lower than the actual engine rotation speed Vy1 during the operation other than the rise run operation (Vy2 <Vy1), and the rise time t2 of the lift arm 21 during the rise run operation is the rise run operation. Since the lift time of the lift arm 21 during the operation other than is less than or equal to t1 (t2 ≦ t1), the travel distance L2 required for the rise run operation is shorter than the travel distance L1 required for the operation other than the rise run operation (L2 <L1). In this way, the traveling distance required for the rise run operation is shortened, so that fuel consumption can be reduced.

  In the present embodiment, the controller 5 is limited to the latter half of the rise run operation, at least during the time when the lift arm 21 is in the horizontal posture and fully lifted up (in the present embodiment, the lift operation amount of the lift arm 21 is 75% or more). Controls the hydraulic pump maximum input torque, and the controller 5 does not control the hydraulic pump maximum input torque in the first half of the rise run operation. As a result, when the lifting operation of the lift arm 21 is not significantly performed, it is possible to maintain the favorable rising of the engine 3 and improve the acceleration performance.

  Further, in the present embodiment, the controller 5 sets the maximum hydraulic pump only when the actual engine rotation speed Vi detected by the first rotation speed sensor 71 is included in the “medium-speed rotation region Z2” or the “high-speed rotation region Z3”. When the input torque is controlled and the actual engine rotation speed Vi detected by the first rotation speed sensor 71 is included in the “low speed rotation range Z1”, the controller 5 does not control the hydraulic pump maximum input torque. In the "low-speed rotation region Z1", the input torque of the hydraulic pump 43 (see characteristic lines A and B shown in FIG. 8) can be limited to a small value regardless of whether or not the lift arm 21 makes a large raising operation. This is because it is desirable to attach importance to the suppression of the deterioration of the rising of No. 3.

  Further, in the present embodiment, when the speed stage is not the “low speed stage” (in the present embodiment, “2 speed stage” shown in FIG. 5) in step S505 (step S504 / NO), the hydraulic pump maximum input torque Is set to NBmax. For example, when the speed stage is not the “low speed stage”, there is a predetermined speed stage selected in the excavation work (“1 speed stage” shown in FIG. 5 in the present embodiment). If selected, it is desirable not to control the hydraulic pump maximum input torque. If the controller 5 sets (changes) the maximum input torque of the hydraulic pump to NAmax during excavation work, of the pressure oil discharged from the hydraulic pump 43, the pressure oil that is throttled down by the spool of the control valve 64 is discarded. This is because the flow rate increases and the fuel consumption increases.

  In the present embodiment, the characteristic line A1 (when the depression amount is shallow), the characteristic line A2 (when the depression amount is medium), and the characteristic line A3 (the depression amount is large) according to the depression amount of the accelerator pedal 61. Case) is set (see FIG. 8), and the controller 5 controls the hydraulic pump maximum input torque based on each characteristic line. Therefore, even when the depression amount of the accelerator pedal 61 is shallow or medium, the discharge flow rate Q2 of the hydraulic pump 43 during the rise run operation is higher than the discharge flow rate Q1 of the hydraulic pump 43 during the operation other than the rise run operation. growing. As a result, even when the depression amount of the accelerator pedal 61 is shallow or medium, the rising speed of the lift arm 21 can be increased as in the case where the depression amount is large.

  The embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are included. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of this embodiment can be replaced with the configuration of another embodiment, and the configuration of this embodiment can be added to the configuration of another embodiment. Furthermore, it is possible to add / delete / replace other configurations with respect to a part of the configurations of the present embodiment.

  For example, in the above-described embodiment, whether or not the lift arm 21 is in the raising operation is determined based on the pilot pressure Pi detected by the manipulated variable detector 74. However, the present invention is not limited to this, and the pressure detector 73 is used. Based on the detected discharge pressure Pa of the hydraulic pump 43, it may be determined whether or not the lift arm 21 is in the raising operation.

  Further, in the above embodiment, the wheel loader 1 is equipped with the torque converter type traveling drive system, but the present invention is not limited to this, and the HST type traveling drive system, the HMT type traveling drive system, and the EMT type traveling drive system are incorporated. It may be a wheel loader. That is, there is no particular limitation on the method of the traveling drive system of the wheel loader 1.

  Further, the setting of the hydraulic pump maximum input torque by the setting unit 54 may be made such that the operator can arbitrarily adjust the set value by an adjusting device or the like provided in the operator's cab 12. As a result, the control of the maximum input torque of the hydraulic pump can be arbitrarily adjusted according to the operator's preference, the environment of the site, etc., and the convenience is improved.

1: Wheel loader 2: Front working machine 3: Engine 5: Controller 21: Lift arm 43: Hydraulic pump 62: Forward / backward changeover switch (running state detector)
73: manipulated variable detector (motion detector)
74: Pressure detector (motion detector)
100B: dump truck 610: stepping amount detector (running state detector)
Z1: Low speed rotation area Z2: Medium speed rotation area Z3: High speed rotation area

Claims (5)

A wheel loader provided with a front working machine having a lift arm which is provided at a front portion of a vehicle body and is rotatable in a vertical direction,
Engine,
A variable displacement hydraulic pump driven by the engine to supply hydraulic oil to the front working machine,
A running state detector for detecting the running state of the vehicle body,
A motion detector for detecting a lifting motion of the lift arm,
A controller that controls the maximum input torque of the hydraulic pump with respect to the actual rotation speed of the engine,
The controller is
Based on the traveling state detected by the traveling state detector and the state of the lifting operation of the lift arm detected by the operation detector, an upward movement of the lift arm during forward traveling of the vehicle body is performed. Judge whether or not the specified specific conditions are met,
When the specific condition is satisfied, the maximum input torque of the hydraulic pump with respect to the actual rotation speed of the engine is changed to a value larger than the maximum input torque when the specific condition is not satisfied. . The wheel loader according to claim 1,
In the controller, the ratio of the displacement volume of the hydraulic pump when the specific condition is satisfied and the displacement volume of the hydraulic pump when the specific condition is not satisfied is the actual rotation speed of the engine when the specific condition is satisfied. And the maximum input torque of the hydraulic pump with respect to the actual rotation speed of the engine is controlled to be equal to or higher than the ratio of the actual rotation speed of the engine when the specific condition is not satisfied. The wheel loader according to claim 1,
The wheel loader, wherein the controller controls the maximum input torque of the hydraulic pump with respect to the actual rotation speed of the engine only while the lift arm is in a horizontal posture and is fully lifted upward. The wheel loader according to claim 1,
The controller stores the range of the actual rotation speed of the engine by dividing it into three rotation speed regions of a low-speed rotation region, a medium-speed rotation region, and a high-speed rotation region. A wheel loader that controls the maximum input torque of the hydraulic pump with respect to the actual rotation speed of the engine only when included in the high speed rotation range or the high speed rotation range. The wheel loader according to claim 1,
The controller controls the maximum input torque of the hydraulic pump with respect to the actual rotation speed of the engine only in the case of the low speed stage selected when traveling toward the dump truck in the loading work. Wheel loader.

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