Operating machinery

Abstract

The present invention provides a working machine capable of achieving both low fuel consumption and ensuring workability. When the speed detected by the speed sensor is a first speed (S11: yes) and the output of the engine or the hydraulic pump increases to a rising threshold value (S12: yes), the working machine increases the speed of the engine from the first speed to a second speed higher than the first speed (S13), and in the process of increasing the speed of the engine to the second speed, outputs a signal indicating a decrease in the discharge capacity of the hydraulic pump to a regulator so that the output of the engine or the hydraulic pump is constant (S14), and when the speed detected by the speed sensor reaches the second speed, outputs a signal indicating an increase in the discharge capacity of the hydraulic pump to the regulator so that the output of the engine or the hydraulic pump becomes a value corresponding to the required load (S16).

Description

Technical Field

[0001] The present invention relates to a working machine including a variable capacity hydraulic pump. Background Art

[0002] Conventionally, there is known a working machine including an engine, a variable capacity hydraulic pump that discharges hydraulic oil using the driving force of the engine, a regulator that changes the discharge capacity of the hydraulic pump, and a hydraulic actuator that operates using the hydraulic oil discharged from the hydraulic pump.

[0003] In the working machinery of the above structure, there is the following technology: when the hydraulic actuator is operated at a low load, the speed is reduced and the engine is driven at a high torque, and when the hydraulic actuator is operated at a high load, the engine speed is increased, thereby achieving both improved fuel consumption and high output (for example, refer to Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-120426 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Here, in order to increase the engine speed in response to the high load, in addition to the torque corresponding to the increased load, a transient torque corresponding to the inertia force of the rotating body (engine and hydraulic pump) is also required. Therefore, in the technology of Patent Document 1, there is a problem that it takes time to increase the engine speed, which reduces the workability.

[0009] The present invention has been made in view of the above-mentioned actual situation, and an object of the present invention is to provide a technology for achieving both low fuel consumption and ensuring workability in a working machine that switches the engine speed according to the load of a hydraulic actuator.

[0010] Means for solving problems

[0011] In order to achieve the above object, the working machine of the present invention comprises: an engine; a variable capacity hydraulic pump that discharges hydraulic oil by the driving force of the engine; a regulator that changes the discharge capacity of the hydraulic pump; a hydraulic actuator that operates by using the hydraulic oil discharged from the hydraulic pump; a rotation speed sensor that detects the rotation speed of the engine; and a controller that controls the rotation speed of the engine and the discharge capacity of the hydraulic pump, wherein the controller increases the rotation speed of the engine from the first rotation speed to a second rotation speed higher than the first rotation speed when the rotation speed detected by the rotation speed sensor is a first rotation speed and the output of the engine or the hydraulic pump increases to a rising threshold value, and outputs a signal instructing a decrease in the discharge capacity of the hydraulic pump to the regulator in the process of increasing the rotation speed of the engine to the second rotation speed so that the output of the engine or the hydraulic pump is constant, and outputs a signal instructing an increase in the discharge capacity of the hydraulic pump to the regulator when the rotation speed detected by the rotation speed sensor reaches the second rotation speed so that the output of the engine or the hydraulic pump becomes a value corresponding to the required load.

[0012] Effects of the Invention

[0013] According to the present invention, in a working machine that switches the engine speed according to the load of the hydraulic actuator, it is possible to achieve both low fuel consumption and ensuring workability. In addition, other problems, structures and effects than those described above will become clear through the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a side view of a hydraulic excavator.

[0015] Figure 2 This is a diagram showing a drive circuit of a hydraulic excavator.

[0016] Figure 3 It is the hardware structure diagram of the hydraulic excavator.

[0017] Figure 4 This is a diagram showing the relationship between the engine speed and torque.

[0018] Figure 5 This is a flow chart of the speed control process.

[0019] Fig. 6A It is a diagram showing the relationship between the fuel injection amount and the engine torque.

[0020] Figure 6B This is a diagram showing the relationship between the operation amount of the boom operating lever and the pump flow rate.

[0021] Figure 6C This is a diagram showing the relationship between pump output and engine torque.

[0022] Fig. 7A : is a graph showing the time change of the engine speed in the speed control process.

[0023] Figure 7B : is a diagram showing the time change of the engine torque in the rotation speed control process.

[0024] Figure 7C : is a graph which shows the time change of the engine output in the rotation speed control process.

[0025] Figure 8 1 is a diagram showing the relationship between the curves W1 and W2 corresponding to a plurality of operation modes of the hydraulic excavator. DETAILED DESCRIPTION

[0026] The embodiment of the hydraulic excavator 1 (working machine) of the present invention is described using the accompanying drawings. In addition, the specific example of the working machine is not limited to the hydraulic excavator 1, and may also be a wheel loader, a crane, a dump truck, etc. In addition, the front, back, left, and right in this specification are based on the viewpoint of the operator who rides on the hydraulic excavator 1 and operates it unless otherwise specified.

[0027] Figure 1 is a side view of the hydraulic excavator 1. Figure 1 As shown, the hydraulic excavator 1 includes a lower traveling structure 2 and an upper revolving structure 3 supported by the lower traveling structure 2. The lower traveling structure 2 and the upper revolving structure 3 are examples of a vehicle body.

[0028] The lower travel body 2 includes a pair of left and right crawler tracks 8 as endless tracks. The pair of left and right crawler tracks 8 are independently rotated by the driving of a travel motor (not shown). As a result, the hydraulic excavator 1 travels. However, the lower travel body 2 may be wheeled instead of the crawler tracks 8.

[0029] The upper rotating body 3 is supported on the lower traveling body 2 in a manner that allows it to rotate by a rotating electric motor (not shown). The upper rotating body 3 mainly includes: a rotating frame 5 serving as a base; a front working machine 4 (working device) mounted in the center of the front of the rotating frame 5 so as to be rotatable in the up-down direction; a cab (operating seat) 7 disposed on the left side in front of the rotating frame 5; and a counterweight 6 disposed at the rear of the rotating frame 5.

[0030] The front working machine 4 includes: a boom 4a supported on the upper rotating body 3 in a manner that allows it to rise and fall; an arm 4b supported on the front end of the boom 4a in a manner that allows it to rotate; a bucket 4c supported on the front end of the arm 4b in a manner that allows it to rotate; a boom cylinder 4d that drives the boom 4a; an arm cylinder 4e that drives the arm 4b; and a bucket cylinder 4f that drives the bucket 4c. The counterweight 6 is used to achieve weight balance with the front working machine 4 and is a heavy object that is in the shape of an arc when viewed from above.

[0031] An internal space in which an operator who operates the hydraulic excavator 1 sits is formed in the cab 7. In addition, a seat in which the operator sits and an operating device operated by the operator sitting on the seat are arranged in the internal space of the cab 7.

[0032] The operating device receives an operation from an operator to operate the hydraulic excavator 1. When the operator operates the operating device, the lower travel body 2 travels, the upper rotating body 3 rotates, and the front working device 4 operates. In addition, as specific examples of the operating device, a lever, a steering wheel, an accelerator pedal, a brake pedal, a switch, etc. can be cited. The operating device includes, for example, a boom operating lever 7a (see FIG. 1 ) for operating the boom cylinder 4d. Figure 2 ) and a mode selection switch 7b for switching the operation mode of the hydraulic excavator 1 (see Figure 3 ).

[0033] The boom operating lever 7a is operated (turned down) by the operator to extend and retract the boom cylinder 4d. In more detail, the more the boom operating lever 7a is operated, the more the boom cylinder 4d is extended and retracted. In addition, although not shown in the figure, the operating device also includes an operating part (pedal, rod) for operating the travel motor, the rotation motor, the dipper cylinder 4e and the bucket cylinder respectively.

[0034] The mode selection switch 7b allows the operator to select the energy saving mode, the power mode, and the high power mode as the operation mode of the hydraulic excavator 1. The mode selection switch 7b transmits a mode signal indicating the operation mode selected by the operator to the vehicle body controller 21 (see Figure 3 ) output.

[0035] The energy-saving mode is an action mode that places the greatest emphasis on low fuel consumption among the three action modes. The high-power mode is an action mode that places the greatest emphasis on high output among the three action modes. The power mode is an action mode between the energy-saving mode and the power mode. That is, the fuel consumption is high in the order of energy-saving mode, power mode, and high-power mode, and the output is from high to low in the order of high-power mode, power mode, and energy-saving mode. Moreover, if the high-power mode is set as the first mode, the power mode and the energy-saving mode become the second mode. In addition, if the power mode is set as the first mode, the energy-saving mode becomes the second mode.

[0036] Figure 2 1 is a diagram showing a drive circuit of the hydraulic excavator 1. Figure 2 As shown, the hydraulic excavator 1 mainly includes an engine 10 , a hydraulic oil tank 11 , a hydraulic pump 12 , a pilot pump 13 , and a directional control valve 14 .

[0037] The engine 10 generates a driving force for driving the hydraulic excavator 1. More specifically, the engine 10 mixes air taken in from the outside of the hydraulic excavator 1 with fuel injected from the injector 15 and burns the mixture, thereby rotating the output shaft 16. The rotation speed (rpm) of the engine 10 is detected by the rotation speed sensor 17. The rotation speed sensor 17 transmits a rotation speed signal indicating the detected rotation speed to the engine controller 22 (see Figure 3 ) output.

[0038] The hydraulic oil tank 11 stores hydraulic oil. The hydraulic pump 12 and the pilot pump 13 are connected to the output shaft 16 of the engine 10. The hydraulic pump 12 and the pilot pump 13 discharge the hydraulic oil stored in the hydraulic oil tank 11 by the driving force of the engine 10.

[0039] exist Figure 2 In the figure, only the boom cylinder 4d in the hydraulic actuator is simply illustrated. A directional control valve 14 is provided between the hydraulic pump 12 and the boom cylinder 4d. The hydraulic pump 12 and the boom cylinder 4d and the directional control valve 14 are connected via piping, respectively. When the boom operating lever 7a is in a neutral state, the hydraulic pump 12 is connected to the working oil tank 11 via the directional control valve 14 through piping. The hydraulic pump 12 supplies the working oil stored in the working oil tank 11 to the hydraulic actuator (travel motor, rotation motor, boom cylinder 4d, arm cylinder 4e, bucket cylinder 4f) through the directional control valve 14. The hydraulic pump 12 is a variable capacity type (inclined plate type, inclined axis type) capable of changing the discharge capacity. The discharge capacity of the hydraulic pump 12 is adjusted by the regulator 18 that operates according to the signal output from the vehicle body controller 21. In addition, the discharge pressure of the hydraulic pump 12 is detected by the discharge pressure sensor 19. The discharge pressure sensor 19 outputs a discharge pressure signal indicating the detected discharge pressure to the vehicle body controller 21.

[0040] A boom operating lever 7a is provided between the pilot pump 13 and the directional control valve 14. The pilot pump 13, the directional control valve 14 and the boom operating lever 7a are respectively connected via pilot piping. When the boom operating lever 7a is in a neutral state, the pilot pump 13 is connected to the working oil tank 11 via the boom operating lever 7a through the pilot piping. The pilot pump 13 supplies the working oil stored in the working oil tank 11 to a pair of pilot ports of the directional control valve 14 through the boom operating lever 7a. If the operator operates the boom operating lever 7a to one side (falls over), a pilot pressure is applied to one of the pair of pilot ports. If the operator operates the boom operating lever 7a to the other side (falls over), a pilot pressure is applied to the other of the pair of pilot ports.

[0041] The greater the operation amount of the boom operating lever 7a, the higher the pilot pressure applied to the pilot port. The pilot pressure applied to the pilot port is detected by the pilot pressure sensor 7c. The pilot pressure sensor 7c outputs a pilot pressure signal indicating the detected pilot pressure to the vehicle body controller 21.

[0042] The direction control valve 14 supplies the hydraulic oil discharged from the hydraulic pump 12 to the bottom chamber or the rod chamber of the boom cylinder 4d. In addition, the direction control valve 14 controls the supply direction and supply amount of the hydraulic oil to the boom cylinder 4d according to the pilot pressure applied to the pilot port.

[0043] In more detail, the directional control valve 14 supplies working oil to the bottom chamber of the boom cylinder 4d by applying a pilot pressure to one pilot port, so that the working oil in the piston rod chamber flows back to the working oil tank 11. As a result, the boom cylinder 4d extends. On the other hand, the directional control valve 14 supplies working oil to the piston rod chamber of the boom cylinder 4d by applying a pilot pressure to the other pilot port, so that the working oil in the bottom chamber flows back to the working oil tank 11. As a result, the boom cylinder 4d contracts. In addition, the higher the pilot pressure applied to the pilot port, the more the directional control valve 14 increases the supply amount of working oil to the boom cylinder 4d.

[0044] Figure 3 1 is a hardware structure diagram of a hydraulic excavator 1. Figure 3 As shown, the hydraulic excavator 1 includes a vehicle controller 21 for controlling the entire hydraulic excavator 1 and an engine controller 22 for controlling the operation of the engine 10. In addition, the vehicle controller 21 and the engine controller 22 described below are just examples of sharing the roles, so they are sometimes collectively referred to as "controller 20" in this specification.

[0045] The vehicle body controller 21 obtains the mode signal output from the mode selection switch 7b, the pilot pressure signal output from the pilot pressure sensor 7c, the discharge pressure signal output from the discharge pressure sensor 19, and the speed signal output from the engine controller 22. Then, the vehicle body controller 21 outputs a signal instructing adjustment (increase or decrease) of the discharge capacity of the hydraulic pump 12 to the regulator 18, and notifies the target speed of the engine 10 to the engine controller 22.

[0046] The engine controller 22 obtains the rotation speed signal output from the rotation speed sensor 17 and obtains the target rotation speed of the engine 10 from the vehicle body controller 21. Then, the engine controller 22 outputs the rotation speed signal obtained from the rotation speed sensor 17 to the vehicle body controller 21, and controls the injection of fuel from the injector 15 based on the target rotation speed obtained from the vehicle body controller 21.

[0047] The controller 20 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The controller 20 reads out and executes the program code stored in the ROM through the CPU to implement the processing described below. The RAM is used as a work area when the CPU executes the program. The ROM and RAM are examples of memories.

[0048] However, the specific structure of the controller 20 is not limited thereto, and may be realized by hardware such as ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array).

[0049] Figure 4 : is a diagram showing the relationship between the rotation speed and torque of the engine 10. First, Figure 4 The maximum torque Tmax of the engine 10 indicated by the solid line in FIG. 1 varies according to the rotation speed. More specifically, in the low rotation speed region, the maximum torque Tmax gradually increases as the rotation speed increases. On the other hand, after the maximum torque Tmax reaches the highest point, the maximum torque Tmax gradually decreases as the rotation speed increases.

[0050] in addition, Figure 4 The dotted line is an equal fuel consumption line connecting points where the fuel consumption rates of the engine 10 are equal. The fuel consumption rate is an index (g / kWh) indicating the time fuel consumption per unit output of the engine 10. That is, the smaller the value of the fuel consumption rate, the better the fuel consumption. In the engine 10 involved in this embodiment, at each speed, there is a tendency that the greater the torque, the higher the fuel consumption.

[0051] Therefore, the controller 20 of the present embodiment drives the engine 10 using either the first speed N1 or the second speed N2. The first speed N1 is a speed at which the engine 10 can be operated with lower fuel consumption than the second speed N2. The first speed N1 is set to a value higher than the speed corresponding to the highest point of the maximum torque Tmax, for example. On the other hand, the second speed N2 is a speed at which an output W higher than the first speed N1 can be generated. In addition, the second speed N2 is a value higher than the first speed N1. The second speed N2 is set to the rated speed of the engine 10, for example.

[0052] That is, the controller 20 sets the target speed of the engine 10 to the first speed N1 while the hydraulic actuator is operating at a low load, and operates the hydraulic excavator 1 with low fuel consumption. On the other hand, when the load of the hydraulic actuator increases, the controller 20 increases the target speed of the engine 10 from the first speed N1 to the second speed N2, and generates a high output.

[0053] in addition, Figure 4 The curves W1 and W2 are equal output lines connecting points where the output of the engine 10 is equal. In addition, the second output value W2 is set to be higher than the first output value W1. In this way, in order to keep the output of the engine 10 constant, it is necessary to reduce the torque of the engine 10 as the speed of the engine 10 increases. On the other hand, the curve W1' is an output line in which the output of the engine 10 gradually increases as the speed increases. Moreover, the curves W1, W1', and W2 are stored in the memory as functions of the speed and torque.

[0054] The torque of the engine 10 can be controlled, for example, by the discharge capacity of the hydraulic pump 12. More specifically, if the discharge capacity of the hydraulic pump 12 is increased, the torque of the engine 10 is also increased. On the other hand, when the discharge capacity of the hydraulic pump 12 is reduced, the torque of the engine 10 is also reduced. That is, the controller 20 outputs a signal indicating a reduction in the discharge capacity of the hydraulic pump 12 to the regulator 18 as the speed of the engine 10 increases, thereby being able to switch the speed while keeping the output of the engine 10 constant.

[0055] Next, refer to Figure 5 to Figure 7C , a process of controlling the rotation speed of the engine 10 and the discharge capacity of the hydraulic pump 12 will be described. Figure 5 This is a flow chart of the speed control process. Figure 6A to Figure 6C 1 is a diagram for explaining a method of calculating the output W of the engine 10 . Figure 7A to Figure 7C 1 is a diagram showing time changes in the rotation speed (A), torque (B), and output (C) of the engine 10 during the rotation speed control process.

[0056] First, the controller 20 determines the speed of the engine 10 detected by the speed sensor 17 (S11). Then, when the controller 20 determines that the speed of the engine 10 is the first speed N1 (S11: Yes), it executes the processing of steps S12 to S16. Here, the output of the engine 10 is increased from 10 to 110 as the load of the hydraulic actuator increases. Figure 3 The processing of increasing the point a0 to the point c. In addition, as a method of calculating the output W of the engine 10, for example, the following three methods can be considered.

[0057] As an example, the output W of the engine 10 is represented by the product of the rotation speed and the torque of the engine 10. Fig. 6AAs shown, the torque of the engine 10 has a positive correlation (more specifically, a proportional relationship) with the fuel injection amount of the injector 15. Fig. 6A The controller 20 can calculate the output W of the engine 10 by multiplying the rotation speed of the engine 10 detected by the rotation speed sensor 17 and the torque corresponding to the fuel injection amount of the injector 15 controlled by the engine controller 22.

[0058] As another example, the output W of the engine 10 is represented by the product of the output of the hydraulic pump 12 and the pump efficiency of the hydraulic pump 12. In addition, the output of the hydraulic pump 12 is represented by the product of the discharge pressure of the hydraulic pump 12 and the flow rate of the hydraulic oil discharged from the hydraulic pump 12. Figure 6B As shown, the flow rate of the hydraulic oil discharged from the hydraulic pump 12 has a positive correlation (more specifically, a proportional relationship) with the operation amount of the boom operating lever 7a (in other words, the pilot pressure detected by the pilot pressure sensor 7c). Figure 6B The controller 20 can calculate the output W of the engine 10 by multiplying the discharge pressure detected by the discharge pressure sensor 19, the flow rate corresponding to the pilot pressure detected by the pilot pressure sensor 7c, and a preset pump efficiency.

[0059] In addition, as another example, Figure 6C As shown, the torque of the engine 10 has a positive correlation (more specifically, a proportional relationship) with the output of the hydraulic pump 12. Figure 6B The relationship is pre-stored in the memory. The controller 20 calculates the output of the hydraulic pump 12 by multiplying the discharge pressure detected by the discharge pressure sensor 19 and the flow rate corresponding to the pilot pressure detected by the pilot pressure sensor 7c. In addition, the controller 20 can calculate the output W of the engine 10 by multiplying the rotation speed of the engine 10 detected by the rotation speed sensor 17 and the torque of the engine 10 corresponding to the output of the hydraulic pump 12.

[0060] The controller 20 compares the output W of the engine 10 with a predetermined rising threshold value W. th1 The controller 20 compares the output W of the engine 10 with the rising threshold value W. th1 Before (S12: No), a signal instructing an increase in the discharge capacity of the hydraulic pump 12 is output to the regulator 18 while the rotation speed of the engine 10 is maintained at the first rotation speed N1. Figure 7A to Figure 7C As shown in the time period from t0 to t1, while the rotation speed of the engine 10 is maintained at the first rotation speed, the torque and output of the engine 10 increase.

[0061] Rising threshold W th1The increase threshold value W represents the output of the engine 10 when the rotation speed of the engine 10 is increased from the first rotation speed N1 to the second rotation speed N2. th1 That is, the controller 20 limits the upper limit of the output of the engine 10 to the rising threshold value W while the engine 10 is rotating at the first speed N1. th1 .

[0062] Next, the controller 20 Figure 7C At time t1, when the output W of the engine 10 increases to the rising threshold value W th1 , the speed of the engine 10 is increased (S13), and a signal indicating a decrease in the discharge capacity of the hydraulic pump 12 is output to the regulator 18 (S14). Then, the controller 20 repeats the processing of steps S13 to S14 until the speed detected by the speed sensor 17 reaches the second speed N2 (S15: No).

[0063] Here, the controller 20 sets the lower limit value of the output of the engine 10 to the first output value W1 while increasing the rotation speed of the engine 10 from the first rotation speed N1 to the second rotation speed N2. The first output value W1 is equal to the increase threshold value W1. th1 That is, the controller 20 outputs a signal instructing the regulator 18 to reduce the discharge capacity of the hydraulic pump 12 in order to make the output of the engine 10 constant while increasing the rotation speed of the engine 10 to the second rotation speed N2.

[0064] For example, the controller 20 increases the speed and reduces the discharge capacity along the curve W1 in the repeatedly executed steps S13 to S14. In other words, the controller 20 outputs a signal to the regulator 18 to instruct the reduction of the discharge capacity of the hydraulic pump 12 in the process of increasing the speed of the engine 10 to the second speed N2 so that the output of the engine 10 is consistent with the first output value W1. Figure 7C As shown between the times t1 and t2 of the solid line, the torque gradually decreases as the rotation speed increases so as to be maintained at the first output value W1.

[0065] Next, when the speed detected by the speed sensor 17 reaches the second speed N2 (S15: Yes), the controller 20 outputs a signal to the regulator 18 to instruct the increase of the discharge capacity of the hydraulic pump 12 while maintaining the speed of the engine 10 at the second speed N2 (S16). Figure 7C As after time t2 indicated by the solid line, the torque is increased so that the output of the engine 10 reaches the second output value W2 while the rotation speed is maintained at the second rotation speed N2.

[0066] In addition, the target output of step S16 varies according to the required load of the engine 10 and is set to an arbitrary value below the second output value W2. The required load refers to the target value required by the operator through the boom operating lever 7a (that is, the load corresponding to the operation amount of the boom operating lever 7a). That is, in step S16, the controller 20 outputs a signal to the regulator 18 to instruct the adjustment of the discharge capacity of the hydraulic pump 12 with the second output value W2 as the upper limit so that the output W of the engine 10 becomes a value corresponding to the required load.

[0067] On the other hand, when the controller 20 determines that the rotation speed of the engine 10 is the second rotation speed N2 (S11: No), the controller 20 executes the processing of steps S17 to S20. Here, the output of the engine 10 is reduced from 0.01 to 0.06 as the load of the hydraulic actuator is reduced. Figure 3 The point c is reduced to the point a0.

[0068] The controller 20 compares the output W of the engine 10 with a predetermined decreasing threshold value W. th2 The controller 20 compares the output W of the engine 10 with the decrease threshold value W. th2 Previously ( S17 : NO), a signal instructing a decrease in the discharge capacity of the hydraulic pump 12 is output to the regulator 18 while the rotation speed of the engine 10 is maintained at the second rotation speed N2 .

[0069] Next, the controller 20 reduces the output W of the engine 10 to the falling threshold value W. th2 : In the case of a load drop (S17: Yes), the speed of the engine 10 is reduced (S18), and a signal indicating adjustment of the discharge capacity of the hydraulic pump 12 is output to the regulator 18 (S19). Then, the controller 20 repeatedly performs the processing of steps S18 to S19 until the speed detected by the speed sensor 17 reaches the first speed N1 (S20: No). In more detail, in the repeatedly executed steps S18 to S19, the controller 20 outputs a signal indicating adjustment of the discharge capacity of the hydraulic pump 12 to the regulator 18 while reducing the speed of the engine 10 to the first speed N1, so that the output W of the engine 10 becomes a value corresponding to the required load. In addition, the change in the output W of the engine 10 during the process of reducing the speed of the engine 10 is different from the change in the output W of the engine 10 during the process of increasing the speed of the engine 10 (i.e., Figure 4 The curve W1) is different.

[0070] Falling threshold W th2 The output of the engine 10 when the rotation speed of the engine 10 is reduced from the second rotation speed N2 to the first rotation speed N1 is shown. th2That is, the controller 20 limits the output of the engine 10 from the second output value W2 (upper limit value) to the decreasing threshold value W1 while the engine 10 is rotating at the second speed N2. th2 (lower limit).

[0071] In addition, the above-mentioned speed control process is commonly applied to the energy-saving mode, the power mode, and the high-power mode. That is, the above description is a process in a state where the action mode of the hydraulic excavator 1 is fixed. On the other hand, in the energy-saving mode, the power mode, and the high-power mode, the first output value W1 and the second output value W2 are different. Figure 8 1 is a diagram showing the relationship between the curves W1 and W2 corresponding to the plurality of operation modes of the hydraulic excavator 1 .

[0072] like Figure 8 As shown, the first output value W1 is set to be a value from high to low in the order of energy saving mode, power mode and high power mode (W1 E >W1 P >W1 HP ). Along with this, the rising threshold W th1 The second output value W2 is set to be a value in the order of energy saving mode, power mode and high power mode from high to low. On the other hand, the second output value W2 is set to be a value in the order of energy saving mode, power mode and high power mode from low to high (W2 E <W2 P <W2 HP ). However, the second output value W2 may also be set to the same value in the energy saving mode, the power mode, and the high power mode.

[0073] According to the above embodiment, the hydraulic excavator 1 can be operated with low fuel consumption by maintaining the engine 10 at the first speed N1 while the load on the hydraulic actuator is small. In addition, when the load on the hydraulic actuator increases, the output of the engine 10 can be increased in accordance with the load on the hydraulic actuator by increasing the speed of the engine 10 from the first speed N1 to the second speed N2.

[0074] Here, in the process of increasing the speed of the engine 10 to the second speed N2, by reducing the discharge capacity of the hydraulic pump 12 (in other words, the torque of the engine 10), the speed of the engine 10 can be quickly brought to the second speed N2. As a result, the time during which the extension and retraction speed of the boom cylinder 4d does not follow the operation amount of the boom operating lever 7a can be shortened. Moreover, in the process of increasing the speed of the engine 10 to the second speed N2, by making the output of the engine 10 greater than the first output value W1, it is possible to prevent the operability from being significantly reduced. As a result, it is possible to achieve both low fuel consumption and ensuring operability.

[0075] In addition, in step S11, the rising threshold W th1 The output to be compared is not limited to the output of the engine 10, but may be the output of the hydraulic pump 12. In step S17, the output of the hydraulic pump 12 is compared with the decreasing threshold value W. th2 The objects for comparison are also the same. Furthermore, the controller 20 may also reduce the discharge capacity of the hydraulic pump 12 in step S14 so that the output of the hydraulic pump 12 matches the first output value. The output of the hydraulic pump 12 can be adjusted by using Figure 6B Explain the method to calculate.

[0076] In addition, in the process of increasing the speed of the engine 10 to the second speed N2, the output of the engine 10 may not be consistent with the first output value W1. As another example, the controller 20 may also repeat the steps S13 to S14 along the Figure 3 In other words, the controller 20 outputs a signal to the regulator 18 to instruct the reduction of the discharge capacity of the hydraulic pump 12 in such a manner that the higher the speed of the engine 10, the higher the output of the engine 10.

[0077] Therefore, if Figure 7C As shown in the dashed line between time t1 and t3, the torque gradually decreases as the speed increases, so that the output of the engine 10 gradually increases. Figure 7B The torque shown by the dashed line decreases more gradually than the torque shown by the solid line. Fig. 7A In FIG. 1 , the time from the first rotation speed N1 to the second rotation speed N2 is longer in the dashed line ( t1 to t3 ) than in the solid line ( t1 to t2 ).

[0078] That is, according to Figure 7A to Figure 7C The dotted line control, and according to Figure 7A to Figure 7C Compared with the control of the solid line, the time during which the extension and retraction speed of the boom cylinder 4d does not follow the operation amount of the boom operating lever 7a becomes longer, while the decrease in operability before the rotation speed of the engine 10 reaches the second rotation speed N2 can be suppressed.

[0079] In addition, according to the above embodiment, the rising threshold W th1 Set it to the same value as the first output value W1, and set the falling threshold value W th2 The value is set to be smaller than the first output value W1. Thus, it is possible to prevent the rotation speed of the engine 10 from being repeatedly switched (so-called hunting) due to fluctuations in the rotation speed of the engine 10 detected by the rotation speed sensor 17.

[0080] Furthermore, according to the above embodiment, the first output value W1, the second output value W2 and the rising threshold value W in the energy saving mode, the power mode and the high power mode are th1Set to use Figure 8 Thus, in the energy-saving mode, the rotation speed of the engine 10 is easily maintained at the first rotation speed N1, so that the hydraulic excavator 1 can be operated with low fuel consumption. On the other hand, in the high-power mode, the rotation speed of the engine 10 is easily switched to the second rotation speed N2, so that the high load of the hydraulic actuator can be handled.

[0081] The above-mentioned embodiments are examples for explaining the present invention, and are not intended to limit the scope of the present invention to these embodiments. A person skilled in the art can implement the present invention in various other forms without departing from the gist of the present invention.

[0082] Description of Reference Numerals

[0083] 1Hydraulic Excavator

[0084] 2 Lower running body

[0085] 3 Upper rotating body

[0086] 4Front working machine

[0087] 4a Boom

[0088] 4b Stick

[0089] 4c Bucket

[0090] 4d boom cylinder

[0091] 4e Stick Cylinder

[0092] 4f Bucket cylinder

[0093] 5 Rotating frame

[0094] 6 Counterweight

[0095] 7 Cab

[0096] 7a Boom operating lever

[0097] 7b Mode selector switch

[0098] 7c Pilot pressure sensor

[0099] 8 Tracks

[0100] 10 Engine

[0101] 11 Working oil tank

[0102] 12 Hydraulic pump

[0103] 13 pilot pump

[0104] 14 Directional control valve

[0105] 15 Injector

[0106] 16 Output shaft

[0107] 17 Speed ​​sensor

[0108] 18 Regulator

[0109] 19 Exhaust pressure sensor

[0110] 20 Controllers

[0111] 21 Car body controller

[0112] 22 Engine controller.

Claims

1. A working machine, comprising: an engine, a variable capacity hydraulic pump that discharges working oil by the driving force of the engine; a regulator that changes the discharge capacity of the hydraulic pump; a hydraulic actuator that is actuated by the working oil discharged from the hydraulic pump; a rotation speed sensor that detects the rotation speed of the engine; and a controller that controls the rotation speed of the engine and the discharge capacity of the hydraulic pump, characterized in that: The controller performs the following actions: In a state where the speed detected by the speed sensor is a first speed and the output of the engine or the hydraulic pump has increased to a rising threshold value, the speed of the engine is increased from the first speed to a second speed higher than the first speed, and in the process of increasing the speed of the engine to the second speed, a signal instructing a reduction in the discharge capacity of the hydraulic pump is output to the regulator so that the output of the engine or the hydraulic pump is constant, When the rotation speed detected by the rotation speed sensor reaches the second rotation speed, a signal instructing an increase in the discharge capacity of the hydraulic pump is output to the regulator so that the output of the engine or the hydraulic pump becomes a value corresponding to the required load.

2. The working machine according to claim 1, characterized in that: The controller outputs a signal instructing the regulator to reduce a discharge capacity of the hydraulic pump so that the output of the engine or the hydraulic pump matches the increase threshold value while increasing the rotation speed of the engine to the second rotation speed.

3. The working machine according to claim 1, characterized in that: The controller reduces the speed of the engine from the second speed to the first speed when the speed detected by the speed sensor is the second speed and the output of the engine or the hydraulic pump has dropped to a reduction threshold value, and in the process of reducing the speed of the engine to the first speed, outputs a signal to the regulator instructing adjustment of the discharge capacity of the hydraulic pump so that the output of the engine or the hydraulic pump becomes a value corresponding to the required load.

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