Hydraulic drive system

Abstract

This invention provides a hydraulic drive system that can be calibrated even without installing special components. The hydraulic drive system includes: a directional control valve disposed in a supply line from a hydraulic pump to a hydraulic actuator, controlling the direction of the supply of working oil to the hydraulic actuator; a flow control valve disposed upstream of the flow of working oil from the directional control valve in the supply line, controlling the flow rate of working oil supplied from the hydraulic pump to the directional control valve; a solenoid valve for opening and closing the flow control valve; and a controller for performing a calibration process that regulates the command current output to the solenoid valve. During the calibration process, with the flow control valve closed and the directional control valve open, the controller shifts the command current output to the solenoid valve in the direction that opens the flow control valve, and determines the command current at the time point of pressure change detected by a pressure sensor as the opening current at which the flow control valve begins to open.

Description

Technical Field

[0001] This invention relates to a hydraulic drive system for driving hydraulic actuators. Background Technology

[0002] Previously, hydraulic drive systems were installed in hydraulic excavators, dump trucks, wheel loaders and other operating machinery. These hydraulic drive systems consisted of hydraulic actuators, hydraulic pumps that sprayed working oil, and multiple valves that controlled the supply direction and amount of working oil sprayed from the hydraulic pump.

[0003] As an example of such a hydraulic drive system, Patent Document 1 discloses a structure comprising a directional control valve configured in a supply line from a hydraulic pump to a hydraulic actuator to control the supply direction of working oil to the hydraulic actuator; a flow control valve configured upstream of the flow of working oil from the directional control valve in the supply line to control the flow rate of working oil supplied from the hydraulic pump to the directional control valve; and a solenoid valve for opening and closing the flow control valve.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 7193446 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the hydraulic drive system described above, the opening of the flow control valve relative to the command current output to the solenoid valve may deviate due to manufacturing errors or other reasons. Therefore, calibration is required to adjust the magnitude of the command current and the opening of the flow control valve.

[0009] As one example, consider installing a pressure sensor on the output side of a solenoid valve to measure the pilot pressure output characteristics. However, when the solenoid valve is integrated with a flow control valve, installing a pressure sensor on the output side of the solenoid valve is inherently difficult. Another example is considering measuring the pressure between a flow control valve and a directional control valve for calibration. However, in actual operation of machinery, the necessity of installing a pressure sensor between the flow control valve and the directional control valve is low. Therefore, removing and installing the pressure sensor for each calibration requires a significant amount of time.

[0010] The present invention was made in view of the above-mentioned actual situation, and its purpose is to provide a hydraulic drive system that can be calibrated even without the installation of special components.

[0011] Methods for solving problems

[0012] To achieve the above objectives, the present invention provides a hydraulic drive system comprising: a hydraulic pump that ejects working oil stored in a working oil tank; a hydraulic actuator driven by the working oil ejected from the hydraulic pump; a directional control valve disposed in a supply line from the hydraulic pump to the hydraulic actuator, controlling the direction of the supply of working oil to the hydraulic actuator; a flow control valve disposed upstream of the flow of working oil from the hydraulic pump to the directional control valve in the supply line, controlling the flow rate of working oil supplied from the hydraulic pump to the directional control valve; and a pressure sensor that detects the pressure supplied to the hydraulic actuator. The pressure of the working oil; a solenoid valve that opens and closes the flow control valve by supplying pilot pressure to the pilot port of the flow control valve; and a controller that performs a calibration process for adjusting the command current output to the solenoid valve, wherein, in the calibration process, the controller, with the flow control valve closed and the directional control valve open, causes the command current output to the solenoid valve to change in the direction that causes the flow control valve to open, and determines the command current at the time point of pressure change detected by the pressure sensor as the opening start current of the flow control valve.

[0013] Invention Effects

[0014] According to the present invention, a hydraulic drive system that can be calibrated even without installing special components can be obtained. Furthermore, issues, structures, and effects other than those described above will become clear through the following description of embodiments. Attached Figure Description

[0015] Figure 1 This is a side view of a hydraulic excavator.

[0016] Figure 2 It is part of the circuit diagram of a hydraulic drive system.

[0017] Figure 3 It is another part of the circuit diagram of the hydraulic drive system.

[0018] Figure 4 This is a cross-sectional view of a flow control valve.

[0019] Figure 5 This is a diagram showing the opening area characteristics of a flow control valve.

[0020] Figure 6 This is the functional block diagram of the controller.

[0021] Figure 7 This is a diagram illustrating the performance error of a solenoid valve.

[0022] Figure 8 This is a flowchart of the calibration process.

[0023] Figure 9This is a graph showing the time variation of the command current and the variation of the load voltage relative to the command current during the calibration process. Detailed Implementation

[0024] [Structure of Hydraulic Excavator 200]

[0025] The embodiments of the hydraulic excavator 200 (operating machinery) of the present invention will be described using the accompanying drawings. However, the specific examples of operating machinery are not limited to the hydraulic excavator 200; all devices equipped with hydraulic actuators, such as wheel loaders, dump trucks, and cranes, are applicable. Furthermore, unless otherwise specified, the terms "front," "back," "left," and "right" in this specification are based on the viewpoint of the operator riding in and operating the hydraulic excavator 200.

[0026] Figure 1 This is a side view of a hydraulic excavator 200. (For example...) Figure 1 As shown, the hydraulic excavator 200 includes a lower traveling body 201 and an upper rotating body 202 supported by the lower traveling body 201. The lower traveling body 201 and the upper rotating body 202 are examples of the machine body.

[0027] The lower traveling body 201 has a pair of tracks 204 on the left and right sides, which serve as an infinite track. Moreover, the pair of tracks 204 rotate independently by the drive motor 205. As a result, the hydraulic excavator 200 travels. However, the lower traveling body 201 can also be wheeled instead of having tracks 204.

[0028] The upper rotating body 202 is supported on the lower traveling body 201 in a manner that allows it to rotate via a rotary motor 206. That is, the upper rotating body 202 rotates relative to the lower traveling body 201 by rotating the rotary motor 206. The upper rotating body 202 mainly includes a rotating frame 207 that serves as a base, a cab (driver's seat) 208 located on the front left side of the rotating frame 207, a counterweight 209 located at the rear of the rotating frame 207, and a front work machine 210 (working device) that is rotatable in the vertical direction and mounted at the front center of the rotating frame 207.

[0029] The cab 208 is configured adjacent to the front work machine 210 in the left-right direction (width direction of the vehicle body). More specifically, the cab 208 is configured to the left of the front work machine 210 (on one side in the left-right direction). However, the configuration of the cab 208 is not limited to the above example; the cab 208 can be configured to one side of the front work machine 210 in the left-right direction.

[0030] The cab 208 provides space for an operator to sit while operating the hydraulic excavator 200. Inside the cab 208 is a seat for the operator and an operating device operated by the operator seated in the seat. The operating device is operated by the operator to move the hydraulic excavator 200. By operating the operating device, the lower traveling body 201 travels, the upper rotating body 202 rotates, and the front workpiece 210 moves. The operating device includes at least... Figure 3 The control levers 115a and 115b are shown. Other specific examples of control devices include levers, steering wheels, pedals, and switches.

[0031] The front workpiece 210 includes: a boom 211 that is undulatingly supported on the upper rotating body 202; a stick 212 that is rotatably (loading and unloading) supported on the front end of the boom 211; a bucket 213 (accessory) that is rotatably (loading and unloading) supported on the front end of the stick 212; a boom cylinder 214 that drives the boom 211; a stick cylinder 215 that drives the stick 212; and a bucket cylinder 216 that drives the bucket 213. Furthermore, specific examples of accessories are not limited to the bucket 213; they can also be grab buckets, cutters, crushers, hydraulic breakers, etc. The counterweight 209, used to achieve weight balance with the front workpiece 210, is a heavy object that appears as an arc when viewed from above.

[0032] The travel motor 205, swivel motor 206, boom cylinder 214, stick cylinder 215, and bucket cylinder 216 are examples of hydraulic actuators. That is, a hydraulic actuator includes one or both of a hydraulic motor that rotates by supplying working oil and a hydraulic cylinder that extends and retracts by supplying and discharging working oil. However, specific examples of hydraulic actuators are not limited to the examples described above.

[0033] [Structure of hydraulic drive system 100]

[0034] Figure 2 It is part of the circuit diagram of the hydraulic drive system 100. Figure 3 This is another part of the circuit diagram of the hydraulic drive system 100. The hydraulic excavator 200 possesses... Figure 2 and Figure 3 The hydraulic drive system 100 is shown. The hydraulic drive system 100 is a system for driving hydraulic actuators (e.g., travel motor 205, swivel motor 206, boom cylinder 214, stick cylinder 215, and bucket cylinder 216).

[0035] like Figure 2As shown, the hydraulic drive system 100 includes three hydraulic pumps 1, 2, and 3, and a working oil tank 4 for storing the working oil discharged from the hydraulic pumps 1-3. The hydraulic pumps 1-3 are driven by an engine (not shown), thereby discharging the working oil stored in the working oil tank 4 toward the hydraulic actuator. Furthermore, the hydraulic pumps 1-3 are variable-capacity hydraulic pumps capable of changing their discharge capacity (e.g., tilt angle). The discharge capacity (tilt angle) of the hydraulic pumps 1-3 is controlled by regulators respectively attached to the hydraulic pumps 1-3. Each regulator for the hydraulic pumps 1-3 includes flow control command pressure ports 1a, 2a, and 3a.

[0036] The hydraulic drive system 100 includes a right-hand travel directional control valve 6, a bucket directional control valve 7, a second stick directional control valve 8, a first boom directional control valve 9, a second boom directional control valve 10, a first stick directional control valve 11, a first accessory directional control valve 12, a left-hand travel directional control valve 13, a slewing directional control valve 14, a third boom directional control valve 15, and a second accessory directional control valve 16. The directional control valves 6-16 are located in the supply lines (oil lines 44-49, 54-59, 65-70) from the hydraulic pumps 1-3 to the hydraulic actuators. Furthermore, the directional control valves 6-16 control the direction of the supply of working oil discharged from the hydraulic pumps 1-3 to their respective hydraulic actuators.

[0037] The hydraulic pump 1's ejection line 41 is connected to the working oil tank 4 via a central bypass line 42. On the central bypass line 42, starting from the upstream side of the working oil flow, there are sequentially arranged a right-side directional control valve 6 for controlling the right-side travel motor 205, a bucket directional control valve 7 for controlling the flow of hydraulic oil supplied to the bucket cylinder 216, a second stick directional control valve 8 for controlling the flow of hydraulic oil supplied to the stick cylinder 215, and a first boom directional control valve 9 for controlling the flow of hydraulic oil supplied to the boom cylinder 214.

[0038] The supply ports of the bucket directional control valve 7, the second stick directional control valve 8, and the first boom directional control valve 9 are respectively connected in parallel via oil lines 44, 45, 46, 47, and 48, 49 to a parallel line 43 branching from the central bypass line 42 connecting the right-hand drive directional control valve 6 and the bucket directional control valve 7. Furthermore, a vent valve 34 is located at the downstream end of the central bypass line 42 to control the flow of hydraulic oil discharged from the central bypass line 42 to the working oil tank 4. Additionally, the discharge line 41 is connected to the working oil tank 4 via an oil line 50 equipped with an overflow valve 31 to protect the circuit from excessive pressure rise.

[0039] The discharge line 51 of the hydraulic pump 2 is connected to the working oil tank 4 via the central bypass line 52. On the central bypass line 52, starting from the upstream side of the working oil flow, there are arranged in sequence: a second boom directional control valve 10 for controlling the flow of hydraulic oil supplied to the boom cylinder 214, a first stick directional control valve 11 for controlling the flow of hydraulic oil supplied to the stick cylinder 215, a first accessory directional control valve 12 for controlling the flow of hydraulic oil supplied to the first actuator shown in the diagram, which drives a first special accessory such as a crusher installed instead of the bucket 213, and a left travel directional control valve 13 for controlling the drive of the left travel motor 205.

[0040] The supply ports of the second boom directional control valve 10, the first stick directional control valve 11, the first accessory directional control valve 12, and the left travel directional control valve 13 are respectively connected in parallel via oil passages 54, 55, 56, 57, 58, 59, and 60 to a parallel pipeline 53 branching from the ejection pipeline 51. Furthermore, a vent valve 35 is located at the downstream end of the central bypass pipeline 52 to control the flow of hydraulic oil discharged from the central bypass pipeline 52 to the working oil tank 4. Additionally, pipelines 41 and 53 are connected via an oil passage 69 equipped with a confluence valve 37, and check valves 38 and 39 are installed on pipelines 41 and 53 to prevent backflow. Moreover, the parallel pipeline 53 is connected to the working oil tank 4 via an oil passage 61 equipped with a relief valve 32 to protect the circuit from excessive pressure rise.

[0041] The discharge line 62 of the hydraulic pump 3 is connected to the working oil tank 4 via a central bypass line 63. On the central bypass line 63, starting from the upstream side of the working oil flow, there are sequentially arranged a rotation directional control valve 14 for controlling the flow of hydraulic oil supplied to the rotary motor 206 driving the upper rotating body 202, a third boom directional control valve 15 for controlling the flow of hydraulic oil supplied to the boom cylinder 214, and a second accessory directional control valve 16. The second accessory directional control valve 16 controls the flow of hydraulic oil supplied to the second actuator when a second special accessory with a second actuator in addition to the first special accessory is installed, or when a second special accessory having both a first actuator and a second actuator is installed instead of the first special actuator.

[0042] The supply ports of the rotation directional control valve 14, the third boom directional control valve 15, and the second accessory directional control valve 16 are respectively connected in parallel to a parallel pipeline 64 branching from the ejection pipeline 62 via oil passages 65, 66, 67, 68, and 69, 70. Furthermore, a relief valve 36 is located at the downstream end of the central bypass pipeline 63 to control the flow of hydraulic oil discharged from the central bypass pipeline 63 to the working oil tank 4. In addition, the parallel pipeline 64 is connected to the working oil tank 4 via an oil passage 71 equipped with a relief valve 33 to protect the circuit from excessive pressure rise.

[0043] Oil lines 44-49, 54-59, and 65-70 are examples of supply lines from hydraulic pumps 1-3 to hydraulic actuators. Relief valves 34, 35, and 36 are examples of opening and closing devices for the central bypass lines 42, 52, and 63 from hydraulic pumps 1-3 to the working oil tank 4 via directional control valves 6-16.

[0044] The hydraulic drive system 100 includes flow control valves 21, 22, 23, 24, 25, 26, 27, 28, and 29. Flow control valves 21 to 29 are positioned upstream of the directional control valves 6 to 16 in the supply lines (oil lines 44 to 49, 54 to 59, 65 to 70) on the side upstream of the flow of working oil. Furthermore, flow control valves 21 to 29 control the flow rate of working oil supplied from hydraulic pumps 1 to 3 to the directional control valves 6 to 16. For details regarding flow control valves 21 to 29, please refer to [link to relevant documentation]. Figure 4 To be discussed later.

[0045] The bucket flow control valve 21 is installed in oil passages 44 and 45 connected to the supply port of the bucket directional control valve 7. The second stick flow control valve 22 is installed in oil passages 46 and 47 connected to the supply port of the second stick directional control valve 8. The first boom flow control valve 23 is installed in oil passages 48 and 49 connected to the supply port of the first boom directional control valve 9.

[0046] The flow control valve 24 for the second boom is installed in oil passages 54 and 55 connected to the supply port of the directional control valve 10 for the second boom. The flow control valve 25 for the first stick is installed in oil passages 56 and 57 connected to the supply port of the directional control valve 11 for the first stick. The flow control valve 26 for the first accessory is installed in oil passages 58 and 59 connected to the supply port of the directional control valve 12 for the first accessory.

[0047] A slewing flow control valve 27 is installed in oil passages 65 and 66 connected to the supply port of the slewing directional control valve 14. A third boom flow control valve 28 is installed in oil passages 67 and 68 connected to the supply port of the third boom directional control valve 15. A second accessory flow control valve 29 is installed in oil passages 69 and 70 connected to the supply port of the second accessory directional control valve 16.

[0048] like Figure 3 As shown, the hydraulic drive system 100 includes a pilot pump 111, a pilot relief valve 112, and a solenoid valve unit 113. The pilot pump 111 is connected to the working oil tank 4 via the pilot relief valve 112 for generating pilot primary pressure. Furthermore, the pilot pump 111 is connected to the solenoid valve unit 113 via an oil passage 121. Moreover, the pilot pump 111 compresses the working oil stored in the working oil tank 4 and outputs pilot pressure to the solenoid valve unit 113.

[0049] The solenoid valve unit 113 includes multiple solenoid valves 113a, 113b, 113c, 113d, and 113e. Solenoid valve 113a is connected to the flow control command pressure port 2a of the regulator of the hydraulic pump 2 via pilot line 123. Solenoid valves 113b and 113c are connected to the command pressure ports 11a and 11b of the first boom directional control valve 11 via pilot lines 124 and 125. Solenoid valve 113d is connected to the command pressure port 25j of the first boom flow control valve 25 via pilot line 126. Solenoid valve 113e is connected to the command pressure port 35a of the relief valve 35 via pilot line 127. Furthermore, solenoid valves 113a to 113e are connected to the working oil tank 4 via oil passage 122.

[0050] Solenoid valve 113d is an electromagnetic proportional valve that adjusts its opening degree according to the command current output from controller 114. Furthermore, solenoid valve 113d, under the control of controller 114, supplies pilot pressure to the command pressure port 25j (pilot port) of the first boom flow control valve 25. More specifically, the larger the command current, the higher the pilot pressure supplied by solenoid valve 113d. This causes the first boom flow control valve 25 to open and close. The other solenoid valves 113a-113c and 113e operate similarly.

[0051] Furthermore, due to the complexity of the explanation, the following solenoid valves are omitted from the diagram: hydraulic pump 1, hydraulic pump 3, right-travel directional control valve 6, bucket directional control valve 7, second boom directional control valve 8, first boom directional control valve 9, second boom directional control valve 10, first accessory directional control valve 12, left-travel directional control valve 13, rotation directional control valve 14, third boom directional control valve 15, second accessory directional control valve 16, bucket flow control valve 21, second boom flow control valve 22, first boom flow control valve 23, second boom flow control valve 24, first accessory flow control valve 26, rotation flow control valve 27, third boom flow control valve 28, second accessory flow control valve 29, vent valve 34, vent valve 36, and confluence valve 37.

[0052] like Figure 2 and Figure 3 As shown, the hydraulic drive system 100 includes pressure sensors 84, 85, 86, 87a, 87b, 88a, 88b, 89a, 89b, 90a, 90b, 133, 134, 135, 136, and 137. Pressure sensors 84–90 and 133–137 detect the pressure of the working oil flowing in the flow path (e.g., injection pressure, actuator pressure, load pressure, flow control command pressure, command pressure) and output a pressure signal representing the detected pressure to the controller 114.

[0053] Pressure sensor 84 detects the discharge pressure of hydraulic pump 1 on discharge line 41. Pressure sensor 85 detects the discharge pressure of hydraulic pump 2 on discharge line 51. Pressure sensor 86 detects the discharge pressure of hydraulic pump 3 on discharge line 62. Pressure sensors 87a and 87b detect actuator pressure on actuator lines 72a and 72b connected to boom cylinder 214. Pressure sensors 88a and 88b detect actuator pressure on actuator lines 73a and 73b connected to stick cylinder 215. Pressure sensors 89a and 89b detect actuator pressure on actuator lines 74a and 74b connected to bucket cylinder 216. Pressure sensors 90a and 90b detect actuator pressure on actuator lines 75a and 75b connected to rotary motor 206. In addition, due to the complexity of the description, illustrations of the left drive motor (not shown), the right drive motor (not shown), and the pressure sensor for detecting the actuator pressure of the accessory (not shown) have been omitted.

[0054] Pressure sensor 133 detects the flow control command pressure output from solenoid valve 113a to flow control command pressure port 2a via pilot line 123. Pressure sensors 134 and 135 detect the command pressure output from solenoid valves 113b and 113c to command pressure ports 11a and 11b via pilot lines 124 and 125, respectively. Pressure sensor 136 detects the command pressure output from solenoid valve 113d to command pressure port 25j via pilot line 126. Pressure sensor 137 detects the command pressure output from solenoid valve 113e to command pressure port 35a via pilot line 127.

[0055] Furthermore, due to the complexity of the description, illustrations of the pressure sensors used to detect the command pressure of the solenoid valves for hydraulic pump 1, hydraulic pump 3, right-travel directional control valve 6, bucket directional control valve 7, second boom directional control valve 8, first boom directional control valve 9, second boom directional control valve 10, first accessory directional control valve 12, left-travel directional control valve 13, rotation directional control valve 14, third boom directional control valve 15, second accessory directional control valve 16, bucket flow control valve 21, second boom flow control valve 22, first boom flow control valve 23, second boom flow control valve 24, first accessory flow control valve 26, rotation flow control valve 27, third boom flow control valve 28, second accessory flow control valve 29, relief valve 34, relief valve 36, and confluence valve 37 are omitted.

[0056] The hydraulic drive system 100 includes temperature sensors 91 and 92. Temperature sensors 91 and 92 detect the temperature of the working oil and output a temperature signal indicating the detected temperature to the controller 114. Temperature sensor 91 detects the temperature of the working oil stored in the working oil tank 4. Temperature sensor 92 detects the temperature of the working oil flowing in the oil passage 121.

[0057] The hydraulic drive system 100 includes posture sensors 222, 223, 224, 225, and 226. Posture sensors 222-226 detect the posture of the hydraulic excavator 200 or the hydraulic actuators and output posture signals representing the detected posture to the controller 114. Posture sensors 222-224 are, for example, stroke sensors that detect the posture (extension) of the boom cylinder 214, stick cylinder 215, and bucket cylinder 216. Posture sensor 225 is, for example, a tilt sensor that detects the posture of the hydraulic excavator 200 (body). Posture sensor 226 is, for example, a rotation angle sensor that detects the rotation angle of the rotary motor 206.

[0058] The hydraulic drive system 100 is equipped with current sensors 143, 144, 145, 146, and 147. The current sensors 143 to 147 detect the magnitude of the command current output from the controller 114 to the solenoid valves 113a to 113e, and output a current signal indicating the magnitude of the detected command current to the controller 114.

[0059] Furthermore, due to the complexity of the description, the diagrams of the current sensors used to detect the control current output by the solenoid valves for the following valves are omitted: hydraulic pump 1 (for opposing direction), hydraulic pump 3 (for hydraulic pump 3), right-travel directional control valve 6 (for hydraulic pump 6), bucket directional control valve 7 (for hydraulic pump 7), second boom directional control valve 8 (for hydraulic pump 8), first boom directional control valve 9 (for hydraulic pump 9), second boom directional control valve 10 (for hydraulic pump 10), first accessory directional control valve 12 (for hydraulic accessory 12), left-travel directional control valve 13 (for hydraulic pump 13), slewing directional control valve 14 (for hydraulic pump 14), third boom directional control valve 15 (for hydraulic pump 15), second accessory directional control valve 16 (for hydraulic accessory 16), bucket flow control valve 21 (for hydraulic pump 22), second boom flow control valve 22 (for hydraulic pump 22), first boom flow control valve 23 (for hydraulic pump 23), second boom flow control valve 24 (for hydraulic pump 24), first accessory flow control valve 26 (for hydraulic accessory 26), slewing flow control valve 27 (for hydraulic pump 27), third boom flow control valve 28 (for hydraulic pump 28), second accessory flow control valve 29 (for hydraulic accessory 29), vent valve 34, vent valve 36, and confluence valve 37.

[0060] The hydraulic drive system 100 includes an operating lever 115a capable of switching between operating the first boom directional control valve 9, the second boom directional control valve 10, and the third boom directional control valve 15, and an operating lever 115b capable of switching between operating the first stick directional control valve 11 and the second stick directional control valve 8. Operating levers 115a and 115b are examples of operating devices. Operating levers 115a and 115b output operating signals indicating the operator's operating direction (tilting direction) and operating amount (tilting amount) to the controller 114.

[0061] In addition, for the sake of simplicity, the diagrams of the right-moving control lever for switching right-moving directional control valve 6, the bucket control lever for switching bucket directional control valve 7, the first accessory control lever for switching first accessory directional control valve 12, the left-moving control lever for switching left-moving directional control valve 13, the rotation control lever for switching rotation directional control valve 14, and the second accessory control lever for switching second accessory directional control valve 16 are omitted.

[0062] The controller 114 includes a CPU (Central Processing Unit) and memory. The memory may consist of, for example, ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), or a combination thereof. The controller 114 uses the CPU to read and execute program code stored in ROM or HDD to perform the processing described later. RAM serves as the working area for the CPU when executing the program.

[0063] However, the specific structure of the controller 114 is not limited to this, and it can also be implemented by hardware such as ASIC (Application Specific Integrated Circuit) and FPGA (Field-Programmable Gate Array).

[0064] The controller 114 is mounted on the hydraulic excavator 200 (body). Furthermore, the controller 114 adjusts (increases or decreases) the command current output to the solenoid valves 113a to 113e included in the solenoid valve unit 113 based on the operation signals output from the operating levers 115a and 115b, the pressure signals output from the pressure sensors 84 to 90 and 133 to 137, the temperature signals output from the temperature sensors 91 and 92, the current signals output from the current sensors 143 to 147, and the attitude signals output from the attitude sensors 221 to 226.

[0065] Solenoid valves 113a-113e (and other solenoid valves not shown) reduce the pilot primary pressure based on the command current output from controller 114 and output it as the command pressure. In this embodiment, the larger the command current output from controller 114, the larger the pilot pressure output through solenoid valves 113a-113e. Conversely, the smaller the command current output from controller 114, the smaller the pilot pressure output through solenoid valves 113a-113e. However, the relationship between command current and pilot pressure is not limited to the example described above.

[0066] The hydraulic drive system 100 includes a calibration indicator 116 (indicator). The calibration indicator 116 handles calibration requests from the operator. Figure 8 The system receives the execution instruction and inputs the received execution instruction to the controller 114. As an example, the calibration instruction device 116 may also be part of the operating device (e.g., a button, an icon displayed on a touch panel display) located inside the cab 208.

[0067] As another example, the calibration indicator 116 can also be configured as a portable device (e.g., tablet terminal, smartphone, feature phone, laptop computer) detachable from the controller 114 (first controller) mounted on the hydraulic excavator 200. Such a portable device includes at least a second controller and a user interface (e.g., display, control panel). The second controller has the same structure as the controller 114. Furthermore, the second controller can instruct the controller 114 to perform calibration processing according to instructions from the operator via the user interface. Moreover, the first and second controllers can share the responsibility of performing the calibration process. Figure 8 The calibration process will be described later.

[0068] [Structure of flow control valve 25]

[0069] Figure 4 This is a cross-sectional view of the flow control valve 25. (Example) Figure 4 As shown, the flow control valve 25 for the first boom mainly comprises a main housing 151, a pilot housing 152, a main lifting valve 153 (main valve), a pilot valve core 154, helical springs 155, 158, and 159, and a ball check valve 156. The main housing 151 and pilot housing 152 are examples of housings. Furthermore, since the flow control valves 21 to 29 have the same structure, the structure of the flow control valve 25 for the first boom will be described below. Additionally, the structures of the flow control valves 21 to 29 mounted on the hydraulic drive system 100 are not limited to... Figure 4 Examples.

[0070] A first pressure chamber 161, a second pressure chamber 173, and a third pressure chamber 166 are formed inside the main housing 151. These three pressure chambers are spaces through which working oil can pass. The first pressure chamber 161 is connected to oil passage 56 (the supply line to the hydraulic pump 2 side). The second pressure chamber 173 is connected to oil passage 57 (the supply line to the first boom directional control valve 11 side). The third pressure chamber 166 is positioned opposite the first pressure chamber 161 in the direction of movement of the main lifting valve 153.

[0071] Pilot pressure chambers 168 and 170, pilot oil passages 167, 171 and 172, and pilot ports 174 and 175 are formed inside the pilot housing 152. The pilot pressure chambers 168 and 170, the pilot oil passages 167, 171 and 172, and the pilot ports 174 and 175 are spaces through which working oil can pass.

[0072] Pilot chambers 168 and 170 house the pilot valve core 154. Pilot oil passage 167 connects the third pressure chamber 166 to pilot chambers 168 and 170. Pilot oil passages 171 and 172 connect pilot chambers 168 and 170 to the second pressure chamber 173. Pilot chambers 168 and 170 and pilot oil passages 167, 171, and 172 are an example of pilot piping. Pilot port 174 connects to the working oil tank 4. Pilot port 175 connects to the oil passage 121 of the pilot pump 111 via solenoid valve 113d.

[0073] The main lift valve 153 moves within the main housing 151 in a direction that connects or blocks the first pressure chamber 161 and the second pressure chamber 173, utilizing the pressure difference between the first pressure chamber 161 and the third pressure chamber 166. More specifically, when the pressure in the first pressure chamber 161 is greater than the pressure in the third pressure chamber 166, the main lift valve 153 moves in a direction that connects the first pressure chamber 161 and the second pressure chamber 173. Conversely, when the pressure in the third pressure chamber 166 is greater than the pressure in the first pressure chamber 161, the main lift valve 153 moves in a direction that blocks the first pressure chamber 161 and the second pressure chamber 173.

[0074] The first pressure chamber 161 and the second pressure chamber 173 are connected via a variable throttling section formed in the main housing 151. Furthermore, the main lift valve 153 is seated in the main housing 151 by means of a helical spring 155 provided in the third pressure chamber 166 (i.e., blocking the first pressure chamber 161 and the second pressure chamber 173). Additionally, the main lift valve 153 always blocks the connection between the second pressure chamber 173 and the third pressure chamber 166. Moreover, the main lift valve 153 connects the first pressure chamber 161 and the third pressure chamber 166 via communication paths 163 and 164 and a control variable throttling section 165.

[0075] Furthermore, the main lift valve 153 has connecting paths 163 and 164 and a control variable throttling section 165. Connecting paths 163 and 164, and the control variable throttling section 165, are spaces through which working oil can pass. Connecting paths 163 and 164 connect the first pressure chamber 161 and the third pressure chamber 166 through the interior of the main lift valve 153. The control variable throttling section 165 is formed at the end of the connecting path 164 on the third pressure chamber 166 side (i.e., at the position facing the third pressure chamber 166 and the inner wall of the main housing 151). The opening area of ​​the control variable throttling section 165 changes in conjunction with the operation of the main lift valve 153. More specifically, the lower the pressure in the third pressure chamber 166, the larger the opening area of ​​the control variable throttling section 165. Conversely, the higher the pressure in the third pressure chamber 166, the smaller the opening area of ​​the control variable throttling section 165.

[0076] A ball-shaped check valve 156 and a coil spring 158 are housed in the connecting path 163. The ball-shaped check valve 156 is forced by the coil spring 158 in the direction of closing the connecting path 163. Moreover, when the pressure in the first pressure chamber 161 is greater than that in the third pressure chamber 166, the ball-shaped check valve 156 opens the connecting path 163. On the other hand, when the pressure in the third pressure chamber 166 is greater than that in the first pressure chamber 161, the ball-shaped check valve 156 closes the connecting path 163.

[0077] Pilot valve spool 154 uses pilot pressure supplied via solenoid valve 113d to open and close pilot chambers 168 and 170 (i.e., pilot lines). More specifically, the higher the pilot pressure supplied to pilot port 175, the smaller the opening of pilot chambers 168 and 170 caused by pilot valve spool 154. Conversely, the lower the pilot pressure supplied to pilot port 175, the larger the opening of pilot chambers 168 and 170 caused by pilot valve spool 154. Furthermore, pilot valve spool 154 is subjected to force by coil spring 159 in the direction that opens between pilot chambers 168 and 170.

[0078] The first pressure chamber 161 and the second pressure chamber 173 are connected via a variable throttling section formed in the main housing 151. Furthermore, the main lift valve 153 is provided with a notch 162 that forms the opening characteristic of the variable throttling section. Additionally, the opening characteristic of the pilot circuit is adjusted by a throttling section provided between the pilot pressure chambers 168 and 170 and a notch 169 provided in the pilot valve core 154. Moreover, the notches 162 and 169 and the control variable throttling section 165 can be combined with various shapes, in addition to the shapes shown in the figures, to obtain the opening characteristics desired by the designer.

[0079] Figure 5 This is a diagram showing the opening area characteristics of the flow control valve 25. More specifically... Figure 5 This indicates the change in the opening area of ​​the pilot valve core 154, the control variable throttle section 165, and the main lift valve 153 relative to the command pressure Pi_fcv of the first boom flow control valve 25. Other flow control valves also have the same structure.

[0080] The pilot valve core 154 has an opening area aPS and the control variable throttling section 165 has an opening control region where the command pressure Pi_fcv is Pi_fcv1 to Pi_fcv4. On the other hand, the main lift valve 153 has an opening control region where the command pressure Pi_fcv is from Pi_fcv2 (> Pi_fcv1) to Pi_fcv3 (< Pi_fcv4). The maximum opening area aMP1 of the main lift valve 153 is set to be sufficiently larger than the opening area aPS of the pilot valve core 154 and the opening area aFB of the control variable throttling section 165. That is, the larger the command pressure Pi_fcv, the smaller the opening of the first boom flow control valve 25, and the smaller the command pressure Pi_fcv, the larger the opening of the first boom flow control valve 25. However, the relationship between the command pressure Pi_fcv and the opening of the first boom flow control valve 25 is not limited to the above example.

[0081] When the command pressure Pi_fcv is between Pi_fcv2 and Pi_fcv3, the opening amount of the first boom flow control valve 25 is equal to the sum of the opening area aMP of the main lift valve 153 and the opening area aPS of the pilot valve core 154. That is, when the opening amount of the pilot valve core 154 to the pilot pressure chambers 168 and 170 is above the threshold S, the first boom flow control valve 25 supplies working oil to the first boom directional control valve 11 via the first pressure chamber 161 and the second pressure chamber 173 connected by the main lift valve 153, and the first pressure chamber 161, connecting paths 163 and 164, the third pressure chamber 166, and the pilot lines (167, 168, 170, 171, 172).

[0082] On the other hand, when the command pressure Pi_fcv is between Pi_fcv3 and Pi_fcv4, the opening area aMP of the main lift valve 153 is zero. Therefore, the opening amount of the first boom flow control valve 25 is equal to the opening area aPS of the pilot valve core 154. That is, when the opening amount of the pilot valve core 154 to the pilot pressure chambers 168 and 170 of the first boom flow control valve 25 is less than the threshold S, the main lift valve 153 blocks the first pressure chamber 161 and the second pressure chamber 173, and supplies working oil to the first boom directional control valve 11 via the first pressure chamber 161, connecting paths 163 and 164, the third pressure chamber 166, and the pilot lines (167, 168, 170, 171, 172).

[0083] Thus, the first boom flow control valve 25 has a region that controls the opening amount relative to the command pressure Pi_fcv by the sum of the opening area aMP of the main lift valve 153 and the opening area aPS of the pilot valve core 154, and a region that controls the opening amount only by the opening area aPS of the pilot valve core 154, which are switched by a predetermined command pressure Pi_fcv3.

[0084] [Function block of controller 114]

[0085] Figure 6 This is the functional block diagram of controller 114. (Example) Figure 6 As shown, the controller 114 includes an actuator target speed calculation unit 114a, an actuator target flow calculation unit 114b, a pump target flow calculation unit 114c, a pump control command calculation unit 114d, a directional control valve target opening calculation unit 114e, a directional control valve control command calculation unit 114f, a flow control valve target opening calculation unit 114g, a flow control valve control command calculation unit 114h, and a calibration processing unit 114i.

[0086] The following description focuses on examples of controlling the hydraulic pump 2, the directional control valve 11 for the first stick (hereinafter referred to as "directional control valve 11"), the flow control valve 25 for the first stick (hereinafter referred to as "flow control valve 25"), and the stick cylinder 215. However, other hydraulic pumps, directional control valves, flow control valves, and hydraulic actuators are also controlled in the same way.

[0087] The actuator target speed calculation unit 114a calculates the target speed of the boom cylinder 215 based on the operation signal output from the operating lever 115b. The actuator target flow calculation unit 114b calculates the target flow rate of the working oil supplied to the boom cylinder 215 based on the actuator target speed calculated by the actuator target speed calculation unit 114a. The pump target flow calculation unit 114c calculates the pump target flow rate of the working oil to be injected by the hydraulic pump 2 based on the actuator target flow rate calculated by the actuator target flow calculation unit 114b. The pump control command calculation unit 114d calculates the pump command current based on the pump target flow rate calculated by the pump target flow calculation unit 114c, and outputs the pump command current to the solenoid valve 113a that supplies pilot pressure to the flow control command pressure port 2a. Thus, the injection capacity of the hydraulic pump 2 is set according to the operation amount of the operating lever 115b. Furthermore, the greater the operation amount of the operating lever 115b, the greater the injection capacity of the hydraulic pump 2.

[0088] The directional control valve target opening calculation unit 114e calculates the target opening of the directional control valve based on the operation signal output from the operating lever 115b and the pressure signals output from pressure sensors 84-90 and 133-137. The directional control valve control command calculation unit 114f calculates the directional control valve command current based on the target opening calculated by the directional control valve target opening calculation unit 114e, and outputs the calculated directional control valve command current to solenoid valves 113b and 113c. Thus, the supply direction of working oil from the directional control valve 11 to the boom cylinder 215 is set according to the operation direction of the operating lever 115b.

[0089] The flow control valve target opening calculation unit 114g calculates the final target opening that ensures flow control accuracy based on the actuator target flow calculated by the actuator target flow calculation unit 114b, the pressure signals output from pressure sensors 84-90 and 133-137, and a predetermined limit opening area. The flow control valve control command calculation unit 114h calculates the flow control valve command current based on the flow control valve target opening calculated by the flow control valve target opening calculation unit 114g, and outputs the calculated flow control valve command current to the solenoid valve 113d. Thus, the flow rate of working oil supplied from the flow control valve 25 to the directional control valve 11 is set according to the operating amount of the operating lever 115b. Furthermore, the greater the operating amount of the operating lever 115b, the greater the flow rate of working oil supplied from the flow control valve 25 to the directional control valve 11.

[0090] Based on the calibration execution instruction output from the calibration instruction device 116, the calibration processing unit 114i outputs the target control command for performing the calibration processing to the pump control command calculation unit 114d, the directional control valve control command calculation unit 114f, and the flow control valve control command calculation unit 114h. Furthermore, based on the pressure signals output from pressure sensors 84-90 and 133-137 and the current signals output from current sensors 143-147, the calibration processing unit 114i adjusts (calibrates) the opening start current of the flow control valve 25.

[0091] [Performance error of solenoid valve 113d]

[0092] Figure 7 This is a diagram illustrating the performance error of solenoid valve 113d. More specifically... Figure 7 The left figure in the figure shows the correspondence between the target opening Atgt of the flow control valve 25 and the command current I to the solenoid valve 113d. Figure 7 The central diagram shows the correspondence between the command current I to solenoid valve 113d and the command pressure Pi to solenoid valve 113d. Figure 7 The right figure in the figure shows the relationship between the command pressure Pi of the solenoid valve 113d and the opening area A of the flow control valve 25.

[0093] The controller 114 is based on the predetermined correspondence between the target opening Atgt and the command current I. Figure 7 (See the left figure in the diagram). The command current I corresponding to the target opening Atgt is calculated and output to the solenoid valve 113d. Here, due to manufacturing deviations of the controller 114, etc., based on... Figure 7 The command current I calculated from the correspondence in the left figure may have a current error CUerror between it and the actual output command current I.

[0094] In addition, such as Figure 7As shown in the central diagram, the output of solenoid valve 113d corresponds to the command pressure Pi of the command current I output from controller 114. Here, due to manufacturing deviations of solenoid valve 113d, a command pressure error Pierror may occur between the command current I and the command pressure Pi. Furthermore, as... Figure 7 As shown in the right figure, the flow control valve 25 is set to have an opening area A corresponding to the command pressure Pi output from the solenoid valve 113d. Here, due to manufacturing deviations of the flow control valve 25, an opening area error Aerror may occur between the command pressure Pi and the opening area A.

[0095] That is, between the target opening Atgt calculated by the controller 114 and the actual opening area A, there may be an error obtained by adding the current error CUerror, the command voltage error Pierror, and the opening area error Aerror. Therefore, in order to correct this error, the controller 114 needs to execute... Figure 8 The calibration process is shown.

[0096] [Calibration Process]

[0097] Figure 8 This is a flowchart of the calibration process. Figure 9 This is a graph showing the time variation of the command current and the change of the load voltage relative to the command current during the calibration process. The operator can perform the calibration process, for example, after the hydraulic excavator 200 is assembled, during routine maintenance, or when parts are replaced. The calibration process for flow control valve 25 is described below, but the same applies to other flow control valves 21-24 and 26-29.

[0098] First, the calibration indicator 116 displays a list of flow control valves 21-29 on the display, allowing the operator to select the object to be calibrated via the operation panel (S11). Here, flow control valve 25 is selected. Then, the calibration indicator 116 specifies the flow control valve 25 selected by the operator and outputs a calibration execution instruction to the controller 114. As another example, the calibration indicator 116 may also automatically select multiple flow control valves 21-29 in a predetermined order and output calibration execution instructions.

[0099] Next, the controller 114 outputs a pump command current to the solenoid valve 113a to reduce the ejection capacity of the hydraulic pump 2 to below a predetermined value (S12). In step S12, it is preferable to reduce the ejection capacity of the hydraulic pump 2 as much as possible within the range that can drive the boom cylinder 215 (i.e., can perform the calibration process).

[0100] Next, the controller 114 controls the hydraulic pump 2, the directional control valve 11, and the flow control valve 25 to change the posture of the boom cylinder 215 to a predetermined posture (S13). This process can be executed automatically by the controller 114 or can be prompted by the operator in the cab 208 to operate the control device via a display.

[0101] As an example, the predetermined posture refers to a posture in which, during the calibration process, the boom cylinder 215 will not move due to its own weight, even if the outlet throttling side of the directional control valve 11 is connected to the oil tank line. As another example, the predetermined posture refers to a posture in which the range of motion of the boom cylinder 215 is limited during the calibration process; more specifically, it is a position where the boom cylinder 215 returns a predetermined amount from the end of its stroke on the loading side to the unloading side. That is, the controller 114 performs an action that extends (moves) the boom cylinder 215 to the end of its stroke and then slightly returns (retracts) it to a predetermined position away from the end of its stroke.

[0102] In the case of boom cylinder 214, the position is the return from the end of the boom lifting stroke to a predetermined position. In the case of bucket cylinder 216, the position is the return from the end of the loading stroke to a predetermined position. In the case of travel motor 205 and swivel motor 206, assuming that the operator has set the outlet throttle side of the directional control valve to a horizontal position before calibration, where the actuator will not move due to its own weight even if connected to the oil tank line, there is no need to change to the predetermined posture in this step. In addition, the predetermined amount refers to the minimum stroke amount that is sufficient and necessary to return the load pressure, which has been pressurized to the overflow pressure set by the overflow valve provided in the pump line, to the actuator holding pressure when moving to the end of the cylinder stroke.

[0103] Next, the controller 114 maximizes the command current output to the solenoid valve 113d (i.e., Pi_fcv4), causing the flow control valve 25 to close (S14). As a result, the oil passages 56 and 57 are blocked, and the working oil injected from the hydraulic pump 2 will not be supplied to the directional control valve 11 via the flow control valve 25.

[0104] Next, the controller 114 outputs command current to the solenoid valves 113b and 113c to open the directional control valve 11, thereby supplying working oil in the direction of extension of the boom cylinder 215 (S15). Then, the controller 114 cuts off the central bypass line 52 (S16). As a result, the parallel line 53 is pressurized to the overflow pressure of the relief valve 32.

[0105] As an example, controller 114 can close relief valve 35 by outputting a command current to solenoid valve 113e. As another example, directional control valve 11 can also be configured to cut off central bypass line 52 when switching to supply working oil to boom cylinder 215. In this case, directional control valve 11 is another example of an opening and closing device. Switching of relief valve 35 is not required in this situation.

[0106] Next, the controller 114 gradually changes the command current output to the solenoid valve 113d in the direction that opens the flow control valve 25 (S17). In this embodiment, the command current is gradually reduced. More specifically, the controller 114 gradually reduces the command current within the range that the main lift valve 153 blocks the flow between the first pressure chamber 161 and the second pressure chamber 173, and the oil passages 56 and 57 are blocked (i.e., Pi_fcv4 to Pi_fcv3).

[0107] Next, controller 114 monitors the changes in load pressure represented by the pressure signal from pressure sensor 88a (S18). In other words, controller 114 gradually reduces the command current. Figure 9 (as shown in the upper figure), until the load pressure detected by pressure sensor 88a changes ( Figure 9 (See the diagram below). Then, the controller 114 determines the command current at the time point of load pressure change (rise) detected by the pressure sensor 88a as the opening start current of the flow control valve 25 (S18: Yes → S19).

[0108] Then, controller 114 performs calibration (S20) using the opening start current determined in step S19. Controller 114 uses, for example, the opening start current to adjust... Figure 7 The left figure shows the correspondence between the target opening Atgt and the command current I. More specifically, controller 114 enables... Figure 7 The solid line in the left figure is moved parallel to make the intercept of the command current I match the current at the start of the opening.

[0109] Next, the controller 114 determines whether there are any other flow control valves 21-29 that are subject to calibration (S21). Then, if the controller 114 determines that there are still flow control valves 21-29 that are subject to calibration (S21: No), the controller 114 executes the process after step S11 again. On the other hand, if the controller 114 determines that the calibration of all flow control valves 21-29 has been performed (S21: Yes), the calibration process ends.

[0110] According to the above-described implementation method, the following effects are achieved, for example.

[0111] According to the above-described implementation, pressure sensors 88a and 88b are used to detect the pressure of the working oil supplied to the boom cylinder 215, so that calibration can be performed even without installing special components on the hydraulic excavator 200.

[0112] Furthermore, according to the above-described embodiment, when the hydraulic pump 2's injection capacity is at its minimum and the parallel line 53 is pressurized to overflow pressure, the command current to the solenoid valve 113d is gradually reduced, causing the pilot valve core 154 to gradually displace, ultimately opening (connecting) the pilot pressure chambers 168 and 170. At this time, the injection capacity of the hydraulic pump 2 is suppressed to the required minimum, and the oil lines 56 and 57 are connected only through the pilot lines (167, 168, 170, 171, 172) of the flow control valve 25. This suppresses vibrations in the vehicle body caused by the abrupt movement of the boom cylinder 215 and enables high-precision measurement of changes in the load pressure of the boom cylinder 215.

[0113] Furthermore, according to the above-described embodiment, the boom cylinder 215 reaches the end of its stroke from a predetermined position with the necessary minimum stroke. Therefore, after the flow control valve 25 opens, it immediately rises from the holding pressure to the overflow pressure in a short time, making it easy to measure changes in the load pressure.

[0114] Furthermore, according to the above-described embodiment, by setting the flow rate of the working oil supplied to the boom cylinder 215 and the stroke of the boom cylinder 215 to a necessary minimum, the amount of movement of the hydraulic excavator 200 during calibration is also set to a necessary minimum. As a result, the impact on the surrounding environment during calibration can be reduced.

[0115] Furthermore, according to the above-described embodiment, by performing calibration in a state where the stick cylinder 215 does not move due to its own weight, it is possible to prevent the stick cylinder 215 from moving when the directional control valve 11 is opened.

[0116] The above-described embodiments are illustrative examples of the present invention and are not intended to limit the scope of the invention to these embodiments only. Those skilled in the art can implement the invention in various other ways without departing from its spirit.

[0117] Symbol Explanation

[0118] 1, 2, 3: Hydraulic pump

[0119] 1a, 2a, 3a: Flow control command press port

[0120] 6-16: Directional control valve

[0121] 11a, 11b, 35a: Command compression ports

[0122] 21-29: Flow control valve

[0123] 31-33: Relief valve

[0124] 34, 35, 36: Relief valves

[0125] 37: Confluence valve

[0126] 38, 39: Check valve

[0127] 41, 51, 62: Ejection pipes

[0128] 42, 52, 63: Central bypass pipeline

[0129] 43, 53, 64: Parallel pipeline

[0130] 72-75: Actuator piping

[0131] 84-90, 133-137: Pressure sensors

[0132] 91-92: Temperature sensor

[0133] 100: Hydraulic drive system

[0134] 111: Pilot Pump

[0135] 112: Pilot-operated relief valve

[0136] 113: Solenoid valve unit

[0137] 113a-113e: Solenoid valves

[0138] 114: Controller

[0139] 114a: Actuator target speed calculation unit

[0140] 114b: Actuator target flow calculation unit

[0141] 114c: Pump target flow calculation unit

[0142] 114d: Pump control command processing unit

[0143] 114e: Directional control valve target opening calculation unit

[0144] 114f: Directional control valve control command processing unit

[0145] 114g: Flow control valve target opening calculation unit

[0146] 114h: Flow control valve control command processing unit

[0147] 114i: Calibration Processing Department

[0148] 115a, 115b: Operating lever

[0149] 116: Calibration indicator device

[0150] 123-127: Pre-operative pathway

[0151] 143-147: Current Sensor

[0152] 151: Main shell

[0153] 152: Pilot housing

[0154] 153: Main lift valve

[0155] 154: Pilot valve core

[0156] 155, 158, 159: Coil springs

[0157] 156: Ball-type check valve

[0158] 161: First Pressure Chamber

[0159] 162, 169: Notch

[0160] 163, 164: Connecting paths

[0161] 165: Control of variable throttling section

[0162] 166: Third pressure chamber

[0163] 167, 171, 172: Pilot oil circuit

[0164] 168, 170: Pilot pressure chamber

[0165] 173: Second pressure chamber

[0166] 174, 175: Pilot ports

[0167] 200: Hydraulic excavator

[0168] 201: Lower driving body

[0169] 202: Upper Rotational Body

[0170] 204: Tracks

[0171] 205: Drive motor

[0172] 206: Rotary motor

[0173] 207: Rotating Frame

[0174] 208: Driver's Cab

[0175] 209: Counterweight

[0176] 210: Front working machine

[0177] 211: Lever

[0178] 212: Fighting Pole

[0179] 213: Bucket

[0180] 214: Boom Cylinder

[0181] 215: Bucket Cylinder

[0182] 216: Bucket cylinder

[0183] 221, 226: Posture sensors.

Claims

1. A hydraulic drive system, comprising: A hydraulic pump that sprays working oil stored in a working oil tank; A hydraulic actuator, driven by working oil ejected from the hydraulic pump; A directional control valve is configured in the supply line from the hydraulic pump to the hydraulic actuator to control the direction of the supply of working oil to the hydraulic actuator; A flow control valve is positioned upstream of the flow of working oil in the directional control valve of the supply line to control the flow rate of working oil supplied from the hydraulic pump to the directional control valve. A pressure sensor that detects the pressure of the working oil supplied to the hydraulic actuator; A solenoid valve that opens and closes the flow control valve by supplying pilot pressure to the pilot port of the flow control valve; and The controller performs a calibration process that adjusts the command current output to the solenoid valve. Its features are, In the calibration process, with the flow control valve closed and the directional control valve open, the controller causes the command current output to the solenoid valve to change in the direction that causes the flow control valve to open, and determines the command current at the time point of pressure change detected by the pressure sensor as the opening current of the flow control valve.

2. The hydraulic drive system according to claim 1, characterized in that, The hydraulic drive system includes an opening and closing device for opening and closing a bypass line from the hydraulic pump through the directional control valve to the working oil tank. In the calibration process, the controller, with the flow control valve closed, the directional control valve open, and the opening / closing device closed, causes the command current output to the solenoid valve to change in the direction that causes the flow control valve to open.

3. The hydraulic drive system according to claim 1, characterized in that, In the calibration process, the controller, while the posture is changed to a predetermined posture in which the hydraulic actuator does not move due to its own weight, causes the command current output to the solenoid valve to change in the direction that causes the flow control valve to open.

4. The hydraulic drive system according to claim 3, characterized in that, The hydraulic pump is a variable capacity type. During the calibration process, the controller reduces the ejection capacity of the hydraulic pump to below a predetermined value before changing the posture of the hydraulic actuator to the predetermined posture.

5. The hydraulic drive system according to claim 1, characterized in that, The hydraulic actuator is a hydraulic cylinder that extends and retracts due to the supply and discharge of working oil. In the calibration process, the controller controls the flow control valve and the directional control valve to move the hydraulic cylinder to the end of its stroke and return to a predetermined position away from the end of its stroke, thereby opening the directional control valve by moving the hydraulic cylinder toward the end of its stroke.

6. The hydraulic drive system according to claim 1, characterized in that, The hydraulic drive system also includes an indicator device for instructing the execution of the calibration process. The controller executes the calibration process based on the execution instruction of the indication device.

7. The hydraulic drive system according to claim 1, characterized in that, The flow control valve includes: The housing has a first pressure chamber connected to the supply line on the hydraulic pump side, a second pressure chamber connected to the supply line on the directional control valve side, a third pressure chamber disposed opposite to the first pressure chamber, and a pilot line connecting the third pressure chamber and the second pressure chamber. The main valve moves in a direction that connects or blocks the first pressure chamber from the second pressure chamber by means of the pressure difference between the first pressure chamber and the third pressure chamber; and A pilot valve spool, which opens and closes the pilot passage by the pilot pressure supplied through the solenoid valve. The main valve includes: a connecting path that connects the first pressure chamber and the third pressure chamber; and a control variable throttling section formed at the end of the connecting path on the third pressure chamber side, wherein the lower the pressure in the third pressure chamber, the larger the opening area. The flow control valve performs the following control: when the opening of the pilot valve core to the pilot guide line is less than a threshold, the main valve blocks the connection between the first pressure chamber and the second pressure chamber, and supplies working oil to the direction control valve through the first pressure chamber, the connecting path, the third pressure chamber and the pilot guide line; as well as When the opening of the pilot valve core to the pilot line is greater than or equal to the threshold, working oil is supplied to the directional control valve through the first pressure chamber and the second pressure chamber connected by the main valve, the connecting path, the third pressure chamber, and the pilot line.

8. The hydraulic drive system according to claim 7, characterized in that, During the calibration process, the controller varies the command current within a range where the opening of the pilot circuit is less than the threshold.

9. The hydraulic drive system according to claim 1, characterized in that, The controller includes: The first controller, which is mounted on the vehicle body; and A second controller, located on a portable device separate from the vehicle body, instructs the first controller to perform the calibration process.

10. The hydraulic drive system according to claim 1, characterized in that, The controller is mounted on the vehicle body.

Images