Hydraulic system

Abstract

A hydraulic system according to an embodiment of the present application includes: a hydraulic pump provided with a swash plate; a swash plate drive piston provided with a large diameter portion for adjusting the inclination of the swash plate; a swash plate control hydraulic line for supplying a portion of working oil discharged from the hydraulic pump to the large diameter portion; a swash plate control valve for controlling the flow rate of working oil supplied to the large diameter portion; an electronic proportional pressure reducing valve for generating a pilot pressure to be applied to the swash plate control valve in proportion to the magnitude of an input current; a pressure sensor for measuring the pressure of working oil supplied to the large diameter portion; and a control device for supplying the input current to the electronic proportional pressure reducing valve and correcting the discharge flow rate of the hydraulic pump in relation to the input current based on the rate of change of the large diameter portion pressure measured by the pressure sensor.

Description

Technical Field

[0001] The present invention relates to a hydraulic system, and more particularly to a hydraulic system capable of correcting a discharge flow rate of a variable displacement hydraulic pump. Background Art

[0002] Typically, hydraulic systems use hydraulic fluid discharged from a hydraulic pump to transmit power to various drive devices. Such systems are widely used in construction machinery and industrial vehicles. For example, a hydraulic system used in construction machinery uses hydraulic fluid discharged from an engine-driven hydraulic pump to drive multiple working devices, such as a placing boom, a boom, a bucket, and travel and swing motors.

[0003] According to a swash plate type variable displacement hydraulic pump used in such a hydraulic system, a discharge flow rate is controlled by adjusting the angle of a swash plate formed in the pump using a flow control device such as a regulator.

[0004] This type of hydraulic control device can be divided into mechanical control and electronic control. In the past, mechanical control was the main method, but in recent years, electronic control has become more and more common. Electronic control hydraulic control devices control the angle of the swash plate by applying an electrical signal to the regulator. This type of electronic control hydraulic control device controls a pressure-controlled electronic hydraulic pump. This pressure-controlled electronic hydraulic pump is controlled by a control device that receives the operating signal of the operating device installed in the driver's seat of the construction machinery and the angle value of the swash plate from the angle sensor installed in the electronic hydraulic pump as electrical signals, and outputs the electrical signal used to control the pressure to the corresponding electronic hydraulic pump.

[0005] The flow rate of hydraulic oil discharged from the hydraulic pump is controlled by a flow control device such as a regulator. The regulator's electronic proportional control valve generates pilot pressure in response to the input current. The swash plate control valve then controls the movement of the swash plate drive piston and adjusts the swash plate angle based on the pilot pressure generated by the electronic proportional control valve, thereby controlling the discharge flow rate of the hydraulic pump.

[0006] In this type of hydraulic system, the flow characteristics of each regulator vary from product to product. Therefore, while manufacturers measure the flow characteristics through factory testing before shipping variable displacement hydraulic pumps, these tests are conducted under only a single, pre-set pressure condition.

[0007] However, in many types of equipment, such as construction machinery equipped with variable displacement hydraulic pumps, the pressure conditions in the equipment's operating environment often differ from those used during factory testing. Consequently, the flow characteristics measured during factory testing often fail to replicate after the pumps are installed in the equipment. This creates a discrepancy between the flow characteristics measured during factory testing and the flow characteristics when the pumps are actually installed in the equipment. Summary of the Invention

[0008] An embodiment of the present invention provides a hydraulic system capable of correcting the discharge flow rate characteristics of a variable displacement hydraulic pump while being mounted on an actually used device.

[0009] According to an embodiment of the present invention, a hydraulic system includes: a variable displacement hydraulic pump having a swash plate; a swash plate driving piston having a large diameter portion and a small diameter portion, the inclination of the swash plate of the hydraulic pump being adjusted according to changes in pressure applied to the large diameter portion; a swash plate control hydraulic line for supplying a portion of the hydraulic oil discharged from the hydraulic pump to the large diameter portion; a swash plate control valve provided on the swash plate control hydraulic line for controlling the flow rate of the hydraulic oil supplied to the large diameter portion according to the magnitude of a received pilot pressure; an electronic proportional pressure reducing valve (EPPRV) for generating the pilot pressure to be applied to the swash plate control valve in proportion to the magnitude of an input current; a pressure sensor for measuring the pressure of the hydraulic oil supplied to the large diameter portion of the swash plate driving piston; and a control device for controlling the discharge flow rate of the hydraulic pump by supplying the input current to the electronic proportional pressure reducing valve, and correcting the discharge flow rate of the hydraulic pump in relation to the input current according to a rate of change in the large diameter portion pressure measured by the pressure sensor.

[0010] The control device may control the hydraulic pump based on a current-flow rate characteristic line indicating a correlation between the magnitude of the input current and the magnitude of the discharge flow rate.

[0011] Furthermore, the control device can search for a first correction point corresponding to the minimum stroke of the swash plate drive piston and a second correction point corresponding to the maximum stroke of the swash plate drive piston from the pressure change rate of the working oil supplied to the large-diameter portion of the swash plate drive piston, calculate a corrected current-flow characteristic line connecting the first correction point and the second correction point, and replace the pre-correction current-flow characteristic line with the calculated corrected current-flow characteristic line, thereby controlling the hydraulic pump.

[0012] According to the embodiment of the present invention, the hydraulic system of the present invention can correct the discharge flow rate characteristics of the variable displacement hydraulic pump while being mounted on an actually used device. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 FIG. 4 is a hydraulic circuit diagram of a hydraulic system according to an embodiment of the present invention.

[0014] Figure 2 For illustration purposes Figure 1 A graph showing the process of correcting the current-flow characteristics of the hydraulic system in FIG.

[0015] Figure 3 To show Figure 1 Flowchart of the process of correcting the current-flow characteristics of the hydraulic system in FIG.

[0016] Description of Reference Signs

[0017] 101: Hydraulic Systems

[0018] 200: Swash plate drive piston

[0019] 210: Small diameter part

[0020] 290: Large diameter part

[0021] 300: Inclined plate control valve

[0022] 310: Hydraulic pump

[0023] 314: Inclined Plate

[0024] 370: Pilot pump

[0025] 500: Electronic proportional pressure reducing valve

[0026] 610: Main hydraulic line

[0027] 640: Swash plate control hydraulic line

[0028] 700: Control device

[0029] 750: Pressure sensor. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. The present invention can be embodied in various embodiments and is not limited to the embodiments described herein.

[0031] The various figures are schematic illustrations and are not drawn to scale. For clarity and convenience, the relative sizes and proportions of various parts in the figures are shown exaggerated or reduced relative to their actual sizes. Any dimensions are illustrative only and are not limiting. Furthermore, to indicate similar features, identical structures, elements, or components shown in two or more figures are denoted by the same reference numerals.

[0032] The embodiments of the present invention specifically represent ideal embodiments of the present invention. As a result, many variations from the illustrations are contemplated. Therefore, the embodiments are not limited to the specific configurations shown in the illustrated areas and include, for example, variations in configuration based on manufacturing.

[0033] Below, refer to Figure 1 The hydraulic system 101 according to one embodiment of the present invention will now be described. This hydraulic system 101 according to one embodiment of the present invention can be used in construction machinery or industrial vehicles, and can use hydraulic fluid discharged from an engine-driven hydraulic pump 310 to drive various drive devices, such as a boom cylinder, a boom cylinder, a bucket cylinder, a swing motor, and a travel motor.

[0034] like Figure 1 As shown, the hydraulic system 101 according to an embodiment of the present invention includes: a hydraulic pump 310 , a swash plate driving piston 200 , a swash plate control hydraulic line 640 , a swash plate control valve 300 , an electronic proportional pressure reducing valve 500 , a pressure sensor 750 and a control device 700 .

[0035] The hydraulic system 101 according to one embodiment of the present invention may further include a main hydraulic line 610 and a pilot pump 370 .

[0036] The hydraulic pump 310 is a swash plate type variable displacement type. That is, the hydraulic pump 310 includes a swash plate 314. The discharge flow rate of the hydraulic pump 310 can be adjusted by adjusting the angle of the swash plate 314.

[0037] The main hydraulic line 610 moves the hydraulic oil discharged from the hydraulic pump 310. For example, the main hydraulic line 610 moves the hydraulic oil discharged from the hydraulic pump 310 to a plurality of drive devices via a main control valve (not shown).

[0038] The swash plate driving piston 200 adjusts the angle of the swash plate 314 of the hydraulic pump 310. The swash plate driving piston 200 has a large diameter portion 290 and a small diameter portion 210, and adjusts the inclination of the swash plate 314 of the hydraulic pump 310 according to the change in pressure applied to the large diameter portion 290.

[0039] The swash plate control hydraulic line 640 is formed in a manner that a portion of the working oil discharged by the hydraulic pump 310 is supplied to the large diameter portion 290 of the swash plate drive piston 200. That is, the swash plate control hydraulic line 640 is branched from the main hydraulic line 610 and connected to the swash plate drive piston 200 by the swash plate control valve 300 to be described later.

[0040] The swash plate control valve 300 controls the flow rate of the working oil to be supplied to the large diameter portion 290 of the swash plate drive piston 200 by being provided on the swash plate control hydraulic line 640. Specifically, the swash plate control valve 300 changes the internal flow path by switching the position of the spool, thereby supplying the working oil moved through the swash plate control hydraulic line 640 to the large diameter portion 290 of the swash plate drive piston 200 or evacuating the working oil discharged from the large diameter portion 290 of the swash plate drive piston 200. In this case, the swash plate control valve 300 controls the flow rate of the working oil supplied to the large diameter portion of the swash plate drive piston 200 according to the size of the pilot pressure received. For example, the pilot pressure moves the position of the spool by applying pressure to one side of the swash plate control valve 300.

[0041] The electronic proportional pressure reducing valve (EPPRV) 500 generates the pilot pressure to be applied to one side of the swash plate control valve 300. Such an electronic proportional pressure reducing valve 500 is an electronically controlled valve that generates the pilot pressure in proportion to the input current supplied from the control device 700 to be described later. That is, the electronic proportional pressure reducing valve 500 can adjust the size of the generated pilot pressure in proportion to the size of the input current supplied from the control device 700.

[0042] The pilot pump 370 is used to generate the pilot pressure. That is, the pressure of the working oil discharged by the pilot pump 370 is processed by the electronic proportional pressure reducing valve 500 into the pilot pressure to be transmitted to the control valve 300.

[0043] The pressure sensor 750 can measure the pressure of the working oil supplied to the large diameter portion 290 of the swash plate drive piston 200. For example, the pressure sensor 750 can be provided to the swash plate control hydraulic line 640 between the swash plate control valve 300 and the large diameter portion 290 of the swash plate drive piston 200.

[0044] The control device 700 can control the electronic proportional pressure reducing valve 500 according to an operation signal of a user or a working condition. That is, the electronic proportional pressure reducing valve 500 generates the pilot pressure according to the input current received from the control device 700.

[0045] As described above, the pilot pressure generated by the electronic proportional pressure reducing valve 500 under the control of the control device 700 is transmitted to the swash plate control valve 300. The swash plate control valve 300 operates in response to the received pilot pressure to control the operation of the swash plate driving piston 200. Furthermore, the angle of the swash plate 314 of the hydraulic pump 310 is adjusted in response to the operation of the swash plate driving piston 200, thereby controlling the discharge flow rate of the hydraulic pump 310.

[0046] Furthermore, according to one embodiment of the present invention, the control device 700 can control the discharge flow of the hydraulic pump 310 by supplying input current to the electronic proportional pressure reducing valve 500, and can correct the discharge flow of the hydraulic pump 310 related to the input current according to the pressure change rate of the large diameter part measured by the pressure sensor 750.

[0047] Furthermore, the control device 700 controls the hydraulic pump 310 based on a current-flow characteristic line that represents the correlation between the magnitude of the input current and the magnitude of the discharge flow rate. Furthermore, the hydraulic pump 310 is shipped from the factory in a manner controlled according to the initially set current-flow characteristic line after the flow characteristics are measured during factory testing. However, for various equipment, such as construction machinery equipped with the hydraulic pump 310, there are cases where the pressure conditions in the equipment's operating environment do not match the pressure conditions during factory testing. In other words, there may be cases where an error occurs between the flow characteristics of the hydraulic pump 310 measured during factory testing and the flow characteristics of the hydraulic pump 310 when actually installed in the equipment.

[0048] However, the hydraulic system 101 of one embodiment of the present invention can be easily and effectively calibrated based on the pressure change rate of the large diameter portion measured by the pressure sensor 750 so that the set current-flow characteristic is as close as possible to the actual current-flow characteristic of the hydraulic pump 310 actually installed on the equipment.

[0049] According to the above-described configuration, the hydraulic system 101 according to one embodiment of the present invention can correct the discharge flow rate characteristics of the variable displacement hydraulic pump while being mounted on an actually used device.

[0050] That is, in order to eliminate errors when the hydraulic pump 310 is installed in the actual device, the discharge flow rate of the hydraulic pump 310 related to the input current can be corrected when the hydraulic pump 310 is installed in the actual device, thereby more accurately controlling the discharge flow rate of the hydraulic pump 310.

[0051] Below, refer to Figure 2 and Figure 3 , a method for correcting a current-flow rate characteristic line for controlling the discharge flow rate of the hydraulic pump 310 in the hydraulic system 101 according to an embodiment of the present invention will be described in detail.

[0052] like Figure 2 and Figure 3As shown, the control device 700 transmits an input current to the electronic proportional pressure reducing valve 500 that generates a pilot pressure for controlling the swash plate driving piston 200 .

[0053] Moreover, the control device 700 measures and analyzes the pressure change rate of the working oil supplied to the large diameter portion 290 of the swash plate drive piston 200 based on the change in the input current, thereby finding a first correction point A corresponding to the minimum stroke of the swash plate drive piston 200 and a second correction point B corresponding to the maximum stroke of the swash plate drive piston 200.

[0054] The pressure of the large diameter portion 290 of the swash plate driving piston 200 gradually increases or decreases, and rises sharply when the swash plate driving piston 200 reaches the minimum stroke and the maximum stroke. In addition, the minimum flow rate and the maximum flow rate of the hydraulic pump 310 are determined according to the specifications.

[0055] Therefore, the time point at which the pressure peak occurs when the swash plate driving piston 200 reaches its minimum stroke is set as the minimum discharge flow rate of the hydraulic pump 310 and is set as the first calibration point A. The time point at which the pressure peak occurs when the swash plate driving piston 200 reaches its maximum stroke is set as the maximum discharge flow rate of the hydraulic pump 310 and is set as the second calibration point B. The first calibration point A and the second calibration point B are then linearly connected to calculate a corrected current-flow characteristic line. The calculated corrected current-flow characteristic line replaces the pre-calibration current-flow characteristic line. The pre-calibration current-flow characteristic line can be the current-flow characteristic line set by factory measurement.

[0056] Furthermore, as described above, the calculated corrected current-flow rate characteristic line was compared with the actual current-flow rate characteristic in a state where the device is mounted, and it was confirmed that they were very close.

[0057] As described above, in the hydraulic system 101 according to one embodiment of the present invention, the control device 700 searches for a first correction point A corresponding to the minimum stroke of the swash plate drive piston 200 and a second correction point B corresponding to the maximum stroke of the swash plate drive piston 200 from the pressure change rate of the working oil flowing into the large diameter portion 290 of the swash plate drive piston 200, calculates a corrected current-flow characteristic line linearly connecting the first correction point A and the second correction point B, and replaces the pre-correction current-flow characteristic line with the calculated corrected current-flow characteristic line to control the hydraulic pump 310. When the hydraulic pump 310 is mounted on an actual device, the discharge flow characteristic of the variable capacity hydraulic pump 310 can be easily and effectively corrected.

[0058] On the other hand, although Figure 2 In the example, only the second calibration point B is changed, but this is only exemplary. The first calibration point A may also be changed, or both the first calibration point A and the second calibration point B may be changed.

[0059] Although the embodiments of the present invention are described above with reference to the accompanying drawings, it will be understood by those skilled in the art that the present invention may be implemented in other specific embodiments without changing the technical concept or essential features of the present invention.

[0060] Therefore, it must be understood that the embodiments described above are merely illustrative in all aspects and do not limit the present invention. The scope of the present invention is represented by the scope of protection claimed in the invention, rather than the detailed description described above. It should be interpreted that all changes or modifications derived from the meaning, scope and equivalent concepts of the scope of protection claimed in the invention are included in the scope of the present invention.

Claims

1. A hydraulic system, characterized in that: include: A variable capacity hydraulic pump provided with a swash plate; a swash plate driving piston having a large diameter portion and a small diameter portion, and adjusting the inclination of the swash plate of the hydraulic pump according to a change in pressure applied to the large diameter portion; a swash plate controlled hydraulic line for supplying a portion of the hydraulic oil discharged from the hydraulic pump to the large diameter portion; a swash plate control valve, provided on the swash plate control hydraulic line, for controlling the flow of the working oil supplied to the large diameter portion according to the magnitude of the pilot pressure received; an electronic proportional pressure reducing valve for generating the pilot pressure to be applied to the swash plate control valve in a manner proportional to the magnitude of the input current; a pressure sensor for measuring the pressure of the hydraulic oil supplied to the large diameter portion of the swash plate driving piston; as well as a control device for controlling the discharge flow rate of the hydraulic pump by supplying the input current to the electronic proportional pressure reducing valve, and correcting the discharge flow rate of the hydraulic pump in relation to the input current based on the rate of change of the large diameter portion pressure measured by the pressure sensor; The control device searches for a first correction point corresponding to a minimum stroke of the swash plate drive piston and a second correction point corresponding to a maximum stroke of the swash plate drive piston from the rate of change in pressure of the working oil supplied to the large-diameter portion of the swash plate drive piston, calculates a corrected current-flow characteristic line connecting the first correction point and the second correction point, and replaces the pre-correction current-flow characteristic line with the calculated corrected current-flow characteristic line, thereby controlling the hydraulic pump.

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