Hydraulic apparatus with position detector

Abstract

A hydraulic device with a position detector capable of achieving ease of adjustment process during manufacturing and ease of adjustment process when loaded into a host machine without integrating a servo amplifier, which is feedback controlled by a servo amplifier based on a deviation between an instruction value of an instruction signal and a position detection value from the position detector, wherein there is provided an arithmetic processing unit that outputs the position detection value as a detection signal; a communicator that transmits the detection signal to the servo amplifier and receives a signal from the servo amplifier; and a storage unit that stores characteristic information of the hydraulic device in a readable manner via the communicator, wherein the characteristic information of the hydraulic device includes at least calibration information that corresponds the position detection value by the position detector and a characteristic value of the hydraulic device, which is measured in advance in a test bench of the hydraulic device, and flow characteristic information that corresponds a flow of the hydraulic device with respect to the instruction signal and the instruction signal.

Description

Technical Field

[0001] This invention relates, for example, to a hydraulic device equipped with a position detector for detecting the displacement of valve components such as valve stems of hydraulic servo valves. More specifically, this invention relates to a hydraulic device that can be optimized by simply reading out the characteristic information of the hydraulic device through a storage unit that has pre-stored characteristic information of the hydraulic device, including calibration information relative to the position detector, and can simplify the adjustment process during manufacturing and the adjustment process when assembling with the main machine. Background Technology

[0002] For example, a hydraulic servo valve that drives various hydraulic devices, actuators, and other machine tools receives a command signal from a controller on the machine tool side to a servo amplifier connected to a power source. This servo amplifier then supplies a control current corresponding to the command signal to the motor, moving the valve stem to a valve opening position corresponding to the commanded flow direction and flow rate of the working oil. Within the servo amplifier, the signal from the current position detected by a position detector that measures the valve stem's position is compared with the command signal. Based on the deviation, the current supply is adjusted to provide feedback control over the valve stem's movement.

[0003] Hydraulic servo valves include proportional electromagnetic direct-acting directional and flow control valves and direct-acting hydraulic linear servo valves. These valves change flow rate and switch flow paths (directions) through the linear movement of the valve stem, caused by the movable iron core of an electromagnetic solenoid corresponding to energization or by the displacement of a movable coil (voice coil) of a linear motor. In such hydraulic servo valves, a differential transformer, typically an LVDT (Linear Variable Differential Transformer), is integrated as a position detector for feedback control of the valve stem position (see, for example, Patent Documents 1, 2, and 3). Such hydraulic servo valves are driven and controlled by a servo amplifier connected together with the position detector.

[0004] For example, having Figure 8 (a) shows a pair of solenoids (double solenoids: SOLa, SOLb) and an LVDT for valve stem position detection, such as Figure 8As shown in (b), the proportional electromagnetic directional flow control valve 200 connected to the servo amplifier 300 has a configuration with four ports: a working oil inflow port P from the supply source, two ports A and B for hydraulic control inflow and outflow, and a return port T to the oil tank. Current is supplied based on a command signal, and the valve stem is moved within the valve by a solenoid driven by an excitation signal to control the inflow and outflow of each port. At the neutral point of the valve mechanism, the flow rates at ports A and B are zero. That is, as the valve stem is driven by the excitation of the first solenoid SOLa corresponding to the command signal to move from the neutral point in one direction, the outflow rate at port A increases, and the inflow rate to port B increases. Conversely, as the valve stem is driven by the excitation of the second solenoid SOLb to move in the opposite direction, the outflow rate at port B increases, and the inflow rate to port A increases.

[0005] Additionally, LVDT, such as Figure 9 As shown, the system typically includes a core 203 fixed by a rod 202 extending outward from the end of the valve stem 201 towards the valve body; a tube member 204 into which the core 203 is inserted; and a detection coil consisting of a pair of secondary coils 206 symmetrically wound on both sides of a primary coil 205 wound around the center of the outer periphery of the tube member 204. The primary coil 205 is energized by an alternating current of a predetermined amplitude and frequency supplied by a servo amplifier, outputting a differential voltage between itself and the secondary coils 206, whose position changes accordingly as the core 203 within the coil that moves along with the valve stem 201. This analog signal output by the voltage is digitized by an A / D converter, and then processed by a signal processing unit to obtain a digital detection signal as a position detection value.

[0006] The assembly length of the core 203 can be finely adjusted by the fastening of the screw structure 210 that fixes the rod 202 to the end of the valve stem 201, and the tube member 204 is a structure in which the position of the LVDT body can be variably adjusted by the fastening of the nut 230 from the outer end side that is opposite to the adjusting spring 220 clamped on the valve body side.

[0007] Therefore, when mounting sensors on hydraulic equipment, a position detector must be installed during the manufacturing process of the hydraulic equipment, and a precise adjustment must be performed on a test bench after installation to ensure that the origin of the hydraulic equipment's control mechanism and the position detector are aligned. The aforementioned hydraulic servo valve is also produced after pre-adjustment that aligns the valve stem's neutral zero point with the position detector's origin.

[0008] Prior art literature

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 10-141305

[0011] Patent Document 2: Japanese Patent Application Publication No. 09-303328

[0012] Patent Document 3: Japanese Patent Application Publication No. 2012-57776 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] Typically, the adjustment and inspection of hydraulic equipment on a test bench are performed using an amplifier installed at the hydraulic equipment manufacturing plant. Furthermore, the servo amplifiers actually used to drive and control the hydraulic equipment mounted on the mother machine are adjusted and inspected under electrical conditions using an electronic simulated load device in a separate factory dedicated to electronic equipment before being shipped. Therefore, the hydraulic equipment and servo amplifier assembled on the mother machine can be used in a real-world environment through combined adjustment.

[0015] That is, even if the origin is adjusted during the manufacturing process as described above, the hydraulic characteristics of the hydraulic equipment are different. In this control mechanism and position detection device, because there are individual differences in the sensitivity of the flow rate and other parameters relative to the position, the flow characteristics and other parameters can be adjusted by combining the hydraulic equipment and the servo amplifier that drives and controls it when assembling it on the mother machine, so that it can be used in the actual environment.

[0016] For example, the flow characteristics of a hydraulic servo valve relative to the valve stem displacement are not necessarily a linear relationship with a certain proportion. Figure 8 (a) Directional flow control valve, such as Figure 10 As shown in the graph of the flow characteristics relative to the command signal, even for different types, the flow rate relative to the command signal (input voltage VDC) of the servo amplifier is not a monotonic proportional characteristic. Due to the valve mechanism, there must be a range with almost no flow rate change near the input voltage of 0VDC, the so-called insensitive region, which becomes a saturated flow characteristic as it approaches the maximum input voltage of 10VDC.

[0017] Furthermore, because the shape and size deviations of the flow control mechanism of the hydraulic servo valve and the displacement detection of the position detector also result in linearity errors and deviations, the flow characteristics relative to the valve stem displacement exhibit linearity errors and deviations. Since such flow errors cannot be completely corrected by adjusting the zero point and span in the servo amplifier alone, corrections are made as part of the control of the master unit, such as the hydraulic cylinder.

[0018] That is, when the hydraulic servo valve and servo amplifier are installed in the hydraulic cylinder serving as the master unit, the hydraulic cylinder is tested and operated. While reciprocating at a certain speed, the servo amplifier is adjusted so that the maximum flow rate of the hydraulic servo valve's valve mechanism neutral point and the hydraulic cylinder's stop point, or the maximum valve opening, is suitable for the maximum speed of the hydraulic cylinder. In particular, because the flow rate corresponding to the valve opening due to the valve column displacement is non-linear with respect to the command signal, this valve characteristic is taken into account, and the amplifier is adjusted to regulate the speed of the hydraulic cylinder controlled by the flow rate corresponding to the valve opening relative to the command signal.

[0019] Furthermore, when modifying hydraulic equipment on the same machine tool, existing servo amplifiers need to be readjusted to adapt them or be modified along with the servo amplifier. This is especially true for hydraulic servo valves, where there are many specially designed varieties and a high frequency of new designs. Therefore, after the servo amplifier is designed, a new model is designed or a modified hydraulic servo valve is used. In this case, because readjusting the servo amplifier is very troublesome, it is often replaced along with the paired servo amplifiers that are adjusted together with the new hydraulic servo valve. That is, some hydraulic equipment is shipped as an integrated product until it is adjusted and combined with the servo amplifier on the test bench at the manufacturing plant. In such integrated products, the aforementioned trial operation and adjustment in a real-world environment is unnecessary, but the manufacturing burden increases. Additionally, if only one of the hydraulic equipment or the servo amplifier fails, both need to be replaced as a pair.

[0020] On the other hand, there are also hydraulic equipment products equipped with dedicated servo amplifiers (for example, see Patent Document 3). This structure simplifies cable routing, and during the manufacturing process, adjustments to the control mechanism and sensors of the hydraulic equipment can be made using the servo amplifier in a hydraulic equipment test bench to address individual differences, improving ease of installation into the mainframe. However, the installation environment of hydraulic equipment assembled on the mainframe is often high-temperature or requires water, presenting harsh conditions for the servo amplifier. Furthermore, design constraints such as miniaturization of the servo amplifier result in reduced electrical power, leading to compromises in its functionality and performance. This is particularly true in large direct-acting hydraulic servo valves, where the structure maximizes the motor's drive power, making the integration of a servo amplifier difficult and impractical.

[0021] In view of the above problems, the object of the present invention is to provide a hydraulic device with a position detector, which can simplify the adjustment process during manufacturing and achieve the same level of ease of adjustment when installing it into the machine without integrating or mounting the servo amplifier as a product.

[0022] The means to solve the problem

[0023] To achieve the above objectives, the invention described in technical solution 1 is a hydraulic device with a position detector. This device is driven and controlled by a servo amplifier in response to a command signal. It integrates a position detector that generates an output signal corresponding to the position of the valve component that determines the valve opening and the direction of working oil flow. The servo amplifier performs feedback control based on the deviation between the command value of the command signal and the position detection value based on the output signal.

[0024] The device includes a processing unit, a communication unit, and a storage unit. The processing unit processes the output from the position detector and outputs the position detection value as a detection signal. The communication unit transmits the detection signal to the servo amplifier and receives signals from the servo amplifier. The storage unit readablely stores characteristic information of the hydraulic equipment via the communication unit.

[0025] The characteristic information of the hydraulic equipment stored in the aforementioned storage unit includes at least correction information and flow characteristic information. The correction information is obtained by measuring in advance on a test bench during the manufacturing process of the hydraulic equipment, so that the position detection value by the position detector corresponds to the characteristic value of the hydraulic equipment. The flow characteristic information is the flow characteristic information of the hydraulic equipment relative to the command signal, which corresponds to the command signal.

[0026] The hydraulic device with a position detector of the invention described in technical solution 2 is, in the hydraulic device with a position detector described in technical solution 1, further including, in the characteristic information of the hydraulic device stored in the storage unit, a control program and control constants suitable for the hydraulic device.

[0027] The hydraulic device with a position detector of the invention described in technical solution 3 is, in the hydraulic device with a position detector described in technical solution 1 or 2, wherein the above-mentioned storage unit further stores an abnormality detection current setting value, which is used to compare with a drive current measurement value measured by moving the valve component each time the machine installed in the above-mentioned hydraulic device is started.

[0028] The hydraulic device with a position detector of the invention described in technical solution 4 is the hydraulic device with a position detector described in technical solution 3. The storage unit has the following functions: it stores the drive current value measured by moving the valve component before the hydraulic device leaves the factory as the initial value of the drive current, and stores the drive current measurement value at each start of the machine to accumulate over time.

[0029] The hydraulic device with a position detector according to technical solution 5 is, in any one of the hydraulic devices with a position detector according to technical solutions 1 to 4, the above-mentioned arithmetic processing unit, the above-mentioned communication unit and the above-mentioned storage unit are integrally disposed in the same housing as the position detector.

[0030] The hydraulic device with a position detector according to technical solution 6 is, in any one of technical solutions 1 to 4, the aforementioned processing unit, the aforementioned communication unit, and the aforementioned storage unit are disposed on the main body housing side of the hydraulic device.

[0031] The effects of the invention

[0032] In the hydraulic device with position detector of the present invention, since it has a storage unit that readablely stores the characteristic information of the hydraulic device in advance, the servo amplifier that drives and controls the hydraulic device can read out the required characteristic information through a communication connection, and the origin correction of the hydraulic device and the position detector and the optimization of the flow characteristics can be easily performed based on the characteristic information. Therefore, it has the effect of simplification in the adjustment process during manufacturing and in the adjustment process when combined with the machine tool on site. Attached Figure Description

[0033] Figure 1 This is a schematic structural diagram of a hydraulic linear servo valve of a hydraulic device with a position detector, which is a first embodiment of the present invention, in the state of servo amplifier connection.

[0034] Figure 2 It means to Figure 1 The flowchart shows the operation of the hydraulic linear servo valve after it is connected to the servo amplifier.

[0035] Figure 3 This is a schematic structural diagram of a hydraulic linear servo valve of a hydraulic device with a position detector, which is a second embodiment of the present invention, in the state of servo amplifier connection.

[0036] Figure 4 This is a line graph showing an example of the flow characteristics (horizontal axis: relative to the input signal, vertical axis: pressure oil flow rate L / min) of a hydraulic servo valve varying between large and small flow rates.

[0037] Figure 5 This is a line graph showing an example of the flow characteristics (horizontal axis: relative to input signal %, vertical axis: pressure oil flow rate L / min) of a hydraulic servo valve suitable for an injection molding machine.

[0038] Figure 6 This is a line graph showing an example of the linearity and continuity of the flow characteristics (horizontal axis: relative to the input signal, vertical axis: rated flow rate L / min) of a hydraulic servo valve near its zero crossing.

[0039] Figure 7 This is a control block diagram representing the feedback control operation process of the hydraulic equipment in the servo amplifier.

[0040] Figure 8 This is a schematic diagram showing an example of a conventional proportional electromagnetic directional flow control valve and a servo amplifier. (a) is a hydraulic diagram showing the outline structure of the directional flow control valve, and (b) is a circuit diagram showing the connection state with the servo amplifier.

[0041] Figure 9 This is a schematic diagram of the conventional valve position detector (LVDT).

[0042] Figure 10 It means Figure 8 A line graph showing the characteristics of a directional flow control valve relative to the flow command signal (horizontal axis: input voltage VDC) (vertical axis: pressure oil flow rate L / min). Detailed Implementation

[0043] In order to implement the invention

[0044] The hydraulic device with a position detector of the present invention is a hydraulic device driven and controlled by a servo amplifier in response to a command signal. It integrally includes a position detector that generates an output signal corresponding to the position of a valve member that determines the valve opening and the direction of working oil flow. The servo amplifier performs feedback control based on the deviation between the command value of the command signal and the position detection value based on the output signal. The device includes a processing unit, a communication unit, and a storage unit. The processing unit processes the output from the position detector and outputs the position detection value as a detection signal. The communication unit transmits the detection signal to the servo amplifier and receives signals from the servo amplifier. The storage unit readable by the communication unit stores characteristic information of the hydraulic device. This characteristic information includes at least correction information and flow characteristic information. The correction information is obtained by prior measurement on a test bench during the manufacturing process of the hydraulic device, ensuring that the position detection value obtained by the position detector corresponds to the characteristic value of the hydraulic device. The flow characteristic information is the flow rate of the hydraulic device relative to the command signal, corresponding to the command signal.

[0045] Based on the above structure, since any servo amplifier can read the calibration information of the position detector corresponding to the position detection value and the characteristic value of the hydraulic equipment from the storage unit, the origin correction based on this characteristic information can be performed by the servo amplifier without performing precise adjustment work to align the origin of the hydraulic equipment's control mechanism and the position detector during pre-manufacturing. Therefore, for example, when mounting the LVDT position detector on the valve stem end of the hydraulic servo valve, it is no longer necessary to adjust the assembly position of the position detector and fine-tune the core assembly length by manually tightening screws while observing the flow rate of the working oil after actual power-on. The position detector only needs to be fixedly installed, thus greatly simplifying the manufacturing process.

[0046] Furthermore, in this invention, since the flow characteristic information relative to the command signal can be read from the storage unit via the communication unit by any servo amplifier, there is no need to make adjustments on-site by the test run of the machine tool. The servo amplifier can perform control suitable for the inherent characteristics of the hydraulic equipment.

[0047] For example, based on the read flow characteristic information, the amplifier can control the elimination of the neutral insensitivity region observed in the flow characteristics of the hydraulic equipment, effectively linearizing the flow characteristics relative to the command signal. Therefore, control that takes into account the valve characteristics of the hydraulic equipment is no longer required during system adjustments.

[0048] Furthermore, in cases where improved control precision of the hydraulic cylinder is desired, a hydraulic servo valve with a zero-obstruction structure, exhibiting flow at both ports P→A and P→B even at the zero position of the valve column, is employed. However, this results in significant energy loss because hydraulic pressure often leaks out when the hydraulic cylinder stops. Therefore, in machine tools where speed control of the hydraulic cylinder is paramount and control precision at the zero position of the valve column is not critical, a hydraulic servo valve with an overlapping structure is used, where flow exits from a position that has undergone some degree of displacement without flow at the zero position of the valve column. In this overlapping structure, products with an adjustment mechanism function as a servo amplifier, which displaces the valve column to the overlapping end when the speed command signal changes from zero to the minimum speed, causing the hydraulic cylinder to operate at minimum speed. However, because there is a deviation from the specified displacement at the overlapping end of the valve column, adjustments were previously required while simultaneously monitoring the hydraulic cylinder's operation during machine startup and when replacing the hydraulic servo valve. In contrast, in this invention, since such complicated adjustment work is not performed, the same state as after adjustment can be obtained simply by having the servo amplifier read the flow characteristic information of the hydraulic servo valve from the storage unit. Therefore, it can be easily put into practical use in a short time when the machine is started or when the hydraulic servo valve is replaced.

[0049] In addition, in the case of a machine tool that performs speed feedback control of hydraulic cylinders, the flow characteristics of the hydraulic servo valve are as follows: Figure 4 As shown, if the flow characteristics of a hydraulic servo valve vary greatly between high and low flow rates, the flow gain changes drastically near the point of flow change, leading to instability in the feedback control of the hydraulic cylinder. In this invention, because the servo amplifier can read flow characteristic information, including such a point of change, from its storage unit, it can also adjust the flow gain near the point of change based on this characteristic information to prevent drastic changes.

[0050] Furthermore, based on the different flow characteristics and control actions derived from the type and operation category of the target machine, a hydraulic device corresponding to the target machine is selected. This hydraulic device contains a control program suitable for its own control. Using this control program, the servo amplifier can appropriately drive and control the hydraulic device. In the hydraulic device of this invention, by pre-storing the control program and control constants in a storage unit, when loaded into the actual machine, the servo amplifier connected to the hydraulic device can read the control program and control constants of the hydraulic device via a communication device. Therefore, if the hydraulic device has the control program in its storage unit, since the servo amplifier can also be used with various specially designed hydraulic devices that do not store control programs in the amplifier itself, it is not necessary to prepare dedicated servo amplifiers for each hydraulic device in pairs.

[0051] For example, when the hydraulic cylinder of the main machine is used in an injection molding machine, hydraulic equipment designed to suit the flow characteristics of that injection molding machine is selected for combination. However, the control accuracy near the zero crossing of the valve column is not important. Depending on the type of operation of the main machine, the system switches between controlling the hydraulic pressure equivalent to the output load of the hydraulic cylinder or controlling the flow rate equivalent to the speed of the hydraulic cylinder. Therefore, as Figure 5 As shown, because there is a point of change in flow characteristics in the middle of the valve stem's displacement range, the hydraulic device is appropriately driven and controlled by a control program that increases the valve stem displacement control gain in order to improve reproducibility and suppress interference at this intermediate point of change. Therefore, by pre-storing this control program in the hydraulic device's storage unit, even a servo amplifier that does not have the control program can read the control program from the hydraulic device's storage unit and perform appropriate drive control of the hydraulic device.

[0052] Furthermore, in hydraulic equipment where position control of the hydraulic cylinder is critical, a 4-port (A, P, B, T) configuration is preferred, such as... Figure 6As shown, because the linearity and continuity near the zero crossings where both port P→A and port P→B flow are zero have a significant impact on the performance of the machine tool, a control program is used to improve the valve control accuracy by using the hydraulic servo valve drive current near the zero crossings to counteract the driving forces in the P→A and P→B directions. If the control program is pre-stored in the storage unit of the hydraulic equipment, even a servo amplifier without pre-stored control program can read the control program from the storage unit to perform appropriate drive control of the hydraulic equipment.

[0053] As described above, if the control program and control constants suitable for the hydraulic equipment are stored in the storage unit, the servo amplifier can read the control program and control constants from the storage unit when connected to the hydraulic equipment and use them for the drive control of the hydraulic equipment. Therefore, without integrating the hydraulic equipment and the servo amplifier as a pair or directly mounting them during the manufacturing process, the same level of simplicity can be achieved in the adjustment process when installing them into the mother machine.

[0054] Furthermore, even if only the servo amplifier fails after prolonged use in the mainframe, a newly connected servo amplifier can still read the flow characteristics, control program, and control constants—the characteristic information of the hydraulic equipment—so it is not necessary to replace the hydraulic equipment as a pair; only the servo amplifier needs to be replaced. Additionally, even when changing hydraulic equipment, if the characteristic information is readablely stored in the storage section of the new hydraulic equipment, the existing servo amplifier can read the new hydraulic equipment's characteristic information to make it suitable.

[0055] Furthermore, the control programs and control constants are associated with numbers assigned according to the appropriate category of hydraulic equipment, simplifying the management of reading and rewriting the corresponding control programs and control constants according to these numbers. For example, since it is also possible that the control programs for various hydraulic equipment are already stored in the servo amplifier integrated with the target machine along with the hydraulic equipment, if the number is first read from the storage unit and the corresponding number is already stored in the servo amplifier, the servo amplifier can select and use its own stored control program. Moreover, if the target hydraulic equipment is specially designed and its control program number does not match the stored one, the servo amplifier only needs to read its specific control program from the hydraulic equipment's storage unit. In addition, the control constants stored in the storage unit along with the control programs can be either set within the program or processed separately.

[0056] The servo amplifier, in response to the command signal, provides feedback control of the hydraulic equipment's control mechanism based on the deviation between its command value and the position detection value from the position detector. In this case, such as... Figure 7As shown, firstly, to ensure consistency between the command value CV and the position detection value DV, a deviation is obtained by performing correction calculations on each value separately. At this point, there are constant coefficients for the zero-span correction calculation (CZc-CSc, DZc-DSc), and then constant coefficients for the respective filtering processes (CFc, DFc) are needed. Next, the deviation from these corrected command values ​​and position detection values ​​is calculated using the constant coefficients of PID control (proportional coefficient Pc, integral coefficient Ic, derivative coefficient Dc) to determine the control command value CCV for the drive current. The drive current also undergoes the same feedback control calculation to determine the control command value sent to the drive current control mechanism.

[0057] In this invention, by pre-storing values ​​related to control compensation, such as PID control constants, in the storage unit, the servo amplifier can read the coefficient constants required for feedback control, update the coefficient values ​​in the control compensation calculation program, and achieve optimal control of the hydraulic equipment. Furthermore, when the design of the hydraulic equipment is changed, or when replacing it with a new specially designed hydraulic equipment, the servo amplifier can be updated simply by changing the coefficient values ​​in the storage unit, eliminating the need to replace or readjust the servo amplifier itself, thus improving convenience.

[0058] Furthermore, in this invention, if an abnormality detection current setting value is further stored in the storage unit, the servo amplifier compares this abnormality detection current setting value read during connection with the drive current measurement value measured at each start-up of the machine tool equipped with hydraulic equipment. If an overcurrent exceeding the current setting value is detected, a warning signal can be output. If this warning signal is generated just before the next actual use of the machine tool, the user can easily grasp the abnormal state before actual use. Therefore, since maintenance of the valve mechanism or replacement of parts is possible, operation of the machine tool in an abnormal state can be avoided.

[0059] The measurement of the drive current for each start-up of the machine tool can be achieved by automatically moving the valve stem at a certain speed across its entire range of motion each time the servo amplifier starts, and then measuring the valve stem drive current at multiple points. Typically, when starting the machine tool's hydraulic system, the servo amplifier's power is connected in advance. Therefore, even if the valve stem position of the hydraulic equipment changes immediately after the servo amplifier's power is connected, the machine tool will not move. Furthermore, by inputting signals such as hydraulic disconnection to the servo amplifier, it is easy to create a problem-free condition even if the valve stem position of the hydraulic equipment changes. The current setting value for abnormal detection can be set to an overcurrent value slightly lower than the threshold value considered abnormal for the drive current of the hydraulic equipment. If foreign objects accumulate between the valve stem and the bushing, or become stuck, making valve stem displacement difficult, resulting in an overcurrent exceeding the above current setting value, the servo amplifier can output a warning signal based on this.

[0060] Furthermore, the storage unit of the present invention has the following functions: before the hydraulic equipment leaves the factory, the valve component is moved, the measured drive current value is stored as the initial value of the drive current, the measured value of the drive current at each start-up of the machine is stored, and the data is accumulated over time. Therefore, the servo amplifier can anticipate the time when the abnormality detection current set value will be reached based on the change in the initial value of the drive current over time, and can output a warning signal when that time is known or before it is about to be reached. The user can use the warning signal to understand the lifespan and potential failure of nearby valve mechanisms, and can prepare for maintenance or replacement in advance. Furthermore, by comparing the measured value with the previous value, in the event of a rapid change in the current value, the structure for outputting a warning signal can also indicate the possibility of certain adverse conditions occurring.

[0061] Furthermore, the position detection process for valve components such as valve stems is the same as before: the analog signal output from the position detector is digitized by an A / D converter, the digital signal is processed to obtain a digital detection signal, and the position detection value is sent to the servo amplifier via a communication unit. Therefore, the communication unit of the present invention only needs to be able to receive and transmit digital communication with the servo amplifier, and preferably it is made to have the function of receiving and transmitting high-speed digital communication and long-distance transmission. For example, an industrial fieldbus communication system or an industrial Ethernet communication system can be used for the communication connection between the servo amplifier and the hydraulic equipment, as long as the distance and environment between the actual servo amplifier and the machine-side hydraulic equipment are appropriately set.

[0062] Furthermore, the storage unit of this invention can be a rewritable non-volatile memory, and the arithmetic processing unit can be a digital signal processing IC such as a CPU, DSP, or FPGA. Therefore, the digital communication functions required by the communication device are the transmission of position detection signals from the arithmetic processing unit, the transmission of read values ​​from the non-volatile memory, the reception of write values ​​to the non-volatile memory, and the transmission and reception of check codes for detecting the correctness of communication.

[0063] Furthermore, in this invention, the processing unit, storage unit, and communication unit, other than the position detector directly mounted on the valve component, can be structures located near the position detector or structures located away from the position detector on the main body of the hydraulic equipment. For example, when integrated with the position detector within the same housing, the position detection device can be manufactured in advance in a consolidated form, allowing for easy installation on various hydraulic equipment. Additionally, by placing it on the position detector side, the number of parts in the hydraulic equipment is reduced, simplifying assembly during manufacturing. However, depending on the type of hydraulic equipment and position detector, the position detection device may also be designed to accommodate situations requiring a housing design consistent with the hydraulic equipment or a shape design suitable for the mounting portion on the hydraulic equipment side.

[0064] On the other hand, when the processing unit, storage unit, and communication unit are arranged separately from the position detector on the main housing side of the hydraulic equipment, the sensor amplifier can be integrated into a simple box-shaped housing regardless of the shape of the hydraulic equipment itself. This allows for placement in any location within the main housing of the hydraulic equipment that is easy to install and has ample space. In particular, the shape of the position detector varies depending on factors such as the detectable displacement length and the required pressure resistance (e.g., in the case of a hydraulic flow-to-core configuration in an LVDT), resulting in different external dimensions. Therefore, it is not necessary to consider the external shape of the sensor amplifier side, which is separate from the position detector. This provides a high degree of design freedom for the hydraulic equipment body, position detector, and sensor amplifier.

[0065] However, the sensor amplifier separated from the position detector, because it is manufactured and installed during the production of hydraulic equipment, also requires a protective structure for the weak analog signal wiring output from the position detector. This increases the number of components and manufacturing steps for hydraulic equipment. Therefore, the choice between either an integrated position detection device mounted on the hydraulic equipment as a position detection unit on the position detector side, or a separate sensor amplifier configured on the main body of the hydraulic equipment, depends on the specific hydraulic equipment being designed.

[0066] Example 1

[0067] Figure 1 This is a schematic structural diagram of a direct-acting hydraulic linear servo valve 1 connected to a servo amplifier 30. This direct-acting hydraulic linear servo valve 1 is a hydraulic device with a position detector as a first embodiment of the present invention. The position detection device 10 is installed at the end of the valve body 2. The position detection device 10 has a storage section that stores characteristic information of the hydraulic device and an LVDT that serves as a position detector 11, all within the same housing.

[0068] The hydraulic linear servo valve 1 of this embodiment consists of a generally cylindrical valve body 2, a linear motor 5, and a position detection device 10. The valve body 2 consists of a sleeve 3, a valve stem 4 sliding within the sleeve 3, and four ports (P, A, B, T). When the valve stem 4 is at the neutral point, these ports (P, A, B, T) are closed. If the valve stem 4 is displaced from the neutral point, the ports open accordingly with the amount of displacement, thus creating a zero-obstruction structure for the flow of pressurized oil.

[0069] The linear motor unit 5 is composed of a voice coil motor and is supplied with a command signal C from the servo amplifier 30. S The movable coil 7 with the corresponding driving current DI reciprocates within the magnetic field generated by the neodymium, iron and boron rare earth permanent magnet 6, thereby directly driving the valve stem 4 connected to the movable coil 7.

[0070] In the position detection device 10, an LVDT (Low-Level Dynamic Disk Detector) for a valve stem position detector 11, which is non-contact and highly responsive, is installed at the end of the valve stem 4. Specifically, a core 13 is fixed to the front end of a rod 12 extending from the valve stem 4. A tube member 14, through which the core 13 is inserted, protrudes from the side of the valve body 2 housing. A detection coil is formed around the tube member 14 by a primary coil 15 wound in the center and a pair of secondary coils 16 symmetrically wound on either side. The differential voltage between the secondary coils 16, whose position changes accordingly with the position of the core 13 within the detection coil that moves with the valve stem 4, is output relative to the primary coil 15, which has undergone one excitation. This analog signal output by the voltage is digitized by the A / D converter 17 and then processed by the arithmetic processing unit 18 to obtain a digital detection signal as the position detection value. The obtained position detection signal is transmitted from the communication unit 20 via high-speed digital communication to the communication unit 31 of the servo amplifier 30 (described later).

[0071] Furthermore, in the position detection device 10 of this embodiment, a storage unit 19 composed of a non-volatile memory is provided. In this storage unit 19, characteristic information of the hydraulic linear servo valve 1 can be readablely stored, and control programs and control constants suitable for the hydraulic linear servo valve 1 can be read out and rewritten by assigning numbers. That is, the position detection device 10 integrates the position detector (LVDT) 11, A / D converter 17, D / A converter 21, arithmetic processing unit 18, storage unit 19 and communication unit 20 into a single housing.

[0072] If the servo amplifier 30 is connected to the hydraulic linear servo valve 1 for startup, it only needs to have a built-in communication unit 31 that establishes a high-speed digital communication connection with the communication unit 20 of the position detection device 10. Furthermore, as always, it includes a processing unit 32, which is based on the command signal C from the controller on the host machine side. SThe control command value is calculated based on the deviation from the detection signal fed back from the position detection device 10, and the current supplied to the linear motor unit 5 is controlled accordingly. In this arithmetic processing unit 32, when communicating with the position detection device 10, the characteristic information of the hydraulic linear servo valve 1 can be read from the storage unit 19 via the communication devices 31 and 20. Therefore, the control program, control constants, flow characteristics, etc., suitable for hydraulic equipment contained in the characteristic information can be used to easily and appropriately control the linear motor unit 5. In addition, the servo amplifier 30 may also store control programs with the numbers of various hydraulic equipment that have been previously read into the amplifier memory 35.

[0073] The following are examples of specific characteristic information stored in storage unit 19.

[0074] (1) Model and manufacturing number of the position detector (LVDT in this embodiment).

[0075] (2) Calibration value of position detector (used only during manufacturing inspection of position detector)

[0076] (3) Model and manufacturing number of the hydraulic equipment (in this embodiment, a linear servo valve).

[0077] (4) Control program number suitable for hydraulic equipment

[0078] (5)(4) control program binary code

[0079] (6) The control constant best suited for hydraulic equipment

[0080] (7) Flow rate values ​​relative to position detection values ​​measured during the manufacturing inspection of hydraulic equipment (calibration information) and flow rate relative to command signals (flow characteristic information).

[0081] (8) The initial value of the drive current and the set value of the current for abnormal detection relative to the position detection value measured by moving the valve stem at a certain speed during the manufacturing inspection of the hydraulic equipment (drive current characteristic information).

[0082] (9) Drive time and number of starts of the hydraulic mechanism

[0083] (10) The drive current value for position detection, measured relative to the elapsed time of each start-up of the hydraulic equipment and the movement of the valve stem at a certain speed (for anticipatory diagnosis).

[0084] The adjustment process performed during the manufacturing of the hydraulic linear servo valve 1 with position detection device 10 in this embodiment can be listed as follows. First, in the position detection device 10, the model and manufacturing number of the LVDT (Leveled Low-Voltage Detector) that serves as the position detector 11, as well as the effective displacement range of that model, are pre-stored in the storage unit 19. Furthermore, cores 13 are arranged at the mechanical neutral point and rated displacement point of the LVDT, and adjustment data is pre-stored in the storage unit 19 by outputting digital signals at each point. Additionally, the model and manufacturing number of the hydraulic linear servo valve 1 on which the position detection device 10 is installed are also stored in the storage unit 19.

[0085] On the other hand, when the position detection device 10 is installed on the hydraulic linear servo valve 1, the body of the LVDT 11 and the valve stem 4 are assembled in the sleeve 3 of the valve body 2 in such a way that the neutral point of the valve mechanism where the valve stem 4 is located and the mechanical neutral point of the LVDT are aligned. After assembly, while moving the valve stem 4 using a test amplifier, the valve flow rate relative to the position detection value output by the displacement position of the LVDT core is measured. The position detection value of the neutral point for switching the valve's outlet port and the position detection value of the rated flow rate for each port are stored in the storage unit 19. The flow characteristics relative to this position detection value are used as correction information in the origin calibration performed by the servo amplifier 30 before actual use, eliminating the need for precise fine-tuning of the LVDT's installation position.

[0086] Furthermore, based on the measurement results, a coefficient for the flow rate relative to the position detection value is calculated. The location where this coefficient changes significantly is determined as an inherent change point for the hydraulic linear servo valve 1, and the position detection value and coefficient corresponding to each change point are stored in the storage unit 19. Additionally, the drive current value relative to the position detection value is measured, and its drive current characteristics are also stored in the storage unit 19. This drive current characteristic is used as a reference for future predictive diagnostics. Furthermore, before leaving the factory, the storage unit 19 also stores, with assigned numbers, control programs and control constants suitable for the hydraulic linear servo valve 1.

[0087] Next, the hydraulic linear servo valve 1 of this embodiment is connected to the servo amplifier 30, and the operation of the servo amplifier 30 after startup is... Figure 2 The flowchart is shown below. First, if the servo amplifier 30 is started, a communication connection is established with the position detection device 10 (S100).

[0088] In this communication connection state, the model and manufacturing number of the position detector are read from the storage unit 19 via the communication units 20 and 31 (S101), and a suitability determination of the model and manufacturing number is performed (S102). If it is not suitable, a warning signal is output and the start-up of the servo amplifier 30 is stopped (S103). If it is determined to be suitable, the model and manufacturing number of the hydraulic equipment (hydraulic linear servo valve 1) are read from the storage unit 19 (S104), and a suitability determination of the model and manufacturing number is performed (S105). If it is not suitable, a warning signal is output and the start-up of the servo amplifier 30 is stopped (S106). If it is determined to be suitable, the control program number is read from the storage unit 19 (S107). A determination is made as to whether the number is abnormal or normal (S108). If it is determined to be an abnormal number, a warning signal is output and the start-up of the servo amplifier 30 is stopped (S109).

[0089] If the control program number is determined to be normal, a determination is made as to whether the control program corresponding to that number is suitable or special (S110). That is, the control program number is used to determine whether it is suitable for one of the control programs already stored in the amplifier memory 35 of the servo amplifier 30, or whether it is a special control program that does not exist in the amplifier memory 35. If the control program number indicates that a suitable control program already exists, then the control program with that number is selected from the amplifier memory 35 in the servo amplifier 30 (S111).

[0090] On the other hand, if the control program is determined to be a special control program based on its number (S110), the binary code of the (5) control program is read from the storage unit 19, and the range of the amplifier memory 35 configuring the control program is rewritten (S120). After the control program is specified in the above process, its optimal control constant is read out and the control program constant is rewritten (S112). Next, the flow characteristic information of the (7) hydraulic equipment during manufacturing inspection from the storage unit 19 is read out and the target value correction curve relative to the position of the command value CV to the servo amplifier 30 is updated (S113).

[0091] Then, the drive current characteristic information (8) is read from the storage unit 19, and the drive current is measured to autonomously drive the linear motor unit 5 to move the valve stem 4 at a certain speed throughout the entire operating range (S114). Then, a diagnostic judgment is performed (S115), which compares the overcurrent setting value, which is the current setting value for abnormality detection included in the read drive current characteristics, with the measured drive current value. If an abnormality is diagnosed, a warning signal is output (S116). The user can determine from the warning signal that the valve mechanism of the hydraulic linear servo valve 1 is in a malfunctioning state, and perform specific inspections, repairs, and replacement of parts.

[0092] If the diagnosis is normal, the drive elapsed time and number of starts of the hydraulic equipment up to the last time (9) and the elapsed time of each start of the hydraulic equipment up to the last time (10) and the position detection value measured by moving the valve column at a certain speed are read from the storage unit 19. The number of starts is updated, and the measurement results of the drive current value performed in step S114 are stored and accumulated (S117). Here, the change of the initial value of the drive current as a characteristic of the drive current over time can also be updated, and the period when the abnormal drive current value will arrive can be predicted based on the extension of its rate of change and the detection of large change points. Then, according to the control program optimized by rewriting the control constant, normal drive control relative to the hydraulic linear servo valve 1 is performed in accordance with the command signal from the controller on the machine side (S118). When the power supply to the servo amplifier 30 is cut off after the normal operation ends, the power of the storage unit inside the amplifier is used to communicate with the position detector 10 and send a digital signal of the elapsed time of this start. The drive elapsed time and number of starts are updated by the storage unit 19 (S119).

[0093] As described above, in the hydraulic linear servo valve 1 of this embodiment, since any servo amplifier can easily read the characteristic information of the hydraulic equipment pre-stored in the storage unit 19 for adjustment, there is no need for a precise adjustment process during manufacturing, nor is there a need for an adjustment process that is performed while the machine is being tested on-site, thus achieving excellent simplicity.

[0094] In the first embodiment described above, a structure is shown in which the equipment required to output analog signals from the position detector 11 and from the digitization of the analog signals to the output of detection signals, including the storage unit 19, is arranged in the same housing as the position detector 11 as a position detection device 10. However, the present invention is not limited to this, and a configuration in which the position detector 11 and other equipment are separated may also be performed.

[0095] Therefore, as a second embodiment of the present invention, Figure 3This is a schematic structural diagram of a hydraulic linear servo valve 51 with the following structure, showing its connection state with the servo amplifier 30. The hydraulic linear servo valve 51 has a storage unit storing characteristic information of the hydraulic equipment and a position detector mounted separately on the housing side of the valve body of the hydraulic equipment. In this embodiment, the storage unit 73 is the main component. A sensor amplifier 70, which houses devices other than the position detector disposed in the position detection device 10 in the first embodiment, is mounted on the housing side of the valve body 52. ​​Otherwise, the structure of the valve body 52 is similar to... Figure 1 The structure of the valve body 2 is the same.

[0096] That is, the valve body 52 of the hydraulic linear servo valve 51 in this embodiment is generally cylindrical in shape, with a linear motor 55 on one end and an LVDT as a position detector 61 on the other end. It is composed of a sleeve 53, a valve stem 54 that slides in the sleeve 53, and four ports (P, A, B, T), and has a zero-obstruction structure.

[0097] The linear motor unit 55 receives the command signal C from the servo amplifier 30 via the movable coil 57 of its voice coil motor. S The corresponding drive current DI reciprocates within the magnetic field of the permanent magnet 56 to directly drive the linear motor section of the valve column 54.

[0098] The LVDT, serving as the position detector 61, has a core 63 fixed to the front end of a rod 62 extending from the valve stem 54, and can reciprocate inside a tube member 64 protruding from the side of the valve body 52. ​​In this embodiment, a weak analog signal wiring 60 extending out of the housing of the position detector 61 is arranged from a primary coil 65 forming a detection coil at the center of the outer periphery of the tube member 64 and a pair of secondary coils 66 on either side thereof to the sensor amplifier 70.

[0099] In the LVDT, relative to the primary coil 65 which has undergone one excitation, an analog signal outputting the differential voltage between the secondary coil 66, which is the detection coil whose core 63 changes position accordingly as it moves along with the valve stem 54, is sent to the sensor amplifier 70 via the weak analog signal wiring 60. After being digitized by the A / D converter 71, it is processed by the arithmetic processing unit 72 to obtain a digital detection signal as the position detection value. The obtained position detection signal is sent from the communication unit 74 to the communication unit 31 of the servo amplifier 30 via high-speed digital communication. In addition, the sensor amplifier 70 has a storage unit 73 inside its housing, which stores characteristic information (1) to (10) related to the hydraulic linear servo valve 51.

[0100] As in this embodiment, when the A / D converter 71, D / A converter 75, arithmetic processing unit 72, storage unit 73, and communication unit 74 are installed as a sensor amplifier 70 separate from the position detector 61 and mounted on the main body housing side of the hydraulic equipment, the individual sensor amplifier 70 can be easily adapted to the installation of hydraulic equipment with various external shapes. Therefore, as a result, the design freedom of the hydraulic equipment body, position detector, and sensor amplifier is increased.

[0101] In addition, in this embodiment, the sensor amplifier 70 and the position detector 61 are configured separately, but are started by connecting the servo amplifier 30. After establishing a high-speed digital communication connection between the sensor amplifier 70 and the servo amplifier 30 via the communication devices 74 and 31, it can be operated in the same manner as in the first embodiment. Figure 2 The actions shown.

[0102] Furthermore, the above embodiments illustrate a hydraulic device equipped with an LVDT as a position detector, but the present invention is not limited thereto. It goes without saying that the same principle applies even when other magnetic, optical, or magnetostrictive sensors capable of detecting the position of valve components are installed.

[0103] Explanation of symbols

[0104] 1.51: Hydraulic linear servo valve

[0105] 2.52: Valve body

[0106] 3, 53: Casing

[0107] 4, 54, 201: Valve column

[0108] 5, 55: Linear motor section

[0109] 6, 56: Permanent magnets

[0110] 7, 57: Movable coil

[0111] 10: Position detection device

[0112] 11, 61: Position Detector (LVDT)

[0113] 12, 62, 202: poles

[0114] 13, 63, 203: core

[0115] 14, 64, 204: Pipe components

[0116] 15, 65, 205: Primary coil

[0117] 16, 66, 206: Secondary coils

[0118] 17, 33, 71: A / D converter

[0119] 18, 72: Computation and Processing Unit

[0120] 19, 73: Storage Department

[0121] 20, 74: Communication equipment

[0122] 21, 34, 75: D / A converter

[0123] 30, 300: Servo amplifiers

[0124] 31: Communication equipment

[0125] 32: Computation and Processing Unit

[0126] 35: Amplifier Memory

[0127] 60: Weak analog signal wiring

[0128] 70: Sensor Amplifier

[0129] 200: Proportional electromagnetic directional flow control valve

[0130] 210: Screw Construction

[0131] 220: Adjusting spring

[0132] 230: Nut.

Claims

1. A hydraulic device with a position detector, which is a hydraulic device driven and controlled by a servo amplifier in response to a command signal, integrally provided with a position detector that generates an output signal corresponding to the position of a valve member that determines the valve opening degree and the working oil flow direction, and which performs feedback control by the servo amplifier based on the difference between the command value of the command signal and the position detection value based on the output signal, characterized by comprising: an arithmetic processing unit that performs arithmetic processing on the output from the position detector and outputs the position detection value as a detection signal; a communication device that transmits the detection signal to the servo amplifier and receives a signal from the servo amplifier; and a storage unit that stores characteristic information of the hydraulic device in a readable manner via the communication device.

2. The hydraulic device with a position detector according to claim 1, characterized in that the characteristic information of the hydraulic device stored in the storage unit further includes correction information and flow characteristic information in a rewritable manner, the correction information being correction information that makes the position detection value by the position detector correspond to the characteristic value of the hydraulic device, which is measured in advance in a test stand during the manufacturing process of the hydraulic device, and the flow characteristic information being flow characteristic information that makes the flow of the hydraulic device with respect to the command signal correspond to the command signal.

3. The hydraulic device with a position detector according to claim 1 or 2, characterized in that the storage unit further stores an abnormality detection current setting value for comparison with a drive current measurement value measured by moving the valve member at each start of a host machine into which the hydraulic device is incorporated.

4. The hydraulic device with a position detector according to claim 3, characterized in that the storage unit has a function of storing a drive current value measured by moving the valve member before shipment of the hydraulic device as a drive current initial value and storing the drive current measurement value at each start of the host machine to accumulate over time.

5. The hydraulic device with a position detector according to any one of claims 1 to 4, characterized in that the arithmetic processing unit, the communication device, and the storage unit are integrally provided in the same housing as the position detector.

6. The hydraulic device with a position detector according to any one of claims 1 to 4, characterized in that the arithmetic processing unit, the communication device, and the storage unit are provided on the side of the main housing of the hydraulic device. ​ ​ ​ ​ ​ ​ ​

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