JPS6219617B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a viscous load control device that utilizes changes in the viscosity of a magnetic fluid under the influence of a magnetic field. First, to explain the conventional method of speed control or synchronized travel, electro-hydraulic servo controls the flow rate using a four-way guide valve of a servo valve, and is suitable for obtaining large driving power.
A hydraulic power unit is required as a hydraulic power source, and the overall structure of the device becomes large-scale, resulting in high costs. In addition, there are problems such as the servo valve becoming clogged and malfunctioning due to dirt mixed in the hydraulic oil, so regular maintenance and inspections (flushing, filter treatment) are required to clean the hydraulic oil. I needed to maintain my sexuality. On the other hand, AC servos, DC servos, pulse motors, etc. are used as electric servo systems, but the disadvantage of electric systems is that they generate heat during overload.
There is a possibility of malfunction or fire, and caution must be taken to prevent explosions in explosive atmospheres.
It also had disadvantages, such as lower power than hydraulic systems. In addition, for example, in the case of a pulse motor, the mechanical part that uses a ball screw or the like to convert the output rotation axis into linear motion is expensive, requires dust-proof measures for the ball screw part, and also has the harsh high frequency range unique to pulse motors. Noise was also a problem. At present, there are few pneumatic systems that can be used as speed and positioning servos, and their compressibility makes precise control of flow rate difficult, so they are mostly used only for simple two-point positioning. be. Both systems have many problems in terms of cost, performance, maintenance, etc. when applied to synchronized running of conveyors in factories. An object of the present invention is to provide a viscous load control device that can be electrically controlled and can withstand large-power control, in place of these conventional methods, each of which has its own advantages and disadvantages. An embodiment of the present invention will be described below. FIG. 1 is a configuration diagram of a speed control actuator in one embodiment of the present invention. 1 is an air cylinder, 2 is a piston rod of air cylinder 1, 3 is a magnetic fluid cylinder, 4 is a piston rod of magnetic fluid cylinder 3, 4a is a piston, 5 is a left pressure chamber, 6 is a right pressure chamber, 7 is a control pipe, 8 is a solenoid, and 9 is a magnetic fluid filled in the pressure chambers 5, 6 and the control pipe 7. Here, magnetic fluid has fluidity, which is a characteristic of liquid, and alloys (solid) of iron, nickel, ferrite, etc.
It has both the properties of a magnetic material made from In the examples of the present invention, magnetite (FeO, Fe ₂ O ₃ ), which is a type of ferrite, was made into fine particles with a diameter of about 100 Å and dispersed in a solvent by the action of a surfactant. Now, in the apparatus shown in FIG. 1, a control pipe 7 is connected to the left and right pressure chambers 5 and 6 of the magnetic fluid cylinder 3, and by the movement of the piston rod 4 connected to the piston rod 2 of the air cylinder 1, The magnetic fluid 9 is configured to circulate between the left and right pressure chambers 5 and 6. The control pipe 7 is also provided with a solenoid 8 that controls the viscosity of the magnetic fluid 9. Now, as shown in Fig. 1, air is supplied to the air cylinder 1 at a constant supply pressure, and if a propulsive force: F is applied to the piston rod 2, the speed of the piston rod 4 will be reduced by the magnetic force flowing through the control pipe 7 in a steady state. It is determined by the viscous load caused by the fluid 9. That is, the speed of the piston rods 2 and 4 is V,
The diameter of the control pipe is d ₁ , the length of the control pipe is L,
If the inner diameter of the magnetic fluid cylinder 3 is d ₂ and the viscosity of the magnetic fluid 9 is μ, then the propulsive force of the air cylinder 1: F is balanced with the viscous load in a steady state, and F=R ₁ μ・V ……(1 ) However, R ₁ = 8πL (d ₂ /d ₁ ) ⁴ In a normal flow control valve, by making R ₁ variable, for example, the diameter of the orifice of the flow control valve placed in the fluid pipe: d ₁ can be changed. The flow rate (speed) is controlled by making it variable, but in this device, the above _R1 is kept constant, that is, without changing the pipe diameter (without mechanical operation). The magnetic fluid 9 is characterized in that the speed of the piston rod 4 is controlled by applying a magnetic field to the magnetic fluid 9 to make the viscosity μ variable. This focuses on the unique property of magnetic fluids, namely the ``apparent viscosity change'' of magnetic fluids that flow under the influence of a magnetic field. When the magnetic fluid flowing in the tube is affected by a magnetic field, rotational torque acts on the microparticles that have magnetic dipoles, and the dipoles try to align in the direction of the magnetic field, hindering the free rotation of the microparticles. This increases pipe friction resistance. That is, there is a phenomenon that causes an increase in apparent viscosity, and this device utilizes this property of magnetic fluid. Therefore, in FIG. 1, if the value of the current flowing through the solenoid 8 wound around the control pipe 7 is made variable, the axial magnetic field of the control pipe 7 changes, and the magnetic fluid 9 flowing through the control pipe 7 changes. The viscosity apparently increases or decreases. In other words, under constant conditions, the propulsive force F of the cylinder 1 caused by the constant air pressure source increases or decreases to the speed of the piston rods 2 and 4 as the viscous load increases or decreases. Now, the speed control actuator according to this method has the following characteristics. (1) Viscosity load and speed can be controlled with an extremely simple and low-cost configuration. Conventional flow control valves control the flow rate by making the opening area of the guide valve variable. However, for example, in the case of a four-way guide valve, in order to escape from the influence of the flow hose (static axial force) generated on the spool of the guide valve, complex and precise grooves are machined on the land end face to reduce the flow hose. It was necessary to take measures such as measuring the Furthermore, in the case of a servo valve, for example, it is made up of many precision parts, such as a torque motor comprising a nozzle flapper, a filter, a fixed orifice, a four-way guide valve, etc., resulting in high costs. In principle, this device only has a solenoid 8 placed in the axial direction on a control pipe 7 that connects the left and right pressure chambers, and there are no complicated or precise mechanical operating parts, making it possible to have an extremely simple configuration. did it. (2) Highly accurate viscous load and speed control is possible. Conventional servo valves and variable orifice flow control valves with mechanically actuated parts have a small amount of Coulomb friction in the actuating parts (such as the spool of the guide valve) that control the flow rate, as shown in Figure 2. , a dead band (hysteresis) exists between the input current and the output flow rate. The existence of this dead zone has been a factor leading to a decrease in output accuracy. FIG. 3 shows the magnetization characteristics of the magnetic fluid used in this device. The magnetization curve of magnetic fluid is not loop-shaped (with hysteresis) as is the case with ordinary ferromagnetic materials.
It is a straight line. In other words, super paramagnetism with extremely small residual magnetization: Br and coercive force: Hc
In Fig. 3,
Even if the magnetic field: H is replaced with the input current of the solenoid, the magnetization: B is replaced with the viscosity μ, or the viscous load: F, the same tendency is shown. However, even when H<O, the viscosity is μ>O and is symmetrical with respect to the y-axis. This device uses the above-mentioned unique properties of magnetic fluid to configure a speed control actuator.
There is no dead zone between the input current and the output (speed, viscous load), allowing highly accurate control. As described above, this device connects two pressure chambers of a cylinder containing magnetic fluid with a pipe, and controls the viscosity load and speed by varying the viscosity of the magnetic fluid flowing in the pipe using an external magnetic field. I have explained the basic idea. This actuator can be extremely effectively applied to a closed-loop controlled synchronous transfer device, which will be described below. FIG. 4 is a basic configuration diagram of a synchronous transfer device according to an embodiment, and FIG. 5 is a block diagram thereof. A transfer table 10 is connected to the piston rod 2 and runs on a rail 11. Reference numeral 12 denotes hangers provided at equal pitches on the conveyor 13, and are continuously moving parallel to the rail 11 at a constant speed. 14 is an input potentiometer that detects the hanger position, and 15 is an output potentiometer that detects the position of the transfer table 10. 16 is a semi-fixed orifice provided in the control pipe 7, 17 is a control device, 18 is a manipulator provided on the transfer table 10, and 19 is a workpiece to be transferred from the manipulator 18 to the hanger. The purpose of this synchronous transfer device is the manipulator 18.
By moving the transfer table 10 provided with the transfer table 10 in synchronization with the continuously operating conveyor 13, the workpiece 19 is loaded onto the hanger 12 by the manipulator 18. To achieve synchronous running, the variable parameters of the device are adjusted as follows. Assuming that the speed of the conveyor 13 is V ₀ , the speed of the transfer device without applying a magnetic field to the control pipe 7 is V ₁ , and the minimum possible speed with a magnetic field applied is V ₂ , the following conditions hold: Adjust the semi-fixed orifice 16:R so that the V ₂ <V ₀ <V ₁ ...(2) Then, within the range of equation (2), the speed of the transfer device can be freely controlled by the input electrical signal of the control device. Now, the hanger 12 to which the work 19 should be transferred
When the hanger 12 approaches, the input potentiometer 14 installed on the conveyor 13 detects the position of the hanger 12. Upon receiving a detection signal indicating the approach of the hanger 12, the transfer table 10 starts traveling on the rail. The control device is configured such that the larger the deviation signal (difference between conveyor displacement: y and transfer, table displacement: x, ε=y−x), the smaller the input current applied to the solenoid 8 becomes. Eventually, the deviation value |ε| becomes the allowable error range: ε
When it is detected that |ε|=ε _p for _p , the workpiece 19 is
will be transferred. By using the present actuator for closed loop control in this manner, the effects of the present invention can be extremely effectively obtained. For example, in addition to the effects of the present invention described above, (3) a speed control actuator with small residual speed deviation can be constructed. When a speed control actuator is constructed in a closed loop, the larger the open loop gain, the smaller the residual speed deviation (velocity droop), but the aforementioned dead zone of the flow control valve becomes a major restriction on the open loop gain. However, the present speed actuator, which essentially has a small dead zone, can have a sufficiently large open loop gain. For example, when a unit step speed input (obtained from the input potentiometer 14) becomes a setting signal for the control device 17 as in the case of the present transfer device, the residual speed deviation e _v of the output changes the open loop gain of the system. K _l and the speed of the conveyor 13 is V _p , then e _v = V _p /K _l ...(3) When attaching to an object moving at high speed, the above residual degree deviation becomes a big problem, but this device For the reasons mentioned above, since the open loop gain: K _l can be made sufficiently large, it is possible to improve the tracking performance. Now, an important issue for synchronous transfer devices is how to shorten the time required to reach synchronous travel. In order to achieve synchronous running in practice, it is first necessary to be able to adjust the speed of the transfer table 10 so that it has the same speed as the conveyor 13, and in addition, within a controllable range,
The key point is how large the difference in speed between the conveyor 13 and the transfer table 10 can be made. For example, in equation (2), the larger V ₁ is, the shorter the time required to reach synchronous running even if the transfer table 10 starts later than the conveyor 13. This is determined by how large a change in viscous load can be made due to the magnetic field (input current), but it has been confirmed that the tracking performance of this device can be improved by the following method. (i) Bypass circuit and main circuit (control pipe 7)
Install an ON-OFF type solenoid valve. In order to improve the performance of the synchronous transfer device (shorten the follow-up time), Figure 6 shows a bypass circuit 20 and an ON
- This is an example in which OFF type solenoid valves 21 and 22 are provided. A bypass circuit 20 provided in parallel with the control pipe 7 is provided to speed up the movement of the transfer table 10 when the deviation ε>ε _p . In other words, the input and output potentiometers 14, 1
When the deviation signal ε=y−x>ε _p of No. 5, the solenoid valves 21 and 29 are turned ON (open). Conversely, the solenoid valve 22 provided in the control pipe 7 has ε<-ε _p
, it becomes OFF (at this time, the solenoid valve 21 is
OFF), the circulation of the magnetic fluid 9 sealed in the magnetic fluid cylinder 3 in the left and right pressure chambers 5 and 6 is stopped, so the air cylinder 1 is locked and stops running. The operations of the solenoid valves 21 and 22 can be summarized as shown in Table 1.

[Table] By using the above method, even if the set speed V _p of the conveyor 13 to be followed changes significantly each time the present device is applied, the function of synchronous running can be sufficiently performed. In other words, conveyor 13, speed: V _p ,
It is sufficient to adjust the semi-fixed orifice 16 in advance so as to satisfy equation (2), which is the control range for proportional operation, and set the switching range ε _p so that it falls within the proportional operation range only for final precise control. Just do it. Furthermore, since the electromagnetic valves 21 and 22 are of a simple ON-OFF type, there is almost no problem with the simplicity of the configuration and cost of the device. (ii) Set each parameter within the range of 10 ^-8 <γoμo/MH < 10 ^-6 . Rosensweig et al. investigated the effect of the magnetic field on the viscosity of a magnetic fluid containing magnetite as a dispersoid by dimensional analysis (Journal of
Colloid and Interface Science VOL 29,
NO.4, April 1969, pages 680-686), the viscosity is γo
As defined by μo/MH, γoμ
It has been confirmed that the greatest viscosity dependence is obtained when o/MH is in the above range. Here, γo=shear rate, μo=viscosity of the dispersion, M=magnetization of the particles, H=magnetic field. For this device, each parameter (diameter of control pipe 7: d ₁ , inner diameter of magnetic fluid cylinder 3: d ₂ , magnetization characteristic of magnetic fluid 9) is determined by paying attention to the above phenomenon. That is, the range of the shear speed: γo is determined from the set range of the conveyor speed: Vo running in the factory, and furthermore, γoμo/MH is designed to fall within the above range. Under such conditions, it has been confirmed that the speed range of this speed control actuator can be changed by a factor of 3 to 4.
Normally, the conveyor speed running in the factory is V
_p = 15 cm to 35 cm/sec, which is well within the range where speed control is possible in this transfer device. Now, depending on the input current proportional to the deviation: i,
This device, which performs synchronous running by changing the apparent viscosity μ of the magnetic fluid, was able to find stable conditions for the system that are useful for design using the method described below.
The information below is provided for reference. If i' is the change in current proportional to deviation: ε=y-x and time delay: T, then K ₁ ε=i'+Tdi'/dt (4) io is used as a bypass current to actually supply solenoid 8. If the flowing input current is i, then K ₂ i=K ₂ (i _p −i')=μ (5) Also, for the propulsive force of air cylinder 1: F,
The following equation of motion holds true between the deviations ε. F=R ₁ (μo−μ) (V _p −dε/dt)−W/g d ² ε/dt ² (
6) In formula (5), W is the weight of the transfer table 10,
μo is the viscosity of the magnetic fluid when i=O, and this device is configured so that when the deviation ε becomes large, the input current i becomes small. From equations (4, 5, 6), linearize around the equilibrium point at t→∞ to find the stability condition: K ₁ K ₂ <F/V〓R ₁ (g/W F/V _p +1/T) (7
) From equation (6), for example, the time constant of solenoid 8:
It can be seen that the smaller T, the weight of the transfer table: W, the conveyor speed: _Vp , and the larger the propulsive force of the air cylinder 1: F, the more stable the present transfer device operates. Displacement of transfer table 10 when TO is >1:
X can be obtained as follows. Now, in the embodiment of the present invention, the parameters used in the synchronous transfer device are shown in Table 2 below.

[Table] Under the conditions of Table 2, conveyor speed: V
It can be seen that the synchronous transfer device that started with a delay of y _p =30 cm at _p = 30 cm/sec runs synchronously with the conveyor (deviation: εO) in an extremely short time, as shown in FIG. The magnetic fluid cylinder 3 used in the example is one used in ordinary hydraulic equipment. The pressure chambers are separated by a piston (partition plate) and a cylinder case (housing) that houses the piston, and the movement of the piston wall changes the volume of each pressure chamber. Furthermore, any shape or type of actuator or pipe can be used in the present invention as long as the working fluid confined in the pressure chamber is fed under pressure and the viscous load due to the flow of the working fluid is applied as a reaction force to the piston wall and piston rod 4. can. Alternatively, instead of two pressure chambers, a structure may be used in which the magnetic fluid is confined in only one pressure chamber and connected to a magnetic fluid tank via a flow path (such as a pipe). Fig. 8 shows another method of speed control, where 23 is an actuator, and by combining the air cylinder 1 and magnetic fluid cylinder 3 in Fig. 1, one cylinder can have the functions of the other. It is something. 24 is the piston rod, 25
is a piston, 26 is a compression spring, 27 is a control pipe, 28 is a solenoid, 29 is a magnetic fluid tank,
30 is a pipe. In FIG. 8, the left pressure chamber 31 is an air cylinder, and the piston 25 is moved by air pressure.
is given a force to move in the right direction (direction A),
Further, the compression spring 26 has the function of restoring the piston 25 in the left direction (direction B). The right pressure chamber 32 is filled with magnetic fluid 9,
The magnetic fluid 9 flows through the control pipe 27 as the volume of the right pressure chamber 32 changes due to the movement of the piston.
The speed can be controlled by applying a magnetic field to. In the structure of FIG. 8, what corresponds to the bypass circuit 20 described above is only required to connect the right pressure chamber 32 and the magnetic fluid tank 29, and the solenoid valve 21,
22. A valve corresponding to the semi-fixed flow rate control valve 16 may be provided in the bypass circuit and control pipe. In the embodiment, a direct-acting type cylinder 3 is used, but the present invention can be applied by connecting pressure chambers with a control pipe using, for example, a rotary type motor, pipes, or the like. The piston (partition plate) may have any shape, for example, a blade shape used in a rotary actuator.
In this embodiment, the air cylinder 1 is used as the actuator that provides driving force to the device, but hydraulic pressure,
Any method, air or electricity, may be used, for example,
Gravity itself may be used as the driving force. Further, in the embodiment, a magnetic field is applied in the axial direction of the flow path (pipe 7) through which the magnetic fluid 9 flows, but a magnetic field may be applied in the radial direction of the pipe 7. However, the dependence of viscosity on the magnitude of the magnetic field is reduced to approximately 1/2. Further, the flow path (control pipe 7 in the embodiment) connecting the pressure chambers may have any shape and may be provided at any location, and its flow resistance changes by applying a magnetic field. If the magnetic circuit and fluid path are configured in this way, the effects of the present invention can be obtained. In addition, the opening 31 of the magnetic fluid cylinder (the part where the piston rod 4 and the cylinder tube slide) is the only opening to the atmosphere in the structure shown in FIG. 1, for example, but the magnetic fluid 9 flows out to the outside. , is the only place where there is a possibility of leakage. If a magnetic seal using, for example, a permanent magnet is constructed in this portion by utilizing the attraction effect of the magnetic fluid 9 to the magnetic pole, leakage can be minimized. Listed above are the effects of the actuator of the present invention: It is electrically controllable, has no mechanically actuated parts, has an extremely simple and low-cost configuration, and can be applied to large amounts of power; current)
There is no hysteresis (dead zone) between output (velocity, displacement), high precision, and response speed is faster than those with mechanical moving parts. Furthermore, in the second invention, by using this device for closed-loop control, for example, by applying it to synchronous transfer of a conveyor, it is possible to obtain a larger open-loop gain than when using conventional electro-hydraulic servos, pulse motors, etc. It is possible to realize a transfer traveling device that has a small residual speed deviation, is extremely simple and low cost, and is easy to maintain. In addition, by providing a bias circuit in the flow path of this device or appropriately setting the parameters so that the viscosity dependence by the magnetic field is maximized,
Levels of performance can also be measured using methods such as increasing the proportional operating range.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a speed control actuator showing the basic principle of the present invention, Fig. 2 is a diagram showing the flow rate characteristics with respect to the input current of a conventional flow control valve, and Fig. 3 is the magnetization characteristics of the magnetic fluid used in the present invention. (or apparent viscosity change characteristics with respect to input current) diagram, 4th
The figure is a block diagram of a synchronous transfer device that is an embodiment of the present invention, FIG. 5 is a block diagram of the synchronous transfer device, FIG. 6 is a diagram showing its improvement, and FIG. 7 is a start-up of synchronous travel in the embodiment. FIG. 8, which is a diagram showing the characteristics, is a diagram showing another method of speed control according to the present invention. 1, 2... Actuator, 3... Cylinder, 4
a... Piston, 5, 6... Pressure chamber, 7... Flow path (control pipe), 8... Magnetic field generation source (solenoid), 9... Magnetic fluid, 15... Detection section (output potentiometer) , 16...Flow rate adjustment section (orifice), 17...Control device, 20...Bypass circuit, 21, 22...Flow rate control section (electromagnetic valve).

Claims (1)

[Claims] 1. A piston, a cylinder housing the piston, a pressure chamber formed by the piston and the cylinder, a magnetic fluid filled in the pressure chamber, and a magnetic fluid connected to the pressure chamber. and a flow path in which the magnetic fluid flows due to relative movement of the piston and the cylinder, and a magnetic field generation source applied to the magnetic fluid in the flow path, and a solenoid is used as the magnetic field generation source. . A viscous load control device, characterized in that the magnitude of the magnetic field is made variable depending on the current value applied to the solenoid. 2 Forming multiple pressure chambers before and after the piston,
The viscous load control device according to claim 1, characterized in that the pressure chambers are connected to each other through flow passages. 3. The viscous load control device according to claim 1, further comprising an actuator that provides relative movement between the piston and the cylinder. 4. The viscous load control device according to claim 1, characterized in that a semi-fixed flow rate adjustment section is provided in the flow path communicating between the pressure chambers. 5. The viscous load control device according to claim 1, characterized in that an ON-OFF type flow control section is used in the flow path that communicates between the pressure chambers. 6. A viscous load control device according to claim 1, characterized in that a bypass circuit is provided in a flow path that communicates between pressure chambers, and an ON-OFF type flow rate control section is provided in this bypass circuit. . 7 a piston, a cylinder housing the piston, a pressure chamber formed by the piston and the cylinder, a magnetic fluid filled in the pressure chamber, communicating with the pressure chamber, and connecting the piston and the cylinder; It consists of a flow path through which the magnetic fluid flows due to relative movement of cylinders, and a magnetic field generation source that is applied to the magnetic fluid in this flow path, and a solenoid is used as the magnetic field generation source, and the magnetic field is applied to the solenoid. The detection unit includes a control device that varies the magnitude of the magnetic field depending on a current value and further applies an input current to the solenoid, and a detection unit that detects a relative displacement or a change in displacement between the piston and the cylinder. A viscous load control device comprising a closed loop control system using the signal as a feedback signal for the control device.