JP4624038B2 - Liquid supply device - Google Patents

Description

  The present invention relates to a liquid supply device that supplies a liquid such as paint in a fixed amount.

  As a conventional liquid supply device, a configuration is known in which a piston of a piston pump is reciprocated via a drive mechanism by a pulse motor or a servo motor (for example, Patent Document 1). The liquid supply apparatus using such an electric actuator can perform positioning and speed control of the piston with high accuracy by using a ball screw or the like as a drive mechanism, and can perform a desired quantitative supply. However, since the allowable torque load is not so large, there is a problem that it is difficult to supply the liquid when the viscosity of the liquid is high or the flow path on the discharge side is long.

  On the other hand, an airless pump that reciprocates a piston by supplying driving air to an air motor is known as a liquid supply device that can maintain sufficient discharge performance even if a large load acts on the discharge side. (For example, patent document 2). As the air motor, a double-acting air cylinder is preferably used, and a high discharge pressure can be obtained by appropriately setting the ratio between the cross-sectional area of the air cylinder and the cross-sectional area of the piston pump. However, since the discharge pressure of the air motor is controlled by adjusting the supply pressure of the driving air, there is a problem that it is difficult to maintain the discharge flow rate with high accuracy against the load fluctuation on the discharge side. In addition to the above, a gear pump is also known as a pump capable of supplying high pressure. However, particularly in a liquid such as a low-viscosity paint, leakage is likely to occur from the gap between the gear and the housing, and it is difficult to quantitatively supply the pump. .

As the liquid supply device, the configuration disclosed in Patent Document 3 is known. In this liquid supply device, two pistons are arranged opposite to each other inside the housing of the suction pump, and the liquid is supplied by increasing / decreasing the volume of the pump chamber by individually controlling driving by two drive motors. be able to. However, the two drive motors used are both electric motors, and there is a problem that it is difficult to quantitatively supply the liquid when the viscosity of the liquid is high, as in the configuration of Patent Document 1.
JP 2001-113220 A JP-A-6-296907 JP-A-8-72266 (FIG. 6, paragraph [0086])

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a liquid supply device capable of quantitatively supplying a liquid with high accuracy regardless of the viscosity of the liquid and the load on the discharge side. To do.

  The object of the present invention includes a cylinder body having two openings and a sliding member that slides on the inner wall surface of the cylinder body, and the sliding member moves along the axis of the cylinder body. A liquid supply apparatus configured to allow liquid to flow in from one of the openings and to discharge liquid from the other of the openings, the electric actuator driving the sliding member, and the sliding by the electric actuator This is achieved by a liquid supply device including a fluid pressure cylinder that assists driving of the moving member.

  In this liquid supply apparatus, the electric actuator includes a drive rod, the fluid pressure cylinder includes a piston rod, and the drive rod and the piston rod are arranged on both sides of the sliding member on the axis of the cylinder body. It is preferable that they are arranged so as to be able to advance and retreat along each.

  Further, the apparatus further comprises a fluid pressure detecting means for detecting the pressure of the liquid discharged from the opening, and an operation control means for controlling the working fluid pressure of the fluid pressure cylinder based on the detection by the fluid pressure detecting means. Is preferred.

  The fluid pressure cylinder is preferably a double-acting air cylinder.

  The liquid supply device includes a switching valve that is connected to each of the two openings via a pipe and that can switch a liquid flow path so that liquid is supplied to one of the two openings from a liquid supply source. The liquid flow path can be switched by the switching valve in synchronism with switching of the reciprocating motion of the sliding member.

  According to the liquid supply apparatus of the present invention, the liquid can be quantitatively supplied with high accuracy regardless of the viscosity of the liquid and the load on the discharge side.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a liquid supply apparatus according to an embodiment of the present invention, and shows a main part in cross section. As shown in FIG. 1, the liquid supply apparatus includes a cylinder body 1, an electric actuator 6, and an air cylinder 7.

  The cylinder body 1 has openings 4a and 4b formed in two end plates 1a and 1b covering both ends in the axial direction, respectively, and accommodates a sliding block 2 having a circular cross section that slides along the inner wall surface. . Seal members 3 such as V-seal are provided on both sides in the axial direction of the sliding block 2, and the sealing performance when the sliding block 2 slides is maintained.

  The electric actuator 6 has a known configuration including a motor such as a pulse motor or a servo motor and a linear motion mechanism such as a ball screw. The electric actuator 6 is connected to the sliding block 2 via one end plate 1a and is connected to the cylinder body 1. The drive rod 6a which advances / retreats along the axis line is provided.

  Further, the air cylinder 7 alternately supplies compressed air through two air supply holes 7a and 7b formed at both ends of the cylinder body so that an internal piston (not shown) advances and retreats. This is a known double-acting air cylinder. The air cylinder 7 includes a piston rod 5 that is connected to the sliding block 2 via the other end plate 1 b and moves forward and backward along the axis of the cylinder body 1, and drives the sliding block 2 by the electric actuator 6. Assist.

  The air supply holes 7 a and 7 b of the air cylinder 7 are connected to a compressed air supply source 13 via a universal type three-way valve 15 and an electropneumatic converter 12. The electropneumatic converter 12 functions as an operation control means for controlling the air pressure to the air cylinder 7 based on a signal from a hydraulic pressure sensor 11 to be described later, and the configuration can be exemplified by a nozzle flapper system.

  Sliding portions of the end plates 1a and 1b of the cylinder body 1 with the drive rod 6a and the piston rod 5 are V seals, U seals, etc. made of Teflon (registered trademark), high density polyethylene, or other high performance engineering plastics. By providing the liquid-tight seal. In order to further improve the slidability and durability, it is preferable that the inner wall surface of the cylinder body 1 and the outer peripheral surfaces of the drive rod 6a and the piston rod 5 are subjected to mirror finish by applying hard chrome plating or the like.

  The cylinder diameter of the air cylinder 7 is preferably set so that necessary thrust can be obtained in consideration of the assumed pressure loss on the discharge side such as the viscosity of the liquid and the diameter and length of the discharge side piping. . Moreover, it is preferable that the stroke length of the drive rod 6a and the piston rod 5 is substantially the same from a viewpoint of making compact, specifically, 10-100 cm is preferable and 20-50 cm is more preferable.

  The diameters of the drive rod 6a and the piston rod 5 may be appropriately set in consideration of the required liquid supply flow rate, the inner diameter of the cylinder body 1, and the like, but if it is too large, the seal between the end plates 1a and 1b On the other hand, if it is too small, a problem in strength tends to occur, so the range of 5 to 20 mm is preferable, and the range of 10 to 15 mm is more preferable.

  A switching valve 10 is connected to the two openings 4a and 4b of the cylinder body 1 via distribution pipes 16a and 16b, respectively. The type of the switching valve 10 is not particularly limited, such as an air driven type or an electromagnetic type, but it is preferable to use an air driven type when used in an explosion-proof area, and an electromagnetic type is required when a faster switching response is required. It is preferable to use it. A supply pipe 16 c and a discharge pipe 16 d are connected to the switching valve 10, and the supply pipe 16 c is connected to the liquid storage tank 8 via the diaphragm pump 9. The diaphragm pump 9 supplies the liquid in the liquid storage tank 8 toward the switching valve 10 at a constant pressure.

  The switching valve 10 is configured to be able to switch the flow path so that the liquid supplied from the liquid storage tank 8 is supplied to one of the two openings 4a and 4b via the distribution pipes 16a and 16b. . When the liquid is supplied to one distribution pipe 16a, the liquid in the cylinder body 1 is discharged from the discharge pipe 16d through the other distribution pipe 16b, and when the liquid is supplied to the other distribution pipe 16b, The liquid in the cylinder body 1 is discharged from the discharge pipe 16d through one distribution pipe 16a. The discharge pipe 16d is provided with a hydraulic pressure sensor 11 that detects the pressure of the passing liquid and outputs an analog signal. The detection signal of the hydraulic pressure sensor 11 is transmitted to the electropneumatic converter 12. For example, when the liquid is a paint, the discharge pipe 16d is connected to a mixer or a paint gun. For example, when mixing a main agent and a curing agent in the case of a two-component paint or mixing a plurality of color paints in in-line toning, the mixture is supplied to the mixer before reaching the coating gun.

  The operation of the electric actuator 6, the air cylinder 7, and the diaphragm pump 9, and the switching of the flow path by the three-way valve 15 and the switching valve 10 are performed by a controller (not shown).

  Next, the operation of the liquid supply apparatus having the above configuration will be described. First, the electric actuator 6 and the diaphragm pump 9 are operated, and the sliding block 2 is moved from the one end plate 1a side to the other end plate 1b by the drive rod 6a. As a result, a liquid such as paint flows into the cylinder body 1 from the one opening 4a through the supply pipe 16c, the switching valve 10 and the distribution pipe 16a from the liquid storage tank 8, and from the other opening 4b of the cylinder body 1. The liquid in the cylinder body 1 is pushed out. The liquid discharged from the cylinder body 1 is supplied to the transport destination through the distribution pipe 16b, the switching valve 10 and the discharge pipe 16d.

  When a controller (not shown) detects that the sliding block 2 has reached a predetermined position in the vicinity of the other end plate 1b due to the amount of movement of the drive rod 6a, the controller detects that the drive rod 6a is driven by the electric actuator 6. While switching the moving direction to the reverse direction, the flow path of the switching valve 10 is switched so that the liquid is supplied to the other opening 4 b of the cylinder body 1. The sliding block 2 moves from the side of the other end plate 1b toward the one end plate 1a. The liquid flows into the cylinder body 1 from the other opening 4b and the liquid is pushed out from the one opening 4a. Then, it is supplied to the transfer destination through the distribution pipe 16a, the switching valve 10 and the discharge pipe 16d. When the sliding block 2 approaches one end plate 1a, a controller (not shown) switches the moving direction of the drive rod 6a again and switches the flow path of the switching valve 10.

  Thus, by switching the liquid flow path by the switching valve in synchronization with the switching of the reciprocating motion of the sliding block 2, the liquid passes through the discharge pipe 16d together with the reciprocating motion of the sliding block 2. The liquid paint can be continuously supplied to a mixer or a paint gun connected to the discharge pipe 16d.

The pressure of the liquid passing through the discharge pipe 16d is detected by the hydraulic pressure sensor 11, and an analog signal corresponding to the hydraulic pressure is output to the electropneumatic converter 12. Based on the input signal, the electropneumatic converter 12 controls the operating air pressure so that the pressure of the compressed air supplied to the air cylinder 7 increases as the hydraulic pressure increases. Switching of the supply flow path to the air cylinder 7 by the three-way valve 15 is controlled by a controller (not shown) so that the reciprocation of the piston rod 5 is synchronized with the reciprocation of the drive rod 6a of the electric actuator 6. That is, when the drive rod 6a moves from one end plate 1a toward the other end plate 1b, the piston rod 5 similarly moves from one end plate 1a toward the other end plate 1b , When the drive rod 6a moves from the other end plate 1b toward the one end plate 1a, the piston rod 5 similarly moves from the other end plate 1b toward the one end plate 1a . The force acting on the sliding block 2 by the air cylinder 7 varies according to the load on the discharge side detected by the hydraulic pressure sensor 11 as described above, and the propulsion of the sliding block 2 by the air cylinder 7 increases as the load increases. Power also increases. Therefore, the movement of the sliding block 2 by the electric actuator 6 can be performed in a state where the load is almost zero (that is, a state close to the case where no liquid exists in the cylinder body 1).

  In this way, even when the allowable load of the electric actuator 6 is small, the driving of the sliding block 2 by the electric actuator 6 can be assisted by the air cylinder 7, so that the liquid can be used regardless of the viscosity of the liquid or the load on the discharge side. Can be supplied at a constant flow rate with high accuracy. For example, in the case of a multi-liquid mixing device of two or more liquids, the internal pressure of the mixer varies depending on the supply state of each liquid, but according to the liquid supply device of this embodiment, the paint is always applied regardless of the internal pressure of the mixer. It can be fed at a constant flow rate and is particularly useful.

  When a pulse motor is used as a power source for the electric actuator 6, since the speed stability decreases when the speed is too low, the moving speed of the drive rod 6a is normally 0 so that the liquid supply flow rate can be controlled with high accuracy. It is preferably 1 mm / sec or more. However, by combining a pulse motor with a transmission gear or a ball screw, it is possible to obtain stable speed control even at 0.01 mm / sec, and therefore the minimum moving speed is not necessarily limited to 0.1 mm / sec.

  In actual design, the diameters of the drive rod 6a and the piston rod 5 are first determined, and the inner diameter of the cylinder body 1 (= the diameter of the sliding block 2) is determined from the set speed range of the electric actuator 6 and the set range of the required discharge amount. ) Is preferred. For example, when the minimum moving speed of the electric actuator 6 is 0.1 mm / sec, the distance that the sliding block 2 travels in one minute at this speed is 6 mm. When the required minimum discharge amount is 1 cc / min, the required cross-sectional area of the sliding block 2 is obtained, and the diameter of the sliding block 2 is calculated from this to be about 17.8 mm.

  On the other hand, the maximum moving speed of the electric actuator 6 can be set to about 200 to 1000 times the minimum moving speed. For example, when the minimum moving speed is 0.1 mm / sec, the maximum moving speed can be set to 100 mm / sec, the diameter of the drive rod 6a and the piston rod 5 is 10 mm, and the inner diameter of the cylinder body 1 is 17.8 mm. In this case, the maximum discharge amount from the cylinder body 1 is about 1000 cc / min.

  As mentioned above, although one Embodiment of this invention was explained in full detail, the specific aspect of this invention is not limited to the said embodiment. For example, the internal structure of the cylinder body 1 is not necessarily limited to that of the present embodiment as long as the liquid inside the cylinder body 1 is pressed by the movement of the sliding block 2 and supplied to the outside. By arranging 6 and the air cylinder 7 as appropriate, the same effects as in the present embodiment can be obtained.

  Further, instead of the air cylinder 7, other fluid pressure cylinders such as a double-acting hydraulic cylinder can be used.

[Example]
An embodiment of the liquid supply apparatus having the configuration shown in FIG. 1 will be described. The cylinder body 1 is made of stainless sanitary piping having an inner diameter of 72.3 mmφ, and has a total length of 500 mm and welded flanges for connection at both ends. The electric actuator 6 uses a ball screw unit (KR45) made by THK and a 5-phase pulse motor (PK543AW) made by Oriental Motor as a drive source, and the minimum control speed of the drive rod 6a is 0.1 mm / sec. As the air cylinder 7, an air cylinder (DDA100) manufactured by Koganei and having a cylinder diameter of 100 mmφ was used. As the hydraulic pressure sensor 11, a hydraulic pressure sensor (AP-52A) manufactured by Keyence Corporation was used, and as the electropneumatic converter 12, an electropneumatic converter (EVS 500) manufactured by CKD Corporation was used. The diameters of the drive rod 6a and the piston rod 5 were 10 mm.

  When a highly viscous coating material is supplied using the liquid supply apparatus configured as described above, the operating air pressure of the air cylinder 7 is set to 0.5 MPa, and the driving assistance by the air cylinder 7 enables high precision by the electric actuator 6. A fixed amount could be supplied.

  Since the cylinder diameter of the air cylinder 7 is 100 mm, the inner diameter of the cylinder body 1 is 72.3 mm, so the area ratio between them is about 2: 1. Therefore, when the operating air pressure of the air cylinder 7 is 0.5 MPa, a pressure of 1 MPa acts on the liquid in the cylinder body 1. This is approximately 4000 N when converted to the thrust of the electric actuator 6. When the sliding block 2 is driven only by the electric actuator 6 without driving assistance by the air cylinder 7 in a state where a large load acts on the discharge side in this way, the allowable thrust (about several hundred newtons) of the pulse motor is exceeded. As a result, the pulse motor stopped due to an overload condition.

It is a schematic block diagram of the liquid supply apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder main body 2 Sliding block 4a, 4b Opening 5 Piston rod 6 Electric actuator 6a Drive rod 7 Air cylinder 10 Switching valve 11 Hydraulic pressure sensor 12 Electropneumatic converter (operation control means)

Claims (4)

A cylinder body having two openings;
And a sliding member that slides an inner wall surface of said cylinder body,
A liquid supply apparatus configured to allow liquid to flow from one of the openings and to discharge liquid from the other of the openings by moving the sliding member along the axis of the cylinder body,
An electric actuator for driving the sliding member;
And a fluid pressure cylinder for assisting the driving of the sliding member by the electric actuator,
The electric actuator has a drive rod;
The fluid pressure cylinder has a piston rod;
The liquid supply device , wherein the drive rod and the piston rod are respectively disposed on both sides of the sliding member so as to be able to advance and retract along the axis of the cylinder body . Fluid pressure detecting means for detecting the pressure of the liquid discharged from the opening;
An operation control means for controlling the working fluid pressure of the fluid pressure cylinder based on the detection of the hydraulic pressure detection means ;
The liquid supply measure according to claim 1, further comprising: The fluid pressure cylinder, the liquid supply apparatus according to claim 1 or 2 which is double-acting air cylinder. A switching valve connected to each of the two openings via a pipe and capable of switching a liquid flow path so that liquid is supplied to one of the two openings from a liquid supply source;
Switching of the liquid flow path by the switching valve, the liquid supply apparatus according to claim 1 or 2 carried out in synchronization with the switching of the reciprocating motion of the sliding member.

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