JP2008088827A - Rotary displacement pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary displacement pump capable of providing stable displacement without being influenced by accuracy of components and assembly, and capable of materializing high reproducibility of flow rate irrespective of drive types such as short period drive and continuous drive. <P>SOLUTION: A drive control part 2 controls rotation quantity of a stepping motor M by pulse drive. Drive of the stepping motor M is controlled to set minimum delivery quantity of fluid to unit delivery quantity during one rotation of a drive gear 7 or a driven gear 8, or integral multiple thereof. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotary positive displacement pump that delivers a constant flow rate fluid such as a dispenser, an analyzer, a fuel cell, and an ink jet printer.

  There are various types of pumps that quantitatively deliver fluid, such as rotary displacement pumps such as gear pumps and roots pumps, and direct-acting pumps that reciprocally move pistons and plungers. Since the direct acting pump is not suitable for the continuous feeding operation of the fluid, the application is limited. On the other hand, the rotary displacement pump can adjust the flow rate by changing the number of revolutions by realizing the constant flow rate by controlling the number of revolutions of the driving side rotating body provided in the pump chamber. Versatile is expected.

For example, there has been proposed a technique for controlling the operation of a gear pump drive motor by flowing a control current substantially proportional to a set flow rate, and realizing a constant flow rate by correcting so that a constant control current flows (patent) Reference 1).
In addition, a technique has been proposed in which the correlation between the rotational speed of the drive-side rotator and the flow rate is stored in advance, and the drive signal is corrected by the detection signal of the rotational speed sensor to achieve a quantitative feed (see Patent Document 2). .
Japanese Utility Model Publication No. 07-21159 JP-A-9-155252

However, when the flow rate of the rotary positive displacement pump is measured when it is continuously driven at a high pressure and when it is driven for a short time, the variation in the flow rate is large, and the constant flow rate is lowered.
For example, in the gear pump of FIG. 3, the drive side gear 51 and the driven side gear 52 are accommodated in the pump chamber 54 of the pump body 53.
Variations in the volume of the space portion 56 surrounded by the drive side gear 51 or the driven side gear 52 and the inner wall surface 55 of the pump chamber 54 due to the component accuracy of the drive side gear 51 and the driven side gear 52 or the pump body 53. As a result, the fluid feed amount varies.
Further, the fluid feed amount varies due to the variation in the clearance P between the tooth tips of the driving gear 51 and the driven gear 52 and the inner wall surface 55 of the pump chamber 54.
Further, an assembly error between the pump body 53 in which the pump chamber 54 in which the drive side gear 51 and the driven side gear 52 are accommodated (for example, the rotation center of the drive side gear 51 and the driven side gear 52 and the pump body 53 The fluid feed amount varies due to the displacement Q of the assembly position.
These occur even if the drive side gear 51 and the driven side gear 52 are gears of the same diameter, so that the assembly errors are easily accumulated between the gears of different diameters, and the variation in the flow rate also increases.
In addition, in combination with component accuracy and assembly accuracy, variations in flow rate also occur due to variations in rotation stop position due to short-time driving or continuous driving.

  The present invention has been made to solve these problems, and the object of the present invention is to obtain a stable discharge amount without being affected by component accuracy and assembly accuracy, and drive such as short time drive and continuous drive. An object of the present invention is to provide a rotary positive displacement pump capable of realizing high flow reproducibility regardless of the method.

In order to achieve the above object, the present invention comprises the following arrangement.
A pump body formed to temporarily store fluid in a pump body in which a fluid flow path is formed, and a driving side rotating body and a driven side rotating body are engaged with each other and accommodated in the pump chamber. A rotor that discharges the fluid sucked into the chamber at a fixed amount from the discharge port, and a drive control unit that includes a stepping motor that rotationally drives the drive side rotating body. The drive control unit rotates the stepping motor by pulse driving. And the stepping motor drive is controlled so that the minimum discharge amount of the fluid becomes a unit discharge amount or an integral multiple thereof during one rotation of the driving side rotating body and the driven side rotating body.
Further, the rotor may be either a gear pump or a roots pump that pushes fluid from the pump chamber by meshing the drive side gear and the driven side gear.
In addition, the driving side rotating body and the driven side rotating body are rotated by meshing gears of the same or different diameter, and the rotation is obtained by dividing the least common multiple of the number of driving side gear teeth and the number of driven side gear teeth by the number of driving side gear teeth. The flow rate corresponding to the number is set as the minimum discharge amount.

If the rotary positive displacement pump described above is used, the drive control unit controls the rotation amount of the stepping motor by pulse driving, and the minimum discharge amount is a unit discharge amount during one rotation of the driving side rotating body and the driven side rotating body or The driving of the stepping motor is controlled so as to be an integral multiple thereof.
As a result, the drive control is performed so that the minimum flow rate of the pump is an integral multiple of both the driving side rotating body and the driven side rotating body, so that the rotation start and stop positions are constant, without being affected by the component accuracy and assembly accuracy. A stable discharge amount can be obtained, and high flow reproducibility can be realized regardless of the driving state such as short time driving or continuous driving.

  Hereinafter, the best embodiment of the rotary positive displacement pump according to the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, a gear pump will be described as an example of a rotary positive displacement pump.

First, a schematic configuration of the stepping motor M used as a drive source will be described.
A rotor core having rotor teeth formed on a rotor (not shown) is disposed, and rotates integrally with a rotating shaft made of a nonmagnetic material. The stator is provided such that the rotor is surrounded by a stator core. The stator core is provided with a pole having stator small teeth opposed to the rotor small teeth provided on the rotor core, and a magnet wire is wound around the pole via an insulator. By switching the excitation phase to the magnet wire wound around the poles of the stator core and energizing, the rotor small teeth of the rotor core rotate to a position that is magnetically stable with the stator small teeth facing it. It is like that. The stepping motor M is open-loop controlled by the drive circuit 1 by pulse driving by the PWM driving method. The stepping motor M and the drive circuit 1 constitute a pump drive control unit 2.

Next, the configuration of the gear pump will be described with reference to FIG.
A pump chamber 3 is provided in the pump body 9. The pump chamber 3 is provided in a part of the flow path of the fluid (gas, liquid, semi-fluid, etc.) F and temporarily stores the fluid F. A rotor 6 is rotatably accommodated in the pump chamber 3. As the rotor 6 rotates, the fluid F sucked into the pump chamber 3 from the suction port 4 is discharged from the discharge port 5 in a fixed amount. The rotor 6 is provided with a driving side rotating body (driving gear) 7 and a driven side rotating body (driven gear) 8 meshing with each other. The drive gear 7 of the rotor 6 is rotationally driven by the stepping motor M. In the embodiment of FIG. 1, the drive gear 7 and the driven gear 8 are gears having the same diameter and are engaged with each other to rotate.

  The drive control unit 2 controls the rotation amount of the stepping motor M by pulse driving, and the stepping motor M so that the minimum discharge amount becomes a unit discharge amount during one rotation of the drive gear 7 and the driven gear 8 or an integral multiple thereof. Control the drive. In this embodiment, since the gears having the same diameter are used on the drive side and the driven side, the drive gear 7 and the driven gear 8 rotate regardless of whether the minimum discharge amount is set for every rotation or an integral multiple of the rotation. The stop position and the rotation start position are constant.

As a result, the drive is controlled so that the minimum flow rate of the pump is an integral multiple of the drive gear 7 and the driven gear, so the rotation start and stop positions are always constant and stable without being affected by the component accuracy and assembly accuracy. Thus, a high flow rate reproducibility can be realized regardless of the driving state such as short-time driving or continuous driving.
Therefore, it can be expected to be applied to a wide range of applications such as a device for quantitatively feeding a fluid, such as a dispenser, an analyzer, a fuel cell, and an ink jet printer.

Next, another example of the gear pump will be described with reference to FIG. The present embodiment has the same schematic configuration as that of FIG. 1, except that the drive gear 7 and the driven gear 8 constituting the rotor 6 are rotated by meshing gears of different diameters. .
In this case, since there is a difference in the number of teeth, the amount of rotation differs between the drive gear 7 and the driven gear 8. Therefore, the flow rate corresponding to the rotational speed obtained by dividing the least common multiple of the number of teeth of the drive gear 7 and the number of teeth of the driven gear 8 by the number of teeth of the drive gear 7 is defined as the minimum discharge amount. And the drive control part 2 drive-controls the stepping motor M so that it may become the integral multiple rotation amount. As a result, the rotation start and stop positions of the gear pump are always constant, and a stable discharge amount can be obtained without being affected by the component accuracy and assembly accuracy, and a high flow rate can be reproduced regardless of the driving state such as short-time driving or continuous driving. Can be realized.

  In the embodiment described above, the gear pump is exemplified as the rotary positive displacement pump. However, the present invention is not limited to this, and a roots pump or the like may be used. The roots type pump is one in which, for example, vertical rotors mesh with each other in the pump chamber to push out the fluid from the pump chamber, and for the rotation amount of the rotor, high flow reproducibility can be realized by using the same drive control as in this embodiment. .

It is explanatory drawing of a gear pump. It is explanatory drawing of the gear pump which concerns on another example. It is explanatory drawing which shows the subject of a gear pump.

Explanation of symbols

M Stepping motor F Fluid 1 Drive circuit 2 Drive controller 3 Pump chamber 4 Suction port 5 Discharge port 6 Rotor 7 Drive gear 8 Driven gear 9 Pump body

Claims (3)

A pump chamber formed to temporarily store fluid in a pump body in which a fluid flow path is formed;
A rotor for driving and rotating the driven side rotor and the driven side rotor in the pump chamber, and discharging the fluid sucked from the suction port into the pump chamber in a fixed amount from the discharge port;
A drive control unit including a stepping motor that rotationally drives the drive side rotating body;
The drive control unit controls the rotation amount of the stepping motor by pulse driving, and the stepping motor is configured so that the minimum discharge amount is a unit discharge amount or an integral multiple thereof during one rotation of the driving side rotating body and the driven side rotating body. A rotary positive displacement pump that controls the drive of the motor.   2. The rotary positive displacement pump according to claim 1, wherein the rotor is a gear pump or a roots pump that engages the driving side gear and the driven side gear to push the fluid from the pump chamber.   The drive-side rotator and the driven-side rotator are rotated by meshing the same or different diameter gears, and the number of rotations is obtained by dividing the least common multiple of the number of drive-side gear teeth and the number of driven-side gear teeth by the number of drive-side gear teeth. The rotary positive displacement pump according to claim 1, wherein a corresponding flow rate is a minimum discharge amount.

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