JP2004308690A - Linear motion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow an operating element 3 to be pushed and pulled independent of a guide tolerance on the side of the operating element 3, solve the nonconformity of a side load being applied on a screw shaft 401 and a rotary nut due to a pushing and pulling load, and solve the problem of drop of thrust due to tight screw engagement and malfunction when driving the operating element 3 back and forth with the screw shaft 401 of a linear motor 4. <P>SOLUTION: A fitting tolerance of a guide 203 vertically guiding the operating element 3 is set to be higher than a shaft center assembling tolerance of the screw shaft 401 of the linear motor 4. A tip part of the screw shaft 401 is connected to the operating element 3 with a loosely fixing means 5 absorbing the center deviation or rotational run-out of the screw shaft due to the shaft center assembling tolerance of the linear motor 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motion device that pushes and pulls an operating body that is highly accurately positioned and guided using a linear motion motor.
[0002]
[Prior art]
Usually, in a sample analysis process, etc., it is necessary to perform highly accurate positioning when dispensing a reagent, moving a container, reacting a sample in a container, stirring, and the like.For example, a liquid such as a reagent is transferred to a plurality of containers. There are known a dispensing machine for dispensing in a dispensing manner, a stirrer for stirring a sample in a test tube by inserting a stirring rod, an analyzer for analyzing a sample in a container by stopping various sensors close to each other, and promoting a reaction. In general, the linearly moving (advancing / retracting) operation used in these methods is such that an operating body to be positioned is guided by a pair of guide shafts to a ball guide with a fitting tolerance of (1 to 5) / 100 mm. A structure that allows the robot to move forward and backward is employed. In some cases, positioning accuracy is required in the moving process in addition to stopping the robot in proximity to the object.
[0003]
However, these positioning drive mechanisms use a rotary motor whose output shaft rotates as a drive source, connect one end of the feed screw to the motor shaft via a coupling, and connect the middle to the operating body via a connection nut member. Since it has a structure in which it is screwed and the other end is rotatably supported on the base, the number of components and the structure of the drive mechanism are complicated, and there is an inconvenience that causes a cost increase.
[0004]
By the way, in order to make such a complicated mechanism unnecessary and to make it inexpensive, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-39639, a mold clamping device of a molding device using a linear motor as a power source has been proposed. Some have tried to adopt a known one.
The linear motion motor uses a screw shaft as an output shaft, and the screw shaft is screwed into a rotating nut (rotor) to convert the motion into a non-rotating linear motion. Due to the above problems etc., there is a limit to the assembly accuracy such as the shaft axis of the screw shaft being misaligned and tilting during assembly, and the screw shaft and nut are screwed together taking into account the thermal expansion during driving (Tooth) It is assembled with tolerance, especially when resin is used for the nut, since the expansion coefficient with the screw shaft is different, it is necessary to take into account such tolerance. There was a structural problem with respect to the shaft core assembly tolerance, and its use range was limited.
[0005]
Therefore, as in the mold clamping device, the operating body (movable plate) is guided along the four guide shafts, and is finally pressed against the base (fixed plate) to be pushed and pulled so as to stop feeding and stopping. Since it is not necessary to guide the operating body with a high-accuracy fitting tolerance exceeding the shaft assembly tolerance of the linear motion motor, including its moving process, the screw shaft of the motor is set at the center position between the guide shafts. If the tolerances on the motor side and the guide tolerances on the operating body side are set to be approximately equal and substantially no load, and if the motor rotation nuts meet predetermined requirements such as adopting an expensive ball screw structure, push-pull Although it is possible to drive, there is a problem that the side load is applied between the screw shaft and the nut due to the problems such as the axial misalignment and the screwing deviation, and the durability is impaired. Use type motor It was also added factors that costly than the drive mechanism, not intended to be substantially employed.
Further, in the above-described device requiring high-precision movement and positioning, since the operating body is guided with a tolerance setting exceeding the assembly tolerance of the linear motor, a screw shaft is connected to the operating body (or the base). In the case of pushing and pulling, the side load is applied between the screw shaft and the nut due to the problem of the shaft center misalignment and the screwing deviation, the screwing is tight, the thrust is reduced, and the operation is defective. And it was difficult to use it substantially.
[0006]
[Patent Document 1]
JP-A-8-39639
[Problems to be solved by the invention]
The present invention has been conceived in order to eliminate the above-described problems, and in which an operating body is driven forward and backward by a screw shaft of a linear motion motor, while the linear motion motor has a misalignment or a screw. Even if there is a problem in the manufacturing such as joint blur, the operating body can be pushed and pulled without depending on the guide tolerance of the operating body side, and the screw shaft and the rotating nut are The problem that side load is applied to the motor is eliminated, the screwing is not tight, the thrust is not reduced, and the malfunction does not occur, and the durability of the linear motor can be improved. In addition to stopping, it requires positioning accuracy in its moving process, and can be used as a linear motion device such as a dispenser or analyzer that requires the use of a rotary motor, expanding its use range. This And to provide a linear motion device capable.
[0008]
[Means for Solving the Problems]
The technical means adopted by the present invention to solve the above-mentioned problem is that an operating body is slidably fitted to a guide provided on a base with a predetermined fitting tolerance so as to be movable forward and backward, and the operating body is configured to be movable. Is driven by a linear motor, the fitting tolerance with the guide is configured with an accuracy that exceeds the shaft core assembly tolerance of the screw shaft of the linear motor, while the linear motor is mounted on the base or the operating body. One of the screw shafts, and the other end of the screw shaft, with respect to the base or the operating body different from the side on which the linear motor is provided, the screw shaft by the shaft core assembly tolerance of the linear motor. The moving body is connected by a play means for absorbing a center deviation or a rotational shake of the moving body, and the operating body is configured to perform a straight running operation.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a linear motion device illustrating an embodiment of the present invention as a preferred embodiment will be described in detail with reference to the drawings. FIG. 1 is a front view of a main part of a linear motion device, FIG. 2 is a side view of a main part, FIG. 3 is a detailed view of a connection part of a motor screw shaft, and FIG. As shown in FIG. 1, the linear motion device 1 includes a base 2 having an upper base 201 and a lower base 202 and formed in a substantially U-shape in a side view, and a predetermined interval on the left and right sides of the base 2. Axial guides 203, 203 erected (standing) on the upper base 201 and the lower base 202, respectively, and the operating body 3 slidably (elevated) with a predetermined fitting tolerance on the guide 203. It is configured to be movable forward and backward (elevation), and the tip of a screw shaft 401 of a linear stepping motor 4 (hereinafter simply referred to as a linear motor) disposed on the upper base 201 is attached to the operating body 3 by play means 5. Are connected so that they can be driven up and down (forward and backward).
[0010]
The insertion structure of the operating body 3 with the guide 203 is approximately 2 / a due to a so-called ball guide structure in which a ball guide 302 is provided in guide holes 301 formed in the operating body 3 and inserted into the guide 203. The ascending and descending guide is designed to be highly accurate with a fitting tolerance of 100 mm.
Note that the configuration of the base 2 and the operating body 3 and the arrangement of the linear motor 4 are not limited thereto. For example, the concave base 2 is a convex base when viewed from the side, The guide 203 is slidably fitted and protruded from both sides of the base, and an operating body is provided as a set on both left and right ends of the guide 203, a linear motion motor is mounted on one operating body side, and the other operating body is mounted. It may be configured to perform a predetermined work operation such as positioning. In this case, the other working body is provided with various sensors in the working body, for example, to allow a sample in a container such as a test tube to react magnetically or to measure the transmittance. It is used for work of a straight-ahead (advance / retreat) operation such as positioning in close proximity or pushing and moving a test tube rack to a predetermined position to carry and position. In FIG. 1, the linear motor 4 may be provided on the operating body 3 side, and the tip of the screw shaft 401 may be connected to either the upper base 201 or the lower base 202.
[0011]
FIGS. 3 and 4 show a connection structure of the tip end of the screw shaft 401 and the operating body 3 by the play means 5.
The loosening means 5 is provided with a pair of concave and convex relations including a receiving portion 51 provided on the operating body 3 and a joint portion 52 formed at the tip of the screw shaft to be loosely fitted to the receiving portion 51. Stop is configured. That is, the receiving portion 51 includes the concave groove 511 formed in the operating body 3, the plate member 512 bent and formed in a substantially L-shape, and the U-shaped engagement formed by notching the plate member 512. The coupling portion 52 is formed around the axis of the screw shaft 401 (around the circumference) so as to form a locking projection 521 around the tip of the screw shaft 401. A concave joint groove 522 to be engaged with (engaged with) is formed. In this case, since the screw shaft 401 is not restricted from rotating on the side of the linear motor 4, the engagement concave portion 513 is formed in the joint groove 522. The rotation-stop restricting portion 523 that comes into contact with is formed integrally.
Thus, the receiving portion 51 and the joint portion 52 allow the engaging convex portion 521 to be inserted into the concave groove 511 in a state where the joint groove 522 is engaged with the engaging concave portion 513, and the plate member 512 is actuated. 3, the tip of the screw shaft 401 (locking projection 521) is prevented from coming off by the locking recess 513, and is loosely attached to swing in the vertical, left, right, front and rear (XYZ axis) directions. , A so-called universal joint mechanism.
[0012]
FIG. 5 shows another embodiment of the locking projection formed at the tip of the screw shaft 401. The locking projection 521 is not formed integrally with the screw shaft 401, but is formed as a locking projection. A washer member is used as 521a, and a detent member 523a that contacts the joint groove 522a and the locking concave portion 513 is formed of a rectangular tubular member. Is formed by screwing into a female screw portion 402 formed in the hole.
[0013]
FIG. 6 shows another embodiment of the locking projection in the case where the screw shaft 401 is regulated by the rotation preventing regulating portion 403 on the side of the linear motion motor 4. A bearing 521c having a bearing ball mounted between a pair of opposed inner and outer rings at a predetermined interval is screwed into a female screw portion 402 formed in a screw shaft 401 by an attachment bolt 521b and mounted. . The bearing ball is loosely fitted in the curved joint groove 521d provided in the inner and outer rings, and the outer ring is fitted in the surface area facing the concave groove 511a formed in the operating body 3, and is prevented from falling off by the donut-shaped mounting plate 512a. By fixing, the tip of the screw shaft 401 is configured to be able to swing (mainly from the curved joint groove 521d to the attachment bolt 521b) and swing back and forth.
[0014]
Next, a configuration in a case where the linear motion device 1 is applied to a dispenser will be described. In constituting the cylinder unit 6, a cylinder block 61 having a plurality of cylinders 611, 611 is provided on the lower base 202, and a plurality of plungers 621, 621 which are fitted and sealed in the cylinders 611 and operate as pistons. A plunger block 62 having the following structure is provided on the operating body 3.
The cylinder 611 is provided with an injection needle 612 at the tip. The cylinder 611 is provided on a front surface of the lower base 202 in a cylinder holder 71 having an openable and closable holding lid 711 individually attached thereto. It is detachably attached to it.
Each plunger 621 is fitted with a U-shaped plunger mounting groove 721 formed in the operating body 3 so that the T-shaped head is placed and inserted from the near side, and the head is fitted. It is detachably attached to a plunger holder 72 having a cover 722 fixed to the operating body 3 with screws.
As a result, the operating body 3 functioning as the plunger block 62 is integrally moved up and down by forward and reverse driving of the linear motor 4, and each plunger 621 transfers an arbitrary reagent (sample) in the container 8 to the cylinder 611. A fixed amount is sucked into the inside, and the fixed amount is discharged. The cylinder 611 and the plunger 621 are replaced with cylinders and plungers of a commercially available syringe or syringe.
[0015]
The linear motion device 1 is also applied to the dispensing table T provided on the work stage (base). In this case, the dispensing table T as the operating body 3 is provided on the base. The screw shaft 401 of the linear motion motor 4 (not shown) is connected by the same play means 5 as described above, and is configured to be able to move forward and backward. In addition, the dispensing table T has a lower surface area formed by a guide structure as disclosed in Japanese Patent Application Laid-Open No. 2001-82469, which is formed in place of the fitting structure of the guide 203 and the guide hole 301. The convex rail and the concave guide groove are configured to be slidable with good fitting tolerance by means of concave and convex fitting (not shown). The convex rail and the concave guide groove may be formed to have a wide width, and the side walls of both may be substituted for the pair of guides 203 and the guide holes 301.
As described above, the dispensing machine to which the linear motion device 1 is applied includes an operating mechanism 9 (inside omitted) provided on the back side and other components, along with arbitrary components in the front-rear, left-right, up-down (XYZ axis) directions. The dispensing table T is disposed on a work stage that can be moved back and forth or swingable, and a sample solution bottle (not shown) and a dispensing table T that are disposed on the work stage. A plurality of cartridges (small containers) 8 which are set vertically and horizontally are accurately positioned with respect to the arrangement site of the cartridge containers (small containers) 8. A predetermined amount of reagent solution is simultaneously poured into the containers 8, 8. The sample solution container may be arbitrarily used separately from the one integrally formed with the cartridge container.
[0016]
In the embodiment of the present invention configured as described above, the dispenser moves on the dispensing table T, and sucks about 0.5 to 3 cc of the test solution into each cylinder 611, and dispenses the test solution into each of the child containers 8, The operation of dispensing a fixed amount (dispensing) by subdividing the droplets sequentially in the form of droplets 8 is performed. At this time, the working body 3 handles the expensive reagent solution in an amount necessary for a single suction and discharge. As described above, it is necessary to set the piston stroke amount (positioning movement amount) and the piston speed of the plunger 621 by controlling the rotation of the motor, and to mount the plunger 621 on the guide 203 so as to be slidable (elevated) so as to ascend and descend in good balance.
In the drive mechanism of the feed screw system using the conventional rotary motor, the setting tolerance of the fitting between the guide 203 and the operating body 3 depends mainly on the screwing tolerance of the fitting between the feed screw and the operating body 3 and the feed pitch. Although the accuracy is maintained, when the linear motor 4 is used, the balance of maintaining the accuracy is lost due to a problem in accuracy of the linear motor itself, such as assembly, and cannot be adopted.
However, the linear motion device 1 according to the present invention slides (moves up and down) the operating body 3 so that the fitting tolerance between the guide 203 and the guide hole 301 exceeds the assembly tolerance of the screw shaft 401 of the linear motor 4. The linear motor 4 is disposed on the base 2 and one end of the screw shaft 401 is connected to the operating body 3 by a screw according to the shaft core assembly tolerance of the linear motor 4. The shaft 401 is connected with the play means 5 for absorbing the misalignment or the rotation blur of the shaft 401, and is configured to perform the straight running operation of the operating body.
[0017]
For this reason, even though the operating body 3 is driven forward and backward by the screw shaft 401 of the linear motor 4, even if the linear motor 4 has a problem in its manufacture such as a misalignment of the shaft center or a screwing error. In addition, the operating body 3 can be pushed and pulled without depending on the guide tolerance of the operating body 3 side, and it is not only necessary to dispose the play means 5 at the center between the specially arranged guides 203, 203. This eliminates the problem that the side load is applied to the screw shaft 401 and the rotating nut due to the push / pull load accompanying the forward / reverse drive. Performance can be improved. As a result, not only is the tip of the plunger 621 approached to the bottom side of the cylinder 611 to be positioned at the suction standby position, but also is not stopped close to the target object, but is also slightly pushed and moved after the suction to distribute and discharge. It can respond to the usability that requires the positioning accuracy in, and is comparable to that of the feed screw type drive mechanism using a conventional rotary motor as a linear motion device such as a dispenser or analyzer. It can be used while maintaining its performance, and it is not necessary to use parts that constitute a drive mechanism such as a feed screw, a coupling, and a connecting nut member, and the structure is simplified, and it can be provided as an easy-to-manufacture and inexpensive product. The range can be expanded.
[0018]
The loosening means 5 has a pair of concave and convex relations including a receiving portion 51 provided on the operating body 3 and a joint portion 52 formed at the tip of the screw shaft 401 to be loosely fitted to the receiving portion 51. , It can be formed with a very simple universal joint structure.
That is, the receiving portion 51 is formed by the concave groove 511 and the locking concave portion 513, and the joint portion 52 is formed as a locking convex portion 521 at the tip of the screw shaft 401. The part 521 is inserted into the concave groove 511, and is prevented from coming off by the locking concave part 513 and loosely attached. Further, the concave groove 511 and the locking concave portion 513 may be formed by processing the operating body 3 itself. However, the concave groove 511 is formed in the operating body 3 itself, and the locking concave portion 513 is formed as a separate plate member. Since it is formed at 512, the connection between the receiving portion 51 and the joint portion 52 can be easily released by the attachment / detachment operation of the plate member 512, and the attachment / detachment of the motor can be easily carried out.
[0019]
Thus, the operation body 3 is pushed and pulled by the linear motor 4 via the play means 5. At this time, the width of the joint groove 522 (522a, 521d) is set to be wider than the plate thickness of the plate member 512 (the ball diameter of the ball bearing) so that a side load is not applied to the screw shaft 401. As shown in FIG. 1, a movement amount corresponding to a clearance obtained by subtracting the plate thickness of the plate member 512 from the width of the joint groove 522 is generated as a positioning error when the reversal is started. Motor control considering the clearance is required.
Therefore, when the operation direction is reversed, such as from pushing to pulling, the amount of clearance movement is corrected to the number of movement (rotation) pulses, the number of clearance pulses is corrected, and the control pulse to the next positioning point is adjusted. By adding the number of clearance correction pulses (movement amount error value) to the number, control for canceling the positioning error for the clearance is performed. This makes it possible to eliminate the positioning accuracy error for the clearance.
[0020]
【The invention's effect】
The operating body 3 is slidably fitted to each guide 203 provided at a predetermined interval on the base body 2 with a predetermined fitting tolerance so that the operating body 3 can be moved forward and backward, and the operating body 3 is moved by a linear motor. 4, the fitting tolerance with the guide 203 is configured with an accuracy exceeding the tolerance of assembling the axis of the screw shaft 401 of the linear motor 4, while the linear motor 4 is connected to the base 2 or The one end of the screw shaft 401 is disposed on one of the operating bodies 3 and one end of the screw shaft 401 is connected to the base 2 or the operating body 3 different from the side on which the linear motor 4 is disposed. By connecting with the play means 5 for absorbing the center deviation of the screw shaft due to the shaft core assembling tolerance or the rotational shake, the linear motion of the operating body 3 is performed.
Even though the operating body 3 is driven forward and backward by the screw shaft 401 of the linear motor 4, even if the linear motor 4 has a problem in its manufacture such as misalignment of the shaft center and unbalanced screwing, the operating body 3 The operation body 3 can be pushed and pulled without depending on the guide tolerance on the third side, and the problem that the screw shaft 401 and the rotating nut are side-loaded by the push-pull load accompanying the forward / reverse drive is eliminated, and the screw engagement is reduced. Tightening does not cause a decrease in thrust or malfunction, and the durability of the linear motor 4 can be improved. As a result, not only is it stopped close to an object, but also positioning is performed during its movement process. It can be used as a linear motion device such as a dispenser or an analyzer, which requires precision and requires the use of a rotary motor, thereby expanding its use range.
[Brief description of the drawings]
FIG. 1 is a front view of a main part of a linear motion device used as a dispensing mechanism.
FIG. 2 is a side view of a main part of FIG. 1;
FIG. 3 is a detailed view showing a joint structure of a motor screw shaft.
FIG. 4 is an explanatory view of connection of a motor screw shaft.
FIG. 5 is an exploded perspective view showing another embodiment of the locking projection formed at the tip of the screw shaft.
FIG. 6 is an essential part cross-sectional view showing another embodiment of the connection structure of the motor screw shaft.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Linear motion device 2 Substrate 201 Upper base 202 Lower base 203 Guide 3 Actuator 301 Guide hole 302 Ball guide 4 Linear motor 401 Screw shaft 402 Female screw 403 Restriction 5 Playing means 51 Reception part 511 Recessed groove 511a Recessed groove 512 Plate member 512a Mounting plate 513 Locking concave portion 52 Joint portion 521 Locking convex portion 521a Locking convex portion 521b Mounting bolt 521c Bearing 521d Curved joint groove 522 Joint groove groove 522a Joint groove groove 523 Regulator 523a Regulator 6 cylinder unit 61 Cylinder block 611 Cylinder 612 Injection needle 62 Plunger block 621 Plunger 71 Cylinder holder 711 Holding lid 72 Plunger holder 721 Plunger mounting groove 722 Cover body 8 Container 9 Operating mechanism T Dispensing table

Claims (8)

An operating body is slidably inserted into a guide provided on the base body with a predetermined fitting tolerance so as to be able to move forward and backward. While the linear motion motor is configured with an accuracy exceeding the shaft core assembly tolerance of the screw shaft, the linear motion motor is disposed on either the base or the operating body, and one end of the screw shaft is The linear motion motor is connected to a base or an operating body different from the side on which the linear motion motor is provided, by a play means for absorbing a deviation of the screw shaft or a rotational deviation due to the shaft core assembly tolerance of the linear motion motor, A linear motion device configured to perform a linear motion of the operating body. The pair of concave-convex portions according to claim 1, wherein the attaching means comprises a receiving portion provided on the base or the operating body, and a coupling portion formed at the tip of the screw shaft so as to be loosely fitted to the receiving portion. A linear motion device characterized in that the linear motion device is configured to be prevented from falling off. In Claim 2, The receiving part is formed of a concave groove and a locking concave part, a locking convex part is provided in the joint part, and the receiving part and the joint part form the locking convex part with a concave groove. A linear motion device, wherein the linear motion device is loosely inserted in the locking concave portion and loosely attached. 4. The linear motion device according to claim 3, wherein the receiving portion is formed of a plate member in which the locking recess is formed with a notch, and is detachably attached to the base or the operating body. 5. 5. The screw shaft according to claim 3, wherein the concave groove is provided on the base or the operating body, and the locking protrusion is formed integrally with the screw shaft by a concave joint groove engraved around the axis of the screw shaft. 6. A linear motion device. The linear motion device according to any one of claims 2 to 5, wherein, when the rotation of the screw shaft is not restricted on the translation motor side, the rotation of the receiving portion and the joint portion is stopped. The operating body according to any one of claims 1 to 6, wherein the operating body is disposed on both sides of the guide protruding from both sides of the base, a linear motion motor is mounted on one operating body side, and the other operating body is mounted. A linear motion device configured to perform a predetermined work operation such as positioning and the like. 8. The method according to claim 1, wherein at the time of the reversal start of the pushing and pulling of the operating body, the clearance movement amount of the screw shaft formed by the play means is converted into the number of movement pulses of the linear motor. At least, it is set as the number of error correction pulses of the clearance, and the movement amount at the time of the inversion start is configured to be positioned by motor control that adds the number of error correction pulses to the number of control pulses to an arbitrary positioning point. Linear motion device characterized by the above-mentioned.

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