JPS6140045B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes one detected value generating element for detecting a physical quantity that changes within a detection range between a predetermined first state and a second state. The present invention relates to a physical quantity detecting device configured to eliminate the influence of variations in characteristics of detected value generating elements.

Conventionally, in a physical quantity detection device, for example, a position detection device that includes a magnetically sensitive element for sensing the magnetism of a permanent magnet attached to a detected object, manufacturing variations in the magnetically sensitive element affect the detected position of the detected object. This directly appears as a variation in the detected value generated from the magnetically sensitive element in response to the change in position, so when manufacturing a position detection device, it is necessary to select magnetically sensitive elements with similar relationships (detection characteristics) between the detected value and the detected position. Furthermore, in order to eliminate as much as possible the influence on detection accuracy due to slight variations in the characteristics of the selected magnetically sensitive element, the installation position of the magnetically sensitive element may be adjusted or a permanent magnet for bias may be used. The detected value from the magnetically sensitive element is corrected by applying a magnetic field to the magnetically sensitive element in advance. However, the work of adjusting the installation position of the magnetically sensitive element or the work of installing the bias permanent magnet is troublesome for the operator, and the work of selecting the magnetically sensitive element requires considerable time and effort. This has caused a decrease in the manufacturing efficiency of the position detection device.

Therefore, the present invention has been made in view of the above-mentioned matters, and uses a detected value generated from a detected value generating element such as a magnetically sensitive element in response to an actual physical quantity such as a position based on a predetermined standard. By correcting the value to a value corresponding to the actual physical quantity on a straight line representing a linear function, it is possible to accurately and easily detect the physical quantity without being affected by variations in the characteristics of the detected value generating element, that is, differences in the characteristics. The object of the present invention is to provide a physical quantity detection device configured to.

The present invention will be described below by embodying it in a cloth thickness detecting device for a sewing machine.

FIG. 1 shows the head of a sewing machine, in which a sewing needle 2 is attached to a needle bar 1 which is capable of vertically reciprocating movement, and a presser bar 3 is disposed adjacent to the needle bar 1. A presser foot 4 is attached to the lower end of the presser bar 3, a presser bar holder 5 is fixed to the middle part of the presser bar 3, and a presser lever 6 is formed at the base end of the presser lever 6 to move the presser bar 3 up and down. The cam surface is in contact with the lower part of the presser bar holder 5. The spring 7 is fitted into the presser bar 3 and its lower end is locked to the presser bar holder 5. The connecting rod 8 is fitted into the presser rod 3 and is locked to the upper end of the spring 7, and its tip end key-shaped portion 8a engages with a rotating arm 10 rotatably supported by a frame 9 of the sewing machine head. are doing. A cam sliding surface is formed on the right side of the upper surface of the rotating arm 10, and the cam surface of the cam body 11 engages with the cam sliding surface 10a to rotate the rotating arm 10. The pressing pressure of the work cloth 13 held between the upper surface of the bed 12 and the upper surface of the bed 12 can be adjusted and set according to the rotational position of the cam body 11.

An automatic thread tension device 20 is provided to supply the needle thread 15 from the needle thread supply source toward the thread take-up lever 14 and the sewing needle 2. The pressure roller 22 is urged by a spring force so as to come into contact with the roller. The upper thread 15 is caught between both rollers 21 and 22, and the step motor performs a stepwise motion in synchronization with the vertical reciprocating movement of the sewing needle 2, thereby increasing the upper thread necessary to form one stitch. The yarn 15 is supplied. The supply amount of the upper thread 15, ie, the number of steps of the step motor, is calculated based on the stitch pitch and the thickness of the work cloth 13. The thickness of the work cloth 13 is detected by a cloth thickness detector 30, and a permanent magnet 32 is attached to the presser bar 3 with a screw 31 so that its position can be adjusted, and a screw 33 is attached to the frame 9 of the sewing machine head. The cloth thickness detector 30 is constituted by a Hall IC 34 whose position is adjustable. The position of the permanent magnet 32 when the push-up lever 6 is lowered and the presser foot 4 is located on the top surface of the bed 12 is defined as the first position P1, and the push-up lever 6 is raised and the presser foot 4 is placed in the uppermost position. The position of the permanent magnet 32 at a certain time is defined as a second position P2. The position of the permanent magnet 32, that is, the position of the presser foot 4 is detected in the detection range between the two positions P1 and P2, and a voltage having a value related to the position is output from the Hall IC 34.

Within the detection range, the permanent magnet 32 or the Hall IC 34 can be used so that the part of characteristic A (shown in FIG. 3) in which the voltage value is approximately proportional to the position of the Hall IC 34 can be used.
Adjust the position appropriately. This adjustment work may be roughly performed so that a portion having a substantially proportional relationship with the characteristic A can be used since the characteristic difference of the Hall IC 34 is almost eliminated by the detection value correction operation described later.

FIG. 2 is a block diagram showing the electrical configuration of this embodiment, and the voltage of the value corresponding to the thickness of the workpiece cloth 13 from the cloth thickness detector 30 is converted into digital detection information by the A/D converter 41. Cloth feed information that controls the amount of feed of the work cloth 13 and amplitude information that controls the horizontal swing amplitude of the sewing needle 2 are generated from the stitch information generator 43 and supplied to the central processing unit 42. It is supplied to the processing device 42. The central processing unit 42 receives the digital detection information from the A/D converter 41 and the stitch information generator every time it receives a timing pulse generated from the timing pulse generator 44 in synchronization with the up and down reciprocating movement of the sewing needle 2. Read the cloth feed information and amplitude information from 43,
The digital detection information is corrected, and an arithmetic operation is performed to determine the needle thread supply amount based on the fabric feed information, amplitude information, and the corrected information (information representing fabric thickness). The needle thread supply amount determined as described above is supplied to the needle thread supply drive device 45 as drive information for instructing the number of steps of the step motor connected to the drive roller 21.
The input operation unit 46 is placed at an appropriate position on the sewing machine, and in response to the input operation unit 46, digital detection information from the A/D converter 41 is read into the central processing unit 42 and stored in a random access memory (hereinafter referred to as
(abbreviated as RAM) 47.
A read-only memory (hereinafter abbreviated as ROM) 48 fixedly stores the control program for the central processing unit 42, and also stores the control program for the central processing unit 42, which is determined according to the characteristic B having a standard linear function relationship shown in FIG. Reference information representing first and second reference values b2 and b2 corresponding to the first and second positions P1 and P2 is also fixedly stored. The central processing unit is integrated as a microprocessor, and the central processing unit is integrated as a microprocessor.
Together with ROM 48 and RAM 47, it constitutes a microcomputer.

The operation of this embodiment configured above will be explained.

Hall IC 3 used in cloth thickness detector 30
4 is the first and second position P of the permanent magnet 32
Since it is necessary to find the voltage value to be output in relation to P1 and P2, the permanent magnet 32 is moved to the first position P1.
After positioning, the input operation unit 46 is operated to convert the detected voltage value a1 corresponding to the first position P1 into digital information and stored in the RAM 47, and then the permanent magnet 32 is positioned at the second position P2. After that, the user operates the input operation section 46 to convert the detected voltage value a2 corresponding to the second position P2 into digital information and stores it in the RAM 47. Therefore, the detected voltage values a1 and a2 according to the characteristic A of the Hall IC 34
Detection information representing the is temporarily stored in the RAM 47,
Based on the stored information, the permanent magnet 32 in the detection range between the first and second positions P1 and P2 is
It is possible to know the proportional relationship between the position of and the voltage value of the Hall IC 34.

Next, in order to start sewing work, when the work cloth 13 is clamped between the presser foot 4 and the top surface of the bed 12 and the sewing machine motor is started, a timing pulse is generated from the timing pulse generator 44 and the central processing The device 42 reads digital information from the A/D converter 41 and cloth feed amount information and amplitude information from the stitch information generating device 43. The digital information is transmitted to the Hall IC 34 according to the thickness of the processed cloth 13.
represents the voltage value a output from. hole
Permanent magnet 3 when IC34 outputs voltage of value a
If the actual position of 2 is P, then the value b corresponding to the actual position P on the straight line representing the standard linear function (characteristic B) can be determined according to the following arithmetic expression.

b=b2+(b1-b2)・(a-a2)/(a1-a2) The central processing unit 42 calculates the actual position according to the linear function of the reference before performing the calculation for determining the upper thread supply amount. A value b corresponding to P is calculated. That is, reference information in the ROM 48 representing the first and second reference values b1 and b2, and RAM 47 representing the first and second detected voltage values a1 and a2.
The central processing unit 42 determines the position P corresponding to the actual position P based on the detection information within and the digital information representing the voltage value a read in response to the generation of the timing pulse and according to the arithmetic expression. Calculate the value b. Therefore, the detected voltage value according to the characteristic A of the Hall IC 34 is a standard linear function (characteristic B).
The influence of the difference in characteristic A is removed, and all values representing the position of the permanent magnet 32 are determined according to characteristic B.

After the above correction calculation operation is completed, a calculation operation for determining the upper thread supply amount is performed. That is, the central processing unit 42 calculates the stitch pitch based on the cloth feed amount information and amplitude information read in response to the generation of the timing pulse, and further calculates the stitch pitch based on the value b determined by the above-mentioned correction calculation operation. The needle thread supply amount necessary for forming one stitch is calculated based on the information representing the thickness of the work cloth 13 (meaning the thickness of the work cloth 13) and the information representing the calculated stitch pitch. Central processing unit 4
2 repeats the above-mentioned correction calculation operation and needle thread supply amount calculation operation every time the timing pulse occurs;
The calculated needle thread supply amount is supplied to the needle thread supply drive device 45 as drive information for the step motor, and thereby the drive roller 21 and the pressure roller 22 are rotated to transfer the needle thread 15 to the thread take-up lever 14 and the sewing needle 2.
Stitches are formed on the work cloth 13 with the optimum thread tension.

Regardless of whether the Hall IC in this embodiment has the characteristic A or the characteristic C shown in FIG. Therefore, the generated voltage values a and c are standardized and corrected to the value b according to the standard linear function (characteristic B), and the influence on detection accuracy due to the difference in characteristics of the Hall IC is removed. In addition, the characteristics of the Hall IC are as follows:
It is ideal to have an accurate proportional relationship in the detection range between 1 and P2, but the maximum error of the Hall IC characteristic A with respect to the ideal proportional relationship (straight line D shown in Figure 3) is the maximum error of the Hall IC. If it is negligible compared to the voltage value output from the Hall
The influence of differences in IC characteristics can be almost eliminated by the above-mentioned corrective calculation operation.

In the embodiments described above, the present invention is embodied as a cloth thickness detection device, but it goes without saying that various modifications can be made to any device that detects physical quantities, such as a temperature detection device or a pressure detection device. It is about.

As is clear from the above description, the present invention is capable of converting a detected value generated from a detected value generating element for detecting an actual physical quantity that changes within a predetermined detection range into a linear function of a predetermined standard. By correcting the value to a value corresponding to the actual physical quantity on the straight line representing the value, it is possible to eliminate the influence on the detection accuracy due to the characteristic characteristic difference of the detected value generating element, and to detect the physical quantity accurately and easily. Since the detection value correction operation is performed by a microcomputer, the detection device as a whole can be miniaturized.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the head of a sewing machine in which the cloth thickness detecting device of this embodiment is incorporated, FIG. 2 is a block diagram of a control section that controls the operation of the cloth thickness detecting device, and FIG.
The figure is an explanatory diagram for explaining the correction calculation operation in the cloth thickness detection device. In the figure, 30 is a cloth thickness detector, 32 is a permanent magnet, and 34
is a Hall IC, 42 is a central processing unit, and 47 is a
RAM, 48 is ROM, P1, P2 are first and second
, P is the actual position, a1 and a2 are the first and second detected voltage values, and b1 and b2 are the first and second reference values.

Claims (1)

[Claims] 1. In order to detect a physical quantity that changes within a detection range between a predetermined first state and a second state, detection that changes approximately proportionally in relation to the physical quantity. One detected value generating element that generates a value, and first and second reference values corresponding to the first and second states determined according to the relationship of a linear function of a predetermined reference are stored. a reference value storage means; a first value generated from the detected value generating element when the physical quantity is in a first state and a second state, respectively;
and a detection value storage means for storing a second detection value; and a detection value storage means for storing a detection value generated from the detection value generating element corresponding to an actual physical quantity within the detection range in the reference value storage means. a calculation means for performing calculations based on both the reference value and the detected value stored in the detected value storage means to correct the value to a value corresponding to the actual physical quantity on the straight line representing the linear function of the reference; A physical quantity detection device characterized in that an influence due to a difference in characteristics of the detected value generating elements is removed. 2. The reference value storage means is comprised of a nonvolatile memory that permanently stores the first and second reference values, and the detected value storage means is comprised of a volatile memory that temporarily stores the first and second detected values. The first
2. The physical quantity detecting device according to claim 1, wherein the second detected value is stored in its volatile memory. 3. The physical quantity detection device according to claim 1, wherein the calculation means is comprised of a microcomputer.