JP2003057128A - Magnetostriction type load sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetostriction type load sensor that can be made small in size and light in weight and can be reduced in cost. SOLUTION: In this magnetostriction type load sensor 1 constituted by housing a coil 4 and a detection rod 2 arranged in the axial center of the coil 4 in a case 5, the case 5 is made of a sheet metal and one end of the detection rod 2 is held by the flat face of the case 5. Thus, one end face forming the flat face of the detection rod 2 requires no precise machining, and because the case 5 is made of inexpensive sheet metal, the load sensor 1 can be made compact and light in weight and the cost can be also reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive load sensor for electromagnetically detecting a load acting on a detection rod by a magnetostrictive effect.

[0002]

2. Description of the Related Art A strain gauge type load cell is known as a load sensor for detecting a load acting on an elastic body. The load cell detects a strain of an elastic body which is elastically deformed by receiving a load. The load acting on the elastic body is calculated based on the detected strain.

However, since the strain gauge type load cell is weak in strength and cannot have a wide dynamic range (range of load to be used), it has a small tolerance for a force higher than the rated load, and a large rated load cell can detect a small load. There is a problem that the accuracy cannot be secured and the output signal is weak, so that the signal processing circuit becomes complicated and the cost increases.

Therefore, the present applicant has previously proposed a load detection sensor for electromagnetically detecting a load by utilizing the magnetostrictive effect (see Japanese Patent Laid-Open No. 11-241955). This magnetostrictive load sensor applies a current to a coil to magnetize a detection rod, applies a load to the detection rod to change its magnetic characteristic, and converts the change in the magnetic characteristic into a voltage change and outputs the voltage change. The load is detected.

[0005]

However, in the conventional magnetostrictive load sensor, since the detection rod directly receives the load, the end surface of the detection rod on the side received by the case needs to be processed with high precision, and Since the case that receives the load from the detection rod was made of die-cast,
There is a problem that the sensor becomes large in size, heavy in weight, and high in cost.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetostrictive load sensor which can be reduced in size, weight and cost.

[0007]

In order to achieve the above object, the invention according to claim 1 is a magnetostrictive load constructed by housing a coil and a detection rod arranged at the axial center of the coil in a case. In the sensor, the case is made of a metal plate, and one end of the detection rod is received by a plane portion of the case.

A second aspect of the present invention is the magnetostrictive load sensor according to the first aspect, wherein one end of the detection rod that abuts the case is a flange shape.

According to a third aspect of the present invention, in the first or second aspect of the invention, the case has an upper and lower half-split structure.
It is characterized in that the detection rod is sandwiched and fixed by two upper and lower cases.

A fourth aspect of the present invention is characterized in that, in the first, second or third aspect of the invention, a lead wire from the coil is taken out from the case in a lateral direction.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, a cover for forming a magnetic shield is provided at the lead-out portion of the lead wire.

According to a sixth aspect of the present invention, in the first aspect of the present invention, a sensor unit including the coil, the detection rod, and the case is slidably provided in a holder, and the sensor unit is unidirectionally formed by a spring member. Characterized by having been urged.

According to a seventh aspect of the present invention, in the sixth aspect, the two sensor units having the same structure are electrically differentially connected.

Therefore, according to the present invention, since the case is made of sheet metal and one end of the detection rod is received by the flat surface portion of the case, it is not necessary to process the one end surface of the detection rod with high precision. In addition, since the case is made of inexpensive metal plate, it is possible to reduce the size and weight of the magnetostrictive load sensor and reduce the cost.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a side sectional view of a magnetostrictive load sensor according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is an arrow of FIG. FIG. 4 is a view in the B direction, and FIG. 4 is a view showing various forms of the flange shape of the detection rod of the magnetostrictive load sensor.

In the magnetostrictive load sensor 1 shown in FIG.
Reference numeral 2 denotes a detection rod made of a magnetic material, around which a coil 4 housed in a bobbin 3 is arranged. These detection rod 2, bobbin 3 and coil 4 are housed in a case 5 made of sheet metal. Has been done.

Here, the case 5 has an upper and lower two-part structure composed of an upper case 5A and a receiving case 5B, and a flange portion 2a is formed at the lower end of the detection rod 2. A recess 3a (see FIG. 1) for accommodating the flange 2a of the detection rod 2 is formed at the center of the lower end surface of the bobbin 3.
The lower end flange portion 2a is vertically supported as shown by being sandwiched between the bobbin 3 and the receiving case 5B, and the upper end portion thereof projects upward from the upper case 5A.

Here, the case 5 is assembled by bending and crimping the cut-and-raised parts 5a formed at four locations on the outer periphery of the receiving case 5B to the peripheral edge of the lower end of the upper case 5A. The lead wire 6 extending from the coil 4 is laterally taken out from the notch formed in the case 5, and the take-out portion of the lead wire 6 is fitted into the case 5 in order to reduce magnetic resistance and prevent disturbance. It is shielded by the cover 7.

In the magnetostrictive load sensor 1 having the above structure, the detection rod 2 is magnetized by the current flowing through the coil 4, and when an external load is applied to the upper end of the magnetized detection rod 2, the detection rod 2 is detected. A compressive force acts on the magnetic flux 2 to reduce the magnetic permeability of the detection rod 2 due to the magnetostrictive effect, which causes an inductance change, which changes the voltage across the coil 4. Therefore, the external load can be detected electromagnetically by detecting the change in the voltage.

In the above, since the case 5 is made of sheet metal and one end of the detection rod 2 is received by the flat surface portion of the receiving side case 5B of the case 5 in the present embodiment, the flat surface of the detection rod 2 is formed. It is not necessary to perform high-precision machining on one end face, and since the case 5 is made of inexpensive sheet metal, the magnetostrictive load sensor 1 can be made smaller and lighter and the cost can be reduced. In this case, since the flange portion 2a is formed at the lower end portion of the detection rod 2, the adhesion of the lower end portion of the detection rod 2 to the case 5 is enhanced, and the detection rod 2
A high degree of verticality can be secured.

Further, since the lead wire 6 is taken out from the case 5 in the lateral direction, no external load acts on the lead wire 6, and breakage or damage of the lead wire 6 is prevented.

In the present embodiment, the shape of the flange portion 2a of the detection rod 2 is stepped as shown in FIG. 4 (a), but it is tapered as shown in FIG. 4 (b), (c), (d). Alternatively, the R shape may be formed as shown in FIG. 2B, or the flange 2a may be formed as a separate body as shown in FIGS.

Further, as shown in FIG. 5, the magnetostrictive load sensor 1 is independently installed on a flat base 8, and an output signal from the sensor 1 is amplified by an amplifier 9 and sent to a controller 10. The actuator 10 can be drive-controlled by the controller 10.

Further, as shown in FIG. 6, two magnetostrictive load sensors 1 and 1 ′ are installed on a flat base 8 and output signals from both sensors 1 and 1 ′ are differentiated by an amplifier 8. The actuator 11 can be amplified and sent to the controller 10 to drive and control the actuator 11. At this time, when the loads 1 and 2 act simultaneously, both loads 1 and 2
Of the load 1 or 2 can be detected, and the action direction and magnitude of the load 1 or 2 can be detected.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. 7 is a side sectional view of the magnetostrictive load sensor according to the present embodiment, and FIG. 8 is a view in the direction of arrow C in FIG. 7, in which the same elements as those shown in FIGS. Are denoted by the same reference numerals, and description thereof will be omitted below.

In the magnetostrictive overload sensor 1 according to the present embodiment, the detection rod 2 has a straight shape, and the recess 5b is formed in the receiving side case 5B of the case 5 made of sheet metal. The detection rod 2 is vertically supported by fitting and holding the lower end.

Further, the lead wire 6 extending from the coil 4 is laterally taken out from the lead-out hole 5e formed by the convex portions 5c and 5d formed on the upper case 5A of the case 5 and the receiving side case 5b, and the magnetic resistance. In order to reduce the noise and prevent disturbance, the lead-out portion of the lead wire is shielded by the convex portions 5c and 5d of the case 5 forming the cover portion.

In this embodiment as well, since the case 5 is made of sheet metal and one end of the detection rod 2 is received by the flat surface portion of the receiving side case 5B of the case 5, the first embodiment described above is adopted. The same effect as can be obtained.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIGS. 9 and 10. Incidentally, FIG.
(A)-(c) is sectional drawing which shows the basic composition and operation of the magnetostrictive load sensor which concerns on this Embodiment, FIG.10 (a) shows the load which acts on the detection rod of the same magnetostrictive load sensor, and an external load. And FIG. 6B is a diagram showing the relationship between the protrusion amount of the detection rod and the external load.

Magnetostrictive load sensor 1 according to the present embodiment
Includes a sensor unit SU including a coil, a detection rod 2 and a case 5 (not shown) slidably in the holder 12, and the sensor unit SU is biased upward by a spring 13 to push the sensor unit SU. While the external load acting on the detection rod 2 from the plate 14 is less than the initial set load F ₀ of the spring 13, the sensor unit SU is at the upper end position in the holder 12 as shown in FIG. The detection rod 2 protruding upward from the upper surface of the holder 12 protrudes upward from the upper surface of the holder 12 by a ₀ . Although not shown, in the magnetostrictive load sensor 1 according to the present embodiment as well, a flange portion is formed at the lower end portion of the detection rod 2, and the lead wire 6 from the sensor unit SU is taken out in the lateral direction. ing.

In the magnetostrictive load sensor 1 having the above construction, the holder 12, which also functions as a stopper, the spring 13, and the detection rod 2 constitute an overload preventing mechanism, and the load (compressive force) acting on the detection rod 2 is compressed. ) Is a constant value F
It can be kept below. The holder 12 that functions as a stopper is made of a material having a higher strength than the detection rod 2.

Next, the operation of the magnetostrictive load sensor 1 having the above overload preventing mechanism will be described.

The detection rod 2 is magnetized by passing a current through a coil (not shown) of the sensor unit SU,
When an external load acts on the detection rod 2 of the sensor unit SU from the push plate 14, a compressive force acts on the detection rod 2 in the axial direction. When the compressive force acts on the detection rod 2 in this way, the magnetic permeability of the detection rod 2 decreases due to the magnetostrictive effect and the magnetic characteristic changes. Therefore, the change in the magnetic characteristic is converted into a voltage change and output to detect the change. The external load acting on the rod 2 is detected.

By the way, when the external load is less than the initial set load F ₀ of the spring 13, the spring 13 does not deform, and as shown in FIGS. 9 (a) and 10 (b), the detection rod 2
The protrusion amount a of is kept at the initial value a ₀ , and the load (compressive force) acting on the detection rod 2 linearly changes with an increase or decrease of the external load as shown in FIG.

When the external load increases above the initial set load F ₀ of the spring 13, the spring begins to be deformed by compression as shown in FIG. 9B, and the load acting on the detection rod 2 is as shown in FIG.
As shown in FIG. 0 (b), the amount of protrusion a of the detection rod 2 is shown in FIG.
As shown in 0 (b), it decreases linearly in inverse proportion to the increase of the external load.

When the external load increases above a certain value F, the detection rod 2 is completely buried in the holder 12 as shown in FIG. 9 (c), and the protrusion amount a is shown in FIG. 9 (c). Also, as shown in FIG. 10B, the detection rod 2 becomes zero (a = 0), and part of the external load is received by the holder 12 that functions as a stopper.
As shown in (a), a constant load F acts, and the load greater than the maximum load does not act on the detection rod 2.

Therefore, in the magnetostrictive load sensor 1 according to the present embodiment, the load acting on the detection rod 2 can be suppressed to the fixed value F or less smaller than the allowable load of the detection rod 2 by the overload prevention mechanism. Since the detection rod 2 is not plastically deformed and its magnetic characteristics do not change, an external load less than the constant value F can always be detected accurately, and the reliability and durability of the magnetostrictive load sensor 1 are improved. To be
When the magnetostrictive load sensor 1 is used with zero displacement, its usage area (range of external load to be detected) is shown in FIG.
As shown in (b), the area is equal to or less than the initial set load F ₀ of the spring 13.

Further, the magnetostrictive load sensor 1 according to the present embodiment can be displaced by the spring 13 when an external load larger than the initial load F ₀ of the spring 13 acts, so that the installation management thereof is easy. Turn into.

Further, since the magnetostrictive load sensor 1 according to the present embodiment is constructed without largely changing its structure, the cost can be reduced, and the action of overload due to vibration or shock can be prevented. It is also suitable for mounting on a moving body such as a vehicle.

As shown in FIG. 11, the pressing member 14
A cap 15 may be interposed between the sensor 15 and the detection rod 2 of the sensor unit SU, and an initial value a ₀ of the protrusion amount a of the cap 15 from the holder 12 may be set.
Also, as shown in FIG. 12, two sensor units SU
It is also possible to adopt a configuration in which the sensor units SU1 and SU2 are biased upward by a spring 13 so that the sensor units SU1 and SU2 are provided so as to be vertically slidable in the holder 12 by electrically differentially connecting them.

<Fourth Embodiment> A fourth embodiment of the present invention will be described below with reference to FIGS. 13 and 14. Incidentally, FIG.
3 is a side view of the electric cart, and FIG. 14 is an enlarged detailed view of a portion D of FIG.

This embodiment shows an application example of the magnetostrictive load sensor 1 according to the third embodiment, and FIG.
In the electric trolley 20 shown in FIG. 1, the main body 21 is movably supported by a pair of left and right front wheels 22 and rear wheels 23, and an electric motor 24 is installed between the front wheels 22 and the rear wheels 23 of the main body 21. A battery 25 and a control box 26 are arranged above it. In the control box 26, a detection circuit and a drive circuit (not shown) are incorporated.

The rotation of the electric motor 24 is decelerated by a speed reducer (not shown) and transmitted to the rear wheel 23, and the rear wheel 23 is rotationally driven to drive the electric carriage 20.

A handle stay 27 is erected obliquely upward and rearward from the rear portion of the main body 21, and a handle 28 extending horizontally in the horizontal direction is provided above the handle stay 27 with respect to the handle stay 27. The handle stay 27 and the handle 2 are provided so as to be movable back and forth.
The magnetostrictive load sensor 1 (see FIG. 9) according to the third embodiment is interposed between the first and second sensors. 14, the same elements as those shown in FIG. 9 are designated by the same reference numerals.

In the electric carriage 20 having the above structure, when the operator holds the handle 28 by hand and pushes it forward, the force applied to the handle 28 by the operator is electromagnetically applied by the magnetostrictive load sensor 1. The detected sensor output signal is output as a control signal by a detection circuit (not shown) incorporated in the control box 26. The electric motor 2 is driven by a control signal output from a drive circuit that operates based on this control signal.
4 is driven, the rotation of the electric motor 24 is transmitted to the rear wheels 23, and the electric carriage 20 travels by human power and assist force by the electric motor 24. In the present embodiment, the electric motor 24 provides an assist force having a magnitude proportional to the force applied to the handle 28 by the operator,
This reduces the physical burden on the operator.

Thus, also in this embodiment, the magnetostrictive load sensor 1 having the overload preventing mechanism is not overloaded, so that the magnetostrictive load sensor 1 is effectively protected.

[0048]

As is apparent from the above description, according to the present invention, in the magnetostrictive load sensor constructed by housing the coil and the detection rod arranged at the axial center of the coil in the case, Since the case is made of sheet metal and one end of the detection rod is received by the plane portion of the case, the magnetostrictive load sensor can be reduced in size, weight, and cost.

[Brief description of drawings]

FIG. 1 is a side sectional view of a magnetostrictive load sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

3 is a view in the direction of arrow B in FIG.

FIG. 4 is a view showing various forms of the flange shape of the detection rod of the magnetostrictive load sensor according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram showing a modified example of the magnetostrictive load sensor according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram showing a modified example of the magnetostrictive load sensor according to the first embodiment of the present invention.

FIG. 7 is a side sectional view of a magnetostrictive load sensor according to a second embodiment of the present invention.

8 is a view in the direction of arrow C in FIG.

9A to 9C are cross-sectional views showing the basic configuration and operation of a magnetostrictive load sensor according to a third embodiment of the present invention.

10A is a diagram showing a relationship between a load acting on a detection rod of the magnetostrictive load sensor and an external load, and FIG. 10B is a diagram showing a relationship between a protrusion amount of the detection rod and an external load. .

FIG. 11 is a sectional view showing a modified example of the magnetostrictive load sensor according to the third embodiment of the present invention.

FIG. 12 is a sectional view showing a modified example of the magnetostrictive load sensor according to the third embodiment of the present invention.

FIG. 13 is a side view of an electric carriage including a magnetostrictive load sensor according to a fourth embodiment of the present invention.

FIG. 14 is an enlarged detailed view of a portion D in FIG.

[Explanation of symbols]

1 Magnetostrictive load sensor 2 Detection rod 2a Flange at the bottom of the detection rod 3 bobbins 4 coils 5 cases 5A upper case 5B Receiving case 6 lead wire 7 cover 12,12 'holder 13 Spring (bar member) 15 Spacer

Claims (7)

[Claims] 1. A magnetostrictive load sensor configured to house a coil and a detection rod arranged at the axis of the coil in a case, wherein the case is made of sheet metal, and one end of the detection rod is a case. A magnetostrictive load sensor characterized by being configured to be received by a flat portion of the. 2. The magnetostrictive load sensor according to claim 1, wherein one end of the detection rod that comes into contact with the case has a flange shape. 3. The magnetostrictive load sensor according to claim 1, wherein the case has a vertically divided structure, and the detection rod is sandwiched and fixed by the vertically divided two cases. 4. The magnetostrictive load sensor according to claim 1, wherein the lead wire from the coil is taken out from the case in a lateral direction. 5. The cover for forming a magnetic shield is provided at the lead-out portion of the lead wire.
The magnetostrictive load sensor described. 6. The magnetostriction according to claim 1, wherein a sensor unit including the coil, the detection rod, and the case is slidably provided in a holder, and the sensor unit is biased in one direction by a spring member. Load sensor. 7. The magnetostrictive load sensor according to claim 6, wherein the two sensor units having the same structure are electrically differentially connected.