A high-precision, high-life composite contact linear displacement sensor

Abstract

The present invention discloses a high-precision, high-life composite contact linear displacement sensor, in which a movable shaft is installed in a housing and one end thereof passes through the housing, a brush is installed on the movable shaft and can contact and slide on a resistor, and the resistor and the brush are both located in the housing; in the resistor, an insulating layer is provided on the outer peripheral surface of a conductive skeleton, the conductive skeleton is installed on an insulating base, a precision resistance wire is wound on the insulating layer on the outer peripheral surface of the conductive skeleton, and the outer surface of the conductive skeleton and the precision resistance wire is covered with a conductive plastic resistance film layer in the area that needs to contact with the brush when in use. The resistor of the linear displacement sensor of the present invention integrates the advantages of traditional precision wire-wound resistors and precision conductive plastic resistors, while also overcoming their respective shortcomings, forming a high-precision, high-life composite contact linear displacement sensor, whose resistance temperature coefficient can reach 78ppm / ℃, and whose service life can reach 1 million weeks.

Description

Technical Field

[0001] The invention relates to a contact type linear displacement sensor, in particular to a high-precision, long-life composite contact type linear displacement sensor. Background Art

[0002] The function of the contact linear displacement sensor is to convert the linear mechanical displacement into an electrical signal. In order to achieve this effect, the resistor (i.e. the variable resistor slide) is usually fixed in a fixed position inside the sensor, and the brush (i.e. the slider) is moved on the resistor to measure different resistance values. The two power supply end leads of the resistor are respectively connected to the two output ends of the steady-state DC power supply, allowing a small current to flow. The voltage between the brush and the starting end is proportional to the length of the brush movement.

[0003] The working principle of the traditional contact linear displacement sensor is the working principle of the sliding rheostat. The contact resistors used as sensors mainly include precision wire-wound resistors and precision conductive plastic resistors. The advantages of precision wire-wound resistors are small resistance temperature coefficient (≤100ppm / ℃) and high linear accuracy, but the disadvantages are low life (taking the electrical stroke of 20mm as an example: ≥50,000 cycles) and large resolution (0.1%); the advantages of precision conductive plastic resistors are long life (taking the electrical stroke of 20mm as an example: ≥1 million cycles), small resolution (infinitely small), and high linear accuracy, but the disadvantage is large resistance temperature coefficient (≤500ppm / ℃). No matter which type of resistor the user uses, they are always restricted by their respective shortcomings, which is extremely inconvenient to use. In addition, the reed bracket of the traditional contact linear displacement sensor is fixedly connected to the moving shaft. After the two are connected, the moving shaft can only move linearly and cannot rotate, which is not conducive to the assembly and adjustment of the sensor. Summary of the invention

[0004] The object of the present invention is to provide a high-precision, long-life composite contact type linear displacement sensor in order to solve the above-mentioned problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A high-precision, high-life composite contact linear displacement sensor comprises a housing, a movable shaft, a brush and a resistor, wherein the movable shaft is installed in the housing and one end of the movable shaft passes through the housing, the brush is installed on the movable shaft, the resistor and the brush are both located in the housing, the brush can contact and slide on the resistor, the resistor comprises an insulating base, a conductive skeleton, a precision resistance wire and a conductive plastic resistance film layer, the outer peripheral surface of the conductive skeleton is provided with an insulating layer, the conductive skeleton is installed on the insulating base, the precision resistance wire is wound on the outer peripheral surface insulating layer of the conductive skeleton, and the outer side surfaces of the conductive skeleton and the precision resistance wire, the areas that need to contact with the brush when in use are covered with the conductive plastic resistance film layer.

[0007] In the above structure, the resistor body is not a conventional resistor, but a variable resistor slide rail formed by a precision resistor wire and a conductive plastic resistor film layer composited on a conductive frame; the insulating base is used as the installation base of the entire resistor body; the conductive frame is used to wind the precision resistor wire and lay the conductive plastic resistor film layer; the precision resistor wire is a precision conductor with a large electrical conductivity and a small diameter; the conductive plastic resistor film layer has a relatively small electrical conductivity, but it is also a conductor; the area on the outer surface of the conductive frame and the precision resistor wire that needs to contact the brush when in use is generally defined as the working surface. This setting can not only meet the use requirements, but also save raw material costs as much as possible.

[0008] Preferably, in order to improve the service life of the displacement sensor and achieve good contact between the conductive plastic resistor film layer and the brush, the conductive skeleton is a copper core enameled wire and its radial cross-section is square, and the conductive plastic resistor film layer is arranged on the working surface of the conductive skeleton, where the working surface is the outer surface of the area that needs to contact the brush during use, and the insulating base is a plastic base.

[0009] Preferably, in order to utilize the conductive skeleton as the transmission medium of the power supply end so as to remove the independent transmission wire and be able to lead out two power supply end leads from one end so as to achieve the purpose of reducing the volume and saving space, the precision resistance wire is wound on the conductive skeleton in a single layer, the first end of the precision resistance wire is connected to the first power supply end lead, the second end of the precision resistance wire is connected to the conductive end face of the corresponding end of the conductive skeleton, and the conductive end face of the other end of the conductive skeleton is connected to the second power supply end lead.

[0010] Preferably, in order to minimize the resistance temperature coefficient of the displacement sensor and to ensure that the conductive plastic resistor film layer has sufficient wear resistance while meeting the conductive property requirements, the precision resistance wire is a nickel, chromium, iron, or aluminum alloy wire with a resistance temperature coefficient ≤100ppm / °C; the conductive plastic resistor film layer is a resistor film layer formed by spraying conductive plastic resistor slurry on the working surfaces of the conductive skeleton and the precision resistor wire and curing the conductive plastic resistor slurry, wherein the working surface is the outer surface of the area that needs to contact the brush during use.

[0011] Preferably, in order to make the conductive plastic resistor film layer have sufficient wear resistance while meeting the conductive property requirements, the conductive plastic resistor paste includes graphite, carbon black and DPO resin. The DPO resin is dioctyl phthalate.

[0012] Furthermore, in order to more significantly improve the linear accuracy of the linear displacement sensor, the precision resistance wire is intermittently wound on the conductive frame, and the position between two adjacent turns of the precision resistance wire in the conductive plastic resistance film layer is trimmed by a linear trimming machine to form a trimming groove.

[0013] Furthermore, in order to more significantly improve the linear accuracy of the linear displacement sensor, the resistance values ​​of all corresponding parts of the conductive plastic resistance film layer located between two adjacent trimming grooves are the same.

[0014] Furthermore, in order to enable the moving shaft to rotate after semi-assembly to facilitate continued assembly and adjustment, the composite contact linear displacement sensor also includes a reed bracket, the moving shaft is composed of a large diameter section and a small diameter section connected to each other, the reed bracket is sleeved on the small diameter section of the moving shaft, the brush is installed on the reed bracket, an "O"-shaped washer sleeved on the small diameter section of the moving shaft is provided between one end of the reed bracket and the large diameter section of the moving shaft, and an elastic clamping ring sleeved on the small diameter section of the moving shaft is provided between the other end of the reed bracket and the nut sleeved on the small diameter section of the moving shaft.

[0015] Specifically, the elastic clamping ring includes an elastic washer and two fixed washers arranged on both sides of the elastic washer.

[0016] The beneficial effects of the present invention are:

[0017] The resistor of the linear displacement sensor of the present invention integrates the advantages of traditional precision wire-wound resistors and precision conductive plastic resistors, while overcoming their respective disadvantages, forming a high-precision, long-life composite contact linear displacement sensor, whose resistance temperature coefficient can reach 78ppm / ℃, and life can reach 1 million cycles, and the comprehensive performance is much higher than that of traditional linear displacement sensors; the specific advantages are as follows:

[0018] 1. By designing a composite structure of precision resistance wire + conductive plastic resistance film layer, after applying voltage to the resistor, the electrons migrate under the action of the electric field. This migration path of electrons is often the path with the least impedance. The impedance of the precision resistance wire is small, while the conductive items of the conductive plastic resistance film layer are graphite and carbon black, which have a large impedance. Therefore, the electrons migrate only through the precision resistance wire. After the composite, the resistance temperature coefficient of the sensor is actually the resistance temperature coefficient of the precision resistance wire, so the resistance temperature coefficient of the sensor is small;

[0019] 2. The conductive properties of the conductive skeleton are utilized to directly connect one end of the precision resistance wire to the conductive end surface of the conductive skeleton, so that both power supply leads are led out from one end of the resistor body without adding independent transmission wires. This can significantly reduce the volume of the product (up to one third of the volume) and save space;

[0020] 3. Cover the precision resistance wire with a conductive plastic resistance film layer, so that the brush contacts the conductive plastic resistance film layer when moving, which significantly improves the sensor life and can reach 1 million cycles;

[0021] 4. By linearly trimming the position between two adjacent turns of precision resistance wire in the conductive plastic resistor film layer, the linear accuracy of the sensor is significantly improved to 0.3%;

[0022] 5. By installing an elastic collar at one end of the reed bracket and positioning it with a nut, the moving shaft can still rotate after being connected to the reed bracket, i.e., semi-assembled, thereby facilitating the continued assembly and adjustment of the sensor and making installation easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a partial cross-sectional front view structural schematic diagram of the high-precision, long-life composite contact type linear displacement sensor of the present invention;

[0024] Figure 2 The main view of the resistor body of the high-precision, high-life composite contact linear displacement sensor of the present invention is shown in the figure. Figure 1 ;

[0025] Figure 3 1 is a top view of the resistor body of the high-precision, high-life composite contact linear displacement sensor of the present invention, and the ratio in the figure is greater than Figure 1 ;

[0026] Figure 4 The schematic diagram of the main structure of the high-precision, high-life composite contact linear displacement sensor of the present invention is a schematic diagram of the connection between the spring bracket and the moving shaft, and the scale of the figure is larger than Figure 1 . DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings:

[0028] like Figure 1-Figure 3 As shown, the high-precision, high-life composite contact linear displacement sensor of the present invention includes a housing 3, a moving shaft 10, a brush 7 (two multi-finger brushes in the figure) and a resistor 6 (two in the figure), the moving shaft 10 is installed in the housing 3 and one end thereof passes through the housing 3, the brush 7 is installed on the moving shaft 10, the resistor 6 and the brush 7 are both located in the housing 3, the brush 7 can contact and slide on the resistor 6, the resistor 6 includes an insulating base 63, a conductive skeleton 64, a precision resistance wire 65 and a conductive plastic resistance film layer 66, the outer peripheral surface of the conductive skeleton 64 is provided with an insulating layer, the conductive skeleton 64 is installed on the insulating base 63, the precision resistance wire 65 is wound on the outer peripheral surface insulating layer of the conductive skeleton 64, and the outer surface of the conductive skeleton 64 and the precision resistance wire 65 The area that needs to contact with the brush 7 when in use is covered with a conductive plastic resistance film layer 66.

[0029] Figure 1 Also shown are the first end cap 1 and the second end cap 11 respectively installed at both ends of the housing 3, the mounting support 2 installed in the housing 3, and the resistor 6 installed in the housing 3 through the mounting support 2 and the second end cap 11. These structures are conventional structures.

[0030] like Figure 1-Figure 3 As shown, when in use, the two ends of the precision resistance wire 65 are connected to an external power source; the outer end of the movable shaft 10 is connected to the component that needs to detect linear displacement. When the component moves, the movable shaft 10 is driven to move, thereby driving the brush 7 to move on the conductive plastic resistance film layer 66 on the resistor body 6, thereby changing the electrical signal output by the resistor body 6. The electrical signal is output to an external central processing unit. After the central processing unit processes and calculates the signal, the linear movement distance of the movable shaft 10 and the corresponding external component is obtained, thereby achieving the purpose of linear displacement detection.

[0031] like Figure 1-Figure 4 As shown, a variety of optimized structures are also disclosed below. According to actual needs, the above structure can be superimposed and combined with one or more of the following structures to form a more optimized technical solution.

[0032] In order to improve the service life of the displacement sensor and ensure good contact between the conductive plastic resistor film layer 66 and the brush 3, the conductive skeleton 64 is a copper core enameled wire with a square radial cross section. The conductive plastic resistor film layer 66 is arranged on the working surface of the conductive skeleton 64, and the insulating base 63 is a plastic base.

[0033] In order to utilize the conductive skeleton 64 as the transmission medium of the power end to remove the independent transmission wire and be able to lead out two power end leads from one end to achieve the purpose of reducing the volume and saving space, the precision resistance wire 65 is wound on the conductive skeleton 64 in a single layer, the first end of the precision resistance wire 65 is connected to the first power end lead 61, the second end 67 of the precision resistance wire 65 is connected to the conductive end face of the corresponding end of the conductive skeleton 64, and the conductive end face of the other end of the conductive skeleton 64 is connected to the second power end lead 62. When in use, the first power end lead 61 and the second power end lead 62 are externally connected to a weak power source, and the current passes through the first power end lead 61, the precision resistance wire 65, the conductive skeleton 64, and the second power end lead 62 in sequence (the current can also pass through the above loop in the reverse direction).

[0034] In order to minimize the resistance temperature coefficient of the displacement sensor and make the conductive plastic resistor film layer 66 have sufficient wear resistance under the premise of meeting the requirements of the conductive characteristics, the precision resistor wire 65 is a nickel, chromium, iron, aluminum alloy wire with a resistance temperature coefficient of ≤100ppm / ℃; the conductive plastic resistor film layer 66 is a resistor film layer formed by printing the conductive plastic resistor slurry on the working surface of the conductive skeleton 64 and the precision resistor wire 65 and curing, and more preferably, the processing method of printing-precuring-secondary molding-curing. Further, in order to make the conductive plastic resistor film layer 66 have sufficient wear resistance under the premise of meeting the requirements of the conductive characteristics, the conductive plastic resistor slurry includes graphite, carbon black and DPO resin.

[0035] In order to more significantly improve the linear accuracy of the linear displacement sensor, the precision resistance wire 65 is intermittently wound on the conductive frame 64, and the position between two adjacent turns of the precision resistance wire 65 in the conductive plastic resistance film layer 66 is trimmed by a linear trimming machine to form a trimming groove 68. Further, in order to more significantly improve the linear accuracy of the linear displacement sensor, the resistance values ​​of all corresponding parts between two adjacent trimming grooves 68 in the conductive plastic resistance film layer 66 are the same.

[0036] In order to enable the moving shaft 10 to rotate after semi-assembly so as to facilitate further assembly and adjustment, the composite contact type linear displacement sensor further includes a reed bracket 8, the moving shaft 10 is composed of a large diameter section and a small diameter section connected to each other, the reed bracket 8 is sleeved on the small diameter section of the moving shaft 10, the brush 3 is mounted on the reed bracket 8, an "O"-shaped washer 9 sleeved on the small diameter section of the moving shaft 10 is provided between one end of the reed bracket 8 and the large diameter section of the moving shaft 10, and an elastic clamp 5 sleeved on the small diameter section of the moving shaft 10 is provided between the other end of the reed bracket 8 and the nut 4 sleeved on the small diameter section of the moving shaft 10. Specifically, the elastic clamp 5 includes an elastic washer (not marked in the figure) and two fixed washers (not marked in the figure) provided on both sides of the elastic washer.

[0037] The above embodiments are only preferred embodiments of the present invention and are not limitations of the technical solutions of the present invention. Any technical solution that can be implemented on the basis of the above embodiments without creative work should be deemed to fall within the scope of protection of the patent of the present invention.

Claims

1. A high-precision, high-life composite contact linear displacement sensor, comprising a housing, a moving shaft, a brush and a resistor, wherein the moving shaft is installed in the housing and one end thereof passes through the housing, the brush is installed on the moving shaft, the resistor and the brush are both located in the housing, and the brush can contact and slide on the resistor, characterized in that: The resistor body includes an insulating base, a conductive frame, a precision resistance wire and a conductive plastic resistance film layer. The outer peripheral surface of the conductive frame is provided with an insulating layer, the conductive frame is installed on the insulating base, the precision resistance wire is wound on the outer peripheral surface insulating layer of the conductive frame, and the outer side surfaces of the conductive frame and the precision resistance wire are covered with the conductive plastic resistance film layer in areas that need to contact the brush when in use; the conductive frame is a copper core enameled wire and its radial cross-section is square, the conductive plastic resistance film layer is arranged on the working surface of the conductive frame, and the insulating base is a plastic base; the precision resistance wire is wound on the conductive frame in a single layer, the first end of the precision resistance wire is connected to the first power supply end lead, and the second end of the precision resistance wire is connected to the conductive wire at the corresponding end of the conductive frame. The conductive end face of the conductive skeleton is connected, and the conductive end face of the other end of the conductive skeleton is connected to the second power supply end lead; the precision resistance wire is intermittently wound on the conductive skeleton, and the position between two adjacent turns of the precision resistance wire in the conductive plastic resistance film layer is trimmed by a linear trimmer to form a trimming groove; the composite contact linear displacement sensor also includes a reed bracket, the movable shaft is composed of a large diameter section and a small diameter section connected to each other, the reed bracket is sleeved on the small diameter section of the movable shaft, the brush is installed on the reed bracket, an "O"-shaped washer sleeved on the small diameter section of the movable shaft is provided between one end of the reed bracket and the large diameter section of the movable shaft, and an elastic clamping ring sleeved on the small diameter section of the movable shaft is provided between the other end of the reed bracket and the nut sleeved on the small diameter section of the movable shaft.

2. The high-precision, long-life composite contact linear displacement sensor according to claim 1, characterized in that: The precision resistance wire is a nickel, chromium, iron or aluminum alloy wire with a resistance temperature coefficient of ≤100ppm / °C; the conductive plastic resistance film layer is a resistance film layer formed by printing conductive plastic resistance slurry on the working surface of the conductive skeleton and the precision resistance wire and curing it.

3. The high-precision, long-life composite contact linear displacement sensor according to claim 2, characterized in that: The conductive plastic resistor paste comprises graphite, carbon black and DPO resin.

4. The high-precision, long-life composite contact linear displacement sensor according to claim 1, characterized in that: The resistance values ​​of all corresponding parts of the conductive plastic resistance film layer located between two adjacent trimming grooves are the same.

5. The high-precision, long-life composite contact linear displacement sensor according to claim 1, characterized in that: The elastic clamping ring comprises an elastic washer and two fixed washers arranged on both sides of the elastic washer.

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