Key switch

Abstract

To provide a key switch that exhibits high linearity with respect to stroke and is less susceptible to the effects of temperature and other factors. [Solution] The key switch 100 comprises a key housing 10, a magnetic field generator 20, and a magnetic sensor 30. The key housing has a first part 11 that can be fixed to a substrate and a second part 12 that can move in a first direction X relative to the first part. The magnetic field generator is fixed to the second part and can move in the first direction together with the second part. The magnetic sensor is fixed to the first part at any position in the radial direction perpendicular to an axis A extending in the first direction with respect to the magnetic field generator, and is configured to detect changes in the angle of the magnetic field generated in the magnetic sensor when the magnetic field generator moves in the first direction.

Description

Technical Field

[0001] The present disclosure relates to a key switch.

Background Art

[0002] A plurality of key switches are arranged on a keyboard. Various methods have been studied as means for detecting that a key switch has been pressed.

[0003] For example, Japanese Patent Laid-Open No. 55-105916 discloses a method of reading that a key switch has been pressed by installing a permanent magnet that generates a magnetic field in the key switch and utilizing the change in the intensity of the magnetic field detected by a magnetic sensor when the key switch is pressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One object of the present disclosure is to provide a key switch that has high linearity with respect to the stroke of the key switch and is less affected by factors such as temperature.

Means for Solving the Problems

[0006] The present disclosure provides the following technology.

[0007] A key switch according to the first embodiment comprises a key housing, a magnetic field generator, and a magnetic sensor. The key housing has a first portion that can be fixed to a substrate and a second portion that can move in a first direction relative to the first portion. The magnetic field generator is fixed to the second portion and can move in the first direction together with the second portion. The magnetic sensor is fixed to the first portion at any position in the radial direction perpendicular to an axis extending in the first direction with respect to the magnetic field generator, and is configured to detect changes in the angle of the magnetic field generated in the magnetic sensor when the magnetic field generator moves in the first direction. [Effects of the Invention]

[0008] The key switch according to the above embodiment exhibits high linearity with respect to stroke and is less susceptible to the effects of temperature and other factors. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of the key switch according to the first embodiment. [Figure 2] This is a circuit diagram of an example of a magnetic sensor according to the first embodiment. [Figure 3] This is a plan view showing a portion of the key switch according to the first embodiment. [Figure 4] This is a cross-sectional view illustrating the operation of the key switch according to the first embodiment. [Figure 5] This is a plan view illustrating the operation of the key switch according to the first embodiment. [Figure 6] This figure illustrates a first example of the calculation processing of the calculation unit of the key switch according to the first embodiment. [Figure 7] This figure illustrates a second example of the calculation processing of the calculation unit of the key switch according to the first embodiment. [Figure 8] This figure shows an example of the relationship between the stroke amount and output of a key switch according to the first embodiment. [Figure 9] This is a cross-sectional view of the key switch according to Comparative Example 1. [Figure 10]This figure shows an example of the relationship between the stroke amount and output of the key switch in Comparative Example 1. [Figure 11] This is a cross-sectional view of a key switch according to the first modified example. [Modes for carrying out the invention]

[0010] The following description of this embodiment will be explained in detail with reference to the drawings as appropriate. The drawings used in the following description may be enlarged for convenience to make the configuration easier to understand, and the dimensional ratios of each component may differ from those in reality. The materials, dimensions, etc., exemplified in the following description are examples only, and this disclosure is not limited to them. It is possible to modify and implement them as appropriate within the scope of achieving the effects of this disclosure.

[0011] For the sake of explanation, directions are defined as follows: The direction in which the magnetic field generator 20 can move is defined as the X direction. The X direction is an example of a first direction. The Z direction is defined as the direction in which a straight line extends from axis A, which extends in the X direction relative to the magnetic field generator 20, to the magnetic sensor 30 (for example, the magnetosensitive surface of the magnetic sensor 30) at the shortest distance. The Z direction is an example of a second direction. The Y direction is defined as the direction perpendicular to the X and Z directions. The Y direction is an example of a third direction.

[0012] Figure 1 is a cross-sectional view of the key switch 100. The key switch 100 comprises a key housing 10, a magnetic field generator 20, and a magnetic sensor 30. The key switch 100 may also have a circuit board 40 and a calculation unit 50. The key housing 10, the magnetic field generator 20, and the magnetic sensor 30 are removable from the circuit board 40 and the calculation unit 50.

[0013] The key housing 10 has a first part 11 and a second part 12. The first part 11 is fixable to the substrate 40. The second part 12 is movable in the X direction relative to the first part 11. A keypad may be provided on the side of the second part 12 that is farther from the substrate 40. The second part 12 moves in the X direction, for example, when the keypad is pressed in the X direction.

[0014] The magnetic field generator 20 is fixed to the second part 12. The magnetic field generator 20 can move in the X direction along the axis A together with the second part 12. The axis A passes through the center of the magnetic field generator 20 when viewed in plan from the X direction and extends in the X direction. The magnetic field generator 20 may be a member capable of generating a magnetic field. The magnetic field generator 20 may include, for example, a magnet as illustrated in FIG. 1. In the case of the embodiment illustrated in FIG. 1, the magnets included in the magnetic field generator 20 are magnetized such that the N poles and S poles are arranged in the X direction. Note that the magnetization direction and the number of poles of the magnet are not particularly limited and may be appropriately selected. As another example, the magnetic field generator 20 may be configured to include, for example, an electromagnet.

[0015] The magnetic sensor 30 is fixed to the first part 11. The magnetic sensor 30 is at any position in the radial direction orthogonal to the axis A. The magnetic sensor 30 is arranged at a position where it can detect the magnetic field generated by the magnetic field generator 20. As an example, the magnetic sensor 30 may be arranged at a position facing the magnetic field generator 20. The magnetic sensor 30 is installed, for example, on a support substrate 31 extending in the XY directions. The support substrate 31 is connected to, for example, a terminal 32. The terminal 32 serves as an electrical contact between the substrate 40 and the magnetic sensor 30.

[0016] The magnetic sensor 30 detects the direction of the magnetic field generated on the magnetosensitive surface 30A. The magnetosensitive surface 30A is, for example, parallel to the XY plane. The magnetic sensor 30 detects the direction of the magnetic field in the XY plane. For example, when any direction in the XY plane is taken as a reference direction (for example, the X direction), the magnetic sensor 30 detects the angle of the magnetic field with respect to the reference direction. The magnetic sensor 30 is, for example, an angle sensor that detects the angle of the magnetic field generated on the magnetic sensor 30. The angle of the magnetic field changes as the magnetic field generator 20 moves in the X direction.

[0017] The magnetic sensor 30 includes, for example, a magnetoresistive element. The magnetoresistive element may be, for example, an anisotropic magnetoresistive element (e.g., an AMR (Anisotropic Magneto Resistance) element, etc.), or a spin valve type magnetoresistive element (e.g., a GMR (Giant Magneto Resistance) element, a TMR (Tunnel Magneto Resistance) element, etc.).

[0018] The magnetoresistive element is configured such that its resistance value changes depending on the direction in which a magnetic field is applied. For example, in the case of a spin valve type magnetoresistive element such as TMR or GMR, the magnetoresistive element includes a fixed layer with a fixed magnetization direction, a free layer whose magnetization direction can change according to the direction of the applied magnetic field, and a gap layer disposed between the fixed layer and the free layer. In a spin valve type magnetoresistive element, the resistance value changes according to the angle formed by the magnetization direction of the free layer with respect to the magnetization direction of the magnetization fixed layer. In a spin valve type magnetoresistive element, the resistance value shows a minimum value when the magnetization directions of the fixed layer and the free layer are parallel, and shows a maximum value when the magnetization directions of the fixed layer and the free layer are antiparallel.

[0019] Also, for example, in the case of an anisotropic magnetoresistive element such as AMR, the resistance value changes according to the angle formed by the direction of the applied magnetic field and the direction of the current flowing through the element.

[0020] The magnetic sensor 30 may include a plurality of magnetoresistive elements. The plurality of magnetoresistive elements may be connected, for example, by a bridge circuit. The magnetic sensor 30 may also be a Hall sensor. A Hall sensor is an element that outputs an electrical signal corresponding to the ambient magnetic field using the Hall effect.

[0021] For the sake of explanation, the following example will describe the use of a spin-valve type magnetoresistive element. For example, the magnetic sensor 30 may use multiple magnetoresistive elements with different magnetization directions of the stationary layers to simultaneously output a first signal corresponding to a change in the angle of the magnetic field and a signal that is out of phase with the first signal. Figure 2 is a circuit diagram of an example of the magnetic sensor 30. Each resistor in Figure 2 represents a magnetoresistive element, and the arrows indicate the magnetization direction of the stationary layer of the magnetoresistive element. The magnetic sensor 30 shown in Figure 2 is configured to output a first signal corresponding to a change in the angle of the magnetic field and a second signal that is out of phase with a 90° difference. As another example, the magnetic sensor may be configured to simultaneously output a first signal corresponding to a change in the angle of the magnetic field and a third signal that is out of phase with a 180° difference with the first signal. For example, by rotating the magnetization directions of the stationary layers R1 and R2 shown in Figure 2 by 90°, the first signal and the third signal can be output simultaneously.

[0022] Figure 3 is a plan view showing a portion of the key switch 100. Figure 3 is a plan view of the magnetic field generator 20 and the magnetic sensor 30 from the Z direction.

[0023] When viewed from the Z direction, the Y-direction center C30 of the magnetic sensor 30 does not have to coincide with the Y-direction center C20 of the magnetic field generator 20. The offset between the centers C20 and C30 makes it easier for the magnetic sensor 30 to detect the direction of the magnetic field, which changes in response to the movement of the magnetic field generator 20 in the X direction. When viewed from the Z direction, the magnetic sensor 30 does not have to coincide with the magnetic field generator 20. Here, "the magnetic sensor 30 and the magnetic field generator 20 do not coincide" means that the entire magnetic sensor 30 and the entire magnetic field generator 20 do not coincide. Furthermore, "the magnetic sensor 30 and the magnetic field generator 20 do not coincide" means that they do not coincide whether the second part 12 of the key switch 100 is pressed or not.

[0024] The shortest distance D1 between the magnetic field generator 20 and the magnetic sensor 30 may be set based on, for example, the length S1 of the magnetic field generator 20 in the X direction. For example, when the shortest distance D1 is the first variable and the length S1 is the second variable, a relationship expressed by a predetermined equation may hold between the first and second variables. The shortest distance D1 between the magnetic field generator 20 and the magnetic sensor 30 may be, for example, 0.9 mm or more and 9.0 mm or less. The shortest distance D1 between the magnetic field generator 20 and the magnetic sensor 30 may be defined, for example, as the shortest distance between a virtual plane including the magnetosensitive surface 30A of the magnetic sensor 30 and the portion of the magnetic field generator 20 facing the virtual plane, or as the shortest distance between the plane and the axis A described above.

[0025] The circuit board 40 is designed to allow the key housing 10 to be attached and detached. The material, size, shape, etc., of the circuit board 40 are not particularly limited and may be appropriately selected according to the specifications required for the keyboard.

[0026] The arithmetic unit 50 is electrically connected to the magnetic sensor 30. The arithmetic unit 50 may be part of a microcontroller (MCU) responsible for keyboard control, part of an application-specific integrated circuit (ASIC) provided for each key switch, or a combination of these. The arithmetic unit 50 may be implemented by a central processing unit (CPU) capable of executing software that performs specific arithmetic processing (specifically, for example, instructions that constitute the software), or it may include an arithmetic circuit that performs specific arithmetic processing. The arithmetic unit 50 may include, for example, an operational amplifier that outputs the differential of two signals.

[0027] Next, the operation of the key switch 100 will be explained. Figure 4 is a cross-sectional view illustrating the operation of the key switch 100. Figure 5 is a plan view illustrating the operation of the key switch 100. In Figures 4 and 5, the left figure shows the state in which the key switch 100 is not pressed, and the right figure shows the state in which the key switch 100 is pressed.

[0028] When the key switch 100 is pressed, the magnetic field generator 20 moves in the X direction together with the second part 12.

[0029] The maximum value T1 of the moving distance of the magnetic field generator 20 in the X direction may satisfy the relationship of 0.50×S1 < T1 < 1.50×S1 with respect to the length S1 of the magnetic field generator 20 in the X direction, may satisfy the relationship of 0.75×S1 < T1 < 1.25×S1, or may satisfy the relationship of 0.90×S1 < T1 < 1.10×S1. When the length of the magnetic field generator 20 in the X direction is within the range of ±25% of the maximum value T1 of the moving distance, the linearity of the angle of the magnetic field detected by the magnetic sensor 30 with respect to the movement of the key switch is high, and the key size can be reduced. For example, when the relationship of 0.90×S1 < T1 < 1.10×S1 is satisfied, the length S1 and the maximum value T1 of the moving distance substantially coincide.

[0030] As shown in FIG. 5, a magnetic field B is generated from the magnetic field generator 20. The arrow shown in FIG. 5 indicates the direction of the magnetic field (the direction of the magnetic flux) detected by the magnetic sensor 30. The magnetic field B is generated so as to flow back from the first end to the second end of the magnetic field generator 20 in the X direction. When the position of the magnetic field generator 20 in the X direction changes, the direction of the magnetic field generated in the magnetic sensor 30 also changes. When the position of the magnetic field generator 20 in the X direction changes, when any direction in the XY plane is used as a reference direction (for example, the X direction), the angle of the magnetic field detected at the position of the magnetic sensor 30 with respect to the reference direction changes. The magnetic sensor 30 detects the angle of the magnetic field around the magnetic sensor 30.

[0031] The magnetic sensor 30 may be configured such that a magnetic field equal to or higher than the saturation magnetic field of the magnetoresistive effect element constituting the magnetic sensor 30 is applied as the magnetic field B. Here, "equal to or higher than the saturation magnetic field" means that the absolute value of the intensity of the magnetic field B in the magnetic sensor 30 is equal to or higher than the absolute value of the saturation magnetic field. The saturation magnetic field means that the intensity of the magnetic field B in the magnetic sensor 30 is the intensity at which the magnetization of the free layer constituting the magnetoresistive effect element is saturated (the magnitude of the magnetization of the free layer hardly changes).

[0032] The signal detected by the magnetic sensor 30 is sent to the calculation unit 50. The calculation unit 50 performs calculation processing. The calculation unit 50 may implement calculation processing by a combination of circuit elements.

[0033] For example, when the magnetic sensor 30 simultaneously outputs a first signal corresponding to a change in the angle of the magnetic field and a second signal that is 90° out of phase with respect to the first signal, the calculation unit 50 performs first signal processing. Figure 6 is a diagram illustrating the first signal processing in the calculation unit 50. In Figure 6, Vout1 is the first signal and Vout2 is the second signal. For example, the first signal draws a sine wave, and the second signal draws a cosine wave. By calculating the arctans of the first and second signals, the angle θ of the magnetic field can be determined from the output of the magnetic sensor 30. Specifically, the angle θ of the magnetic field can be calculated as θ = arctan(sinθ (=Vout1) / cosθ (=Vout2)). As shown in Figure 6, it can be seen that θ calculated from the sensor output exhibits good linearity.

[0034] For example, if the magnetic sensor 30 simultaneously outputs a first signal corresponding to a change in the angle of the magnetic field and a third signal that is 180° out of phase with respect to the first signal, the calculation unit 50 performs a second signal processing. Figure 7 is a diagram illustrating the second signal processing in the calculation unit 50. In Figure 7, Vout1 is the first signal and Vout2 is the third signal. By calculating the difference between the first signal and the third signal within a specific range, the correspondence between the sensor output signal and the angle θ of the magnetic field within that range can be determined. As shown in Figure 7, it can be seen that θ calculated from the sensor output exhibits good linearity.

[0035] As described above, in the key switch 100 according to this embodiment, the change in the angle of the magnetic field accompanying the movement of the magnetic field generator 20 in the X direction is sensed using the magnetic sensor 30, thereby improving the linearity of the output from the magnetic sensor 30 with respect to the movement of the magnetic field generator 20 in the X direction.

[0036] Specifically, the magnetic sensor 30 senses the change in the magnetic field accompanying the movement of the magnetic field generator 20 in the X direction, and calculates the angle of the magnetic field at the position of the magnetic sensor 30. The relationship between the magnetic field angle θ and the displacement of the key switch 100 in the X direction may be expressed using, for example, a specific function, or it may be expressed using a table that shows the correspondence between the magnetic field angle θ and the displacement. As described above, since the linearity of the magnetic field angle θ calculated from the output signal of the magnetic sensor 30 is good, it is possible to accurately determine the magnetic field angle θ from the output signal of the magnetic sensor 30. For this reason, the amount of movement of the magnetic field generator 20 in the X direction can also be accurately determined based on the output signal of the magnetic sensor 30.

[0037] Figure 8 shows the relationship between the stroke amount and output of the key switch 100 according to this embodiment. The horizontal axis represents the displacement (stroke amount) of the magnetic field generator 20 in the X direction, and the vertical axis represents the output from the magnetic sensor 30. The vertical axis is normalized to a specified value. In Figure 8, it is normalized to the maximum output of the magnetic sensor 60 of Comparative Example 1, which will be described later. The specified value may be, for example, the maximum output of the magnetic sensor 30, or the maximum output of the magnetic sensor 60 of Comparative Example 1, which will be described later. As shown in Figure 8, in the key switch 100 according to this embodiment, the output from the magnetic sensor 30 is approximately linear with respect to the movement of the magnetic field generator 20 in the X direction.

[0038] Figure 9 is a cross-sectional view of a key switch 101 according to Comparative Example 1. The key switch 101 differs from the key switch 100 in that it has a magnetic sensor 60 instead of a magnetic sensor 30. The magnetic sensor 60 is installed on the substrate 40. The magnetic sensor 60 is positioned on the extension of axis A. The magnetic sensor 60 is a sensor that detects changes in the strength of a magnetic field.

[0039] Figure 10 shows the relationship between the stroke amount and output of the key switch 101 according to Comparative Example 1. The horizontal axis represents the displacement (stroke amount) of the magnetic field generator 20 in the X direction, and the vertical axis represents the output from the magnetic sensor 60. The vertical axis is normalized by the maximum output of the magnetic sensor 60. As shown in Figure 10, in Comparative Example 1, the output from the magnetic sensor 30 with respect to the movement of the magnetic field generator 20 in the X direction is nonlinear. The relationship between the distance (stroke) between the magnetic field generator 20 and the magnetic sensor 60 and the strength of the magnetic field detected by the magnetic sensor 60 is less linear compared to Figure 8. Therefore, when using the magnetic sensor 60 with the magnetic field strength according to Comparative Example 1, the stroke resolution is lower compared to this embodiment. In other words, this embodiment can detect how far the key switch is pressed with greater accuracy than Comparative Example 1.

[0040] As shown in Figure 8, the key switch 100 according to this embodiment can linearly convert the stroke amount in the X direction of the magnetic field generator 20 using the output from the magnetic sensor 30, thereby increasing the stroke resolution of the key switch 100.

[0041] Furthermore, since the key switch 100 senses the angle of the magnetic field with the magnetic sensor 30, it can cancel out the effects of temperature changes and is less susceptible to temperature fluctuations. In contrast, when the stroke amount is sensed by changes in the strength of the magnetic field, as in the key switch 101, it is susceptible to temperature changes. For example, if the magnetic sensor 60 itself has temperature characteristics, the output of the magnetic sensor 60 may fluctuate due to temperature changes. Also, if the magnetic field generator 20 itself has temperature characteristics, the magnetic field generated from the magnetic field generator 20 may fluctuate due to temperature changes. In either case, since temperature changes affect the output of the magnetic sensor 60, the stroke amount calculated based on that output is also susceptible to temperature changes.

[0042] Furthermore, while the key switch 101 senses changes in magnetic field strength, it is difficult to increase the amount of change in magnetic field strength, making it difficult to freely increase the output of the magnetic sensor 60. In contrast, the key switch 100 senses the angle of the magnetic field with the magnetic sensor 30, allowing for a large change in the resistance of the magnetic sensor 30.

[0043] Furthermore, by arranging the magnetic field generator 20 and magnetic sensor 30 inside the key housing 10, the key switch 100 can apply a large magnetic field to the magnetic sensor 30, thereby increasing the output range of the magnetic sensor 30. In addition, the absence of the magnetic sensor 30 on the circuit board 40 simplifies the circuit layout on the circuit board 40, thus simplifying the circuit board 40.

[0044] Up to this point, we have provided an example of the key switch 100 and explained its specific configuration. The key switch relating to this disclosure is not limited to this example configuration, and various modifications are possible within the scope of satisfying the intent of this disclosure.

[0045] Figure 11 is a cross-sectional view of the key switch 102 according to the first modified example. The key switch 102 differs from the key switch 100 in the configuration of the magnetic field generator 21.

[0046] The magnetic field generator 21 has multiple combinations of north and south poles. The magnetization of the magnetic sensor 30 rotates once in the XY plane each time a pair of north and south poles passes near the magnetic sensor 30. Therefore, the magnetic sensor 30 can count how many pairs of north and south poles have passed by determining how many rotations the magnetization has made. In other words, the magnetic sensor 30 senses the angle of the magnetic field and also functions as an encoder.

[0047] The key switch 102 according to the first modified example has the same effect as the key switch 100. [Explanation of symbols]

[0048] 10-key cabinet 11 Part 1 12 Part 2 20, 21 Magnetic field generator 30, 60 magnetic sensors 30A magnetically sensitive surface 31 Support substrate Terminal 32 40 circuit boards 50 Arithmetic section 100, 101, 102 key switches A-axis B magnetic field C20, C30 center D1 Shortest distance T1 Maximum distance traveled

Claims

1. It comprises a key housing, a magnetic field generator, and a magnetic sensor. The key housing has a first portion that can be fixed to the circuit board and a second portion that can move in a first direction relative to the first portion. The magnetic field generator is fixed to the second part and is movable in the first direction together with the second part. The magnetic sensor is fixed to the first portion at any position in the radial direction perpendicular to the axis extending in the first direction with respect to the magnetic field generator, and is configured to detect changes in the angle of the magnetic field generated in the magnetic sensor when the magnetic field generator moves in the first direction. Key switch.

2. The magnetic sensing surface of the magnetic sensor is parallel to a first plane perpendicular to the second direction to which a straight line connecting the axis and the magnetic sensor by the shortest distance extends. The key switch according to claim 1, wherein the magnetic sensor is configured to detect a change in the angle of the component of the magnetic field parallel to the first plane.

3. The key switch according to claim 1, wherein, when viewed from a second direction on which a straight line connecting the shaft and the magnetic sensor by the shortest distance extends, the center of the magnetic sensor in a third direction perpendicular to the first and second directions does not coincide with the center of the magnetic field generator in the third direction.

4. The key switch according to claim 3, wherein, when viewed from the second direction, the magnetic sensor does not overlap with the magnetic field generator.

5. The key switch according to claim 1, wherein the shortest distance between the magnetic field generator and the magnetic sensor is set based on the length of the magnetic field generator in the first direction.

6. The key switch according to claim 1, wherein the shortest distance between the magnetic field generator and the magnetic sensor is 0.9 mm or more and 9.0 m or less.

7. The key switch according to claim 1, wherein the length S1 of the magnetic field generator in the first direction and the maximum value T1 of the travel distance of the magnetic field generator in the first direction satisfy 0.50 × S1 < T1 < 1.50 × S1.

8. The key switch according to claim 7, wherein the length S1 and the maximum value T1 are substantially the same.

9. It also includes a calculation unit, The magnetic sensor is configured to output a first signal corresponding to a change in the angle of the magnetic field, and a second signal that is 90° out of phase with respect to the first signal. The key switch according to claim 1, wherein the calculation unit is configured to determine the angle of the magnetic field using the first signal and the second signal.

10. It also includes a calculation unit, The magnetic sensor is configured to output a first signal corresponding to a change in the angle of the magnetic field, and a third signal that is 180° out of phase with respect to the first signal. The key switch according to claim 1, wherein the calculation unit is configured to determine the angle of the magnetic field based on the difference between the first signal and the third signal.

11. The magnetic sensor has a magnetoresistive element whose resistance changes when a magnetic field is applied. The key switch according to claim 1, wherein the magnetic field generator is configured to apply a magnetic field to the magnetic sensor that is greater than or equal to the strength at which the resistance change of the magnetoresistive element saturates.

Images