JP2017087750A - Stroke sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stroke sensor excellent in responsiveness in braking at an initial stage.SOLUTION: A stroke sensor comprises: a magnet 10 rotationally driven about a rotary shaft 12; a magnetic detection part 20 disposed facing the magnet 10, for detecting a change in a magnetic field caused by the magnet 10; an output calculation part 30 for calculating an output value corresponding to a rotation angle of the rotary shaft on the basis of the change detected by the magnetic detection part 20; and a correction processing part 40 for performing a correction processing to increase an output characteristics (output value/rotation angle) at an initial part of the rotation angle.SELECTED DRAWING: Figure 1

Description

  It relates to a stroke sensor.

  As a conventional technique, a stroke sensor that outputs a control signal related to braking based on an operation of a brake pedal is known. For example, the stroke sensor includes a magnet, two detection units, a first output unit, and a second output unit. The magnet is fixed to the shaft, and rotates around the shaft according to the depression operation of the brake pedal. The two detectors independently detect the rotation of the magnet. The first output unit generates and outputs two linear signals that continuously represent changes in the rotational operation from the two results detected by the two detection units. In addition, the second output unit has two on / off values representing the change in the rotational operation in binary values based on the threshold value provided for each result from the two results detected by the two detection units. An OFF signal is generated and output (see Patent Document 1).

  The stroke sensor includes an actuator, a first detection determination unit, a second detection determination unit, a first calculation processing unit, a second calculation processing unit, a linear signal output unit, and an ON / OFF signal output unit. And an external input determination unit. In the arithmetic processing unit, the first arithmetic processing unit inputs a detection signal output from the first detection unit and a detection signal output from the second detection unit, respectively, and a predetermined voltage range is determined from these detection signals. Linear signals that take (for example, 0 V to 5 V) are generated. The linear signal output unit outputs the two linear signals generated by the first arithmetic processing unit to the brake electronic control unit.

JP 2012-91700 A

  As described above, the stroke sensor of Patent Document 1 outputs a linear signal generated based on the operation amount of the brake pedal from the linear signal output unit. This linear signal is output to the brake ECU and used for lighting control of the brake lamp and the like. However, when the linear signal from the stroke sensor is used as a control signal for a by-wire type brake device, there is a problem in response when the brake pedal is stepped on. That is, when the signal from the stroke sensor is a linear signal, there is a problem that quick feedback to the brake system is difficult because the response of the hydraulic mechanism is poor when the brake pedal is depressed.

  Accordingly, an object of the present invention is to provide a stroke sensor having excellent responsiveness when a brake is depressed.

[1] In order to achieve the above object, the present invention provides a magnet that is driven to rotate about a rotation axis, and a magnetism detection unit that is disposed opposite to the magnet and detects a change in a magnetic field by the magnet. An output calculation unit that calculates an output value corresponding to the rotation angle of the rotating shaft based on a change in the magnetic field detected by the magnetic detection unit, and an output characteristic (output value / output value) of the rising portion of the rotation angle in the output value. And a correction processing unit that performs a correction process for increasing the rotation angle).

[2] The stroke sensor according to [1], wherein the rotation shaft is connected to a brake pedal mechanism and is driven to rotate in conjunction with movement of the brake pedal mechanism.

[3] The stroke sensor according to [2] above, wherein the rising portion of the rotation angle is a region corresponding to the time when the brake pedal is stepped on.

  ADVANTAGE OF THE INVENTION According to this invention, the stroke sensor excellent in the responsiveness at the time of brake depression can be provided.

FIG. 1 is a schematic configuration diagram showing a vehicle brake system having a stroke sensor according to an embodiment of the present invention. FIG. 2 is a schematic perspective view showing the configuration of the magnet and magnetic detection IC of the stroke sensor according to the embodiment of the present invention. FIG. 3 is a circuit diagram showing a circuit configuration example of the magnetic detection IC of the stroke sensor according to the embodiment of the present invention. 4A shows detection signals from each MR element of the magnetic detection IC of the stroke sensor according to the embodiment of the present invention, and FIG. 4B shows a relationship between the rotation angle θ and the output value V. FIG. 4C is a diagram illustrating the relationship between the rotation angle θ output from the correction processing unit, the output value Vout, and the brake signal Sd. FIG. 5 is a schematic configuration diagram of a by-wire type brake system in which a brake signal Sb is input and brake control is performed according to the depression amount (rotation angle θ) of the brake pedal of the stroke sensor according to the embodiment of the present invention. is there.

(Summary of Embodiments of the Present Invention)
A stroke sensor 1 according to an embodiment of the present invention includes a magnet 10 that is driven to rotate about a rotation shaft 12, and a magnetic detection unit 20 that is disposed opposite to the magnet 10 and detects a change in a magnetic field by the magnet 10. An output calculation unit 30 that calculates an output value V1 corresponding to the rotation angle θ of the rotary shaft 12 based on a change in the magnetic field detected by the magnetic detection unit 20, and an output characteristic of a rising portion of the rotation angle θ in the output value V1. And a correction processing unit 40 that performs a correction process for increasing (output value / rotation angle), and is configured to output an output value Vout having excellent responsiveness at the rising portion.

(Schematic configuration of brake system)
FIG. 1 is a schematic configuration diagram showing a vehicle brake system having a stroke sensor according to an embodiment of the present invention. The stroke sensor 1 according to the embodiment of the present invention is used to detect the movement of the brake pedal mechanism 60 in a by-wire brake system as shown in FIG. In particular, the rotating shaft 12 of the magnet 10 is connected to the brake pedal mechanism 60 and is driven to rotate in conjunction with the movement of the brake pedal mechanism 60. The rising portion of the rotation angle θ is a region corresponding to the time when the brake pedal 62 is depressed. Thereby, in the by-wire type brake system, the stroke sensor 1 can be excellent in responsiveness when the brake is stepped on.

  FIG. 2 is a schematic perspective view showing configurations of the magnet 10 and the magnetic detection IC 50 of the stroke sensor according to the embodiment of the present invention. In the present embodiment, the magnetic detection unit 20, the output calculation unit 30, and the correction processing unit 40 are, for example, a packaged magnetic detection IC 50 as shown in FIG.

(Magnet 10)
As shown in FIG. 2, the magnet 10 is a disk-shaped permanent magnet, and a rotation shaft 12 is provided at the center. The magnet 10 is rotatable about the rotation shaft 12.

  As shown in FIG. 2, the magnet 10 is magnetized in a disk-like radial direction to form an N pole and an S pole. The magnetic flux φ of the magnet 10 goes from the N pole to the S pole. As shown in FIG. 2, a part of the magnetic flux φ passes through the magnetic sensing surface 55 of the magnetic detection IC 50, so that the magnetic flux φ of the magnet 10 rotates on the magnetic sensing surface 55. As a result, when the magnetic detection IC 50 is an MR element, the output changes with a change in magnetic field (change in the direction of magnetic flux), and the rotation angle θ can be detected.

  The magnet 10 is, for example, a permanent magnet such as an alnico magnet, a ferrite magnet, or a neodymium magnet, or a magnetic material such as a ferrite-based, neodymium-based, samakoba-based, or samarium-iron-nitrogen-based material, polyamide-based, polyphenylene sulfide (PPS), or the like. And a synthetic magnet material mixed into a desired shape. In the present embodiment, the magnet 10 uses a plastic magnet.

(Magnetic detector 20)
FIG. 3 is a circuit diagram showing a circuit configuration example of the magnetic detection IC of the stroke sensor according to the embodiment of the present invention. The magnetic detection unit 20 has a configuration in which two full bridges constituted by MR elements are arranged with a rotation angle of 45 °. An intermediate voltage is input to the operational amplifier (differential amplifier) OP1 from the nodes 215b and 215d of the first MR bridge 210 (MR elements 211, 212, 213, and 214), and the detection signal S1 can be detected as a differential signal. ing. Similarly, intermediate voltages are input to the operational amplifier (differential amplifier) OP2 from the nodes 225b and 225d of the second MR bridge 220 (MR elements 221, 222, 223, and 224), and the detection signal S2 can be detected as a differential signal. It is configured. Note that the reference voltage Vcc is applied to the nodes 215a and 225a, and the nodes 215c and 225c are grounded (GND). The detection signal S1 and the detection signal S2 are output to the output calculation unit 30.

  Here, FIG. 4A shows detection signals from the MR elements of the magnetic detection IC of the stroke sensor according to the embodiment of the present invention. The detection signal S1 and the detection signal S2 are sine wave signals having a phase difference of 45 °. The sine wave signal is a sine wave having a period of π due to rotation of the N pole and S pole of the magnet 10. In the present embodiment, for example, a range where the rotation angle θ is from zero to π / 4 can be used.

(Output calculation unit 30)
The output calculation unit 30 receives detection signals S1 and S2 having a phase difference of 45 ° as changes in the magnetic field of the magnet 10 (changes in the direction of magnetic flux). The output calculation unit 30 performs an Arctan process that takes the arc tangent by dividing the two detection signals S1 and S2, for example, by referring to the Arctan table stored as a table in the storage unit, to change the magnetic field The output value V based on (change in magnetic flux direction) can be calculated and calculated. Here, FIG. 4B is a diagram showing the relationship between the rotation angle θ and the output value V, and the calculated output value V is a linear output V corresponding to the rotation operation angle of the brake pedal 62. .

(Correction processor 40)
The correction processing unit 40 performs nonlinear conversion processing. This non-linear conversion processing can be performed by sampling an input signal at a predetermined period and outputting an output corresponding to the input signal with reference to a predetermined conversion table. In a magnetic detection IC package with a built-in correction processing unit that performs non-linear conversion processing, a predetermined conversion table can be changed for the magnetic detection IC by an external write adjustment function. The output can be made non-linear. Further, non-linear conversion can be performed by hard logic using a known non-linear conversion circuit.

  FIG. 4C is a diagram illustrating the relationship between the rotation angle θ output from the correction processing unit, the output value Vout, and the brake signal Sd. In the rotation angle θ, correction processing (nonlinear conversion processing) for increasing the output characteristics (output value / rotation angle) is performed in the region from 0 to θ1, which is the rising portion of the rotation angle θ. That is, in the region of the rotation angle θ from 0 to θ1, the output value Vout has a larger slope than the linear output V shown in FIG. Here, θ1 is set to be equal to or greater than the angle at which the braking operation starts in a later-described by-wire brake system. Thereby, the rising value of the rotation angle θ is improved, and the output value Vout can improve the sensitivity at the time of depressing the brake and have excellent responsiveness at the time of depressing the brake in the by-wire brake system. .

(Brake pedal mechanism 60)
As shown in FIG. 1, the brake pedal mechanism 60 is a brake pedal device provided in the vehicle 5, and includes a brake pedal 62 that the driver steps on to perform a brake operation. The brake pedal 62 is rotatably supported by a rotation center 64 provided on the vehicle 5 side, and depresses from a predetermined position and rotates to the rotation center 64 to perform a brake operation of the vehicle 5.

  The rotating shaft 12 of the magnet 10 is connected to the brake pedal mechanism 60. For example, as shown in FIG. 1, the rotation shaft 12 of the magnet 10 is connected to the rotation center 64 of the brake pedal 62 and rotates in conjunction with the rotation of the brake pedal 62. The connection between the rotating shaft 12 of the magnet 10 and the brake pedal mechanism 60 is not limited to this, and the rotating shaft 12 and the brake pedal 62 are rotatably connected via a transmission mechanism such as a link mechanism or a gear mechanism. It may be a configuration.

(Control unit 70)
Based on the output from the stroke sensor 1, the control unit 70 generates a brake signal Sb for controlling the by-wire brake system 100, a stop lamp signal for controlling lighting of a vehicle stop lamp, and the like at a predetermined timing. Is output. The brake signal Sb for controlling the by-wire brake system 100 is generated based on the output value Vout input from the correction processing unit 40 described above. The brake signal Sb is a non-linear output signal similar to the output value Vout shown in FIG. 4C. For example, the brake signal Sb is a signal obtained by level conversion of the output voltage in accordance with the specifications of the brake system 100.

  The control unit 70 includes, for example, a CPU (Central Processing Unit) that performs predetermined calculation, processing execution, and the like according to a stored program, a RAM (Random Access Memory) that is a semiconductor memory, a ROM (Read Only Memory), and the like. This is a microcomputer. In this ROM, for example, a program for operating the control unit 70 and various parameters are stored. Moreover, the control part 70 is provided with the interface part for communicating via the vehicle-mounted LAN with various vehicle equipment of a vehicle.

  The stroke sensor 1 according to the embodiment of the present invention is applied to a by-wire brake system, and the control unit 70 generates a brake signal Sb corresponding to the depression operation amount (rotation angle θ) of the brake pedal 62. Brake control is performed by outputting to the brake system 100.

(Brake system 100)
FIG. 5 is a schematic configuration diagram of a by-wire type brake system in which a brake signal Sb is input and brake control is performed according to the depression amount (rotation angle θ) of the brake pedal of the stroke sensor according to the embodiment of the present invention. is there.

  The by-wire brake system 100 includes a motor-driven cylinder device 110 as an electric hydraulic pressure generator. The motor drive cylinder device 110 generates brake hydraulic pressure to be supplied to the wheel cylinder 200a of the disc brake 200 based on the brake signal Sb corresponding to the depression amount (rotation angle θ) of the brake pedal 62 detected by the stroke sensor 1. .

  In the brake system 100, a servo motor 120 and a gear box 130 connected to the servo motor 120 are integrally provided, and torque is transmitted to the gear box 130 via a ball screw mechanism so as to be axially aligned. There is provided a threaded rod 140 that is displaced, and a first piston 150a and a second piston 150b that are coaxially arranged in series with the threaded rod 140.

  As a result, the servo motor 120 rotates in accordance with the depression operation amount (rotation angle θ) of the brake pedal 62, and the rotational force is converted into the axial force of the threaded rod 140 via the gear box 130, and the first piston. 150a moves linearly. Thus, the by-wire type brake system 100 is configured in which the brake oil pressure is generated by the motor-driven cylinder device 110 in accordance with the depression amount of the brake pedal 62.

(Operation of the brake system 100)
When the driver depresses the brake pedal 62, the servo motor 120 is rotationally driven by the brake signal Sb shown in FIG. The rotational force is converted to the axial force of the threaded rod 140 via the gear box 130, and the first piston 150a and the second piston 150b move linearly. Here, the oil in the first oil chamber 16 a and the second oil chamber 16 b flows into the reservoir 17.

  The reservoir 17 is for uniformly transmitting hydraulic pressure to a plurality of pistons. For this reason, when the brake pedal 62 is initially depressed, the oil flows into the reservoir 17, so that the hydraulic pressure is not transmitted from the first oil chamber 16a and the second oil chamber 16b to the wheel cylinder 200a of the disc brake 200.

  However, in the stroke sensor 1 according to the present embodiment, as shown in FIG. 4C, the relationship between the stepping operation amount (rotation angle θ), the output value Vout, and the brake signal Sb has nonlinear characteristics. That is, at the start of depression of the brake pedal 62, the output of the brake signal Sb is larger than the linear characteristic. For this reason, when the depression of the brake pedal 62 is started, the first piston 150a and the second piston 150b are largely driven, so that the oil flows into the reservoir 17 quickly.

  The region where the correction processing (nonlinear conversion processing) is performed by the correction processing unit 40 and the output characteristic (output value / rotation angle) is increased is up to the angle θ1 or more at which the braking operation shown in FIG. It has become. For this reason, the responsiveness of the hydraulic mechanism is good when the brake pedal 62 is depressed, and quick feedback to the brake system is possible in the by-wire system.

(Effect of embodiment)
The stroke sensor 1 according to the present embodiment has the following effects.
(1) The stroke sensor 1 according to the embodiment of the present invention is used for detecting the movement of the brake pedal mechanism 60 in the brake system as shown in FIG. In particular, the rotating shaft 12 of the magnet 10 is connected to the brake pedal mechanism 60 and is driven to rotate in conjunction with the movement of the brake pedal mechanism 60. The rising portion of the rotation angle θ is a region corresponding to the time when the brake pedal 62 is depressed. Thereby, the stroke sensor 1 can be made excellent in the responsiveness at the time of brake depressing.
(2) The stroke sensor 1 performs nonlinear conversion processing by the correction processing unit 40. This non-linear conversion process is a correction process (non-linear conversion process) for increasing the output characteristics (output value / rotation angle) in the region from 0 to θ1, which is the rising portion of the rotation angle θ, at the rotation angle θ. That is, in the region of the rotation angle θ from 0 to θ1, the output value Vout has a larger slope than the linear output V shown in FIG. Here, θ1 is set to be equal to or larger than the angle at which the braking operation starts in the by-wire brake system. As a result, the output value Vout has improved rising characteristics of the rotation angle θ.
(3) By applying the stroke sensor 1 according to the embodiment of the present invention to a by-wire type brake system, it is possible to improve the sensitivity when the brake is stepped on and to have excellent responsiveness when the brake is stepped on. . Thereby, the responsiveness of the hydraulic mechanism is good when the brake pedal 62 is depressed, and quick feedback to the brake system is possible in the by-wire system.

  As mentioned above, although embodiment of this invention was described, these embodiment is only an example and does not limit the invention which concerns on a claim. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the scope of the present invention. In addition, not all the combinations of features described in these embodiments are essential to the means for solving the problems of the invention. Furthermore, these embodiments are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Stroke sensor 5 ... Vehicle 10 ... Magnet 12 ... Rotating shaft 16a ... 1st oil chamber 16b ... 2nd oil chamber 17 ... Reservoir 20 ... Magnetic detection part 30 ... Output calculating part 40 ... Correction process part 55 ... Magnetic sensing surface 60 ... Brake pedal mechanism 62 ... Brake pedal 64 ... Rotation center 70 ... Control unit 100 ... Brake system 110 ... Motor drive cylinder device 120 ... Servo motor 130 ... Gear box 140 ... Threaded rod 150a ... First piston 150b ... Second piston 200 ... disc brake 200a ... wheel cylinder 210 ... bridges 211, 212, 213, 214 ... MR elements 215a, 215b, 215c, 215d ... node 220 ... bridges 221, 222, 223, 224 ... MR elements 225a, 225b, 225c, 225d ... Node S1 ... Detection signal S ... detection signal Sb ... brake signal V ... output value V1 ... output value Vout ... output value theta ... rotation angle

Claims (3)

A magnet that is driven to rotate around the rotation axis;
A magnetic detection unit disposed opposite to the magnet and detecting a change in a magnetic field by the magnet;
An output calculation unit that calculates an output value corresponding to a rotation angle of the rotation shaft by a change in the magnetic field detected by the magnetic detection unit;
A correction processing unit for performing a correction process for increasing an output characteristic (output value / rotation angle) of the rising portion of the rotation angle in the output value;
A stroke sensor characterized by comprising:   The stroke sensor according to claim 1, wherein the rotation shaft is connected to a brake pedal mechanism and is driven to rotate in conjunction with movement of the brake pedal mechanism.   The stroke sensor according to claim 2, wherein the rising portion of the rotation angle is a region corresponding to depression of the brake pedal.

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