JP5218855B2 - Data communication method and wheel state detection device - Google Patents

Description

  The present invention relates to a data communication method for transmitting different physical quantities over a common signal line. The present invention also relates to a wheel state detection device that transmits a physical quantity indicating the state of the wheel using such a data communication method.

  In an in-vehicle system such as an anti-lock braking system (ABS) or a vehicle stability controller, a rotational speed sensor is used to measure the rotational speed of a wheel in order to perform the control. The rotational speed sensor is disposed in the vicinity of the wheel, and the detection result is transmitted to the vehicle-mounted control device using a signal line. The wheel information includes, in addition to the rotation speed, the tire air pressure and the like, which is detected by an air pressure sensor or the like. In recent years, many sensors are mounted on vehicles, and the number is expected to increase further. Therefore, if signal lines are individually provided for each sensor, the number of signal lines becomes enormous. Therefore, for example, a technique has been proposed in which a plurality of pieces of information are transmitted through a common signal line, such as superimposing another detection result such as a detection result of an air pressure sensor on a signal line of a rotation speed sensor.

  Japanese Patent Laid-Open No. 2001-505691 (Patent Document 1) proposes a method for transmitting data supplied by a rotational speed sensor and additional data via a common signal line. This is to superimpose serial bit data between pulses using a pulsed rotational speed sensor signal as a trigger. Japanese Patent Laying-Open No. 2005-274310 (Patent Document 2) proposes a method of superimposing serial bit data during a high period of a pulse-like signal of approximately 50% duty that is output in response to wheel rotation. ing. This represents serial bit data by a superposed pulse that is larger than the pulse height of the pulse output according to the rotation of the wheel and narrower than the pulse.

JP-T-2001-505691 (second page, FIG. 1 etc.) Japanese Patent Laying-Open No. 2005-274310 (paragraphs 55 to 62, FIG. 10, etc.)

  These methods are excellent in that other information can be superimposed on the signal line of the rotation speed sensor. However, there is a possibility that information cannot be sufficiently superimposed when the rotation speed is high. That is, there is a possibility that the interval between pulses is shortened, making it difficult to generate serial bit data, or the high period of the pulse is shortened, making it difficult to generate a superimposed pulse. By providing a start bit, a stop bit, and a parity bit, serial data can be transmitted over a plurality of periods. However, since both the information transmission side and the reception side require a control function corresponding to the information transmission side, the scale of the signal processing device and the program may be increased.

  Therefore, it is desired to provide a data communication method capable of transmitting a plurality of information through a common signal line while suppressing an increase in the scale of a signal processing device or a program.

  A data communication method according to the present invention for solving the above-described problem is to transmit a first physical quantity at least by a period of a rectangular wave, and at a predetermined position of either a high level or a low level in one period of the rectangular wave A second physical quantity different from the first physical quantity is transmitted by a superposed pulse superimposed on the first physical quantity, and an increase or decrease of the second physical quantity transmitted by the previous period is represented by the number of superposed pulses in each period. The second physical quantity is transmitted.

  According to this feature, it is not necessary to transmit the value of the second physical quantity itself in each cycle of the rectangular wave, and it is sufficient to transmit a difference from the previous cycle. Therefore, the amount of information transmitted in each period of the rectangular wave is reduced. As a result, an increase in the size of the signal processing device or program is suppressed. Since the superimposition pulse indicating the second physical quantity is superimposed on the rectangular wave indicating the first physical quantity, a plurality of pieces of information can be transmitted through a common signal line.

  Here, it is preferable that two or more superimposing pulses can be superimposed in each cycle, and the increase / decrease number including zero is indicated by the number of pulses.

  Even when only one superimposed pulse is superimposed in each cycle, it is possible to indicate an increase / decrease, for example, by indicating an increase when there is a superimposed pulse and a decrease when there is no superimposed pulse. However, if two or more superimposed pulses are configured to be superposed in each cycle, for example, it may decrease when there are no superimposed pulses, increase when there are two, and indicate no increase or decrease when there is one. It becomes possible. That is, when there is no change in the second physical quantity, it is possible to suppress unnecessary vibration and transmit the second physical quantity satisfactorily. Alternatively, it is possible to indicate a reset state in which the second physical quantity is returned to the initial value when there is no superimposed pulse. The control device that receives the second physical quantity can obtain the second physical quantity more accurately by using this reset state as a reference.

  In the data communication method according to the present invention, it is preferable that the value of the second physical quantity is indicated based on the number of periods of the rectangular wave in a predetermined period and the number of pulses of the superimposed pulse.

  In addition to showing an increase / decrease from the previous cycle in each cycle of the rectangular wave, since the value of the second physical quantity can be obtained in a predetermined period, the control device that receives the second physical quantity does not track the increase / decrease each time. The second physical quantity can be obtained at a necessary timing.

  Here, it is preferable that the first physical quantity is a physical quantity indicating a rotation state of a wheel.

  For example, the physical quantity indicating the rotation speed as the rotation state of the wheel can be indicated by the period of the rectangular wave. A sensor for detecting the temperature of the wheel and the air pressure of the wheel is also provided in the vicinity of the wheel. By transmitting the physical quantity detected by these sensors as the second physical quantity, it is possible to transmit a plurality of information while suppressing an increase in transmission lines.

  Furthermore, it is preferable that the second physical quantity is a physical quantity indicating a lateral force applied to the wheel from a direction along a rotation axis direction of the wheel.

  In recent years, there is also a demand for detection of lateral force on a vehicle for use in a stable control device such as a side slip prevention device. Therefore, when a lateral force is transmitted as a second physical quantity, an increase in transmission lines is suppressed, It is preferable that information can be transmitted. As one embodiment, an alternating current that is output from the detection element according to the rotation of the detection object is arranged by opposing the detection element with a predetermined interval to the detection object fixed to the wheel. The period of the detection signal can be transmitted as the first physical quantity. Further, when a lateral force is applied to the wheel, the amplitude of the AC detection signal that fluctuates when the predetermined interval fluctuates can be transmitted as the second physical quantity. That is, two physical quantities obtained from the same detection element can be transmitted through a common signal line.

The characteristic configuration of the wheel state detection device according to the present invention for solving the above problems is as follows:
A rotation detection signal for generating a rotation detection signal of a rectangular wave having a period corresponding to the period of the detection signal as a signal for transmitting the first physical quantity based on an AC detection signal output according to the rotation of the wheel. A generator,
A second physical quantity different from the first physical quantity can be superimposed in each period of the rotation detection signal, representing an increase or decrease with respect to a value transmitted up to the previous period depending on the number of pulses superimposed in each period. An additional signal generation unit for generating an additional signal to be transmitted;
An output unit that superimposes the additional signal at a predetermined position of either the high level or the low level in one cycle of the rotation detection signal;
It is in the point provided with.

  The physical quantity indicating the rotation speed as the rotation state of the wheel can be indicated by the period of the rectangular wave, and many have been put into practical use. In recent years, detection of lateral force on a vehicle is also required for use in a stable control device such as a side slip prevention device. This lateral force can be detected not only by a yaw rate sensor mounted on the vehicle but also by a MEMS sensor built in the wheel. Since the sensor for detecting the rotational speed of the wheel is provided in the vicinity of the wheel, the lateral force detected by the MEMS sensor incorporated in the wheel or the like is transmitted as the second physical quantity, thereby suppressing an increase in the transmission line. Meanwhile, it is possible to provide a wheel rotation state detection device capable of transmitting a plurality of information.

Side view schematically showing the relationship between the rotating body, the object to be detected, and the rotating state detecting element Arrow view from direction II of detected object in FIG. Block diagram schematically showing a configuration example of a wheel state detection device Explanatory drawing which shows an example of the method of converting a detection signal into a digital count value Explanatory drawing which shows an example of the method of producing | generating a periodic signal Waveform diagram showing an example in which the amplitude (wave height) of the detection signal changes due to lateral force Waveform diagram schematically showing an example of increasing or decreasing information indicating lateral force Explanatory diagram showing the type of superimposed pulse The figure which shows an example which shows the value of lateral force with the number of periods of a rectangular wave, and the number of superposition pulses Flow chart showing an example of an output signal generation method The figure which shows the other example which shows the value of lateral force by the number of periods of a rectangular wave, and the number of superposition pulses Explanatory drawing which shows the other example of the method of producing | generating a periodic signal. Waveform diagram schematically showing another example in which the information indicating lateral force increases or decreases

[First Embodiment]
Hereinafter, the embodiment of the present invention detects the rotation state of a vehicle wheel, and outputs the rotation information to an ECU (electronic control units) that performs control such as ABS or an electronic stability control (ESC). A state detection device will be described as an example. As shown in FIGS. 1 and 2, a magnet rotor 8 is fixed to the wheel 9 as a detected body for detecting the rotation state of the wheel 9 of the vehicle as a rotating body. The magnet rotor 8 may be fixed directly to the wheel 9 or may be fixed to a shaft 7 (rotating shaft) that fixes the wheel 9 as shown in FIG. A sensor 10 that is a detection element for detecting rotation of the wheel 9 (rotation of the magnet rotor 8) is attached to a vehicle side that does not rotate with the wheel 9, such as a hub bearing. The sensor 10 is disposed to face the magnet rotor 8 with a predetermined distance A. The sensor 10 is a magnetic detection sensor such as a Hall IC or a Hall IC equipped with a Hall element.

  The sensor 10 outputs an AC detection signal S according to the rotation of the wheel 9 and the magnet rotor 8. As shown in FIG. 2, the magnet rotor 8 is alternately provided with N poles and S poles at a predetermined pitch. When the NS poles pass through the sensor 10, an AC detection signal S is output. The AC frequency of the detection signal S changes depending on the speed at which the magnet rotor 8 passes through the sensor 10. Thereby, the rotation speed (the number of rotations per predetermined time) of the wheel 9 rotating integrally with the magnet rotor 8 can be known. Since the principle of magnetic detection by the sensor 10 is known, a detailed description is omitted.

  By the way, as the vehicle travels, a force in a direction along the shaft 7 in FIG. Here, the force applied from the direction along the shaft 7 (rotation axis) is hereinafter referred to as “lateral force”. Due to this lateral force, the wheel 9 causes rotational blurring as shown by an arrow B in FIG. Due to this rotational vibration, a change occurs in a predetermined interval A between the sensor 10 and the magnet rotor 8 that are arranged to face each other. As a result, the strength of the magnetic field of the sensor 10 or the magnitude of the magnetic flux changes, so that the amplitude (crest value) of the AC component detection signal S output from the sensor 10 changes. Since the detection signal S has such a change in peak value as well as an increase / decrease in the DC component due to a temperature change, the wheel state detection device performs the following signal processing to accurately detect the AC frequency. Do.

  In the present embodiment, as shown in FIG. 3, the wheel state detection device includes a receiving unit 1, a wave height detection unit 2, a periodic signal generation unit (rotation detection signal generation unit) 3, and an output unit 4. Configured. As described above, the receiving unit 1 is a functional unit that receives the AC detection signal S output in accordance with the rotation of the rotating body. The detection signal S output from a sensor such as a rotation sensor is often a high impedance signal. The receiving unit 1 includes a buffer 11 having a high input impedance and a low output impedance. The wave height detection unit 2 is a functional unit that detects the wave height of the detection signal S. The periodic signal generation unit 3 generates a periodic signal (rotation detection signal) F1 having a period corresponding to the period of the detection signal S based on a threshold value (Th) set according to the wave height of the detection signal S. Part. The lateral force detection signal generation unit (additional signal generation unit) 5 is a functional unit that generates a lateral force detection signal (additional signal) F3 indicating the lateral force applied to the rotating body according to the peak value of the detection signal S. is there. The output unit 4 is a functional unit that synthesizes the periodic signal F1 and the lateral force detection signal F3 and outputs the resultant as one output signal F. Details of the periodic signal generation unit 3, the lateral force detection signal generation unit 5, and the output unit 4 will be described later.

  First, the functions of the wave height detector 2 and the periodic signal generator 3 will be described in detail. In the present embodiment, the wheel state detection device is configured by an electronic circuit having a microcomputer or the like as a core. Each functional unit is realized by cooperation of hardware and hardware and software. Hereinafter, in the present embodiment, a case where the detection signal S is digitally converted and digital signal processing is described as an example. FIG. 4 shows an example of a method for converting the detection signal S into the digital count value D, and FIG. 5 shows an example of a method for generating the periodic signal F1. As shown in FIG. 3, in the present embodiment, the pulse height detection unit 2 includes an A / D conversion unit 21, an inversion threshold setting unit 22, a comparator 23, a counter 24, and a register 25. Composed. Then, based on the detected peak value, the periodic signal generator 3 generates the periodic signal F1.

  As described above, the detection signal S is impedance-converted in the receiving unit 1, and at this time, signal amplification processing or the like can be performed at the same time. Therefore, strictly speaking, not the detection signal S received by the receiving unit 1 but the signal output from the receiving unit 1 is digitally converted. Can be considered as a signal. Therefore, hereinafter, the signal output from the receiving unit 1 is also referred to as a detection signal S.

  The A / D conversion unit 21 is a functional unit that digitally converts the detection signal S according to a predetermined condition, and includes an A / D converter. There are various types of A / D converters such as a flash type, a successive approximation type, and an integration type, and an optimal one is appropriately selected according to the conversion speed, conversion accuracy, and the like. Also, the output form of the A / D converter also outputs an absolute value as a digital value with respect to an analog input, or outputs a trigger signal every time the analog input changes by a predetermined amount, etc. There are various forms, which are appropriately selected. In the present embodiment, an absolute value is not output as a digital value, but an example in which an A / D converter that outputs a trigger signal for every predetermined amount of change (predetermined step) is used as an example. explain.

  In this embodiment, this type of A / D converter is used for the following countermeasures. In other words, even when the amplitude center of the detection signal S of the rotation sensor fluctuates, that is, when the offset of the direct current component fluctuates, appropriate signal processing can be performed according to the amplitude (wave height) of the detection signal S. This is because. The offset for the DC component can be eliminated by another signal processing circuit using a coupling capacitor or a DC bias. A person skilled in the art can understand the description of the present embodiment shown below and configure the sensor signal processing apparatus of the present invention using an A / D converter of a type that outputs an absolute value as a digital value. It will be possible. Therefore, this embodiment does not limit the present invention.

  The A / D converter 21 outputs a trigger signal each time the detection signal S changes by a predetermined amount, specifically, every time the detection signal S changes by a predetermined amount toward the peak P side of the oscillating waveform. As the peak value of the oscillating waveform is referred to as “peak to peak”, in this embodiment, “the peak P of the waveform” refers to both the peak side and the valley side of the waveform. And As shown in FIG. 4, a trigger signal is output on the side of the peak P from the predetermined inversion threshold R, and this trigger signal is counted by the counter 24 to become a digital count value D. In FIG. 4, the digital count value D is a step that changes stepwise along the sinusoidal detection signal S and has the values 5, 6, 7. The inversion threshold R will be described later.

When the detection signal S reaches the peak P, the detection signal S does not change toward the peak P by a predetermined amount. Therefore, the digital count value D is in a state in which a constant value continues in the vicinity of the peak P of the detection signal S. In the example shown in FIG. 4, the digital count value D has continued at 25, it has a peak value D _P of the digital count value D. The counter 24 is an up / down counter, and when the detection signal S changes by a predetermined amount in the direction of the peak P and in the opposite direction, different trigger signals are output from the A / D converter 21. For example, a digital count value D corresponding to the waveform of the detection signal S can be obtained. However, in this case, there is a possibility that the detection signal S may follow even when the detection signal S increases or decreases at a position other than the peak P due to noise or the like. Therefore, in the present embodiment, the counter 24 is configured as an up counter. When the detection signal S changes in the reverse direction (changes in the direction opposite to the peak P), the peak is detected when a predetermined change width h corresponding to a plurality of counts of the digital count value D is exceeded. It is configured to be determined to have reversed beyond P. That is, hysteresis is set.

  Specifically, in the present embodiment, the inversion threshold value setting unit 22 sets an inversion threshold value R for determining whether or not the detection signal S is inverted beyond the peak P. Here, the inversion threshold R is set with a change width h corresponding to 5 counts of the digital count value D. The A / D converter 21 transmits the analog value of the detection signal S at the time of outputting the latest trigger signal (or the analog value that is an A / D conversion threshold) to the inversion threshold setting unit 22. The inversion threshold value setting unit 22 sets the inversion threshold value R by adding a predetermined change width h (hysteresis value) to the received analog value. When the detection signal S is rising (when the peak P is on the peak side), the hysteresis value h is subtracted from the analog value, and the inversion threshold R is set. When the detection signal S is decreasing (when the peak P is on the valley side), the hysteresis value h is added to the analog value, and the inversion threshold R is set.

The inversion threshold R is input to the comparator 23 that functions as an inversion determination unit. The comparator 23 compares the detection signal S with the inversion threshold value R and determines whether or not the detection signal S is inverted beyond the peak P. The counter 24 that has received the determination output from the comparator 23 transfers the peak value DP of the digital count value D to the register 25 and stores it, and also presets the digital count value D of itself (counter 24). In the example illustrated in FIG. 2, the counter 24 stores “25” as the peak value D _P of the digital count value D in the register 25 and presets the digital count value D of itself (counter 24) to “5”. The preset value “5” is the number of steps of the digital count value D corresponding to the hysteresis value h.

  After that, the A / D converter 21 that has received the determination output from the comparator 23 outputs a trigger signal when the detection signal S changes by a predetermined amount in a direction opposite to that before receiving the determination output. In response to this trigger signal, the counter 24 increments the digital count value D. Also, the inversion threshold value setting unit 22 that has received the determination output from the comparator 23 switches the calculation method when setting the inversion threshold value R. That is, the inversion threshold value setting unit 22 switches between “subtracting” and “adding” the hysteresis value h to the analog value received from the A / D conversion unit 21.

Periodic signal generating unit 3, the register 25 obtains a peak value D _P of the latest digital count value D to set the threshold Th. In the present embodiment, the threshold value Th is a threshold value for determining a periodic signal. Threshold Th is set by multiplying a predetermined coefficient k with respect to the peak value D _P. The threshold value Th may be set in the register 25 and the periodic signal generation unit 3 may acquire the threshold value Th from the register 25. In any case, the periodic signal generator 3 determines the output timing of the periodic signal F1 based on the threshold value Th and the digital count value D acquired from the counter 24. In the present embodiment, the periodic signal F1 is inverted at each output timing. That is, if the rotating body rotates at a constant speed, the periodic signal F1 is generated as a rectangular wave having a duty of 50%. However, the periodic signal generation unit 3 does not necessarily generate the waveform of the periodic signal F1, and it is sufficient to determine the output timing such as the change point of the pulse waveform. The waveform generation may be performed in the output unit 4.

Hereinafter, description will be made using specific numerical values. Here, a case where a waveform is generated will be described as an example for easy understanding. Peak D _P of the left valley of the detection signal S in FIG. 5 is "23". For example, when the coefficient k is 0.8, the threshold value Th is “18”. Here, the fraction is rounded down for easy explanation. When the digital count value D received from the counter 24 becomes “18”, the periodic signal generator 3 generates the periodic signal F1. The periodic signal F1 changes from the reference value C in the positive direction to the wave height of the signal level PL. Further, the peak value D _P of the peak of the detection signal S in FIG. 5 is “25”. In this case, the threshold value Th is “20”. When the digital count value D received from the counter 24 becomes “20”, the periodic signal generator 3 changes the periodic signal F1. The periodic signal F1 changes from the signal level PL to the reference value C. That is, the periodic signal F1 is inverted every time the digital count value D reaches the threshold value. The periodic signal F1 is generated one by one in one period of the detection signal S. As described above, the periodic signal generation unit 2 is a period corresponding to the period of the detection signal S (proportional to the period) based on the threshold Th set according to the wave height (peak value D _P ) of the detection signal S. A periodic signal F1 having the following is generated.

  Here, a case where a lateral force Y is applied to the wheel 9 will be considered. FIG. 6 shows an example in which a lateral force Y is applied to the wheel 9, rotational vibration occurs in the wheel 9, and the amplitude (peak value) of the detection signal S output from the sensor 10 changes. If the wheel 9 is rotating at a constant speed by the signal processing as described above, the cycle detection signal F1 is output at a constant interval regardless of a change in amplitude (peak value). Here, focusing on the change in the peak value PP (peak-to-peak value PP), as described above with reference to FIG. 1, the peak-to-peak value PP is applied to the wheel 9 by the lateral force Y. Will change. Therefore, the magnitude of the lateral force Y can be known from the peak-to-peak value PP. In this example, the peak value from the top to the bottom is the peak-to-peak value PP. As shown in FIG. 3, the wheel state detection apparatus of the present invention includes a lateral force detection signal generation unit 5 and an output unit 4. The lateral force detection signal generator 5 generates a lateral force detection signal F3 as an internal signal based on the peak-to-peak value PP detected by the wave height detector 2. As will be described later, the information indicated by the lateral force detection signal F3 is output by being superposed on the periodic signal F1 in the output unit 4.

  FIG. 6 illustrates a waveform example of the lateral force detection signal F3 as an internal signal. The magnitude of the lateral force Y, that is, the magnitude of the peak-to-peak value PP is indicated by the pulse height of the pulse waveform. The lateral force detection signal F3 in this example indicates a peak-to-peak value PP based on the peak value from the reference voltage (or reference current) ref. Further, the reference Z in the figure indicates when the lateral force Y is zero. As is apparent from the structure shown in FIG. 1, the length of the predetermined distance A between the magnet rotor 8 and the sensor 10 varies depending on the direction in which the lateral force Y is applied. Therefore, the direction in which the lateral force Y is applied can be detected by defining the point where the lateral force Y is zero. The switching of the peak value of the pulse waveform is preferably synchronized with the change timing of the periodic signal F1, as shown in FIG.

  As described above, it is possible to provide a wheel state detection device that can detect the lateral force Y in addition to the rotational speed by adding a signal processing function unit slightly. Today, in order to grasp the behavior of the vehicle and perform feedback control, various sensors are mounted on the vehicle, and the number thereof is constantly increasing. According to the present invention, it is possible to detect a plurality of events by devising signal processing without adding a sensor element or the like, so that there is no substantial increase in the number of parts and an increase in cost can be suppressed. It is suitable for. Further, the detection of the lateral force Y when the vehicle travels, which is important detection information for the skid prevention device, is preferably performed quickly in response to the occurrence of the event, rather than using a yaw rate sensor or the like mounted on the vehicle body side. It is preferably detected at the wheel 9. According to the present invention, since the lateral force Y is detected at the wheel 9, the detection result of the wheel state detection device is very useful for the skid prevention device.

  However, when the rotational speed detection device is already mounted on the vehicle, it is not preferable to add a signal line in order to obtain the detection result of the lateral force Y because the number of parts increases. Therefore, the information indicated by the lateral force detection signal F3 is combined with the periodic signal F1 to output this output signal F via one signal line as one output signal F. Accordingly, it is possible to easily add a function of detecting the lateral force Y without adding a signal line. Hereinafter, a protocol for transmitting a plurality of physical quantities by superimposing information indicated by the lateral force detection signal F3 on the periodic signal F1 in the output unit 4 will be described.

  As shown in FIG. 7, in the data communication method (communication protocol) of the present embodiment, the value indicating the lateral force Y is not superimposed in each cycle of the periodic signal F1, but is a difference value from the previous cycle. Is output. Specifically, a learning mode and a normal mode are provided, and in the learning mode, for example, the difference value between the initial value that is zero and the lateral force Y is reduced, and in the normal mode, the amount of change in the lateral force Y is used as the difference value. Is output. A flag for distinguishing between the learning mode and the normal mode is not necessary. The ECU that receives the output signal F, for example, determines that the learning mode is in a period during which the value of the lateral force Y is monotonously increasing, and moves with increasing or decreasing, decreasing or increasing, or does not increase or decrease. It is possible to determine that the normal mode has been reached.

  As shown in FIG. 8, in this example, the output signal F is a signal obtained by combining the periodic signal F1 with the superimposed pulse F3a representing the difference value of the lateral force Y. In the present example, the following four types of superimposed pulses F3a are set according to the difference value of the lateral force Y, and the output signal F also takes four types of waveforms, Fa to Fd, accordingly. Here, an example of a waveform in which the superimposed pulse F3a is superimposed as a higher level signal when the periodic signal F1 is at a high level is shown, but the waveform example is not limited to this. When the periodic signal F1 is at a low level, the superimposed pulse F3a may be superimposed as a signal having a lower level.

  The output signal Fa is a case where the superimposed pulse F3a is not superimposed, and this period in the periodic signal F1 (output signal F) indicates a reset state of information indicating the lateral force Y. The output signal Fb is a case where one pulse of the superimposed pulse F3a is superimposed. This period indicates that the lateral force Y is reduced by one unit with respect to the previous period. Here, one unit indicates a predetermined resolution. The output signal Fc is a case where two superimposed pulses F3a are superimposed. As shown in FIG. 8, for example, when the pulse width of the superimposed pulse F3a is 50 μs, two pulses are superimposed with an interval of 50 μs. This period indicates that the lateral force Y does not increase or decrease with respect to the previous period. The output signal Fd is a case where three pulses of the superimposed pulse F3a are superimposed. Similar to the output signal Fc, three pulses are superimposed with an interval of 50 μs. This period indicates that the lateral force Y is increased by one unit with respect to the previous period.

  For example, in FIG. 9, at times t1, t2, and t5, the number of superimposed pulses F3a is 3, and the value F3b of the lateral force Y increases by one. At time t3, the number of superimposed pulses F3a is 1, and the lateral force Y value F3b is decremented by one. At times t4 and t6, the number of superimposed pulses F3a is 2, and the lateral force Y value F3b is maintained.

  The lateral force Y is obtained by calculating the lateral force Y according to the following equation (1) using the number of pulses of the periodic signal F1 (period number) and the number of pulses of the superimposed pulse F3a in a predetermined period. Can do. Here, aj is the number of pulses crossing the reference a in FIG. 9, that is, the number of pulses of the periodic signal F1, and bj is the number of pulses crossing the reference b in FIG. 9, that is, the superimposed pulse F3a indicating the lateral force Y. The number of pulses. The ECU that has received the output signal F may increase or decrease the lateral force Y in each cycle to update the value, or may calculate the lateral force Y by calculating all at the end of a predetermined period. Good.

  Lateral force Y = Σbj−2 · Σaj (1)

  In FIG. 9, the number of pulses crossing the reference a, that is, the number of pulses of the periodic signal F1, is set to aj, and the number of pulses crossing the reference b, that is, the number of superimposed pulses F3a indicating the lateral force Y is set to bj. As shown in Expression (1), a value obtained by subtracting twice the total number of pulses of the periodic signal F1 from the total number of superposed pulses F3a in a predetermined period is the value of the lateral force Y. According to the equation (1), at each time t0 to t6 in FIG. 9, the value of the data value F3b is as follows.

Time t0: 0 (reset)
Time t1: 1 = 3−2 × 1
Time t2: 2 = 6−2 × 2
Time t3: 1 = 7−2 × 3
Time t4: 1 = 9−2 × 4
Time t5: 2 = 12-2−5
Time t6: 2 = 14−2 × 6

  The above formula (1) can also be interpreted as the following formula (2).

    Here, the first term on the right side of Equation (2) represents the value up to the previous period of the rectangular wave. For example, it is considered that the times t1 to t6 in FIG. The first term on the right side of Equation (2) is the value (= 7) of the data value F3b determined at time t5. The second term on the right side of Equation (2) represents the difference (= 2) when time elapses from time t5 to time t6. That is, according to this communication protocol, the ECU that has received the output signal F can also update the value by increasing / decreasing the lateral force Y in each cycle. It can be better understood that the value of force Y can also be determined.

  In each period of the rectangular wave, the data value can be updated by a simple calculation of adding a difference (including a negative value) to the data value up to the previous period, so the calculation load on the ECU receiving the output signal F is reduced. The calculation time is also shortened. It is also possible to suppress the capacity of temporary storage means such as a RAM for temporarily storing data.

  Hereinafter, a specific example of a communication protocol for transmitting different physical quantities using a common signal line will be described with reference to the flowchart of FIG. It mainly corresponds to the function of the periodic signal generation unit 3, the lateral force detection signal generation unit 5, and the output unit 4 described above. However, here, description will be made as an execution example of a program of a microcomputer in which the functional units are not specified, and these functional units are realized. As described above, the periodic signal F1 is inverted at each output timing determined based on the threshold value Th and the digital count value D acquired from the counter 24. The periodic signal F1 is inverted to a low level (Low) in Step # 10. Here, the second physical quantity such as the lateral force Y is acquired as the additional data value X (step # 20).

  Next, it is determined whether or not communication of additional data X is necessary (step # 30). If communication is not required, the communication flag J is set to 0, and the difference coefficient d is reset to 0 (step # 31). If communication is required, the communication flag J is set to 1 (step # 32). When communication is required, the current value is maintained without resetting the difference coefficient d.

  Next, the internal data M of the additional data value X is calculated (step # 40). The internal data M is obtained by adding the product of the difference coefficient d and the resolution to the initial value. When the communication flag J is set to 0, the difference coefficient d is reset to 0, so that the internal data M becomes an initial value. When the communication flag J is set to 1, a value corresponding to the difference coefficient d is calculated.

  Next, in steps # 50 to # 57, the number Q of superimposed pulses F3a is set. In step # 50, the setting state of the communication flag J is determined. If the communication flag J is 0, the pulse number Q of the superimposed pulse F3a is set to 0 in order to transmit that the reset state is set (step S50). # 51). When the communication flag J is 1, the acquired additional data value X and the internal data M are compared, and the pulse number Q of the superimposed pulse F3a is set (steps # 52 to # 57). When the additional data value X is smaller than the internal data M (step # 52), the pulse number Q of the superimposed pulse F3a is set to 1 (step # 53) in order to transmit the decrease in the additional data value X. . When the additional data value X is the same as the internal data M (step # 54), in order to transmit the maintenance of the additional data value X, the pulse number Q of the superimposed pulse F3a is set to 2 (step # 55). When the additional data value X is larger than the internal data M (step # 56), the number Q of superposed pulses F3a is set to 3 in order to transmit the increase in the additional data value X (step # 57). .

  When the pulse number Q of the superimposed pulse F3a is set, the difference coefficient d is calculated and updated according to the pulse number Q (step # 60). In the present embodiment, the maximum number of pulses Q of the superimposed pulse F3a is 3, and as described above, the difference from minus 1 to plus 1 is indicated. Therefore, the value obtained by subtracting 2 from the number Q of pulses is the value of the periodic signal F1. This is the difference in the period. The difference coefficient d is a value indicating the accumulation of differences after the communication plug J becomes 1.

  As described above, the periodic signal F1 is inverted at each output timing determined based on the threshold value Th and the digital count value D acquired from the counter 24. The periodic signal F1 is inverted to a high level (High) in Step # 70. Here, as shown below, a superimposed pulse F3a is generated as necessary, and is superimposed on the periodic signal F1 and output as the output signal F (steps # 80 to # 82). First, it is determined whether or not the pulse number Q is 0 (step # 80). If it is 0, the superimposed pulse F3a is not generated, and the periodic signal F1 is output as the output signal F. That is, the output signal F having a waveform like Fa shown in FIG. 8 is output. If the number of pulses Q is not 0, one superimposed pulse F3a is generated (step # 81). For example, as shown in FIG. 8, a superimposed pulse Fa3 that lasts for 50 μs is generated and superimposed on the periodic signal F1.

  When one superimposed pulse F3a is generated, the value of the number of pulses Q is decremented by 1 (step # 82). Then, it is again determined whether or not the pulse number Q is 0 (step # 80). Here, if the pulse number Q is 0, the periodic signal F1 is output as the output signal F in the period thereafter. That is, an output signal F having a waveform like Fb shown in FIG. 8 is output. If the pulse number Q is 1 or 2, one more superimposed pulse F3a is generated (step # 81). The period from the completion of the previous step # 81 to the start of the execution of step # 81 again through step # 82 and step # 80 is 50 μs in this example, and is preferably managed by a timer or the like. It is. As a result, as shown in FIG. 8, a superimposed pulse F3a that lasts for 50 μs and continues again for 50 μs after 50 μs is generated and superimposed on the periodic signal F1.

  When one more superimposed pulse F3a is generated, the value of the number of pulses Q is similarly reduced by one (step # 82). Then, it is again determined whether or not the pulse number Q is 0 (step # 80). Here, if the pulse number Q is 0, the periodic signal F1 is output as the output signal F in the period thereafter. That is, an output signal F having a waveform like Fc shown in FIG. 8 is output. Here, if the number of pulses Q is not yet 0, as described above, one more superimposed pulse F3a is generated (step # 81). Next, by the generation of the superimposed pulse F3a, the value of the pulse number Q is similarly reduced by one (step # 82). Then, it is again determined whether or not the pulse number Q is 0 (step # 80). If it is 0, the periodic signal F1 is output as the output signal F in the period thereafter. That is, the output signal F having a waveform like Fd shown in FIG. 8 is output.

  In this example, the case where the superimposition pulse F3a is a maximum of three pulses has been described as an example, but any number that can be superimposed can be set according to the minimum value of the period T of the periodic signal F1. In this example, the case where both the pulse width and the pulse interval of the superimposed pulse F3a are set to 50 μs has been described as an example, but this can also be set as appropriate according to the minimum value of the period T of the periodic signal F1. Hereinafter, the calculation formula of the internal data M when the maximum number of superimposed pulses F3a in one cycle of the periodic signal F1 is 1, 2, 5, N (any odd number of 3 or more) is shown. This corresponds to the above-described formula (1), and the formula when the maximum number of pulses is 3 is also shown again for reference. When the maximum number of pulses is 1, the reset state cannot be indicated.

Maximum number of pulses 1: M = 2 · Σbj−Σaj
Maximum number of pulses 2: M = 2 · Σbj−3 · Σaj
Maximum number of pulses 3: M = Σbj−2 · Σaj
Maximum number of pulses 5: M = Σbj−3 · Σaj
Maximum number of pulses N: M = Σbj − {(N + 1) / 2} · Σaj

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described. The description of the same points as in the first embodiment is omitted as appropriate, and the points corresponding to the first embodiment are indicated by the same reference numerals in the drawings. The first embodiment has been described using an example in which a narrow superimposed pulse having a wave height higher than the wave height of the rectangular wave is superimposed at a high level predetermined position in one cycle of the rectangular wave. However, the form of the superimposed pulse is not limited to this, and it is possible to adopt a form as shown in FIG. FIG. 11 corresponds to FIG. 8 of the first embodiment.

  As shown in FIG. 11, also in the second embodiment, the output signal F is a signal obtained by combining the periodic signal F1 with the superimposed pulse F3a. The following four types of superposition pulses F3a are set according to the difference value, and the output signal F also takes four types of waveforms Fa to Fd accordingly. In the second embodiment, when the periodic signal F1 is at a low level, the superimposed pulse F3a is superimposed as a signal having the same level as the wave height of the periodic signal F1 without being spaced from the periodic signal F1. That is, as a result, the pulse width W of the periodic signal F1 is extended by the superposition of the superposition pulse F3a. The apparent pulse width of the extended periodic signal F1 is assumed to be W1.

  The output signal Fa is a case where the superimposed pulse F3a is not superimposed, and the period in which this waveform is output in the periodic signal F1 (output signal F) indicates a reset state of information indicating the lateral force Y. The output signal Fb is a case where one pulse of the superimposed pulse F3a is superimposed. In this example, the pulse width of one pulse of the superimposed pulse F3a is the same as the pulse width of the periodic signal F1. As shown in FIG. 11, when the pulse width W of the periodic signal F1 is 50 μs, the pulse width W of the superimposed pulse F3a is also 50 μs, and the apparent pulse width W1 of the periodic signal F1 is 2 W (= 100 μs). Similar to the first embodiment, this period of the periodic signal F1 indicates that the lateral force Y is reduced by one unit with respect to the previous period.

  The output signal Fc is a case where two superimposed pulses F3a are superimposed. As shown in FIG. 11, since two 50 μs superimposed pulses F3a are superimposed on the periodic signal F1 without any interval, the apparent pulse width W1 of the periodic signal F1 is 3 W (= 150 μs). . Similar to the first embodiment, this period indicates that the lateral force Y does not increase or decrease with respect to the previous period. The output signal Fd is a case where three pulses of the superimposed pulse F3a are superimposed. The apparent pulse width W1 of the periodic signal F1 is 4 W (= 200 μs). Similar to the first embodiment, this period indicates that the lateral force Y is increased by one unit with respect to the previous period.

When employing the configuration as in the second embodiment, the periodic signal F1 is generated in the form as shown in FIG. FIG. 12 is a diagram corresponding to FIG. 5, and a description of the same points as in the first embodiment is omitted. Peak D _P of the left valley of the detection signal S is "23". When the coefficient k is 0.8, the threshold value Th obtained by rounding down the decimal part is “18”. When the digital count value D received from the counter 24 becomes “18”, the periodic signal generator 3 generates the periodic signal F1. The periodic signal F1 is generated as a pulse having a wave height of the signal level PL and a pulse width of the width W in the positive direction from the reference value C. The pulse width W is sufficiently narrower than the period T of the detection signal S. Here, as described above, the pulse width W is 50 μs. Later, based on a threshold Th that is set by a valley peak value D _P, the detection signal S is in is changed from the valley side to the mountain side, the pulse of the periodic signal F1 is generated.

Incidentally, mountain peak D _P, based on a threshold Th that is set by both the peak value D _P of the valley, the valley periodic signal S from the mountain, in both are changing from the valley to the mountain, pulse May be generated. In this case, the pulse interval of the periodic signal F1 is a half period (= T / 2) of the detection signal S. In any case, the periodic signal generator 2 is a period corresponding to the period of the detection signal S (proportional to the period) based on the threshold Th set according to the wave height (peak value D _P ) of the detection signal S. A periodic signal F1 having the following is generated.

  As described above with reference to FIG. 11, in the second embodiment, when the periodic signal F1 is at a low level, the superimposed pulse F3a having the same level as the wave height of the periodic signal F1 is generated without leaving an interval from the periodic signal F1. Superimposed. Therefore, as shown in FIG. 12, the interval between the rising edges of the periodic signal F1 indicates a period corresponding to the period of the detection signal S regardless of the number of pulses on which the overlapping pulse F3a is superimposed.

  FIG. 13 corresponds to FIG. 7 of the first embodiment. As in the first embodiment, as shown in FIG. 13, the value itself indicating the lateral force Y is not superimposed in each cycle of the periodic signal F1, but the value of the difference from the previous cycle is output. The learning mode and the normal mode are provided, and the difference value between the initial value and the lateral force Y that is, for example, zero in the learning mode is reduced, and the change amount of the lateral force Y is output as the difference value in the normal mode.

  In the first embodiment, as shown in FIG. 9, the value of the lateral force Y and the difference value are obtained based on the number of pulses aj in the reference a and the number of pulses bj in the reference b. Also in the second embodiment, the value of the lateral force Y and the difference value can be similarly obtained. In the second embodiment, the apparent pulse width W1 of the periodic signal F1 may be used as bj instead of the number of pulses in the reference b. Specifically, by setting “bj = (W1 / W) −1”, it is possible to calculate the number of superimposed pulses F3b.

[Other Embodiments]
The periodic signal F1 is not limited to a signal indicating a rotation state, and may be another signal as long as the period indicates a physical quantity (first physical quantity). In addition, other signals may be used as long as they are periodic signals (the period may vary). Further, the second physical quantity is not limited to the lateral force Y, and may be another physical quantity. For example, it may be the temperature or the air pressure of the wheel. Further, in the present embodiment, the case where the first physical quantity and the second physical quantity are acquired based on the detection result detected by one magnetic sensor 10 is illustrated, but the present invention is not limited to such a configuration. Absent. In the block diagram shown in FIG. 3, detection results from different sensors can be shared by adopting a configuration in which detection results from other sensors are input to the lateral force detection signal generation unit 5 that functions as an additional signal generation unit. It is possible to transmit with a signal line. In the above example, the case where the value indicating the second physical quantity increases in the learning mode is exemplified, but the present invention is not limited to this. The initial value may be a high value and may be a physical quantity whose value decreases in the learning mode.

  As described above, according to the present invention, it is possible to provide a data communication method for transmitting different physical quantities through a common signal line. This data communication method can be applied to a wheel state detection device that transmits other physical quantities together with a physical quantity indicating the state of the wheels.

F1: Periodic signal (rectangular wave, rotation detection signal)
F3a: Superposition pulse (additional signal)
3: Periodic signal generator (rotation detection signal generator)
4: Output unit 5: Lateral force detection signal generation unit (additional signal generation unit)
9: Wheel

Claims (6)

The first physical quantity is transmitted at least by the period of the rectangular wave, and the first physical quantity differs from the first physical quantity by a superposition pulse superimposed at a predetermined position of either the high level or the low level in one period of the rectangular wave. A data communication method for transmitting two physical quantities,
A data communication method for transmitting the second physical quantity by representing an increase / decrease in the second physical quantity transmitted up to the previous period according to the number of the superimposed pulses in each period.   2. The data communication method according to claim 1, wherein two or more superimposing pulses can be superposed in each cycle, and indicate an increase / decrease number including zero according to the number of pulses.   The data communication method according to claim 1 or 2, wherein the value of the second physical quantity is indicated based on the number of periods of the rectangular wave in a predetermined period and the number of pulses of the superimposed pulse.   The data communication method according to claim 1, wherein the first physical quantity is a physical quantity indicating a rotation state of a wheel.   The data communication method according to any one of claims 1 to 4, wherein the second physical quantity is a physical quantity indicating a lateral force applied to the wheel from a direction along a rotation axis direction of the wheel. A rotation detection signal for generating a rotation detection signal of a rectangular wave having a period corresponding to the period of the detection signal as a signal for transmitting the first physical quantity based on an AC detection signal output according to the rotation of the wheel. A generator,
A second physical quantity different from the first physical quantity can be superimposed in each period of the rotation detection signal, representing an increase or decrease with respect to a value transmitted up to the previous period depending on the number of pulses superimposed in each period. An additional signal generation unit for generating an additional signal to be transmitted;
An output unit that superimposes the additional signal at a predetermined position of either the high level or the low level in one cycle of the rotation detection signal;
A wheel state detection device comprising:

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