JPS60116326A - Heart rate meter for vehicle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to an on-vehicle heart rate monitor that measures the heartbeat of a driver, etc. on a vehicle, and particularly relates to a vehicle equipped with a sensor on the steering wheel that outputs an electrical signal according to the human heartbeat. Regarding heart rate monitors.

[Prior Art] When driving a vehicle, if the driver's health condition is not favorable, there is a high possibility that an accident will occur.

For example, if you continue to drive for a long time without taking a break, fatigue accumulates, your health condition worsens, and your ability to concentrate decreases.

Heart rate is one barometer that can tell us about a person's health condition. Recently, small portable heart rate monitors have been sold as devices for measuring heart rate.

Although this type of heart rate monitor can be carried anywhere, its measurement accuracy is low. Furthermore, even if a driver who drives a car were to bring such a heart rate monitor into the vehicle in order to learn about his or her health condition, the heart rate measurement would have to be carried out with the vehicle stopped. .

In other words, in this type of general heart rate monitor, a light emitting diode, a photodiode, etc. are protruded from a substrate to form a reflective photosensor, and this sensor is applied to the pad of a person's finger to further reduce the influence of external light. In order to eliminate this problem, the sensor and fingers are covered with black sponge, etc., so the driver cannot drive with this covered on his fingers. In addition, with this type of sensor, if the finger is moved during measurement, the position of the sensor and finger will shift and measurement will not be possible, so the person being measured is required to rest.

Therefore, the present applicant has developed an on-vehicle heart rate monitor (patent application No. 57-1980) that is capable of measuring heart rate even while driving the vehicle by equipping the steering wheel with a sensor for detecting heart rate.
132847).

However, even in this case, in order to measure heart rate,
Since heart rate signals cannot be obtained unless you press your fingertips against the sensor on the steering wheel and maintain that position, it feels strange when measuring while driving, and when you try to drive normally, your fingertips float off the sensor. measurement is interrupted.

[Objective] An object of the present invention is to provide an on-vehicle heart rate monitor that can automatically measure the heartbeat even when the driver is driving naturally.

[Since the area of the constituent fingers is small, if you drive the vehicle while pressing them against a predetermined position on the steering wheel, your hands will be fixed in an unnatural position, creating a feeling of discomfort. However, if the heartbeat can be detected in the palm of the hand, since the palm has a large surface area, there will be room to move the hand relative to the sensor position, and the heartbeat can be measured while continuing to drive the vehicle in a natural manner. However, in the palm of the hand, blood vessels are not concentrated in relatively shallow areas like the fingertips,
3- The palm of the hand tends to float above the steering wheel, so conventional detectors cannot detect the heartbeat signal frequency from the palm. Therefore, in the present invention, a plurality of light-receiving elements are arranged around a light-emitting element so as to surround it, and a detection unit configured such that the optical axes of the light-emitting element and the light-receiving element are directed in substantially the same direction is attached to a steering wheel. Provide at least one on the top. According to this, the heartbeat signal can be extracted from the palm of the hand, and the heartbeat can be measured in a natural manner even while driving.

While driving a vehicle, there are times when it is desired to change the positional relationship between the steering wheel and the hands, such as when changing the direction of travel. Furthermore, the position where each driver grips the steering wheel varies. Therefore, in one preferred embodiment of the present invention, a plurality of detection units are arranged on the steering wheel at predetermined intervals so that the heartbeat signal can be detected no matter where the driver grips the steering wheel.

Hereinafter, a detailed explanation of the present invention will be given with reference to the drawings. Ru.

FIG. 1 shows the vicinity of the driver's seat of a vehicle equipped with an on-vehicle heart rate monitor according to an embodiment. Referring to FIG. 1, in the center of the steering wheel 4 there is a start switch SWI for instructing the start of heart rate measurement, a cancel switch SW2 for instructing cancellation of the measurement. It is also equipped with a light emitting diode LED that displays information according to the heart rate. Two cathode ray tube displays [CRT1 and CRT2] are provided on the left side of the steering wheel 4.

Details of the steering wheel 4 are shown in FIG. 2a.

Shown in Figures 2b and 2c. Referring to these drawings, the upper surface of the steering wheel 4 includes reflective optical sensors SEI, SF2. ...SF3 are arranged dispersedly from each other. Each optical sensor consists of one light emitting diode (LEI) and four phototransistors (PT1 to PT4) arranged around it. The light emitting diode provided in each optical sensor is an infrared light emitting diode that emits light in the infrared region. One light emitting diode and four phototransistors of each optical sensor are
The optical axes are directed in the same direction (above the steering wheel 4). The steering wheel 4 is made up of an iron core 4b and a resin 4a covering it, and each optical sensor is connected to the resin 4a.
It is fixed to the part. Electric wires drawn out from each optical sensor pass through the inside of the resin mesh 4a and are connected to an electronic circuit in a panel at the center of the steering wheel 4.

Figure 3a shows an on-vehicle heartbeat n mounted on the vehicle shown in Figure 1.
1 shows an outline of the circuit configuration of No. 1. This will be explained with reference to Figure 3a. Microcomputer CP controls the entire circuit
It is U. The microcomputer CPU includes an oscillation circuit 08C2, a voice synthesizer VGU, and a video memory VRAM.
I, VRAM2゜Buzzer BZ, A/D converter ADC
, key switches SWI, SW2, etc. are connected. The circuit provided between the key switches SWI and SW2 and the CPU is a waveform shaping circuit. A speaker SP is connected to the output terminal of the voice synthesizer VGU, and a speaker SP is connected to the output terminal of the voice synthesizer VGU.
AM1 and VRAM2 have a cathode ray tube display device CRT.
I and CRT2 are connected to each other. Variable resistors VRI and VR2 for setting a reference level are connected to input terminals 1 and 2 of the A/D converter ADC, respectively, and an output terminal of a demodulation circuit DEM is connected to an input terminal 3. The output terminal of the demodulation circuit DEM is connected to a light emitting diode LED for display via a driver DV. The output terminal of the oscillation circuit osct is connected to the sensor unit SEU, and the output terminal of the sensor unit SEU is connected to the input terminal of the demodulation circuit DEM.

Oscillation circuit O8CI in Figure 3a, sensor unit SEU
, and the details of the demodulation circuit DEM are shown in FIG. 3b. This will be explained with reference to FIG. 3b. The oscillation circuit 08C1 is an unstable multivibrator circuit, and in this example, IKI (
Outputs a square wave signal of z.

The sensor unit SEU includes eight optical sensors SE1 to S
It is E8. The light emitting diodes LEI, LE2, . . . of the optical sensors SEI to SE8 are connected in series, and one end thereof is connected to the output terminal of the oscillator 7-path 08CI.

Therefore, the light emitting diode of each optical sensor is 1m5
Lights up intermittently at a cycle of ec. Optical sensor SEI~S
When any of E8 is positioned opposite to a human blood vessel, the light reflectance of that portion varies depending on the blood flow rate, that is, the heartbeat. Therefore, an IKHz alternating current signal whose amplitude is modulated according to the heartbeat signal is obtained at the output terminal of the phototransistor of the optical sensor.

Phototransistor PT of each optical sensor SEI to SE8
I, PT2. PT3... are connected in parallel with each other, and one end thereof is connected to the input terminal of the demodulation circuit OEM. The demodulation circuit DEM is.

Amplifier AM 1 , low pass filter LPI, amplifier A
M2. Low pass filter LP2. It consists of an amplifier AM3 and the like, and demodulates the original heartbeat signal from the amplitude modulated IKHz signal.

FIG. 4 shows the configuration of the video memory VRAM1 of FIG. 3a. Note that the video memory VRAM2 also has the same configuration as the VRAM1. This will be explained with reference to FIG. 4. The memory RAM stores bright/dark data corresponding to each pixel displayed on the cathode ray tube. The address line of the memory RAM is connected to a multiplexer MX, and a memory address is selected according to either the count value of the address counter CO applied to inputs A and H of MX or the output address of the CPU.

This selection is made by the microcomputer CPU when writing data to the memory RAM or when writing data to the RA, M
When reading data from MX, input B of MX is designated, and the CPU designates the address.

At other times, the address of the memory RAM is specified by the count value of the address counter CO.

The address counter CO constantly performs counting using a pulse signal corresponding to the number of pixels from the oscillator 08C3. Further, a synchronization signal generation circuit 100 is connected to the output terminal of the address counter CO, and this circuit is connected to the output terminal of the address counter CO.
A vertical synchronization signal and a horizontal synchronization signal are generated at predetermined timing according to the count value of .

A shift register SR is connected to a data line consisting of a plurality of bits of the memory RAM, and a serial output terminal of the SR is connected to a signal synthesis circuit 110. Also, this data line is connected to CP via bidirectional buffer BF2.
The U data line is connected.

When displaying a predetermined pixel on a cathode ray tube brightly, set a predetermined bit to ``1'' in the RAM address corresponding to that pixel.
Write the data from the CPU. In this case, specify the B input of multiplexer MX and bidirectional buffer BF2.
Specify the CPU side as input and the RAM side as output, and
Predetermined data is set in the address line and data line of the memory RAM, and a write designation signal is applied to the memory RAM. After this is finished, until the next write is performed,
Specify MX as input A, and write RAM of bidirectional buffer BF2.
side is set to high impedance.

In this state, a synchronization signal is generated at every predetermined timing, and RAM addresses are sequentially selected in accordance with the synchronization signal. When a predetermined address is specified by writing display data, multiple bits of data including pixel data are set in the shift register SR, and with a delay of a predetermined clock corresponding to the pixel position, the "bright" state of the predetermined pixel is indicated. Data is applied to signal synthesis circuit 110. In this way, a serial digital camera corresponding to the data of all pixels on the display screen is continuously output, and this image data and the synchronization signal are combined at 110 to form a composite signal, which is used in a cathode ray tube display device (monitor). television).

FIG. 5 shows a schematic operation of the microcomputer CPU shown in FIG. 3a. The operation will be explained with reference to FIG.

First, interrupt processing will be explained. Since the signal from the oscillation circuit 08C2 is applied to the interrupt input terminal INT of the CPU, the CPU executes interrupt processing at predetermined intervals.

In this interrupt processing, the contents of register N are incremented by one.

In other words, the contents of register N change depending on the elapsed time, so if you clear the contents of N to 011- at a certain timing, you can check the value of N in the main routine and check the progress since clearing. I can tell the time. In the main routine, subroutine, etc., various processing timings are determined by checking the value of this register N.

Next, the main routine will be explained. When the power is turned on,
First, check the start switch SW1. When this is turned on, the voltage set by the variable resistors VRI and VR2 is converted into a digital signal by the A/D converter ADC, and the converted data is stored in the registers MH and ML. The data in registers MH and ML are as follows:
This is the upper limit value of heart rate variation and the lower limit value of heart rate for determining whether or not to issue an alarm.

Table 1 below outlines the relationship between the general average value of heart rate 1/L and the variation (i.e. variance) ΔL of the heartbeat cycle and a person's physical and mental state.

12-Table 1 Generally, when driving a vehicle, the driver is physically relaxed and mentally tense.

However, when the driver falls asleep while driving due to fatigue or the like, the mental tension disappears and the heart rate returns to the state during sleep. In other words, referring to Table 1, when a person begins to fall asleep while driving a vehicle, the variation in heartbeat cycles increases rapidly.

Therefore, in this example, the heartbeat cycle variation reference value (
An upper limit value) Ml and a heart rate reference value (lower limit value) MH are set so that an alarm is issued when the variation is large and the heart rate is below a predetermined value.

M) Once I and ML settings are completed, heart rate measurement is started after waiting for the elapse of a predetermined time To required for the detection signal to become stable. The heart rate measurement subroutine will be explained in detail later. After the heartbeat measurement is completed, the variance of the heartbeat cycle, that is, the variation ΔL, is calculated based on the result. This calculation is performed using a calculation formula where S is the heartbeat cycle of a predetermined sample (16 in this example).

Variance = Average value of 82 - (Mean value of S) 2 Next, the heart rate, that is, the heart rate converted per minute, is calculated from the average value of S. Depending on this result, R in the CPU is set in advance.
Read out the predetermined numerical display data stored in the OM (read-only memory) and transfer it to the video memory VRA.
Set to a predetermined address of M2. As a result, the numerical value of the heart rate is displayed on the cathode ray tube display CRT2, for example, as shown in FIG. 3a.

Next, the A/D converter ADC samples the heartbeat signal at predetermined intervals for a predetermined time, and displays the sampled data as a waveform on the cathode ray tube display device CRTI. Note that before performing this display, the memory RAM is cleared in advance. In the display processing, the following processing is performed.

As shown in Figure 6, pixels on the display screen are
A predetermined plotting subroutine (not shown) is executed to set a predetermined bit at a predetermined address in the memory RAM to rr 1 n.

Specify the voltage Ov to a predetermined Y position 41 (for example, 10),
Change the designated X coordinate according to the value of sampled data. For example, when increasing the X coordinate by 10 for every 0.1V of voltage, if the sampled voltage is 1.5V, the specified X coordinate will be 25 (10+15). The X coordinate has an initial value of 0 and is changed by +1 each time sampling is performed.

That is, when this process is performed, pixels at the X coordinate corresponding to the voltage are sequentially displayed brightly from the left side of the screen to the right side. This process is performed until the X coordinate reaches the right end, that is, X=XM. As a result, a heartbeat waveform as shown in FIG. 6 is displayed on the display CRTI.

Check whether the cancel switch SW2 is on or not.
5 = Yes, if this is off, perform the next process. Dispersion ΔL
is larger than the contents of register MH, and the heart rate is 1/
If L is smaller than the contents of register ML, there is a high possibility that the driver is drowsy, so buzzer B2 is energized for one second and the voice synthesizer is activated! Give an instruction to the VGU and output a voice message saying, "Take a break from the speaker SP." If the above two conditions are not met, only the heart rate and heartbeat waveform are displayed.

Next, the heart rate measurement subroutine will be explained. Note that this subroutine uses a plurality of registers R20 and the like specified by the contents of registers A, R1, and 0.

First, clear the memory (register) and AD
Sample every 2m5ec with C. Check whether an R wave has arrived, and if it is an R wave, then check whether it is the peak of the signal.

The R wave is a large peak in the heartbeat signal, and in this example, the differential value, that is, the change in data for each sampling, is checked to see if it is larger than a predetermined value. It is determined that it is an R wave only when Furthermore, in this example, a peak is determined when the change in the sampling value is 0 or less twice in a row.

When a peak is detected, set the contents of counter N (timer) to 0.
, and measure the time (L) from peak detection to the next peak detection. This time is the so-called RR interval (heartbeat cycle). Each time a measurement is performed, the contents of register A are counted up, and each measurement result is stored in register R2.
Store in (A).

When data for 16 waves is obtained (when A=16)
, end the measurement. The 16 registers of register R2(A) now store period data for 16 periods.

Therefore, from the contents of this register, the variance value and heart rate data can be obtained by performing the above processing.

In the above embodiment, two cathode ray tube display devices are used to display the heartbeat waveform on one and the heart rate on the other. You can set up more than one and use them instead,
The waveform and heart rate may be displayed in a superimposed manner on a surface display for displaying the heartbeat waveform, or the waveform and heart rate may be switched and displayed according to an instruction using a switch or at a predetermined cycle.

In the above embodiment, the light emitting element and the light receiving element are mounted directly on the wheel of the steering wheel. It may also be configured to guide light. Using optical fibers, you can connect multiple optical fibers to the light emitting surface of one light emitting diode, or connect multiple optical fibers to the light receiving surface of one phototransistor, increasing the number of light emitting elements and light receiving elements. It can be reduced. Note that since it is difficult to bend the optical fiber at right angles in a narrow section, it is necessary to use a mirror or the like to direct the optical axis above the steering wheel as in the embodiment.

[Effects] As described above, according to the present invention, the detection unit is located on the steering wheel and the heartbeat signal can be detected in the palm of a person's hand, so the heartbeat can be measured in a natural state even while driving.

[Brief explanation of drawings]

FIG. 1 is a front view showing the vicinity of a driver's seat of a vehicle equipped with an on-vehicle heart rate monitor according to an embodiment. Fig. 2a is an enlarged plan view showing the steering wheel 4 of the vehicle shown in Fig. 1, Fig. 2b is a sectional view taken along the line IIb-IIb in Fig. 2a, and Fig. 2C is a sectional view taken along the line IIc-IIC in Fig. 2a. be. FIG. 3a is a block diagram showing a schematic configuration of the on-vehicle heart rate monitor mounted on the vehicle of FIG. 1, and FIG. 3b is an electric circuit diagram showing the main parts of FIG. 3a. FIG. 4 is a block diagram showing the configuration of the video memory VRAM1 of FIG. 3a. FIG. 5 is a flowchart showing the general operation of the microcomputer CPU shown in FIG. FIG. 6 is a plan view showing the screen display on the display device CRTI. 19-4 steering wheel SEI, SE2. ..., SBR: optical sensor (heartbeat detection means) SEU: sensor unit LEI, LE2. LE3...: Light emitting diode (light emitting means) PTI, PT2. PT3...: Phototransistor (light receiving means) SWI start switch SW2: Cancellation switch osct: Oscillation circuit (light emission means) VGU: Voice synthesizer (notification means) CRTI, CRT2 CRT display device DEM: Demodulation circuit CPU : Microcomputer (electronic control means) 20- Fig. 1

Claims (3)

[Claims] (1) A light emitting means, and a plurality of light receiving means disposed near the light emitting means in positions surrounding the light emitting means with optical axes oriented in substantially the same direction as the light emitting means, and at least one light receiving means disposed on the steering wheel. a set of heart rate detection means; a light emitting energizing means for energizing the light emitting means; a switch means for instructing the start of heart rate measurement; a notification means for performing at least one of display and sound output; An on-vehicle heart rate monitor comprising: electronic control means for calculating a value according to the number of fluctuations per predetermined time or period of fluctuation of an electrical signal from the means, and energizing the notification means according to the result. (2) The on-vehicle heart rate monitor according to claim 1, wherein there is a plurality of heart rate detecting means, each of which is arranged at a predetermined distance from each other with its optical axis directed above the steering wheel. (3) Jl! The on-vehicle heart rate monitor according to claim 1, wherein the pre-energizing means intermittently energizes the light emitting means at a predetermined period.