Smoke detector

• US 8,941,505 B2
• Filed: 10/09/2009
• Issued: 01/27/2015
• Est. Priority Date: 10/09/2008
• Status: Active Grant

• Current Assignee: Hochiki Corporation
• Original Assignee: Hochiki Corporation
• Inventors: Dohi, Manabu
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Labbees, Edny
• Application Number:
  US13/122,940
• Publication Number:
  US 20110194111A1
• Time in Patent Office: 1,936 Days
• Field of Search: 340/628, 340/630, 340/577, 340/578, 250/573, 250/574, 250/575
• US Class Current: 340/630
• CPC Class Codes: G01N 21/53 within a flowing fluid, e.g. smoke
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/113 Constructional details
• CPC Class Codes: G08B 29/18 Prevention or correction of operating errors G08B29/02, G08B29/12 take precedence

Abstract

This smoke detector is provided with: a plurality of light emitting devices which emit light beams of mutually different wavelengths; and a plurality of scattered light receiving sections which receive, at a different scattering angle for each light beam of the respective wavelengths, scattered light generated due to the plurality of light beams emitted simultaneously from these light emitting devices impinging on smoke.

Claims

1. A smoke detector comprising:

a plurality of light emitting devices which emit light beams of mutually different wavelengths; and

a plurality of scattered light receiving sections which receive, at a different scattering angle for each light beam of the respective wavelength, scattered light generated due to the plurality of light beams emitted simultaneously from these light emitting devices impinging on smoke,

wherein a light emission driving under a first driving condition which makes the plurality of the light emitting devices simultaneously emit light with a light emission current of the same current value, and a light emission driving under a second driving condition which changes a light emission current of at least one of the plurality of the light emitting devices so that the light emission current is different from that of the other light emitting device, are performed at a different timing.

2. The smoke detector according to claim 1, wherein

the presence or absence, or type of the smoke is determined based on a correlation between respective light reception signals from each of the scattered light receiving sections.

3. The smoke detector according to claim 1, wherein

the presence or absence, or type of the smoke are determined based on a correlation between light reception signals of each of the scattered light receiving sections under the first driving condition, and a correlation between light reception signals of each of the scattered light receiving sections under the second driving condition.

4. A smoke detector comprising:

a first scattered light detection section in which a long wavelength light emitting device which emits a first light beam having a predetermined long wavelength, and a long wavelength light receiving device which receives first scattered light generated due to the first light beam emitted from this long wavelength light emitting device impinging on smoke, are arranged with a first scattering angle;

a second scattered light detection section in which a short wavelength light emitting device which emits a second light beam having a predetermined short wavelength, and a short wavelength light receiving device which receives second scattered light generated due to the second light beam emitted from this short wavelength light emitting device impinging on smoke, are arranged with a second scattering angle, which differs from the first scattering angle;

a light emission control section which makes the long wavelength light emitting device and the short wavelength light emitting device simultaneously perform light emission;

a first detection processing section which obtains a first long wavelength light reception signal from the long wavelength light receiving device, and a first short wavelength light reception signal from the short wavelength light receiving device; and

a second detection processing section which obtains a second long wavelength light reception signal from the long wavelength light receiving device, and a second short wavelength light reception signal from the short wavelength light receiving device,

wherein the light emission control section is provided with a driving current variable control section which changes a driving current of either one of the long wavelength light emitting device and the short wavelength light emitting device so that a driving current of the long wavelength light emitting device and a driving current of the short wavelength light emitting device are different.

5. The smoke detector according to claim 4, further comprising a smoke type determination section which determines the type of the smoke based on the first long wavelength light reception signal, the second long wavelength light reception signal, the first short wavelength light reception signal, and the second short wavelength light reception signal.

6. The smoke detector according to claim 5, wherein:

the light emission control section drives the long wavelength light emitting device and the short wavelength light emitting device to simultaneously perform light emission with the same light emission current;

the first detection processing section obtains the first long wavelength light reception signal from the long wavelength light receiving device and the first short wavelength light reception signal from the short wavelength light receiving device;

the light emission control section changes the light emission current of either one of the long wavelength light emitting device and the short wavelength light emitting device, and then makes them emit light simultaneously;

the second detection processing section obtains the second long wavelength light reception signal from the long wavelength light receiving device and the second short wavelength light reception signal from the short wavelength light receiving device; and

the smoke type determination section determines the diameter of particles of the smoke as being greater than a predetermined value if the proportion of a long wavelength light reception signal is relatively higher, or, it determines the diameter of the particles of the smoke as being smaller than the predetermined value if a proportion of a short wavelength light reception signal is relatively higher, based on the first long wavelength light reception signal, the second long wavelength light reception signal, the first short wavelength light reception signal, and the second short wavelength light reception signal.

7. The smoke detector according to either one of claim 6, further comprising a detector main body having a flat exposed surface, wherein:

the long wavelength light emitting device, the long wavelength light receiving device, the short wavelength light emitting device, and the short wavelength light receiving device are respectively embedded in the exposed surface;

the first light beam emitted from the long wavelength light emitting device and the second light beam emitted from the short wavelength light emitting device are irradiated into an external smoke detection space which the exposed surface faces, to thereby generate the first scattered light and the second scattered light generated due to these light beams impinging on the smoke within the external smoke detection space; and

the first scattered light is received by the long wavelength light receiving device while the second scattered light is received by the short wavelength light receiving device.

8. The smoke detector according to claim 5, wherein:

the light emission control section makes a light emission current to be flowed to the short wavelength light emitting device lower than a light emission current to be flowed to the long wavelength light emitting device, and makes the short wavelength light emitting device and the long wavelength light emitting device perform a simultaneous light emission;

the second detection processing section obtains the second long wavelength light reception signal from the long wavelength light receiving device, and the second short wavelength light reception signal from the short wavelength light receiving device; and

the smoke type determination section (i) finds a first output ratio, which is found by dividing the first long wavelength light reception signal by the second short wavelength light reception signal, (ii) it estimates the diameter of the particles of the smoke as being smaller than a predetermined value if the first output ratio is less than 1, (iii) having established this estimation, it finds a second output ratio, which is found by dividing the second long wavelength light reception signal by the second short wavelength light reception signal, and then (iv) it determines the result of the estimation as being correct if this second output ratio is 1 or higher.

9. The smoke detector according to claim 5, wherein:

the light emission control section makes a light emission current to be flowed to the short wavelength light emitting device lower than a light emission current to be flowed to the long wavelength light emitting device, and makes the short wavelength light emitting device and the long wavelength light emitting device perform a simultaneous light emission;

the second detection processing section obtains the second long wavelength light reception signal from the long wavelength light receiving device, and the second short wavelength light reception signal from the short wavelength light receiving device; and

the smoke type determination section (i) finds a first output ratio, which is found by dividing the first long wavelength light reception signal by the first short wavelength light reception signal, (ii) it estimates the diameter of the particles of the smoke as being greater than a predetermined value if this first output ratio is 1 or higher, (iii) having established this estimation, it finds a second output ratio, which is found by dividing the second long wavelength light reception signal by the second short wavelength light reception signal, and then (iv) it determines the result of the estimation as being correct if this second output ratio is 1 or higher.

10. The smoke detector according to claim 5, wherein:

the light emission control section makes a light emission current to be flowed to the short wavelength light emitting device lower than a light emission current to be flowed to the long wavelength light emitting device, and makes the short wavelength light emitting device and the long wavelength light emitting device perform a simultaneous light emission;

the second detection processing section obtains the second long wavelength light reception signal from the long wavelength light receiving device, and the second short wavelength light reception signal from the short wavelength light receiving device; and

the smoke type determination section (i) finds a first output ratio, which is found by dividing the first long wavelength light reception signal by the first short wavelength light reception signal, (ii) it estimates the diameter of the particles of the smoke as being smaller than a predetermined value if this first output ratio is less than 1, (iii) having established this estimation, it finds a second output ratio, which is found by dividing the second long wavelength light reception signal by the second short wavelength light reception signal, and then (iv) it determines the result of the estimation as being correct if this second output ratio is less than 1.

11. The smoke detector according to claim 5, wherein:

the light emission control section makes a light emission current to be flowed to the short wavelength light emitting device lower than a light emission current to be flowed to the long wavelength light emitting device, and makes the short wavelength light emitting device and the long wavelength light emitting device perform a simultaneous light emission;

the second detection processing section obtains the second long wavelength light reception signal from the long wavelength light receiving device, and the second short wavelength light reception signal from the short wavelength light receiving device; and

the smoke type determination section (i) finds a first output ratio, which is found by dividing the first long wavelength light reception signal by the second short wavelength light reception signal, (ii) it estimates the diameter of the particles of the smoke as being greater than a predetermined value if this first output ratio is 1 or higher, (iii) having established this estimation, it finds a second output ratio, which is found by dividing the second long wavelength light reception signal by the second short wavelength light reception signal, and then (iv) it determines the result of the estimation as being correct if this second output ratio is less than 1.

12. The smoke detector according to claim 5, wherein:

the light emission control section makes a light emission current to be flowed to the short wavelength light emitting device lower than a light emission current to be flowed to the long wavelength light emitting device, and makes the short wavelength light emitting device and the long wavelength light emitting device perform a simultaneous light emission;

the second detection processing section obtains the second long wavelength light reception signal from the long wavelength light receiving device, and the second short wavelength light reception signal from the short wavelength light receiving device; and

the smoke type determination section (i) finds a first output ratio, which is found by dividing the first long wavelength light reception signal by the second short wavelength light reception signal, and a second output ratio, which is found by dividing the second long wavelength light reception signal by the second short wavelength light reception signal, and (ii) it determines the diameter of the particles of the smoke as being smaller than a predetermined value if the rate of change from the first output ratio to the second output ratio is greater than or equal to a predetermined threshold value, or, it determines the diameter of the particles of the smoke as being greater than the predetermined value if the rate of change is less than the threshold value.

13. The smoke detector according to claim 5, wherein:

the light emission control section makes a light emission current to be flowed to the short wavelength light emitting device lower than a light emission current to be flowed to the long wavelength light emitting device, and makes the short wavelength light emitting device and the long wavelength light emitting device perform a simultaneous light emission;

the second detection processing section obtains the second long wavelength light reception signal from the long wavelength light receiving device, and the second short wavelength light reception signal from the short wavelength light receiving device; and

the smoke type determination section (i) finds a first output ratio, which is found by dividing the first long wavelength light reception signal by the second short wavelength light reception signal, and a second output ratio, which is found by dividing the second long wavelength light reception signal by the second short wavelength light reception signal, and (ii) it determines the diameter of the particles of the smoke as being smaller than a predetermined value if the rate of change from the first output ratio to the second output ratio is less than a predetermined threshold value, or, it determines the diameter of the particles of the smoke as being greater than the predetermined value if the rate of change is greater than or equal to the threshold value.

14. A smoke detector comprising:

a first scattered light detection section in which a long wavelength light emitting device which emits a first light beam having a predetermined long wavelength, and a long wavelength light receiving device which receives first scattered light generated due to the first light beam emitted from this long wavelength light emitting device impinging on smoke, are arranged with a first scattering angle;

a second scattered light detection section in which a short wavelength light emitting device which emits a second light beam having a predetermined short wavelength which is shorter than the long wavelength, and a short wavelength light receiving device which receives second scattered light generated due to the second light beam emitted from this short wavelength light emitting device impinging on smoke, are arranged with a second scattering angle, which differs from the first scattering angle;

a light emission control section which makes the long wavelength light emitting device and the short wavelength light emitting device to simultaneously perform light emission with the same light emission current;

a detection processing section which obtains a long wavelength light reception signal from the long wavelength light receiving device, and a short wavelength light reception signal from the short wavelength light receiving device; and

a smoke type determination section which determines the type of the smoke, based on the long wavelength light reception signal and the short wavelength light reception signal,

wherein the first scattered light detection section and the second scattered light detection section are arranged in order to match a detection point of the first scattered light detection section and a detection point of the second scattered light detection section.

15. The smoke detector according to claim 14, wherein

the smoke type determination section:

(i) sets a first output ratio, which is found by dividing a known long wavelength light reception signal obtained with respect to one or more types of preliminarily determined smoke by a known short wavelength light reception signal, as a threshold value;

(ii) finds a second output ratio, which is found by dividing the long wavelength light reception signal obtained in the detection processing section with respect to unknown smoke, by the short wavelength light reception signal; and

(iii) compares this second output ratio with the threshold value to thereby determined the type of the smoke.

16. The smoke detector according to claim 14, wherein

a position of the short wavelength light emitting device of the second scattered light detection section is arranged so as to be horizontal-rotationally displaced about a predetermined axis, with respect to a position of the long wavelength light emitting device of the first scattered light detection section.

17. The smoke detector according to claim 14, further comprising a detector main body having a flat exposed surface, wherein:

the long wavelength light emitting device, the long wavelength light receiving device, the short wavelength light emitting device, and the short wavelength light receiving device are respectively embedded in the exposed surface;

the first light beam emitted from the long wavelength light emitting device and the second light beam emitted from the short wavelength light emitting device are irradiated into an external smoke detection space which the exposed surface faces, to thereby generate the first scattered light and the second scattered light generated due to these light beams impinging on the smoke within the external smoke detection space; and

the first scattered light is received by the long wavelength light receiving device while the second scattered light is received by the short wavelength light receiving device.