Patent Publication Number: US-7911350-B2

Title: Alcohol detection system

Description:
BACKGROUND 
     The present invention relates to an alcohol detection system to detect the level of alcohol consumed by a person. As one example, a drunk driving detection system is provided for a motor vehicle that detects mainly an alcohol drinking condition of the driver. 
     In recent years, a drunk driving detection system for detecting an alcohol drinking condition of a driver has been developed to reduce the number of accidents caused by drunk driving. Further, studies are made on various systems for controlling the start and operation of a motor vehicle (hereinafter referred to as “vehicle”) based on the output from the drunk driving detection system. 
     In such a drunk driving detection system, an alcohol sensor detects a concentration of alcohol typically in exhalation. This system utilizes the proportionality between the alcohol concentration in the blood increased by alcohol-drinking and the alcohol concentration in the exhalation. Such types of systems are also used in crackdown of drunk driving. However, in detection of an alcohol drinking condition of a driver by this method, illicit acts cannot be eliminated. Such illicit acts include packing into a balloon the air exhaled by another non-drunk person, or the air exhaled when the driver drinks no alcohol, and blowing the air into the drunk driving detection system. Further, when a drunk driving detection system is installed inside of a vehicle, alcohol contained in the air exhaled by a fellow passenger or in an aromatic substance such as fragrance can cause the system to erroneously detect that the driver is drunk. 
     A drunk driving detection system is provided that detects an alcohol concentration in the perspiration, which is proportional to the alcohol concentration in the blood, like an alcohol concentration in the exhalation.  FIG. 15  is a schematic diagram showing the structure of such a drunk driving detection system. 
     Sensor elements  105  for detecting alcohol are provided in parts of a steering wheel  101  and a speed change gear knob  103  which are located near the drivers seat of a vehicle and which are to be in contact with the palms of the driver. Each sensor element  105  is made of a pair of electrodes, and an alcohol-sensitive film covering the electrodes. Sensor element  105  utilizes a phenomenon that absorption of an alcohol component to the alcohol-sensitive film changes the resistance between the electrodes. Thus, when the perspiration vapor generated from the palms reaches sensor element  105 , the sensor element can detect an alcohol concentration in the perspiration. The output signal from sensor element  105  is transmitted to alcohol concentration measurement unit  107 , where an alcohol concentration is obtained. The alcohol concentration output obtained in alcohol concentration measurement unit  107  is transmitted to drunk driving determiner  109 , where an alcohol drinking condition of the driver is determined. The determination result is transmitted to post-stage processor  111 . If the driver is in a drunk condition, post-stage processing, such as inhibition, warning, prevention, and control of drunk driving, is performed. Specifically, post-stage processor  111  locks the vehicle to inhibit the start thereof, or reduces the speed while the vehicle is running. 
     In this manner, installation of sensor elements  105  in a steering wheel and a speed change gear knob  103  to be operated by a driver allows the detection of the alcohol concentration in the perspiration of the driver. Thus, the possibility of illicit acts or erroneous detection can be reduced in comparison with the alcohol detection using the exhalation. 
     Further, after piezoelectric elements or the like disposed in proximity to sensor elements  105  determine whether or not the hand of a driver has touched steering wheel  101 , the drunk driving detection system is activated. Thus, the detection accuracy is improved. 
     Such a drunk driving detection system can detect an alcohol drinking condition of the driver with high accuracy. However, disposition of the piezoelectric elements or the like in proximity to sensor elements  105  causes the following problems. For example, when the driver places the palm on steering wheel  101  so that the palm touches the piezoelectric element but does not touch sensor element  105 , the alcohol concentration in the perspiration from the palm is not detected although the drunk driving detection system is activated. As a result, illicit acts for evading detection of an alcohol drinking condition can be performed. 
     SUMMARY 
     A drunk driving detection system of the present invention is incorporated in a motor vehicle, and includes a steering wheel, a film, a pair of contact detection electrodes, an alcohol sensor, and a control circuit. The steering wheel provided with an opening in a portion thereof to be grasped by a driver. The film is liquid-impermeable and air-permeable, and covers the opening. The contact detection electrodes are provided on the surface of the film. The alcohol sensor is provided in a space in communication with the opening. The control circuit is connected to the contact detection electrodes and the alcohol sensor, and measures the resistance between the contact detection electrodes. When the resistance is within a predetermined range, the control circuit determines that the driver is in contact with the film and detects an alcohol drinking condition of the driver based on the output from the alcohol sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view of a drunk driving detection system in accordance with a first exemplary embodiment of the present invention. 
         FIGS. 2A through 2C  are plan views showing configurations of pairs of contact detection electrodes in the drunk driving detection system of  FIG. 1 . 
         FIG. 3  is a block circuit diagram of the drunk driving detection system of  FIG. 1 . 
         FIG. 4  is an exploded perspective view of an alcohol sensor in the drunk driving detection system of  FIG. 1 . 
         FIG. 5  is a perspective view of an alcohol detecting element in the alcohol sensor of  FIG. 4 . 
         FIG. 6  is a sectional view of the alcohol detecting element in the alcohol sensor of  FIG. 4 . 
         FIG. 7  is a flowchart showing the operation of the drunk driving detection system of  FIG. 1 . 
         FIGS. 8 through 10  are schematic sectional views of other structures of the drunk driving detection system in accordance with the first exemplary embodiment of the present invention. 
         FIG. 11  is a schematic sectional view of a drunk driving detection system in accordance with a second exemplary embodiment of the present invention. 
         FIG. 12  is a block circuit diagram of the drunk driving detection system of  FIG. 11 . 
         FIG. 13  is a flowchart showing the operation of the drunk driving detection system of  FIG. 11 . 
         FIG. 14  is a block circuit diagram of another structure of the drunk driving detection system in accordance with the exemplary embodiments of the present invention. 
         FIG. 15  is a schematic view showing a structure of a conventional drunk driving detection system. 
     
    
    
     DETAILED DESCRIPTION 
     First Exemplary Embodiment 
       FIG. 1  is a schematic sectional view of a drunk driving detection system in accordance with a first exemplary embodiment of the present invention.  FIGS. 2A through 2C  are plan views showing configurations of pairs of contact detection electrodes in the drunk driving detection system.  FIG. 3  is a block circuit diagram of the drunk driving detection system of  FIG. 1 .  FIG. 4 ,  FIG. 5 , and  FIG. 6  are an exploded perspective view, a perspective view, and a sectional view, respectively, of an alcohol sensor in the drunk driving detection system.  FIG. 7  is a flowchart showing the operation of the drunk driving detection system of  FIG. 1 .  FIG. 8 ,  FIG. 9 , and  FIG. 10  are schematic sectional views of other structures of the drunk driving detection system in accordance with this exemplary embodiment. 
     This drunk driving detection system is to be incorporated into a motor vehicle. The drunk driving detection system includes steering wheel  13 , films  17 , a pair of first contact detection electrodes  21 A, first alcohol sensor  19 A, a pair of second contact detection electrodes  21 B, second alcohol sensor  19 B, and control circuit  29 . Steering wheel  13  is provided with openings  15  in portions thereof to be grasped by a driver. Films  17  cover openings  15 . Contact detection electrodes  21 A and  21 B are provided on the surfaces of respective films  17 . Each of alcohol sensors  19 A and  19 B is provided in a space inside of steering wheel  13  in communication with corresponding openings  15 . With reference to  FIG. 1 , alcohol sensors  19 A and  19 B are provided in proximity to openings  15 . Control circuit  29  is connected to contact detection electrodes  21 A and  21 B, and alcohol sensors  19 A and  19 B as shown in  FIG. 3 . Control circuit  29  measures the resistance between contact detection electrodes  21 A and the resistance between contact detection electrodes  21 B. When at least one of the resistance values is within a predetermined range, the control circuit determines that the driver is in contact with at least one of films  17  and detects an alcohol drinking condition of the driver based on the output from at least one of alcohol sensors  19 A and  19 B. 
     Alcohol detection parts  11  are incorporated within steering wheel  13 . Alcohol detection parts  11  are disposed in two positions in steering wheel  13 . The detailed structure of each alcohol detection part  11  is as follows. Alcohol detection part  11  is formed in a space made by hollowing a part of steering wheel  13 . Along the outer periphery of steering wheel  13 , opening  15  for capturing the perspiration vapor from a palm is provided. Film  17  is provided so as to cover the entire part of opening  15 . Behind openings  15 , i.e. inside of steering wheel  13 , alcohol sensors  19 A and  19 B are provided. 
     Each film  17  works to pass only the perspiration vapor and no liquid perspiration from the palm. In other words, film  17  is liquid-impermeable and air-permeable. Alcohol sensors  19 A and  19 B provided behind openings  15  detect a concentration of alcohol that is contained in the perspiration vapor introduced from openings  15  through films  17 . 
     As described above, film  17  is liquid-impermeable. This property can reduce failures such that wet alcohol sensors  19 A and  19 B cannot detect an alcohol concentration. As film  17  having such property, an oriented porous fluorocarbon resin can be used. Film  17  is extremely thinner than steering wheel  13 ; however, in order to simplify understanding,  FIG. 1  shows the thickness of films  17  larger than the actual thickness. Beam-shaped members for supporting the entire part of films  17  are also disposed in contact with films  17 . However, the beam-shaped members are omitted in  FIG. 1 . 
     Provided on the surfaces of films  17  are pairs of contact detection electrodes  21 A and  21 B having either one of configurations shown in  FIG. 2A through 2C . Contact detection electrodes  21 A and  21 B are provided in order to detect whether or not openings  15  (films  17 ) are in contact with the palms. Hereinafter, a description is provided of contact detection electrodes  21 A as an example. 
     Control circuit  29  of  FIG. 3  determines that a palm is in contact with film  17  by detecting the resistance between contact detection electrodes  21 A, i.e. the resistance of the skin of the palm. In this manner, control circuit  29  detects that the palm is in contact with film  17  provided over opening  15  by contact detection electrodes  21 A. Further, in this condition, control circuit  29  detects an alcohol concentration in the perspiration of the palm by alcohol sensors  19 A and  19 B. Thus, illicit acts can be reduced. 
     Film  17  is made of a resin and thus has electrical insulating property. Therefore, contact detection electrodes  21 A are directly fixed onto the surface of film  17  so that they are out of contact with each other. When film  17  has electrical conductivity, contact detection electrodes  21 A may be fixed to film  17  with an insulating layer disposed therebetween. 
     Next, a description is provided of the detailed structure of contact detection electrodes  21 A, with reference to  FIGS. 2A through 2C . These drawings are plan views as film  17  is seen from the outside thereof. 
     Contact detection electrodes  21 A have a configuration in which they are intricate into each other. For example,  FIG. 2A  shows a spiral configuration. In this configuration, it is extremely difficult to perform an illicit act of covering only film  17  with a moisture-impermeable film or the like while intentionally avoiding covering contact detection electrodes  21 A so that an alcohol drinking condition is not detected. If the entire part of opening  15  is covered with a moisture-impermeable film or the like, the skin resistance is always undetectable by contact detection electrodes  21 A. Thus, control circuit  29  can determine an illicit act. 
     Other than the spiral configuration of  FIG. 2A , contact detection electrodes  21 A can be configured in a comb-shaped configuration of  FIG. 2B  or a star-shaped configuration of  FIG. 2C  in which the two electrodes are intricate into each other. Any configuration may be used as long as the configuration hinders covering not contact detection electrodes  21 A but only film  17  with a moisture-impermeable film or the like. 
     Next, a description is provided of the detailed structure of alcohol sensors  19 A and  19 B, with reference to  FIGS. 4 through 6 . A description is provided of alcohol sensor  19 A as an example. 
       FIG. 4  is an exploded perspective view of alcohol sensor  19 A. Alcohol detecting element  1  is fixed onto base  2 . Base  2  has four pins  3  penetrating through base  2 . The top face of each pin  3  is connected to alcohol detecting element  1  by two gold wires  4 . The use of each two wires  4  allows continuous use of alcohol sensor  19 A even if one of wires  4  is broken, because the other of wires  4  is still connected. Thus, the reliability is improved. Cap  8  including hole  7  is fitted over base  2 . Base  2  and cap  8  are fixed to each other by resistance welding. Over hole  7 , stainless-steel net  9  is fixed with cap  8 . Thus, perspiration vapor reaches alcohol detecting element  1  through net  9  disposed over hole  7 . 
     Next, a description is provided of the detailed structure of alcohol detecting element  1 .  FIG. 5  is a perspective view of alcohol detecting element  1 .  FIG. 6  is a sectional view thereof. Alcohol detecting element  1  includes micro heater  41  having a meander pattern on the surface of silicon pedestal  40 , and semiconductor device  43  of a thin film formed on micro heater  41 . Micro heater  41  is formed of a platinum thin film, and thus is capable of enduring high temperatures. Semiconductor device  43  is formed of a thin-film of tin oxide. Both ends of micro heater  41  are connected to lands  42 A. Further, semiconductor device  43  is coupled to lands  42 B via extraction electrodes  44 . Lands  42 A and  42 B are connected to wires  4  shown in  FIG. 4 . 
     As shown in  FIG. 6 , micro heater  41  and semiconductor device  43  are formed on the surface (the top face in  FIG. 6 ) opposite to the surface that has recess  40 A formed by micromachining. The thickness of thin plate part  40 C formed by recess  40 A is approximately 10 μm, for example. In order to prevent the short circuit between pedestal  40  made of silicon, i.e. a semiconductor, and micro heater  41 , insulating layer  45  is formed between thin plate part  40 C and micro heater  41 . Thus, micro heater  41  is formed on the top face of insulating layer  45 . Extraction electrodes  44  and semiconductor device  43  are further formed on the top face of micro heater  41  via insulating layer  45 . In this manner, micro heater  41  is electrically insulated from pedestal  40  and semiconductor device  43 . 
     Providing micro heater  41  on thin plate part  40 C in this manner can extremely reduce the heat capacity. Further, providing gap  40 B to minimize the portion connected to pedestal  40  can inhibit heat conduction to pedestal  40 . Thermal coupling between micro heater  41  and semiconductor device  43  via insulating layer  45  facilitates heat conduction to semiconductor device  43 . With these structures, the heat capacity of micro heater  41  is extremely reduced, and semiconductor device  43  can be heated to a sufficient temperature even at minute electric current. Each of micro heater  41 , semiconductor device  43 , extraction electrodes  44 , and insulating layers  45  has a thickness of approximately several micrometers. However,  FIG. 6  shows the dimensions thereof exaggeratingly larger than the actual dimensions to simplify understanding. 
     Semiconductor device  43  detects an alcohol concentration in a condition heated by micro heater  41  to a temperature appropriate for alcohol detection. This temperature depends on the material of semiconductor device  43 , and is approximately several hundred degrees Celsius. However, large power is consumed to keep semiconductor device  43  at such a high temperature. For this reason, semiconductor device  43  is located immediately above micro heater  41 . This structure can extremely reduce the heat capacity of alcohol sensor  19 A. Thus, the temperature of semiconductor device  43  can be risen to a preset temperature at a low current, e.g. approximately several milliamperes, within a short time period, e.g. 0.1 second or shorter. 
     When an alcohol component is brought into contact with semiconductor device  43  heated by micro heater  41 , with oxidation of the alcohol component, semiconductor device  43  is reduced. As a result, the resistance of semiconductor device  43  changes. In a case that semiconductor device  43  is made of a tin oxide, the resistance decreases. Control circuit  29  measures changes in the resistance between lands  42 B to calculate the alcohol concentration. 
     Meanwhile, the alcohol concentration need not be detected at all times. The alcohol concentration may be detected only when it is detected that a palm has made contact with film  17  by contact detection electrodes  21 A or contact detection electrodes  21 B after the out-of-contact state. For this reason, the alcohol concentration is detected using pulse current passing through micro heater  41 . For example, only a current of 7 mA supplied for 0.2 second can complete the temperature rise, thus allowing detection of an alcohol concentration. The use of such current can reduce the power consumption in alcohol sensors  19 A and  19 B. The accuracy in detecting alcohol concentrations can be improved by repeating the detection using pulsed current at a plurality of times and providing an average output value. At this time, control circuit  29  operates only alcohol sensor  19 A when the contact of a palm is detected in contact detection electrodes  21 A, and operates only alcohol sensor  19 B when the contact of a palm is detected in contact detection electrodes  21 B. When the contact of palms is detected in both contact detection electrodes  21 A and  21 B, control circuit  29  activates both alcohol sensors  19 A and  19 B. These operations allow at least one of alcohol sensors  19 A and  19 B to securely be operated with respect to a subject of alcohol detection only, and thus are preferable. 
     The pulse current may be supplied also before the detection of an alcohol concentration by utilizing the fast temperature rise characteristics of alcohol sensors  19 A and  19 B. With this operation, impurities, such as moisture, absorbing to the surface of semiconductor device  43  are removed by heating. This operation allows detection of an alcohol concentration with the surface of semiconductor device  43  in a clean condition. Thus, detection accuracy can further be improved. All the pulse current supplied to alcohol sensors  19 A and  19 B is controlled by control circuit  29 . 
     Each of alcohol sensors  19 A and  19 B may include a plurality of semiconductor devices  43 . Micro heater  41  is fabricated extremely small by micromachining technology. Using this technology, a plurality of micro heaters  41  can collectively be fabricated in one alcohol sensor and semiconductor device  43  is formed on each micro heater. A plurality of semiconductor devices  43  provided in this manner can extend the life of alcohol sensors  19 A and  19 B for the following reason. Even if a failure is caused by deterioration, breakage of wires or the like in one of semiconductor devices  43 , the other normal ones of semiconductor devices  43  can be used in place of the failed one. 
     Further, control circuit  29  may sequentially switch the plurality of semiconductor devices  43  every time an alcohol concentration is detected. In this case, the deterioration degrees of the plurality of semiconductor devices  43  are averaged and the frequency of use per semiconductor device is reduced. This structure extends the life of alcohol sensors  19 A and  19 B. This structure can also inhibit variations in the output from respective semiconductor devices  43 . 
     It is preferable that the intake side of pump  25  is coupled to alcohol detection parts  11  provided with openings  15 , via suction pipes  23  each incorporated in steering wheel  13 . In this structure, pump  25  sucks air containing perspiration vapor through films  17 , and exhausts the air from exhaust port  28 . For example, a small pump, e.g. a piezoelectric pump, can be used as pump  25 , which can be installed in steering wheel  13 . 
     When control circuit  29  detects that a palm is in contact with film  17  by contact detection electrode pair  21 A or contact detection electrode  21 B, control circuit  29  operates pump  25 . This operation causes the perspiration vapor from the palm to be evaporated and positively introduced to alcohol sensors  19 A and  19 B. Thus, alcohol sensors  19 A and  19 B can detect alcohol concentrations in the perspiration vapor at high speeds. It is preferable that exhaust port  28  is provided at a distance from openings  15  so that the alcohol vapor contained in the exhaust air from exhaust port  28  does not affect the detection. 
     In  FIG. 1 , pump  25  is provided inside of steering wheel  13 . However, pump  25  may be provided outside of steering wheel  13  and connected to suction pipes  23  by tubes or the like. 
     It is preferable that pressure sensor  27  is provided between openings  15  and pump  25 . With pressure sensor  27 , control circuit  29  can detect that film  17  is blocked, when the pressure output from pressure sensor  27  during operation of pump  25  is equal to or lower than a predetermined pressure. Then, control circuit  29  determines that alcohol concentrations cannot be measured properly at this time. 
     Next, a description is provided of the circuit structure of the drunk driving detection system, with reference to  FIG. 3 . Alcohol sensors  19 A and  19 B, contact detection electrodes  21 A and  21 B, pump  25 , and pressure sensor  27  are connected to control circuit  29 . Control circuit  29  is made of microcomputers and peripheral circuits, and controls the entire part of the drunk driving detection system. Fed into control circuit  29  are resistance Rs 1  between contact detection electrodes  21 A, resistance Rs 2  between contact detection electrodes  21 B, output Ce 1  from alcohol sensor  19 A, and output Ce 2  from alcohol sensor  19 B, and output P from pressure sensor  27 . The operation of pump  25  is controlled by pump driving signal Pc (including driving power of pump  25 ) from control circuit  29 . 
     Further, control circuit  29  communicates with the vehicle control circuit to exchange various kinds of information, such as detection results of alcohol drinking conditions, and unlocking and locking conditions. The communicated data is fed into and supplied from control circuit  29  as data signal data. 
     Next, a description is provided of the operation of the drunk driving detection system, with reference to the flowchart of  FIG. 7 . This flowchart shows a subroutine to be executed every predetermined period of time (e.g. every one minute) from the main routine (not shown). 
     When the main routine executes the subroutine of  FIG. 7 , control circuit  29  reads resistance Rs 1  between contact detection electrodes  21 A, and resistance Rs 2  between contact detection electrodes  21 B at first (S 11 ). Next, control circuit  29  determines whether or not resistance Rs 1  is within a predetermined range (S 13 ). The predetermined range of resistance Rs 1  is a range within which skin resistance exists. In this exemplary embodiment, the range is set from 2 kΩ to 5 kΩ inclusive. However, this range varies with the size and shape of contact detection electrodes  21 A and the distance between the two electrodes. Thus, the range of the skin resistance corresponding to contact detection electrodes  21 A is predetermined and stored in a memory of control circuit  29 . 
     When resistance Rs 1  is within the predetermined range (Yes in S 13 ), control circuit  29  determines that the left hand is in contact with contact detection electrodes  21 A. Next, control circuit  29  determines whether or not the right hand is also in contact with contact detection electrodes  21 B. Specifically, control circuit  29  determines whether or not resistance Rs 2  between contact detection electrodes  21 B is within a predetermined range (S 15 ). The predetermined range of resistance Rs 2  is equal to that of resistance Rs 1 . 
     When resistance Rs 2  is within the predetermined range (Yes in S 15 ), control circuit  29  determines that the right hand is in contact with contact detection electrode pair  21 B. In other words, control circuit  29  determines that the left and right hands are in contact with contact detection electrodes  21 A and contact detection electrodes  21 B, respectively, at the same time. Then, in order to indicate that the left and right hands are in contact with contact detection electrodes  21 A and  21 B, respectively, control circuit  29  substitutes “3” for contact flag SF (S 17 ). Contact flag SF is a memory built in control circuit  29  and a flag that indicates the following conditions. When SF is “1”, the left hand is in contact with the contact detection electrode pair. When SF is “2”, the right hand is in contact with the contact detection electrode pair. When SF is “3”, both hands are in contact with the contact detection electrode pairs. After S 17 , control is jumped to S 25  to be described later. 
     On the other hand, when resistance Rs 2  is not within the predetermined range (No in S 15 ), control circuit  29  determines that the right hand is not in contact with contact detection electrodes  21 B and only the left hand is in contact. Therefore, “1” is substituted for contact flag SF (S 19 ), and control is jumped to S 25  to be described later. 
     Again with reference to S 13 , when resistance Rs 1  is not within the predetermined range (No in S 13 ), control circuit  29  determines that the left hand is not in contact with contact detection electrodes  21 A and then determines whether or not the right hand is in contact. Specifically, similar to S 15 , control circuit  29  determines whether or not resistance Rs 2  between contact detection electrodes  21 B is within the predetermined range (S 21 ). When resistance Rs 2  is not within the predetermined range (No in S 21 ), control circuit  29  determines that the left and right hands are out of contact with contact detection electrodes  21 A and contact detection electrodes  21 B, respectively. The operation and case assumed in this condition are as follows. The driver is sharply turning steering wheel  13 , or operating components other than steering wheel  13 , such as a shift lever. When the left and right hands are out of contact with contact detection electrodes  21 A and contact detection electrodes  21 B, respectively, in this manner, an alcohol drinking condition cannot be determined. Thus, the subroutine of  FIG. 7  is terminated and control is returned to the main routine. 
     On the other hand, when resistance Rs 2  is within the predetermined range (Yes in S 21 ), control circuit  29  determines that only the right hand is in contact with contact detection electrodes  21 B. Then, “2” is substituted for contact flag SF (S 23 ). 
     Next, control circuit  29  drives pump  25  (S 25 ) and pump  25  sucks the air in the vicinity of openings  15 . The driving power of pump  25  is supplied via control circuit  29 . Thereafter, control circuit  29  determines whether or not a predetermined period of suction time has elapsed (S 27 ). The predetermined period of suction time is a period during which pump  25  is driven to replace all the air in two alcohol detection parts  11 . When the predetermined period of suction time has not elapsed (No in S 27 ), control is returned to S 27  and control circuit  29  waits for the lapse of the predetermined period of suction time. When the predetermined period of suction time has elapsed (Yes in S 27 ), control circuit  29  reads the output (pressure output P) from pressure sensor  27  (S 29 ). Thereafter, control circuit  29  determines whether or not pressure output P is equal to or lower than a predetermined pressure (S 31 ). The predetermined pressure is set at an absolute pressure of 0.051 MPa, for example. If openings  15  are illicitly blocked so that alcohol detection can be evaded, pressure output P from pressure sensor  27  disposed between openings  15  and pump  25  is reduced to a value equal to or lower than the predetermined pressure. Thus, monitoring pressure output P allows determination of illicit acts. 
     When pressure output P is equal to or lower than the predetermined pressure (Yes in S 31 ), it is possible that illicit acts, such as blocking openings  15 , are performed. Thus, abnormality in pressure is warned by an alarm (S 33 ), and the subroutine of  FIG. 7  is terminated. 
     On the other hand, when pressure output P is higher than the predetermined pressure (No in S 31 ), control circuit  29  determines that the perspiration vapor in the vicinity of the palm has normally been introduced into alcohol detection part  11 . Next, control circuit  29  determines whether or not contact flag SF is “1” (S 35 ). When SF is “1” (Yes in S 35 ), only the left hand is in contact with contact detection electrodes  21 A and thus control is jumped to S 41  to be described later. On the other hand, when SF is not “1” (No in S 35 ), at least the right hand is in contact with contact detection electrodes  21 B and thus control circuit  29  reads output Ce 2  from alcohol sensor  19 B (S 37 ). Thereafter, control circuit  29  determines whether or not contact flag SF is “2”, in order to determine whether or not the left and right hands are in contact with contact detection electrodes  21 A and contact detection electrodes  21 B, respectively (S 39 ). 
     When SF is “2” (Yes in S 39 ), only the right hand is in contact with contact detection electrodes  21 B and thus control is jumped to S 43  to be described later. On the other hand, when SF is not “2” (No in S 39 ), SF is “3” and the left and right hands are in contact with contact detection electrodes  21 A and contact detection electrodes  21 B, respectively. Output Ce 2  from alcohol sensor  19 B has already been read in S 37 , and then output Ce 1  from alcohol sensor  19 A is read (S 41 ). With these operations, when only the left hand is in contact with the contact detection electrode pair, i.e. when SF is “1”, control circuit  29  reads output Ce 1  from alcohol sensor  19 A. When only the right hand is in contact with the contact detection electrode pair, i.e. when SF is “2”, control circuit  29  reads output Ce 2  from alcohol sensor  19 B. When both hands are in contact with the contact detection electrode pairs, i.e. when SF is “3”, control circuit  29  reads both outputs Ce 1  and Ce 2 . 
     Thereafter, control circuit  29  determines whether or not either output Ce 1  or output Ce 2  is equal to or larger than an alcohol drinking regulation value (S 43 ). The alcohol drinking regulation value is set at a concentration of alcohol in perspiration vapor that corresponds to the concentration of alcohol in exhalation used to determine alcohol intoxication in regulation of drunk driving. For example, this value is specified as 0.15 mg per 1 L of exhalation according to Japan Road Traffic Law as of 2007. The alcohol drinking regulation value is predetermined as a value corresponding to the concentration used to determine alcohol intoxication, and stored in a memory of control circuit  29 . 
     When neither output Ce 1  nor output Ce 2  is equal to or larger than the alcohol drinking regulation value (No in S 43 ), control circuit  29  determines that the driver is not drunk. Then, the subroutine of  FIG. 7  is terminated, and control is returned to the main routine. On the other hand, when either output Ce 1  or output Ce 2  is equal to or larger than the alcohol drinking regulation value (Yes in S 43 ), control circuit  29  determines that the driver is drunk. In this case, control circuit  29  transmits a drinking alarm signal for the driver to the vehicle control circuit (S 45 ). Upon receipt of the signal, the vehicle control circuit displays a warning to the driver in an indicator of the vehicle or the like. 
     Because continuing driving in the drunk condition is dangerous, control circuit  29  transmits a vehicle control signal to the vehicle control circuit (S 47 ). Upon receipt of the vehicle control signal, the vehicle control circuit prompts the driver to stop the vehicle safely by forcing to decelerate the vehicle or controlling the vehicle so that the speed thereof is kept up to a predetermined value or lower. Alternatively, at the start of the vehicle, the start of the engine is inhibited. Thereafter, the subroutine of  FIG. 7  is completed and control is returned to the main routine. 
     As described above, control circuit  29  determines that a palm is in contact with film  17 , when at least one of resistance Rs 1  between contact detection electrodes  21 A and resistance Rs 2  between contact detection electrodes  21 B is within a predetermined range. When output Ce 1  from alcohol sensor  19 A or output Ce 2  from alcohol sensor  19 B with respect to the perspiration vapor sucked by pump  25  is equal to or larger than the alcohol drinking regulation value in this condition, control circuit  29  determines that the driver is drunk. 
     Though not shown in  FIG. 7 , it is preferable that control circuit  29  operates pump  25  at least when the vehicle is locked or unlocked. Then, output Ce 1  from alcohol sensor  19 A and output Ce 2  from alcohol sensor  19 B at that time are set as a value at which no alcohol is detected for calibration. With this setting, the zero point output from alcohol sensors  19 A and  19 B can be corrected every time when the vehicle is used. Thus, alcohol drinking conditions can be determined with high accuracy. 
     With the above structures and operations, control circuit  29  drives pump  25  only when control circuit  29  detects that a palm is in contact with film  17  covering opening  15 , by the contact detection electrode pairs. This mechanism allows the perspiration from the palm to be positively evaporated and introduced into alcohol detection part  11 , thus providing a high-accuracy drunk driving detection system capable of reducing the possibility of illicit acts and detecting alcohol concentrations in the perspiration vapor at a high speed. 
     In this exemplary embodiment, each of alcohol sensors  19 A and  19 B is made of thin-film semiconductor device  43  provided on micro heater  41 . However, the present invention is not limited to this structure. For example, a catalytic-combustion alcohol sensor may be used. In such a type of sensor, a catalyst is provided on the micro heater and heated to a temperature appropriate for alcohol detection, and the temperature changes caused by alcohol combustion are detected. This type of alcohol sensor is small and has low power consumption, and thus is also preferable. 
     In this exemplary embodiment, two alcohol sensors  19 A and  19 B are used. However, as shown in  FIG. 8 , only one alcohol sensor  19  may be provided on the exhaust side of pump  25 . In this case, only one alcohol sensor  19  does not have errors caused by variations in the output when a plurality of alcohol sensors  19  are provided, thus further improving the detection accuracy. However, in comparison with the structure including alcohol sensors  19 A and  19 B in alcohol detection parts  11 , it takes more time for the perspiration vapor to reach alcohol sensor  19  in this structure, and thus requires a countermeasure, such as improvement of the suction capability of pump  25 . 
     Further, in this structure, pump  25  sucks air from both openings  15 , even when control circuit  29  detects contact in either one of contact detection electrodes  21 A and  21 B, i.e. when SF is “1” or “2”. For this reason, similar to the second exemplary embodiment to be described later, correction to the output from alcohol sensor  19  is necessary in either of the case when SF is “1” or “2”, and the case when SF is “3”. 
     In this exemplary embodiment, alcohol detection parts  11  are provided in two positions in steering wheel  13 . However, alcohol detection part  11  can be provided in at least one position. Disposing the alcohol detection part only in one position reduces the probability that a palm makes contact with film  17 . This may raise the possibility that drunk driving cannot be determined adequately. 
     To address this problem, it is more preferable that a plurality of alcohol detection parts  11  (in 19 positions in  FIG. 9 ), for example, are provided across steering wheel  13 . Specifically, a plurality of openings  15  are provided in steering wheel  13 , and partition walls  30  are provided between adjacent openings  15  inside of steering wheel  13 . Then, alcohol sensor  19  is provided behind each of openings  15 , and the suction side of pump  25  is connected to each of the openings  15 . With this structure, even when a palm grasps any portion of steering wheel  13 , the palm makes contact with one of films  17  and thus alcohol concentrations in perspiration vapor can be detected at all times. The structure of  FIG. 9  includes 19 alcohol sensors. For the detection of an alcohol drinking condition, control circuit  29  can use the output only from alcohol sensors  19  behind openings  15  that have contact detection electrode pairs having a resistance within the predetermined range. 
     In the structure of  FIG. 9 , existence of a large number of alcohol sensors  19  can increase variations in output and decrease the accuracy in detecting an alcohol drinking condition. To determine an alcohol drinking condition with high accuracy, the drunk driving detection system may have a structure of  FIG. 10 . In this structure, pumps  25  are connected to openings  15  respectively and only one alcohol sensor  19  is provided in an integral part of pumps  25  on the exhaust side.  FIG. 10  shows a structure including two openings  15  and two pumps  25 , as an example. In this case, control circuit  29  operates only one of pumps  25  connected to opening  15  that includes a contact detection electrode pair having a resistance within the predetermined range. This mechanism prevents dilution of the perspiration vapor and thus allows detection of an alcohol drinking condition with high accuracy. 
     In this case, when one of pumps  25  is not driven, air is sucked only from opening  15  connected to the other one of pumps  25 . Thus, the output from alcohol sensor  19  need not be corrected according to the SF value. 
     Second Exemplary Embodiment 
       FIG. 11  is a schematic sectional view of a drunk driving detection system in accordance with a second exemplary embodiment of the present invention.  FIG. 12  is a block circuit diagram of the drunk driving detection system.  FIG. 13  is a flowchart showing the operation of the drunk driving detection system. In the structure of the drunk driving detection system of the second embodiment, elements similar to those in the first embodiment have the same reference marks, and the detailed descriptions of those elements are omitted. 
     As shown in  FIG. 11 , the structure of this exemplary embodiment features that an alcohol sensor is formed of infrared light source (hereinafter “light source”)  51  and infrared sensor (hereinafter “sensor”)  53  both incorporated within steering wheel  13 . Specifically, as shown by the dotted line in  FIG. 11 , an infrared ray generated from light source  51  repeatedly reflects in optical path  55  disposed along the circumferential direction of steering wheel  13  and reaches sensor  53 . Light source  51  and sensor  53  are thus disposed. Further, openings  15  are provided through the surface of steering wheel  13  including optical path  55 . Pump  25  is connected to optical path  55  by suction pipe  23 . In this exemplary embodiment, as shown in  FIG. 11 , openings  15  are provided in two positions on the left and right sides in steering wheel  13 . Light source  51  is disposed behind one of two openings  15  (on the left side in  FIG. 11 ). Sensor  53  is disposed behind the other of openings  15  (on the right side in  FIG. 11 ). 
     Next, a detailed description is provided of each of the featuring elements in this exemplary embodiment. Light source  51  may be formed of a heater. However, in this exemplary embodiment, a pyroelectric element is used as sensor  53 . Thus, sensor  53  need be irradiated with pulse infrared rays. For this purpose, light source  51  is formed of a filament that generates pulse infrared rays according to on-off signals. 
     Sensor  53  is irradiated with pulse infrared rays as described above. However, when sensor  53  is irradiated with infrared rays having any infrared wavelength, detection of alcohol components is difficult. To address this problem, a filter (not shown) that selectively passes the infrared rays having wavelengths responsive to alcohol components is deposed above light source  51 . 
     Infrared rays emitted from light source  51  through the filter are absorbed by alcohol components. Sensor  53  measures the intensity of the infrared rays that are not absorbed by the alcohol components and reach sensor  53 . Control circuit  29  calculates the concentrations of the alcohol components based on the output from sensor  53 . 
     Optical path  55  provided between light source  51  and sensor  53  is shaped like a cylinder formed in a part of the inside of steering wheel  13 . The surface of optical path  55  is gold-plated so as to efficiently reflect the infrared rays. In this structure, as shown by the dotted line in  FIG. 11 , an infrared ray emitted from light source  51  repeatedly reflects on the surface of optical path  55  and reaches sensor  53 . This structure increases the optical path length from light source  51  to sensor  53 , and the output sensitivity of sensor  53 , thus allowing detection of alcohol concentrations with high accuracy. 
     Formed on the surfaces of films  17  provided over two openings  15  are contact detection electrodes  21 A and  21 B having one of the configurations shown in  FIG. 2A through 2C . Control circuit  29  operates pump  25  when at least one of a resistance between contact detection electrodes  21 A and a resistance between contact detection electrodes  21 B is within a predetermined range. With this structure, the perspiration vapor can positively be introduced across optical path  55 , and infrared rays pass through the perspiration vapor. This structure allows alcohol components to be selected from the perspiration vapor and detected with high accuracy. The structure other than described above is similar to that of the first exemplary embodiment. 
     Next, a description is provided of a circuit structure of this exemplary embodiment, with reference to  FIG. 12 . In  FIG. 12 , elements similar to those in  FIG. 3  have the same reference marks, and the detailed descriptions of those elements are omitted. 
     The structure of  FIG. 12  features that light source  51  and sensor  53  are connected in place of alcohol sensors  19 A and  19 B of the first exemplary embodiment. In this structure, control circuit  29  supplies pulse drive current IRP to light source  51 , and reads output Ce from sensor  53 . The circuit structure other than described above is similar to that of the first exemplary embodiment. 
     Next, a description is provided of the operation in this exemplary embodiment, with reference to  FIG. 13 . In  FIG. 13 , the operations similar to those in  FIG. 7  have the same step numbers, and the detailed descriptions of those steps are omitted. 
     In steps S 11  through S 33 , the operations same as those in the first exemplary embodiment are performed. In the case of No in S 31 , control circuit  29  supplies pulse drive current IRP to light source  51  so that pulse infrared rays are generated for a predetermined period of time. Further, control circuit  29  reads output Ce from sensor  53  at that time (S 51 ). Thereafter, control circuit  29  determines whether or not contact flag SF is “3” (S 53 ). When SF is not “3” (No in S 53 ), control is jumped to S 57  to be described later. On the other hand, when SF is “3” (Yes in S 53 ), both hands are in contact with two films  17 , and the perspiration vapor from both hands is introduced into optical path  55 . 
     At this time, when only one hand is in contact with one of films  17 , air is introduced from opening  15  that is not in contact with the other hand. For this reason, the alcohol concentration in the perspiration vapor introduced is diluted to a half the actual alcohol concentration. In this exemplary embodiment, an alcohol drinking condition is determined on the basis of an alcohol concentration in the perspiration vapor from one hand, because the case of one hand has higher probability than the case where both hands are in contact with two films  17 . Thus, when SF is “3”, i.e. both hands are in contact with two films  17 , an alcohol concentration twice the standard concentration is detected. Accordingly, control circuit  29  updates the Ce value by dividing output Ce from sensor  53  by two (S 55 ). 
     Next, control circuit  29  compares output Ce from sensor  53  with an alcohol drinking regulation value (S 57 ). The alcohol drinking regulation value is set to the same value as the first exemplary embodiment. 
     When output Ce is smaller than the alcohol drinking regulation value (No in S 57 ), the driver is determined not to be drunk. Thus, the subroutine of  FIG. 13  is terminated and control is returned to the main routine. On the other hand, when output Ce is equal to or larger than the alcohol drinking regulation value (Yes in S 57 ), the driver is determined to be drunk. Then, similar to the first exemplary embodiment, control circuit  29  transmits a drinking alarm signal for the driver to the vehicle control circuit (S 59 ). Control circuit  29  may also transmit a vehicle control signal to the vehicle control circuit (S 61 ). Upon receipt of the signals, the vehicle control circuit gives an alarm to the driver and forcedly controls the vehicle. Thereafter, the subroutine of  FIG. 13  is completed and control is returned to the main routine. 
     Also with such operations, an alcohol drinking condition of the driver can be determined. Further, unlike the structure of the first exemplary embodiment, the structure of this exemplary embodiment requires only one sensor  53  and one pump  25  for detection of alcohol concentrations, and does not require a plurality of alcohol sensors or pumps. Thus, a drunk driving detection system has a simplified structure. This drunk driving detection system is capable of improving detection accuracy without variations caused by a plurality of alcohol sensors and detecting alcohol drinking conditions at a higher speed, using infrared rays. 
     Similar to the first exemplary embodiment, it is preferable that pump  25  and light source  51  are operated when the vehicle is locked or unlocked, and output Ce from sensor  53  at that time is set as a value at which no alcohol is detected. 
     In this manner, pump  25  and light source  51  are driven only when contact of a palm with film  17  is detected in contact detection electrodes  21 A or  21 B. This operation allows the perspiration from the palm to be positively evaporated and introduced to alcohol detection part  11 , while reducing the possibility of illicit acts. Further, the higher responsibility of sensor  53  allows detection of alcohol concentrations in the perspiration vapor at a higher speed. As power-consuming pump  25  and light source  51  are driven only when required, the power consumption can be reduced. 
     In the above description, openings  15  are provided in two positions on the left and right sides in steering wheel  13 . The openings may be provided in any number of positions through the surface of steering wheel  13  including optical path  55 . However, providing only one opening  15  reduces the probability that a palm makes contact with film  17 . On the other hand, when a large number of openings  15  are provided, air is introduced also from openings  15  where film  17  is out of contact with a palm and dilutes the perspiration vapor. For these reasons, it is preferable that openings  15  are provided in two positions on the left and right sides in steering wheel  13 . 
     In each of the first and second exemplary embodiments, control circuit  29  determines an alcohol drinking condition based on the alcohol concentrations in perspiration vapor. In addition to the alcohol concentrations, fatigue degrees of the driver may be used for determination. Specifically, line-of-sight detector  61  for detecting the lines of sight of the driver is provided in a place, e.g. the dashboard in front of the driver seat, and connected to control circuit  29 , as shown in the block circuit diagram of  FIG. 14 . In this structure, control circuit  29  detects line-of-sight motion characteristics by line-of-sight detector  61 , and calculates a fatigue degree of the driver based on the line-of-sight motion characteristics. When the fatigue degree is equal to or larger than a predetermined value and the output from the alcohol sensor is equal to or larger than the alcohol drinking regulation value, the driver is determined to be in a heavily drunk condition (first drunk condition). In this case, operations such as giving a stronger drinking alarm or forcedly stopping the vehicle may be performed. The fatigue degree can be obtained by calculating Lyapunov exponent λ expressed by Equation (1), for example: 
     
       
         
           
             
               
                 
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     Lyapunov exponent λ can be obtained as an extremal value when the line-of-sight motion characteristics are set as f(xi) in Equation (1), and modulus of variations (differential values) of the line-of-sight motion characteristics are averaged after logarithmic calculation. When the obtained Lyapunov exponent λ is equal to or larger than a predetermined value, control circuit  29  determines that the driver is tired. 
     Alternatively, weight sensor  62  may be provided in the driver seat in place of line-of-sight detector  61  so that control circuit  29  detects the weight change characteristics based on the output from weight sensor  62 , and calculates the fatigue degree based on the weight change characteristics. Specifically, weight sensors  62  are provided in four corners of the driver seat, for example, and the displacement of the gravity center of the driver is obtained according to the weight change characteristics of each sensor. Calculation of Lyapunov exponent λ thereof can provide a fatigue degree. In such a structure, the driver seat weight sensor for a smart air-bag system can be used as weight sensor  62 . Thus, in a vehicle incorporating a smart air-bag system, an alcohol drinking condition including a fatigue degree can be determined without the need of adding weight sensor  62 . 
     When the fatigue degree obtained by line-of-sight detector  61  or weight sensor  62  described above is equal to or larger than a predetermined value, an alarm about fatigue may be given to the driver to prompt the driver to have a break, even though the diver is not in a drunk condition. Both line-of-sight detector  61  and weight sensor  62  may be provided.  FIG. 14  shows a structure that includes line-of-sight detector  61  or weight sensor  62  added to the structure of  FIG. 3 . However, line-of-sight detector  61  or weight sensor  62  may be added to the structure of  FIG. 12 . 
     In each of the first and second exemplary embodiments, pump  25  sucks the perspiration vapor from opening  15  through film  17 . However, pump  25  is not essential. In the first exemplary embodiment, for example, when alcohol sensors  19 A and  19 B are provided in contact with the edges around openings  15 , and the responsibility of alcohol detection is ensured by the use of a material highly permeable to alcohol vapor or other methods, pump  25  can be eliminated. 
     In the above descriptions, the drunk driving detection system in each of the first and second exemplary embodiments is mainly for a motor vehicle. However, the drunk driving detection system may be used for the applications in which drunk operation gives serious influence, such as a railroad vehicle, an airplane, a marine vessel, construction equipment, and a plant actuator. Thus, the alcohol detection system as described above for a motor vehicle is just one example of particular application and the same can be applied to any other device or object which is controlled or monitored by a human. 
     The drunk driving detection system of the present invention can determine that the driver is in a drunk condition with high accuracy. Thus, the present invention is useful as a drunk driving detection system or the like particularly for private vehicles having a large number of drivers to which less strict control of drunk driving detection is given.