Abstract:
In order to achieve an aspect of the present invention, a rear vehicle detecting apparatus of a vehicle include an alarm unit, a temperature detecting section, a reference temperature data generating section, a comparing section, and a drive section. The temperature detecting section detects a first temperature data based on heat radiated from another vehicle which exists behind the vehicle. The reference temperature data generating section generates a second temperature data as a reference. The comparing section compares the first temperature data and the second temperature data. The driving section drives the alarm unit based on the comparing result by the comparing section.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rear vehicle detecting apparatus, and more particularly to a rear vehicle detecting apparatus of a vehicle which can detect another vehicle following the vehicle from oblique rear in the same direction as the vehicle runs. 
     2. Description of the Related Art 
     Generally, a vehicle such as an automobile runs on a lane indicated on a road, and the driver of the vehicle changes the lane into an adjacent lane based on the running situation. In a case to change the running lane, the driver confirms whether or not another vehicle is running on the adjacent lane, by a rearview mirror such as a door mirror, a room mirror and a fender mirror, and then the driver changes the running lane. 
     Conventionally, the technique is proposed, in which a transmission and reception unit for laser light or millimeter wave is arranged in the front portion of a following vehicle, and the running speed of the following vehicle is decelerated based on an output signal from the transmission and reception unit, when the distance from the following vehicle to a preceding vehicle is smaller than a predetermined value. 
     According to this proposal, when the preceding vehicle and the following vehicle runs on the same lane, the laser from the following vehicle is reflected in the rear of the preceding vehicle, because the rear of the preceding vehicle and the front of the following vehicle oppose. Therefore, it is possible for the reflected laser to be detected by the reception unit arranged in the front of the following vehicle. 
     However, when the preceding vehicle and the following vehicle are running on different lanes, the laser beam reflected by the preceding vehicle can not be sufficiently detected by the reception unit of the following vehicle, because the rear of the preceding vehicle and the front of the following vehicle do not oppose. Therefore, the detection precision of the existence of the preceding vehicle reduces remarkably. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a vehicle with a rear vehicle detecting apparatus for detecting another vehicle running on a different lane. 
     In order to achieve an aspect of the present invention, a rear vehicle detecting apparatus of a vehicle include an alarm unit, a temperature detecting section, a reference temperature data generating section, a comparing section, and a drive section. The temperature detecting section detects a first temperature data based on heat radiated from another vehicle which exists behind the vehicle. The reference temperature data generating section generates a second temperature data as a reference. The comparing section compares the first temperature data and the second temperature data. The driving section drives the alarm unit based on the comparing result by the comparing section. 
     The temperature detecting section preferably includes an optical system collecting the heat radiated from the other vehicle which exists behind the vehicle, an infrared sensor detecting the collected heat by the optical system, and a converting section converting the detected heat into the first temperature data. 
     In this case, when the optical system includes a lens, the temperature detecting section may include a plurality of sets of the lens and the infrared sensor. At this time, the plurality of sets are provided to have different fields of view. 
     Also, the optical system may include a first mirror collecting the heat radiated from the other vehicle which exists behind the vehicle, and a second mirror which reflects the collected heat by the first mirror on the infrared sensor. 
     Further, the optical system may include a prism collecting the heat radiated from the other vehicle on the infrared sensor when the other vehicle exists in different positions relative to the vehicle. 
     The temperature detecting section further includes a drive section driving the optical system and the infrared sensor to orient different fields of view, depending upon time. 
     The rear vehicle detecting apparatus may include two sets of the temperature detecting sections respectively provided in a rear portion of the vehicle on left and right sides. 
     Also, the reference temperature data generating section may include a measuring unit measuring at least an element of whether circumstance of the vehicle, and a generating unit generating the second temperature data based on the measuring result of the measuring unit. 
     When the temperature detecting section includes a plurality of infrared sensors detecting the radiated heat, it is preferable that the comparing section time-divisionally compares the first temperature data and the second temperature data for every infrared sensor. 
     Also, it is preparable that the alarm unit is driven to output an alarm auditorily, and is provided in a front portion of the vehicle. 
     When the temperature detecting section includes at least an infrared sensor, it is preferable that the infrared sensor is of a bolometer type, a pyroelectric type, or a thermopile type. 
     In order to achieve another aspect of the present invention, a vehicle includes a rear vehicle detecting apparatus which includes a heat detecting section provided in a rear portion of the vehicle to detect heat radiated from another vehicle, and an alarm unit provided to output an alarm corresponding to the detecting result by the heat detecting section. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a vehicle with a rear vehicle detecting apparatus of the present invention; 
     FIG. 2 is a block diagram of the rear vehicle detecting apparatus according to a first embodiment of the present invention; 
     FIG. 3 is a circuit diagram of a detecting unit section of the rear vehicle detecting apparatus in the first embodiment; 
     FIG. 4 is a cross sectional view of a rear section of the vehicle with the rear vehicle detecting apparatus in the first embodiment; 
     FIG. 5 is a flow chart to explain the operation of the rear vehicle detecting apparatus according to the first embodiment of the present invention; 
     FIG. 6 is a diagram to explain the operation of the rear vehicle detecting apparatus according to the first embodiment of the present invention; 
     FIG. 7 is a diagram to explain the operation of the rear vehicle detecting apparatus according to a second embodiment of the present invention; 
     FIG. 8 is a diagram illustrating the detecting unit section of the rear vehicle detecting apparatus according to a third embodiment of the present invention; 
     FIG. 9 is a diagram illustrating the detecting unit section of the rear vehicle detecting apparatus according to a fourth embodiment of the present invention; and 
     FIG. 10 is a cross sectional view of the infrared sensor of the rear vehicle detecting apparatus according to a fifth embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, a vehicle with a rear vehicle apparatus of the present invention will be described below in detail with reference to the attached drawings. 
     FIGS. 1 to  4  show the back vehicle detecting apparatus according to the first embodiment of the present invention. 
     Referring to FIG. 1, a vehicle A is provided with tires Bal and Bar on either front side and tires Bbl and Bbr on back either side. Also, referring to FIG. 2, the vehicle A has the rear vehicle detecting apparatus a detecting unit section  1 , an alarm unit  7  and a steering mechanism lock mechanism  9 . The alarm unit  7  may be composed of a buzzer, a lamp, a speaker, or a liquid crystal display. In this embodiment, the alarm unit  7  is a buzzer and provided in dashboard in the front portion of the vehicle A. The steering mechanism restriction mechanism  9  will be described later. 
     The detecting unit section  1  is composed of a left detecting unit  1 L, a right detecting units  1 R, a control section  8 , a circumstance element detecting unit  10 , and a sensor driving section  11 . The left detecting unit  1 L and the right detecting units  1 R are arranged in the rear portion of the vehicle A on either side. The left detecting unit  1 L and the right detecting unit  1 R have substantially the same structure. The control section  8 , the circumstance temperature detecting unit  10 , and the sensor driving section  11  will be described later. 
     The left detecting unit  1 L is composed of an infrared sensor section  2 , a temperature converting section  3 , a reference temperature setting section  4 , a comparing and determining section  5  and a drive circuit  6 . The infrared sensor section  2  detects heat radiated from a vehicle  1 A to generate a heat detection signal. The temperature converting section  3  converts the heat detection signal supplied from the infrared sensor  2  to a data indicative of a detection temperature. The reference temperature setting section  4  outputs a data indicative of a reference temperature. The comparing and determining section  5  compares the detection temperature data supplied from the temperature converting section  3  and the reference temperature data supplied from the reference temperature setting section  4  to determine whether or not the detection temperature is higher than the reference temperature. The drive circuit  6  operates based on the determining result of the comparing and determining section  5  to drive the alarm unit  7  to be described later. 
     The alarm unit  7  is connected to the drive circuit  6  of each detecting unit  1 L and  1 R. It should be noted that the temperature converting section  3 , the reference temperature setting section  4 , and the comparing and determining section  5  in each detecting unit  1 L or  1 R are realized by a CPU and a software. 
     Referring to FIG. 3, the drive circuit  6  in each of the left detecting unit  1 L and the right detecting unit  1 R is composed of a resistance  61  and a transistor  62  as a switching element. The collectors of the transistors  62 R and  62 L in the drive circuits  6 R and  6 L of the left detecting unit  1 L and the right detecting unit  1 R are connected together with the alarm unit  7  such as a buzzer  71 . The outputs of the comparing and determining sections  5 R and  5 L are connected to the bases of the transistors  62 R and  62 L through resistors  61 R and  61 L, respectively. It should be noted that the DC power supply Vcc is supplied to the buzzer  71 . 
     The infrared sensor section  2  ( 2 R,  2 L) in each of the left detecting unit  1 L and the right detecting unit  1 R detects the infrared rays radiated from an engine room and/or a tire of the following vehicle A 1 . For example, the infrared sensor section  2  has a lens  8  and an infrared sensor  12  as a single sensor element or a sensor element array in a sealed container. The inner space of the infrared sensor  12  is set to the vacuum state or filled with a xenon gas. The infrared sensor  12  may be of a cooling type or a non-cooling type. However, the infrared sensor  12  of a non-cooling type bolometer using a resistance change dependent upon temperature is preferable, and such an infrared sensor has the temperature resolution of about 0.1° C. It should be noted that a thermopile-type infrared sensor, which has a low sensitivity, and a pyroelectric type infrared sensor which requires a chopper may be applied as the infrared sensor  12 , in addition to the bolometer type infrared sensor  12 . 
     In the rear vehicle detecting apparatus, the left detecting unit  1 L and the right detecting unit  1 R are arranged to be isolated from each other in the trunk section T in the rear portion of the vehicle A. A 1 so, the alarm unit  7  is arranged in the dashboard section DB in the vehicle A (FIG.  1 ). Especially, the infrared sensor sections  2 R and  2 L of the left detecting unit  1 L and the right detecting unit  1 R are provided to sense the infrared rays through the lenses  8  and holes Ta which are formed on either side of the trunk section T. The infrared sensor  12  is arranged to detect heat collected by the lens  8  from the heat source such as the tire Bar of the following vehicle A 1  which exists obliquely behind the vehicle A on the left side. A 1 so, the infrared sensor section  2 R of the right detecting unit  1 R is arranged to detect the heat source such as the tire Bal of the following vehicle which exists obliquely behind the vehicle A on the right side. It should be noted that relatively dry air is flowed out from the hole Ta of the trunk section T to prevent moisture from being adhered on the infrared sensor  2  and the lens  8 , as shown in FIG. 4 by the arrows. 
     Next, the operation of the rear vehicle detecting apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 5 and 6. 
     In FIG. 6, it is supposed that the preceding vehicle A is running on a running lane Ra and the following vehicle A 1  is running on a passing lane Rb in the direction indicated by the arrow. The left detecting unit  1 L and the right detecting unit  1 R are arranged in the respective rear portions of the preceding vehicle A. The infrared sensor section  2  of the right detecting unit  1 R detects heat radiated from the tire Bar of the following vehicle A 1  which exists obliquely behind the vehicle A on the right side (Step S 1  in FIG.  5 ). The temperature converting section  3  converts the heat detection signal outputted from the infrared sensor  2  into the detection temperature data (Step S 2 ) to output to the comparison and at determining section  5 . On the other hand, the reference temperature data is supplied from the reference temperature setting section  4  to the comparing and determining section  5 . The reference temperature is desirably changed based on external environment, because the temperature of the tire depends on the season, the weather, and an ambience temperature. For this purpose, the reference temperature setting section  4  is connected with the circumstance element detecting unit  10 . The circumstance element detecting unit  10  is a thermometer or an ombroscope in this embodiment to measure a circumstance temperature or a rain amount as a circumstance element. The reference temperature setting section  4  determines the reference temperature based on the measuring result by the circumstance element detecting unit  10 . Thus, the reference temperature is automatically changed. 
     The comparing and determining section  5  compares the detection temperature data from the infrared sensor section  2  and the reference temperature data from the reference temperature setting section  4  to determine whether or not the detection temperature is higher than the reference temperature (Step S 3 ). The following vehicle A 1  is determined to exist obliquely behind the preceding vehicle A on the right side when the detection temperature is determined to be higher than the reference temperature. Also, the following vehicle A 1  is determined not to exist obliquely behind the preceding vehicle A on the right side when the detection temperature is determined to be lower than the reference setting temperature. 
     Especially, when a signal is outputted from the comparing and determining section  5  to indicate that the following vehicle A 1  is determined to exist obliquely behind the preceding vehicle A on the right side (Step S 4 ), the signal is given to the base of the transistor  62  through the resistance  61  of the drive circuit  6 . The transistor  62  of the drive circuit  6  is set to the ON state in response to the signal. In this way, it is auditorily notified to the driver P through the operation of the buzzer  71  that the other vehicle exists on the passing lane Rb, because the power supply Vcc is supplied to the buzzer  71  of the alarm unit  7 . 
     Also, when the following vehicle A 1  is determined by the comparing and determining section  5  not to exist obliquely behind the preceding vehicle A on the right side (Step S 5 ), the drive circuit  6  is kept in an off state. Therefore, the alarm unit  7  is not driven and the buzzer  71  in the dashboard section DB does not generate any sound. Therefore, the driver can recognize that change of the lane is possible. 
     When the preceding vehicle A changes the lane from the passing lane Rb into the running lane Ra, whether or not the following vehicle A 1  exists on the running lane Ra is detected by the left detecting unit  1 L, and the similar operation is carried out. 
     According to the first embodiment, the existence or non-existence of the following vehicle can be detected based on the existence or non-existence of the radiation heat by the left detecting unit  1 L or the right detecting unit  1 R of the detecting unit  1 , even when the existence of the following vehicle can not be confirmed because of the blind spot of the rearview mirror in case of change of the lane. Therefore, the propriety of the lane change can be accurately determined. 
     Especially, because the alarm unit  7  is the buzzer  71 , it can be auditorily notified by buzzer  71  that the following vehicle exists and the lane change is improper. 
     Also, because the infrared sensor section  2  of the detecting unit section  1 , i.e., the left detecting unit  1 L or the right detecting unit  1 R is arranged in such a manner that the tire Bar or Bal of the following vehicle whose temperature rises due to the high-speed rotation, is in the rear field of view, the signal-noise ratio to the background temperature can be taken high. Thus, it is possible to improve in the precision and reliability of the detection of the following vehicle. 
     FIG. 7 shows the rear vehicle detecting apparatus according to the second embodiment of the present invention. The rear vehicle detecting apparatus in the second embodiment is basically the same as the first embodiment. The different point is that a plurality of sets of lens and infrared sensor are provided in the infrared sensor section  2  for the left detecting unit  1 L and the right detecting unit  1 R which are arranged on the either rear side of the preceding vehicle A, as shown in FIG.  8 . For example, when the infrared sensor section  2  is composed of three infrared sensors  12 - 1  to  12 - 3 , the infrared sensor  12 - 1  to  12 - 3  are arranged to have different fields of view B 1  to B 3 . 
     The rear vehicle detecting apparatus operates as follows. That is, it is supposed that the preceding vehicle A runs on the running lane Ra and the following vehicle A 1  runs on the passing lane Rb. When the preceding vehicle A changes the lane from the running lane into the passing lane Rb, the confirmation of the existence or non-existence of the following vehicle is carried out. At this time, the existence or non-existence of the following vehicle A 1  obliquely behind the vehicle A on the right side is detected by the infrared sensor section  2  of the right detecting unit  1 R of the preceding vehicle A. When the existence of the following vehicle A 1  is roughly confirmed by the first infrared sensor  12 - 1  as shown by the dotted line, it is informed that the following vehicle A 1  has a considerable long interval from the vehicle A so that it is possible to change the lane. Also, when the existence of the following vehicle A 1  is confirmed by the second and third infrared sensors  12 - 2  and  12 - 3  as shown by the solid line, it is informed that the following vehicle A 1  is approaching the vehicle A so that it is impossible to change the lane. 
     According to the second embodiment, the distance from the vehicle A to the following vehicle A 1  can be finely detected. 
     In the rear vehicle detecting apparatus in the third embodiment, a single infrared sensor  12  and a prism  25  in place of the lens  8  may be used to produce a plurality of fields of view B 1  to B 3 . In this case, it is possible to compare the detected temperature of the heat source for each of the fields of view B 1  to B 3  with the reference temperature. 
     Also, in the rear vehicle detecting apparatus in the fourth embodiment, each detecting unit  1 R or  1 L may be composed of a single infrared sensor  12  and the sensor driving section  11  (FIG.  2 ). In this case, the infrared sensor  12  is scanned in the fields of view B 1  to B 3  for every predetermined time, to collect heat from the heat source. Thus, it is possible to compare the detected temperature in each of the fields of view B 1  to B 3  with the reference temperature. 
     According to the fourth embodiment, when the scanning time is set suitably, it is possible to determine the approaching speed of the following vehicle A 1  to the preceding vehicle A. 
     FIG. 10 shows a rear detecting apparatus according to the fifth embodiment of the present invention. Referring to FIG. 10, the radiated heat from the heat source is collected on a sub-mirror  22  by a parabolic main mirror  21 , and then is incident to the infrared sensor  2  through an opening formed in the center of the main mirror  21 . 
     According to the fifth embodiment, the heat collection to the infrared sensor  12  can be efficiently performed and the detection precision of the following vehicle can be improved. 
     It should be noted that the present invention is not limited by the above embodiments. For example, the whole detecting unit section may be arranged in the vehicle rear portion, or only the infrared sensor of the detecting unit section may be arranged in the vehicle rear portion. In this case, the other components of the detecting unit section may be distributed in the car indoors. 
     Also, when a plurality of infrared sensors are used, the infrared sensors may be arranged in storage sections such as a stoplight, a car spoke light, a backlight in the rear, in addition to the trunk section, or may be arranged in any sections such as a bumper. 
     Also, the detection of the rear vehicle by the infrared sensor may be performed using the infrared rays which are radiated from the components other than the tire of the following vehicle A 1 . 
     Also, the heat collecting mechanism to the infrared sensor may be an off-axis method, a Newton method, or a Nasmith method. 
     Also, the steering system of the vehicle A may be controlled based on the detection result of the following vehicle A 1 . That is, the control section ( 8 ) calculated the data supplied from the comparing and determining section  5  and controls the steering mechanism restriction mechanism  9  (FIG. 2) based on the calculating result such that the vehicle A is not turned to the right direction. 
     Moreover, as the alarm unit  7 , a visual technique such as a lamp and a liquid crystal panels may be applied in place of or in addition to the auditory technique such as the buzzer and the speaker. When the alarm unit  7  is changed from the buzzer or speaker into the lamp and/or the liquid crystal panel, the drive circuits  6 R and  6 L are changed in accordance with the change of the alarm unit. 
     As described above, according to the present invention, the existence of the heat source can be detected by the left detecting unit or the right detecting unit of the detecting unit, even when the existence of the following vehicle on an adjacent lane can not be confirmed by the blind spot of the rearview mirror change. Therefore, the existence of the following vehicle can be accurately determined. 
     Also, if the infrared sensor is arranged in such a manner that the tire of the following vehicle which has been risen in the temperature because of the high-speed rotation is in the rear eyesight of the infrared sensor in the left detecting unit or the right detecting unit of the detecting unit, it is possible to increase a signal-noise ratio to the background temperature. In this way, the existence or non-existence of the following vehicle can be precisely detected.