JP7626008B2 - In-vehicle camera - Google Patents

Description

The present invention relates to an in-vehicle camera. Specifically, the present invention relates to an in-vehicle camera that can increase the normal operating time of the in-vehicle camera by shortening the time required for the in-vehicle camera to resume operation after being stopped while reducing failures caused by temperature rise in the in-vehicle camera.

In vehicle-mounted cameras used for vehicle control, etc., problems may occur when the temperature of the vehicle-mounted camera rises above the guaranteed operating temperature due to, for example, the environment outside the vehicle (e.g., temperature and solar radiation, etc.) and/or heat generated during operation (self-heating), causing the vehicle-mounted camera to break down. To reduce such problems, there is known technology that stops the vehicle-mounted camera by turning off the power when the temperature of the vehicle-mounted camera exceeds a predetermined threshold (see, for example, Patent Document 1 and Patent Document 2).

In the above-mentioned conventional technology, it is known that the on-board camera is restored (the power supply of the on-board camera is turned on (ON)) when it is detected that the on-board camera has cooled down to a temperature below a predetermined threshold (for example, see Patent Document 1). In this case, the power supply of the on-board camera is off when the on-board camera is restored, so the temperature of the on-board camera itself cannot be detected. Therefore, the temperature of the on-board camera is estimated based on the elapsed time since the on-board camera was stopped, the speed of the vehicle on which the on-board camera is mounted (vehicle speed), and vehicle information such as the outside temperature of the vehicle, and the on-board camera is restored when it is determined that the temperature has dropped to a predetermined threshold or lower. In this way, when the on-board camera is restored, the temperature of the on-board camera estimated based on the vehicle information, etc., rather than the temperature of the on-board camera that is actually detected, is used, so it is necessary to set the threshold low in consideration of the estimation accuracy. As a result, the period required from turning the on-board camera off to turning it on again (from stopping the on-board camera to restoring it) becomes longer, and there is a risk that the normal operating time of the on-board camera becomes excessively short.

However, when the temperature threshold (stop temperature) of the on-board camera when the power of the on-board camera is turned off is the same as the temperature threshold (return temperature) of the on-board camera when the power of the on-board camera is turned on (without hysteresis control), the on-board camera is frequently switched on and off (the on-board camera is frequently stopped and turned on). In the technical field, it is common to set the return temperature lower than the stop temperature (performing hysteresis control) in order to reduce such problems. As illustrated in FIG. 5, by performing hysteresis control, the period during which the on-board camera is switched on and off (the on-board camera is repeatedly stopped and turned on) can be made longer than the case in which the hysteresis control illustrated in FIG. 4 is not performed (see the thick double arrow). However, the lower the temperature threshold for the dash cam when turning it on is set in this way, the longer the period required to turn the dash cam back on after it has been turned off (from stopping the dash cam to restarting it), and the greater the risk that the normal operating time of the dash cam will become excessively short.

As described above, there is a demand in this technical field for a technology that can reduce failures caused by temperature rises in the dashcam while shortening the time it takes for the dashcam to resume operation after being stopped, thereby increasing the normal operating time of the dashcam.

JP 2006-151301 A JP 2020-191575 A

As mentioned above, there is a demand in this technical field for a technology that can reduce failures caused by temperature rises in the dashcam while shortening the time it takes for the dashcam to resume operation after being stopped, thereby increasing the normal operating time of the dashcam.

Therefore, as a result of extensive research, the inventors have discovered that the above problem can be solved by continuing to detect the temperature of the onboard camera even when the onboard camera's function is stopped or restricted due to a rise in temperature of the onboard camera, and by appropriately changing the threshold value (return temperature) for restoring the onboard camera's function in accordance with parameters such as vehicle speed.

Specifically, the vehicle-mounted camera according to the present invention (hereinafter, sometimes referred to as the "camera of the present invention") is an on-board camera mounted on a vehicle to capture images of the exterior of the vehicle, and includes an imaging means, a temperature detection means for detecting the internal temperature of the on-board camera, a vehicle speed detection means for detecting the speed of the vehicle on which the on-board camera is mounted, and a control means for controlling the operating state of the on-board camera. The control means is configured to stop or limit the function of the on-board camera when the internal temperature of the on-board camera is higher than a first temperature, which is a predetermined threshold value.

The temperature detection means is configured to detect the internal temperature of the vehicle-mounted camera even when the function of the vehicle-mounted camera is stopped or restricted by the control means. The vehicle speed detection means is configured to detect the vehicle speed even when the function of the vehicle-mounted camera is stopped or restricted by the control means. Furthermore, the control means is configured to release the stop or restriction of the function of the vehicle-mounted camera when the internal temperature of the vehicle-mounted camera is equal to or lower than a second temperature that is a predetermined threshold lower than the first temperature. In addition, the second temperature is changed based on a vehicle parameter that is a parameter including at least the vehicle speed so that the higher the efficiency of heat dissipation from the vehicle-mounted camera, the closer it is to the first temperature.

As described above, in the camera of the present invention, the second temperature (restore temperature), which is the internal temperature threshold when the suspension or restriction of the vehicle-mounted camera's functions is released (the vehicle-mounted camera is restored), is changed so that it becomes higher as the heat dissipation efficiency from the vehicle-mounted camera increases. Therefore, with the camera of the present invention, it is possible to reduce malfunctions caused by temperature rises in the vehicle-mounted camera while shortening the period required for the vehicle-mounted camera to resume operation from being suspended, thereby increasing the normal operating time of the vehicle-mounted camera.

Other objects, features and associated advantages of the present invention will be readily understood from the description of the embodiments of the present invention described below with reference to the drawings.

4 is a schematic graph illustrating the relationship between the heat transfer coefficient of a windshield and vehicle speed. 5 is a schematic graph illustrating the change in the internal temperature of the vehicle-mounted camera according to the present invention (the camera of the present invention) depending on the vehicle speed and the return temperature (second temperature); 5 is a flowchart illustrating the flow of each process included in an internal temperature control routine executed in the camera of the present invention. 11 is a schematic graph showing a change in internal temperature when hysteresis control is not performed and stopping and starting of the vehicle-mounted camera is frequently repeated. 11 is a schematic graph showing a change in internal temperature when hysteresis control is performed and the period during which the vehicle-mounted camera is repeatedly stopped and restarted becomes long.

The vehicle-mounted camera according to the present invention (the camera of the present invention) will be described in detail below with reference to the drawings.

As mentioned above, in conventional vehicle-mounted cameras (hereinafter sometimes referred to as "conventional cameras"), the vehicle-mounted camera is turned back on when the temperature of the vehicle-mounted camera estimated based on vehicle information, etc., rather than the temperature actually detected by the vehicle-mounted camera, falls below a predetermined threshold. For this reason, the threshold is set low in consideration of the accuracy of the estimation of the vehicle-mounted camera temperature, which may lengthen the period required to turn the vehicle-mounted camera back on after it is stopped, resulting in a risk of the normal operating time of the vehicle-mounted camera becoming excessively short. Furthermore, this tendency is more pronounced when hysteresis control is performed.

On the other hand, as described above, the camera of the present invention is an on-board camera that is mounted on a vehicle and captures images of the outside of the vehicle. Such on-board cameras capture images of the front and/or surroundings of the vehicle, for example, and the images are used for various vehicle controls, such as collision avoidance. Typically, the camera of the present invention is attached near the upper end of the inside (cabin side) of the vehicle's windshield, like a conventional camera, and captures images centered on the front of the vehicle. However, the mounting position of the on-board camera is not limited to the above, and is not particularly limited as long as it is a location where it is possible to obtain the effect of increasing cooling efficiency as the vehicle speed increases, as described below.

The camera of the present invention comprises an imaging means, a temperature detection means for detecting the internal temperature of the vehicle-mounted camera, a vehicle speed detection means for detecting the speed of the vehicle on which the vehicle-mounted camera is mounted, and a control means for controlling the operating state of the vehicle-mounted camera. The imaging means is not particularly limited as long as it is capable of capturing images that can be used for the intended purpose, such as the vehicle control described above. Specific examples of the imaging means include digital cameras that use a CCD (Charged Couples Device) or CMOS (Complementary Metal Oxide Semiconductor) as an imaging element.

The temperature detection means is not particularly limited as long as it is capable of detecting the internal temperature of the vehicle-mounted camera, and may be, for example, a thermocouple or other device that is widely used in the relevant technical field. Furthermore, the internal temperature of the vehicle-mounted camera may be any temperature that correlates with the temperature of a component of the vehicle-mounted camera that may be damaged by an increase in temperature, and is not limited to the temperature at a specific location of the vehicle-mounted camera. Specifically, the internal temperature of the vehicle-mounted camera means, for example, the temperature of the IC chip and/or circuit board contained inside the vehicle-mounted camera, the surface temperature of the housing of the vehicle-mounted camera, and the air temperature inside the vehicle-mounted camera.

The vehicle speed detection means is not particularly limited as long as it is capable of detecting the speed of the vehicle on which the vehicle-mounted camera is mounted, but a vehicle speed sensor that is commonly used for various control purposes in automobiles can be used as the vehicle speed detection means.

The control means is configured to stop or limit the function of the vehicle-mounted camera when the internal temperature of the vehicle-mounted camera is higher than a first temperature, which is a predetermined threshold. The function as such a control means can be realized, for example, by an electronic control unit (ECU: Electric Control Unit) equipped in the vehicle-mounted camera. The ECU has a microcomputer as its main part, and is equipped with an input port for receiving detection signals from components such as the temperature detection means and an output port for sending instruction signals to components such as the power supply unit of the vehicle-mounted camera. The microcomputer includes, for example, a CPU and a data storage device such as a ROM and a RAM. The CPU is configured to realize various functions by receiving various detection signals, executing various arithmetic processing, and sending various instruction signals based on instructions (programs) stored in the ROM. The ECU can thus realize the function as a control means.

The first temperature corresponds to the internal temperature of the vehicle-mounted camera detected by the temperature detection means when the temperature of a component of the vehicle-mounted camera that may fail due to a temperature rise exceeds the guaranteed operating temperature. The first temperature can be determined appropriately, for example, taking into consideration a detection error by the temperature detection means and/or a further temperature rise during the period required for the control means to stop or limit the functions of the vehicle-mounted camera.

The stop or restriction of the functions of the vehicle camera by the control means is not necessarily limited to the stop or restriction of all functions of the vehicle camera, so long as it is possible to reduce further heat generation inside the vehicle camera. In other words, the functions of the vehicle camera stopped or restricted by the control means may be some of the functions of the components of the vehicle camera, such as those that are likely to break down due to temperature rise and/or those that generate a large amount of heat during operation. In addition, the stop or restriction of the functions of the vehicle camera by the control means is not necessarily limited to the stop by, for example, cutting off the power supply to all or some of the components of the vehicle camera, so long as it is possible to reduce further heat generation inside the vehicle camera. In other words, the stop or restriction of the functions of the vehicle camera by the control means also includes, for example, reducing the processing by changing the operating mode of all or some of the components of the vehicle camera, reducing the load on all or some of the components of the vehicle camera, etc.

However, in the camera of the present invention, the temperature detection means is configured to detect the internal temperature of the vehicle-mounted camera even when the functions of the vehicle-mounted camera are stopped or restricted by the control means. As a result, in the camera of the present invention, the suspension or restriction of the functions of the vehicle-mounted camera can be released (the vehicle-mounted camera can be restored) based on the internal temperature of the vehicle-mounted camera actually detected by the temperature detection means, rather than the internal temperature of the vehicle-mounted camera estimated based on vehicle information, etc., as in the conventional camera described above.

That is, in the camera of the present invention, the control means is configured to release the suspension or restriction of the functions of the vehicle-mounted camera when the internal temperature of the vehicle-mounted camera is equal to or lower than the second temperature, which is a predetermined threshold lower than the first temperature. That is, in the camera of the present invention, hysteresis control is performed. The second temperature is set to a temperature lower than the first temperature so that the suspension or restriction of the functions of the vehicle-mounted camera and the release of the suspension or restriction are not frequently switched (the suspension and recovery of the vehicle-mounted camera are not frequently repeated). In other words, the second temperature is set to a temperature lower than the first temperature so that the internal temperature of the vehicle-mounted camera can remain in a range equal to or lower than the first temperature for a sufficiently long period of time even if the suspension or restriction of the functions of the vehicle-mounted camera is released at that time and the rise in the internal temperature of the vehicle-mounted camera resumes.

As mentioned above, the onboard camera is typically mounted near the upper end of the inside (cabin side) of the vehicle's windshield. As the vehicle speed increases, the amount of heat dissipated from the windshield due to contact with the air in front of the vehicle increases, so as shown in Figure 1, the heat dissipation efficiency (heat transfer rate) from the windshield increases as the vehicle speed increases. Therefore, the heat dissipation efficiency from the onboard camera via the windshield and/or the air in the cabin around the windshield also increases as the vehicle speed increases.

As a result of the above, as shown in FIG. 2(a), the rate at which the internal temperature of the dashcam decreases during the period after the internal temperature of the dashcam becomes higher than the first temperature (stop temperature) and the dashcam's functions are stopped or restricted (the dashcam is stopped) is higher when the vehicle speed is high (high speed) than when the vehicle speed is low (low speed). Therefore, if the same second temperature (return temperature) is set for both low and high speeds, the timing at which the internal temperature of the dashcam falls below the second temperature (return temperature) and the stop or restriction of the dashcam's functions is lifted (the dashcam returns) is earlier when the vehicle speed is high (high speed) than when the vehicle speed is low (low speed) (see the open arrow).

Furthermore, as shown in FIG. 2(a), the rate at which the internal temperature of the dashcam rises after recovery is slower when the vehicle speed is high (high speed) than when it is low (low speed). Therefore, if the same second temperature (return temperature) is set for both low and high speeds, the timing at which the internal temperature of the dashcam rises above the first temperature (stop temperature) again and the functions of the dashcam are stopped or restricted again (the dashcam is stopped again) will be later when the vehicle speed is high (high speed) than when it is low (low speed). In this way, the normal operating time of the dashcam can be ensured longer when the vehicle speed is high (high speed) than when it is low (low speed).

In particular, in the graph shown in FIG. 2A, after time Tr (see black circle), the difference between the internal temperature of the dash-camera and the first temperature (stop temperature) becomes larger when the vehicle speed is high (high speed) than when the vehicle speed is low (low speed). In other words, if the same second temperature (return temperature) is set for both low and high speeds, the internal temperature of the dash-camera when the vehicle speed is high (high speed) is kept excessively low relative to the first temperature (stop temperature) compared to when the vehicle speed is low (low speed). In other words, in consideration of the rate at which the internal temperature of the dash-camera rises when the vehicle speed is high (high speed), it can be said that the same second temperature (return temperature) as when the vehicle speed is low (low speed) is too low. In other words, when the vehicle speed is high (high speed), even if the second temperature (return temperature) is set higher than when the vehicle speed is low, the length of the period (normal operating time) until the internal temperature of the dashcam again exceeds the first temperature (stop temperature) and the functions of the dashcam are stopped or restricted (the dashcam is stopped) can be maintained at least as long as when the vehicle speed is low (low speed).

Therefore, in the camera of the present invention, the second temperature is changed based on vehicle parameters, which are parameters including at least the vehicle speed, so that the higher the heat dissipation efficiency from the vehicle-mounted camera, the closer it becomes to the first temperature. As described above, the vehicle-mounted camera is typically attached near the upper end of the inside (cabin side) of the vehicle's windshield, so the higher the vehicle speed, the higher the heat dissipation efficiency from the vehicle-mounted camera via the windshield and/or the air in the cabin around the windshield. Therefore, in the camera of the present invention, the higher the vehicle speed, the closer the second temperature (return temperature) is set to a temperature.

2(b) is a schematic graph showing the transition of the internal temperature of the camera of the present invention when the vehicle speed is low (low speed) and when the vehicle speed is high (high speed). In the camera of the present invention, the second temperature at high speed is set to a temperature closer to (higher than) the first temperature than the second temperature (return temperature) at low speed as described above (see the black arrow). Therefore, the timing at which the internal temperature of the camera of the present invention becomes equal to or lower than the second temperature and the stop or restriction of the function of the camera of the present invention is released (the camera of the present invention returns) becomes earlier at high speed than at low speed (see the open arrow). As a result, the timing at which the camera of the present invention returns becomes earlier at high speed than when the same second temperature is set at low speed and high speed as shown in FIG. 2(a) (see the solid double arrow). In this way, according to the camera of the present invention, it is possible to reduce the failure caused by the temperature rise of the vehicle-mounted camera, while shortening the period required for the vehicle-mounted camera to return from being stopped, thereby increasing the normal operating time of the vehicle-mounted camera.

The above-mentioned "vehicle parameters" may be only the vehicle speed, or may further include other parameters that affect the heat dissipation efficiency from the vehicle-mounted camera in addition to the vehicle speed. Specific examples of such other parameters include the outside air temperature of the vehicle. Naturally, the lower the outside air temperature of the vehicle, the higher the heat dissipation efficiency from the vehicle-mounted camera via the windshield and/or the air in the passenger compartment around the windshield. Therefore, the camera of the present invention may further include an outside air temperature detection means for detecting the outside air temperature of the vehicle, and may not only change the second temperature (return temperature) so that it approaches the first temperature (stop temperature) as the vehicle speed increases, but also change the second temperature (return temperature) so that it approaches the first temperature (stop temperature) as the vehicle outside air temperature decreases.

The speed of the vehicle on which the camera of the present invention is mounted may be the average vehicle speed over a predetermined period of time. In the case where the outside air temperature of the vehicle is also used as a vehicle parameter as described above, the average outside air temperature over a predetermined period of time may be used.

The above-mentioned correspondence between the vehicle parameters and the second temperature (return temperature) can be stored in a data storage device such as a ROM constituting the control means as a two-dimensional data map of a combination of a plurality of second temperatures (return temperatures) corresponding to each range of the vehicle speed divided into a plurality of ranges. In the case where the outside air temperature of the vehicle is also used as a vehicle parameter as described above, the correspondence between the vehicle parameters and the second temperature (return temperature) can be stored in a data storage device such as a ROM constituting the control means as a three-dimensional data map of a combination of a plurality of second temperatures (return temperatures) corresponding to each combination of the vehicle speed divided into a plurality of ranges and the outside air temperature divided into a plurality of ranges. Alternatively, the correspondence between the vehicle parameters and the second temperature (return temperature) can be stored in a data storage device such as a ROM constituting the control means as a function (calculation formula) with vehicle parameters such as the vehicle speed or a combination of the vehicle speed and the outside air temperature as variables.

The operation of the camera of the present invention will now be described in detail with reference to FIG. 3. FIG. 3 is a flow chart showing an example of the flow of each process included in the internal temperature control routine executed in the camera of the present invention. When the power supply of the camera of the present invention is turned on (ON) and normal operation as an in-vehicle camera is started, the control routine is repeatedly executed at predetermined time intervals by the CPU constituting the control means in accordance with a program stored in a data storage device such as a ROM constituting the control means. Note that the following explanation will be given for the case where the vehicle speed is used as a vehicle parameter that serves as an index for changing the second temperature (return temperature).

When the control routine is started, first in step S01, the internal temperature T of the camera of the present invention is acquired by the temperature detection means. Next, in step S02, it is determined whether the internal temperature T is higher than a first temperature (stop temperature) T1. If the internal temperature T is equal to or lower than the first temperature T1, the determination in step S02 is "No" and processing proceeds to step S09, where normal operation as an in-vehicle camera continues. On the other hand, if the internal temperature T is higher than the first temperature T1, the determination in step S02 is "Yes" and processing proceeds to the next step S03, where the function of the in-vehicle camera is stopped or restricted.

When the function of the vehicle-mounted camera is stopped or restricted in step S03 as described above, the process proceeds to the next step S04, where the vehicle speed V of the vehicle on which the camera of the present invention is mounted is acquired by the vehicle speed detection means. Next, in step S05, the second temperature (return temperature) T2 is determined based on the vehicle speed V as the vehicle parameter described above. Specifically, as described above, the second temperature T2 is identified or calculated by the CPU constituting the control means based on a data map or function stored in a data storage device such as a ROM constituting the control means.

Next, the process proceeds to step S06, where the internal temperature T of the camera of the present invention is acquired again by the temperature detection means. Then, in the next step S07, it is determined whether the internal temperature T is equal to or lower than the second temperature T2. If the internal temperature T is higher than the second temperature T2, the determination is "No" in step S07, the process returns to the above-mentioned step S04, the vehicle speed V of the vehicle is acquired again by the vehicle speed detection means, and the process from step S05 onwards is repeated. On the other hand, if the internal temperature T is equal to or lower than the second temperature T2, the determination is "Yes" in step S07, the process proceeds to the next step S08, where the suspension or restriction of the functions of the in-vehicle camera is lifted (normal operation of the camera of the present invention is resumed). Then, the process proceeds to the next step S09, where normal operation as an in-vehicle camera continues.

As described above, in the camera of the present invention, the second temperature (restore temperature), which is the internal temperature threshold when the suspension or restriction of the vehicle-mounted camera's functions is released (the vehicle-mounted camera is restored), is changed so that it becomes higher as the heat dissipation efficiency from the vehicle-mounted camera increases. Therefore, with the camera of the present invention, it is possible to reduce malfunctions caused by temperature rises in the vehicle-mounted camera while shortening the period required for the vehicle-mounted camera to resume operation from being suspended, thereby increasing the normal operating time of the vehicle-mounted camera.

The demand to increase normal operation time by shortening the time required to restore functions after being stopped or restricted while reducing failures caused by temperature rises associated with operation is not limited to in-vehicle cameras, but is common to a variety of in-vehicle devices that may experience problems such as failures due to temperature rises caused by the external environment and/or self-heating. In other words, the present invention can be applied not only to in-vehicle cameras, but also to a variety of in-vehicle devices for which similar demands exist.

For the purpose of explaining the present invention, several embodiments having specific configurations have been described with reference to the attached drawings. However, the scope of the present invention should not be construed as being limited to these exemplary embodiments, and it goes without saying that appropriate modifications can be made within the scope of the claims and the matters described in the specification.

Claims (1)

The vehicle-mounted camera includes an imaging means, a temperature detection means for detecting an internal temperature of the vehicle-mounted camera, a vehicle speed detection means for detecting a vehicle speed of the vehicle on which the vehicle-mounted camera is mounted, and a control means for controlling an operating state of the vehicle-mounted camera,
The control means is configured to stop or limit a function of the vehicle-mounted camera when the internal temperature is higher than a first temperature that is a predetermined threshold value,
An in-vehicle camera mounted on a vehicle to capture an image of an exterior of the vehicle,
The temperature detection means is configured to detect the internal temperature even when the function of the vehicle-mounted camera is stopped or limited by the control means,
The vehicle speed detection means is configured to detect the vehicle speed even when the function of the vehicle-mounted camera is stopped or restricted by the control means,
The control means is configured to release the suspension or restriction of the function of the vehicle-mounted camera when the internal temperature is equal to or lower than a second temperature that is a predetermined threshold lower than the first temperature,
The second temperature is changed so as to approach the first temperature as the vehicle speed increases.
The in-vehicle camera is characterized by the above.

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