In-vehicle device and control method for the in-vehicle device

Abstract

To provide an in-vehicle device and a control method for the in-vehicle device that can improve the accuracy of detecting the fan rotation speed. [Solution] The in-vehicle device according to the embodiment comprises a fan, a pulse detection unit, a switch, a controller, and a timer unit. The pulse detection unit detects pulses output each time the fan rotates. The switch is provided on the control line through which pulses are input from the fan to the pulse detection unit, and connects or disconnects the control line. The controller calculates the fan speed based on the number of pulses detected by the pulse detection unit within a certain period of time. The timer unit counts for a certain period of time according to the controller's instructions. The switch connects the control line when the timer unit starts counting for a certain period of time, and disconnects the control line when the timer unit finishes counting for a certain period of time. After the control line is disconnected by the switch, the controller obtains the number of pulses from the pulse detection unit and calculates the rotation speed.

Description

Technical Field

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[0001] The present invention relates to an in-vehicle device and a control method for an in-vehicle device.

Background Art

[0002] Conventionally, an in-vehicle device incorporating a fan for cooling the interior of a housing has been known (see, for example, Patent Document 1). Patent Document 1 discloses a technique for detecting the rotational speed of a fan and controlling the rotational speed of the fan in real time according to the detected rotational speed to maintain it at a target rotational speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, for example, in the case of an in-vehicle device equipped with a control circuit specialized for video processing, such as a drive recorder, since the control circuit is not good at real-time control, there is a possibility that the rotational speed of the fan cannot be accurately detected. Specifically, in Patent Document 1, when detecting the rotational speed of a fan, the number of pulses output each time the fan rotates is measured for a certain period of time, and the rotational speed is detected based on the measured number of pulses. Since the detection circuit for detecting the number of pulses always measures the number of pulses by counting up, it is necessary to accurately read the number of pulses at the timing when a certain period of time has elapsed. However, if the control circuit is not good at real-time control, there is a possibility that the read timing will vary. That is, since the time from the end of the count for a certain period of time to the reading of the number of pulses varies, the accuracy of the read number of pulses may decrease. For this reason, in the prior art, there is a possibility that the detection accuracy of the rotational speed of the fan may decrease due to the decrease in the accuracy of the read number of pulses.

[0005] The present invention has been made in view of the above, and aims to provide an in-vehicle device and a control method for the in-vehicle device that can improve the accuracy of detecting the rotation speed of a fan. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, the in-vehicle device according to the present invention comprises a fan, a pulse detection unit, a switch, a controller, and a timer unit. The pulse detection unit detects pulses output each time the fan rotates. The switch is provided on the control line through which the pulses are input from the fan to the pulse detection unit, and connects or disconnects the control line. The controller calculates the rotation speed of the fan based on the number of pulses detected by the pulse detection unit within a certain period of time. The timer unit counts the time period as instructed by the controller. The switch connects the control line when the timer unit starts counting the time period, and disconnects the control line when the timer unit finishes counting the time period. After the control line is disconnected by the switch, the controller obtains the number of pulses from the pulse detection unit and calculates the rotation speed. [Effects of the Invention]

[0007] According to the present invention, when a count for a certain period of time is started, a control line is connected by a switch, and when the count for the certain period of time is finished, the control line is disconnected, so that the pulse detection unit can detect pulses only during the period that the timer unit is counting. Furthermore, in the present invention, the number of pulses is obtained from the pulse detection unit after the switch is disconnected, that is, at a timing when the number of pulses detected by the pulse detection unit does not change. As a result, even if the timing at which the controller obtains the number of pulses from the pulse detection unit varies, the number of pulses does not change, thus reducing the decrease in accuracy of the pulse count. In other words, according to the present invention, even if the controller is not adept at real-time control, the accuracy of detecting the fan rotation speed can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the configuration and operation of a drive recorder according to an embodiment. [Figure 2] Figure 2 is a timing chart of the dashcam's operation. [Figure 3] Figure 3 shows an example of the configuration and operation of a modified drive recorder. [Figure 4] Figure 4 shows a partial example of the configuration of a modified drive recorder. [Modes for carrying out the invention]

[0009] The in-vehicle device and control method of the in-vehicle device according to the embodiment will be described in detail below with reference to the attached drawings. However, the present invention is not limited to the embodiments shown below. In the following, a drive recorder will be given as an example of an in-vehicle device. However, the in-vehicle device is not limited to a drive recorder, and any in-vehicle device whose main processing is video processing may be used.

[0010] First, an example of the configuration and operation of the drive recorder according to the embodiment will be described using Figure 1. Figure 1 is a diagram showing an example of the configuration and operation of the drive recorder 1 according to the embodiment. Note that, for the sake of explanation, some of the components of the drive recorder 1 (for example, the camera, etc.) are omitted in Figure 1.

[0011] First, let's describe an example configuration of drive recorder 1. As shown in Figure 1, drive recorder 1 comprises an SoC (System on Chip) 2, a cooling fan 3, a switch 4, and a pulse detection unit 5.

[0012] SoC2 is a circuit board on which semiconductors necessary for the operation of the drive recorder 1 are mounted. The SoC2 comprises a controller 21 and a timer unit 22. The controller 21 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various circuits. The controller 21 controls the operation of the entire drive recorder 1 by having the CPU execute a program stored in ROM, using RAM as a working area. Note that the controller 21 may be partially or entirely composed of hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array).

[0013] The timer unit 22 counts for a predetermined period of time according to instructions from the controller 21. Specifically, the timer unit 22 starts counting for the predetermined period of time when it receives a count start instruction from the controller 21. The timer unit 22 also notifies the controller 21 of the end of the predetermined period of time when the counting is complete.

[0014] The cooling fan 3 is a fan that cools the inside of the drive recorder 1's casing. For example, the cooling fan 3 cools the SoC 2. The cooling fan 3's rotation speed is controlled by the controller 21, and it outputs a pulse to the pulse detection unit 5 with each rotation. For example, the cooling fan 3 outputs one pulse for each rotation.

[0015] Switch 4 is located between the cooling fan 3 and the pulse detection unit 5, and connects or disconnects the control lines of the cooling fan 3 and the pulse detection unit 5. In other words, when switch 4 is disconnected, it blocks the output of pulses from the cooling fan 3 to the pulse detection unit 5.

[0016] The pulse detection unit 5 detects the pulses output from the cooling fan 3. The pulse detection unit 5 counts the number of detected pulses and notifies the counted number of pulses when a acquisition request is received from the controller 21.

[0017] Next, an operation example of the rotation speed control of the cooling fan 3 by the drive recorder 1 will be described using FIG. 1.

[0018] As shown in FIG. 1, the controller 21 first outputs an off instruction to the switch 4 (step S1). Specifically, the controller 21 cuts off the control line by the switch 4 before acquiring the number of pulses from the pulse detection unit 5. Thereby, the input of pulses to the pulse detection unit 5 stops, and the number of pulses detected by the pulse detection unit 5 is not updated.

[0019] Thereafter, the controller 21 acquires the number of pulses from the pulse detection unit 5 as a start value (step S2).

[0020] Subsequently, the controller 21 outputs an on instruction to the switch 4 (step S3-1) and outputs a timer start instruction to the timer unit 22 (step S3-2). Thereby, the update of the number of pulses detected by the pulse detection unit 5 is started, and the timer unit 22 starts counting for a certain period of time.

[0021] Subsequently, the timer unit 22 gives a timer end notification to the controller 21 at the timing when the counting for a certain period of time ends (step S4). When the controller 21 receives the timer end notification from the timer unit 22, it outputs an off instruction to the switch 4 (step S5). Thereby, the input of pulses to the pulse detection unit 5 stops, and the update of the number of pulses detected by the pulse detection unit 5 stops.

[0022] Next, the controller 21 acquires the number of pulses from the pulse detector 5 as the end value (step S6). Then, the controller 21 calculates the current rotation speed of the cooling fan 3 based on the start value acquired in step S2 and the end value acquired in step S6, and performs rotation speed control of the cooling fan 3 based on the calculated rotation speed (step S7). Specifically, the controller 21 calculates the number of pulses in a certain period from the start value and the end value, that is, the number of rotations of the cooling fan 3 in a certain period, and calculates the rotation speed (rotations per minute: rpm) based on the number of rotations. Then, the controller 21 compares the calculated rotation speed with the target rotation speed, and adjusts the duty ratio of the control signal output from the controller 21 to the cooling fan 3 so that the calculated rotation speed approaches the target rotation speed.

[0023] Thus, in the present disclosure, when starting the count for a certain period, the control line is connected by the switch 4, and when ending the count for a certain period, the control line is cut off, so that the pulse detector 5 can detect pulses only during the period when the timer unit 22 is counting. And in the present disclosure, after the switch 4 is cut off, that is, at the timing when the number of pulses detected by the pulse detector 5 does not fluctuate, the number of pulses is acquired from the pulse detector 5. Thereby, even if the timing at which the controller 21 acquires the number of pulses from the pulse detector 5 varies, since the number of pulses does not fluctuate, it is possible to reduce the decrease in the accuracy of the number of pulses. That is, according to the present disclosure, even when the controller 21 is not good at real-time control, the detection accuracy of the rotation speed of the cooling fan 3 can be improved.

[0024] Next, the operation timings of each part of the drive recorder 1 will be described using FIG. 2. FIG. 2 is a timing chart of the operation of the drive recorder 1. In FIG. 2, the operation timings of the timer unit 22, the controller 21, the switch 4, and the pulse detector 5 are shown. In FIG. 2, it is assumed that the time t1 is the time when the ignition (IG) of the vehicle is turned on.

[0025] As shown in Figure 2, when the IG is turned on at time t1, the controller 21 turns on switch 4. As a result, the pulse detection unit 5 detects the pulses output from the cooling fan 3 and counts the number of detected pulses. Although Figure 2 shows a configuration in which switch 4 is turned on after the IG is turned on, a configuration in which switch 4 is turned off is also possible. Alternatively, the state of switch 4 when the IG was last turned off may be maintained even after time 1.

[0026] Next, at time t2, the controller 21 outputs an off command to turn off switch 4, and at time t3, switch 4 is turned off. As a result, the pulse detection unit 5 can no longer detect pulses output from the cooling fan 3, and the count of detected pulses stops (is not updated).

[0027] Subsequently, at time t4, the controller 21 starts a read process to acquire the number of pulses (count value) from the pulse detection unit 5, and at time t5, acquires the number of pulses as the starting value. As a result, the controller 21 acquires the number of pulses during the period when the number of pulses in the pulse detection unit 5 is not updated, so even if the acquisition timing (time t5) varies, it is possible to prevent variations in the number of pulses acquired.

[0028] Subsequently, at time t6, the controller 21 outputs an ON command to turn on switch 4, and at time t7, switch 4 is turned ON. As a result, the pulse detection unit 5 detects the pulses output from the cooling fan 3 and counts the number of detected pulses. Also at time t6, the controller 21 outputs a timer start command to the timer unit 22, and at time t7, the timer unit 22 starts counting for a fixed period of time. In other words, the controller 21 starts counting the number of pulses by the pulse detection unit 5 at the same time as the timer unit 22 starts counting for a fixed period of time.

[0029] Next, the timer unit 22 notifies the controller 21 of the timer completion at time t8, a certain time D1 after time t7. After receiving the timer completion notification, the controller 21 outputs an off command to turn off switch 4 (at time t9), and switch 4 is turned off at time t10. As a result, the pulse detection unit 5 can no longer detect pulses output from the cooling fan 3, and the count of detected pulses stops (is not updated).

[0030] Subsequently, at time t11, the controller 21 starts a read process to acquire the number of pulses (count value) from the pulse detection unit 5, and at time t12, it acquires the number of pulses as the final value. As a result, the controller 21 acquires the number of pulses during the period when the number of pulses in the pulse detection unit 5 is not updated, so even if the acquisition timing (time t12) varies, it can prevent the number of acquired pulses from varying.

[0031] In this way, the drive recorder 1 performs read processing while the switch 4 is off, that is, while the pulse detection unit 5 has stopped counting pulses, thereby preventing variations in the number of pulses acquired even if the timing of acquiring the start and end values ​​varies.

[0032] As shown in Figure 2, the counting period D2 of the pulse detection unit 5 is from the time the timer unit 22 stops counting (time t8) until the switch 4 is turned off (time t10). In other words, the counting period D2 is longer than the constant time D1 by a time difference ΔD. However, this time difference ΔD is the time required for the controller 21 to perform a simple process of turning off the switch 4, so if it occurs, it is only a very short time. Also, as mentioned above, the time difference ΔD is the time required for the simple process of turning off the switch 4, so the time variation is extremely small. For this reason, the controller 21 may predict the time difference ΔD in advance through experiments, etc., and calculate the rotation speed using the total time obtained by adding the constant time D1 to the predicted time difference ΔD. This can improve the accuracy of the rotation speed calculated from the number of pulses.

[0033] Furthermore, while Figure 2 shows an example of acquiring the start value immediately after starting the vehicle (ignition on), the read process for acquiring the start value may be omitted, for example, after time t12. This is because the switch 4 remains off even after the read process for the end value, so the count value of the pulse detection unit 5 does not change. For this reason, the controller 21 may use the previous end value as the current start value from the second time onward. This reduces the processing load on the controller 21 because it does not need to perform the read process for acquiring the start value after the initial timing.

[0034] As described above, the in-vehicle device (drive recorder 1) according to the embodiment includes a fan (cooling fan 3), a pulse detection unit 5, a switch 4, a controller 21, and a timer unit 22. The pulse detection unit 5 detects pulses output each time the fan rotates. The switch 4 is provided on the control line through which pulses are input from the fan to the pulse detection unit 5, and connects or disconnects the control line. The controller 21 calculates the fan speed based on the number of pulses detected by the pulse detection unit 5 within a certain period of time. The timer unit 22 counts for a certain period of time according to the instructions of the controller 21. The switch 4 connects the control line when the timer unit 22 starts counting for a certain period of time, and disconnects the control line when the timer unit 22 finishes counting for a certain period of time. After the control line is disconnected by the switch 4, the controller 21 obtains the number of pulses from the pulse detection unit 5 and calculates the rotation speed.

[0035] According to this disclosure, when a count for a certain period of time is started, the control line is connected by switch 4, and when the count for a certain period of time is finished, the control line is disconnected, so that the pulse detection unit 5 can detect pulses only during the period that the timer unit 22 is counting. Furthermore, in this disclosure, after switch 4 is disconnected, that is, at a timing when the number of pulses detected by the pulse detection unit 5 does not change, the number of pulses is acquired from the pulse detection unit 5. As a result, even if the timing at which the controller 21 acquires the number of pulses from the pulse detection unit 5 varies, the number of pulses does not change, thus reducing the decrease in accuracy of the pulse count. In other words, according to this disclosure, even if the controller 21 is not adept at real-time control, the accuracy of detecting the fan rotation speed can be improved.

[0036] In the embodiment described above, the switch 4 is shown to be connected or disconnected by the controller 21, but it may also be connected or disconnected by the timer unit 22. This point will be explained with reference to Figure 3.

[0037] Figure 3 shows an example of the configuration and operation of a modified drive recorder 1. Note that the configuration of drive recorder 1 shown in Figure 3 is the same as in Figure 1, so the explanation of the configuration example is omitted.

[0038] Furthermore, in the example of operation of drive recorder 1 shown in Figure 3, the processing of step S15 differs from the example of operation shown in Figure 1. Specifically, steps S11 to S14 correspond to steps S1 to S4. Also, steps S16 to S17 correspond to steps S6 to S7.

[0039] As shown in Figure 3, in this modified example, the timer unit 22 outputs an off command to turn off switch 4 (step S15). That is, the timer unit 22 notifies the controller 21 of the timer completion (step S14) and turns off switch 4 by its own command. This makes the time difference (time difference ΔD shown in Figure 2) between the end of the fixed time D1 and the timing when switch 4 is turned off shorter compared to when the controller 21 turns off switch 4. In other words, the drive recorder 1 can improve the accuracy of its rotation speed calculation.

[0040] Furthermore, while the embodiments and modifications described above show the timer unit 22 being implemented on the SoC2 together with the controller 21, this is not the only way to go. This point will be explained with reference to Figure 4.

[0041] Figure 4 shows a partial example of the configuration of a modified drive recorder 1. For the sake of explanation, only the controller 21, timer unit 22, and switch 4 are shown in Figure 4.

[0042] As shown in Figure 4, the timer unit 22 may be provided outside the SoC2. For example, the timer unit 22 may be composed of a digital IC. Alternatively, the timer unit 22 may be a timer unit mounted on another in-vehicle device.

[0043] Even in the configuration shown in Figure 4, the timer unit 22 can output an off command to turn off switch 4 (step S15 shown in Figure 3). Note that in Figure 4, the controller 21 may output the off command instead of the timer unit 22. In this way, the SoC2 can be miniaturized by not implementing the timer unit 22 on the SoC2.

[0044] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0045] 1. Dashcam 2 SoC 3 Cooling fan 4 switches 5. Pulse detection unit 21 Controllers 22 Timer section

Claims

1. Fans, A pulse detection unit that detects pulses output each time the fan rotates, A switch is provided in the control line through which the pulse is input from the fan to the pulse detection unit, and which connects or disconnects the control line. A controller that calculates the rotation speed of the fan based on the number of pulses detected by the pulse detection unit within a certain period of time, A timer unit that counts the fixed time period according to the instructions of the controller, Equipped with, The aforementioned switch is When the timer unit starts counting for the specified period, it connects the control line, and when the timer unit finishes counting for the specified period, it disconnects the control line. The aforementioned controller, After the control line is interrupted by the switch, the number of pulses is obtained from the pulse detection unit and the rotation speed is calculated. In-vehicle device.

2. The aforementioned controller, The switch is connected while the timer unit is counting for the specified period of time, and disconnected when the timer unit is not counting for the specified period of time. The in-vehicle device according to claim 1.

3. The pulse detection unit is When the aforementioned switch is connected, the system performs a process to count the number of pulses detected from the fan. The aforementioned controller, Before the timer unit starts counting for the specified period, the switch is turned off and the number of pulses counted by the pulse detection unit is obtained as the starting value. Then, the switch is turned on when the counting for the specified period begins, and after the counting for the specified period ends, the switch is turned off and the number of pulses counted by the pulse detection unit is obtained as the ending value. The rotation speed is then calculated based on the starting value and the ending value. The in-vehicle device according to claim 2.

4. The aforementioned controller, When the vehicle is started and the first rotation speed is calculated, the process of obtaining the starting value is performed, and when calculating the rotation speed from the second time onward, the previous ending value is used as the current starting value. The in-vehicle device according to claim 3.

5. The timer unit is At the end of the aforementioned fixed time count, the switch is shut off. The in-vehicle device according to claim 1.

6. Fans, A pulse detection unit that detects pulses output each time the fan rotates, A switch is provided in the control line through which the pulse is input from the fan to the pulse detection unit, and which connects or disconnects the control line. A timer unit that counts for a set period of time, A control method for an in-vehicle device, comprising: The control step includes calculating the rotation speed of the fan based on the number of pulses detected by the pulse detection unit within a certain period of time, The control process described above is: When the timer unit starts counting for the specified period, it connects the control line, and when the timer unit finishes counting for the specified period, it disconnects the control line. After the control line is interrupted by the switch, the number of pulses is obtained from the pulse detection unit and the rotation speed is calculated. A method for controlling in-vehicle devices.

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