Fan Control Device

Abstract

A fan control device capable of reducing noise during operation of a fan capable of cooling an object to be cooled by blowing air. [Solution] A fan control device according to an embodiment includes a cooling fan, an acquisition unit, a determination unit, and a fan control unit. The cooling fan cools a housing by rotating according to a voltage duty ratio to blow air. The acquisition unit acquires the temperature of the housing. The determination unit determines the duty ratio according to the temperature of the housing based on a nonlinear relationship between a first temperature corresponding to the minimum rotation speed of the cooling fan and a second temperature corresponding to the maximum rotation speed of the cooling fan, and the difference between the temperature of the housing and the first temperature and the duty ratio. The fan control unit controls the rotation of the cooling fan based on the determined duty ratio.

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a fan control device. [Background technology]

[0002] Some devices, such as servers and personal computers, are equipped with fans as a means of achieving cooling functions. The fan's rotation speed is controlled, for example, at a fixed value. The fan's rotation speed is also controlled based on temperatures acquired from a temperature sensor in the CPU (Central Processing Unit), temperature sensors in various devices, or thermistors. The following methods, for example, are available for controlling the fan's rotation speed.

[0003] · Adjusting the duty ratio in PWM (Pulse Width Modulation) -Adjusting the fan voltage value For example, when controlling the fan speed based on temperature, the following formula (1) is often used. In formula (1) below, the minimum temperature, minimum speed, and the amount by which the speed should be changed per 1°C are set in advance. Next, the difference between the minimum temperature and the actually measured temperature (product temperature) is calculated, and the calculated difference is multiplied by a linear coefficient, and the result is added to the minimum speed to calculate the fan speed.

[0004] Formula for temperature-dependent fan control: Rotation speed = minimum rotation speed + (product temperature - minimum temperature) × linear coefficient (1) When the duty ratio is adjusted in equation (1), the rotation speed corresponds to the duty ratio. When the voltage value is adjusted in equation (1), the rotation speed corresponds to the voltage value. When controlling the fan rotation speed based on equation (1), the noise level increases as the fan rotation speed increases. Furthermore, although the maximum rotation speed is generally set within a range where noise is not likely to be a problem, the rotation of the fan may be perceived as noise depending on the installation location or the customer. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a fan control device capable of reducing noise during operation of a fan capable of cooling an object to be cooled by blowing air. [Means for solving the problem]

[0006] A fan control device according to an embodiment includes a cooling fan, an acquisition unit, a determination unit, and a fan control unit. The cooling fan cools a housing by rotating according to a voltage duty ratio to blow air. The acquisition unit acquires the temperature of the housing. The determination unit determines the duty ratio according to the temperature of the housing based on a nonlinear relationship between a first temperature corresponding to the minimum rotation speed of the cooling fan and a second temperature corresponding to the maximum rotation speed of the cooling fan, and the duty ratio and a difference between the temperature of the housing and the first temperature. The fan control unit controls the rotation of the cooling fan based on the determined duty ratio. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view illustrating an example of an electronic device according to an embodiment. [Figure 2] FIG. 2 is a hardware block diagram illustrating an example of a hardware configuration of the electronic device according to the embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of a functional configuration of a processing circuit according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a coefficient table according to the embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of control characteristics of the cooling fan according to the embodiment. [Figure 6] FIG. 6 is a flowchart illustrating an example of a procedure for a fan control process according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of a fan control device will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below. Hereinafter, an electronic device equipped with a fan control device according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the fan control device may also be referred to as a cooling fan control device.

[0009] (Embodiment) A schematic configuration of an electronic device 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a perspective view showing an example of an electronic device 1 according to an embodiment.

[0010] The electronic device 1 performs various electronic controls according to the application. For example, the electronic device 1 is a POS (Point Of Sales) terminal that performs various processes related to product transactions in a store, or a server device (server machine) that is connected to multiple POS terminals and manages the multiple POS terminals and sales management in the store. However, the electronic device 1 is not limited to these.

[0011] The electronic device 1 is housed in a housing 2 and includes a computer device 10, a fan control device 30, and cooling fans 3, 4, and 5. The fan control device 30 may be realized by, for example, a microcomputer.

[0012] The computer device 10 controls the entire electronic device 1. The computer device 10 and the fan control device 30 include heat-generating elements such as a CPU (Central Processing Unit) and a memory device. Therefore, the fan control device 30 appropriately cools these elements according to the temperature inside the housing 2 to ensure stable operation of the CPU, memory device, etc.

[0013] Cooling fan 3, cooling fan 4, and cooling fan 5 are used for this cooling purpose. Cooling fan 3, cooling fan 4, and cooling fan 5 are equipped with fans rotated by motors and cool the inside of housing 2 by discharging air inside housing 2 to the outside of housing 2. Note that the number of cooling fans included in electronic device 1 is not limited to the above three. Cooling fan 3, cooling fan 4, and cooling fan 5 cool housing 2 by rotating and blowing air according to, for example, the duty ratio of the voltage input to cooling fan 3, cooling fan 4, and cooling fan 5, respectively. The duty ratio is, for example, the proportion of the on time to one cycle of a drive pulse that drives cooling fan 3, cooling fan 4, and cooling fan 5 with a voltage.

[0014] The fan control device 30 acquires a coefficient table 121 (see FIG. 2) related to the control characteristics of a plurality of cooling fans including cooling fans 3, 4, and 5. The fan control device 30 also repeatedly acquires the temperature T inside the housing 2 measured by a temperature sensor 6, which will be described later. Furthermore, the fan control device 30 outputs control commands to the currently connected cooling fans 3, 4, and 5, respectively, based on the calculation results of a processing circuit 111 (see FIG. 2) using the temperature T.

[0015] The control command is, for example, information specifying the cooling fan and the duty ratio of the drive pulse applied to the cooling fan. At this time, the rotation speed of the cooling fan is controlled by PWM (Pulse Width Modulation). That is, the rotation of the cooling fan is controlled based on the temperature acquired from a temperature acquisition device, a thermistor, or the like. In response to the control command, the fan control device 30 controls the operation of the cooling fan 3, the cooling fan 4, and the cooling fan 5. This cools the computer device 10, the fan control device 30, and the like.

[0016] The side of the housing 2 is provided with an air vent 8, which is an air outlet for discharging the air sucked in by each of the cooling fans 3, 4, and 5 to the outside of the housing 2, and a connector 9 for connecting the electronic device 1 to a display device such as a monitor or an operating device such as a keyboard, not shown.

[0017] The hardware configuration of the fan control device 30 will be described below with reference to Fig. 2. Fig. 2 is a hardware block diagram showing an example of the hardware configuration of the fan control device 30 according to the embodiment.

[0018] The electronic device 1 includes a computer device 10, a fan control device 30, cooling fans 3, 4, and 5 connected to the fan control device 30, a temperature sensor 6, and a power switch .

[0019] The fan control device 30 includes a processing circuit 111, a ROM (Read Only Memory) 112, a RAM (Random Access Memory) 113, a storage unit 12, a cooling fan driver 14, a sensor interface 15, and a communication controller 16. The processing circuit 111, the ROM 112, the RAM 113, the storage unit 12, the cooling fan driver 14, and the sensor interface 15 are connected via an internal bus 13. The fan control device 30 is realized by, for example, a CPU board. In other words, the fan control device 30 has the configuration of a typical computer.

[0020] The storage unit 12 is connected to the processing circuit 111 and the like via an internal bus 13. The storage unit 12 is a storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The storage unit 12 may also be a non-volatile memory such as a flash memory that retains stored information even when the power is turned off. The storage unit 12 stores a coefficient table 121. The storage unit 12 may further store a control program that operates the processing circuit 111. The coefficient table 121 will be described in detail later.

[0021] The cooling fan driver 14 is a drive circuit for the motors that drive the cooling fans 3, 4, and 5. The cooling fan driver 14 may include a different driver for each of the cooling fans 3, 4, and 5, or one cooling fan driver 14 may drive multiple cooling fans.

[0022] The cooling fan driver 14 generates a pulse waveform with the specified duty ratio based on the control command received from the processing circuit 111, and drives the cooling fan 3 with the generated pulse waveform. The processing circuit 111 issues control commands to all cooling fans connected to the computer device 10 via the cooling fan driver 14.

[0023] The duty ratio of the drive pulse corresponds to the fan speed of the cooling fan 3 to which the drive pulse is applied. For example, the larger the duty ratio of the drive pulse, the higher the fan speed, and the smaller the duty ratio of the drive pulse, the lower the fan speed.

[0024] The sensor interface 15 acquires the output of the temperature sensor 6 installed inside the housing 2 of the electronic device 1, i.e., the temperature T inside the housing 2, and outputs the acquired temperature (hereinafter referred to as acquired temperature) T to the processing circuit 111.

[0025] The temperature sensor 6 is, for example, a thermistor. A thermistor is an element that changes its resistance value in response to the temperature inside the housing 2. There is no limit to the number of temperature sensors 6 that can be installed. For example, the temperature sensors 6 are installed in each of the areas cooled by the cooling fans 3, 4, and 5.

[0026] The communication controller 16 controls communication between the computer device 10 and the fan control device 30. As a result, the communication controller 16 receives and transmits various types of information between the computer device 10 and the fan control device 30.

[0027] The processing circuit 111 controls the overall operation of the fan control device 30. The processing circuit 111 loads a control program stored in the ROM 112 into the RAM 113. The processing circuit 111 operates in accordance with the control program loaded into the RAM 113, thereby controlling the operation of the fan control device 30. The processing circuit 111 has the configuration of a general computer.

[0028] The functional configuration of the processing circuit 111 will be described below with reference to Fig. 3. Fig. 3 is a diagram showing an example of the functional configuration of the processing circuit 111. As shown in Fig. 3, the processing circuit 111 has an acquisition unit 122, a setting unit 123, a determination unit 125, and a fan control unit 127.

[0029] The acquisition unit 122 acquires a signal indicating that the power switch 7 has been pressed (power ON). In response to acquisition of the signal indicating that the power switch 7 has been pressed, the processing circuit 111 starts its own operation. The acquisition unit 122 also acquires a signal indicating that the power switch 7 has been turned off (power OFF). In response to acquisition of the signal indicating that the power switch 7 has been turned off, the processing circuit 111 stops its own operation.

[0030] The acquisition unit 122 repeatedly acquires the temperature T of the casing 2 (for example, the temperature inside the casing 2) from the temperature sensor 6. If multiple temperature sensors 6 are installed inside the casing 2, the acquisition unit 122 acquires the temperatures T from all of the temperature sensors. The acquisition unit 122 associates all of the temperatures T of the casing 2 acquired from the temperature sensors 6 with the time of acquisition and stores them in the RAM 113 or the storage unit 12. At this time, the acquisition unit 122 associates the temperatures T with which temperature sensors measured the values ​​and stores them in the RAM 113 or the storage unit 12. The repetition time for acquiring the temperatures T is set in advance depending on the processing capacity of the processing circuit 111. Hereinafter, the temperatures acquired from the temperature sensors 6 will be referred to as acquired temperatures.

[0031] When a basic setting or a silent setting is input by a user via an input interface (not shown), the setting unit 123 sets a coefficient according to the basic setting or the silent setting. The basic setting is, for example, a setting indicating that the level of noise generated by the operation of cooling fan 3, cooling fan 4, and cooling fan 5 is basic. The silent setting is, for example, a setting indicating that the level of noise generated by the operation of cooling fan 3, cooling fan 4, and cooling fan 5 is lower than that of the basic setting.

[0032] The coefficients for the basic setting and the quiet setting will be described below. These coefficients correspond to the first-order coefficient (first-order coefficient), second-order coefficient (second-order coefficient), and third-order coefficient (third-order coefficient) in the following equation (2) (hereinafter referred to as the duty ratio determination equation) for calculating the set duty ratios to be supplied to cooling fan 3, cooling fan 4, and cooling fan 5. The set duty ratios correspond to the duty ratios generated by cooling fan driver 14. The following equation (2) for calculating the set duty ratios to be generated is stored in storage unit 12, ROM 112, RAM 113, etc.

[0033] Set duty ratio = Minimum duty ratio + (Acquired temperature - Minimum temperature) x Primary coefficient + (obtained temperature - minimum temperature)^2 x quadratic coefficient + (obtained temperature - minimum temperature)^3 × cubic coefficient (2)

[0034] The minimum duty ratio in duty ratio determination formula (2) corresponds to the minimum rotation speed of each of cooling fans 3, 4, and 5. The minimum temperature corresponds to the preset temperature of housing 2. That is, the minimum rotation speed in formula (2) corresponds to the minimum duty ratio at the minimum temperature. Duty ratio determination formula (2) is a calculation formula for determining the duty ratio between a first temperature (minimum temperature) corresponding to the minimum rotation speed of the cooling fans and a second temperature (maximum temperature) corresponding to the maximum rotation speed of the cooling fans.

[0035] In other words, the duty ratio determination formula (2) corresponds to a calculation formula for determining the duty ratio according to the temperature of the housing 2, based on the nonlinear relationship between the duty ratio and the difference between the temperature of the housing 2 (obtained temperature) and the first temperature (lowest temperature), where the first temperature (lowest temperature) corresponds to the minimum rotation speed of the cooling fan and the second temperature (highest temperature) corresponds to the maximum rotation speed of the cooling fan. The duty ratio corresponding to the highest temperature (hereinafter referred to as the maximum duty ratio) corresponds to the maximum rotation speed of the cooling fan.

[0036] The linear coefficient in duty ratio determination formula (2) indicates a coefficient by which the duty ratio is proportional to the linear difference between the acquired temperature and the minimum temperature (hereinafter referred to as the temperature difference). The quadratic coefficient in duty ratio determination formula (2) indicates a coefficient by which the duty ratio is proportional to the quadratic difference. The cubic coefficient in duty ratio determination formula (2) indicates a coefficient by which the duty ratio is proportional to the linear difference. While duty ratio determination formula (2) only indicates the third order of the temperature difference, this is not a limitation, and duty ratio determination formula (2) may include higher-order terms, such as the fourth order or higher, of the temperature difference. While duty ratio determination formula (2) is expressed as being added to the minimum duty ratio, this is not a limitation. For example, a value obtained by multiplying the linear and nonlinear temperature differences by coefficients may be subtracted from the maximum duty ratio.

[0037] The above nonlinear relationship is expressed in duty ratio determination formula (2) as an equation having a finite power series of the temperature difference. Furthermore, in addition to the above nonlinear relationship, duty ratio determination formula (2) has a linear relationship between the difference and the duty ratio (the first and second terms in duty ratio determination formula (2)). Specifically, duty ratio determination formula (2) has the minimum duty ratio corresponding to the minimum rotation speed as the first term of the power series, has a first-order coefficient of the temperature difference, and has multiple coefficients of the second order and higher of the temperature difference.

[0038] When the basic setting is selected by a user instruction via the input interface, the setting unit 123 sets multiple coefficients (multi-order coefficients) of second order and higher in the duty ratio determination formula (2) to 0. In addition, the setting unit 123 sets the first-order coefficient in the duty ratio determination formula (2) to a value corresponding to the basic setting (hereinafter referred to as the basic value).

[0039] Furthermore, when the silent setting is selected by a user instruction via the input interface, the setting unit 123 sets the first-order coefficient in the duty ratio determination formula (2) to zero, and sets multiple coefficients (multi-order coefficients) from the second order onwards to values ​​corresponding to the silent setting (hereinafter referred to as silent values).

[0040] The coefficient table stored in the storage unit 12 will be described below. FIG. 4 is a diagram showing an example of the coefficient table 121. Two quiet settings are shown in FIG. 4. Quiet setting 1 is quieter than the basic setting but less quiet than quiet setting 2. Quiet setting 2 is the quietest setting. The coefficient table shown in FIG. 4 is just an example, and the number of quiet settings is not limited to two, and may be one or three or more.

[0041] As shown in FIG. 4, the minimum temperature Tmin, maximum temperature Tmax, minimum duty ratio Rmin, and maximum duty ratio Rmax are all the same in the basic setting, silent setting 1, and silent setting 2. Note that the maximum temperature Tmax may be different between the basic setting, silent setting 1, and silent setting 2. The maximum temperature Tmax may also be different between the basic setting, silent setting 1, and silent setting 2. Also, as shown in FIG. 4, in the basic setting, the first-order coefficient is indicated by L. The first-order coefficient L is set in advance, but can be set, changed, or adjusted as appropriate by the user via an input interface (not shown). Also, as shown in FIG. 4, the higher-order coefficients (second-order coefficient and third-order coefficient) in the basic setting are zero.

[0042] Also, as shown in FIG. 4, the first-order coefficients in the silent setting 1 and the silent setting 2 are zero. The second-order coefficient is a value smaller than the first-order coefficient and satisfies 0 < Q1 < 1 < L. Also, the third-order coefficient is a value smaller than the second-order coefficient and satisfies 0 < Q2 < Q1. For example, the order (number of digits) of the second-order coefficient is smaller than the order (number of digits) of the first-order coefficient. Also, the order (number of digits) of the second-order coefficient is smaller than the order (number of digits) of the first-order coefficient. For example, the second-order coefficient is on the order of 10^(-2), and the third-order coefficient is on the order of 10^(-4).

[0043] The determination unit 125 determines a duty ratio corresponding to the temperature (acquired temperature) of the housing 2 based on a non-linear relationship between the difference (temperature difference) between the temperature (acquired temperature) of the housing 2 and the first temperature (minimum temperature: Tmin) corresponding to the minimum rotation speed of the cooling fan and the duty ratio, between the first temperature (minimum temperature: Tmin) and the second temperature (maximum temperature: Tmax) corresponding to the maximum rotation speed of the cooling fan. For example, the determination unit 125 determines a duty ratio corresponding to the temperature of the housing 2 based on the duty ratio determination formula (2) using the coefficient set by the setting unit 123 and the temperature difference.

[0044] Specifically, the determination unit 125 substitutes the temperature difference into the duty ratio determination formula (2) using the coefficient set by the setting unit 123 to calculate the set duty ratio. For example, when the temperature (acquired temperature) of the housing 2 is lower than the first temperature (minimum temperature: Tmin), the determination unit 125 determines the duty ratio corresponding to the minimum rotation speed (minimum duty ratio: Rmin) as the duty ratio for controlling the rotation of the cooling fan. Also, when the temperature (acquired temperature) of the housing 2 is higher than the second temperature (maximum temperature: Tmax), the determination unit 125 determines the duty ratio corresponding to the maximum rotation speed (maximum duty ratio: Rmax) as the duty ratio for controlling the rotation of the cooling fan.

[0045] Furthermore, when the silent setting is selected, the determination unit 125 compares the duty ratio determined based on the duty ratio determination formula (2) including a nonlinear relationship with the temperature (acquired temperature) of the housing 2 with the duty ratio corresponding to the maximum rotation speed (maximum duty ratio: Rmax). Next, if the determined set duty ratio is greater than the maximum duty ratio Rmax, the determination unit 125 determines the maximum duty ratio Rmax corresponding to the maximum rotation speed as the duty ratio for controlling the rotation of the cooling fan. Furthermore, if the acquired temperature is between the minimum temperature: Tmin and the maximum temperature: Tmax and the duty ratio determined based on the duty ratio determination formula (2) is less than the maximum duty ratio: Rmax, the determination unit 125 determines the duty ratio determined based on the duty ratio determination formula (2) as the control command for the cooling fan.

[0046] The fan control unit 127 controls the rotation of the cooling fans based on the determined duty ratio. Specifically, the fan control unit 127 outputs the determined duty ratio as a control command to the cooling fan driver 14. As a result, the cooling fan driver 14 generates a pulse waveform corresponding to the determined duty ratio. The cooling fan driver 14 drives the cooling fans 3, 4, and 5 using the generated pulse waveform. The fan control unit 127 may also be referred to as a cooling fan control unit.

[0047] (Cooling fan control characteristics) The control characteristics of the cooling fan will be described using Fig. 5. Fig. 5 is a diagram showing an example of the control characteristics of the cooling fan. In the control characteristics shown in Fig. 5, the maximum temperature Tmax will be described as being different between the basic setting and the silent setting. Also, in the control characteristics shown in Fig. 5, the description will be given assuming that there is only one silent setting.

[0048] Cooling fans 3, 4, and 5 cool heat-generating elements in the vicinity of cooling fans 3, 4, and 5 by rotating at a fan speed according to the acquired temperature T in the vicinity of cooling fans 3, 4, and 5. The fan speed is determined by the duty ratio of a drive pulse applied to a motor that drives cooling fans 3, 4, and 5 to rotate.

[0049] The duty ratio is, for example, the ratio of the ON time to the time of one cycle of the drive pulse. The larger the duty ratio, i.e., the greater the ratio of the ON time to the time of one cycle of the drive pulse, the faster the fan speed.

[0050] According to the control characteristics shown in Fig. 5, when the acquired temperature T is less than 25°C, the cooling fan is driven with a drive pulse having a duty ratio D = 30%. When the basic setting is selected, the duty ratio D increases linearly with the increase in the acquired temperature T until the acquired temperature T reaches 50°C. When the basic setting is selected, once the acquired temperature T reaches 50°C, the cooling fan is driven with a drive pulse having a maximum duty ratio Rmax = 80%.

[0051] Furthermore, according to the control characteristics shown in Fig. 5, when the quiet setting is selected, the duty ratio D increases exponentially with a nonlinear SS as the acquired temperature T increases until the acquired temperature T reaches 60°C. When the quiet setting is selected and the acquired temperature T reaches 60°C, the cooling fan is driven with a drive pulse having a maximum duty ratio Rmax = 80%. Note that the quiet setting related to the nonlinear SS corresponds to, for example, quiet setting 1 described in Fig. 4 with the cubic coefficient C1 set to zero.

[0052] The configuration of this embodiment has been described above. Below, the procedure for the process of controlling the rotation speed of the cooling fan (hereinafter referred to as fan control process) executed by the fan control device 30 will be described. FIG. 6 is a flowchart showing an example of the procedure for the fan control process. The fan control process starts when the power is turned on by the user operating the power switch 7. For the sake of concreteness, the following description will be given assuming that there is only one quiet setting.

[0053] (Fan control processing) (Step S601) If the silent setting is set by a user instruction via the input interface (input unit) (Yes in step S601), the process proceeds to step S603. If the silent setting is not set (No in step S601), that is, if the basic setting is selected by a user instruction via the input interface (input unit), the process proceeds to step S602.

[0054] (Step S602) The setting unit 123 sets the first-order coefficient to a basic value in the duty ratio determination formula (2). In addition, the setting unit 123 sets the second-order and subsequent coefficients to zero in the duty ratio determination formula (2).

[0055] (Step S603) The setting unit 123 sets the first-order coefficient in the duty ratio determination formula (2) to 0. In addition, the setting unit 123 sets the second-order and subsequent coefficients in the duty ratio determination formula (2) to silence values.

[0056] (Step S604) The acquisition unit 122 acquires the temperature T of the housing 2 from the temperature sensor 6. The acquisition unit 122 stores the temperature T of the housing 2 in the RAM 113 or the storage unit 12.

[0057] (Step S605) The determination unit 125 compares the temperature (obtained temperature) T of the housing 2 with the minimum temperature Tmin. If the obtained temperature T is equal to or lower than the minimum temperature Tmin (No in step S605), the process proceeds to step S606. If the obtained temperature T is higher than the minimum temperature Tmin (Yes in step S605), the process proceeds to step S607.

[0058] (Step S606) The determining unit 125 determines the duty ratio as a control command for the fan to be the duty ratio corresponding to the minimum rotation speed (minimum duty ratio).

[0059] (Step S607) The determination unit 125 compares the temperature (obtained temperature) T of the housing 2 with the maximum temperature Tmax. If the obtained temperature T is less than the maximum temperature Tmax (Yes in step S607), the process proceeds to step S608. If the obtained temperature T is equal to or greater than the maximum temperature Tmax (No in step S607), the process proceeds to step S610.

[0060] (Step S608) The determination unit 125 calculates the duty ratio using the set coefficient based on the acquired temperature T and the duty ratio determination formula. Specifically, the determination unit 125 reads the duty ratio determination formula (2) from the storage unit 12, the ROM 112, or the RAM 113. Next, the determination unit 125 substitutes the set coefficient, the acquired temperature T, the minimum temperature Tmin, and the minimum duty ratio Rmin into the read duty ratio determination formula (2) to calculate the set duty ratio.

[0061] (Step S609) The determination unit 125 compares the set duty ratio T with the maximum duty ratio Rmax. If the set duty ratio T is less than the maximum duty ratio Rmax (Yes in step S609), the process proceeds to step S611. If the set duty ratio T is equal to or greater than the maximum duty ratio Rmax (No in step S609), the process proceeds to step S610.

[0062] (Step S610) The determining unit 125 determines the duty ratio as a control command for the fan to be the duty ratio corresponding to the maximum rotation speed (maximum duty ratio).

[0063] (Step S611) The determining unit 125 determines the duty ratio as the fan control command to be the calculated duty ratio (set duty ratio).

[0064] (Step S612) The fan control unit 127 uses the determined duty ratio to control the rotation speed of the cooling fan.

[0065] (Step S613) If the power is turned off by the user's operation of the power switch 7 (Yes in step S613), the fan control process ends. If the power is not turned off (No in step S613), the process from step S601 onwards is repeated after a preset specified time has elapsed.

[0066] As described above, the fan control device 30 of this embodiment acquires the temperature of the housing 2, and determines a duty ratio corresponding to the temperature of the housing 2 based on the nonlinear relationship between the difference (temperature difference) between the temperature of the housing 2 and the first temperature (minimum temperature Tmin) corresponding to the minimum rotation speed of the cooling fans 3, 4, and 5 that cool the housing 2 by blowing air through rotation according to the voltage duty ratio, and the second temperature (maximum temperature Tmax) corresponding to the maximum rotation speed of the cooling fans 3, 4, and 5, and controls the rotation of the cooling fans 3, 4, and 5 based on the determined duty ratio.

[0067] For example, the nonlinear relationship in the fan control device 30 according to this embodiment is expressed by duty ratio determination equation (2) having a finite power series of the temperature difference, and duty ratio determination equation (2) has a linear relationship between the temperature difference and the duty ratio in addition to the nonlinear relationship. Duty ratio determination equation (2) in the fan control device 30 according to this embodiment has, for example, the duty ratio corresponding to the minimum rotation speed as the first term of the power series, a first-order coefficient of the temperature difference, and multiple coefficients of second-order and higher orders of the temperature difference.

[0068] Specifically, when the basic setting is selected as the noise generated by the operation of cooling fan 3, cooling fan 4, and cooling fan 5, the fan control device 30 of this embodiment sets multiple coefficients of the second order and higher in duty ratio determination formula (2) to zero, and sets the first order coefficient to a value corresponding to the basic setting, and when the quiet setting is selected, sets the first order coefficient in duty ratio determination formula (2) to zero, and sets multiple coefficients of the second order and higher to a value corresponding to the quiet setting, and determines the duty ratio according to the temperature of the housing 2 based on the duty ratio determination formula (2) using the set coefficients and the temperature difference.

[0069] More specifically, when the temperature of the housing 2 is lower than the first temperature, the fan control device 30 according to this embodiment determines the duty ratio (minimum duty ratio) Rmin corresponding to the minimum rotation speed as the duty ratio for controlling the rotation of the cooling fans 3, 4, and 5. When the temperature of the housing 2 is higher than the second temperature, the fan control device 30 according to this embodiment determines the duty ratio (maximum duty ratio) Rmax corresponding to the maximum rotation speed as the duty ratio for controlling the rotation of the cooling fans 3, 4, and 5.

[0070] Furthermore, when a quiet setting is selected for the noise generated by the operation of cooling fans 3, 4, and 5, fan control device 30 according to this embodiment compares the duty ratio determined based on duty ratio determination formula (2) that includes a nonlinear relationship with the temperature of housing 2 with duty ratio (maximum duty ratio) Rmax corresponding to the maximum rotation speed. Next, if the determined duty ratio is greater than duty ratio (maximum duty ratio) Rmax corresponding to the maximum rotation speed, fan control device 30 according to this embodiment determines duty ratio (maximum duty ratio) Rmax corresponding to the maximum rotation speed as the duty ratio for controlling the rotation of cooling fans 3, 4, and 5.

[0071] For these reasons, the fan control device 30 according to this embodiment can use, as the duty ratio determination formula (2), a multidimensional calculation formula such as a quadratic or cubic expression, rather than just a linear expression for the temperature difference, to calculate the curve showing the change in duty ratio relative to the temperature of the housing 2. As a result, the fan control device 30 according to this embodiment can implement fan control that prioritizes quietness through the above control. Therefore, according to the fan control device 30 according to this embodiment, when the load on the heat-generating element is high and the temperature of the housing is at or above the minimum temperature Tmin, the cooling fans 3, 4, and 5 can be set to high rotation speeds, thereby cooling the housing 2 with an emphasis on quietness.

[0072] In addition, the fan control device 30 according to this embodiment can easily adjust the rotation speed of the cooling fan with an emphasis on quietness by changing the coefficient in the duty ratio determination formula (2) through software processing, unlike a configuration using a hardware circuit. As a result, the fan control device 30 according to this embodiment can realize low-cost control of the rotation of the cooling fan with an emphasis on quietness. As described above, the fan control device 30 according to this embodiment can provide a fan control device that can reduce noise during the operation of a fan that can cool an object by blowing air.

[0073] When the technical idea of ​​the embodiment is realized in a fan control method, the fan control method acquires the temperature of the housing 2, and determines a duty ratio corresponding to the temperature of the housing 2 based on a nonlinear relationship between a first temperature corresponding to the minimum rotation speed of a cooling fan that cools the housing 2 by rotating according to the duty ratio of a voltage and a second temperature corresponding to the maximum rotation speed of the cooling fan, and the duty ratio and controls the rotation of the cooling fan based on the determined duty ratio. The processing procedure of the fan control method conforms to the fan control processing of the embodiment. Furthermore, the effects of the fan control method are similar to those of the embodiment. For these reasons, a description of the processing procedure and effects of the fan control method will be omitted.

[0074] When the technical idea of ​​the embodiment is realized by a fan control program, the fan control program causes a computer to acquire the temperature of the housing 2, and determine a duty ratio corresponding to the temperature of the housing 2 based on the nonlinear relationship between the duty ratio and the difference between the temperature of the housing 2 and the first temperature, between a first temperature corresponding to the minimum rotation speed of a cooling fan that cools the housing 2 by blowing air according to the rotation according to the duty ratio of the voltage, and a second temperature corresponding to the maximum rotation speed of the cooling fan, and control the rotation of the cooling fan based on the determined duty ratio.

[0075] For example, the fan control process can be realized by installing the fan control program on a computer, such as a POS terminal installed in a store or a server device connected to multiple POS terminals to manage the multiple POS terminals and manage sales at the store, and then expanding the program in memory. In this case, the program that causes a computer to execute the fan control process can also be stored and distributed on a storage medium such as a magnetic disk (e.g., a hard disk), an optical disk (e.g., a CD-ROM or DVD), or a semiconductor memory. Furthermore, the distribution of the fan control program is not limited to the above media. For example, the program may be distributed using a telecommunications function, such as downloading via the Internet. The processing procedure of the fan control program conforms to the fan control process of the embodiment. Furthermore, the effects of the fan control program are similar to those of the embodiment. For these reasons, a description of the processing procedure and effects of the fan control program will be omitted.

[0076] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0077] 1 Electronic equipment 2. Case 3 Cooling Fan 4 cooling fans 5 Cooling Fan 6 Temperature Sensor 7 Power switch 8 Ventilation holes 9 Connectors 10 Computer equipment 111 Processing circuit 112 ROM 113 RAM 12 Storage section 121 Coefficient Table 122 Acquisition Department 123 Settings 125 Decision Section 127 Fan control unit 13 Internal Bus 14 Cooling Fan Driver 15 Sensor Interface 16 Communication Controller 30 Fan control device [Prior art documents] [Patent documents]

[0078] [Patent Document 1] Japanese Patent Application Publication No. 2018-25841

Claims

1. a cooling fan that cools the housing by blowing air according to the voltage duty ratio; an acquisition unit that acquires the temperature of the housing; a determination unit that determines the duty ratio according to the temperature of the housing based on a nonlinear relationship between a first temperature corresponding to a minimum rotation speed of the cooling fan and a second temperature corresponding to a maximum rotation speed of the cooling fan, and the duty ratio and a difference between the temperature of the housing and the first temperature; a fan control unit that controls rotation of the cooling fan based on the determined duty ratio; A fan control device comprising:

2. the nonlinear relationship is expressed by an equation having a finite power series of the difference, The equation has a linear relationship between the difference and the duty ratio in addition to the nonlinear relationship. The fan control device according to claim 1 .

3. The formula is The power series has a duty ratio corresponding to the minimum rotation speed as a first term, a first order coefficient of said difference, having a plurality of coefficients of the difference from second order onwards; The fan control device according to claim 2 .

4. When a basic setting is selected as the noise generated by the operation of the cooling fan, the plurality of coefficients from the second order onwards in the formula are set to zero, and the first order coefficient is set to a value corresponding to the basic setting; When a quiet setting is selected as the noise, the first-order coefficient in the formula is set to zero, and the second-order and subsequent coefficients are set to values ​​corresponding to the quiet setting. Further comprising a setting unit, the determination unit determines the duty ratio according to the temperature of the housing based on an equation using the set coefficient and the difference. The fan control device according to claim 3 .

5. The determination unit When the temperature of the housing is lower than the first temperature, a duty ratio corresponding to the minimum rotation speed is determined as a duty ratio related to control of rotation of the cooling fan; When the temperature of the housing is higher than the second temperature, a duty ratio corresponding to the maximum rotation speed is determined as a duty ratio related to control of rotation of the cooling fan; When a quiet setting is selected for the noise generated by the operation of the cooling fan, a duty ratio determined based on the temperature of the housing and the equation including the nonlinear relationship is compared with a duty ratio corresponding to the maximum rotation speed; When the determined duty ratio is greater than the duty ratio corresponding to the maximum rotation speed, the determination unit determines the duty ratio corresponding to the maximum rotation speed as the duty ratio related to the control of the rotation of the cooling fan. The fan control device according to any one of claims 1 to 4.

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