Abstract:
An information processing apparatus includes a cooling fan, a temperature acquiring unit, and a control unit configured to accelerate the cooling fan in an n-stage and to decelerate it in an m-stage more than the n-stage based on temperature acquired by the temperature acquiring unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-109173, filed Apr. 1, 2004, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an information processing apparatus, such as a personal computer having a cooling fan. In particular, the present invention relates to an information processing apparatus, which enables fan control of achieving both cooling performance traceability with rise in temperature, and reduction of non-continuous sound.  
         [0004]     2. Description of the Related Art  
         [0005]     In many cases, an information processing apparatus such as a personal computer is equipped with a cooling fan for releasing heat of a housing outside and blowing air toward exothermic objects. In general, this kind of information processing apparatus controls a cooling fan rate stepwise.  
         [0006]     Conventionally, stepwise rate control of the cooling fan has been carried out in the same manner in both cases where temperature rises and falls. For example, three-stage control means that both acceleration and deceleration of the cooling fan are controlled in three stages. For this reason, the following situation is given depending on load; more specifically, acceleration and deceleration are readily repeated. As a result, a non-continuous sound, such as an annoying noise is frequently made.  
         [0007]     In view of such circumstances, the following method has been proposed in order to reduce the non-continuous sound (e.g., see JPN. PAT. APPLN. KOKAI Publication No. 11-272365,). According to the method, if the cooling fan is operated at a low rate with a fall of temperature, deceleration is made only when a predetermined time or more elapses after a rate change is finally made.  
         [0008]     However, the cooling performance traceability in a rise of temperature required for the cooling fan must be preferentially taken into consideration. If multi-stage control is carried out, the rate difference caused between stages inevitably takes a large value to some degree. In other words, even if the method disclosed in the foregoing Publication No. 11-272365 is employed, the following problem arises. More specifically, when the cooling fan is decelerated, the rate difference becomes large (sudden change) before and after deceleration. For this reason, the reduction of non-continuous noise is not achieved even if deceleration is made while maintaining regular intervals or more.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     According to an embodiment of the present invention, an information processing apparatus comprises a cooling fan; a temperature acquiring unit; a first control unit configured to set a rate of the cooling fan to a first rate when a temperature acquired by the temperature acquiring unit exceeds a first temperature and the rate of the cooling fan is less than the first rate; a second control unit configured to set a rate of the cooling fan to a second rate faster than the first rate when the temperature acquired by the temperature acquiring unit exceeds a second temperature higher than the first temperature and the rate of the cooling fan is less than the second; and a third control unit configured to set the rate of the cooling fan so that the cooling fan is decelerated in a rate difference smaller than a rate difference between the first and second rates when the temperature acquired by the temperature acquiring unit is less than a third temperature lower than the first temperature and an elapsed time after the rate of the cooling fan is set to a current rate exceeds a predetermined time.  
         [0010]     According to an another embodiment of the present invention, an information processing apparatus comprises a cooling fan; a temperature acquiring unit; and a control unit configured to accelerate the cooling fan in an n-stage and to decelerate it in an m-stage more than the n-stage based on temperature acquired by the temperature acquiring unit.  
         [0011]     And according to an another embodiment of the present invention, a fan control method for an information processing apparatus having a cooling fan, comprises acquiring temperature; and controlling to accelerate the cooling fan in an n-stage and decelerate it in an m-stage more than the n-stage based on the acquired temperature. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0012]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0013]      FIG. 1  is a block diagram showing the configuration of a fan controller included in an information processing apparatus according to an embodiment of the present invention;  
         [0014]      FIG. 2  is a first graph to explain the operation principle of the fan controller included in the information processing apparatus according to the embodiment;  
         [0015]      FIG. 3  is a second graph to explain the operation principle of the fan controller included in the information processing apparatus according to the embodiment;  
         [0016]      FIG. 4  is a flowchart to explain fan control carried out by the information processing apparatus according to the embodiment;  
         [0017]      FIG. 5  is a flowchart to explain a first acceleration procedure taken by the information processing apparatus according to the embodiment;  
         [0018]      FIG. 6  is a flowchart to explain a second acceleration procedure taken by the information processing apparatus according to the embodiment;  
         [0019]      FIG. 7  is a flowchart to explain a deceleration procedure taken by the information processing apparatus according to the embodiment;  
         [0020]      FIG. 8  is a block diagram showing the configuration of another fan controller (modification example) included in the information processing apparatus according to the embodiment; and  
         [0021]      FIG. 9  is a flowchart to explain another deceleration procedure (modification example) taken by the information processing apparatus according to the embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     An embodiments of the present will be described below with reference to the accompanying drawings.  
         [0023]      FIG. 1  is a block diagram showing the configuration of a fan controller included in an information processing apparatus  100  according to an embodiment of the present invention. The information processing apparatus  100  is a desktop type personal computer, for example. As shown in  FIG. 1 , the apparatus  100  includes fan controller  1 , cooling fan  2 , temperature sensor  3  and clock module  4  in order to prevent the temperature of a housing from rising more than a predetermined reference.  
         [0024]     The fan controller  1  controls the rate of the cooling fan  2  based on temperature data acquired from the temperature sensor  3  and time data acquired from the clock module  4 . The fan controller  1  includes variable rate control unit  11 , digital-to-analog converter (DAC)  12  and memory unit  13 . Here, an example of acquiring temperature data from the temperature sensor  3  is given. In this case, the method of acquiring the temperature data is not limited to above, and any other methods are applicable. Likewise, an example of acquiring time data from the clock module  4  is given. Further, the method of acquiring the time data is not limited to above, and any other methods are applicable. In other words, the matters described above do not relate to the subject matter of the present invention described in this embodiment. In the following, temperature shown by the temperature data from the temperature sensor  3  is referred as T, and time shown by the time data from the clock module  4  is referred as t.  
         [0025]     The variable rate control unit  11  has first acceleration unit  111 , second acceleration unit  112  and deceleration unit  113 . These units each control the cooling fan  2 , with the result that they are unified as a system to control the cooling fan  2 . The operation principle for controlling the cooling fan  2  will be described later.  
         [0026]     The DAC  12  is a circuit for controlling a rate of the cooling fan  2  using voltage. The DAC  12  sets a rate of the cooling fan  2  based on instructions from the variable rate control unit  11 . Incidentally, any other methods and configurations may be used without being limited to above so long as the rate of the cooling fan  2  is set.  
         [0027]     The memory unit  13  is a rewritable storage medium such as flash memory. The memory unit  13  stores various information of fan rate group  131 , threshold value group  132 , setup value group  133  and status information group  134 . The fan rate group  131  is an aggregate of a fan rate in each stage for controlling the rate of the cooling fan  2  stepwise. In this case, the rate of the cooling fan  2  is controlled using eight (8) stages, and thus, eight (8) fan rates (R 1  to R 8 ) are defined. In  FIG. 1 , R 1  is the lowest rate while R 8  is the highest rate, thus the rate becomes gradually higher from R 1  toward R 8 .  
         [0028]     The threshold value group  132  is an aggregate of threshold values used for a comparison with temperature T in the foregoing first, second acceleration units  111 ,  112  and deceleration unit  113 . In  FIG. 1 , an acceleration threshold value T 1  is used for the first acceleration unit  111 . An acceleration threshold value T 2  is used for the second acceleration unit  112 . A deceleration threshold value T 3  is used for the deceleration unit  113 . In this case, a relation of T 3 &lt;T 1 &lt;T 2  is given.  
         [0029]     The setup value group  133  is an aggregate of index values when the foregoing first, second acceleration units  111 ,  112  and deceleration unit  113  control the cooling fan  2 . In  FIG. 1 , a fan rate Rh is a target fan rate when the first acceleration unit  111  accelerates the cooling fan  2 . A fan rate Rf is a target fan rate when the second acceleration unit  112  accelerates the cooling fan  2 . Hysteresis time Ht is an interval when the deceleration unit  113  decelerates the cooling fan  2  stepwise while maintaining a predetermined interval. The foregoing fan rates Rh and Rf are each stored with an identifier showing any of fan rates R 1  to R 8  of the fan rate group  131 . In this case, the fan rate Rh is stored with an identifier showing the fan rate R 5 ; on the other hand, the fan rate Rf is stored with an identifier showing the fan rate R 8 .  
         [0030]     The status information group  134  is an information aggregate for grasping control conditions of the cooling fan  2  by the first, second acceleration units  111 ,  112  and deceleration unit  113 . In  FIG. 1 , a current fan rate Rc holds a current rate (any of R 1  to R 8 ) of the cooling fan  2 . A fan rate setup time St holds time when the cooling fan  2  is set to the current rate.  
         [0031]     The operation principle of the fan controller  1  having the configuration described above will be described below with reference to  FIG. 2 . In the graph shown in  FIG. 2 , fan rate is shown on the vertical axis, and temperature on the horizontal axis.  
         [0032]     The temperature T shown by temperature data from the temperature sensor  3  rises (( 1 ) of  FIG. 2 ), and thereafter, exceeds the acceleration threshold value T 1  (( 2 ) of  FIG. 2 ). In this case, the first acceleration unit  111  determines whether or not the current fan rate Rc is lower than the fan rate Rh. If the current fan rate Rc is lower than the fan rate Rh, the first acceleration unit  111  takes the following procedures. More specifically, the unit  111  immediately accelerates the rate of the cooling fan to the fan rate Rh via the DAC  12 . Further, the unit  111  records the fan rate Rh as a current fan rate Rc while recording time t shown by time data acquired from the clock module  4  as a fan rate setup time St.  
         [0033]     Regardless of acceleration of the cooling fan  2 , the temperature T continues to rise, and then, exceeds the acceleration threshold value T 2  (( 2 ) of  FIG. 2 ). In this case, the second acceleration unit  112  determines whether or not the current fan rate Rc is lower than the fan rate Rf. If the current fan rate Rc is lower than the fan rate Rf, the second acceleration unit  112  follows the following procedure. More specifically, the unit  112  immediately accelerates the rate of the cooling fan to the fan rate Rf via the DAC  12 . Further, the unit  112  records the fan rate Rf as a current fan rate Rc while recording time t as a fan rate setup time St. In other words, the first and second acceleration units  111  and  112  carry out three-stage acceleration control of R 1 →R 5 →R 8  with respect to the cooling fan  2 .  
         [0034]     Thereafter, when the temperature T starts to drop (( 4 ) of  FIG. 2 ), it becomes less than the acceleration threshold values T 2  and T 1 . In this case, the rate of the cooling fan  2  continues to be maintained to the fan rate Rf (i.e., fan rate R 8 ). The temperature rises exceeding the acceleration threshold value T 1 , and thereafter, falls without exceeding the acceleration threshold value T 2 . In this case, the rate of the cooling fan  2  continues to be maintained at the fan rate Rh (i.e., fan rate R 5 ). Then, when the temperature becomes less than the deceleration threshold value T 3 , the deceleration unit  113  determines whether or not a time difference from time elapsed from the fan rate setup time St, that is, time t exceeds hysteresis time Ht. If the time difference exceeds the hysteresis time Ht, the deceleration unit  113  acquires a fan rate value of one stage lower than the current fan rate Rc from the fan rate group  131 . Then, the deceleration unit  113  decelerates the rate of the cooling fan  2  to the above-mentioned fan rate via the DAC  12 . Simultaneously, the deceleration unit  113  records the fan rate as a current fan rate Rc while recording time t as a fan rate setup time St. The procedure described above is taken, and thereby, deceleration of R 8 →R 7  is made.  
         [0035]     Since the elapsed time from the fan rate setup time St soon exceeds the hysteresis time Ht, the deceleration unit  113  makes deceleration of R 7 →R 6  according to the same procedure as above. In other words, the deceleration unit  113  carries out eight-stage deceleration control of R 8 →R 7 →R 6 →R 5 →R 4 →R 3 →R 2 →R 1  with respect to the cooling fan  2  while keeping the hysteresis time Ht.  
         [0036]     The variable rate control unit  11  has first, second acceleration units  111 ,  112  and deceleration unit  113 , which each control the cooling fan  2  in the manner described above. The variable rate control unit  11  is used, and thereby, the fan controller  1  controls the cooling fan  2  while realizing both cooling performance traceability in a rise of temperature and reduction of non-continuous sound.  
         [0037]     In a zone A of  FIG. 2 , eight-stage deceleration is made; therefore, any one of fan rates R 1  to R 8  is capable of being set as the rate of the cooling fan  2 . Likewise, in a zone B of  FIG. 2 , any one of fan rates R 1  to R 8  is capable of being set as the rate of the cooling fan  2 . This is because deceleration to a certain fan rate is made in the zone A, and thereafter, the temperature T again exceeds the deceleration threshold value T 3 . On the other hand, in a zone C of  FIG. 2 , the rate of the cooling fan  2  is set within a range from fan rate R 5  to R 8 . The fan rates R 5  and R 8  has no need of explanation. The fan rates R 6  and R 7  correspond to the case where deceleration to the fan rates R 6  and R 7  is made in the zone A, and thereafter, the temperature T again exceeds the acceleration threshold value T 1 .  
         [0038]      FIG. 4  to  FIG. 7  is a flowchart to explain the operation procedure relevant to fan control by the information processing apparatus  100  of this embodiment.  
         [0039]      FIG. 4  is a flowchart to explain the entire flow of fan control carried out by the information processing apparatus  100 . The following procedures are successively and repeatedly taken while the information processing apparatus  100  is operating. One is a first acceleration procedure (step A 1 ) by the first acceleration unit  111  of the variable rate control unit  11 . Another is a second acceleration procedure (step A 2 ) by the second acceleration unit  112 , and further, another is a deceleration procedure (step A 3 ) performed by the deceleration unit  113 .  
         [0040]      FIG. 5  is a flowchart to explain the flow of the first acceleration procedure by the first acceleration unit  111  of the variable rate control unit  11 .  
         [0041]     The first acceleration unit  111  determines whether or not temperature T exceeds the acceleration threshold value T 1  (step B 1 ). If the temperature T exceeds the acceleration threshold value T 1  (YES in step B 1 ), the unit  111  determines whether or not the current fan rate Rc is lower than the fan rate Rh (step B 2 ). If the current fan rate Rc is lower than the fan rate Rh (YES in step B 2 ), the unit  111  immediately sets the rate of the cooling fan  2  to the fan rate Rh (step B 3 ). Thereafter, the unit  111  updates the current fan rate Rc as fan rate Rh while updating the fan rate setup time St as time t (step B 4 , B 5 ).  
         [0042]     The unit  111  makes an operation of setting the rate of the cooling fan  2  to the fan rate Rh only when the current fan rate Rc is lower than the fan rate Rh according to the determination of step B 2 . Therefore, the first acceleration procedure does not conflict with control of the cooling fan  2  performed by the second acceleration unit  112 .  
         [0043]      FIG. 6  is a flowchart to explain the flow of the second acceleration procedure by the first acceleration unit  112  of the variable rate control unit  11 .  
         [0044]     The second acceleration unit  112  determines whether or not temperature T exceeds the acceleration threshold value T 2  (step C 1 ). If the temperature T exceeds the acceleration threshold value T 2  (YES in step C 1 ), the unit  112  determines whether or not the current fan rate Rc is lower than the fan rate Rf (step C 2 ). If the current fan rate Rc is lower than the fan rate Rf (YES in step C 2 ), the unit  112  immediately sets the rate of the cooling fan  2  to the fan rate Rf (step C 3 ). Thereafter, the unit  112  updates the current fan rate Rc as fan rate Rf while updating the fan rate setup time St as time t (step C 4 , C 5 ).  
         [0045]     As described above, the first and second acceleration units  111  and  112  immediately carry out acceleration control. Therefore, cooling performance traceability during a rise of temperature is secured.  
         [0046]      FIG. 7  is a flowchart to explain the flow of the deceleration procedure performed by the deceleration unit  113  of the variable rate control unit  11 .  
         [0047]     The deceleration unit  113  determines whether or not temperature T is less than the deceleration threshold value T 3  (step D 1 ). If the temperature T is less than the deceleration threshold value T 3  (YES in step D 1 ), the unit  113  determines whether or not time exceeding hysteresis time Ht elapses from the fan rate setup time St (step D 2 ). If the time exceeds the hysteresis time Ht (YES in step D 2 ), the unit  113  determines whether or not the current fan rate Rc is the lowest fan rate, that is, the fan rate R 1  (step D 3 ). Determination in step D 2  is given, and thereby, reduction of non-continuous sound is realized.  
         [0048]     If the current fan rate Rc is not the fan rate R 1  (NO in step D 3 ), the deceleration unit  113  decelerates the rate of the cooling fan  2  by one stage (step D 4 ). The unit  113  updates the current fan rate Rc as a fan rate (Rc−1) after one-stage deceleration while updating the fan rate setup time St as time t (step D 5 , D 6 ).  
         [0049]     As described above, the deceleration unit  113  makes deceleration while keeping the interval of hysteresis time Ht. By doing so, it is possible to secure cooling performance traceability during a rise in temperature and reduction of non-continuous sound.  
         [0050]     In this embodiment, two cases are given as described above. According to one case, temperature T exceeds the acceleration threshold value T 1 , and the cooling fan  2  is accelerated to the fan rate Rh. Thereafter, by the preceding acceleration, the temperature T becomes less than the deceleration threshold value T 3 . According to another case, the temperature T further exceeds the acceleration threshold value T 2 , and the cooling fan  2  is accelerated to the fan rate Rf. Thereafter, by the preceding acceleration, the temperature T becomes less than the deceleration threshold value T 3 . In the former case, deceleration of the cooling fan  2  is started if the elapsed time after the first acceleration unit  111  records the fan rate setup time St exceeds hysteresis time Ht. In the latter case, deceleration of the cooling fan  2  is started if the elapsed time after the second acceleration unit  112  records the fan rate setup time St exceeds hysteresis time Ht. The following is a description of the case given below. That is, the deceleration of the cooling fan  2  is started at timing when the elapsed time after temperature T becomes less than the deceleration threshold value T 3  exceeds hysteresis time Ht.  
         [0051]     Thus, the memory unit  13  of the fan controller  1  holds a fan rate setup flag Fg as one of the status information group  134  as seen from  FIG. 8 . More specifically, the first and second acceleration units  111  and  112  set the current fan rate Rc to the fan rate Rh or Rf. In this case, these units  111  and  112  set the fan rate setup flag Fg in addition to setting of the time t to the fan rate setup time St in step C 5  of  FIG. 6  or step D 6  of  FIG. 7 . On the other hand, the deceleration unit  113  is operated according to the flow shown in  FIG. 9  using the fan rate setup flag Fg.  
         [0052]     The deceleration unit  113  determines whether or not temperature T becomes less than the deceleration threshold value T 3  (step E 1 ). If the temperature T is less than the deceleration threshold value T 3  (YES in step E 1 ), the unit  113  determines whether or not the fan rate setup flag Fg is set (step E 2 ). If the fan rate setup flag Fg is set (YES in step E 2 ), the deceleration unit  113  updates the fan rate setup time St to time t (step E 3 ), and then, does not set the fan rate setup flag Fg (step E 4 ). In other words, the fan rate setup flag Fg is used, and thereby, it is possible to recognize the timing when the temperature T becomes less than deceleration threshold value T 3 .  
         [0053]     On the other hand, if the fan rate setup flag Fg is not set (NO in step E 2 ), the unit  113  determines whether or not the elapsed time from the fan rate setup time St exceeds the hysteresis time Ht (step E 5 ). If the time exceeds the hysteresis time Ht, (YES in step E 5 ), the unit  113  determines whether or not the current fan rate Rc is the lowest rate, that is, the fan rate R 1  (step E 6 ).  
         [0054]     If the current fan rate Rc is not the fan rate R 1  (NO in step E 6 ), the deceleration unit  113  decelerates the rate of the cooling fan  2  by one state (step E 7 ). Then, the deceleration unit  113  updates the current fan rate Rc to a fan rate (Rc−1) after one-stage deceleration while updating the fan rate setup time St to time t (step E 8 , E 9 ).  
         [0055]     The fan rate setup flag Fg is newly provided in order to obtain the deceleration start timing of the cooling fan  2  when the elapsed time after temperature T becomes less than the deceleration threshold value T 3  exceeds the hysteresis time Ht. In this case, any other configuration and principle may be employed so long as the foregoing purpose is achieved.  
         [0056]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.