Patent Publication Number: US-6698403-B2

Title: Fuel vapor adsorption device of internal combustion engine and method of desorbing fuel vapor from fuel vapor adsorbent

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2001-297678 filed on Sep. 27, 2001, including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a fuel vapor adsorption apparatus disposed in an intake air passage of an internal combustion engine in order to adsorb fuel vapor and a method of desorbing fuel vapor from a fuel vapor adsorbent. 
     2. Description of Related Art 
     As regulations on fuel vapor (hereinafter referred to as “HCs”) discharged from a motor vehicle while the vehicle is stopped become more and more stringent, it has become a major issue that HCs diffuse and leak through an inlet port into the atmosphere while the vehicle is stopped. HCs are generated when residual fuel left in an engine and fuel that leaks from an injector vaporize. There has been devised a device, in which an HC adsorbent in the form of, for example, a filter accommodating an active carbon is disposed in a partial or entire surface of a cross section of an intake passage, such as an intake duct, an air cleaner, or the like, to adsorb HCs and thereby prevent HCs from leaking out through the intake port. 
     According to the device, the adsorbent is purged by air which is drawn in while the vehicle is operating such that HCs previously adsorbed while the vehicle was stopped are desorbed, thereby recovering the adsorption performance of the adsorbent. Thus, the adsorbent can effectively adsorb HCs when the vehicle is stopped the next time. However, the intake air may not be in uniform contact with the adsorbent and if the amount of the intake air is small depending on an operating state of the engine, HCs adsorbed by the adsorbent may not be completely purged. In this case, the adsorbent lacks a sufficient adsorption capacity when the vehicle is stopped the next time. As a result, HCs may leak through the intake port. 
     There is a known device as disclosed in Japanese Utility Model Laid-Open Publication No. 62-184162, in which an adsorbent provided in an air cleaner is heated to recover the adsorbent. However, since the arrangement has been devised for preventing icing, what is adsorbed by the adsorbent is water content in the air. The control of heating the adsorbent presented in this arrangement is not suited for the desorption of HCs as an object of the invention. Moreover, heating the adsorbent at all times aggravates fuel economy and should be avoided as much as possible. 
     SUMMARY OF THE INVENTION 
     The inventors have been paying attention to the fact that desorption of HCs adsorbed by an active carbon is promoted under a low pressure or a high temperature condition. At the time of desorption of HCs from the active carbon, HCs adsorbed through liquefaction are desorbed through vaporization. Desorption performance is therefore enhanced under a condition that allows HCs to vaporize easily (high temperature, low pressure). According to the invention, therefore, the desorption performance is enhanced by, reducing the pressure of the place in which the HC adsorbent is disposed, and/or heating the intake air or the HC adsorbent (it is desirable that the air or material be heated to a level of a typical boiling point of a fuel or higher) while the vehicle is operating (or during desorption). This approach makes it possible to efficiently desorb HCs from the adsorbent even with a small amount of air. 
     A first aspect of the invention relates to a fuel vapor adsorption apparatus of an internal combustion engine. The apparatus includes an adsorbent, disposed on at least a part of a cross section of an intake air passage of the internal combustion engine, that adsorbs fuel vapor, and an adjustment device, disposed upstream of the adsorbent in the intake air passage, that adjusts the amount of the intake air. The apparatus includes a controller that controls the adjustment device to place the adsorbent in a more vacuum condition than condition during an ordinary control of the internal combustion engine, under the same operating state but where fuel vapor is not being desorbed from the adsorbent, by regulating the amount of the intake air while a control is provided to desorb fuel vapor from the adsorbent. 
     As a result, by controlling the controller of the adjustment device (for example, an intake throttle valve), the adsorbent when purged, is placed in the more vacuum condition than a condition during the ordinary control where fuel vapor is not desorbed from the adsorbent, as compared to the internal combustion engine the same operation state, under but when description is not taking place. This promotes desorption of HCs. 
     A second aspect of the invention relates to a fuel vapor adsorption apparatus of an internal combustion engine. The apparatus includes an adsorbent, disposed in at least a part of a cross section of an intake air passage of the internal combustion engine, and a heading device. The adsorbent adsorbs fuel vapor. The heating device heats the adsorbent. The apparatus includes a controller that controls the heating device to adjust a heating amount for heating the adsorbent during a desorbing control of the internal combustion engine for desorbing fuel vapor from the adsorbent. The fuel vapor is described in accordance with the amount of the intake air passing through the intake air passage of the internal combustion engine. 
     In the second aspect, because the heating amount is controlled in accordance with the amount of the intake air passing through the intake air passage, it is possible to efficiently desorb HCs from the adsorbent. 
     A third aspect of the invention relates to a method of desorbing fuel vapor from an absorbent that adsorbs the fuel vapor and is disposed on at least part of a cross section of an intake air passage of an internal combustion engine. The method includes the step of determining whether a condition for desorbing fuel vapor from the adsorbent is met, and placing the adsorbent, if it is determined that the condition for desorbing fuel vapor from the adsorbent is met, in a more vacuum condition than during an ordinary control of the internal combustion engine under the same operating condition but where fuel vapor is not desorbed from the adsorbent. 
     In the third aspect, it is possible to efficiently desorb HCs from the adsorbent because the adsorbent is placed in the more vacuum condition if it is determined that the condition for desorbing fuel vapor from the adsorbent is met, than during the ordinary control of the internal combustion engine under the same operating state. 
     A fourth aspect of the invention relates to a method of desorbing fuel vapor from an adsorbent that adsorbs the fuel vapor and that is disposed on at least part of a cross section of an intake air passage of an internal combustion engine. The method includes the steps of determining whether a condition for desorbing fuel vapor from the adsorbent is met, determining an amount of the intake air required by the internal combustion engine, and increasing a heating amount for heating the adsorbent based on the determined amount of the intake air, if it is determined that the condition for desorbing fuel vapor from the adsorbent is met. The heating amount increases as the determined amount of the intake air decreases. 
     In the fourth aspect, because the heating amount is controlled in accordance of the intake air passing through the intake air passage, it possible to efficiently desorb HCs from the adsorbent. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein: 
     FIG. 1 is a system configuration diagram of a device according to a first embodiment of the invention; 
     FIG. 2 is a flowchart showing a control routine according to the first embodiment of the invention; 
     FIG. 3 is a system configuration diagram of a device according to a second embodiment of the invention; 
     FIG. 4 is a system configuration diagram of a device according to a third embodiment of the invention; 
     FIG. 5 is a system configuration diagram of a device according to a fourth embodiment of the invention; 
     FIG. 6 is a system configuration diagram of a device according to a fifth embodiment of the invention; 
     FIG. 7 is a flowchart showing a control routine according to the second embodiment and the fifth embodiment of the invention; 
     FIG. 8 is a flowchart showing a control routine according to the third embodiment of the invention; 
     FIG. 9 is a system configuration diagram of a device as a modified example of the third embodiment of the invention; 
     FIG. 10A is an enlarged front elevational view showing a principal part of the device according to the fourth embodiment of the invention; 
     FIG. 10B is an enlarged side cross-sectional view showing a principal part of the device according to the fourth embodiment of the invention; 
     FIG. 11 is a flowchart showing a control routine according to the fourth embodiment of the invention; 
     FIG. 12A is an enlarged front elevational view showing a principal part of a first modified example according to the fourth embodiment of the invention; 
     FIG. 12B is an enlarged side cross-sectional view showing a principal part of the first modified example according to the fourth embodiment of the invention; 
     FIG. 13A is an enlarged front elevational view showing a principal part of a second modified example according to the fourth embodiment of the invention; 
     FIG. 13B is an enlarged side cross-sectional view showing a principal part of the second modified example according to the fourth embodiment of the invention; 
     FIG. 14A is an enlarged front elevational view showing a principal part of the device according to the fifth embodiment of the invention; 
     FIG. 14B is an enlarged side cross-sectional view showing a principal part of the device according to the fifth embodiment of the invention; 
     FIG. 15 is a flowchart showing a control routine according to the fifth embodiment of the invention; and 
     FIG. 16 is a flowchart showing a modified example of the control routine according to the fifth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The first embodiment according to the invention will be explained with reference to FIG.  1 . An air cleaner  21  is installed in an intake pipe  2  of an internal combustion engine (engine)  1 . The air cleaner  21  is provided therein with an air filter  22  having a function of filtering an intake air and an adsorption sheet  3  having a function of adsorbing HCs. The adsorption sheet  3  is disposed on a clean side of the air filter  22  (on a side of a main body of the engine  1 ) so as to prevent it from being plugged up by dust or other problem. The adsorption sheet  3  has a construction in which an adsorbent (for example, active carbon)  31  is sandwiched between two meshes  32 . The mesh size of the mesh is set such that granular powders of the active carbon  31  do not drop through the mesh and the mesh meets an allowable pressure loss value. An intake throttle valve  61  regulates the amount of the intake air upstream of the air cleaner  21 . The intake throttle valve  61  is set such at it does not, even when closed, make the intake pipe  2  airtight and thus allows air to flow therethrough so as to secure an amount of the intake air required when the engine  1  is operating at low revolution speeds or under low loads such that it ensures that there is a certain degree of vacuum in the areas around the adsorption sheet  3  which is located downstream of the intake throttle valve  61 . An opening of the intake throttle valve  61  is controlled by an electronic control device (ECU)  7 . An ordinary intake throttle valve  6  is provided downstream of the adsorption sheet  3 . 
     The operation of the first embodiment according to the invention will be explained. HCs adsorbed onto the adsorption sheet  3  are easy to desorb if a condition that makes the HCs easy to vaporize is established. Therefore, if a vacuum is created in areas around the adsorption sheet  3 , desorption of HCs will be promoted. The opening of the intake throttle valve  61  is therefore made small during purging, thereby allowing a vacuum to be created in areas around the adsorption sheet  3  downstream of the intake throttle valve  61  for promotion of desorption of HCs. As described earlier, when the engine is operating at low revolution speeds or under low loads, the amount of the intake air is small and HCs are hard to desorb. Control is therefore provided to close the intake throttle valve  61  such that a vacuum is created in areas around the adsorption sheet  3 , thereby promoting desorption. As noted earlier, the opening of the intake throttle valve  61 , when closed, is set so as to secure the amount of the intake air required when the engine is operating at low revolution speeds or under low loads. Therefore, closing of the intake throttle valve  61  has substantially no effect on the engine  1 . 
     Since a large amount of the intake air is required when the engine is operating at high revolution speeds or under heavy loads, closing of the intake throttle valve  61  would inhibit intake of air, thus adversely affecting engine operations. The intake throttle valve  61  is therefore opened in such an operating state. At this time, there is a large amount of the intake air, which sets a condition, in which HCs are easy to desorb from the adsorption sheet  3 . Therefore, it is possible for HCs to desorb satisfactorily even without a vacuum being created in areas around the adsorption sheet  3 . 
     A routine executed by the ECU  7  to control the intake throttle valve  61  in such a manner as described in the foregoing paragraphs will be explained with reference to the flowchart shown in FIG.  2 . When it is determined that the engine  1  is started to operate as IG (ignition switch) is turned ON (step  101 ), control of the intake throttle valve  61  is started. Since the engine  1  is operating at low revolution speeds or under low loads at a timing immediately after the start, the intake throttle valve  61  is closed in step  102 . It is then determined, in step  103 , whether or not the engine  1  has stopped. If the engine  1  has stopped (Yes), the control proceeds to step  110 , in which the intake throttle valve  61  is opened and control is terminated. If the engine  1  has not stopped (No), the control proceeds to step  104 . 
     In step  104 , an engine revolution speed N or a load T at the current time is measured/determined. The engine revolution speed N or load T is measured/determined, for example, by the revolution speed sensor of the engine  1 , the opening of the intake throttle valve  6 , signals indicating other engine operating states, and signals controlling the engine  1 . 
     In subsequent step  105 , it is determined whether or not the engine revolution speed N or the load T at the current timing is equal to or greater than predetermined values N 0  and T 0 , respectively. If N≧N 0  (or T≧T 0 ) is not true (No), it is determined that the engine  1  is still operating at low revolution speeds or under low loads and the control returns to step  103 . 
     If N≧N 0  (or T≧T 0 ) is true (Yes), it is determined that the engine  1  is operating at high revolution speeds or under heavy loads and the control proceeds to step  106 , in which the intake throttle valve  61  is opened. In subsequent step  107 , it is determined whether or not the engine  1  has stopped. If it is determined that the engine  1  has stopped (Yes), the control proceeds to step  110 , in which the intake throttle valve  61  is opened and the control is terminated. 
     If it is determined that the engine  1  has not stopped (No), the control proceeds to step  108 , in which the engine revolution speed N or the load T at the current timing is measured/determined by, for example, the revolution speed sensor of the engine  1 , the opening of the intake throttle valve  6 , signals indicating other engine operating states, signals controlling the engine  1 . 
     In subsequent step  109 , it is determined whether or not the engine revolution speed N or the load T at the current timing is equal to or greater than the predetermined values N 0  and T 0 . If N≧N 0  (or T≧T 0 ) is true (Yes), it is determined that the engine  1  is still operating at high revolution speeds or under heavy loads and the control returns to step  107 . If N≧N 0  (or T≧T 0 ) is not true (No), it is determined that the engine  1  is now operating at low revolution speeds or under low loads and the control returns to step  102 . 
     The amount of air required by the engine  1  may be obtained based on the engine revolution speed N or the load T at the current timing measured/determined by, for example, the revolution speed sensor of the engine  1 , the opening of the intake throttle valve  6 , signals indicating other engine operating states, signals controlling the engine  1 . The opening of the intake throttle valve  61  may be determined in accordance with the obtained required amount of air. 
     A variety of heating devices are available for heating the adsorbent, including a burning type heater that heats the intake air used for desorbing HCs through heating of the adsorbent, drawing in hot air, directly heating the adsorbent using a hot engine coolant, and an electrical heater heating the adsorbent. These devices are shown in FIGS. 3 through 6 and will be sequentially explained as a second embodiment through a fifth embodiment according to the invention. It is to be understood that the heating devices for the adsorbent are not limited to these arrangements and that heaters of other types may be used. 
     A fuel vapor adsorption apparatus according to the second embodiment of the invention will be explained with reference to FIG.  3 . An air cleaner  21  is installed in an intake pipe  2  of an engine  1 . The air cleaner  21  is provided therein with an air filter  22  that filters intake air and an adsorption sheet  3  that adsorbs HCs. The adsorption sheet  3  is disposed on a clean side of the air filter  22  (on a side of a main body of the engine  1 ) so as to prevent it from being plugged up by dust or other problem. The adsorption sheet  3  has a construction in which an adsorbent (for example, active carbon)  31  is sandwiched between two meshes  32 . The mesh size of the mesh  32  is set such that granular powders of the active carbon  31  do not drop through the mesh  32  and the mesh  32  meets an allowable pressure loss value. A burning type heater  41 , as a specific example of a heating device for heating the adsorbent  31  by heating of the intake air, is disposed upstream of the air cleaner  21 . The burning type heater  41  is disposed at a position, at which a flame thereof does not reach the air filter  22 . Driving of the burning type heater  41  is controlled by an ECU  7 . 
     The operation of the second embodiment according to the invention will be explained. When an air drawn in through an inlet port during an operation of the engine  1  moves through the air filter  22  and the adsorption sheet  3 , part of HCs, adsorbed by the adsorbent  31  composed of active carbon, are purged by the air. When the burning type heater  41  is driven, the intake air is heated by the burning type heater  41 , which increases the temperature of the air moving through the adsorption sheet  3 . This helps make HCs adsorbed onto the adsorbent  31  easy to vaporize. As a result, desorption of HCs is promoted and it is possible to efficiently purge HCs with an amount of air smaller than when the intake air is not heated. It is more effective if the heating temperature of the burning type heater  41  is set so as to make the temperature of the intake air at a level of a typical boiling point of fuel (for example 60° C.) or higher. 
     As described earlier, HCs are hard to desorb, if no measure is taken, from the adsorbent  31  when the engine is operating at low revolution speeds or under low loads, as in the case with creating a certain degree of vacuum in areas around the adsorption sheet  3  downstream of the intake throttle valve  61  (the first embodiment). Therefore, according to the second embodiment of the invention, the burning type heater  41  is driven to heat the intake air, which promotes desorption of HCs. 
     On the contrary, HCs are easy to desorb when the engine is operating at high revolution speeds or under heavy loads, and therefore, in such conditions, the burning type heater  41  is stopped. In addition, the control according to the second embodiment has added values. For example, drawing in high temperature air under a condition of low loads promotes atomization of injected fuel flowing in the engine  1  and thus reduces exhaust emissions. Drawing in low temperature air under a condition of heavy loads improves charging efficiency for an increased power output. Further, the reduced intake air temperature suppresses self ignition, thus preventing knocking. The control according to the second embodiment is therefore advantageous also from the viewpoint of engine operations. 
     The control according to the second embodiment will be explained with reference to FIG.  7 . When it is determined that operation of the vehicle is started as IG (ignition switch) is turned ON (in step  201 ), control of the burning type heater  41  is started. Since the engine  1  is operating at low revolution speeds or under low loads at a timing immediately after the start, the burning type heater  41  is driven in step  202 . 
     In subsequent step  203 , it is determined whether or not the engine  1  has stopped. If the engine  1  has stopped (Yes), the control proceeds to step  210 , in which the burning type heater  41  is stopped and control is terminated. If the engine  1  has not stopped (No), the control proceeds to step  204 , in which an engine revolution speed N or a load T at the current timing is measured/determined by, for example, the revolution speed sensor of the engine  1 , the opening of the intake throttle valve  6 , signals indicating other engine operating states, signals controlling the engine  1 . 
     In subsequent step  205 , it is determined whether or not the engine revolution speed N or the load T at the current timing is equal to or greater than the predetermined values N 0  and T 0 , respectively. If N≧N 0  (or T≧T 0 ) is not true (No), it is determined that the engine  1  is still operating at low revolution speeds or under low loads and the control returns to step  203 . 
     If N≧N 0  (or T≧T 0 ) is true (Yes), it is determined that the engine  1  is now operating at high revolution speeds or under heavy loads and the control proceeds to step  206 , in which the burning type heater  41  is stopped. In subsequent step  207 , it is then determined whether or not the engine  1  has stopped. If it is determined that the engine  1  has stopped (Yes), the control proceeds to step  210 , in which the burning type heater  41  is stopped and the control is terminated. If it is determined that the engine  1  has not stopped (No), the control proceeds to step  208 , in which the engine revolution speed N or the load T at the current timing is measured/determined by, for example, the revolution speed sensor of the engine  1 , the opening of the intake throttle valve  6 , signals indicating other engine operating states, signals controlling the engine  1 . 
     In step  209 , it is determined whether or not the engine revolution speed N or the load T at the current timing is equal to or greater than the predetermined values N 0  and T 0 . If N≧N 0  (or T≧T 0 ) is true (Yes), it is determined that the engine  1  is still operating at high revolution speeds or under heavy loads and the control returns to step  207 . If N≧N 0  (or T≧T 0 ) is not true (No), it is determined that the engine  1  is now operating at low revolution speeds or under low loads and the control returns to step  202 . 
     A fuel vapor adsorption apparatus according to the third embodiment of the invention will be explained with reference to FIG.  4 . According to the third embodiment, a hot air passage  53  is installed, with one end opened to an area around an engine  1  so as to take in hot air surrounding the engine  1  and the other end connected to an intake pipe  2  upstream of an air cleaner  21 . Also, a selector valve  51  is installed at a connection portion between the hot air passage  53  and the intake pipe  2 . The selector valve  51  is connected to a motor  57  that is driven as controlled by an ECU  7 . For the sake of convenience, an intake pipe upstream of the selector valve  51  is called herein a cool air passage  55 . 
     The operation of the third embodiment according to the invention will be explained. As evident from the foregoing descriptions, it is desirable that hot air be drawn in while the engine  1  is operating at low revolution speeds or under low loads and cool air be drawn in while the engine  1  is operating at high revolution speeds or under heavy loads. According to the third embodiment, therefore, the selector valve  51  is moved in a direction to open the hot air passage  53  when the engine  1  is operating at low revolution speeds or under low loads. This results in the hot air surrounding the engine  1  being drawn in, which promotes purging of an adsorption sheet  3 . When the engine  1  is operating at high revolution speeds or under heavy loads, on the other hand, the selector valve  51  is moved in a direction to open the cool air passage  55 . As a result, the cool air is drawn into the engine  1 . However, since the amount of the intake air is large, the adsorption sheet  3  can be sufficiently purged even with the cool air. 
     The control according to the third embodiment is shown in FIG.  8 . The steps shown in FIG. 8 are substantially the same as those shown in FIG. 7 that shows the control according to the second embodiment as described above, except that driving of the heater  41  in step  202  is replaced by opening of the hot air passage  53  in step  302  and that stopping of the heater  41  is replaced by opening of the cool air passage  55 . When it is determined that the vehicle has been started as the result of IG being turned ON (in step  301 ), the selector valve  51  is moved in a direction to open the hot air passage  53  in step  302 . If it is determined that N≧N 0  (or T≧T 0 ) is true (Yes) in step  305 , it is determined that the engine  1  is now operating at high revolution speeds or under heavy loads and the control proceeds to step  306 , in which the selector valve  51  is moved in a direction to open the cool air passage  55 . Detailed explanations of FIG. 8 will be omitted. Though the motor  57  is used to drive the selector valve  51  in FIG. 4, an arrangement may be used as a modified example of the third embodiment as shown in FIG. 9, in which the selector valve  51  is driven by an actuator  52  that is operated by an intake pipe vacuum. In this case, the actuator  52  opens the hot air passage  53  when the engine  1  is operating at low revolution speeds or under low loads. 
     A fuel evaporate adsorption apparatus according to the fourth embodiment of the invention will be explained with reference to FIG.  5 . In this arrangement, too, an air cleaner  21  is installed in an intake duct  2  of an engine  1  and the air cleaner  21  is provided therein with an air filter  22  that filters intake air and an adsorption sheet  3  that adsorbs HCs. FIGS. 10A and 10B show the construction of the adsorption sheet  3  that characterizes the fourth embodiment of the invention. The adsorption sheet  3  has a construction in which an adsorbent  31  (for example, an active carbon) that adsorbs HCs is sandwiched between two meshes  32 , and fixed in position by mounting the sheets of the mesh  32  by way of a supporting frame  33  to the air cleaner  21 . 
     The mesh size of the mesh  32  is set such that granular powders of the active carbon  31  do not drop through the mesh and the mesh meets an allowable pressure loss value. Inside the supporting frame  33 , a water passage  34  is formed, connected to an outside by way of ports  35 ,  36  on both ends thereof. Referring to FIG. 5, the port  35  is connected to a water jacket of the engine  1  through a water passage  81 . The port  36  is connected to a radiator (not shown) through a water passage  82 . Valves  83  and  84  are provided in the middle of the water passages  81 ,  82  to cut off the water passages. The valves  83  and  84  are opened and closed as controlled by an ECU  7 . It is good enough even if either the valve  83  or the valve  84  only is installed. 
     The operation of the fourth embodiment will be explained. As described earlier, it is desirable that high temperature air be drawn in while the engine  1  is operating at low revolution speeds or under low loads and low temperature air be drawn in while the engine  1  is operating at high revolution speeds or under heavy loads. Therefore, the engine revolution speed N or the load T at the current timing is measured as in the first embodiment, and valves  83 ,  84  are opened if the engine  1  is operating at low revolution speeds or under low loads. Since the coolant is hot enough to exceed a typical boiling point of fuel (for example 60° C.) under ordinary engine operating states, the adsorption sheet  3  is heated by the heat of the coolant. Moreover, the intake air is also heated as it passes through the adsorption sheet  3 , which means that the engine  1  draws in high temperature air. If the engine  1  is operating at high revolution speeds or under heavy loads, the valves  83 ,  84  are closed. This stops heating the adsorption sheet  3  and thus the engine  1  draws in low temperature air. 
     FIG. 11 shows the control of the fourth embodiment according to the invention. The steps shown in FIG. 11 are substantially the same as those shown in FIG. 7 that shows the control according to the second embodiment, except that driving of the heater  41  is replaced by opening of the valves  83  and  84  and that stopping of the heater  41  is replaced by closing of the valves  83  and  84 . Namely, when it is determined that the vehicle has been started as the result of IG being turned ON (in step  401 ), the valves  83  and  84  are opened in step  402  such that the adsorption sheet  3  is heated by the heat of the coolant. If it is determined that N≧N 0  (or T≧T 0 ) is true (Yes) in step  405 , it is determined that the engine  1  is now operating at high revolution speeds or under heavy loads and the control proceeds to step  406 , in which the valves  83  and  84  are closed. Detailed explanations of FIG. 11 will be omitted. 
     Though a fuel evaporating adsorption apparatus according to the fourth embodiment has the arrangement, in which coolant flows through only the inside of the supporting frame  33 , a water passage  37  can also be provided on a surface of the mesh  32  as in a first modified example of the fourth embodiment as shown in FIG. 12. A water passage can also be provided, for example, between active carbons  31  as in a second modified example of the fourth embodiment as shown in FIG.  13 . This permits even more efficient temperature regulation for the active carbon  31  and intake air, thus leading to enhanced performance. 
     A fuel evaporate adsorption apparatus according to the fifth embodiment of the invention will be explained with reference to FIG.  6 . An air cleaner  21  is installed in an intake duct  2  of an engine  1 . The air cleaner  21  is provided therein with an air filter  22  that filters intake air and an adsorption sheet  3  that adsorbs HCs. FIGS. 14A and 14B show the specific construction of the adsorption sheet  3 . An electrical heater  9  composed of a resistor wire is embedded inside a supporting frame  33  of the adsorption sheet  3 . The heater  9  is energized so as to generate heat, thereby heating an active carbon  31 . Driving of the heater  9  is controlled by an ECU  7 . Installing the adsorption sheet  3  and the heater  9  inside the air cleaner  21  as described above makes it possible to build the entire fuel vapor adsorption apparatus compact. 
     The operation of the fifth embodiment according to the invention will be explained. As explained earlier, it is desirable that a high temperature air be drawn in when the engine  1  is operating at low revolution speeds or under low loads and a low temperature air be drawn in when the engine  1  is operating at high revolution speeds or under heavy loads. In the same manner as in the first embodiment according to the invention, an engine revolution speed N or a load T at the current timing is measured and, if it is found that the engine  1  is operating at low revolution speeds or under low loads, then the heater  9  is energized to heat the adsorption sheet  3 . Moreover, since the intake air is heated as it passes through the heated adsorption sheet  3 , the engine  1  draws in a high temperature air. If the engine  1  is operating at high revolution speeds or under heavy loads, the heater  9  is stopped. This stops heating the adsorption sheet  3 , which results in the engine  1  drawing in low temperature air. The control routine for the heater  9  is the same as that for the second embodiment as shown in FIG.  7  and the corresponding flowchart and explanation will be omitted. 
     With the fifth embodiment according to the invention, too, it is possible to even more efficiently control the temperature of the adsorption sheet  3  by installing a heater on a surface of a mesh  32  and between active carbons  31  as shown in FIGS. 12A,  12 B,  13 A and  13 B, showing modified examples of the fourth embodiment according to the invention, which allows performance to be enhanced. 
     When the heater is heated by an electric power as in the fifth embodiment according to the invention, reduced fuel economy results if the heater is kept energized at all times. It would be preferable if a control be added, with which the heater  9  is energized for only a period of time required for purging HCs from the adsorption sheet  3  and is stopped as soon as the purging of the adsorption sheet  3  is completed. FIG. 15 shows a flowchart, in which a control is provided by means of an output signal provided by an air flow sensor  23  installed in the intake pipe  2 . An amount of the intake air required for purging HCs from the adsorption sheet  3  V 0  is determined by adsorption performance and desorption performance of the adsorption sheet  3  and a calorific value of the heater  9  (or the temperature of the adsorption sheet  3  when heated). 
     If it is determined that the engine  1  has started operating as a result of IG being turned ON (Yes) (in step  501 ), the energization control of the heater  9  is started. Since the engine  1  is operating at low revolution speeds or under low loads immediately after the start, the heater  9  is energized in step  502 . In step  503 , it is then determined whether or not the engine  1  has stopped. If it is determined that the engine  1  has stopped (Yes), the control proceeds to step  513 , in which current supply to the heater  9  is cut off and the control is terminated. If it is determined that the engine  1  has not stopped (No), the control proceeds to step  504 , in which the amount of the intake air V is obtained from the output signal supplied by the air flow sensor  23 . 
     In step  505 , a cumulative amount of the intake air V′ since the control was started is obtained. In subsequent step  506 , it is determined whether or not the cumulative amount of the intake air V′ reaches the required amount of the intake air V 0 . If it is determined that V′≧V 0  is true (Yes), it is considered that the purging of the adsorption sheet  3  is completed and the control proceeds to step  513 , in which the current supply to the heater  9  is cut off and the control is terminated. 
     If it is determined that V′≧V 0  is not true (No), it is determined that the purging of the adsorption sheet  3  is not completed and the control proceeds to step  507 . In step  507 , an engine revolution speed N or a load T at the current timing is measured by a revolution speed sensor of the engine  1 , signals indicating engine operating states, signals controlling the engine  1 , and the like. In step  508 , it is determined whether or not the engine revolution speed N or the load T at the current timing is equal to or greater than predetermined values N 0  and T 0 , respectively. If N≧N 0  (or T≧T 0 ) is not true (No), it is determined that the engine  1  is still operating at low revolution speeds or under low loads and the control returns to step  503 . If N≧N 0  (or T≧T 0 ) is true (Yes), it is determined that the engine  1  is operating at high revolution speeds or under heavy loads and the control proceeds to step  509 , in which current supply to the heater  9  is cut off. 
     In step  510 , it is determined whether or not the engine  1  has stopped. If it is determined that the engine  1  has stopped (Yes), the control proceeds to step  513 , in which current supply to the heater  9  is cut off and the control is terminated. If it is determined that the engine  1  has not stopped (No), the control proceeds to step  511 , in which the engine revolution speed N or the load T at the current timing is measured by a revolution speed sensor of the engine  1 , signals indicating engine operating states, signals controlling the engine  1 , and the like. In step  512 , it is determined whether or not the engine revolution speed N or the load T at the current timing is equal to or greater than predetermined values N 0  and T 0 , respectively. If N≧N 0  (or T≧T 0 ) is true (Yes), it is determined that the engine  1  is still operating at high revolution speeds or under heavy loads and the control returns to step  510 . If N≧N 0  (or T≧T 0 ) is not true (No), it is determined that the engine  1  is now operating at low revolution speeds or under low loads and the control returns to step  502 . This control applies also to each of the first through fifth embodiments. 
     The control routine shown in FIG. 15 is an example of a type of control that is based on only the amount of the intake air available for a period of time while the heater  9  is being energized, during which the adsorption sheet  3  is heated. However, HCs are purged also for a period of time during which the adsorption sheet  3  is not heated. 
     A control routine, which takes into account this fact, is shown in FIG.  16 . Steps  601 - 610  are exactly the same as steps  501 - 510  in FIG. 15. A difference of the control routine shown in FIG. 16 from that shown in FIG. 15 is the portion of steps  611 - 613 , particularly step  612 . The adsorption sheet  3  offers different desorption performance between when it is heated and when it is not heated. Namely, to ensure that the same amount of HCs is to be desorbed, a greater amount of the intake air is required when the adsorption sheet  3  is not heated than when it is heated. A coefficient k indicating the effect of whether or not the adsorption sheet is heated is obtained in advance and considered (step  612 ) when finding the cumulative amount of the intake air V′ when the adsorption sheet is not heated. 
     Explanations in greater detail will be omitted, since the rest of the routine steps are the same as those shown in FIG.  15 . It is also effective if this control routine is applied to each of the first through fifth embodiments according to the invention. 
     After the purging of the adsorption sheet  3  has been completed, control may be shifted to an ordinary control for the engine  1 , different from the control to desorb fuel vapor from the adsorbent  31 . 
     In each of the different embodiments according to the invention as shown in the accompanying drawings, the adsorbent  31  such as the active carbon is held in the adsorption sheet  3  housed in the air cleaner  21 . In a fuel vapor adsorption apparatus according to the invention, the adsorbent  31  may be disposed at a position, other than a position inside the air cleaner  21 , for example, downstream of the air cleaner  21  inside the intake pipe  2  and upstream of the ordinary intake throttle valve  6 . In addition, if an arrangement allows the adsorbent  31  to be directly heated by the heater  9  or coolant, the adsorbent  31  may be disposed downstream of the intake throttle valve  6 . 
     An arrangement is also possible, in which the engine revolution speed N or the load T at the current timing is measured/determined by, for example, the revolution speed sensor of the engine  1 , the opening of the intake throttle valve  6 , signals indicating other engine operating states, signals controlling the engine  1 . Based on the engine revolution speed N or the load T, the calorific value for the adsorbent sheet  3  (or the adsorbent  31 ) is controlled. 
     The ECU  7  and the actuator  52  can be regarded as examples of a controller for the invention. 
     In the illustrated embodiment, the apparatus is controlled a controller, which is implemented as a programmed general purpose computer. It will be appreciated by those skilled in the art that the controller can be implemented using a single special purpose integrated circuit (e.g., ASIC) having a main or central processor section for overall, system-level control, and separate sections dedicated to performing various different specific computations, functions and other processes under control of the central processor section. The controller can be a plurality of separate dedicated or programmable integrated or other electronic circuits or devices (e.g., hardwired electronic or logic circuits such as discrete element circuits, or programmable logic devices such as PLDs, PLAs, PALs or the like). The controller can be implemented using a suitably programmed general purpose computer, e.g., a microprocessor, microcontroller or other processor device (CPU or MPU), either alone or in conjunction with one or more peripheral (e.g., integrated circuit) data and signal processing devices. In general, any device or assembly of devices on which a finite state machine capable of implementing the procedures described herein can be used as the controller. A distributed processing architecture can be used for maximum data/signal processing capability and speed. 
     While the invention has been described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the preferred embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the preferred embodiments are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.