Patent Publication Number: US-5835816-A

Title: Remote service system for image forming apparatuses

Description:
This is a continuation of application Ser. No. 08/588,305 filed on Jan. 18, 1996, now U.S. Pat. No. 5,715,496. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a remote service system for a number of copiers, facsimile apparatuses, printers or similar image forming apparatuses used by respective users. 
     Today, a great number of image forming apparatuses for forming images on papers are used in various fields. Because paper jams or similar troubles are unavoidable with this kind of apparatus, the apparatus is devised such that in the event of, e.g., a jam, the user can remove a jamming sheet and restore the apparatus to its normal condition as far as possible. However, some kinds of jams and other troubles cannot be dealt with by the user and need a serviceman. In light of this, it is a common practice for the user and the manufacturer or distributor to make a maintenance contract, so that periodic inspection and maintenance by a serviceman and rapid repair in the event of a trouble are available. 
     Further, a number of copiers used at different locations may be connected to a single control unit or computer located at, e.g., a control center by a telephone network or similar communication line, as disclosed in, e.g., Japanese Patent Laid-Open Publication No. 3-293369 or 5-80609. When a jam or similar trouble occurs in any one of the copiers, information representative of the trouble is sent to the control unit over the communication line. Therefore, the control unit is capable of collectively controlling all the copiers at the remote station. 
     The control unit taught in the above Laid-Open Publication No. 3-293369 detects jams occurred in the copier, counts the jams while classifying them by location so as to calculate the frequency of jam, and sends, when the frequency at any location exceeds an allowable value assigned to the location, alarm data to the control unit over a public telephone network, thereby informing it of the unusual number of jams. 
     This allows the control center to see such an unusual occurrence immediately and take an adequate measure, e.g., send a serviceman. 
     The copier taught in the above Laid-Open Publication No. 5-80609 also detects and stores, location by location, the jam or similar defective transport of a paper occurred during the course of an image forming sequence. The copier determines a data transfer timing on the basis of a change in information representative of the stored transport error (frequency or the like), and then sends the information to a host computer located at a control center. The operator at the control center is capable of confirming the received information on, e.g., a display. 
     However, in the conventional copier and control unit described above, the copier stores the error information representative of jams or similar errors and determines the data transfer timing, while the control unit simply allows the operator to see the information received from the copier on a display or the like. Therefore, the operator must determine or predict an error on the basis of the received information, determine whether or not a serviceman&#39;s visit is necessary, select, if it is necessary, a service station in charge of the faulty copier, and then communicate with a serviceman by telephone or facsimile machine to report information relating to the copier and its conditions to him. 
     Moreover, when all kinds of information relating to the copier are sent to the service station, the operator at the service station must determine whether or not they are representative of a critical error to occur or of simple operating conditions, wasting time and labor as well as a communication cost. Should the information to be sent and timing are extremely limited at, e.g, the copier, as in the conventional arrangement, it would be impossible for the operator to predict an error or whether or not a serviceman&#39;s visit is necessary (remote diagnosis). 
     In addition, because service stations for copiers or similar image forming apparatuses each covers a particular area, it is desirable from the rapid service standpoint that a serviceman be sent from a service station closest to the place where the faulty copier is located. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a remote service system for image forming apparatuses distributed over a broad area, including a number of service stations, and capable of automatically effecting the collection of service information from each apparatus, the prediction of an error, and the request for a serviceman, thereby allowing an adequate measure to be taken efficiently and rapidly before the occurrence of a critical error. 
     It is another object of the present invention to provide a remote service system for image forming apparatuses and having a single control unit capable of executing highly accurate remote diagnosis, e.g., the prediction of an error and whether or not a serviceman&#39;s visit is needed and automatically sending, if it is needed, necessary information to a service station in charge of a faulty apparatus. 
     In accorance with the present invention, in a service system, a plurality of image forming apparatuses and a control unit for remote-controlling them are connected by a communication line. A plurality of terminal units are located at respective service stations and also connected to the control unit. The image forming apparatuses each sends, when an event indicative of or predictive of an error occurs therein, information representative of the event to the control unit. The control unit received the information analyzes it and then selectively sends information relating to maintenance or repair to the image forming apparatuses to the terminal units. The control unit has a store for sequentially storing the information received from the image forming apparatuses, an analyzer for analyzing the information stored in the store, a predictor for predicting, based on the result of analysis of the analyzer, the occurrence of an error and whether or not a serviceman s visit is necessary, and a transmitter for transmitting the result of prediction of the predictor to the service station in charge of the image forming apparatus in which an error has occurred or which needs a serviceman&#39;s visit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which: 
     FIG. 1 is a block diagram schematically showing a remote service system for image forming apparatuses and embodying the present invention; 
     FIG. 2 shows a number of paper sensors each being located at a particular section of an image forming apparatus, implemented as a copier by way of example, or a particular position on a paper transport path; 
     FIG. 3 is a block diagram schematically showing a specific construction of the copier; 
     FIG. 4 is a block diagram schematically showing a specific construction of a control unit shown in FIG. 1; 
     FIG. 5 is a block diagram schematically showing a specific construction of a terminal unit also shown in FIG. 1; 
     FIG. 6 is a flowchart demonstrating a routine to be executed by the copier of FIG. 1 and relating to jam alarm processing; 
     FIG. 7 is a flowchart demonstrating a main routine to be executed by the control unit or host computer of FIG. 4 and relating to the analysis of jam alarm information and the prediction of the need for a serviceman&#39;s visit; 
     FIG. 8 is a flowchart representative of a routine included in FIG. 7 for the calculation, preparation and registration of transition point history data; 
     FIG. 9 is a flowchart representative of a routine also included in FIG. 7 for making a decision on a valid information evaluation term; 
     FIG. 10 is a flowchart representative of a routine also included in FIG. 7 for making a decision on a same trend jam alarm; 
     FIG. 11 is a flowchart representative of a routine further included in FIG. 7 for making a decision on a jam ratio over alarm; 
     FIG. 12 is a flowchart representative of a routine additionally included in FIG. 7 for making a decision on a jam occupancy ratio over alarm; 
     FIG. 13 a graph showing location-by-location changes in the cumulative number of jams between consecutive jam alarm information, and plotted at times when the history data are registered; and 
     FIG. 14 demonstrates the storage of jam alarm information and representative of an alternative embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 of the drawings, a remote service system for image forming apparatuses and embodying the present invention is shown. As shown, the system includes a number of image forming apparatuses implemented as copiers 1 and located at, e.g., users&#39; offices. The copiers 1 are connected to a single control unit or host computer 4 via a data communication unit 2 and a communication line 3. Terminal units 6 are each located at a particular service center and connected to the control unit 4 by a communication line 5. The communication lines 3 and 5 may be implemented by a public line network by way of example. 
     Each copier 1 has means for detecting a paper jam or similar error occurred or an event predictive of such an error to occur, and means for sending information representative of the error or predictive event to the control unit 4 together with necessary additional information via the communication unit 2 and line 3. The control unit 4 has means for receiving the information from the copiers I and storing them on a copier basis, means for analyzing the information in order to predict the occurrence of an error and whether or not a serviceman&#39;s visit is needed, and means for automatically sending, if a serviceman&#39;s visit is needed, necessary information to one of the terminal units 6 in charge of the copier 1 in trouble. Each terminal unit 6 is implemented by a minicomputer or a personal computer and has means for storing the data received from the control unit 4, and display means for informing a serviceman of, e.g., the place to visit and the conditions of the faulty copier 1. 
     FIG. 2 shows the sections of each copier 1 joining in image formation, and various paper sensors arranged along a paper transport path. As shown, the copier 1 has a photoconductive drum 10 at the center thereof. Arranged around the drum 10 are a main charger 11, a developing unit 12, a transfer charger 13, and a cleaning unit 14. While the drum 10 is rotated in the direction indicated by an arrow, the main charger 11 uniformly charges the surface of the drum 10. The charged surface of the drum 10 is exposed imagewise by a scanner and exposing device, not shown. As a result, a latent image representative of a document image is electrostatically formed on the drum 10. The developing unit 12 develops the latent image with a toner to thereby form a corresponding toner image. 
     Papers P stacked on a paper tray 15 are fed toward a registration roller pair 17 by a pick-up roller 16 one by one. The roller pair 17 drives, at a preselected timing, the paper toward an image transfer position where the transfer charger 13 is located. The transfer charger 13 is operated to transfer the toner image from the drum 10 to the paper P arrived at the image transfer position. The paper P with the toner image is conveyed to a fixing unit 18 by a conveyor belt or conveying section 18. The fixing unit 18 fixes the toner image on the paper P by heating it. Subsequently, the paper or copy P is driven out of the copier 1. After the image transfer, the surface of the drum 10 is cleaned by the cleaning unit 14 and prepared for the next charging thereby. 
     The paper sensors, e.g., reflection type or transmission type photosensors are sequentially arranged on the above path along which the paper P is transported in the copier 1. Specifically, there are shown in FIG. 2 a feed sensor A located at the outlet side of the pick-up roller 16, a registration sensor F located at the outlet side of the registration roller pair 17, a conveyance sensor G located at the conveying section 18, a fixation sensor H located at the inlet of the fixing unit 19, and a discharge sensor I located at the outlet of the unit 19. By monitoring the output signals of the sensors A and F-I and paper transport times, it is possible to detect a transport error, i.e., paper jam and the location where it occurred. In the event of a jam, the operation of the copier 1 is interrupted while the jam is displayed on an operation and display panel, not shown. This kind of procedure is conventional. 
     FIGS. 3, 4 and 5 respectively show the arrangements of the copier 1, control unit 4 and terminal unit 6 which are relevant to the present invention. The operations of the copier 1, control unit 4 and terminal unit 6 will be described with reference also made to FIG. 6 and successive figures. 
     As shown in FIG. 3, the copier 1 has an operation 20 provided on the operation and display panel and including a start key, numeral keys and other conventional keys (switches), and indicators for displaying various conditions. A copy sequence control 21 controls the copy sequence of the copier 1 with a microcomputer. Assume that the start key included in the operation 20 is pressed. Then, the control 21 sequentially controls the various sections shown in FIG. 2, and the scanner, exposing device, motors, clutches, high-tension power sources and so forth which are not shown in FIG. 2, thereby controlling a procedure for reproducing a document image on a paper. At the same time, the control 21 collectively controls the entire copier 1. Sensors 22 include the paper sensors A and F-I, FIG. 2, as well as sensors responsive to temperature (and humidity) inside the copier 1, fixing temperature, drum surface temperature, presence/absence of supplies, etc. A status information store 23 is a memory for storing status information relating to the copier 1 and represented by the output signals of the control 21 and sensors 22. The status information is additional information to be sent together with an alarm signal which will be described. For example, the count of a total counter (TC) for counting the cumulative number of copies, conveying time of the pick-up roller, fixing temperature and image density are included in the status information. 
     The sequence control 21 delivers a count signal to a copy counter 24 every time a copy is produced. The copy counter 24 counts copies on the basis of the count signals received from the control 21. An alarm level store 25 stores an alarm level input from the operation 20. The alarm level is representative of the number of copies produced without a jam and necessary for a jam alarm count to be decremented. The store 25 is implemented by a nonvolatile memory in order to prevent the alarm level from being deleted in the event of power down. A comparator 26 compares a count received from the counter 24 and an alarm level received from the store 25. When the number of copies reaches the alarm level, the comparator 26 feeds the result of comparison to a jam alarm counter 27. 
     When the jam alarm counter 27 receives a jam signal from a jam detector 28, it increments the jam alarm count. If the jam alarm count is not &#34;0&#34; when the counter 27 receives the result of comparison from the comparator 26, the counter 27 decrements it. When the jam alarm count reaches a predetermined value, e.g., &#34;10&#34;, the counter 27 delivers jam alarm information to a transmitter 29 and, at the same time, sends a reset signal to the copy counter 24 for thereby resetting it. The counter 27 should preferably count not only such jam alarms but also jams occurred at the individual location in the copier 1. For example, the counter 27 may count jams sensed by the sensors A and F-I, FIG. 2, as A jams, F jams, G jams, H jams and I jams, respectively. Then, when the above jam alarm count reaches &#34;10&#34;, the counter 27 will output, e.g, A jams &#34;5&#34;, F jams &#34;0&#34;, G jams &#34;2&#34;, H jams &#34;1&#34; and I jams &#34;2&#34; as jam alarm information. 
     The transmitter 29 sends the jam alarm information received from the counter 27 to the control unit 4 via the data communication unit 2 and line 3, FIG. 1, together with the previously mentioned status information stored in the store 23 and an ID (identification) assigned to the copier 1. 
     The jam detector 28 monitors the output signals of the sensors A and F-I, FIG. 2, which are representative of paper transport times during the course of a copying operation as executed by the copy sequence control 21. For example, when the sensor located at the downstream side does not sense a paper in a preselected period of time after the sensor located at the upstream side has sensed it, or when the same sensor continuously senses a paper for more than a preselected period of time, the jam detector 28 determines that a jam has occurred, and then sends a jam signal particular to the location in trouble to the jam alarm counter 27. The jam signal is also used to interrupt the copying operation under way, and to display the jam and the location where it occurred on the operation 20. Usually, the operator of the copier 1 watching the display can remove the jamming sheet and thereby restore the copier to its normal condition. 
     A reference will be made to FIG. 6 for describing jam alarm processing to be executed by the various sections of the copier 1. First, whether or not a copying operation is under way is determined (step S10). Only if a copying operation is under way, the routine to be described is effected; if otherwise, the program simply returns to a main routine, not shown. If the answer of the above decision is positive (Y, step S10), whether or not the time for counting copies has been reached is determined (step S11). If the answer of the step S11 is Y, the number of copies is incremented by 1 (one) (step S12). If the answer of the step S11 is negative (N), the operation is transferred to a step S17. The step S12 is followed by a step S13 for comparing the copy count with the alarm level. If the copy count is greater than or equal to the alarm level, e.g., 2,500 copies (Y, step S13), a step S14 is executed; if otherwise, the step S17 is executed. 
     In the step S14, whether or not the jam alarm count is &#34;0&#34; is determined. If the answer of the step S14 is Y, a step S16 is executed; if otherwise, the jam alarm count is decremented by 1, and then the step S16 is executed. In the step S16, the copy count is reset. Subsequently, whether or not a jam has occurred is determined (step S17). If the answer of the step S17 is Y, the jam alarm is incremented by 1 (step S18), and then the copy count is reset (step S19). This is followed by a step S20. If the answer of the step S17 is N, the step S18 is directly followed by the step S20. In the case of a jam, the location where it occurred is determined, and a jam counter assigned thereto is also incremented by 1. 
     In the step S20, whether or not the jam alarm count has reached the preselected value (&#34;10&#34; in the embodiment) is determined. If the answer of the step S20 is Y, the jam alarm information is sent to the control unit 4 together with the additional information and copier ID (step S21). Then, the jam alarm count is reset (step S22). If the answer of the step S20 is N, the routine simply ends. 
     FIG. 4 shows a specific construction of the control unit or host computer 4. As shown, the control unit 4 has a receiver 40 for receiving the jam alarm information and additional information from each copier 1, a store 41 for sequentially storing the received information on a copier ID basis, an analyzer for analyzing the jam alarm information, a predictor 43 for predicting whether or not a serviceman&#39;s visit is necessary, and a transmitter 44. Every time the receiver 40 receives jam alarm information, the analyzer 42 analyzes the jam alarm information written to the store 41 and including the information particular to the copier 1, and performs remote diagnosis, e.g., error prediction. The predictor 42 predicts whether or not a serviceman&#39;s visit is necessary on the basis of the output of the analyzer 42. If the answer of this decision is positive, the predictor 43 sends to the transmitter 44 serviceman request information and, among the information stored in the store 41, information necessary for a service. The transmitter 44 sends such information to one of the service stations 6, FIG. 1, in charge of the faulty copier 1. 
     FIG. 5 shows a specific construction of the service station or terminal unit 6. As shown, the terminal unit 6 has a receiver 60 for receiving the serviceman request information and information necessary for a service, a store 61 for storing the received information, a reporter 62 for reporting the serviceman request received by the receiver 60 to the operator, and a display 63 for displaying the received information (jam alarm information). 
     How the control unit or host computer 4 analyzes the jam alarm information and predicts whether or not a serviceman&#39;s visit is necessary will be described with reference to FIG. 7 and successive figures. FIG. 7 shows a main routine to be executed by the computer 4. As shown, when the receiver 40 receives the jam alarm information (Y, step S30), the copier ID included in the information is identified, and then the information is cumulatively written to the store 41 (step S31). Subsequently, the analyzer 42 compares the newly received jam alarm information with the jam alarm information stored in the store 41 and particular to the copier 1, thereby executing the calculation, preparation and registration of transition point history data (step S32). This will be described in detail later. After the step S32, the predictor 43 makes a decision on a valid information evaluation term (step S33) to see if this time lies in a valid information evaluation term (step S34). If the answer of the step S34 is Y, the predictor 43 makes a decision on a same trend jam alarm (first prediction relating to the need for a serviceman&#39;s visit) (step S35). If the jam alarm is of the same trend (needing a serviceman&#39;s visit) (Y, step S36), the transmitter 44 sends the serviceman request and necessary information to the terminal unit 6 in charge of the copier 1 (step S41). 
     If the answer of the step S34 is N or if the answer of the step S36 is N, the predictor 43 makes a decision on a jam ratio over alarm (second prediction relating to the need for a serviceman&#39;s visit) (steps S37 and S38). If the answer of the step S38 is Y, meaning that a serviceman&#39;s visit is necessary, the transmitter 44 sends an alarm to the terminal unit 6 in charge of the copier 1. If the answer of the step S38 is N, the predictor 43 makes a decision on a jam occupancy over alarm (third prediction relating to the need for a serviceman&#39;s visit) (steps S39 and S40). If the answer of the step S40 is Y, meaning that a serviceman&#39;s visit is necessary, the transmitter 44 sends an alarm to the above terminal unit 6 (step S41). If the answer of the step S42 is N, the predictor 43 writes the transition point history data in the store 41 (step S42). Then, the main routine shown in FIG. 7 ends. The decisions mentioned above will also be described in detail later. 
     First, the calculation, preparation and registration of the transition point history data derived from the jam alarm information and executed by the analyzer 42 will be described with reference to FIG. 8. As shown, the analyzer 42 determines whether or not the jam alarm information is the first jam alarm information (step S50). If the answer of the step S50 is Y, the analyzer 42 prepares a transition point history table (step S58). If the answer of the step S50 is N, the analyzer 42 subtracts (cumulative numbers of jams of this time by locations) from (cumulative numbers of jams of last time by locations), i.e., calculates an increment from the last jam alarm information of the individual location (step S51). After repeating such a calculation with every location (Y, step S51), the analyzer 42 subtracts (date of jam alarm of this time) from (date of jam alarm of last time) in order to produce the number of days of operation (step S53). Then, the analyzer 42 writes the count of the total counter (TC) in the transition point history data (step S54). 
     Further, the analyzer 42 subtracts (TC of jam alarms of this time) from (TC of jam alarms of last time) in order to calculate the number of copies produced for a given term, i.e., term copy number (step S55). Then, the analyzer 42 divides the above term copy count by the sum (nearly equal to &#34;10&#34;) of the transition values Xi of this time, thereby producing JAMCBF (jam ratio: the number of copies produced between consecutive jams) (step S56). Subsequently, the analyzer 42 divides the sum of the transition values Xi by the number of days of operation so as to produce the number of jams occurred a day (jams per day) (step S57), prepares a transition point history table (step S58), and registers the history data (step S59). 
     Table 1 shown below lists specific jam alarm information written to the store 41 of the control unit 4. As shown, the jam alarm information are the cumulative values of the total counter (TC), A jams, F jams, G jams, H jams and I jams stored together with the dates of receipt of the jam alarm information. The dates are implemented by a timepiece function included in the control unit 4. Table 2 also shown below lists transition point history data derived from the information of Table 1 and generated by the analyzer 42. 
     
                       TABLE 1                                                     
______________________________________                                    
Date   TC     A Jam    F Jam G Jam  H Jam I Jam                           
______________________________________                                    
Date 1 TC1    1 time   2 times                                            
                             3 times                                      
                                    1 times                               
                                          3 times                         
Date 2 TC2    2 times  4 times                                            
                             6 times                                      
                                    3 times                               
                                          7 times                         
Date 3 TC3    4 times  5 times                                            
                             7 times                                      
                                    3 times                               
                                          11 times                        
.      .      .        .     .      .     .                               
.      .      .        .     .      .     .                               
.      .      .        .     .      .     .                               
Date N TCN    times    times times  times times                           
______________________________________                                    
 
    
     
                                           TABLE 2                                 
__________________________________________________________________________
Number                                                                    
     Term                                                                 
of Days of                                                                
     Copy                                                                 
Operation                                                                 
     Count                                                                
         AXi                                                              
            FXi GXi                                                       
                   HXi                                                    
                      IXi ΣXi                                       
                             JAMCBF                                       
                                  Jams/Day                                
__________________________________________________________________________
16   3800                                                                 
         1  2   3  2  4   11 345  0.69                                    
20   4600                                                                 
         2  1   1  0  5   10 460  0.5                                     
.    .   .  .   .  .  .   .  .    .                                       
.    .   .  .   .  .  .   .  .    .                                       
.    .   .  .   .  .  .   .  .    .                                       
 8   2150                                                                 
         6  2   1  0  1   10 215  1.25                                    
__________________________________________________________________________
 
    
     In Table 2, AXi, FXi, GXi, HXi and IXi are respectively representative of transition values between the A jams, F jams, kG jams, H jams and I jams of this time and those of the last time, while ΣXi is representative of the sum of such transistion values. The sum ΣXi often coincides with the preselected value (&#34;10&#34; in the specific case), but it exceeds the preselected value when the jam alarm count is subtracted. 
     The various decisions mentioned with reference to FIG. 7 and executed by the predictor 43 will be described in detail hereinafter. 
     FIG. 9 shows the decision on the valid information evaluation term. As shown, the predictor 43 reads the transistion history data, e.g., the data of Table 1 out of the analyzer 42 (step S60). If the last data is the first jam alarm information (Y, step S61), the predictor 43 ends the routine. If the answer of the step S61 is N, the predictor 43 determines whether or not the number of days of operation is less than or equal to &#34;30&#34; (step S62). If the answer of the step S62 is N, the predictor 43 ends the routine; if otherwise, it determines that this time lies in a valid information evaluation term (step S63). Of course, any desired number of days other than thirty may be selected in matching relation to the user&#39;s characteristic, e.g., the user strict on errors or the user needing priority administration. 
     FIG. 10 shows the decision on the same trend jam alarm or first prediction relating to the need for a serviceman&#39;s visit. First, the predictor 43 reads the transition point history data out of the analyzer 42 (step S70), and determines whether or not the last data is the first jam alarm information (step S71). If the answer of the step S71 is Y, the predictor 43 ends the routine; if otherwise, it confirms the location-by-location jam alarm occupancy ratios of the last time, i.e., the ratios of the numbers of jams AXi-IXi of Table 2 to the sum ΣXi (step S72). If the jam alarm occupancy ratio of any location is greater than or equal to 60% (Y, step S77), the predictor 43 memorizes the location (step S73). After executing the above procedure with the A jam location to the I jam location (steps S74 and S75), the predictor 43 confirms the location-by-location jam alarm occupancy ratios of this time (step S76), and if any of them is greater than or equal to 60% (step S77), memorizes the location (step S78). 
     On completing the above procedure with the A jam location to the I jam location (step S79), the predictor 43 compares information representative of the location where the jam alarm occupancy ratio of the last time is greater than or equal to 60% and information representative of the location where the occupancy ratio of this time is greater than or equal to 60% (step S80), thereby determining whether or not a jam has occurred at the same location (step S81). If the answer of the step S81 is N, the predictor 43 ends the routine. If the answer of the step S81 is Y, the predictor 43 determines that jam alarm information of the same trend has occurred (needing a serviceman&#39;s visit) (step S82), and then ends the routine. Specifically, when jam alarm information representative of a jam occupancy ratio of greater than 60% and particular to a certain location is received twice within the valid information evaluation term (e.g. thirty days), the corresponding portion of the last data (transition point history data) is marked and then sent. Of course, any desired ratio other than 60% may be selected in matching relation to the user&#39;s characteristic, e.g., the user needing priority administration or the user suffered from many jams last month 
     FIG. 11 shows the decision on the jam ratio over alarm or second prediction relating to the need for a serviceman&#39;s visit. First, the predictor 43 reads the transition point history data out of the analyzer 42 (step S90), and then determines whether or not the last data is the first jam alarm information (step S91). If the answer of the step S91 is Y, the predictor 43 simply ends the routine. If the answer of the step S91 is N, the predictor 43 confirms JAMCBF (jam ratio: term copy number/ΣXi) (step S92). If JAMCBF is smaller than or equal to a preselected value (&#34;150&#34; in this case) (Y, step S93), the predictor 43 determines that jam ratio over alarm information has occurred (needing a serviceman&#39;s visit) (step S94), and then ends the routine. Specifically, when the jam ratio JAMCBF included in the data of Table 2 falls below the preselected value (150), the transition point history data of that instant is sent as jam ratio over alarm information. 
     Again, any desired value other than 150 may be selected in matching relation to the user&#39;s characteristic, e.g., the user needing priority administration or the user suffered from many jams last month. In addition, the reciprocal of JAMCBF may be used as the jam ratio. 
     FIG. 12 shows the decision on the jam occupancy ratio over alarm or third prediction as to the need for a serviceman&#39;s visit. First, the predictor 43 reads the transition point history data out of the analyzer 42 (step S100), and determines whether or not the last data is the first jam alarm information (step S101). If the answer of the step S101 is Y, the predictor 43 ends the routine. If the answer of the step S101 is N, the predictor 43 confirms the jam alarm occupancy ratio of this time location by location (step S102). If the occupancy ratio of any location is greater than or equal to 80% (Y, step S 103), the predictor 43 determines that jam occupancy ratio over alarm information (needing a serviceman&#39;s visit) has occurred (step S104), and then ends the routine. Specifically, even if a serviceman&#39;s visit is not necessary, as determined in any one of the above steps, the predictor 43 determines, when the jam occupancy ratio of any location is greater than or equal to 80%, that a serviceman&#39;s visit is necessary; the transition point history data of that instant is sent. Of course, the any desired ratio other than 80% may be selected in matching relation to the user&#39;s characteristic, e.g., the user needing priority administration or the user suffered from many jams last time. 
     FIG. 13 shows, taking the A jams, F jams and I jams as an example, the transition values (Xi) of the cumulative numbers of jams between consecutive jam alarm information, and plotted at the times when the data listed in Table 2 are registered. The curves of FIG. 13 each indicates the trend between the consecutive times. By using the trend, it is possible to predict the need for a serviceman&#39;s visit (an error occurs) or the location where an error occurs, when the trend agrees with a particular pattern. For example, as to the A jams, the trend toward higher frequency is still continuing, and the same trend has occurred a plurality of consecutive times. Hence, it is possible to determine that a cause of jam exists in the sheet feed section, and that a serviceman&#39;s visit is needed. As to the I jams, although the frequency has increased for a while, it is now decreased; it is possible to determine that a serviceman&#39;s visit is not necessary although a cause of jam exists in the paper discharge section. For the prediction of an error and the prediction of the need for a serviceman&#39;s visit, any desired criterion other than the above pattern may be used. For example, when the number of jams occurred a day shown in Table 2 exceeds 1.0, it may be predicted that a serviceman&#39;s visit is necessary. 
     FIG. 14 shows the storage of the jam alarm information and representative of an alternative embodiment of the present invention. As shown, in this embodiment, the cumulative numbers of jams classified by location are not written to the store 41, FIG. 4, of the control unit 4, but only the numbers of jams represented by the jam alarm information of the last time are stored therein. The analyzer 42 compares the location-by-location numbers of jams of this time with the above information stored in the store 41, and stores only binary data representative of trend values, i.e., whether or not the number of this time is greater than the number of the last time (ONE if the former is greater than the latter or ZERO if otherwise). When ONE continuously appears more than a predetermined time, it may be determined that a serviceman&#39;s visit is necessary. This successfully saves the memory capacity required of the control unit 4 to a noticeable degree. 
     The retroactive range of the valid information evaluation term to be use by the analyzer 42 and predictor 43 of the control unit or host computer 4, and the preselected values for the various decisions may be input on a numerical input section included in the host computer 4, as desired. Specifically, the operator of the host computer 4 may select a range setting picture or a reference value setting picture on the computer 4, and then manipulate numeral keys arranged on an operating section. 
     While the embodiments have concentrated on a paper jam, the present invention is practicable with any other event indicative of or predictive of an error, e.g., one relating to a fixing temperature or a charge voltage. In addition, the present invention is applicable not only to copiers but also to facsimile apparatuses, printers and other image forming apparatuses. 
     In summary, it will be seen that the present invention provides a remote service system for image forming apparatuses and having various unprecedented advantages, as enumerated below. 
     (1) The system has a single control unit capable of automatically collecting service information from the apparatuses distributed over a broad range including numerous service stations, automatically effecting accurate remote diagnosis including the prediction of an error and the prediction as to whether or not a serviceman&#39;s visit is necessary, and automatically sending, e.g., a serviceman request to a necessary service station or terminal unit. Hence, the system allows a rapid and adequate measure to be taken before a critical error occurs. 
     (2) The range of information to be analyzed by the control unit can be adequately selected in matching relation to the user&#39;s characteristic and other conditions. This promotes rapid diagnosis and prediction. 
     (3) The control unit may not cumulatively store phenomena indicative of or predictive of errors received from each apparatus, but it may sequentially store only the trend of occurrence of errors. Then, a memory capacity required of the control unit can be noticeably reduced. 
     Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.