Patent Publication Number: US-6659077-B2

Title: Control system and control method of engine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control system, and more particularly, a control system and a control method of a water-cooled multi-cylinder engine, which is utilized at a time of an overheat of the engine. 
     2. Description of the Related Art 
     In a compact four-stroke-cycle multi-cylinder engine, which is mounted, for example, to an outboard motor or like, there is provided a structure adapted to employ a water-cooled type engine cooling method. In a concrete example of a cooling water passage structure, for example, a cooling water such as a sea water, a lake water or the like sucked from a water intake port is pressurized by a water pump so as to be introduced to the engine. 
     In this case, when the water intake port for the cooling water is clogged by an algae or the like or a water pump gets out of order, an overheat of the engine will be caused due to shortage of the cooling water. In order to obviate such defect, there is provided a structure having a control system for executing a misfire of an ignition plug, stopping of a fuel injection or fuel supply, or like so as to reduce an engine revolution number, thereby restricting an ascent of an engine temperature. 
     However, in the engine provided with such control system as mentioned above, even if the engine remains the overheat state, a normal ignition and a normal injection are executed in the case where the engine revolution number becomes lower than a limited revolution number, and, hence, a normal operation would be executed. 
     There is no problem in the case of, for example, clogging of the water intake port or the like, which can relatively easily solved. However, in the case of a problem which is not easily solved on the scene, for example, a roughness on the sea condition, a trouble of the water pump or the like, it is obliged for the engine to be driven even in the overheat state, and in such case, the temperature of the engine will have to be further increased. Accordingly, there is a fear that an excessive damage is applied to equipment such as electrical equipment arranged in an engine main body or at a periphery thereof. 
     SUMMARY OF THE INVENTION 
     The present invention is made by taking the above matters encountered in the prior art mentioned above into consideration, and an object of the present invention is to provide a control system and a control method of an engine capable of rendering the engine usable while minimally restricting an engine damage due to an overheat. 
     This and other objects can be achieved according to the present invention by providing, in a general aspect, a control system of an engine of a water-cooled multi-cylinder structure, in which an engine revolution number is reduced to a level less than a restriction revolution number on the basis of at least one condition of revolution number restriction controls including a misfire and a fuel stop for all cylinders of the engine, at a time of an occurrence of an overheat of the engine, so as to restrict an increasing of a temperature of the engine, wherein in a case when the engine revolution number is less than the restriction revolution number after the overheat occurs, or the engine revolution number is lowered to be less than the restriction revolution number on the basis of the revolution number restriction control after the overheat occurs, a specific cylinder is controlled to be stopped by means of at least one of the misfire and the fuel stop. 
     In a preferred embodiment, the specific cylinder controlled to be stopped by at least one means of the misfire and the fuel stop corresponds to first and fourth cylinders or second and third cylinders in a case of a four-stroke-cycle 4-cylinder engine, corresponds to first and second cylinders or third and fourth cylinders in a case of a two-stroke-cycle 4-cylinder engine, and corresponds to any one of cylinders in a case of a 3-cylinder engine. 
     When the specific cylinder is controlled to be stopped on the basis of the occurrence of the overheat, an idle target revolution number of the engine is set to a revolution number higher than a target revolution number at a time of normal operation period. 
     When a reason of the overheat is cancelled during the stop control of the specific cylinder, the stop control of the specific cylinder is set to be cancelled only at a time when a shift apparatus takes a neutral. 
     The engine is an engine for an outboard motor in which a crankshaft is vertically arranged. 
     In a specified aspect, there is provided a control system of an engine of a water-cooled multi-cylinder structure for controlling an overheat (i.e., revolution number) of the engine, comprising: 
     an element for detecting an occurrence of an overheat of an engine; 
     an element for monitoring and detecting an engine revolution number; 
     an element for discriminating whether the detected engine revolution number exceeds or not a restriction revolution number after occurrence of the overheat; and 
     an element for performing an operation stop control to a specific cylinder by means of at least one condition of revolution number restriction controls including misfire and fuel stop to thereby reduce the engine revolution number. 
     In anther aspect, there is provided a method of controlling an engine of a water-cooled multi-cylinder structure for controlling an overheat (i.e., revolution number) of the engine, comprising the steps of: 
     detecting an occurrence of an overheat of an engine; 
     monitoring and detecting an engine revolution number; 
     discriminating whether the detected engine revolution number exceeds or not a restriction revolution number after occurrence of the overheat; and 
     performing an operation stop control to a specific cylinder by means of at least one condition of revolution number restriction controls including misfire and fuel stop to thereby reduce the engine revolution number. 
     According to the present invention of the aspects mentioned above, in the water-cooled multi-cylinder engine provided with the control system reducing the engine revolution number to the level less than the restriction revolution number, the structure is considered so that when the engine revolution number is less than the restriction revolution number after the occurrence of the overheat, or the revolution number is lowered to be less than the restriction revolution number on the basis of the revolution number restricting control, the specific cylinder of the engine is controlled to be stopped by at least one means of the misfire and the fuel stop. Therefore, it is possible to prevent the engine temperature from being increased even when the engine is continuously used at a time of occurrence of the overheat. 
     Furthermore, since the multi-cylinder engines can be controlled in accordance with the numbers of the cylinders, it is possible to obtain a stable engine revolution even when the engine is continuously used. 
     Furthermore, according to the preferred embodiment, it is possible to obtain a stable engine revolution even in a low revolution number range of the engine. 
     Furthermore, when the reason of the overheat is cancelled during the stop control of the specific cylinder of the engine, the stop control of the specific cylinder can be set to be cancelled only at a time when the shift apparatus takes its neutral position. It is therefore possible to prevent the engine revolution number from being rapidly increased after canceling the stop control. 
     The nature and further characteristic features will be made more clear from the following descriptions made with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a right side elevational view of an outboard motor provided with a control system of an engine according to the present invention; 
     FIG. 2 is a right side elevational view showing an engine portion, in an enlarged scale, of the outboard motor shown in FIG. 1; 
     FIG. 3 is a system chart of an engine unit for the outboard motor shown in FIG. 1; 
     FIG. 4 is a block diagram of the engine unit shown in FIG. 3; 
     FIG. 5 is a flow chart showing a flow of a control executed by an overheat control system; and 
     FIG. 6 is a graph showing a temperature characteristic on the basis of an overheat control. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the present invention will be described hereunder with reference to the accompanying drawings. 
     First, with reference to FIG. 1, showing the right side elevational view of an outboard motor to which the present invention is applied, the outboard motor  1  is attached to a transom  4   a  of a hull  4  through a bracket  3 . The bracket  3  is mounted to an engine holder  2  of the outboard motor  1 . 
     The engine holder  2  is formed therein with an exhaust passage and a drain passage, which will be mentioned below, but not shown, and an engine (or engine unit)  5  is disposed above the engine holder  2 . Further, a crankshaft  6  is provided within the engine  5  in a vertical attitude so as to extend vertically as viewed. Furthermore, a drive shaft housing  8  is placed below the engine holder  2  through an oil pan  7  including an exhaust passage and a drain passage, which will be mentioned below, but not shown. An outer periphery of the engine  5  is covered by an engine cover  9 . 
     A drive shaft  10  connected to a lower end of the crankshaft  6  is arranged so as to extend downward in the oil pan  7  and the drive shaft housing  8  and to drive a propeller  14  via a bevel gear  12  and a propeller shaft  13  arranged within a gear case  11  provided below the drive shaft housing  8 . 
     Further, in the gear case  11 , there is located a shift or shifting apparatus  15  for shifting a revolution direction of the propeller shaft  13  and the propeller  14  to a forward, reverse or neutral direction through a remote control. A shift rod  16  extends upward from the shift apparatus  15  and is connected to a link mechanism  17  provided in the engine cover  9 . 
     Furthermore, a water intake port  18  is formed on a side surface of the gear case  11 , and a cooling water such as a sea water, a lake water or the like is taken therein from the water intake port  18  and then fed under pressure towards the engine  5  via a cooling water pipe  20  by a water pump  19  which is driven by the drive shaft  10 . Further, the cooling water fed towards the engine  5  is discharged out of the outboard motor together with an exhaust gas after cooling the respective portions in the engine unit  5 . 
     Next, with reference to FIGS. 1 to  3 , the engine  5  is, for example, a water-cooled four-stroke-cycle 4-cylinder engine, and in the engine  5 , a cylinder head  21 , a cylinder block  22 , a crank case  23  and the like are arranged in a lateral direction in the illustrated example. 
     A cylinder  24  is formed within the cylinder block  22  of the engine  5 . Further, a combustion chamber  25  aligned with the cylinder  24  is formed in the cylinder head  21 , and an ignition plug  26  is connected from the outside thereof. A piston  27  is slidably inserted in the cylinder  24 , and although a detailed illustration is omitted, the piston  27  and the crankshaft  6  are connected through a connection rod  28 . Further, in the illustrated structure, a reciprocating stroke of the piston  27  is converted into a rotational (or rotating) motion of the crankshaft  6 . Furthermore, although a detailed illustration is omitted, a flywheel magnet  29  is mounted to an upper end of the crankshaft  6  so as to be integrally rotated therewith. 
     An intake port  30  and an exhaust port  31  are formed within the cylinder head  21  so as to be connected to the combustion chamber  25 . Further, a fuel injector  32  for injecting a fuel in the intake port  30  is mounted to the cylinder head  21  from the outside thereof. A valve driving mechanism such as valve train  35  including an intake valve  33  and an exhaust valve  34  for opening and closing both the ports  30  and  31  is arranged in the cylinder head  21  and covered by a cylinder head cover  36 . 
     An electronic equipment  37 , an intake apparatus  38  and an exhaust apparatus  39  are arranged around the engine  5 . The intake apparatus  38  mainly comprises a silencer  40 , a throttle body  41 , a surge tank  42  and an intake manifold  43  provided with a plurality of intake pipes extending from the surge tank  42  to the respective cylinders, and they are collected and arranged in one side of the cylinder block  22 , though the detailed explanations thereof are omitted herein. 
     On the other hand, the exhaust apparatus  39  is arranged on a side opposing to the intake apparatus  38 , and the electronic equipment  37  is also collected and arranged in the same side as that of the exhaust apparatus  39 . The exhaust apparatus  39  has an exhaust manifold  44 , which is supported by a side surface of the cylinder head  21  and a side surface of the engine holder  2 . 
     A water jacket  45  is formed at the periphery of the cylinder  24  in the cylinder block  22  and at the periphery of the combustion chamber  25  of the cylinder head  21 . Further, an exhaust passage  46  is formed in the exhaust manifold so as to connect the exhaust port  31  of the cylinder block  22  to an exhaust passage, not shown, formed in the engine holder  2  and the oil pan  7 . A water jacket  47  is also formed in the periphery of the exhaust passage  46 . 
     A cooling water outlet, not shown, of the water jacket  45  is formed in the cylinder block  22  and arranged above the cylinder block  22 . A drain hose  48  is connected to the cooling water outlet so as to extend downward, and the drain hose  48  has a downstream end connected to a cooling water drain passage, not shown, formed in the engine holder  2  and the oil pan  7  to thereby discharge the cooling water into the drive shaft housing  8 . 
     An electronic equipment holder  49  is arranged to a side surface of the engine  5  and in front of the exhaust manifold  44 , and a control system or apparatus  50  for controlling the engine  5  is arranged therein. Further, a rectifier/regulator  51  is arranged between the exhaust manifold  44  and the electronic equipment holder  49 . 
     Further, a cylinder temperature sensor  52  for detecting a cylinder temperature is provided, for example, on a side surface of the cylinder block  22  above the rectifier/regulator  51 , and a manifold temperature sensor  53  for detecting a temperature of the exhaust manifold  44  is also provided on a side surface of the exhaust manifold  44 . 
     Furthermore, in the arrangement of the 4-cylinders (first to fourth cylinders from top to down as shown), an ignition coil  54   a  for second and third cylinders from the top is provided in an upper side of a side surface of the cylinder head cover  36 , and also, an ignition coil  54   b  for first and fourth cylinders from the top is provided in a lower side. 
     Still furthermore, a neutral switch  55  for detecting whether or not a shift position is neutral is disposed at a portion near the link mechanism  17  of the shift apparatus  15 . 
     As shown in FIG. 3, a crank angle sensor  56  for detecting an angle of revolution of the crankshaft  6  is provided near an outer peripheral surface of the flywheel magnet  29 . Further, an IAC (idle-air-control) solenoid valve  57  for adjusting an amount of air during the idling operation of the engine is disposed in the surge tank  42 , and an air bypass screw  58  is also arranged. Further, a full-close switch  60  executing an operation, at a time when a throttle valve  59  provided in an inner portion of the throttle body  41  is fully closed, is disposed in the throttle body  41 . 
     FIG. 4 is a block diagram of an engine system including the engine  5  shown in FIG.  3 . As shown in FIG. 4, an information obtained from each of the sensors and the switches is transmitted to a control system or unit  50 . In particular, the angle of revolution of the crankshaft  6  is transmitted from the crank angle sensor  56  to a revolution number detecting section  61  after an operation of an analogue-to-digital (A/D) conversion, and data of the engine revolution number obtained here is transmitted to a calculating section  62 . 
     Further, an information of position of the throttle valve  59  in the throttle body  41  is transmitted from the full-close switch  60  to a full-close position judging section  63  after an operation of the A/D conversion, and data of position of the throttle valve  59  obtained here is then transmitted to the calculating section  62 . 
     Furthermore, an information of a shift position of the shift apparatus  15  is transmitted from the neutral switch  55  to a shift position judging section  64 , and data of position of the shift apparatus  15  obtained here is then transmitted to the calculating section  62 . 
     Still furthermore, an information of temperature of the cylinder  24  and the exhaust manifold  44  is transmitted from the cylinder temperature sensor  52  and the manifold temperature sensor  53  to a temperature detecting section  65 , and data of temperature of the cylinder  24  and the exhaust manifold  44  obtained here is then transmitted to the calculating section  62 . 
     The information obtained from each of the sensors and the switches is calculated by the calculating section  62  to thereby transmit suitable control signals to the solenoid control section  66 , the ignition control section  67  and the fuel injection control section, respectively, so as to control the IAC solenoid valve  57  for adjusting the amount of air during the idling operation, the fuel injector  32  injecting the fuel within the intake port  30 , and the ignition coils  54   a  and  54   b  for igniting the ignition plug  26 . 
     By the way, in the case of the engine  5  for the outboard motor, the overheat of the engine  5  is generated, due to the shortage of the cooling water, at a time when the water intake port  18  for the cooling water is clogged by the algae or the water pump  19  gets out of order. In order to obviate this mater, the engine  5  is provided with an overheat control system or apparatus reducing the engine revolution number so as to restrict the increasing of the engine temperature. 
     FIG. 5 is a flow chart showing a flow of a control executed by the overheat control system, and FIG. 6 is a graph showing a temperature characteristic on the basis of this control. 
     With reference to FIGS. 5 and 6, since values of the temperature sensors of the cylinder  24  and the exhaust manifold  44  are always monitored by the control unit  50  as mentioned above, it is at first discriminated or judged whether values (WT) of the temperature sensors  52  and  53  are over a predetermined temperature of A° C., or not (step S 1 ). In this case, the values of the temperature sensors  52  and  53  may employ a temperature ascending slope (an ascending rate) in addition to an absolute temperature. 
     In the case that the values of the temperature sensors  52  and  53  are over the predetermined temperature (i.e., WT&gt;A° C.), it is discriminated that the engine  5  is in an overheat state, and it is discriminated whether a revolution number (Ne) of the engine  5  is equal to or more than a restriction (restricted) revolution number (α rpm) (Step  2 ). In this case, the revolution number of the engine  5  is always monitored by the control unit  50  as mentioned above. 
     In the case that the revolution number of the engine  5  is equal to or more than the restriction revolution number (i.e., Ne≧α rpm), the revolution number of the engine  5  is reduced by at least one of revolution number restricting controls including or among the misfire and the fuel stop around all the cylinders until the revolution number of the engine  5  becomes less than the restriction revolution number (Ne&lt;α rpm) (Step  3 ). 
     In this case, since all the cylinders are in the operating (combustion) state even when the revolution number of the engine  5  is reduced until becoming less than the restricted revolution number in response to the revolution number restricting control, the engine temperature is again increased due to a long time operation, thus being defective. 
     There may provide no problem in the case that such defect, for example, caused by the clogging of the water intake port  18  or like, can be easily solved. However, in the case that the defect can not be solved on the scene, for example, a roughness on the sea condition, a trouble of the water pump  19  or the like, it is obliged for the engine to be continuously used forcedly, so that a further temperature increase of the engine  5  will be caused, and hence, there causes a fear that an excessive damage may be applied to the engine main body, equipments such as electrical equipment  37  or the like arranged at the peripheral portion thereof. 
     Accordingly, after the revolution number of the engine  5  is reduced to a value less than the restricted revolution number in the step S 2  or the revolution number of the engine  5  is reduced to be less than the restricted revolution number in the step S 3 , the specific cylinder is controlled to be stopped by at least one means of the misfire and the fuel stop (step S 4 ). Under such operation stop control of the specific cylinder, a fresh and cool air passes through the specific cylinder of the engine  5  in the overheat state without burning to thereby promote the cooling from the inner portion of the engine. Thus, according to this manner, the temperature increase of the engine  5  is restricted and it becomes possible to continuously use the engine  5 . 
     Further, the cylinder controlled to be stopped is generally exploded in accordance with an order of 1-3-4-2 (first-third-fourth-second cylinders in arrangement) in the case of the four-stroke-cycle 4-cylinder engine  5 , for example, as in the described and illustrated embodiment. Accordingly, the combustion is executed at 360° CA (crank angle) by selecting the first and fourth cylinders or the second and third cylinders so as to obtain the same combustion interval as that of the 2-cylinder engine, whereby the revolution of the engine becomes stable. In this case, the specific cylinder can obtain a sufficient effect even in only one cylinder. 
     Further, in the case of a 3-cylinder engine, the specific cylinder will become any one of cylinders, and on the other hand, in the case of a two-stroke-cycle 4-cylinder engine, the first and second cylinders or the third and fourth cylinders may be selected. Here, in the case of the two-stroke-cycle engine, only the misfire control is effective for the stop control. 
     In this case, when the specific cylinder among a plurality of cylinders is controlled to be stopped (i.e., is subjected to operation stop control), there is a fear that the revolution of the engine  5  becomes unstable at a time of fully closing the throttle valve  59  in the throttle body  41  such as in the idling time, trolling time or like. Accordingly, when the specific cylinder is controlled to be stopped in the step S 4 , an idling (trolling) target revolution number (Nectp) of the engine  5  is set to a revolution number (β rpm) higher than a target revolution number at a normal time (step S 5 ). In this case, the target revolution number is executed by controlling the solenoid valve  57  by means of the control system  50 . 
     In the case that the reason why the overheat is canceled during the operation stop control to the specific cylinder and the values of the temperature sensors  52  and  53  are less than the defined temperature (WT&lt;B° C.), it is necessary to cancel the command of the operation stop control of the specific cylinder. However, in the case of suddenly canceling the stop control during this stop control of the specific cylinder, there may cause a fear that the revolution number of the engine  5  rapidly increases. Accordingly, it is detected by the neutral switch  55  whether or not the shift position of the shift apparatus  15  is in the neutral state, whereby the stop control of the specific cylinder is canceled (Step S 7 ) only in the case that the values of the temperature sensors  52  and  53  are less than the defined temperature and the neutral switch  55  is in an ON-state (the shift position is neutral) (Step S 6 ). Further, at this time, the idling (trolling) target revolution number is returned to the target revolution number at the normal (steady) operation period. 
     Even by reducing the revolution number of the engine  5  to be less than the restriction revolution number at a time when the engine  5  becomes in the overheat state, there is a case where the continuous use of the engine  5  is to be requested in some occasions or conditions, and it is impossible to completely prevent the temperature increase of the engine  5 . Further, since the revolution number restriction control is applied to all the cylinders at random, the revolution of the engine  5  becomes unstable. 
     Accordingly, as mentioned above, by controlling the specific cylinder so as to reduce the revolution number of the engine  5  to be less than the restriction revolution number and then to perform the operation stop control, it becomes possible to prevent the engine temperature from being increased, even if the engine is continuously driven. Then, the prevention of the increasing of the engine temperature results in the stable state or condition of the engine main body and the equipment such as the electronic equipment  37  and the like arranged in the periphery thereof. 
     Further, if the specific cylinder controlled to be stopped is previously set in correspondence to the type or mode of the engine  5  (for example, in the case of the four-stroke-cycle 4-cylinder engine  5 , the first and fourth cylinders or the second and third cylinders are selected as the specific cylinder), it is possible to obtain a stable engine revolution during the continuous use of the engine  5 . 
     Furthermore, since the idling (trolling) target revolution number during the operation stop control of the specific cylinder is set to the revolution number higher than the target revolution number at the normal time, it is possible to obtain the stable engine revolution even in the low revolution number range of the engine  5 , and it is also possible to prevent the engine stall or like. 
     Furthermore, at a time when the reason for the overheat is canceled and the values of the temperature sensors  52  and  53  are reduced to be less than the defined temperature, the operation stop control of the specific cylinder is canceled only at a time when the shift position of the shift apparatus  15  is in the neutral state. It is hence possible to prevent the defect or inconvenience caused by the rapid increase of the engine revolution number after canceling the stop control. 
     In the embodiment mentioned above, although there is provided a structure in which the present invention is applied to the engine  5  of the outboard motor  1 , it is possible to apply to an engine of a motor car, a motorcycle and the like as far as it belongs to the water-cooled type multi-cylinder engine.