APPARATUS AND METHOD FOR CONTROLLING A MECHANICAL SUPERCHARGER FOR A DIESEL ENGINE

Abstract: A control apparatus includes a detecting means (16) for detecting the position of an accelerator pedal (14) or an accelerator lever, a clutch (8) which is disposed between a diesel engine (1) and the mechanical supercharger (10), and a coupling / decoupling means (16) for coupling or decoupling a clutch (8) based on a signal from the detecting means (16). A control method includes the steps of detecting the stroke distance of the accelerator pedal (14) or the accelerator lever, and operating the mechanical supercharger (10) when the stroke distance detected ranges from a predetermined value in the vicinity of the full stroke to the full stroke. Thereby improving responsiveness in the initial stage of acceleration, and obtaining better normal running performance and hill-climbing ability.

Description: The present invention relates to an apparatus for controlling a mechanical supercharger for a diesel engine, and particularly to an apparatus for operating the mechanical supercharger when the fuel injection rate of the diesel engine has reached the range from a predetermined value to the maximum injection rate. Conventionally, in an engine for a vehicle mainly traveling with wheels, such as a car, a truck, a wheeled loader, a wheel crane, a supercharger has been used to reduce the engine size while increasing the output of the engine securing good acceleration. As for the supercharger (super charger), there is a mechanical supercharging method which uses part of the engine output, or power of other machinery, and there is a turbocharger supercharging method which uses exhaust gas. For this reason, as the first background with the mechanical supercharging method, a supercharger 40 is mechanically and directly connected to and driven by an engine 41 through gears 42 and 43, or through a belt or the like, as Fig. 14 illustrates. In the directly connected and driving type where air is supplied as illustrated in Fig. 15, in an area A where the engine speed is lower with a higher load, the amount of air which is supplied to the engine is insufficient. In an area B where the engine speed is higher with a lower load, the amount of supply is excessive, increasing the driving loss of the supercharger 40. There has been a differential driving method proposed for driving the supercharger 40 as shown in Fig. 16. In the differential driving method (I) in Fig. 16, a planetary carrier 43 is fixed to and connected to an output shaft 41a of the engine 41, and usually, three of planetary gears 44 are rotatably attached to the planetary carrier 43 equidistantly from one another. A sun gear 45 is meshed with the inner side of three planetary gears 44, and a ring gear 46 is meshed with the outer side of three planetary gears 44. At the inside of the sun gear 45, the output shaft 41a of the engine 41 is rotatably disposed. A gear 47 is provided at one end of the sun gear 45, and a driving gear 48 for the mechanical supercharger 40 is meshed with the gear 47. A shaft of a power transmission system 50 for a vehicle is connected to a ring gear 46, and the mechanical supercharger 40 is rotated, varying depending on the load of the power transmission system. A differential driving method ( II ) in Fig. 17 for driving a supercharger by a differential driving method similar to the above has the configuration subsequently similar to the above. In the differential driving method ( II ), the ring gear 46 is provided with a brake 46a which utilizes electricity, dry condition, oil pressure, or the like. The rotational force of the mechanical supercharger 40 is controlled based on the difference in strength of drag resistance caused by the brake 46a. Next, as a second background, there is construction machinery which requires higher output at lower and medium engine speed, or there is construction machinery which requires higher output at higher engine speed, depending on a kind of machine used. For example, there is machinery such as hydraulic shovel or the like which needs higher output in an area Qa with the engine rotating at higher speed, as shown in Fig. 18. There is machinery such as a bulldozer, a damp truck, a wheeled loader, a motor grader, or the like which requires higher output at lower and moderate engine speed as shown in Fig. 19. When classifying the uses of each machine's engine according to each load, engine speed, the frequencies of use, the construction machinery's engine described above, is more frequently used in areas Fa and Fb. In the vehicles with tires such as a car, a truck for transporting cargo, a bus, a damp truck, a forklift, a pleasure boat, and the like, and in a fishing boat and a ship, the engines are more frequently used in areas Fb and Fc. In a word, in construction machinery, the engine is more frequently used under a medium or a higher load, while in a vehicle with tires and a ship, the engine is more frequently used under a lower or a medium load. Further, as a third background, in the machinery which is required of higher engine output in the entire area, there is a method using both of a turbocharger and a mechanical supercharging methods. In this case, as Fig. 21 shows, at the lower and medium engine speed, a mechanical supercharging method is used to produce higher output as shown by a solid line Ua, while at the higher engine speed, the mechanical supercharger is stopped to reduce driving loss, and a turbo charger is used to produce higher output as shown by an alternate long and short dash line Ub. A dotted line Uc shows output torque of the engine in a non-supercharging condition. Alternate long and two short dashes lines Ya and Yb show matching lines of a torque converter when driving a vehicle using torque converter. The alternate long and two short dashes line Ya shows e=0, while the alternate long and two short dashes line Yb shows e ≒ 1. Incidentally, in the drawing, the axis of abscissa shows engine speed, and the axis of ordinate shows output torque (load) of the engine. The disadvantages which is designed to be eliminated in the first background are as follows: (1) The directly connected and driving type of supercharger in Fig. 14 is more frequently used for an engine with a lower and medium load in a vehicle with traveling tires, and a ship. In an air supplying condition which is required for an engine with a lower and medium load, this type frequently causes to an excessive and unnecessary driving loss of the supercharger. As the result, fuel consumption per hour is greater as compared to a non-supercharged engine and a turbo supercharging engine. (2) In the conventional differential driving method (I), a load on a vehicle is great while the vehicle is being accelerated from a standing start (acceleration from a standstill), therefore the rotational speed of the mechanical supercharger increases at first, and after sufficient amount of air enters the engine, the vehicle starts to run. Accordingly, an operator receives slow response in the early stage of pressing down on the accelerator, specifically, an operator has complaint of poor responsiveness. (3) In the differential driving method (II), part of engine driving force is lost as thermal loss due to the dragging resistance of a brake and the like, resulting in a disadvantage that fuel efficiency is decreased. The disadvantages in the second and the third backgrounds are as follows: (4) As Fig. 21 shows, in the method using both of a turbocharger and a mechanical supercharging methods, in a truck for transporting cargo, a bus, a damp truck, a folk lift, or the like, which uses a torque converter, the torque converter (e=0) does not match the higher output Ua produced by a mechanical supercharging method, and there is a disadvantage that the output by a supercharging method cannot be used. In addition, at higher speed of the engine, higher output is produced by a turbocharger as shown by the alternate long and short dash line Ub, but an engine in a much smaller size with much higher output and efficiency is desired. US-A-4 519 373 discloses a supercharger including a compressor system which is driven through an electromagnetically actuated variable slipping wet clutch to supply boost to an engine in the form of compressed air according to load requirement by varying the drive torque via the clutch system to the compressor system. US-A-5 256 109 describes a drive device with variable transmission ratio for driving an auxiliary aggregate of a motor vehicle, the drive device comprising a belt pulley having a chamber connected to a reservoir of a hydraulic medium with its centrifugal action being used to change the speed of the driven shaft, wherein the output speed of the drive device is additionally variable by applying a supporting pressure to the chamber. The present invention is made to eliminate the disadvantages of the conventional art, and the first object is to eliminate slow response in an initial stage of acceleration and to improve the responsiveness by increasing the output of an engine in an area in which greater driving output is required at a time of starting a vehicle, at a time of climbing a hill, or the like. In a vehicle using a torque converter, matching performance with the torque converter is improved, and the driving torque is improved. Another object is to obtain the acceleration ability at a start from a standstill which is the same as the engine with a larger bore diameter, better normal running performance, obtain better hill-climbing performance, and improvement in fuel efficiency. According to the invention, this is achieved by the features of the appended claim. An apparatus for controlling a mechanical supercharger for a diesel engine in accordance with the present invention is an apparatus for controlling a mechanical supercharger for a diesel engine including an accelerator pedal or an accelerator lever, a governor interlocking with the accelerator pedal or the accelerator lever, an injection pump which is controlled by the governor, a diesel engine which receives fuel from the injection pump and produces an output, and a mechanical supercharger which is driven by the diesel engine, and including a detecting means for detecting the position of the accelerator pedal or the accelerator lever, a clutch which is disposed between the diesel engine and the mechanical supercharger, and a coupling / decoupling means for coupling or decoupling the clutch based on a signal from the detecting means. According to the above configuration, the clutch is coupled in accordance with the position of the accelerator pedal. For example, when the fuel injection rate is equal to a predetermined value or more, the clutch is coupled and the mechanical supercharger is operated. As the result, sufficient amount of air can be supplied when-the engine needs much air with a higher load, and higher output can be obtained. In addition, since the mechanical supercharger is not operated with lower and medium load with which the engine is more frequently used, driving loss is eliminated. Further, the apparatus for controlling a mechanical supercharger for a diesel engine includes a hydraulic pump which is driven by the diesel engine, while the clutch is a hydraulic clutch and a planetary gear train which are disposed between the diesel engine and the mechanical supercharger, and the coupling / decoupling means comprises a solenoid valve which is actuated on receiving a signal from the detecting means, and which provides or stops a supply of pressure oil from the hydraulic pump to the hydraulic clutch to couple or decouple the hydraulic clutch. According to the structure, by using the planetary gear train, greater reduction ratio can be obtained, and the driving device of the mechanical supercharger becomes small in size. In addition, by using the hydraulic clutch, the durability of the driving device of the mechanical supercharger is improved even in a vehicle in which the driving device of the mechanical supercharger is frequently used in heavy work. Further, the oil hydraulic clutch is provided with a torque variance buffering means at the fixed end side of the hydraulic clutch. According to the structure, twisting vibrations of the engine can be reduced by the torque variance buffering member. Thereby eliminating the disadvantages which are caused as the result that the twisting vibrations transmit to the mechanical supercharger through the planetary gear train, for example, the disadvantage of breaking the gears of the planetary gear train or the mechanical supercharger, and the disadvantage of causing pitching on the surfaces of the gears. The detecting means outputs a signal to the coupling /decoupling means or to the solenoid valve, and couples the hydraulic clutch, when the detected position is in the vicinity of the maximum injection rate of the fuel. According to the structure, when the load on the engine is higher, sufficient air can be supplied as necessary by operating the mechanical supercharger, therefore higher output can be obtained. With lower and medium load with which the engine is more frequently used, the supercharger is not operated, therefore driving loss can be eliminated. According to the structure, the output of the engine is increased in an area in which a greater driving force is needed at the time of starting from a standstill, or at the time of climbing a hill, therefore the responsiveness is improved. In a vehicle using a torque converter, matching ability with the torque converter is improved. Fig. 1 is a block diagram of an Example not according to the present invention, but which, is useful for understanding the present invention; Fig. 2 is a diagram for explaining the relationship among an engine speed, fuel injection rate of minimum-maximum governor (M - M governor), and the amount of acceleration in accordance with the example of figure 1 and the present invention; Fig. 3 is a block diagram of a first embodiment of the present invention; Fig. 4 is a diagram for explaining the relationship among the engine speed, the output torque of the engine, and a period in which a mechanical supercharger is operated in accordance with the present invention; Fig. 5 is a diagram for explaining the relationship among the engine speed, the fuel injection rate of a mechanical RSV governor, and the amount of acceleration of the present invention; Fig. 6 is a diagram for explaining the relationship among the engine speed (constant speed at the time of producing higher speed), the fuel injection rate of an electronically controlled RSV governor, and the amount of acceleration of the present invention; Fig. 7 is a diagram for explaining the relationship among the engine speed (varying speed at the time of producing higher speed), a electronically controlled RSV governor, and the amount of acceleration of the present invention; Fig. 8 is a block diagram of a second embodiment of the present invention; Fig. 9 is a diagram for explaining the relationship among the engine speed, the output torque of the engine, and a period in which the mechanical supercharger is operated in the second embodiment of the present invention; Fig. 10 is a diagram for explaining the relationship between vehicle speed and tractive force when a control apparatus of the present invention is applied to a crane truck or the like; Fig. 11 is a diagram for explaining the relationship between the engine speed and the output torque when the control apparatus of the present invention is applied to a ship or the like; Fig. 12 is an explanatory diagram of the attitude in each condition of a ship using the control apparatus of the present invention; Fig. 13 is a block diagram showing a torque variance buffering means according to the present invention; Fig. 14 is a block diagram of the mechanical supercharger of the conventional diesel engine; Fig. 15 is a diagram for explaining the relationship among the engine speed of the conventional mechanical supercharger, the mean effective pressure, and the amount of air of the mechanical supercharger; Fig. 16 is a block diagram of the conventional mechanical supercharger for an diesel engine, which is driven by an planetary gear train; Fig. 17 is a block diagram in which the conventional mechanical supercharger is driven by the planetary gear train and a braking device is included; Fig. 18 is a diagram for explaining the output line of the conventional diesel engine which is required of higher output when used in a hydraulic shovel or the like; Fig. 19 is a diagram for explaining the output line of the conventional diesel engine which is required of higher output at lower and medium speed; Fig. 20 is a diagram for explaining the usage of the conventional diesel engine according to the machines in which the engine is used; and Fig. 21 is a diagram for explaining the relationship between the engine speed and the output torque of the engine when both of a mechanical supercharger and a turbocharger are used in the conventional diesel engine. A preferable embodiment in accordance with the present invention will be described below with the reference to the attached drawings. Fig. 1 is a diagram showing an example not according to the present invention, but which, is useful for understanding the present invention, and is a block diagram of a system around a diesel engine 1 (hereinafter referred to as an engine 1) which is provided on a vehicle with tires or the like, or on a ship or the like, and which controls the output by using a supercharger 10 and a minimum-to-maximum governor. The engine 1 consists of a suction system 2 for supplying air, a fuel control unit 3, an engine body 1A, and an exhaust system which is not shown in the drawing. The suction system 2 consists of a suction passage 4, an electromagnetic clutch (clutch) 8, a check-valve 9, and a mechanical supercharger 10. The suction system 2 is provided with the suction passage 4 which guides air to the engine 1. The suction passage 4 branches into a first branch passage 4a and a second branch passage 4b at a branch portion 5, and both of the branch passages 4a and 4b meet at a meeting portion 5 to be a suction passage 7, a single passage, once again. The suction passage 4 upstream to the branch portion 5 is provided with an air cleaner which is not shown in the drawing. The first branch passage 4a is provided with the mechanical supercharger 10 which is driven through a gear 1b by the engine body 1A by the medium of the electromagnetic clutch 8. The second branch passage (bypass passage) 4b which bypasses the mechanical supercharger 10 is provided with the check-valve 9, having a function of preventing the air pressurized by the mechanical supercharger 10 from escaping upstream during supercharging. The fuel control unit 3 consists of an in-line fuel injection pump 11, a minimum and maximum speed control type of governor 12 (hereinafter referred to as M - M governor 12), and an accelerator pedal 14, which have been conventionally used. A lever 13,which increases and decreases fuel injection rate, is attached to the M - M governor 12, and interlocks with the accelerator pedal 14 by means of a rod (or a wire) 15. The rod 15 is provided with a switch (detecting means) 16 for detecting the degree of opening of the accelerator pedal 14. In addition, a switch 16 can connect and disconnect a wiring 17 of the electromagnetic clutch 8 and a wiring 19 of a battery 18 in correspondence to the degree of opening, and a switch 16 also forms a coupling / decoupling means for coupling or decoupling the electromagnetic clutch 8. Incidentally, the switch 16 in the embodiment combines a detecting means and a coupling /decoupling means, but these means can be separated as a detecting means 16 and a coupling / decoupling means 16. An accelerator lever can be used instead of the accelerator pedal 14 which is used in the example. Next, the operation of the example of figure 1 will be explained with reference to Fig. 2. In Fig. 2, the axis of abscissa shows the speed of the engine 1, and the axis of ordinate shows the fuel injection rate, while a solid line Za shows the degree of opening of the accelerator pedal 14, specifically, the stroke distance of the accelerator pedal 14. The operation of the mechanical supercharger 10 is set based on the degree of opening of the accelerator pedal 14. Explaining the relationship between the characteristics of fuel injection rate of the M - M governor 11 and the degree of opening of the accelerator 14 with reference to Fig. 2, the mechanical supercharger 10 is operated in an area R (the area shown by dots) in which the accelerator opening degree is a predetermined degree, for example, from 2/3 to 3/3 (FULL). The operation of the mechanical supercharger 10 is stopped when the accelerator opening degree is below 2/3, and the engine 1 is operated without supercharging. Specifically, the supercharger is operated only when the load is higher, and the supercharger is not operated with a lower and medium load with which the engine is more frequently used, so that the driving loss is reduced. As for the actuation of the mechanical supercharger 10, when the degree of opening of the accelerator pedal 14 is 2/3 or over, electric current passes as the result of the operation of the switch 16 which detects the accelerator opening degree, and electric current passes from the battery 18 to couple the electromagnetic clutch 8 and then to rotate the mechanical supercharger 10. When the degree of opening of the accelerator pedal 14 is below 2/3, the electromagnetic clutch 8 is decoupled as the result of the operation of the switch 16 which detects the accelerator opening degree, and the rotation of the mechanical supercharger 10 is stopped. As for the air flow during the supercharging operation, air flows from the suction passage 4, which leads to the engine 1, to the branch portion 5, the first branch passage 4a, and the mechanical supercharger 10, in which the air is pressurized, and the air passes through the meeting portion 6 and the suction passage 7 to be supplied to the engine 1. The check-valve 9 is provided at the portion between the meeting portion 6 and the second branch passage 4b, therefore air does not flow backward. As for the air flow during the non-supercharging operation, air passes from the suction passage 4 through the branch portion 5, the check-valve 9, the second branch passage 4b, the meeting portion 6, and the suction passage 7 to be supplied to the engine 1. Next, a first embodiment of the present invention will be explained with reference to the drawings. In Fig. 3, a planetary gear train 20 is provided between the engine body 1A and the mechanical supercharger 10, and a hydraulic clutch 23 is provided between an outer circumference of a ring gear 21 of the planetary gear train 20 and an outer wall fixed end 22. In the planetary gear train 20, a planetary carrier 24 is secured and connected to the output shaft 1a of the engine 1 through the gear 1b, and usually, three of planetary gears 25 are rotatably attached to the planetary carrier 24 equidistantly from one another. The ring gear 21 is meshed with the outer side of the three of the planetary gears 25, and is rotatably disposed at a shaft 1c of the gear 1b, while in the inner side thereof, a sun gear 26 drives the mechanical supercharger 10. A wet and multiple disc clutch is used as a hydraulic clutch 23, which is disposed between the ring gear 21 of the planetary gear train 20 and the outer wall fixed end 22. The hydraulic clutch 23 connects to a solenoid valve (coupling /decoupling means) 28 through a hydraulic piston 27, and is coupled and decoupled by operating the hydraulic piston 27 with the solenoid valve 28. The solenoid valve 28 is connected to a hydraulic pump 29 which is driven by the output shaft 1a of the engine 1. The hydraulic pump 29 takes in oil from an oil tank of the engine 1, or another oil tank which is provided below the planetary gear train 20, and supplies the oil to the hydraulic piston 27 through the solenoid valve 28. In the first embodiment, the switch 16 operates as a detecting means. Next, the operation will be explained with reference to Fig. 2. As for the actuation of the mechanical supercharger 10, when the degree of opening of the accelerator pedal 14 reaches a predetermined degree, for example, the degree equal to 2/3 or more, electric current flows as the result of the operation of the switch 16 which detects the opening degree, and electric current flows from the battery 18 to actuate the solenoid valve 28. Oil flows from the hydraulic pump 29 to the hydraulic piston 27, and the hydraulic clutch 23 is coupled to drive the mechanical supercharger 10. The hydraulic clutch 23, which is of a wet and multiple disc type, is superior in durability, with less electric power consumption of the solenoid valve 28, and a greater speed up ratio can be obtained by using the planetary gear train, reducing the sizes of the planetary gear train 20 and the mechanical supercharger 10. As described above, in both of the example and the first embodiment, the mechanical supercharger 10 is actuated by coupling the electromagnetic clutch 8 or the hydraulic clutch 23 based on a signal from the switch 16 which detects the position of the accelerator pedal 14 when the fuel injection rate is in the vicinity of the maximum injection rate. Specifically, the mechanical supercharger 10 is operated only when the supply of air is needed in the engine 1 with a higher load. Accordingly, with a lower, or medium load with which the engine is more frequently used, and in which the supply of air is not needed, the mechanical supercharger 10 is not operated, therefore there is no driving loss. Accordingly, the mechanical supercharger 10 produces greater torque of low speed, as compared to the conventional turbocharger (not illustrated) as Fig. 4 shows, and provides a supercharging method with excellent responsiveness at the time of acceleration. In Fig. 4, the axis of abscissa shows the speed of the engine 1, and the axis of ordinate shows the output torque, while an alternate long and two short dashes line Zb shows the output torque during non-supercharging operation, and a solid line Zc shows the output torque produced by supercharging by the mechanical supercharger 10. A dotted line shows an output torque Zd produced by supercharging by a turbocharger. In the example and the first embodiment described above, the M - M governor is used in the explanation, but an all-speed governor can be used as follows. Fig. 5 is a control diagram of the mechanical supercharger 10 when using a mechanical RSV governor (RSV governor is a governor made by Bosch Ltd., in Germany) which is not illustrated in the drawing. Similarly to Fig. 2, the axis of abscissa shows the engine speed, and the axis of ordinate shows the fuel injection rate, while the oblique lines in the drawing show the stroke, specifically, the degree of opening of the accelerator lever, or the accelerator pedal. For example, 5/5 (FULL) shows the operation at the full stroke, and 4/5 shows the operation at 80 % of the entire stroke. In Fig. 5, the mechanical supercharger 10 is operated in the area with a predetermined acceleration ) opening degree, for example, from 3/5 to 5/5 (FULL)(the portion with oblique lines in the drawing). With the acceleration opening degree of less than 3/5, the operation is stopped, and the engine 1 is driven without supercharging. Specifically, the supercharger is used only when the load is higher, and the supercharger is not operated with a lower or medium load with which the engine is more frequently used, therefore driving loss is reduced. Figs. 6 and 7 are control diagrams of the mechanical supercharger 10 when using an electronically controlled RSV governor. In Figs. 6 and 7, when the fuel injection rate is below a predetermined amount Qs, the governor functions as an all-speed governor as in Fig. 5, and when the fuel injection rate is equal to the predetermined amount Qs or more, the governor functions as a minimum-maximum speed governor (M - M governor) as in Fig. 2. In Fig. 6, in a M - M area (the area except the portion in which the all-speed governor type of operation is carried out) in which the fuel injection rate is equal to the predetermined amount Qs or more, the engine speed Nc is kept constant even if the fuel injection rate is changed. In Fig. 7, in the M - M area (the area except the portion in which the all-speed governor type of operation is carried out) in which the fuel injection rate is equal to the predetermined amount Qs or more, the engine speed increases from an engine speed Ne to an engine speed Nf when the fuel injection rate is increased. In Figs. 6 and 7, the mechanical supercharger 10 is operated in the M - M area in which the fuel injection rate is equal to the predetermined amount Qs or more. For example, with the accelerator opening degree being below 2/3, the operation is stopped and the engine 1 is driven without supercharging, while with the accelerator opening degree being equal to 2/3 or more, the mechanical supercharger 10 is operated. Next., a second embodiment of the present invention will be explained with reference to the drawings. Fig. 8 shows the second embodiment, and a turbocharger 30 is added to the suction side of the mechanical supercharger 10 in the first embodiment. In Fig. 8, the suction passage 4 of the mechanical supercharger 10 is connected to the turbocharger 30, and a suction air blower 30a of the turbo charger 30 takes in outside air from an air cleaner which is not illustrated in the drawing. The turbo charger 30 is connected to an exhaust pipe 31 from the engine 1, and an exhaust blower 30b of the turbocharger 30 receives exhaust gas from the engine 1, rotating and discharging the exhaust gas from the engine 1 to the outside through a muffler 32. In the first embodiment described above, the solenoid valve 28 is switched as the result of passing electric current by operating the switch 16 based on the degree of opening of the accelerator pedal 14, but in the second embodiment, a stroke distance detecting sensor 33 for detecting the degree of opening of the accelerator pedal 14 is additionally provided, and a signal therefrom is inputted into a coupling / decoupling command means 34 such as a controller or the like. The coupling /decoupling command means 34 outputs the command to switch, to the solenoid valve 28, and switches the solenoid valve 28 which couples and decouples the hydraulic clutch 23. Accordingly, in the second embodiment, the coupling / decoupling means consists of the coupling / decoupling command means 34 and the solenoid valve 28. The coupling / decoupling command means 34 can be provided with a change-over switch 35 which issues the command to switch the solenoid valve 28 to connect to the hydraulic clutch 23, in order to actuate the mechanical supercharger 10. In the first embodiment, the M - M governor 12 is used, but in the second embodiment, an electronically controlled RSV governor 36 is used. The RSV governor 36 is connected to the coupling /decoupling command means 34, and the coupling / decoupling command means 34 outputs a command to the RSV governor 36, linking to a signal received from the stroke distance detecting sensor 33. The RSV governor 36 supplies the engine body 1A with the discharge from the fuel injection pump 11 corresponding to the signal. As the result, the output torque of the engine 1 is increased. The operation in the above configuration will be explained with reference to Fig. 9. The axis of abscissa sows the speed of the engine 1, and the axis of ordinate shows the output torque. An alternate long and short dash line Ta shows the output torque during non-supercharging operation, and a dotted line Tb shows the output torque produced by supercharging with the turbo charger 30, while a solid line Tc shows the output torque produced by supercharging with the mechanical supercharger 10. An alternate long and two short dashes line e in the drawing shows the matching line of the torque converter. When the engine 1 is started to be rotated and actuated by turning on (ON) a starting switch which is not illustrated in the drawing, the exhaust gas in the engine 1 enters the exhaust blower 30b from the exhaust pipe 31, and rotates the turbocharger 30. The suction air blower 30a is rotated by the rotation of the turbocharger 30, and takes in the outside air from the air cleaner to supply the air to the engine 1. At this time, since the mechanical supercharger 10 does not rotate, pressurized air taken in the turbocharger is supplied to the engine 1 through the suction passage 4, the check-valve 9, the second branch passage 4b, the meeting portion 6, and the suction passage 7. As the result, the output torque Tb during the rotation of the turbo 30 of the engine 1 increases as shown by the dotted line in Fig. 9 as compared to the torque Ta during non-supercharging operation. Further, an operator press down the accelerator 14 in order to cope with a load, or in order to increase the speed of the engine 1 to increase the speed of the vehicle. When the accelerator 14 is pressed down, and the degree of opening reaches a predetermined set stroke distance, for example, the accelerator opening degrees shown in Fig. 2, 5, 6, or 7, a signal is inputted into the coupling / decoupling command means 34 by the stroke distance detecting sensor 33 for detecting the degree of opening, and the coupling / decoupling command means 34 receives the signal, and outputs the command to switch to the solenoid valve 28. The solenoid valve 28 is actuated, and oil flows from the hydraulic pump 29 to the hydraulic piston 27. The hydraulic clutch 23 is coupled, and the mechanical supercharger 10 starts rotational drive. As the result, the pressurized air taken in the turbocharger 30 enters the mechanical supercharger 10 from the suction passage 4, and then the pressurized air which is further pressurized is supplied to the engine 1 through the meeting portion 6 and the suction passage 7. As the result, the output torque Tc during the rotation of the turbo 30 of the engine 1 and the mechanical supercharger 10 further increases to be higher as shown by the solid line Tc in Fig. 9. In the above embodiment, when the accelerator opening degree reaches a predetermined value, the accelerator opening degree is detected by the stroke distance sensor 33 for detecting the degree of opening, and rotationally drives the mechanical supercharger 10. However, it can be constructed in such a way as an operator can switch the solenoid valve 28 to couple the hydraulic clutch 23 by pressing the change-over switch 35 which may be a push-bottom switch as necessary, and to increase the amount of air to be supplied to the engine 1 by rotationally driving the mechanical supercharger 10 while increasing the fuel according to the accelerator opening degree, so that much higher output is produced. The engine 1, which is supercharged by the mechanical supercharger 10 and the turbocharger 30 as described in the above, and which has the output torque increased as shown by the solid line Tc, has great effects if used as the engine of, for example, crane truck or the like adopting a torque converter, or the engine of a ship. Incidentally, in the above, the first embodiment is used in the explanation, but it goes without saying that it is suitable to additionally provide the turbocharger 30 in the example. Next, the engine 1 used in a crane truck will be explained. First, at the time of starting the vehicle with greater weight, an operator presses down the accelerator pedal 14 to a predetermined set stroke distance (accelerator opening degree) or more. As the result, the torque converter (not illustrated) stops the output side, or decreases the rotation of the output side, and the matching line of the torque converter is on e≒0 shown in Fig. 9. Accordingly, the matching point with the output torque Tb during the rotation of the turbo 30 is at a point Ma, and the matching point with the output torque Tc during the rotation of turbo 30 and the mechanical supercarger 10 is at a point Mb. The tractive force which is outputted from the torque converter at this time is a tractive force Fa at the point Ma of the output torque Tb when rotating the turbo 30, and is a tractive force Fb at the point Mb of the output torque Tc when rotating both of the turbo 30 and the mechanical supercharger 10, as shown in Fig. 10. For example, the tractive force Fb, when operating both of the turbo 30 and the mechanical supercharger 10, increases by some 20 % in tractive force, as compared to the tractive force Fa when only rotating the turbo 30. The tractive force can increase by some 20 % during a hill climbing, resulting in the improvement in hill-climbing ability. When running at high speed (for example, when a crane truck or the like is moving forward in the second gear), the matching line of the torque converter becomes e≒0.95 as shown in Fig. 9. Accordingly, the matching point with the output torque Tb during the rotation of the turbo 30 is at a point Na, and the matching point with the output torque Tc during the rotation of both of the turbo 30 and the mechanical supercharger 10 is at a point Nb. A vehicle speed V which the torque converter outputs at this time is at a vehicle speed Va at the point Na of the output torque Tb during the rotation of the turbo 30, and the vehicle speed V is at a vehicle speed Vb at the point Mb of the output torque Tc during the rotation of both of the turbo 30 and the mechanical supercharger 10. For example, in a crane truck, the vehicle speed Vb when operating both of the turbo 30 and the mechanical supercharger 10 is 65 km / h, increasing from 54 km /h, compared to the vehicle speed Va during the rotation of the turbo 30, resulting in an increase by some 20 % in speed. When comparing the sizes of the engine 1, by providing both of the turbocharger 30 and the mechanical supercharger 10, the output of the engine measuring 108 mm in bore diameter with six cylinders can be equal to the output of the engine which is provided with the turbocharger 30 and which measures 125 mm in bore diameter with six cylinders, and the engine measuring 108 mm in bore diamer can obtain the acceleration at the start from a standstill similar to the engine measuring 125 mm in bore diameter, and can attain better normal running performance, hill-climbing ability, and the improvement in fuel efficiency. Normal running performance, or hill-climbing ability is especially improved by increasing the amount of pressing down an accelerator as necessary, or by pressing a push-bottom to rotate the mechanical supercharger 10 to increase the output and to increase the hill-climbing ability or vehicle speed by some 20 %. The engine 1 functions as an engine with a small piston displacement when decoupling off the hydraulic clutch 23 of the mechanical supercharger 10 during partial driving, therefore the fuel efficiency can be improved as compared to an engine (in the above example, bore diameter of 125 mm) which produces the similar amount of output to the engine 1. Next, the engine 1 used in a ship will be explained. Fig. 11 is an explanatory diagram of the engine 1 used in a ship 39 (see Fig. 12), and the output lines Ta, Tb, and Tc are the same as those in Fig. 9. In Fig. 11, the axis of abscissa shows the speed of the engine 1, and the axis of ordinate shows the output torque (proportional to tractive force). An alternate long and two short dashes line W in the drawing is a required torque diagram of the ship 39, and Wa shows the required torque at the time of starting, while Wb shows the required torque before planing, and Wc shows required torque after planing. Fig. 12 shows the attitude of the ship 39, and Wa at the starting time shows the ship 39 stopping on the water line at a predetermined depth. The Wb before planing shows a condition in which the ship 39 travels at a speed below a predetermined speed with the front part of the ship floating a little and with the resistance of water being the greatest. The Wc after planing shows a condition in which the ship 39 travels at a speed equal to a predetermined speed or more with the front part of the ship 39 floating a little and with the resistance of water being the smallest. The ship 39 at this time can obtain higher speed similarly to the speed Vb of a crane truck, as the result of coupling the hydraulic clutch 23 of the mechanical supercharger 10 and producing the engine output Nb of a greater piston displacement. At the time of starting, higher torque can be outputted in response to lower speed and higher load which corresponds to the area with the greatest water resistance at the Wb before planing. The acceleration at the start from a standstill, better normal running performance, and improvement in fuel efficiency can be attained in the same way as the crane truck described above. In the first and second embodiments described above, the wet and multiple disc type hydraulic clutch 23 is provided with a torque variance buffer member (torque variance buffering means) 37 between the ring gear 21 of the planetary gear train 20 and the outer wall fixed end 22 as Fig. 13 shows. The torque variance buffer member 37 consists of a spring 36 which is inserted between a movable plate 21a attached to the ring gear 21 and a fixed plate 37 which is attached to the outside wall fixed end 22a. It is suitable that the spring 36 has an elastic body such as a coil spring, a belleville spring, or rubber. According to the configuration described above, breakage of the gears of the planetary gear train 20 and of the mechanical supercharger 10, and pitching on the surface, which are caused by the twisting vibration of the engine 1 that is transmitted to the mechanical supercharger 10 through the planetary gear train 20, can be prevented as the result of reducing the twisting vibration with the torque variance buffer member 37. In the explanation of the embodiments, in the example and the first embodiment, the accelerator pedal 14 and the M - M governor 12 are interlocked by means of the rod 15, but electrical control can be performed by providing the coupling / decoupling command means 34 such as the stroke distance detecting sensor 33 and a controller as in the second embodiment. In the second embodiment, the M - M governor 12 can be used. The present invention is useful as an apparatus for controlling a mechanical supercharger for a diesel engine by which the response in the initial stage of the acceleration, and the responsiveness can be improved, and by which better normal running performance, hill-climbing performance, and better fuel efficiency can be obtained.

Claims: An apparatus for a mechanical supercharger (10) for a diesel engine (1) including an accelerator pedal (14) or an accelerator lever, a governor (12) interlocking with said accelerator pedal (14) or said accelerator lever, an injection pump (11) which is controlled by said governor (12), a diesel engine (1) which receives fuel from said injection pump (11) and produces an output, and a mechanical supercharger (10) which is driven by said diesel engine (1), comprising: a detecting means (16; 33) for detecting the position of said accelerator pedal (14) or said accelerator lever; a wet and multiple disc type of hydraulic clutch (23) which is disposed between said diesel engine (1) and said mechanical supercharger (10), and which is provided with a torque variance buffering means (37) at the fixed end side thereof; a planetary gear train (20) which is disposed between said wet and multiple disc type of hydraulic clutch (23) and said mechanical supercharger (10), and which drives said mechanical supercharger (10); a hydraulic pump (29) which is driven by said diesel engine (1); and a solenoid valve (28) which is actuated on receiving a signal from said detecting means (16; 33), and which provides or stops a supply of pressure oil from said hydraulic pump (29) to said wet and multiple disc type of hydraulic clutch (23) to couple or decouple said wet and multiple disc type of hydraulic clutch (23).

Inventors: OZAWA GODO, OZAWA, GODO, OZAWA, Godo Komatsu Ltd. Oyama Plant
Applicants: KOMATSU MFG CO LTD, KOMATSU LTD.
Application year: 1996
Main classification: F02B39
IPC codes: F02B33, F02B39, F02B37