Abstract:
The purpose of the present invention is to provide an auxiliary braking device of a vehicle which obtains braking force corresponding to the amount of pressing of an accelerator pedal even during an operation of the auxiliary braking device and prevents frequent repetition of the acceleration and deceleration, to attain a fuel saving operation. Therefore, in the present invention, a vehicle electronic control unit ( 10 ) and other electronic control units ( 20, 30 ) are provided, the vehicle electronic control unit ( 10 ) and the other electronic control units are connected with each other by an in-vehicle communication system (L 123 ), and an auxiliary brake switch position detection device ( 5 S) that detects a switch position of an auxiliary brake switch ( 5 ) and an accelerator pedal pressing amount measurement device ( 4 S) that measures the amount of pressing of the accelerator pedal ( 4 ) are provided.

Description:
TECHNICAL FIELD 
     The present invention relates to an auxiliary braking device of a vehicle. More particularly, the present invention relates to at least one of an exhaust brake of an engine and a retarder for obtaining a braking force by a generator set on a propeller shaft. 
     BACKGROUND ART 
     Various auxiliary braking devices have been proposed (See Patent Literature 1 and Patent Literature 2, for example). 
     Patent Literature 1 and Patent Literature 2 are both constructed such that the auxiliary braking device is not operated during an operation of an accelerator pedal (See  FIG. 5 ). 
     Therefore, according to such auxiliary braking device, if the accelerator pedal is pressed while the auxiliary braking device is operating, a vehicle stops braking and changes to an acceleration state instantly from a deceleration state, and a shock occurs in the vehicle. 
     In the vehicle provided with the auxiliary braking device with such constructions, repetition of acceleration/deceleration increases, a frequency of coasting decreases and a fuel consumption of the vehicle deteriorates on a flat road when an inter-vehicle distance to a preceding vehicle frequently increases/decreases while following the preceding vehicle or on a road in mountains with continuous ups and downs. 
     Since acceleration/deceleration increase, shifting up and shifting will be repeated in a vehicle provided with an automatic transmission, which might give a sense of discomfort to a driver. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Application Non-examined Publication Gazette No. H08-282329 
     Patent Literature 2: Japanese Patent Application Non-examined Publication Gazette No. 2000-35114 
     SUMMARY OF INVENTION 
     Technical Problem 
     The present invention was proposed in view of the above described prior art problems and has an object to provide an auxiliary braking device of a vehicle which can obtain a braking force according to an amount of pressing of an accelerator pedal even during an operation of the auxiliary braking device, so as to prevent frequent repetition of acceleration and deceleration and to realize a fuel saving operation. 
     Solution to Problem 
     An auxiliary braking device ( 100 ) of a vehicle of the present invention has a vehicle electronic control unit (vehicle ECU  10 ) and other electronic control units (ECU: an engine ECU  20 , a retarder ECU  30 , a transmission ECU and the like, for example), and the vehicle electronic control unit ( 10 ) and the other electronic control units ( 20 ,  30 ) are connected by an in-vehicle communication system (so-called “CAN communication” L 123 , for example), an auxiliary brake switch position detection device ( 5 S) for detecting a switch position of an auxiliary brake switch ( 5 ) and an accelerator pedal pressing amount measurement device (accelerator opening sensor  4 S) for measuring an amount of pressing of an accelerator pedal ( 4 ) (as a voltage of the accelerator pedal) are provided, the vehicle electronic control unit ( 10 ) is provided with a storage device ( 14 ) storing characteristics of the amount of pressing the accelerator pedal and the auxiliary braking force, 
     the vehicle electronic control unit has a function for determining the auxiliary braking force corresponding to the amount of pressing the accelerator pedal ( 4 ) in correspondence with the characteristics stored in the storage device ( 14 ), if the accelerator pedal ( 4 ) is pressed when an auxiliary braking device ( 3 ) is operated by the auxiliary brake switch ( 5 ) and 
     a function for transmitting the determined auxiliary braking force to the other electronic control units ( 20 ,  30 ) are provided. 
     In the present invention, the characteristics of the amount of pressing the accelerator pedal ( 4 ) and the auxiliary braking force stored in the storage device ( 14 ) are preferably different at each switch position of the auxiliary brake switch ( 5 ). 
     In the present invention, the auxiliary braking device ( 100 ) of a vehicle is preferably at least one of an exhaust brake of the engine and a retarder ( 3 ) for obtaining the braking force by a generator set on a propeller shaft. 
     Advantageous Effects of Invention 
     According to the present invention provided with the above described constructions, if the accelerator pedal ( 4 ) is pressed when the auxiliary braking device ( 100 ) is operating, the auxiliary braking force corresponding to the amount of pressing the accelerator pedal ( 4 ) is determined and it is transmitted to the electronic control units ( 20 ,  30 ) other than the vehicle electronic control unit ( 10 ). 
     Thus, even if the accelerator pedal ( 4 ) is pressed when the auxiliary braking device ( 100 ) is operating, the state does not immediately change to an acceleration state as in the prior art, but the auxiliary braking force corresponding to the accelerator pedal ( 4 ) works. 
     Thus, rapid acceleration or occurrence of a shock in the vehicle caused by that as in the prior art can be prevented. 
     Moreover, if the amount of pressing the accelerator pedal ( 4 ) is decreased while the auxiliary braking device is operating, the auxiliary braking force increases in accordance with that. There is no need as in the prior art to return the accelerator pedal until the accelerator pedal opening becomes zero in order to operate the auxiliary braking force. 
     As a result, it is no longer necessary to repeat pressing of the accelerator pedal ( 4 ) and returning it until the opening becomes zero. Thus, as compared with the prior art, acceleration/decoration of the vehicle become gentle and frequencies of acceleration/deceleration decrease and fuel consumption is improved. 
     Moreover, since acceleration/deceleration become gentle, repetition of shift-up/shift-down in a vehicle having an automatic transmission is prevented. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a construction of an auxiliary braking device of a vehicle according to an embodiment of the present invention. 
         FIG. 2  is a block diagram illustrating a construction of a vehicle electronic control unit according to an embodiment and relevance between the vehicle electronic control unit and sensors and retarders. 
         FIG. 3  is a characteristic diagram illustrating a relationship among an accelerator pedal voltage, a braking force and a driving force in order to acquire an auxiliary braking force. 
         FIG. 4  is a flowchart illustrating control for determining the auxiliary braking force according to the embodiment. 
         FIG. 5  is a characteristic diagram illustrating a relationship between an accelerator pedal voltage and an accelerator opening as well as a required braking force ratio in a prior art. 
         FIG. 6  is a characteristic diagram illustrating a relationship between an engine speed and the auxiliary braking force in the prior art. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described below by referring to the attached drawings. 
       FIG. 1  shows a construction of an auxiliary braking device of a vehicle generally indicated by reference numeral  100 . 
     In  FIG. 1 , in a vehicle having an engine  1 , a transmission  2  and a retarder  3 , the auxiliary braking device  100  of a vehicle is provided with an accelerator opening sensor  4 S, an auxiliary brake switch position detection device  5 S, a vehicle control unit  10 , an engine controller  20 , and a retarder controller  30 . 
     It is possible to select an exhaust brake other than the retarder  3  for the auxiliary braking device main body. 
     The accelerator opening sensor  4 S is attached to be engaged with an accelerator pedal  4  and transmits a voltage signal of intensity according to accelerator opening to the control unit (hereinafter referred to as a “control unit”)  10  by a line L 4 . 
     The auxiliary brake switch position detection device (hereinafter referred to as an “auxiliary brake position sensor”)  5 S is constructed to be engaged with an auxiliary brake lever  5  whose intensity of an auxiliary braking force (degree of effect) can be switched in four stages so as to detect a position of the four stages. 
     The auxiliary brake position sensor  5 S transmits information of the current position to the control unit  10  by a line L 5 . 
     The control unit  10 , the engine controller  20 , and the retarder controller  30  are connected to each other by an in-vehicle communication system (so-called “CAN communication”, for example) L 123 . 
     The engine controller  20  is connected to a fuel injection device, not shown, by a line L 20  and is constructed to control a fuel injection amount of the fuel injection device in accordance with a control signal transmitted by the control unit  10 . 
     The retarder controller  30  is connected to the retarder  3  by a line L 30  and is constructed to adjust a braking force (power generation amount) of the retarder  3  in accordance with the control signal transmitted by the control unit  10 . 
       FIG. 2  shows constructions of the control unit  10  and a relationship among the control unit  10 , the accelerator opening sensor  4 S, the auxiliary brake position sensor  5 S, the engine controller  20 , and the retarder controller  30 . 
     In  FIG. 2 , the control unit  10  is provided with an auxiliary braking force determination block  12  and a database  14  as storage means. 
     The auxiliary braking force determination block  12  and the database  14  are connected by a line L 124  and a line L 142 . It is constructed such that a position of the auxiliary brake is sent from the auxiliary braking force determination block  12  to the database  14  by the line L 124 , while characteristics relating to the auxiliary braking force corresponding to the position are sent back from the database  14  to the auxiliary braking force determination block  12  by the line L 142 . 
     The auxiliary braking force determination block  12  determines the auxiliary braking force from the accelerator opening information from the accelerator opening sensor  4 S obtained by the line L 4 , auxiliary braking force information from the auxiliary brake position sensor  5 S obtained by the line L 5 , and characteristic diagrams (See  FIG. 3 ) stored in the database  14 . 
     Then, the auxiliary braking force determination block  12  sends a control signal for generating the auxiliary braking force determined in the auxiliary braking force determination block  12  to the retarder controller  30 . Alternatively, the control signal is sent to the engine controller  20  in order to keep the driving force in a proper value at that time. 
     Here,  FIG. 5  shows four positions (switch positions 0, 1, 2, and 3) provided in the auxiliary brake position sensor and a ratio of a required auxiliary braking force at each position (lower region in  FIG. 5 ) over the characteristic diagram illustrating a relationship between the accelerator pedal opening and the accelerator pedal voltage in the prior art (upper region in  FIG. 5 ) in an overlapping manner. 
     As shown in  FIG. 5 , the prior art is constructed such that the auxiliary braking force is not generated when the accelerator pedal is pressed. 
     Moreover, the braking force at the four switch positions (0 to 4) are substantially constant in each of the line diagrams regardless of the engine speed as shown in a line diagram (P 0 , P 1  to P 3 ) in  FIG. 6 . 
     On the other hand, in the auxiliary braking device  100  in this embodiment, the braking force of the auxiliary braking is determined by the characteristic diagram in  FIG. 3 . 
     In  FIG. 3 , intensity of the accelerator pedal voltage (in proportion to the accelerator opening) is marked on the lateral axis, while a ratio of the required auxiliary braking force or the driving force is marked on the vertical axis. 
     If the position of the auxiliary braking lever is 0 (during normal running), as shown in a line diagram C 0 , the auxiliary braking is non-operating. Therefore, the driving force (acceleration side) increases in proportion to the amount of pressing the accelerator pedal (accelerator pedal voltage). 
     Thus, according to the embodiment shown in the drawings, it is possible to set the braking force with respect to the engine speed so that it is located in an intermediate region of the line diagrams P 0  and P 1  to P 3  in  FIG. 6 . 
     The example in  FIG. 3  is constructed such that the braking force increases in the same proportion as the position number (1, 2, and 3) of the auxiliary braking lever  5  increases. 
     In  FIG. 3 , it is known that, if the position 2 (the line diagram C 2 ) is selected, the driving force effecting acceleration cannot be obtained until the accelerator pedal  4  is pressed from the start of pressing until V 2  (P 2  point) is reached in voltage value conversion of the accelerator pedal. 
     Moreover, if the position 1 (the line diagram C) is selected, the vehicle changes from deceleration to acceleration with a not-so-large accelerator pedal pressing amount (V 1  in voltage value conversion of the accelerator pedal). 
     In  FIG. 3 , the line diagram C 3  is a braking force characteristic when the position 3 is selected. 
     Subsequently, a method of determining the auxiliary braking force will be described on the basis of a flowchart in  FIG. 4  and also by referring to  FIG. 1 . 
     At Step S 1  in  FIG. 4 , the control unit  10  stands by until the auxiliary brake starts operation (loop at Step S 1 ). 
     If the auxiliary brake starts to operate (YES at Step S 1 ), the routine proceeds to Step S 2 , and the control unit  10  selects a characteristic corresponding to an auxiliary brake position (position of the auxiliary brake lever  5 ) from the characteristic diagram in  FIG. 3  on the basis of the information from the auxiliary brake position sensor  5 S. 
     At the subsequent Step S 3 , the control unit  10  obtains an accelerator pedal opening signal on the basis of the information from the accelerator opening sensor  4 S. Then, the appropriate auxiliary braking force is determined at Step S 4  by referring to the data in the database  14 , that is, from the characteristic diagram in  FIG. 3 . Then, information of the determined auxiliary braking force and a fuel injection amount relating to that is sent to the retarder controller  30  and the engine controller  20  (Step S 5 ). 
     According to the embodiment shown in the drawings, if the accelerator pedal  4  is pressed while the retarder  3  is operating, the auxiliary braking force corresponding to the amount of pressing the accelerator pedal  4  is determined and sent to the retarder controller  30  and the engine controller. 
     Thus, even if the accelerator pedal  4  is pressed while the retarder  3  is operating, the state does not immediately change to an acceleration state as in the prior art, but the auxiliary braking force corresponding to the accelerator pedal  4  works. 
     Thus, rapid acceleration or occurrence of a shock in the vehicle caused by that as in the prior art can be prevented. 
     Moreover, if the amount of pressing the accelerator pedal  4  is decreased while the retarder  3  is operating, the auxiliary braking force increases in correspondence with that. It is not necessary to return the accelerator pedal until the accelerator pedal opening becomes zero in order to operate the auxiliary braking force as in the prior art. 
     As a result, it is no longer necessary to repeat pressing of the accelerator pedal  4  and returning it until the opening becomes zero. Thus, as compared with the prior art, acceleration/deceleration of the vehicle become gentle and frequencies of acceleration/deceleration decrease and fuel consumption can be improved. 
     Moreover, since acceleration/deceleration become gentle, repetition of shift-up/shift-down in a vehicle having an automatic transmission is prevented. 
     The embodiment shown in the drawings is only exemplification and the description is not intended to limit the technical scope of the present invention. 
     In the embodiment shown by the drawings, in the characteristic diagram in  FIG. 3 , the line diagram C 3  is constituted as non-linear. That is, even if the accelerator pedal is pressed, the auxiliary braking force is not largely decreased until the pressing amount reaches a predetermined amount but decrease of the auxiliary braking force is expedited at that amount or more. 
     The line diagram C 3  may have a linear characteristic as in the line diagrams C 1  and C 2 . On the contrary, all the line diagrams C 1  to C 3  may have non-linear characteristics. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  engine 
               2  transmission 
               3  retarder 
               4 S accelerator opening sensor 
               5 S auxiliary brake switch position detection device/auxiliary brake position sensor 
               10  vehicle ECU/control unit 
               12  auxiliary braking force determination block 
               14  storage device/database 
               20  engine ECU/engine controller 
               30  retarder ECU/retarder controller