Patent Publication Number: US-2023136679-A1

Title: Crawler-type work machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National stage application of International Application No. PCT/JP2021/022729, filed on Jun. 15, 2021. This U.S. National stage application claims priority under 35 U.S.C. § 119(a) to Japanese Patent Application No. 2020-129004, filed in Japan on Jul. 30, 2020, the entire contents of which are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a crawler-type work machine. 
     BACKGROUND ART 
     In a crawler-type work machine (e.g., a bulldozer), power from an engine is transmitted through a transmission to left and right drive wheels so that left and right crawler belts are driven by the left and right drive wheels. In this type of crawler-type work machine, turning to the left and right is executed by controlling the hydraulic pressure of left and right steering clutches and left and right steering brakes provided in correspondence to the left and right drive wheels. 
     Japanese Patent Laid-open No. 2017-71357 proposes a method for supplying, to a steering brake, a portion of the lubricating oil supplied from a hydraulic pump to a steering clutch, in order to use the lubricating oil efficiently. 
     SUMMARY 
     While it is assumed that a planetary gear mechanism may be provided between an input shaft and an output shaft in order to make the steering clutch more compact, Japanese Patent Laid-open No. 2017-71357 does not examine how to efficiently use the lubricating oil when providing a planetary gear mechanism. 
     An object of the present disclosure is to provide a crawler-type work machine that is able to use lubricating oil efficiently. 
     A crawler-type work machine according to one aspect of the present disclosure has a planetary gear mechanism, a steering clutch, a steering brake, a hydraulic pump, a first oil channel, a second oil channel, and a third oil channel. The planetary gear mechanism is disposed between an input shaft and an output shaft. The steering clutch is configured to switch between transmitting and blocking the rotation from the input shaft to the output shaft by the planetary gear mechanism. The steering brake is configured to brake the rotation of the output shaft. The hydraulic pump is configured to discharge a lubricating oil. The first oil channel is configured to guide a portion of the lubricating oil discharged by the hydraulic pump to the steering brake. The second oil channel is configured to guide a portion of the lubricating oil discharged by the hydraulic pump to the planetary gear mechanism. The third oil channel is configured to guide at least a portion of the lubricating oil that has passed through the planetary gear mechanism to the steering brake. At least a portion of the planetary gear mechanism is disposed further inside than the steering brake in a radial direction perpendicular to a center axis of the input shaft. 
     According to the crawler-type work machine as in the present disclosure, the lubricating oil can be used efficiently. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of a bulldozer that is an example of the crawler-type work machine. 
         FIG.  2    is a cross-sectional configuration diagram of a power transmission system of the bulldozer. 
         FIG.  3    is an outline system configuration diagram of the power transmission system of the bulldozer. 
         FIG.  4    is a cross-sectional view illustrating a configuration in the vicinity of a lubricating oil channel. 
         FIG.  5    is a schematic view for explaining the flow of the lubricating oil. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     (Configuration of Bulldozer  1 ) 
       FIG.  1    is a perspective view of a bulldozer  1  that is an example of the crawler-type work machine.  FIG.  2    is a cross-sectional configuration diagram of the power transmission system of the bulldozer  1 .  FIG.  3    is an outline system configuration diagram of the power transmission system of the bulldozer  1 . 
     The bulldozer  1  is equipped with: left and right travel devices  4 L,  4 R that respectively have left and right sprockets  2 L,  2 R and left and right crawler belts  3 L,  3 R; a blade  5  provided at a vehicle front part; and a ripper device  6  provided at a vehicle rear part. 
     The bulldozer  1  is able to do work such as pushing earth with the blade  5 , and work such as crushing and excavating with the ripper device  6 . 
     The bulldozer  1  includes an engine  10 , a power transmission device  20 , left and right planetary gear mechanisms  30 L,  30 R, left and right steering clutches  40 L,  40 R, left and right steering brakes  50 L,  50 R, left and right output shafts  60 L,  60 R, left and right final drive gears  70 L,  70 R, and a lubricating oil supply unit  80 . 
     The power transmission device  20  transmits power from the engine  10  to the left and right planetary gear mechanisms  30 L,  30 R. The power transmission device  20  includes a power take-off device  21 , a torque converter  22 , a transmission  23 , a pinion  24 , a bevel gear  25 , and an input shaft  26 . 
     The power transmission device  21  transmits power from the engine  10  to the torque converter  22  and the lubricating oil supply unit  80 . The torque converter  22  transmits the power of the engine  10  transmitted by the power take-off device  21  to the transmission  23  by means of a fluid. The transmission  23  changes the speed of the rotation motion transmitted from the torque converter  22 . The transmission  23  is able to switch between forward travel and reverse travel. The transmission  23  is coupled to the pinion  24 . Power from the transmission  23  is transmitted through the pinion  24  and the bevel gear  25  to the input shaft  26 . 
     The left and right planetary gear mechanisms  30 L,  30 R are disposed between the input shaft  26  and the left and right output shafts  60 L,  60 R. The left and right planetary gear mechanisms  30 L,  30 R respectively have left and right ring gears  31 L,  31 R, left and right planetary gears  32 L,  32 R, left and right sun gears  33 L,  33 R, and left and right carriers  34 L,  34 R. 
     The left and right ring gears  31 L,  31 R are coupled to the input shaft  26 . The left and right planetary gears  32 L,  32 R are respectively disposed inside the left and right ring gears  31 L,  31 R in a radial direction perpendicular to the center axis of the input shaft  26 . The left and right planetary gears  32 L,  32 R are respectively disposed between the left and right ring gears  31 L,  31 R and the left and right sun gears  33 L,  33 R. The left and right planetary gears  32 L,  32 R respectively mesh with the left and right ring gears  31 L,  31 R and the left and right sun gears  33 L,  33 R. The left and right sun gears  33 L,  33 R are rotatably attached to the input shaft  26 . The left and right sun gears  33 L,  33 R are respectively disposed inside the left and right planetary gears  32 L,  32 R in the radial direction. The left and right sun gears  33 L,  33 R are respectively coupled to the left and right steering clutches  40 L,  40 R. The left and right carriers  34 L,  34 R are respectively coupled to the left and right planetary gears  32 L,  32 R and the left and right output shafts  60 L,  60 R. 
     The left and right steering clutches  40 L,  40 R are wet multiplate clutches that can be respectively engaged or disengaged with the left and right sun gears  33 L,  33 R. The left and right steering clutches  40 L,  40 R switch between respectively transmitting and blocking the rotational force from the input shaft  26  to the left and right output shafts  60 L,  60 R by means of the respective left and right planetary gear mechanisms  30 L,  30 R. 
     Specifically, when the left steering clutch  40 L is coupled and the left sun gear  33 L is directly coupled to a first clutch gear  91 , the first clutch gear  91  cannot rotate (see below) and the left sun gear  33 L also cannot rotate. As a result, the rotation of the input shaft  26  is transmitted through the left ring gear  31 L, the left planetary gear  32 L, and the left carrier  34 L to the left output shaft  60 L. When the left steering clutch  40 L is disengaged and the left sun gear  33 L enters a freely rotating state, the rotation from the input shaft  26  to the left output shaft  60 L is blocked. Similarly, the transmission or blocking of the rotation from the input shaft  26  to the right output shaft  60 R is switched in accordance with the engagement or disengagement of the right steering clutch  40 R. 
     As illustrated in  FIG.  3   , the first clutch gear  91  is attached to the left steering clutch  40 L and the first clutch gear  91  is coupled to an idler gear  93  and a pinion gear  94 . In addition, a second clutch gear  92  is attached to the right steering clutch  40 R and the second clutch gear  92  is coupled to the idler gear  93  and the pinion gear  94  via a first transfer gear  95 , an auxiliary shaft  96 , and a second transfer gear  97 . A pinion shaft  94   a  is coupled to the pinion gear  94  and is fixed by a fixing member  98  in an unrotatable manner. Therefore, the rotational force from the left and right steering clutches  40 L,  40 R to the left and right sun gears  33 L,  33 R is not applied. 
     The fixing member  98  is detachably fixed to an unillustrated housing. When the fixing member  98  is removed from the housing, the fixing member  98  can be removed from the pinion gear  94 . As a result, the fixing of the pinion gear  94  by the fixing member  98  can be released. 
     When the fixing of the pinion gear  94  by the fixing member  98  is released, a turning motor (not illustrated) may be coupled to the pinion shaft  94   a.  In this case, when the left and right steering clutches  40 L,  40 R are engaged and the rotational force of the turning motor is transmitted to the left and right sun gears  33 L,  33 R through the left and right steering clutches  40 L,  40 R, the left and right sun gears  33 L,  33 R rotate in the opposite directions at the same rotation speed. Consequently, a rotation speed difference is generated in the left and right output shafts  60 L,  60 R and the bulldozer  1  is able to turn gently to the left or right. 
     The left and right steering brakes  50 L,  50 R respectively brake the rotation of the left and right output shafts  60 L,  60 R. The left and right steering brakes  50 L,  50 R are wet multiplate clutches that can be respectively engaged or disengaged with the left and right output shafts  60 L,  60 R. 
     When the left steering brake  50 L is engaged, braking is applied to the rotation of the left output shaft  60 L. As a result, the rotation of the left final drive gear  70 L coupled to the left sprocket  2 L is reduced. When the right steering brake  50 R is engaged, braking is applied to the rotation of the right output shaft  60 R. As a result, the rotation of the right final drive gear  70 R coupled to the right sprocket  2 R is reduced. 
     The lubricating oil supply unit  80  has a hydraulic pump  81 , a lubricating oil channel  82 , and a lubricating oil tank  83 . 
     The hydraulic pump  81  is driven by power from the engine  10  transmitted from the power take-off device  21 . The hydraulic pump  81  discharges the lubricating oil from the lubricating oil tank  83  to the lubricating oil channel  82 . The hydraulic pump  81  is a fixed displacement pump in the present embodiment. 
     The lubricating oil channel  82  includes a first oil supply channel  100 , a second oil supply channel  110 , left and right first oil channels  101 L,  101 R, left and right second oil channels  102 L,  102 R, left and right third oil channels  103 L,  103 R, left and right fourth oil channels  104 L,  104 R, left and right fifth oil channels  105 L,  105 R, and left and right oil discharge channels  106 L,  106 R. 
     The first oil supply channel  100  is continuous with the hydraulic pump  81  to the second oil supply channel  110  and the left and right first oil channels  101 L,  101 R. The first oil supply channel  100  supplies the lubricating oil discharged from the hydraulic pump  81  to the second oil supply channel  110  and the left and right first oil channels  101 L,  101 R. 
     The left and right first oil channels  101 L,  101 R guide a portion of the lubricating oil discharged by the hydraulic pump  81  to the left and right steering brakes  50 L,  50 R. 
     The second oil supply channel  110  is continuous with the first oil supply channel  100  and the inside of the input shaft  26 . The second oil supply channel  110  guides a portion of the lubricating oil discharged by the hydraulic pump  81  to the left and right second oil channels  102 L,  102 R and the left and right fourth oil channels  104 L,  104 R. 
     The left and right second oil channels  102 L,  102 R respectively guide a portion of the lubricating oil discharged by the hydraulic pump  81  to the left and right planetary gear mechanisms  30 L,  30 R. The left and right third oil channels  103 L,  103 R respectively guide at least a portion of the lubricating oil that has passed through the left and right planetary gear mechanisms  30 L,  30 R to the left and right steering brakes  50 L,  50 R. In the present embodiment, the left and right third oil channels  103 L,  103 R respectively guide all of the lubricating oil that has passed through the left and right planetary gear mechanisms  30 L,  30 R to the left and right steering brakes  50 L,  50 R. 
     The left and right fourth oil channels  104 L,  104 R respectively guide a portion of the lubricating oil discharged by the hydraulic pump  81  to the left and right steering clutches  40 L,  40 R. The left and right fifth oil channels  105 L,  105 R respectively guide at least a portion of the lubricating oil that has passed through the left and right steering brakes  40 L,  40 R to the left and right steering brakes  50 L,  50 R. Specifically, the left and right fifth oil channels  105 L,  105 R guide all of the lubricating oil that has passed through the left and right steering brakes  40 L,  40 R to the left and right steering brakes  50 L,  50 R via the left and right planetary gear mechanisms  30 L,  30 R and the left and right third oil channels  103 L,  103 R. 
     In this way, all of the lubricating oil guided to the left and right planetary gear mechanisms  30 L,  30 R and to the left and right steering clutches  40 L,  40 R is guided respectively to the left and right steering brakes  50 L,  50 R via the left and right third oil channels  103 L,  103 R, and the left and right fifth oil channels  105 L,  105 R in the present embodiment. 
     The left and right oil discharge channels  106 L,  106 R guide the lubricating oil that has passed through the left and right steering brakes  50 L,  50 R to the lubricating oil tank  83 . 
     (Configuration in the Vicinity of the Lubricating Oil Channel  82 ) 
       FIG.  4    is a cross-sectional view illustrating a configuration in the vicinity of the lubricating oil channel  82 . A cross-section perpendicular to the center axis of the input shaft  26  is depicted in  FIG.  4   . The configuration in the vicinity of the lubricating oil channel  82  is basically right-left symmetrical and the configuration on the right side will be explained below. 
     The right steering clutch  40 R has a rotating member  41 , a clutch housing  42 , a plurality of clutch disks  43 , a plurality of clutch plates  44 , and a clutch piston  45 . 
     The rotating member  41  is supported by the input shaft  26  and rotates around the center axis of the input shaft  26 . The clutch housing  42  is disposed so as to allow relative rotation with respect to the rotating member  41 . The clutch housing  42  encircles the outside of the clutch disks  43  and the clutch plates  44 . The clutch disks  43  are supported by the rotating member  41 . The clutch plates  44  are supported by the clutch housing  42 . The clutch disks  43  and the clutch plates  44  are disposed alternately in the axial direction parallel to the center axis of the input shaft  26 . The clutch piston  45  brings the clutch discs  43  and the clutch plates  44  into pressure contact when hydraulic fluid is supplied. As a result, the right steering clutch  40 R enters an engaged state. 
     The right steering brake  50 R has a rotating member  51 , a brake housing  52 , a plurality of fixing plates  53 , a plurality of brake disks  54 , and a brake piston  55 . 
     The rotating member  51  is fixed to the right output shaft  60 R and rotates around the center axis of the right output shaft  60 R. The brake housing  52  is able to rotate relatively with respect to the rotating member  51 . In the present embodiment, the brake housing  52  is fixed and the brake housing  52  itself does not rotate. The brake housing  52  encircles the outside of the fixing plates  53  and the brake disks  54 . The fixing plates  53  are attached to the brake housing  52 . The fixing plates  53  may move slightly in the axial direction with respect to the brake housing  52 . The brake disks  54  are supported by the rotating member  51 . The brake disks  54  may move slightly in the axial direction with respect to the rotating member  51 . 
     The fixing plates  53  and the brake disks  54  are disposed alternately in the axial direction. The fixing plates  53  and the brake disks  54  are pressed together by an unillustrated spring (e.g., a disk spring or a coil spring). The brake piston  55  causes the fixing plates  53  and the brake disks  54  to separate from each other when hydraulic fluid is supplied. Consequently, the right steering brake  50 R enters a non-braking state. 
     At least a portion of the right planetary gear mechanism  30 R is disposed further inside than the right steering brake  50 R in the radial direction. Specifically, the right ring gear  31 R is disposed further to the inside than the brake disks  54  in the radial direction. Moreover, the right planetary gear  32 R and the right sun gear  33 R disposed on the inside of the right ring gear  31 R are also disposed further to the inside than the brake disks  54  in the radial direction. Furthermore, a portion of the right carrier  34 R coupled to the right planetary gear  32 R and the right output shaft  60 R is also disposed further to the inside than the brake disks  54  in the radial direction. 
     At least a portion of the right steering clutch  40 R is disposed further inside than the right steering brake  50 R in the radial direction. Specifically, the clutch disks  43  and the clutch plates  44  are disposed further to the inside than the brake disks  54  in the radial direction. 
     The phrase “at least a portion of the member X is disposed further to the inside than the member Y in the radial direction” in the present description signifies that the minimum distance between the member X and the center axis is less than the minimum distance between the member Y and the center axis when viewing from the axial direction parallel to the center axis of the input shaft  26 . In this case, the position of the member X in the axial direction and the position of the member Y in the axial direction may partially or completely overlap each other or may not overlap each other. 
     In the present embodiment, while the right steering brake  50 R, the right planetary gear mechanism  30 R, and the right steering clutch  40 R are disposed in said order from the right side, the disposition order in the axial direction may be changed as appropriate. 
     Next, the flow of the lubricating oil will be explained.  FIG.  5    is a schematic view for explaining the flow of the lubricating oil. 
     The lubricating oil discharged from the hydraulic pump  81  is distributed to the right first oil channel  101 R, the right second oil channel  102 R, and the right fourth oil channel  104 R via the first oil supply channel  100  and the second oil supply channel  110 . The distribution ratio to the oil channels may be adjusted as appropriate by changing the opening radius of each oil channel. 
     The lubricating oil distributed to the right fourth oil channel  104 R is guided from the right fifth oil channel  105 R to the right planetary gear mechanism  30 R by centrifugal force after the right steering clutch  40 R has been lubricated. 
     After the right planetary gear mechanism  30 R has been lubricated, the lubricating oil distributed to the right second oil channel  102 R is guided from the right third oil channel  103 R to the right steering brake  50 R by centrifugal force along with the lubricating oil guided from the right fifth oil channel  105 R to the right planetary gear mechanism  30 R. 
     After the right steering brake  50 R has been lubricated with the lubricating oil guided from the right third oil channel  103 R to the right steering brake  50 R, the lubricating oil distributed to the right first oil channel  101 R is guided from the right oil discharge passage  106 R to the lubricating oil tank  83  by centrifugal force. 
     The bulldozer  1  includes a right first oil channel  101 R, a right second oil channel  102 R, and a right third oil channel  103 R. The right first oil channel  101 R guides a portion of the lubricating oil discharged by the hydraulic pump  81  to the right steering brake  50 R. The right second oil channel  102 R guides a portion of the lubricating oil discharged by the hydraulic pump  81  to the right planetary gear mechanism  30 R. The third oil channel  103 R guides at least a portion of the lubricating oil that has passed through the right planetary gear mechanism  30 R to the right steering brake  50 R. At least a portion of the planetary gear mechanism  30 R is disposed further inside than the right steering brake  50 R in the radial direction perpendicular to the center axis of the input shaft  26 . 
     Therefore, because the lubricating oil can be guided from the right planetary gear mechanism  30 R to the right steering brake  50 R with centrifugal force via the third oil channel  103 R, the lubricating oil used for lubricating the right planetary gear mechanism  30 R can also be used for lubricating the right steering brake  50 R. As a result, the lubricating oil supplied from the hydraulic pump  81  can be used efficiently and the capacity of the hydraulic pump  81  can be reduced. This result can be obtained in the same way for the left steering brake  50 L. 
     The bulldozer  1  includes the right fourth oil channel  104 R and the right fifth oil channel  105 R. The right fourth oil channel  104 R guides a portion of the lubricating oil discharged by the hydraulic pump  81  to the right steering clutch  40 R. The fifth oil channel  105 R guides at least a portion of the lubricating oil that has passed through the right steering clutch  40 R to the right steering brake  50 R. At least a portion of the right steering clutch  40 R is disposed further inside than the right steering brake  50 R in the radial direction. 
     Therefore, because the lubricating oil can be guided from the right steering clutch  40 R to the right steering brake  50 R by centrifugal force via the fifth oil channel  105 R, the lubricating oil used for lubricating the right steering clutch  40 R can also be used for lubricating the right steering brake  50 R. As a result, the lubricating oil supplied from the hydraulic pump  81  can be used efficiently and the capacity of the hydraulic pump  81  can be reduced. This result can be obtained in the same way for the left steering brake  50 L. 
     The present disclosure is not limited to the above embodiment and various changes and modifications may be made without departing from the spirit of the disclosure. 
     In the present embodiment, although the left and right third oil channels  103 L,  103 R respectively guide all of the lubricating oil that has passed through the left and right planetary gear mechanisms  30 L,  30 R to the left and right steering brakes  50 L,  50 R, the present disclosure is not limited thereto. The left and right third oil channels  103 L,  103 R may also respectively guide only a portion of the lubricating oil that has passed through the left and right planetary gear mechanisms  30 L,  30 R to the left and right steering brakes  50 L,  50 R. In this case, the remaining portion of the lubricating oil that has passed through the left and right planetary gear mechanisms  30 L,  30 R may be returned directly to the lubricating oil tank  83 . 
     In the present embodiment, although the left and right fifth oil channels  105 L,  105 R respectively guide all of the lubricating oil that has passed through the left and right steering clutches  40 L,  40 R to the left and right steering brakes  50 L,  50 R, the present disclosure is not limited thereto. The left and right fifth oil channels  105 L,  105 R may also respectively guide only a portion of the lubricating oil that has passed through the left and right steering clutches  40 L,  40 R to the left and right steering brakes  50 L,  50 R. In this case, the remaining portion of the lubricating oil that has passed through the left and right steering clutches  40 L,  40 R may be returned directly to the lubricating oil tank  83 . 
     In the present embodiment, although the left and right fifth oil channels  105 L,  105 R are respectively connected from the left and right steering clutches  40 L,  40 R to the left and right planetary gear mechanisms  30 L,  30 R, the present disclosure is not limited thereto. For example, the left and right fifth oil channels  105 L,  105 R may also be respectively connected directly from the left and right steering clutches  40 L,  40 R to the left and right steering brakes  50 L,  50 R. Alternatively, the left and right fifth oil channels  105 L,  105 R may also be respectively connected directly from the left and right steering clutches  40 L,  40 R to the lubricating oil tank  83 .