JP5107583B2 - Travel device for work vehicle - Google Patents

Description

  The present invention relates to a traveling speed change device for a work vehicle such as a tractor used for agricultural work or a wheel loader used for civil engineering work, and more specifically, includes a continuously variable transmission and a sub-transmission mechanism for multi-speed transmission. The present invention relates to a traveling device for a work vehicle.

  Conventionally, in general, in a working vehicle such as a tractor or a wheel loader described above, when power is transmitted to traveling parts such as left and right traveling wheels or traveling crawlers, a transmission case is transmitted from an engine mounted on a traveling machine body in the working vehicle via a main clutch. The power is transmitted to the left and right traveling parts via the transmission mechanism of the transmission case.

In this case, in a conventional traveling device for a work vehicle, a clutch housing and a transmission case are disposed in the traveling machine body, a main clutch is built in the clutch housing, and the engine is connected to the hydraulic continuously variable transmission via the main clutch. The power is transmitted from the hydraulic continuously variable transmission to the traveling unit via the gear type sub-transmission mechanism (see, for example, Patent Document 1).
JP 2003-226165 A

  In the prior art, when the main shift operation tool (main shift operation lever) is operated to control the main shift output of the hydraulic continuously variable transmission, the vehicle speed is reduced from zero at all the shift stages of the gear type sub-transmission mechanism. Since shifting to the maximum speed, the minimum vehicle speed at the high speed side drive output (for example, second speed) of the auxiliary transmission mechanism may be slower than the maximum vehicle speed at the low speed side drive output (for example, first speed) of the auxiliary transmission mechanism. There are problems such as overlapping vehicle speeds at a plurality of shift stages of the gear-type sub-transmission mechanism.

  As a result, even if the sub-transmission operation tool (sub-transmission operation lever) is operated and the gear position of the sub-transmission mechanism is changed to the high speed side, the gear position of the sub-transmission mechanism is changed depending on the operation of the main transmission operation tool. The vehicle speed may be slower than before. On the other hand, even if the gear position of the sub-transmission mechanism is changed to the low speed side, the vehicle speed may become faster than before the gear position of the sub-transmission mechanism is changed depending on the operation of the main transmission operating tool. Therefore, there is a problem that a smooth acceleration operation or deceleration operation cannot be easily executed by an operator who is unfamiliar with driving.

  In addition, when the gear position of the subtransmission mechanism is changed to the high speed side (for example, the third speed, the maximum speed of the subtransmission), the main transmission operating tool is operated to the low speed side (low speed with a small swash plate angle of the hydraulic pump). The hydraulic continuously variable transmission may be stalled, and the power from the engine may not be transmitted from the hydraulic continuously variable transmission to the gear-type sub-transmission mechanism. Therefore, by switching the sub-transmission mechanism to the high speed side and operating the main transmission operation tool to the low speed side when traveling on the road traveling at high speed, the main transmission operation tool is moved from the engine before moving to the neutral position. There is a problem that the power is not transmitted to the traveling part, and the traveling machine body stops or reversely travels on a slope.

  An object of the present invention is to enable a smooth speed increasing operation or a speed reducing operation to be easily executed by a main transmission operation tool and a sub transmission operation tool, and to stop a traveling machine body by a low speed operation of the main transmission operation tool, It is intended to provide a traveling device for a work vehicle that can be easily prevented from going backward.

In order to achieve the above object, a traveling device for a work vehicle according to a first aspect of the present invention includes a continuously variable transmission that shifts power from an engine mounted on a traveling machine body, and a gear ratio of the continuously variable transmission is changed. A work vehicle comprising: a main transmission operation tool that performs a transmission, a sub-transmission mechanism for multi-stage transmission that transmits a shift drive output from the continuously variable transmission, and a sub-transmission operation tool that changes a gear ratio of the sub transmission mechanism. In the traveling apparatus, a main transmission sensor that detects an operation position of the main transmission operation tool, a transmission output portion rotation sensor that detects a transmission drive output rotation speed of the continuously variable transmission, and an operation position of the auxiliary transmission operation tool A sub-transmission sensor for detecting the main transmission operation tool, the main transmission output from the continuously variable transmission is made zero by the neutral operation of the main transmission operation tool, and the non-transmission sensor is determined by the minimum vehicle speed operation of the main transmission operation tool. Minimum main gear shift from step transmission The speed is increased as the speed change operation of the auxiliary transmission operation tool is performed on the high speed side, and the maximum vehicle speed operation of the main transmission operation tool is performed when the speed change operation of the sub transmission operation tool is on the low speed side. The speed change operation of the sub-shift operation tool is at a higher speed side than the maximum main shift output from the continuously variable transmission determined by In this configuration, the minimum main shift output from the step transmission is increased .

According to the first aspect of the present invention, a continuously variable transmission that shifts power from an engine mounted on a traveling machine body, a main transmission operating tool that changes a gear ratio of the continuously variable transmission, and the continuously variable transmission. In a traveling device for a work vehicle, comprising: a sub-transmission mechanism for multi-stage transmission that transmits a shift drive output from a machine; and a sub-transmission operation tool that changes a gear ratio of the sub-transmission mechanism. comprising a main shift sensor for detecting an operation position, the speed change output section rotation sensor for detecting the speed drive output speed of the continuously variable transmission, and a sub-transmission sensor for detecting an operation position of the subtransmission operation member, wherein By the neutral operation of the main transmission operation tool, the main transmission output from the continuously variable transmission is made zero vehicle speed, and the minimum main transmission output from the continuously variable transmission determined by the minimum vehicle speed operation of the main transmission operation tool is The speed change operation of the auxiliary speed change operation tool is The speed on the speed side is faster, and the maximum main speed from the continuously variable transmission is determined by the maximum vehicle speed operation on the main speed change operation tool when the speed change operation of the auxiliary speed change operation is on the low speed side. The minimum main transmission output from the continuously variable transmission determined by the minimum vehicle speed operation of the main transmission operation tool is made faster when the shift stage operation of the auxiliary transmission operation tool is on the higher speed side than the transmission output. since those constituting, in a plurality of shift speeds of the subtransmission mechanism, thereby preventing the vehicle speed overlap. As a result, when the shift speed of the auxiliary transmission mechanism is changed to the high speed side, the vehicle speed selected by the main transmission operating tool does not become slower than before the shift speed of the auxiliary transmission mechanism is changed. On the other hand, when the shift speed of the auxiliary transmission mechanism is changed to the low speed side, the vehicle speed selected by the main transmission operating tool does not become faster than before the shift speed of the auxiliary transmission mechanism is changed. Therefore, as in the case of a conventional gear mission (a structure in which both the main transmission mechanism and the sub-transmission mechanism are configured by a plurality of gears) that does not use a hydraulic pump for shifting, a hydraulic motor, or the like, A smooth speed-up operation or speed-down operation can be easily executed by the speed change operation tool.

  In addition, when driving on the road moving at a high speed, the power from the engine is not transmitted to the traveling unit before the main transmission operation tool shifts to the neutral position by operating the main transmission operation tool to the low speed side. Can be prevented. Therefore, while traveling on the road, it is easy for the traveling machine to stop or reversely travel on a slope even though the engine is operating and the main transmission operating tool is operated to the transmission position. Can be prevented.

In addition, in the state where the speed change operation of the auxiliary speed changer is on the low speed side, the auxiliary speed change is greater than the maximum main speed output from the continuously variable transmission determined by the maximum vehicle speed operation of the main speed changer. The minimum main shift output from the continuously variable transmission determined by the minimum vehicle speed operation of the main transmission operation tool is increased in a state where the operation stage of the operation gear is on the high speed side. Therefore, it is possible to prevent the vehicle speeds from overlapping at a plurality of shift speeds of the auxiliary transmission mechanism. Even if the gear position of the auxiliary transmission mechanism is changed to the high speed side (low speed side), the vehicle speed selected by the main transmission operation tool becomes slower (higher) than before the gear position of the auxiliary transmission mechanism is changed. Can be prevented. A smooth speed-up operation or a speed-down operation can be easily executed by the main transmission operation tool and the auxiliary transmission operation tool.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, drawings when an embodiment of the present invention is applied to a farm tractor as a work vehicle will be described. 1 is a side view of a tractor, FIG. 2 is a plan view of the same, FIG. 3 is a diagram of a traveling drive system, FIG. 4 is a hydraulic circuit diagram, FIG. 5 is a control circuit diagram for traveling shifting, and FIG. FIG. 7 is a flowchart of gear ratio adaptive control.

  As shown in FIGS. 1 and 2, the tractor 1 supports the traveling machine body 2 with a pair of left and right rear wheels 4 as well as a pair of left and right front wheels 3, and an engine 5 mounted on the front portion of the traveling machine body 2. The two rear wheels 4 and the two front wheels 3 are driven to drive forward and backward. The traveling machine body 2 appropriately shifts the rotation of the engine 5 having an engine frame 8 having a front bumper 6 and a front axle case 7, a clutch housing 10 having a main clutch for interrupting power output from the engine 5, and the engine 5. A transmission case 11 for transmitting to the rear wheels 4 and the front wheels 3, a transmission front case 12 for connecting the transmission case 11 to the clutch housing 10, and projecting outward from the outer surface of the clutch housing 10. It comprises a pair of left and right step frames 13 that are detachably mounted.

  A water-cooling radiator 9 is disposed in front of the engine 5. The rear end side of the engine frame 8 is connected to the left and right outer surfaces of the engine 5. The front side of the clutch housing 10 is connected to the rear side of the engine 5. The front side of the mission case 11 is connected to the rear side of the clutch housing 10 via a mission front case 12.

  The engine 5 is covered with a hood 14. A steering column 15 is erected on the upper surface of the clutch housing 10. A steering handle 16 that is steered by moving the front wheels 3 to the left and right is disposed on the upper surface side of the steering column 15. A control seat 17 is disposed on the upper surface of the mission case 11. Flat floor boards 18 are respectively provided on the upper surfaces of the pair of left and right step frames 13. Both front wheels 3 are attached to the engine frame 8 via a front axle case 7. Both rear wheels 4 are attached to the mission case 11 via a rear axle case 11 a that is detachably mounted so as to protrude outward from the outer surface of the mission case 11. The upper surface side of both rear wheels 4 is covered with left and right rear fenders 4a.

  On the upper surface of the mission case 11, a hydraulic working machine lifting mechanism 20 for lifting and lowering a working machine (not shown) such as a tiller connected to the rear part of the traveling machine body 2 is detachably attached. Yes. Furthermore, a PTO shaft 21 for transmitting a driving force to the working machine is provided on the rear side surface of the transmission case 11 so as to protrude rearward. The working machine is connected to the rear portion of the mission case 11 via a three-point link mechanism 24 including a pair of left and right lower links 22 and one top link 23. When the left and right lift arms 20a of the work implement lifting mechanism 20 are connected to the left and right lower links 22 via the lift rod 20b, and the work implement lift mechanism 20 is operated, the work implement moves up and down. .

  As shown in FIG. 3, a hydrostatic continuously variable transmission (HST) 25 described later is disposed on the front side surface of the mission front case 12. The hydrostatic continuously variable transmission 25 is installed in the rear part of the clutch housing 10. A main drive shaft 26 protrudes rearward from the engine 5 through the main clutch 19, and the rotation of the engine 5 is transmitted to the continuously variable transmission 25 through the main drive shaft 26, and then output from the continuously variable transmission 25. Is appropriately shifted by the auxiliary transmission gear mechanism 59 and transmitted to the both rear wheels 4 and both front wheels 3. On the other hand, the rotation of the engine 5 from the main drive shaft 26 is transmitted to the PTO shaft 21 through a PTO transmission gear mechanism via a PTO transmission shaft and a PTO clutch (not shown).

  Next, with reference to FIGS. 1 to 3, the structure of the control unit operated by the operator of the control seat 17 will be described. A clutch pedal 31 is disposed on the left side of the control column 15 protruding upward from the floor plate 18 in front of the control seat 17. When the operator depresses the clutch pedal 31, the main clutch 19 in the clutch housing 10 for transmitting power from the engine 5 to the continuously variable transmission 25 is disconnected.

  On the other hand, right and left brake pedals 33 for operating the left and right rear wheel 4 braking brake mechanisms 32 are disposed to the right of the steering column 15. The brake mechanism 32 is actuated by stepping on the brake pedal 33, and the left and right rear wheels 4 are braked. A reverser lever 27 that switches the moving direction to forward or backward is disposed below the steering handle 16 and to the left of the steering column 15. An accelerator lever 28 for changing the rotational speed of the engine 5 is disposed below the steering handle 16 and to the right of the steering column 15.

  As shown in FIG. 2 and FIG. 3, a main transmission lever 36 for shifting the main transmission hydraulic continuously variable transmission 25 is disposed to the right of the control seat 17. A shift control unit (trunnion shaft) of the main transmission hydraulic continuously variable transmission 25 is connected to a main transmission hydraulic cylinder 37 as a main transmission actuator that is operated by the operation of the main transmission lever 36. The continuously variable transmission 25 performs a shifting operation. Further, a work implement elevating lever 40 and a tilling depth adjusting lever 41 are disposed to the right of the control seat 17. By operating the work implement lifting lever 40 or the tilling depth adjusting lever 41, the work implement lifting mechanism 20 is operated.

As shown in FIG. 2 and FIG. 3, a sub transmission lever 42 for switching the sub transmission gear mechanism 59 is disposed on the left side of the control seat 17. By operating the sub-shift lever 42, the sub-transmission gear mechanism 59 of the mechanical transmission structure is divided into three stages: a low speed (first speed output) position, a medium speed (second speed output) position, and a high speed (third speed output) position. Each transmission gear (not shown) is selectively switched. Between the low-speed position and the medium-speed position, and between the medium-speed position and the high-speed position, neutral positions where the sub-shift output is zero are formed. A PTO speed change lever 43 for switching a PTO speed change mechanism (not shown) for transmitting rotational force to the PTO shaft 21 is disposed on the left side of the control seat 17. By operating the PTO speed change lever 43, the PTO speed change output from the PTO speed change mechanism is divided into three stages of low speed (1st speed output), medium speed (2nd speed output), and high speed (3rd speed output), with the neutral state sandwiched, It will be shifted.

  With the above configuration, the continuously variable transmission output from the continuously variable transmission 25 is transmitted to the auxiliary transmission gear mechanism 59 via the main transmission output shaft 60. The auxiliary transmission output from the auxiliary transmission gear mechanism 59 is shifted from the auxiliary transmission output shaft 61 after being shifted in three stages of low speed (first speed output), medium speed (second speed output), and high speed (third speed output). It is transmitted to the left and right rear wheels 4 via the gear mechanism 62 and the like.

  FIG. 4 shows a hydraulic circuit 70 of the tractor 1 according to this embodiment, which includes a working machine hydraulic pump 74 and a charging hydraulic pump 75 that are operated by the rotational force of the engine 5. The working machine hydraulic pump 74 is connected to a lifting hydraulic switching valve 77 for supplying hydraulic oil to a single-acting lifting hydraulic cylinder 76 in the working machine lifting mechanism 20. Accordingly, the operator operates the work implement elevating lever 40 to switch the elevating hydraulic switching valve 77 to operate the elevating hydraulic cylinder 76 and rotate the lift arm 20a, so that the work implement is connected via the lower link 22. Will be raised or lowered.

  As shown in FIG. 4, the continuously variable transmission 25 includes a transmission hydraulic pump 63 and a transmission hydraulic motor 64 that is operated by the hydraulic pump 63. The above-described variable displacement type shifting hydraulic pump 63 of the hydraulic continuously variable transmission 25 and the constant displacement type shifting hydraulic motor 64 operated by the high pressure hydraulic oil discharged from the hydraulic pump 63 are a closed loop oil. The suction side and the discharge side are connected via a path 65. The closed loop oil passage 65 is supplied with hydraulic oil from a charging hydraulic pump 75. The charge hydraulic pump 75 is connected to the main transmission hydraulic cylinder 37 via the main transmission hydraulic switching valve 78.

  Therefore, when the main transmission hydraulic switching valve 78 is switched by operating the main transmission lever 36 and the main transmission hydraulic cylinder 37 is operated, in other words, the transmission hydraulic pump 63 driven via the transmission input shaft 65. When the angle of the swash plate 63a is adjusted by the main transmission hydraulic cylinder 37, the rotational speed of the main transmission output shaft 60 driven via the transmission hydraulic motor 64 is changed. As shown in FIG. 4, the hydraulic circuit 70 described above includes a relief valve, a flow rate adjustment valve, a check valve, an oil cooler, an oil filter, and the like.

  Next, traveling control (shift control) of the work vehicle (traveling vehicle) of the present embodiment will be described. FIG. 5 is a functional block diagram of the travel control means, and includes a speed change controller 80 such as a microcomputer. The shift controller 80 includes a ROM that stores a control program and a RAM that stores various data.

  Further, as shown in FIG. 5, the speed change controller 80 includes various sensors and switches of the input system, that is, an engine rotation sensor 81 for detecting the rotation speed of the engine 5 and the rotation speed (tractor) Vehicle speed sensor 82 for detecting the movement speed of 1 (vehicle speed), a potentiometer-type main transmission sensor 83 for detecting the operation position (rotation amount) of the main transmission lever 36, and the operation position (rotation amount) of the sub transmission lever 42. A potentiometer-type sub transmission sensor 84 to be detected, a minimum vehicle speed FLP1Vmin at the lowest speed operation position of the main transmission lever 36 in response to a low speed (first speed) operation position of the sub transmission lever 42, and a low speed setting for setting a gear ratio pattern. , The minimum vehicle speed FLP2Vmin at the lowest speed operation position of the main speed change lever 36 in response to the medium speed (second speed) operation position of the auxiliary speed change lever 42, and the change. A medium speed setter 86 for setting the ratio pattern, a minimum vehicle speed FLP3Vmin at the lowest speed operation position of the main speed change lever 36 in response to a high speed (third speed) operation position of the auxiliary speed change lever 42, and a high speed for setting the speed ratio pattern A setting device 86 is connected. Each setter 85, 86, 87 is formed of a variable resistor so that the minimum vehicle speeds FLP1Vmin, FLP2Vmin, FLP3Vmin at the lowest speed operation position of the main transmission lever 36 can be changed steplessly. .

  Further, as shown in FIG. 5, the speed change controller 80 includes various output solenoid valves and indicators such as a monitor, that is, an electromagnetic solenoid of a main hydraulic pressure switching valve 78 of a hydraulic proportional solenoid valve type. It is connected. Based on the outputs of the main transmission sensor 83, the sub transmission sensor 84, the low speed setting device 85, the medium speed setting device 86, and the high speed setting device 86, the main transmission hydraulic pressure switching valve 78 is operated. Then, the main transmission hydraulic cylinder 37 is operated, the angle of the swash plate 63a of the hydraulic pump 63 of the main transmission hydraulic continuously variable transmission 25 is controlled, and the main transmission ratio of the main transmission hydraulic continuously variable transmission 25 is changed. It is configured to do. It is to be noted that the operator can operate the sub-shift lever 42 according to work conditions, etc., and the minimum vehicle speed and the gear ratio pattern can be set for each gear position of the sub-transmission mechanism 59. The setting device 86 and the high-speed setting device 86 are provided. However, a single setting device may be used as each setting device 85, 86, and 87. Each setting device 85, 86, 87 may be formed in the structure of the equation.

  Next, adaptive control of the main gear ratio of the main transmission hydraulic continuously variable transmission 25 will be described. Here, the main transmission ratio refers to the ratio of the rotational speed of the main transmission output shaft 60 of the hydraulic continuously variable transmission 25 to the engine 5 rotational speed. In addition, the control to make the speed close to or coincide with the target vehicle speed in response to the operation position of the main transmission lever 36 and the operation position of the sub transmission lever 42 is referred to as transmission ratio adaptive control. In other words, hydraulic switching for main transmission for controlling the gear ratio of the hydraulic continuously variable transmission 29 so that the vehicle speed in response to the operation position of the main transmission lever 36 and the operation position of the sub transmission lever 42 becomes the target vehicle speed. The valve 78 is controlled. Therefore, the speed ratio pattern of the speed ratio of the main speed change output shaft 60 in the hydraulic continuously variable transmission 29 with respect to the operation position of the main speed change lever 36 and the operation position of the sub speed change lever 42 is stored in the pattern controller 80. The data is stored in a RAM (a readable / writable memory as needed).

  This speed ratio pattern is a pattern in which the vehicle speed increases in proportion to an increase in the operation amount of the main speed change lever 36, and the proportional function is a linear function. The proportional function of the gear ratio pattern may be a function of a quadratic curve. The pattern storage means stores a plurality of speed ratio patterns in a function table format or a map format (see a gear ratio diagram as shown in FIG. 6). In the embodiment of FIG. 6, there are three types of gear ratio patterns according to the operation of the sub-shift lever 42 in three stages of a low speed (first speed output) position, a medium speed (second speed output) position, and a high speed (third speed output) position. (Speed ratio line) is prepared and stored in advance in the pattern storage means. When the operator operates the sub transmission lever 42, one pattern corresponding to the sub transmission operation position is selected (instructed) from the three types of gear ratio patterns. In other words, the auxiliary transmission lever 42 is for changing the change rate of the main transmission ratio corresponding to the operation amount of the main transmission lever 36.

  In the embodiment shown in FIG. 6, the horizontal transmission axis P is the main transmission ratio P (the amount of operation of the main transmission lever 36), and the vertical axis (see the left vertical axis) is the vehicle speed V (the number of rotations of the auxiliary transmission output shaft 61). A diagram of the transmission ratio pattern is shown. In FIG. 6, the sub-shift low-speed (first speed) output FLP1, the sub-shift medium speed (second speed) output FLP2, and the sub-shift high-speed (third speed) output FLP3 are shown in order from the lower line. The angle of the swash plate 63a of the hydraulic pump 63 of the main transmission hydraulic continuously variable transmission 25 is a rotation range from the neutral where the rotation speed of the main transmission output shaft 60 becomes substantially zero to the maximum inclination angle (maximum vehicle speed), that is, A shift range (SLP, 1 = SLPmin to 10 = SLPmax range) of the main transmission hydraulic continuously variable transmission 25 from the lowest vehicle speed to the highest vehicle speed is set. Of the main shift range (1 = SLPmin to 10 = SLPmax) of the main transmission hydraulic continuously variable transmission 25, the vehicle speed V corresponding to the minimum vehicle speed (1 = SLPmin) is the minimum vehicle speed FLP1Vmin of the low speed output FLP1 of the auxiliary shift. Alternatively, the main transmission hydraulic continuously variable transmission in the main transmission range of the main transmission hydraulic continuously variable transmission 25 so as to coincide with either the minimum vehicle speed FLP2Vmin of the medium speed output FLP2 or the minimum vehicle speed FLP3Vmin of the high speed output FLP3. The minimum number of rotations of the 25 hydraulic motors 64 is maintained.

  In other words, in a state where the auxiliary transmission lever 42 is operated to the low speed (first speed output) position, the main transmission lever 36 is operated to the lowest vehicle speed (1 = SLPmin), so that the vehicle speed V becomes the lowest rotation of the hydraulic motor 64. The angle of the swash plate 63a of the hydraulic pump 63 is controlled so that the minimum vehicle speed FLP1Vmin necessary for maintaining the number is reached. In other words, the subtransmission mechanism is higher than the maximum vehicle speeds FLP1max and FLP2max of the subtransmission output when the main transmission lever 36 is operated to the maximum vehicle speed 10 = SLPmax position on the low speed stage FLP1, FLP2 side where the transmission ratio of the auxiliary transmission mechanism 59 is high. The minimum vehicle speeds FLP1min and FLP2min of the sub-shift output when the main transmission lever 36 is operated to the minimum vehicle speed 1 = SLPmin position on the high speed stage FLP2 and FLP3 side where the gear ratio of 59 is low are configured to increase. As a result, when the main transmission lever 36 is operated at an extremely low speed (minimum vehicle speed 1 = SLPmin), the main transmission hydraulic continuously variable transmission 25 is stalled (although the angle of the swash plate 63a of the hydraulic pump 63 is larger than neutral). Thus, it is possible to prevent the tractor 1 from stopping by maintaining the rotation speed of the hydraulic motor 64 at zero.

  For example, in the past, a state in which the main transmission hydraulic continuously variable transmission 25 is stalled due to an extremely low speed (minimum vehicle speed 1 = SLPmin) operation of the main transmission lever 36 in farm work or the like is due to a misunderstanding by the operator. If it is mistaken that the tractor 1 is stopped due to the neutral operation, when the main transmission hydraulic continuously variable transmission 25 is released from the stalled state due to a decrease in the load of the engine 5 or the like, Although there is a problem that the tractor 1 moves at an extremely low vehicle speed, in this embodiment, the main transmission lever 36 can be operated at an extremely low speed by preventing the main transmission hydraulic continuously variable transmission 25 from stalling.

  On the other hand, when the auxiliary transmission lever 42 is operated to the medium speed (second speed output) position or when the auxiliary transmission lever 42 is operated to the high speed (third speed output) position, the main transmission lever 36 is at the minimum vehicle speed (1). = SLPmin), the angle of the swash plate 63a of the hydraulic pump 63 is controlled so that the vehicle speed V becomes the minimum vehicle speeds FLP2Vmin and FLP3Vmin necessary for maintaining the minimum rotational speed of the hydraulic motor 64. As a result, the vehicle speed becomes zero by the neutral operation of the main transmission lever 36 regardless of the position of the sub transmission lever 42, but in this embodiment, the maximum vehicle speed FLP1Vmax at the sub transmission low speed (first speed output). Further, the minimum vehicle speed FLP2Vmin for the sub-shift medium speed (second-speed output) is set larger, and the minimum vehicle speed FLP3Vmin for the sub-shift high speed (third-speed output) is set larger than the maximum vehicle speed FLP2Vmax of the medium sub-speed (second-speed output). Thus, it is possible to prevent the vehicle speed V from being overlapped by the speed change operation of the main speed change lever 36 at each speed of the sub speed change lever 42.

  That is, the vehicle speed V is linearly increased or decreased by the shift operation of the main shift lever 36 in a large shift range between the sub shift low speed and the sub shift high speed regardless of the shift operation of the sub shift lever 42. Therefore, the operator can smoothly change the speed of the main shift lever 36 from the sub-shift low speed stage to the sub-shift high speed stage while easily predicting the change in the moving speed, and the vehicle speed V can be adjusted to the farm work conditions. It can be easily changed and the work efficiency of farm work etc. can be improved.

  Similarly to the case where the sub transmission lever 42 is operated to the low speed (first speed output) position, the sub transmission lever 42 is operated to the medium speed (second speed output) position or the high speed (third speed output) position. However, it is possible to prevent the main transmission hydraulic continuously variable transmission 25 from stalling and stopping the tractor 1 by operating the main transmission lever 36 at an extremely low speed (minimum vehicle speed 1 = SLPmin). Therefore, even if the transmission structure has the continuously variable transmission 25, the driving force can be smoothly shifted as in the conventional gear transmission structure having the main transmission gear instead of the continuously variable transmission 25.

  Next, the main gear ratio adaptive control mode will be described with reference to the flowchart of the gear ratio control (FIG. 7). As described above, the main transmission hydraulic pressure switching valve 78 is actuated in proportion to the operation amount of the main transmission lever 36, and the main transmission hydraulic cylinder 37 is driven by the hydraulic oil from now on so that the hydraulic continuously variable as the main transmission mechanism. The pressure oil discharge amount of the hydraulic pump 25 of the transmission 25 is controlled. In this case, automatic control is performed to maintain the minimum vehicle speeds FLP1Vmin, FLP2Vmin, FLP3Vmin set by the setting devices 85, 86, 87. More specifically, the operation amount of the main transmission lever 36 and the operation position of the auxiliary transmission lever 42 are determined. Self-monitoring and automatically maintaining the minimum vehicle speeds FLP1Vmin, FLP2Vmin, FLP3Vmin set by the setting devices 85, 86, 87 according to changes in the operation amount of the main transmission lever 36 and the operation position of the auxiliary transmission lever 42 It is something to control. Thus, the rotational speed of the main transmission output shaft 36 can be changed and adjusted steplessly.

  Therefore, in the gear ratio adaptive control, the engine is started (S1), then the operation position of the sub-shift lever 42 is read (S2), and a predetermined gear shift stored in the RAM (a readable / writable memory as needed) of the gear shift controller 80 is read. The ratio patterns FLP1, FLP2, FLP3 are read out.

  Next, when the operator operates the main transmission lever 36 to move the tractor 1 forward (reverse), the operation amount of the main transmission lever 36 is read from the main transmission sensor 83 into the transmission controller 80 (S3). Based on the read numerical value, the calculation unit of the speed change controller 80 determines the target vehicle speed (target speed ratio value) corresponding to the operation amount of the main speed change lever 36 on the selected speed ratio patterns FLP1, FLP2, and FLP3. Calculate (S4).

  On the other hand, the shift controller 80 reads the engine 5 rotation speed from the engine rotation sensor 81 at every constant time interval (sampling time interval) during traveling, and the vehicle speed sensor 82 detects the auxiliary transmission output shaft 61 rotation speed. (S5). The current vehicle speed V is calculated from the ratio between the engine speed (denominator) at the sampling time (current) and the sub-shift output shaft 61 speed (numerator), and the current vehicle speed V is the target on the speed ratio patterns FLP1, FLP2, and FLP3. It is determined whether or not the vehicle speed is substantially equal (S6).

  When the current vehicle speed V (current gear ratio value) is separated from the target vehicle speed (target gear ratio value) by a predetermined percentage larger or smaller (S6: no), the gear shift controller 80 corrects the voltage applied to the hydraulic pressure switching valve 78. As a result, the angle of the swash plate 63a of the hydraulic pump 63 is changed and adjusted, and the amount of hydraulic oil discharged to the hydraulic motor 64 is controlled to increase or decrease the rotational speed of the main transmission output shaft 60. (S7). If the current vehicle speed V is substantially equal to the target vehicle speed (when the current vehicle speed V is within ± predetermined% with respect to the target vehicle speed) (S6: yes), the rotational speed of the main transmission output shaft 60 is maintained (S8).

  Accordingly, the state in which the auxiliary transmission lever 42 is operated to the low speed (first speed output) position, the state in which the auxiliary transmission lever 42 is operated to the middle speed (second speed output) position, or the auxiliary transmission lever 42 is operated to the high speed (third speed). In the state of being operated to the output) position, the main speed change lever 36 is operated to the minimum vehicle speed (1 = SLPmin), so that the vehicle speed V is the minimum vehicle speed FLP1Vmin, FLP2Vmin required to maintain the minimum rotation speed of the hydraulic motor 64. , FLP3Vmin, the swash plate 63a angle of the hydraulic pump 63 is controlled. As a result, the vehicle speed becomes zero by the neutral operation of the main transmission lever 36 regardless of the shift position of the auxiliary transmission lever 42, but the minimum vehicle speeds FLP1Vmin, FLP2Vmin, FLP3Vmin are maintained by the transmission operation of the main transmission lever 36. Therefore, it is possible to prevent the vehicle speed V from being overlapped by the shifting operation of the main shifting lever 36 at each shift stage of the sub shifting lever 42 and to operate the main shifting lever 36 at the very low speed (minimum vehicle speed 1 = SLPmin). Stall of the transmission hydraulic continuously variable transmission 25 (occurrence of an overload operation state in which the hydraulic motor 64 is stopped even though the angle of the swash plate 63a of the hydraulic pump 63 is larger than the neutral position) can be prevented.

  As is clear from the above description and FIGS. 3, 5, and 6, the continuously variable transmission 25 that changes the power from the engine 5 mounted on the traveling machine body 2 and the transmission ratio of the continuously variable transmission 25 are changed. A main transmission lever 36 as a main transmission operation tool, a multi-speed transmission sub-transmission mechanism 59 that transmits a shift drive output from the continuously variable transmission 25, and a sub-transmission operation tool that changes the gear ratio of the sub-transmission mechanism 59. In the traveling device of the work vehicle including the auxiliary transmission lever 42 as a main transmission sensor 83, a main transmission sensor 83 that detects the operation position of the main transmission lever 36, and a transmission output that detects the transmission drive output speed of the continuously variable transmission 25. A continuously variable transmission that includes a vehicle speed sensor 82 as a part rotation sensor and a sub-transmission sensor 84 that detects an operation position of the sub-transmission lever 42 and is determined by operation of the main transmission lever 36 by operation of the sub-transmission lever 42. 2 From main speed change output FLP1Vmin from, FLP2Vmin, since those configured as FLP3Vmin is changed, the plurality of shift speeds FLP1, FLP2, FLP3 of the subtransmission mechanism 59, that the vehicle speed FLP1V overlap can be prevented. As a result, when the shift speeds FLP1 and FLP2 of the auxiliary transmission mechanism 59 are changed to the high speed side, the vehicle speed selected by the main transmission lever 36 is slower than before the shift speeds FLP1 and FLP2 of the auxiliary transmission mechanism 59 are changed. Never become. On the other hand, when the shift speeds FLP2 and FLP3 of the auxiliary transmission mechanism 59 are changed to the low speed side, the vehicle speed selected by the main transmission lever 36 becomes faster than before the shift speeds FLP2 and FLP3 of the auxiliary transmission mechanism 59 are changed. There is nothing. Therefore, in the same manner as the conventional gear mission (a structure in which both the main transmission mechanism and the sub-transmission mechanism are configured by a plurality of gears) that does not use the hydraulic pump 63 for transmission, the hydraulic motor 64, and the like, A smooth speed-up operation or speed-down operation can be easily executed by the sub-shift lever 42.

  Further, when the main speed change lever 36 is operated to the low speed side during road travel that moves at a high speed, the power from the engine 5 is used as the rear wheel 4 as the travel portion before the main speed change lever 36 shifts to the neutral position. Can be prevented from being transmitted to. Therefore, while traveling on the road, it is easy for the traveling machine body 2 to stop or reversely travel on a slope even though the engine 5 is operating and the main speed change lever 36 is operated to the speed change position. Can be prevented.

  As is apparent from the above description and FIGS. 3 and 6, the speed ratio of the auxiliary transmission mechanism 59 is higher than the maximum vehicle speed FLP1Vmax and FLP2Vmax when the transmission ratio of the auxiliary transmission mechanism 59 is on the low speed stage FLP1 and FLP2 side. Since the minimum vehicle speeds FLP2Vmin and FLP3Vmin on the FLP2 and FLP3 side are increased, the vehicle speed V can be prevented from overlapping in the plurality of shift speeds FLP1, FLP2 and FLP3 of the auxiliary transmission mechanism 59. Even if the gear position of the subtransmission mechanism 59 is changed to the high speed side FLP2, FLP3 (low speed side FLP1, FLP2), the vehicle speed selected by the main transmission lever 36 is slower than before the gear stage of the subtransmission mechanism is changed. (Fast) can be prevented. A smooth speed increase operation or speed reduction operation can be easily executed by the main speed change lever 36 and the sub speed change lever 42.

  As apparent from the above description and FIGS. 5 and 6, the speed change controller 80 serving as a pattern storage means for storing a plurality of speed ratio patterns of the continuously variable transmission 25 and the speed ratio pattern of the continuously variable transmission 25 are shown. A low-speed setting device 85, a medium-speed setting device 86, and a high-speed setting device 87 are provided as pattern setting devices to be selected, and the setting devices 85, 86, 87 are used according to the operation amount of the main transmission lever 36. Since the output rotational speed of the continuously variable transmission 25 is controlled based on the selected gear ratio pattern, after the operator sets the gear ratio pattern with the setting devices 85, 86, 87, the main speed change lever By simply operating 36, when the actual gear ratio value deviates from the target value due to environmental changes or fluctuations in the work vehicle's running load, it can be automatically controlled so as to automatically approach the target gear ratio value. .

It is a side view of the agricultural tractor which concerns on the Example of this invention. It is the same top view. It is the traveling drive system diagram. It is a hydraulic circuit diagram. FIG. 6 is a control circuit diagram for traveling speed change. It is a diagram showing the relationship between the main transmission output and the vehicle speed. It is a flowchart of gear ratio adaptive control.

2 traveling machine body 5 engine 25 continuously variable transmission 36 main transmission lever (main transmission operating tool)
42 Sub-shift lever (sub-shift control tool)
80 Speed change controller (pattern storage means)
82 Vehicle speed sensor (shift output sensor rotation sensor)
83 Main transmission sensor 84 Sub transmission sensor 85 Low-speed setting device (pattern setting device)
86 Medium speed setting device (Pattern setting device)
87 High-speed setting device (pattern setting device)

Claims (1)

A continuously variable transmission that shifts power from an engine mounted on a traveling machine body, a main transmission operating tool that changes a transmission ratio of the continuously variable transmission, and a multi-stage that transmits a shift drive output from the continuously variable transmission. In a traveling apparatus for a work vehicle, comprising: a sub-transmission mechanism for shifting; and a sub-transmission operation tool that changes a gear ratio of the sub-transmission mechanism.
A main transmission sensor that detects an operation position of the main transmission operation tool, a transmission output portion rotation sensor that detects a transmission drive output rotational speed of the continuously variable transmission, and a sub transmission that detects an operation position of the auxiliary transmission operation tool. With a sensor,
By the neutral operation of the main transmission operating tool, the main transmission output from the continuously variable transmission is made zero vehicle speed,
The minimum main transmission output from the continuously variable transmission determined by the minimum vehicle speed operation of the main transmission operation tool is increased as the speed operation of the auxiliary transmission operation tool is on the high speed side,
Further, the sub-shift operation is more effective than the maximum main shift output from the continuously variable transmission, which is determined by the maximum vehicle speed operation of the main shift operation tool, when the shift speed operation of the sub-shift operation tool is on the low speed stage side. In a state where the gear shift operation of the tool is on the high speed side, the minimum main shift output from the continuously variable transmission determined by the minimum vehicle speed operation of the main shift operation tool is configured to be faster.
A traveling device for a work vehicle.

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