JP2013053637A - Working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a working vehicle for steplessly shifting power transmitted to a traveling device by an HST, in which the HST can stably operate when an engine rotates both at high speed and low speed.SOLUTION: The working vehicle includes the HST 14 constituted of: an HST pump 16 which is driven by power from the engine 4; an HST motor 17 which outputs power on a side of the traveling device 1. The working vehicle steplessly shifts the power transmitted to the traveling device 1 by the HST 14. The transmission mechanism 19 is provided for shifting the power from the engine 4 at high or low speed to transmit it to the HST pump 16.

Description

  The present invention relates to a work vehicle that continuously changes the power transmitted to a traveling device by HST.

  Patent Document 1 that includes an HST composed of an HST pump driven by power from an engine and an HST motor that outputs power to the traveling device side, and continuously shifts the power transmitted to the traveling device by the HST The work vehicle shown in FIG.

Japanese Patent Laid-Open No. 11-50868

  In the work vehicle described in the above document, the engine speed is controlled in order to prevent the high-speed rotation power exceeding the set value from being input to the HST pump, but the power output from the engine is directly applied to the HST pump. Therefore, it is difficult to work by rotating the engine at a high speed, and when the engine is operated at a low speed, the rotational speed of the power input to the HTS pump is too low. Thus, it may be difficult to operate the HST stably.

  According to the present invention, in a work vehicle that continuously changes the power transmitted to the traveling device by the HST, the HST is stably operated both when the engine is rotated at a high speed and when the engine is rotated at a low speed. It is an object of the present invention to provide a work vehicle that can be used.

  In order to solve the above-mentioned problems, firstly, an HST pump 16 that is driven by power from the engine 4 and an HST motor 17 that outputs power to the traveling device 1 side is provided. A work vehicle that continuously changes the power transmitted to the device 1 and is characterized by the provision of a speed change mechanism 19 that shifts the power from the engine 4 to a high and low level and transmits it to the HST pump 16.

  Secondly, a control unit 33 for controlling the shift switching of the transmission mechanism 19 is provided, and the control unit 33 is configured so that the rotational speed of the power input to the HST pump 16 falls within a predetermined setting range. Regardless of the shift command to the mechanism 19, the shift switching of the transmission mechanism 19 is controlled in accordance with the engine speed.

  Thirdly, a control unit 33 that controls the engine speed and the shift switching of the transmission mechanism 19 is provided, and the control unit 33 has a rotational speed of power input to the HST pump 16 within a predetermined setting range. The engine speed is controlled so as to be within the range.

  According to the above configuration, when it is desired to work at a low engine speed, by switching the speed change mechanism to the high speed side, the power having a speed sufficient to stably operate the HST is While it is easy to input to the pump, if you want to work at a high engine speed, switching the speed change mechanism to the low speed side causes the HST to input a high speed rotational power that is greater than the set value. Can be prevented. For this reason, the HST can be stably operated and the traveling device can be efficiently driven both during the operation of rotating the engine at a low speed and during the operation of rotating the engine at a high speed.

1 is a perspective view of an agricultural tractor to which the present invention is applied. It is a power transmission system diagram of this tractor. It is a perspective view which shows the principal part structure in a cabin. It is a perspective view which shows the structure which linked the steering handle and the HST pump by the action | operation mechanism. It is a block diagram of a control apparatus. It is a processing flow figure of the main control part in the case of performing shift change control of a transmission mechanism. It is a processing flow figure of the main control part in the case of performing an engine speed control part. (A), (B) is the side view and top view of a boarding / alighting step. (A), (B) is the side view and top view which show the structure of the other example of a boarding / alighting step.

  FIG. 1 is a perspective view of an agricultural tractor to which the present invention is applied. A tractor, which is a type of work vehicle, has a cabin 3 standing on the rear half of a chassis frame 2 supported by a pair of left and right crawler type traveling devices (traveling devices) 1, 1. A traveling machine body 7 is configured by opening and closing a bonnet 6 that covers the upper side and the periphery of the engine 4 (see FIG. 2) in the front half, and a working machine (not shown) is connected to the traveling machine body 7.

  The tractor performs various operations on the farm field by lowering the work implement and driving the left and right crawler type traveling devices 1 and 1 to travel forward. As a working machine, there exists a connection rotary tillage apparatus connected to the back of the traveling body 7 so that raising / lowering is possible via a raising / lowering link (not shown), a cutting blade, etc., for example.

  The crawler type traveling devices 1, 1 are configured by providing driving wheels 9 and idler wheels 11 at both ends of the traveling frame 8 in the front-rear direction, and by crawling around the driving wheels 9 and idler wheels 11. Has been. Then, the crawler type traveling device 1 is driven to travel by rotating the driving wheel 9.

  FIG. 2 is a power transmission system diagram of the tractor. The power output from the engine 4 is directly output to the transmission shaft 13. The power of the transmission shaft 13 is transmitted toward the PTO shaft that outputs power to the work machine, and is transmitted toward the HST 14 that shifts the power to the left and right crawler type traveling devices 1, 1.

  The HST 14 is a hydraulic stepless transmission, and the HST 14 is provided for each of the left and right crawler type traveling devices 1. Each HST 14 has a hydraulic HST pump 16 and an HST motor 17, and when the HST motor 17 is driven by hydraulic fluid fed by the HST pump 16 to output power, the discharge of the variable displacement HST pump 16 is performed. The amount of power output from the HST motor 17 is steplessly changed by changing the amount by turning the operating arm 18 (see FIG. 4) that rotates integrally with the trunnion shaft.

  While the power of the transmission shaft 13 is transmitted to the HST pump 16 through the speed change mechanism 19, the power output from the HST motor 17 is directly transmitted to the drive wheels 9 of the crawler type traveling device 1. Then, the crawler type traveling device 1 is driven to travel.

  The speed change mechanism 19 provided on the transmission upstream side of both the HSTs 14 and 14 includes the transmission shaft 13, a small-diameter low-speed input gear 21 </ b> L and a large-diameter high-speed input gear 21 </ b> H that rotate integrally with the transmission shaft 13, and both the HST pumps 14. , 14, a pump drive shaft 22, a large-diameter low-speed output gear 23L that is rotatably supported by the pump drive shaft 22 and always meshes with the low-speed input gear 21L, and is rotatably supported by the pump drive shaft 22. A small-diameter high-speed output gear 23H that always meshes with the high-speed input gear 21H and a hydraulic transmission clutch 24 that intermittently transmits the power of the low-speed output gear 23L or the high-speed output gear 23H to the pump drive shaft 22 are provided.

  The transmission mechanism 19 is in a low speed state in which the power of the transmission shaft 13 is transmitted to the pump drive shaft 22 at a low speed via the low speed input gear 21L and the low speed output gear 23L, and via the high speed input gear 21H and the high speed output gear 23H. The transmission clutch 13 is configured to switch between a high speed state in which the power of the transmission shaft 13 is transmitted to the pump drive shaft 22 at a high speed and a neutral state in which the power of the transmission shaft 13 is not transmitted to the pump drive shaft 22. That is, the speed change mechanism 19 is configured to shift the power from the engine 4 to a high and low level and input the power to the HST pump 16.

  FIG. 3 is a perspective view showing a main part configuration in the cabin, and FIG. 4 is a perspective view showing a configuration in which the steering handle and the HST pump are linked by an operating mechanism. The cabin 3 includes a seat 26 on which an operator is seated, a travel speed change lever 27 that is located on the side of the seat 26 and swings back and forth, and a grip 27 a that is formed at the upper end of the travel speed change lever 27. A shift switch 28 that is a push-type shift operation tool installed on the side and a steering handle 29 that is a steering operation tool disposed in front of the seat 26 are provided, and a travel shift lever 27 and a steering handle 29 are provided. The operating arms 18 and 18 are mechanically linked by an operating mechanism 31.

  When the travel shift lever 27 is swung from the neutral position to the left and right sides, it can be swung forward from the neutral position, while when it is swung from the neutral position to the left and right sides, from the neutral position. Backward swing is possible.

  When the traveling speed change lever 27 is swung forward from the front / rear neutral position, the operating mechanism 31 causes both the HSTs 14 and 14 to transmit the forward power to the left and right crawler traveling devices 1 and 1. When the operating arms 18 and 18 are pivoted together, and the traveling speed change lever 27 is swung backward from the front / rear neutral position, both the HSTs 14 and 14 provide the reverse power to the left and right crawler traveling devices 1. 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1. Each operation arm 18 is rotated by the operating mechanism 31 so that a neutral state in which power is not transmitted to the traveling device 1 is achieved.

  When the steering operation of turning the steering handle 29 from the neutral position to the left or right side is performed, the crawler type traveling device 1 on the rotational operation side is driven to travel at a lower speed than the other crawler type traveling device 1. When the steering handle 29 is steered to the left-right neutral position, the operating mechanism 18 rotates the operating arm 18 of each HST so as to turn to the side, and the claw-type traveling devices 1, 1 on both the left and right sides are the same. Each operating arm 18 is rotated by the operating mechanism 31 so as to be driven to travel at a speed.

  Incidentally, the operating mechanism 31 operates each HST 14 so that the power transmitted to the crawler type traveling device 1 becomes higher as the amount of forward / backward swing operation from the neutral position of the traveling speed change lever 27 becomes larger, and the steering. The operation mechanism 31 operates each HST 14 so that the difference in speed between the left and right crawler type traveling devices 1 and 1 increases as the amount of rotation operation from the neutral position of the handle 29 increases.

  In other words, the operation mechanism 31 is configured to rotate each operation arm 18 to an appropriate position according to the operation position of the travel shift lever 27 and the operation position of the steering handle 29.

  The above-described shift switch 28 provided on the travel shift lever 27 is an operating tool for switching the shift mechanism to a high speed state by an on / off operation. And a control device 32 (see FIG. 5) that controls the engine speed or controls the shift switching of the transmission mechanism 19.

  FIG. 5 is a block diagram of the control device. The control device 32 includes a main control unit (control unit) 33 composed of a microcomputer and the like, and an engine control unit 34 composed of a microcomputer and the like that controls the entire engine 4 including the rotational speed and the like. 33 and the engine control unit 34 are communicably connected by CAN or the like.

  On the input side of the main control unit 33, a pickup sensor 36, which is a rotation number detection means, and the above-described shift switch 28 are connected to detect the engine rotation number, while the output side of the main control unit 33 is connected. In addition, a transmission means 37 and 37 which are a pair of electromagnetic proportional control valves for hydraulically operating the transmission clutch 24 of the transmission mechanism 19 to the high speed side and the low speed side are connected, and the main control unit 33 is used for the engine. The engine 4 is configured to be able to control the rotational speed of the engine 4 via the controller 34. Incidentally, the pickup sensor 36 is specifically installed on the transmission shaft 13 and is configured to detect the engine rotation speed by detecting the rotation speed of the transmission shaft 13.

  On the input side of the engine control unit 34, a throttle sensor 38, which is an operation speed detection means for detecting an installation value (operation speed) of a setting operation tool (not shown) such as a throttle lever for setting and operating the engine speed. The engine control unit 34 is configured to control the engine speed based not only on the control signal from the main control unit 33 but also on the detected operation speed.

  FIG. 6 is a process flow diagram of the main control unit in the case of performing shift switching control of the transmission mechanism. When the process is started, the main control unit 33 proceeds to step S1. In step S1, the on / off state of the speed change switch 28 is detected, and if it is turned on, the process proceeds to step S2 to bring the speed change mechanism 19 into a high speed state.

  In step S2, the engine speed is detected by the pickup sensor 36, and from the detected engine speed, the rotational speed of the power input to the HST pump 16 (specifically, when the transmission mechanism 19 is switched to a high speed state) , The rotational speed of the pump drive shaft 22) is calculated as the input rotational speed, and if this input rotational speed is lower than the predetermined set rotational speed, the process proceeds to step S3. Incidentally, the set input rotation speed is the upper limit rotation speed for maintaining the transmission efficiency by the HST 14 or a slightly lower rotation speed than this upper limit, and higher speed power is input to the HST pump 16. If it is done, transmission efficiency will deteriorate.

  In step S3, since the power higher than necessary is not input to the HST pump 16 based on the determination in step S2, the speed change mechanism 19 is switched or held by the speed change means 37, 37 to the step ST3. The process returns to S1.

  On the other hand, if the input rotational speed is equal to or higher than the set input rotational speed in step S2, the transmission efficiency of the HST 14 deteriorates and the unnecessarily high speed power is generated by the HST pump if the speed change mechanism 19 is set to the high speed state. Therefore, even if the speed change switch 28 is turned on, the process proceeds to step S4 in order to switch or hold the speed change mechanism 16 in the low speed state. In step S4, the speed change mechanism 37, 37 switches or holds the speed change mechanism 19 to the low speed state, and the process returns to step S1.

  If it is detected in step S1 that the shift switch 28 is turned off, the process proceeds to step S4 in order to switch or maintain the transmission mechanism 16 in the low speed state.

  According to the processing flow as described above, when an unnecessary shift command is issued by the shift switch 28 so that the transmission mechanism 19 enters a high speed state when the engine speed is higher than a predetermined speed, the main control unit 33 Regardless of the speed change command, the speed change mechanism 19 is kept in a low speed state, so that the rotational speed of the power input to the HST pump 16 falls within a predetermined setting range.

  As described above, since the rotational speed of the power input to the HST pump 16 can be stably stored in the preset range in advance, the engine speed is set to various values by the setting operation tool described above. Even when various operations are performed, the transmission efficiency of the HST 14 can be stably maintained in a good state.

  In the above-mentioned example, the transmission efficiency of the HST 14 is maintained in a good state by appropriately controlling the shift switching of the transmission mechanism 19, but the engine speed is appropriately controlled to improve the transmission efficiency of the HST 14. May be retained.

  FIG. 7 is a process flow diagram of the main control unit in the case of performing the engine speed control unit. When the process is started, the main control unit 33 proceeds to step S11. In step S11, whether the shift switch 28 is turned on or off is detected, and if it is turned on, the process proceeds to step S12. In step S12, the transmission mechanism 19 is switched or held in the high speed state, and the process proceeds to step S13.

  In step S13, the operation speed is detected by the throttle sensor 38. If the operation speed is higher than the preset operation speed, the process proceeds to step S14. Incidentally, when the engine speed becomes higher than the set operation speed, the input speed becomes higher than the set input speed. For this reason, in step S14, a control signal is output to the engine control unit 34 so that the engine speed becomes the set operation speed, and the process returns to step S11.

  On the other hand, in step S13, when the operation speed is the same as or lower than the preset operation speed, the input speed is set and input even when the engine speed becomes the set operation speed. Since the engine speed is the same as or lower than the set input speed, the process proceeds to step S15 in order to set the engine speed to the set operation speed. In step S15, a control signal is output to the engine control unit 34 so that the engine speed becomes the operation speed currently detected by the throttle sensor 38, and the process returns to step S11.

  If it is detected in step S11 that the shift switch 28 is turned off, the process proceeds to step S16. In step S16, the speed change mechanism 19 is switched to or held in the low speed state, and the process proceeds to step S15 where the control signal is sent to the engine control unit 34 so that the engine speed becomes the operation speed detected by the throttle sensor 38. And returns to step S11. Incidentally, when the speed change mechanism 19 is switched to the low speed state, the low speed state of the speed change mechanism 19 is set so that the input speed does not become higher than the set input speed regardless of the engine speed. The gear ratio is set.

  According to the processing flow as described above, since the engine speed is controlled so that the input speed is lower than the set input speed, it is possible to obtain the same effect as in the above case. .

Next, based on FIG. 8, the structure of the boarding / alighting step 39 is demonstrated.
8A and 8B are a side view and a plan view of the getting-on / off step, respectively. On the front part of the traveling frame 8 in the front-rear direction, a boarding step 39 protruding outward is formed. Further, the upper side of the getting-on / off step 39 is covered with a cover body 41. The cover body 41 is attached and fixed to the traveling frame 8 side by a pair of front and rear mounting members 42 fixed on the traveling frame 8 side. An insertable gap S is formed.

  Thus, by covering the upper side of the getting-on / off step 39 with the cover body 41, it is possible to prevent the splashed mud and the like from adhering to the upper surface side of the getting-on / off step 39 and collecting.

Next, a different point from the above-mentioned example is demonstrated about the other examples of boarding / alighting step S39 based on FIG.
FIGS. 9A and 9B are a side view and a plan view showing the configuration of another example of the getting-on / off step. The cover body 41 shown in the figure is formed in a wedge shape with the front and rear central portions raised upward in a side view. Accordingly, even if mud or the like adheres to the upper surface side of the cover body 41, the mud or the like slides down, so that mud or the like can be prevented from accumulating.

1 Crawler type traveling device (traveling device)
4 Engine 14 HST (hydraulic continuously variable transmission)
16 HST pump (hydraulic pump)
17 HST motor (hydraulic motor)
19 Transmission mechanism 33 Main control unit (control unit)

Claims (3)

  An HST pump (16) driven by power from the engine (4) and an HST motor (17) configured to output power to the traveling device (1) side are provided, and the HST (14) ) Is a work vehicle that continuously shifts the power transmitted to the traveling device (1), and the power transmission from the engine (4) is shifted to a high and low and is transmitted to the HST pump (16). Work vehicle provided with.   A control section (33) for controlling the shift switching of the transmission mechanism (19) is provided, and the control section (33) is configured so that the rotational speed of the power input to the HST pump (16) falls within a predetermined setting range. In addition, the work vehicle according to claim 1, wherein the shift switching of the transmission mechanism (19) is controlled in accordance with the engine speed, regardless of a transmission command to the transmission mechanism (19).   A control unit (33) for controlling the engine speed and the shift switching of the transmission mechanism (19) is provided, and the control unit (33) has a predetermined rotational speed of power input to the HST pump (16). The work vehicle according to claim 1, wherein the engine speed is controlled so as to be within a set range.

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