JP4590616B2 - Sub-transmission device for work equipment - Google Patents

Description

  The present invention relates to a sub-transmission device for a working machine such as a combine.

  2. Description of the Related Art Conventionally, a technique in which a working shift such as a combiner or a tractor is equipped with an HST transmission and a main shift lever is operated to perform a traveling shift is known. In such a working machine, it has been conventionally performed to provide a sub-transmission device so that the traveling speed can be changed so that the work can be performed more finely during the work.

  For example, Patent Document 1 filed by the same applicant as the present application discloses a sub-transmission device for a work machine in which a sub-transmission switch is provided in a grip portion of a main transmission lever that performs main transmission. Each time is pressed, the sub-shift state is alternately switched between “high speed” and “low speed”, and it can be operated with a finger while holding the grip portion of the main shift lever with one hand.

As described above, in the technique disclosed in Patent Document 1, the main transmission lever can be operated with one hand in accordance with the load and the desired speed, and the speed can be changed steplessly. Therefore, the operation can be performed simply by moving the finger, and the operability is improved.
Japanese Patent No. 3607932

  After that, there are many elderly people who are engaged in agriculture from the people involved in agriculture, and after operating the auxiliary shift switch, after a while, the auxiliary shift state is currently set to "high speed" or set to "low speed". There was a request to make this easy to understand. Therefore, in the present invention, in view of such a point, the technique disclosed in Patent Document 1 is improved to further improve the convenience, and the safety at the time of starting the work machine or during work is improved. It is an object of the present invention to provide a sub-transmission device for a work machine that achieves this.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

In claim 1, a variable displacement hydraulic pump (91) driven by power from an engine (80) and a variable displacement hydraulic motor (92) driving a drive wheel are connected by a hydraulic closed circuit. Type transmission (9), a main transmission lever (2) for continuously changing speed by operating an angle of a movable swash plate (91b) of the hydraulic pump (91), and a movable swash plate of the hydraulic motor (92) (92b) is provided in a sub-shift lever (3) that shifts in two stages of “low speed” and “high speed” in the sub-shift state by a link mechanism, and a grip portion of the main shift lever (2). Display means (6) for displaying the sub-shift state in the sub-transmission device of the working machine, comprising a sub-transmission switch (27) that switches the state between "low speed" and "high speed" alternately by the actuator (31). In the control section (1) In a state where the lever (3) is set to "low speed", when the sub shift state by the sub shift switch (27) is switched from "low speed" to "high speed", switching check means for checking the switching is provided. It is provided .

According to a second aspect of the present invention, in the auxiliary transmission device for the working machine according to the first aspect, the reset means for resetting the auxiliary transmission state by the auxiliary transmission switch (27) to "low speed" when the electric system of the working machine is turned on. Is provided.

According to a third aspect of the present invention, in the auxiliary transmission device for the working machine according to the first or second aspect, the operation is performed in a state where the auxiliary transmission state by the auxiliary transmission switch (27) is switched to "high speed". In the case of failure, notification means for notifying that effect is provided.

According to a fourth aspect of the present invention, in the sub-transmission device for the working machine according to the second aspect, the reset means is configured such that the sub-transmission switch (27) is provided even when the main transmission lever (2) is switched to the reverse side. The sub-shift state by is reset to “low speed”.

According to a fifth aspect of the present invention, in the sub-transmission device for the working machine according to any one of the first to fourth aspects, the sub-transmission state by the sub-transmission switch (27) is switched to “high speed”. When the engine load is detected as an overload condition, the solenoid valve (36) provided in the hydraulic closed circuit is operated to decelerate the vehicle speed, and the overload condition is detected continuously. The sub-shift state is switched from “high speed” to “low speed”, and when the overload state is detected, the sub-shift state is gradually switched from “high speed” to “low speed”. There is provided an overload prevention means for gradually releasing the operation of the electromagnetic valve (36) to increase the original vehicle speed.

According to a sixth aspect of the present invention, in the sub-transmission device for the working machine according to any one of the first to fifth aspects, the sub-transmission state by the sub-transmission switch (27) is switched to “high speed”. In this state, there is provided shift control means for switching the sub-shift state from “high speed” to “low speed” when the hydraulic pressure of the hydraulic closed circuit is equal to or higher than a predetermined pressure and the vehicle speed is equal to or lower than the predetermined speed.

The present invention configured as described above has the following effects.
According to the first aspect of the present invention, the auxiliary transmission switch is provided in the grip portion of the main transmission lever, and is configured to switch the auxiliary transmission state by switching the speed ratio of the hydraulic motor in sequence each time the auxiliary transmission switch is pressed. This sub-shift state is displayed on the display means, so that the current sub-shift state is not lost and convenience is improved. Also, with this configuration, the current sub-shift state can be reliably grasped, and no erroneous operation is performed against the current sub-shift state, and safety is improved.

In addition , when the sub-shift lever is set to “low speed” while the sub-shift lever is set to “low speed”, for example, when the sub-shift state is switched from “low speed” to “high speed”, the switching is switched. It is configured so as not to be damaged by the restraining means and damage the auxiliary transmission, and an unreasonable gear shift is suppressed to improve safety.

In the second aspect of the invention, when the work machine is powered on and the work machine is started, the sub shift state by the sub shift switch is always reset to “low speed”. Thus, the vehicle does not start with the sub-shift state set to “high speed”, and safety is improved.

Furthermore, in the invention described in claim 3 , when the work is performed in a state where the sub shift state by the sub shift switch is switched to “high speed”, the fact is notified by the notifying means, and the operator is notified. Attention is urged and safety is improved.

According to the fourth aspect of the present invention, even when the work implement is moved backward, the sub-shift state by the sub-shift switch is once reset to “low speed”, so that safety is improved.

In the fifth aspect of the present invention, the rapid speed control mounted on the conventional working machine (the vehicle speed is automatically decelerated when the engine load during work approaches the limit, and automatically when the engine load is reduced). It is possible to cope with an overload that cannot be dealt with under the control of returning to the original vehicle speed, and the operator can perform a work such as a mowing work without performing any operation, thereby improving convenience.

Thus, in the invention according to claim 6, the hydraulic pressure of the hydraulic closed circuit is equal to or higher than the predetermined pressure and the vehicle speed is equal to or lower than the predetermined speed in a state where the sub shift state by the sub shift switch is switched to “high speed”. In this case, the sub shift state is switched from “high speed” to “low speed” by the shift control means without operating the sub shift switch, and convenience is improved.

  Next, an embodiment of the present invention will be described with reference to the drawings. Hereinafter, a combine will be described as an example of a work machine. However, the work machine may be a tractor, a rice transplanter, or the like, and is not particularly limited.

  First, the combine control unit 1 will be described. As shown in FIG. 1, a handle column 50 is erected in front of a driver's seat 7 on which an operator sits, and a handle shaft (not shown) projects upward from a central portion of the upper surface of the handle column 50. A steering handle 5 which is a steering operation means is attached to the upper end of the steering wheel. Further, a leg portion 61 that supports the display device main body 60 protrudes upward from the front end portion of the upper surface of the handle column 50, and the display device main body 60 extends rearward (from the driver's seat 7 side) from the upper end of the leg portion 61. In addition, the upper surface of the display device main body 60 is disposed in a state inclined slightly rearward and downward from the horizontal state. The display panel 6 is attached to the upper surface of the display device main body 60, and is arranged at an angle that is easy for a worker sitting on the driver's seat 7 to see.

  As shown in FIG. 2, the display panel 6 that is a display means is composed of, for example, a large-screen liquid crystal panel that occupies most of the upper surface of the display device body 60, and the display device body 60 including the display panel 6. Are arranged so as to be located in the center in the loop-shaped handle portion 5a of the steering handle 5 in plan view. Since the display device main body 60 is fixed only to the handle column 50 via the leg portion 61 and is not connected to the steering handle 5, the display device main body 60 is displayed even if the steering handle 5 is rotated. The apparatus main body 60 is prevented from moving.

  On the upper surface of the display device main body 60, in front of the liquid crystal panel 6, a work lamp 65 that is turned on when a power switch for turning on and off the electric system of the entire combiner is turned on is disposed. Are provided with two switches 66, 67, 68 and 69 as input means for switching the screen display. Each of these switches 66, 67, 68, 69 is a so-called push switch that outputs a single ON pulse signal when the switch is pressed once, and is a non-lock type switch, each of which has a plurality of roles. It has become.

  Left and right inner bulges 5b and 5c bulging inward are formed at left and right symmetrical positions of the handle 5a of the steering handle 5, and the left and right inner bulges 5b and 5c are horizontal to the body. Four-way operation switches 53 and 54 are provided for control, for raising and lowering the cutting and for controlling the working depth, respectively. The left and right four-way operation switches 53 and 54 are configured to be operated with a thumb or the like in both the straight movement and the turning operation in a state where the operator holds the handle portion 5a of the steering handle 5. Improvements are being made.

  As shown in FIG. 1, a side column 8 having a longitudinal direction directed in the front-rear direction is disposed on one side of the driver seat 7 (left side in the present embodiment). Are arranged with a main transmission lever 2 for continuously changing the vehicle speed and an auxiliary transmission lever 3 for setting and holding the output and rotation speed of the travel drive unit 24 within a predetermined range according to the working state. A work clutch lever 4 for turning on and off the work power is arranged at the rear, and these levers 2, 3, 4 are configured to be able to rotate back and forth.

  In the front part of the side column 8, the main transmission lever 2 and the auxiliary transmission lever 3 are juxtaposed side by side, and the main transmission lever 2 as the main transmission means is located inside the auxiliary transmission lever 3 as the auxiliary transmission means (driver's seat). 7 side). The work clutch lever 4 is configured to be movable along the “L” -shaped guide groove in a plan view. When the work clutch lever 4 is positioned at the rear end outside position of the guide groove, the cutting switch and the threshing switch are When the cutting operation is performed, the reaping clutch is turned off and the threshing clutch is turned off, and only the threshing switch is turned on and operated at the rear end inner position, and the cutting clutch is turned off and the threshing clutch is turned on. At the front end position, the cutting switch is turned on and operated together with the threshing switch so that the cutting clutch is “on” and the threshing clutch “on”.

  Next, the main transmission lever 2 will be described. As shown in FIGS. 1 and 3, the main speed change lever 2 is composed of a multi-function almighty shift lever that can operate a plurality of functions together with the main speed change. A grip portion 20 is attached to the upper end portion so that an operator can hold and operate with one hand (left hand in the present embodiment). The upper half part of the grip part 20 serving as the operation part is formed so as to be inclined forward and upward, and is disposed at an angle that is easy for a worker sitting on the driver's seat 7 to see the upper half part of the grip part 20. On the upper surface 20a, a machine body tilt switch 21, a cutting speed shift switch 22, a cutting depth switch 23, a cutting part lifting switch 24, a cutting part auto lift switch 25, a cutting part auto set switch 26, which are constituted by four-way operation switches, An auxiliary transmission switch 27 is arranged.

  The body tilt switch 21 can be moved up and down by changing the height of the combine body relative to the crawler type traveling device by operating up and down, and can be moved up and down with respect to the left and right crawlers by operating in the left and right direction. Therefore, the cutting speed shift switch 22 is a push button switch for switching the rotational speed of the cutting section provided at the front end of the combine body. The handling depth switch 23 is a switch that detects the position of the tip of the harvested culm and rotates a vertical conveying device for conveying the culm to an appropriate position in the handling cylinder. The mowing unit raising / lowering switch 24 is configured to move the mowing unit up and down by pressing the upper and lower buttons. When the upper and lower buttons are pressed lightly, the mowing unit moves up and down slowly, and when the upper and lower buttons are pushed deeply, the mowing unit It consists of a two-stage switch that moves up and down quickly. The mowing unit auto lift switch 25 raises the mowing unit to the set height just by pushing at the end of mowing, and at the same time lowers the reel to a predetermined height, thereby scraping the cereal into the mowing unit and reducing the loss at the mowing unit. It is configured to prevent. The cutting unit auto-set switch 26 sets all automatic devices (cutting height automatic control, reel tuning control, cutting unit horizontal control, reel automatic height control) of the cutting unit to an automatic control state simply by pressing at the beginning of cutting. It is configured so that the operation at the start of cutting can be easily performed with one touch. The sub transmission switch 27 as the second sub transmission means is constituted by a push button switch that switches the speed ratio of the hydraulic motor in order and switches the sub transmission state between “high speed” and “low speed” each time it is pressed. It is configured so that it can be easily operated with a single touch.

  With the configuration as described above, the operator can operate by gripping the steering handle 5 with the right hand and gripping the grip portion 20 of the main speed change lever 2 with the left hand, and holding the grip portion 20. Further, the operation of these switches 21 to 27 can be performed with the thumb of the left hand so that the operability is improved.

  Next, the traveling HST transmission 9 for the main shift and the sub shift will be described. 4 is a perspective view from the front of the transmission case 90 mounted on the combine. FIG. 5 is a perspective view from the back of the transmission case 90. The upper part of the transmission case 90 has an HST transmission 9 for traveling. And an HST transmission 99 for turning (see FIG. 7).

  As shown in FIGS. 6 and 7, the traveling HST transmission 9 includes a variable displacement hydraulic pump 91 that is driven by power from an engine 80 that is an internal combustion engine, and hydraulic oil supplied from the hydraulic pump 91. The variable displacement type first hydraulic motor 92 and the fixed displacement type second hydraulic motor 93 driven by the engine 80 are provided. An output shaft 80a from the engine 80 is provided with a hydraulic pump 91 via a counter case 88 and a power transmission mechanism 89. The power is transmitted to the input shaft 91a.

  The hydraulic pump 91 is connected to the first hydraulic motor 92 and the second hydraulic motor 93 by a hydraulic closed circuit 94, and the first hydraulic motor 92 and the second hydraulic motor 93 are driven by the hydraulic oil discharged from the hydraulic pump 91. It is the composition which becomes. The first hydraulic motor 92 and the second hydraulic motor 93 are connected by a power transmission mechanism 83, and the second hydraulic motor 93 rotates at a constant ratio with respect to the rotation of the first hydraulic motor 92. . The power transmission mechanism 83 can be constituted by a gear or the like, but the output shafts of the first hydraulic motor 92 and the second hydraulic motor 93 can also be directly connected. An output shaft 93a is connected to the second hydraulic motor 93, and the driving force generated by the first hydraulic motor 92 and the second hydraulic motor 93 is transmitted to the output shaft 93a.

  In the above configuration, when the power transmission mechanism 83 connects the first hydraulic motor 92 and the second hydraulic motor 93 so as to rotate at a ratio of 1: 1, the hydraulic oil discharge amount of the hydraulic pump 91 is The rotational output of the output shaft 93a is determined by the ratio of the amount of hydraulic fluid drawn by the first hydraulic motor 92 and the second hydraulic motor 93.

  That is, when the sum of the suction amounts of the first hydraulic motor 92 and the second hydraulic motor 93 is small, the rotational speed of the output shaft 93a increases, and the sum of the suction amounts of the first hydraulic motor 92 and the second hydraulic motor 93 is reduced. When the number is large, the rotational speed of the output shaft 93a is small.

  The output shaft 93a from the second hydraulic motor 93 of the traveling HST type transmission 9 drives the axles 81a and 81a of the drive wheels 81 and 81 via the power transmission mechanism 84 and the differential mechanism 85, and the differential The mechanism 85 is configured such that power is transmitted also from the turning HST transmission 99 via the power transmission mechanism 107. The turning HST transmission 99 includes a variable displacement hydraulic pump driven by power from the engine 80 and a variable displacement hydraulic motor driven by hydraulic oil supplied from the hydraulic pump. An output shaft 80a from the engine 80 is configured to transmit power to the input shaft 99a of the hydraulic pump via the power transmission mechanism 108.

  Next, the operation of the traveling HST transmission 9 will be described. The operation lever for changing the angle of the movable swash plate 91b of the hydraulic pump 91 and the main transmission lever 2 are connected via a link mechanism, and the angle of the movable swash plate 91b of the hydraulic pump 91 is determined by the main transmission lever 2. The operation oil can be changed by the above operation, and the discharge amount of the hydraulic oil from the hydraulic pump 91 can be adjusted. The movable swash plate 91b of the hydraulic pump 91 rotates in accordance with the operation amount of the main transmission lever 2, and the discharge amount of hydraulic oil from the hydraulic pump 91 can be changed steplessly and the discharge direction can be changed. It is configured so that advance and main shift can be performed simultaneously.

  The operating lever 97 (see FIG. 4) for changing the angle of the movable swash plate 92b of the first hydraulic motor 92 and the auxiliary transmission lever 3 are connected via a link mechanism. The angle of the movable swash plate 92b is configured to be changed in two steps, high and low, by operating the auxiliary transmission lever 3, so that the amount of hydraulic oil sucked into the hydraulic motor 92 can be adjusted.

  With such a configuration, the displacement of the hydraulic pump 91 is controlled by operating the main transmission lever 2 and the displacement of the first hydraulic motor 92 is controlled by operating the auxiliary transmission lever 3 to perform a shifting operation. Can be done. Thus, it is possible to configure the traveling HST transmission 9 that can cope with high rotation and has a wide range of gear ratios.

  Further, the movable swash plate 92b of the first hydraulic pump 92 is configured to be operable by the auxiliary transmission switch 27 provided on the grip portion 20 of the main transmission lever 2, and the hydraulic motor 92 is also operated by the actuator 31 described below. It is structured to be controlled.

  As shown in FIGS. 5 and 8, the actuator 31 includes a swash plate operating piston 32 and an oil path switching electromagnetic valve 33, and hydraulic oil is supplied to the oil path switching electromagnetic valve 33 from a hydraulic pump 34. The swash plate operating piston 32 is operated by sliding the oil path switching electromagnetic valve 33. The swash plate operating piston 32 is connected via a link mechanism to a second operating shaft that changes the angle of the movable swash plate 92b of the hydraulic motor 92. By sliding of the swash plate operating piston 32, the hydraulic motor 92 is connected. The angle of the movable swash plate 92b is controlled. The oil path switching electromagnetic valve 33 is provided with two types of oil paths, and is configured to control the inclination angle of the movable swash plate 92b of the hydraulic motor 92 in two stages.

  Next, the combine control structure will be described. As shown in FIG. 9, the controller 10 serving as a combine control means includes an actuator 31 for switching the angle of the movable swash plate of the hydraulic motor between a “high speed” position and a “low speed” position, and a sub-speed change state “ The auxiliary transmission switch 27 that switches between “high speed” and “low speed”, the display panel 6 that displays various information of the combine, and an overload sensor 35 that is an overload detection means that detects an overload state of the engine load; A high-speed solenoid valve 36 interposed in the hydraulic closed circuit 94 of the traveling HST transmission 9 for increasing or decreasing the hydraulic oil supplied to the hydraulic motor 92, and the traveling HST transmission 9 is connected to a hydraulic pressure sensor 37 that is a hydraulic pressure detection means for detecting the hydraulic pressure of the hydraulic closed circuit 94 and a vehicle speed sensor 38 that is a vehicle speed detection means for detecting the vehicle speed of the combine. The auxiliary transmission lever 3 is configured to switch the speed ratio by switching the angle of the movable swash plate 92b of the first hydraulic motor 92 between a "high speed" position and a "low speed" position via a link mechanism. ing.

  Each time the sub-shift switch 27 is pressed, it outputs an operation signal indicating that the operation has been performed to the controller 10, and an operation signal is output from the controller 10 to the actuator 31, and the actuator 31 receives an operation signal. In addition, the operating position of the actuator 31 is sequentially switched between the “high speed” position and the “low speed” position, and the sub-shift state is alternately switched between “high speed” and “low speed” with no clutch, The switched “high speed” or “low speed” sub-shift state is displayed largely over the entire screen on the display panel 6 disposed in the middle of the steering handle 5, and the operator sitting on the driver's seat 7. Is configured to be clearly visible. In this configuration, the number of times the sub-shift switch 27 is pressed is forgotten and the current sub-shift state is not lost, so that convenience is improved and the current sub-shift state can be reliably grasped. There is no longer any erroneous operation against the sub-shift state, and safety is improved.

  Further, the controller 10 checks the switching when the sub shift state by the sub shift switch 27 is switched from “low speed” to “high speed” while the sub shift lever 3 is set to “low speed”. A switching check program 11 as a switching check means, a reset program 12 as a reset means for resetting the sub shift state by the sub shift switch 27 to “low speed” when the power of the electric system of the combine is turned on, and a sub program by the sub shift switch 27 A notification program 13 is incorporated as notification means for notifying on the display panel 6 when work is performed in a state where the shift state is switched to “high speed”.

  The switching check program 11 switches the sub shift state by the sub shift switch 27 from “low speed” to “high speed” at any time when the sub shift lever 3 is set to “low speed” during operations such as crossing over the fence. In such a case, the actuator 31 is not actuated and a warning is displayed on the display panel 6 so that the subtransmission is not damaged, and an unreasonable shift is suppressed and safety is ensured. The improvement of the property is aimed at. This caution display is configured to be displayed on the display panel 6 for a short time and then switched to a screen showing the current sub-shift state.

  The reset program 12 is configured so that the auxiliary transmission state by the auxiliary transmission switch 27 is always reset to “low speed” when the combine electric system is turned on and the combine is started. Thus, safety is improved without starting with the sub-shift state set to “high speed”. Further, the reset program 12 is configured to reset the sub shift state by the sub shift switch 27 to “low speed” even when the main shift lever 2 is switched to the reverse side, and when the combine is moved backward. In addition, since the sub shift state by the sub shift switch 27 is once reset to “low speed”, the safety is further improved.

  When the sub-shift state by the sub-shift switch 27 is switched to “high speed”, the notification program 13 displays a large warning on the display panel 6 over almost the entire screen. The display can be clearly seen by the worker sitting on the driver's seat 7, and the operator is alerted through vision and safety is improved. This warning display is displayed on the display panel 6 for a short time and then switched to a screen showing the current sub-shift state.

  Further, the controller operates the rapid solenoid valve 36 when the overload sensor 35 detects that the engine load is overloaded while the subshift state by the subshift switch 27 is switched to “high speed”. If the overload sensor 35 continuously detects the engine load overload state, the sub-shift state is switched from “high speed” to “low speed”, and the overload sensor 35 When it is detected that the load is overloaded, the actuator 31 is operated to gradually switch the sub-shift state from “high speed” to “low speed”, and then the rapid solenoid valve 36 is gradually operated. The overload prevention program 14 as overload prevention means for releasing and increasing the original vehicle speed and the sub-shift state by the sub-shift switch 27 are switched to “high speed”, the hydraulic pressure When the sensor 37 detects that the hydraulic pressure of the hydraulic closed circuit 94 is equal to or higher than a predetermined pressure and the vehicle speed sensor 38 detects that the vehicle speed is equal to or lower than the predetermined speed, the actuator 31 is operated to change the sub-shift state from “high speed” to “ A shift control program 15 as a shift control means for switching to “low speed” is incorporated.

  In the overload prevention program 14, the rapid speed control installed in the conventional combine (when the engine overload sensor 35 detects that the engine load is overloaded, the rapid solenoid valve 36 is activated to automatically decelerate the vehicle speed. When the overload sensor 35 detects that the engine load is overloaded, it can handle overload that cannot be handled by the control of releasing the rapid solenoid valve 36 and automatically returning it to the original vehicle speed. Therefore, the operator can perform a work such as a mowing operation without performing any operation, and convenience is improved.

  In the shift control program 15, when the sub-shift state by the sub-shift switch 27 is switched to “high speed” and the hydraulic pressure of the hydraulic closed circuit 94 is equal to or higher than a predetermined pressure and the vehicle speed is equal to or lower than the predetermined speed, the sub-shift switch Without operating 27, the sub-shift state is automatically switched from "high speed" to "low speed", improving convenience.

The perspective view which shows the structure of the control part of a combine. The top view which shows the structure of the steering handle of a combine. The front view which shows the structure of the main transmission lever. The perspective view from the diagonal front of a mission case. The perspective view from diagonally backward of a mission case. The hydraulic circuit diagram which shows the structure of an HST type transmission. The skeleton figure which shows the power transmission structure from an HST type transmission. The figure which shows the structure of the actuator which controls the movable swash plate of a 1st hydraulic motor. The block diagram which shows the control structure of a combine.

DESCRIPTION OF SYMBOLS 1 Control part 2 Main transmission lever 3 Sub transmission lever 5 Steering handle 6 Display panel 7 Driver's seat 8 Side column 9 HST transmission 10 Controller 11 Switching check program 12 Reset program 13 Notification program 14 Overload prevention program 15 Shift control program 20 Grip portion 27 Sub shift switch 31 Actuator 35 Overload sensor 36 Rapid solenoid valve 37 Hydraulic sensor 38 Vehicle speed sensor 91 Hydraulic pump 92 First hydraulic motor 93 Second hydraulic motor

Claims (6)

An HST transmission (9) in which a variable displacement hydraulic pump (91) driven by power from the engine (80) and a variable displacement hydraulic motor (92) driving drive wheels are connected by a hydraulic closed circuit. A link mechanism that connects the main transmission lever (2) for continuously changing the speed of the movable swash plate (91b) of the hydraulic pump (91) and the movable swash plate (92b) of the hydraulic motor (92). The sub-shift lever (3) that shifts in two stages of “low speed” and “high speed” in the sub-shift state, and the grip portion of the main shift lever (2), the sub-shift state is set to “low speed”. In a sub-transmission device for a work machine having a sub-transmission switch (27) that is alternately switched between "high speed" by an actuator (31), display means (6) for displaying the sub-transmission state is provided on the control section (1). The auxiliary transmission lever (3) In a state where "the is set, when the subtransmission state by the sub shift switch (27) is switched from" slow "to" fast ", characterized in that the switching換牽system means for restraining the switching is provided A sub-transmission for a working machine.   The sub-shift of the work implement according to claim 1, further comprising a reset means for resetting a sub-shift state by the sub-shift switch (27) to "low speed" when the electric system of the work implement is turned on. Transmission device.   The informing means for informing that when an operation is performed in a state in which the sub-shift state by the sub-shift switch (27) is switched to "high speed" is provided. The subtransmission for a work machine according to claim 2. Said reset means, the main speed change lever (2) when is switched to the reverse side, the auxiliary shifting state wherein by subtransmission switch (27) to claim 2, characterized in that resetting the "slow" A sub-transmission device for the working machine described When the sub-shift state by the sub-shift switch (27) is switched to “high speed” and the engine load is detected as an overload state, the solenoid valve (36) interposed in the hydraulic closed circuit is set. When the vehicle is decelerated to reduce the vehicle speed and an overload condition is continuously detected, the sub-shift state is switched from “high speed” to “low speed”. And an overload prevention means for gradually releasing the operation of the solenoid valve (36) and increasing the speed to the original vehicle speed after gradually switching the sub-shift state from "high speed" to "low speed". The subtransmission for a working machine according to any one of claims 1 to 4, wherein When the sub-shift state by the sub-shift switch (27) is switched to “high speed” and the hydraulic pressure of the hydraulic closed circuit is equal to or higher than a predetermined pressure and the vehicle speed is equal to or lower than the predetermined speed, the sub-shift state is changed to “ 6. A sub-transmission device for a working machine according to claim 1, further comprising a shift control means for switching from "high speed" to "low speed".