JP4195628B2 - Working vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a working traveling vehicle such as a crawler tractor that shifts traveling power by a hydraulic continuously variable transmission.
[0002]
[Prior art]
2. Description of the Related Art A working vehicle such as a crawler tractor that shifts traveling power by a hydraulic continuously variable transmission (HST) is known. In general, this type of working vehicle has a main transmission lever linked to a swash plate of a hydraulic continuously variable transmission, and performs a vehicle speed operation and a stop operation of the traveling machine body based on the operation of the main transmission lever. Many have a brake pedal for emergency stop.
[0003]
However, when stopping the aircraft by depressing the brake pedal, the driving force of the hydraulic continuously variable transmission acts on the vehicle, so it not only receives a large shock when operating the brake pedal, but also stops the aircraft. If you later remove your foot from the brake pedal, the aircraft may start moving again. For this reason, in recent years, there has been proposed a mechanism equipped with a mechanism for automatically returning the main transmission lever and the hydraulic continuously variable transmission mechanism (swash plate) to the low speed side in accordance with the depression operation of the brake pedal (for example, a patent References 1 and 2).
[0004]
[Patent Document 1]
JP-A-8-99565 (page 3, Fig. 2)
[Patent Document 2]
JP 2002-302062 A (5th page, FIG. 11)
[0005]
[Problems to be solved by the invention]
However, in the ones disclosed in Patent Documents 1 and 2, the swash plate is accurately returned to the neutral position even if the main transmission lever or the hydraulic continuously variable transmission mechanism is returned to the low speed side according to the depression operation of the brake pedal. Since there is no guarantee, there is a possibility that the traveling aircraft does not stop reliably. Therefore, in Patent Documents 1 and 2, in order to return the swash plate to the neutral position when the brake pedal is operated, it is necessary to finely adjust mechanical parts such as the main shift lever return mechanism with extremely high accuracy, which is troublesome for maintenance. There was a problem that it took.
[0006]
[Means for Solving the Problems]
The present invention has been created with the object of solving these problems in view of the above-described circumstances, and is a hydraulic pressure that shifts traveling power with supply oil corresponding to the angle of the swash plate of the swash plate type variable displacement pump. and wherein the continuously variable transmission, a main speed change lever for operating the angle of the swash plate, in a work vehicle and a brake pedal for operating the travel brake mechanism by depressing operation, to the working vehicle, the brake pedal The main transmission lever returning mechanism that returns the main transmission lever to the low speed side in response to the depression operation of the brake pedal, and the swash plate operation oil path is short-circuited in response to the depression operation of the brake pedal, thereby making the swash plate a neutral angle Upon Ru provided a bypass valve back to the travel brake mechanism, the main shift lever return mechanism, and the bypass valve, the brake pedal is depressed The main shift lever return mechanism is returned to the low speed side according to the depression amount of the brake pedal, and the bypass valve is switched before the brake pedal reaches the lower limit to return the swash plate to the neutral position. A working vehicle characterized in that the traveling brake mechanism is linked to operate . In other words, the bypass valve short-circuits the swash plate operating oil path in response to the depression of the brake pedal, so that the swash plate can be set to the neutral angle without fine adjustment of the mechanical parts such as the main transmission lever return mechanism. It is possible to return accurately and to stop the traveling aircraft reliably. Moreover, since it is possible to avoid the brake from acting on the traveling machine body when the driving force of the hydraulic continuously variable transmission is applied, not only the generation of shock due to the brake can be suppressed, but also the burden on the traveling brake mechanism can be reduced, and the traveling brake can be reduced. The mechanism can be miniaturized.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, one embodiment of the present invention will be described with reference to the drawings. In the drawings, 1 is a traveling machine body of a crawler tractor, and the traveling machine body 1 is covered with an engine 2 mounted on the front part of the machine body, a transmission 3 for inputting engine power, a crawler type traveling unit 4 and a cabin 5. An operation unit 6 and a work machine connection unit 7 to which a work machine (not shown) is connected are configured. The work machine connecting portion 7 includes a lift arm cylinder 8 and a lift rod cylinder 9, and is configured to move the work machine up and down by the lift arm cylinder 8 and to tilt the work machine left and right by the lift rod cylinder 9. .
[0008]
As shown in FIG. 2, the traveling machine body 1 includes a working system hydraulic circuit 10 that hydraulically operates the work machine connection unit 7 and a traveling system hydraulic circuit 11 that hydraulically operates the traveling unit 4. The working system hydraulic circuit 10 includes a hydraulic pump 12 driven by the output of the transmission 3, a hydraulic take-out valve 13 for supplying hydraulic pressure to an attachment and the like, a priority valve 14 for diverting the supply oil from the hydraulic pump 12, A position control valve 15 for operating the lift arm cylinder 8, a flow control valve 16 for adjusting the lowering speed of the work implement, and a lift rod valve 17 for operating the lift rod cylinder 9 are configured.
[0009]
The traveling system hydraulic circuit 11 switches the HST pump unit 18 driven by the output of the transmission 3, the left and right traveling motor units 19 operated by oil supplied from the HST pump unit 18, and high / low speed switching of the traveling motor unit 19. The auxiliary transmission switching valve (electromagnetic valve) 20 to perform, a parking brake valve (electromagnetic valve) 21 for braking the traveling motor unit 19, and a bypass valve 22 for short-circuiting the swash plate control oil path of the HST pump unit 18 are configured. ing. In the present specification, a hydraulic continuously variable transmission system including the HST pump unit 18 and the traveling motor unit 19 is referred to as a hydraulic continuously variable transmission.
[0010]
The HST pump unit 18 includes a pair of swash plate type variable displacement pumps 23 that can adjust the discharge oil amount steplessly based on the angle control of the swash plate. A discharge oil amount control valve 25 is connected to a swash plate operation port of each swash plate type variable displacement pump 23 via a pair of swash plate operation oil passages 24. The swash plate angle of the pump 23 is controlled. The above-described bypass valve 22 is connected to a pair of swash plate operating oil passages 24, and shorts them to return the swash plate of the swash plate type variable displacement pump 23 to a neutral angle.
[0011]
The traveling motor unit 19 is operated by oil supplied from the swash plate type variable displacement pump 23, and mechanically brakes the rotation of the driving wheel 4a and the swash plate type variable displacement motor 26 that rotationally drives the driving wheel 4a of the traveling unit 4. A parking brake (traveling brake mechanism) 27, a high / low speed switching valve 28 for switching the traveling speed between two levels of high and low based on swash plate angle control of the swash plate type variable displacement motor 26, and a relief valve 29 for adjusting the pressure of the closed loop circuit. And a shuttle valve 30. The sub-transmission switching valve 20 described above pilot-operates the high / low-speed switching valve 28, and the parking brake valve 21 switches the operation of the parking brake 27.
[0012]
As shown in FIG. 3, a hydraulic box 32 that houses a hydraulic system is provided below the driver's seat 31. The bypass valve 22 is provided at the front of the hydraulic box 32, and a pair of swash plate operation arms 33 connected to the discharge oil amount control valve 25 are provided on one side of the hydraulic box 32. Yes. These swash plate operation arms 33 are connected to the steering wheel 34 and the main transmission lever 35 and are turned in the reverse direction according to the turning angle of the steering wheel 34, while in response to the operation of the main transmission lever 35. It is rotated in the same direction. As a result, the turning operation of the traveling unit 4 by the steering wheel 34 becomes possible, and the stepless traveling speed change operation by the main speed change lever 35 becomes possible. In addition, since the connection structure of the steering wheel 34 and the swash plate operation arm 33 is not the main part of this invention, illustration and description are abbreviate | omitted.
[0013]
The main transmission lever 35 is provided on one side of the driver's seat 31 so as to be pivotable back and forth. The base end portion of the main transmission lever 35 is connected to a connecting arm 39 in front of the driver's seat via a rod 36, a bell crank 37 and a rod 38, and the connecting arm 39 is further connected to a pair of wires 40 and the like. Are connected to the swash plate operating arm 33. As a result, the swash plate operating arm 33 is rotated in accordance with the operation of the main transmission lever 35, and the traveling power is continuously variable, but conversely, by rotating the connecting arm 39 back and forth. The rotation position of the main transmission lever 35 can be changed.
[0014]
A brake pedal 41 is provided at the front foot portion of the driver seat 31. The brake pedal 41 is supported by a pedal support shaft 42 so as to be rotatable up and down, and is urged upward by a spring 43, and is normally restricted by an upper limit stopper 44 from rotating. On the other hand, when the brake pedal 41 is depressed, the lower limit stopper 45 defines the depression amount. The lower limit stopper 45 is constituted by a bolt screwed to the bracket 46, and the lower limit position of the brake pedal 41 is adjusted by changing the screw position. In the drawing, reference numeral 47 denotes an upper limit detection switch for detecting the return of the upper limit of the brake pedal 41. When the upper limit detection switch 47 is OFF, a brake lamp (not shown) is turned on.
[0015]
In the vicinity of the base end portion of the brake pedal 41, a depression detection switch 48 for detecting depression of the brake pedal 41 is provided. The stepping detection switch 48 is adjusted in its mounting position so that the detection operation is performed when the brake pedal 41 reaches the lower limit or when the brake pedal 41 reaches a position immediately before it. The parking brake valve 21 described above is electrically connected to the stepping detection switch 48 and operates the parking brake 27 in response to the switch 48 being turned on. As a result, the parking brake 27 can be operated by depressing the brake pedal 41.
[0016]
Further, a main transmission lever return mechanism 49 for returning the main transmission lever 35 to the low speed side (neutral position) and a bypass valve interlocking mechanism 50 for operating the bypass valve 22 are connected to the brake pedal 41 according to the depression operation. Has been. The main transmission lever return mechanism 49 is a link mechanism for connecting the arm 41a protruding from the base end portion of the brake pedal 41 and the connecting arm 39, and has two arms 51a and 51b protruding. The shaft member 51 includes a connecting plate 52 that connects one arm 51 a to the arm 41 a of the brake pedal 41, and a rod 53 that connects the other arm 51 b to the connecting arm 39. Then, the main transmission lever return mechanism 49 returns the main transmission lever 35 to the neutral side according to the depression amount of the brake pedal 41, and returns the main transmission lever 35 to neutral when the brake pedal 41 reaches the lower limit. The dimensions have been adjusted. Further, the arm 51a and the connecting plate 52 are connected via an accommodation mechanism including a pin 51c and a long hole 52a, and the length of the long hole 52a is the amount of movement of the pin 51c when the main transmission lever 35 is operated in the entire region. Is set larger than. As a result, it is possible to operate the main transmission lever 35 in a state where the linkage with the brake pedal 41 is released during normal times.
[0017]
The bypass valve interlocking mechanism 50 switches the bypass valve 22 before the brake pedal 41 reaches the lower limit (before the parking brake 27 is operated) when the brake pedal 41 is depressed, The arm 54 includes a movably supported arm, a push rod 55 extending from the arm 54 toward the brake pedal 41, and a wire 56 that connects the arm 54 to the bypass valve 22. The push rod 55 passes through the bracket 46 of the lower limit stopper 45 so as to be able to protrude and retract, and is positioned so that the tip thereof is slightly closer to the pedal than the pedal contact position of the lower limit stopper 45. That is, when the brake pedal 41 is depressed, the push rod 55 is pushed in before the brake pedal 41 reaches the lower limit, and switches the bypass valve 22 via the arm 54 and the wire 56. Thereby, before the parking brake 27 operates, not only can the swash plate of the HST pump unit 18 be returned to the neutral angle and the airframe can be stopped reliably, but also the braking load on the parking brake 27 can be reduced. Is possible.
[0018]
In the configuration as described above, a hydraulic continuously variable transmission (HST pump unit 18 and travel motor unit 19) that shifts the traveling power according to the angle of the swash plate, and a main transmission that operates the angle of the swash plate The traveling machine body 1 includes a lever 35 and a brake pedal 41 that operates the parking brake 27 by a stepping operation. The traveling body 1 moves the main transmission lever 35 to a low speed side in response to the depression operation of the brake pedal 41. The main speed change lever return mechanism 49 and the bypass valve 22 for returning the swash plate to the neutral angle by short-circuiting the swash plate operation oil passage 24 according to the depression operation of the brake pedal 41 are provided. Even if the mechanical part such as the mechanism 49 is not finely adjusted with high accuracy, the swash plate can be accurately returned to the neutral angle, and the traveling machine body 1 can be surely stopped.
[0019]
When the brake pedal 41 is depressed, the swash plate is returned to the neutral position by the main transmission lever return mechanism 49 or the bypass valve 22 and then the parking brake 27 is operated. The parking brake 27 can be prevented from working in a state where the driving force is applied. As a result, not only can the occurrence of shock due to the brake be suppressed, but also the braking load on the parking brake 27 can be reduced and the parking brake 27 can be downsized. Can do.
[0020]
Needless to say, the present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, a main transmission lever, a brake pedal, a swash plate operation arm, a bypass valve, and the like are mechanically connected. Needless to say, a hydraulic connection structure or an electric connection structure can be adopted.
[Brief description of the drawings]
FIG. 1 is a side view of a crawler tractor.
FIG. 2 is a hydraulic circuit showing a hydraulic system of a crawler tractor.
FIG. 3 is a side view showing an operation unit of the crawler tractor.
FIG. 4 is an enlarged view of the main part.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Traveling machine body 4 Traveling part 6 Operation part 11 Traveling system hydraulic circuit 18 HST pump part 19 Traveling motor part 21 Parking brake valve 22 Bypass valve 23 Swash plate type variable capacity pump 24 Swash plate operation oil path 25 Discharge oil amount control valve 26 Swash plate type Variable displacement motor 27 Parking brake 33 Swash plate operation arm 35 Main transmission lever 41 Brake pedal 48 Depression detection switch 49 Main transmission lever return mechanism 50 Bypass valve interlock mechanism

Claims (1)

The hydraulic continuously variable transmission that shifts the traveling power with the oil supplied according to the angle of the swash plate of the swash plate type variable displacement pump, the main transmission lever that operates the angle of the swash plate, and the travel brake mechanism that operates by stepping on in working vehicle and a brake pedal which, in the working vehicle, in response to depression of the brake pedal, the main shift lever return mechanism for returning the main speed change lever to the low speed side, depression of the brake pedal depending on the operation, by shorting the swash plate operation oil passage, said Upon the swash plate Ru provided a bypass valve back to the neutral angle, the travel brake mechanism, the main shift lever return mechanism, and the bypass valve, the brake pedal When the pedal is depressed, the main shift lever return mechanism is operated to return to the low speed side according to the depression amount of the brake pedal, and the brake After the pedal is returned to the swash plate is switched to the bypass valve just before reaching the lower limit to the neutral position, the working vehicle being characterized in that tandem so as to operate the travel brake mechanism.

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