JP2009144850A - Continuously variable transmission type work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuously variable transmission type work vehicle capable of reducing manufacturing cost and an adjusting maintenance load, while securing common operability, in a vehicle speed operation part for continuously variably adjusting a vehicle speed in response to a stepping quantity of a forward pedal and a backward pedal by individual pedal specifications. <P>SOLUTION: This continuously variable transmission type work vehicle includes the individually arranged forward pedal 1a and backward pedal 1b, and a continuously variable transmission mechanism 8 capable of continuously variable transmission travel by performing shift operation to a forward-backward target transmission speed corresponding to respective pedal operations. The forward pedal 1a and the backward pedal 1b have a pedal sensor 3s connected to crank levers 3a and 3b for rotatably operating a common rotary shaft 3 in the mutually different directions in response to the respective stepping quantities and detecting its rotation quantity, and a transmission speed control part 5 for adjusting a transmission speed of the continuously variable transmission mechanism 8 in response to a sensor signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a continuously variable work vehicle capable of adjusting a forward / rearward traveling vehicle speed in a stepless manner in accordance with a depression amount of a forward pedal and a reverse pedal.

As shown in Patent Document 1, there is known a work vehicle including a speed operation unit that operates a transmission speed of a continuously variable transmission mechanism by a forward / reverse pedal configured to be stepped on. Since the speed operation unit is connected from the pedal to the speed adjustment unit of the continuously variable transmission mechanism via a link, the transmission speed of the continuously variable transmission mechanism is adjusted in response to the forward and backward operation of the pedal. The forward / backward traveling of the aircraft can be adjusted at the traveling speed corresponding to the pedal operation.
JP 2005-233260 A

  However, since the speed operation unit of the work vehicle is a mechanical linkage mechanism, it is indispensable to deal with an increase in operation load, rust, etc. due to adhesion of mud and dust accompanying field work, and a mechanical component. In order to cope with the deterioration of operability due to backlash of the linkage mechanism as well as operation adjustment according to fluctuations in operability of vehicle speed adjustment due to pedal depression, complicated maintenance according to the elapsed operation period of the work vehicle Is required.

  Such a problem can be solved by a control system that adjusts the transmission speed of the continuously variable transmission mechanism by controlling the actuator based on the detection signal of the pedal operation. In addition to the problem of increased cost due to the complexity of the configuration of the speed operation unit, there is a problem of the work load for adjusting the difference in detection characteristics of both sensors and making the operability uniform. is there.

  The problem to be solved is the manufacturing cost and adjustment while ensuring common operability for the vehicle speed operation part for adjusting the vehicle speed steplessly according to the depression amount of the forward pedal and the reverse pedal by the individual pedal specifications. An object is to provide a continuously variable work vehicle capable of reducing a maintenance load.

  According to the first aspect of the present invention, the forward pedal and the reverse pedal, which are individually disposed so as to be able to be depressed to adjust the forward and reverse vehicle speeds, and the forward / reverse target transmission speed corresponding to the respective pedal operations are shifted. In the continuously variable work vehicle having a continuously variable transmission mechanism that enables continuously variable speed travel, the forward pedal and the reverse pedal rotate in different directions with respect to a common rotation shaft according to the amount of depression. A pedal sensor connected to a moving crank lever and detecting a pedal depression amount based on a rotation amount thereof, and a transmission speed control unit for adjusting a transmission speed of the continuously variable transmission mechanism according to the sensor signal. And

  When the forward pedal and the reverse pedal are individually depressed, the rotation shafts connected via the corresponding crank levers rotate in different directions, so the rotation angle of the rotation shaft is detected. The vehicle traveling speed is adjusted by the common sensor detection characteristic according to the operation of the forward pedal and the reverse pedal by the transmission speed control unit that adjusts the transmission speed of the continuously variable transmission mechanism in response to the sensor signal.

According to a second aspect of the present invention, in the configuration of the first aspect, the transmission speed control unit is the same at an adjustment speed corresponding to a difference between a current transmission speed and a target transmission speed at a speed adjustment time of the continuously variable transmission mechanism. Adjust the transmission speed of the continuously variable transmission mechanism.
The continuously variable transmission mechanism is adjusted by a rapid operation when the transmission speed is away from the target, and is adjusted by a slow operation when the transmission speed approaches the target.

  In the continuously variable work vehicle according to the first aspect of the present invention, since the individual pedal operations of the forward pedal and the reverse pedal are grasped by a common pedal sensor, the stepping amount of the forward pedal and the reverse pedal according to the individual pedal specifications is determined. In addition, the pedal operation detection means for adjusting the vehicle speed steplessly can reduce the manufacturing cost and maintenance load while ensuring common operability with a simple configuration.

  According to the invention of claim 2, since the transmission speed of the continuously variable transmission mechanism is adjusted quickly when it is away from the target, and is adjusted slowly when approaching the target, it ensures responsiveness of pedal operation, The target transmission speed can be adjusted with high accuracy.

Embodiments specifically configured based on the above technical idea will be described below with reference to the drawings.
A tractor, which is an example of a continuously variable work vehicle, includes a transmission 1 having a continuously variable transmission mechanism provided at a floor position of a control unit, as shown in a plan view (a) and a side view (b) of FIG. And the forward pedal 1a and the reverse pedal 1b are arranged at the lateral positions. The transmission 1 shifts the traveling power transmitted from the engine steplessly and transmits it to the traveling wheels to adjust the forward / rearward traveling vehicle speed, and performs shift control of the transmission 1 in accordance with each pedal depression operation. A transmission speed control device (not shown) is provided.

  FIG. 1A is a system configuration diagram of a transmission speed control device for a continuously variable work vehicle. This transmission speed control system adjusts the speed adjustment part of the continuously variable transmission mechanism to the target speed position so as to correspond to the input side for detecting the stepping operation of the forward pedal and the reverse pedal arranged so that the stepping operation can be performed, and the pedal operation. An output side to be driven and a controller for performing device control processing on the output side based on the detection signal on the input side.

  On the input side, the forward pedal 1a and the reverse pedal 1b, the rods 2a and 2b connected from the pedals 1a and 1b, and the forward and backward movements of the rods 2a and 2b are rotated in different directions with respect to the common rotational shaft 3. It is composed of crank levers 3a, 3b that convert to operation, and a pedal sensor 3s that detects the depression position of the pedal by the rotation angle of these crank levers 3a, 3b. In addition, if necessary, a vehicle speed sensor 4a, a throttle sensor 4b, An oil temperature sensor 4c or the like is provided, and each detection signal is input to the transmission speed control unit 5 by a digital controller or the like.

  The output side depends on the hydraulic cylinder 6a that is an actuator that is expanded and contracted by the electromagnetic hydraulic control valve 6b, the crank lever 7 that rotates about the support shaft 7a in response to the expansion and contraction, and the rotation angle of the crank lever 7 A trunnion sensor 7s for detecting the rotational position of the speed adjusting unit by the trunnion shaft 8a and a continuously variable transmission mechanism 8 connected from the crank lever 7 via a rod 7b. The continuously variable transmission mechanism 8 is a hydrostatic forward / reverse continuously variable transmission mechanism, abbreviated as HST, and the transmission speed is adjusted by the rotation angle of the trunnion shaft 8a, which is the speed adjusting portion thereof. Adjust forward and backward and travel speed steplessly.

  In this case, as to the speed adjustment of the continuously variable transmission mechanism 8, as shown in FIG. 1 (b), as necessary, the crank lever 7 is replaced with the electric motor 6c instead of the hydraulic cylinder 6a as necessary. It can be constituted by a gear-driven electric actuator.

  A specific configuration will be described. On the input side of the controller, as shown in a perspective view of FIG. 2, a single pedal link unit includes a forward pedal 1a and a reverse pedal 1b to a pedal sensor 3s for detecting the operation. Configure as. As shown in the side view of FIG. 3, the internal structure of this unit is a forward pedal 1a at a side portion of the transmission 1 for adjusting a vehicle speed of a work vehicle such as a tractor by installing a continuously variable transmission mechanism 8. And the reverse pedal 1b are arranged in parallel in close proximity by a common support shaft 1c, and crank levers 3a and 3b are connected to the rear ends of the rods 2a and 2b with adjusters connected from the pedals 1a and 1b. The levers 3a and 3b convert the forward / backward movement of the rods 2a and 2b with respect to a common rotational shaft 3 into rotational movements in different directions, and a pedal sensor 3s is disposed with respect to the integrally provided working arm 3e, and its swing angle Is detected. Since the pedals 1a and 1b, the pedal sensor 3s, and the rods 2a and 2b are attached to the floor F that is mounted and supported with respect to the transmission 1, vibrations from the transmission 1, that is, vibrations from the airframe side. Therefore, the detection accuracy of the pedal sensor 3s is improved.

  The input side unit by the pedal link unit is rotated about the common rotation shaft 3 via the corresponding rods 2a, 2b and crank levers 3a, 3b when one of the forward pedal 1a and the reverse pedal 1b is depressed. The pedal sensor 3s detects the rotation angle corresponding to the pedal depression operation via the action arm 3e. When the other pedal is depressed, the corresponding crank levers 3a and 3b are rotated in the reverse direction, and as a result, the reverse rotation angle is detected by the pedal sensor 3s.

  On the output side, as shown in the side view of FIG. 4, the hydraulic cylinder 6a is arranged along the side surface of the transmission 1 and the crank lever 7 connected to the piston rod is pivotally supported by the support shaft 7a. A trunnion sensor 7 s for detecting the swing angle of the crank lever 7 is disposed, and a trunnion arm 8 b that is a crank lever integrated with the trunnion shaft 8 a of the transmission 1 at the front end of a rod 7 b connected from the crank lever 7. Are connected to the side surface of the transmission 1 so that they are aligned with the input unit. Further, a cam 8c is formed on the trunnion arm 8b, and a neutral arm 8e acting on the cam 8c is attached by a neutral spring 8d so as to return the trunnion arm 8b to the neutral position.

  With the output side configuration, when the piston rod of the hydraulic cylinder 6a that is hydraulically controlled moves forward and backward, the trunnion shaft 8a that is integral with the trunnion arm 8b is rotated via the crank lever 7 and the rod 7b, so The swash plate of the variable hydraulic motor of the continuously variable transmission mechanism 8 is rotated to adjust the transmission speed, and the hydraulic cylinder 6a is controlled to expand and contract based on the signal of the trunnion sensor 7s that detects the adjustment position of the trunnion shaft 8a. This makes it possible to adjust the required speed. Further, when the control hydraulic pressure of the hydraulic cylinder 6a is released, the trunnion arm 8b is returned to a predetermined neutral position by the cam 8c that receives the acting force of the neutral arm 8e, and the vehicle travel is stopped.

  When the pedal sensor 3s detects the depression of the forward pedal 1a and the reverse pedal 1b, the transmission speed control unit 5 determines the target speed position of the trunnion shaft 8a according to the signal, and the trunnion shaft 8a is the target speed position. The hydraulic cylinder 6a is controlled by the electromagnetic hydraulic control valve 6b based on the signal of the trunnion sensor 7s until it becomes equal to. As a result, the traveling vehicle speed of the aircraft can be adjusted according to the pedal operation.

  The transmission speed control unit 5 detects the respective stepping operation amounts of the forward pedal 1a and the reverse pedal 1b via the common pedal sensor 3s by the configuration on the detection side. With a simple configuration, the transmission speed control device for adjusting the vehicle speed in a stepless manner according to the amount of steps 1a and 1b can reduce the manufacturing cost and the maintenance load while ensuring common operability.

  In this case, as shown in the transmission speed control division diagram in FIG. 5, the transmission speed control unit 5 sets the transmission speed at an adjustment speed according to the difference between the current speed position and the target speed position of the continuously variable transmission mechanism. Adjust. Specifically, as shown in the flowchart of FIG. 6, by comparison processing with the target value (S1), if the distance from the target speed position is far away, continuous output (S2a, S2c) is performed as a quick adjustment to the target speed position. As the speed approaches, by adjusting the transmission speed of the continuously variable transmission mechanism 8 with a pulse output (S2b) for only a few bits before the target, the response speed of the pedal operation is ensured and the target speed position is accurately adjusted. Speed can be controlled.

  Further, as shown in the flowchart of the determination process of the trunnion target as shown in FIG. 7, the trunnion target is neutralized within the range of a certain angle from the pedal release position by the detection classification determination (S11) of the pedal sensor 3s (S12). By configuring the control process as described above, it is possible to reliably ensure neutral (stop) even if there is pedal play or the like.

(Sensor failure response)
In addition to the above control, as a backup for sensor failure, when the pedal position is outside the neutral region when starting the engine, the trunnion target is set to the neutral position until the neutral region is detected once. In the case where the sensor that detects the failure shows an abnormal value, it is possible to avoid a situation in which the vehicle suddenly starts when the engine is started, so that safety can be ensured.

(For brake)
In relation to the brake operation, even if the brake is depressed and the trunnion 8a changes to the deceleration side, if the brake is still depressed, it is judged as a dangerous state, and the trunnion 8a is driven and controlled neutrally. If necessary, safety can be ensured by combining the engine stop output.

(Engine rotation support)
Next, the engine rotation response control will be described. As shown in a control block diagram of FIG. 8, the engine speed sensor 11 is provided to configure the transmission speed control unit 5 of the continuously variable transmission mechanism 8 that adjusts the vehicle speed of the tractor. As shown in the flowchart of FIG. 9A, the control by the transmission speed control unit 5 detects the depression position of the forward pedal 1a or the reverse pedal 1b by the pedal sensor 3s (S21), and the controller 5 according to the detected position. The trunnion target position is calculated by (S22), and the trunnion cylinder 6a is expanded and contracted by the trunnion sensor 7s. The control of the trunnion cylinder 6a is controlled according to the engine rotation as shown in the regulation characteristic diagram of FIG. 9B. Thus, the operation area of the trunnion cylinder 6a is regulated (S23).
By such a control process, it is possible to solve the problem that the engine drops and stalls when the trunnion 8a is moved to the high speed side by excessive depression of the pedal when the engine speed is low.

  As shown in FIG. 10, the control process of the control device is limited to when the engine rotation is in the low rotation region and the sub-shift is “high speed” with respect to the restriction of the operation range of the trunnion 8a (S31, By performing S32), the usable area of the trunnion 8a is not unnecessarily narrowed.

  Further, since the trunnion cylinder 6a has an allowance for thrust, even when the traveling load becomes large, the trunnion cylinder 6a may operate as it is and may drop and stall the engine. As shown in the flowchart of FIG. 11, the position sensor 4b is provided to constitute a control process for changing the operation speed of the trunnion cylinder 6a (S42a, S42b) in accordance with the engine rotation fluctuation (S41). As described above, the engine rotation fluctuation is monitored, and in a situation where the traveling load is large and the engine drops, the operation speed of the trunnion cylinder 6a can be slowed to prevent engine stall.

As for another control process, as shown in a flowchart of FIG. 12, the engine rotation sensor 11 and the throttle position sensor 4b decelerate the trunnion cylinder 6a when the engine rotation of a predetermined ratio or less with respect to the target engine rotation continues for a specified time. The control process which changes to the side (S51-S53) is comprised.
This is because when the engine speed is not the throttle command target, the trunnion position is too high with respect to the running load at that time, so it cannot be said that this is a vehicle speed zone that can secure sufficient torque. In such a state, by changing the trunnion target to the deceleration side, it is possible to secure a sufficient torque, and highly efficient work is possible.

  As for another control process, as shown in the flowchart of FIG. 13, the trunnion cylinder 6a is changed to the deceleration side according to the rate of change of the engine rotation (dropping direction) by the engine rotation sensor 11 and the throttle position sensor 4b ( S61, S62) control processing is configured. By such a control process, a highly efficient work can be performed by changing the trunnion target to the deceleration side quickly with respect to a sudden load fluctuation.

  As for the return after the target change in the above control, as shown in the flowchart of FIG. 14, when the engine rotation has exceeded the target time in the vicinity of the target, return to the original trunnion target after being changed to the deceleration side (S71 to S71). S73) The control process is configured. As described above, the return to the original position is performed in a state where the load is stabilized to some extent, so that the situation where the deceleration and the acceleration are frequently repeated can be prevented.

System configuration diagram (a) of transmission speed control device and other configuration example (b) Perspective view of input side unit Side view of the internal configuration of the input unit Side view of the output side Transmission speed control division diagram Speed control flowchart An enlarged side view of the main part of the trunnion shaft drive Control block diagram of engine rotation control Flow chart of control (a) and its regulation characteristic diagram (b) Flow chart for sub-transmission Flow chart of another control process Flowchart for further control processing Flowchart for further control processing Flow chart for return after target change Top view (a) and side view (b) of the tractor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shift transmission 1a Forward pedal 1b Reverse pedal 3 Rotating shaft 3a, 3b Crank lever 3s Pedal sensor 5 Controller (transmission speed control part)
6a Hydraulic cylinder (trunnion cylinder)
6b Electromagnetic hydraulic control valve 7 Crank lever 7s Trunnion sensor 8 Continuously variable transmission mechanism 8a Trunnion shaft (speed adjustment part)
8b trunnion arm

Claims (2)

The forward pedal (1a) and the reverse pedal (1b), which are individually arranged so as to be able to be depressed to adjust the forward and reverse vehicle speeds, and the forward and backward target transmission speeds corresponding to the respective pedal operations are not changed. In a continuously variable work vehicle including a continuously variable transmission mechanism (8) that enables step-variable traveling,
The forward pedal (1a) and the reverse pedal (1b) are connected to crank levers (3a, 3b) that rotate in different directions with respect to a common rotation shaft (3) according to the respective depression amounts. A pedal sensor (3s) that detects a pedal depression amount based on a rotation amount, and a transmission speed control unit (5) that adjusts the transmission speed of the continuously variable transmission mechanism (8) according to the sensor signal. Continuously variable work vehicle.   The transmission speed control unit (5) transmits the continuously variable transmission mechanism (8) at an adjustment speed according to the difference between the current transmission speed and the target transmission speed at the time of speed adjustment of the continuously variable transmission mechanism (8). The continuously variable work vehicle according to claim 1, wherein the speed is adjusted.

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