JP2010133469A - Working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an engine stall and degradation of rotation of an engine when a HST load torque becomes excessively large during medium to low rotation of the engine in a working vehicle including a HST traveling device. <P>SOLUTION: This working vehicle includes the HST traveling device, an operation detecting means of a governor operator for setting a target rotational speed, a controller for calculating and outputting control signals according to the target rotational speed in a capacity controller of a HST pump, and an engine rotation detecting means. When the detected rotational speed by the rotation detecting means is a set rotational speed, set lower than the target rotational speed, or less, and a state of a prescribed rotational speed, set lower than the maximum torque rotational speed of the engine, or less, or the maximum torque rotational speed of the engine or less continues over a prescribed period of time, the controller reduces the control signals, and prevents rapid degradation of the rotational speed and stopping of the engine. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a work vehicle including an HST traveling device.

The traveling speed of a work vehicle such as a wheel loader equipped with an HST traveling device which is a continuously variable transmission is determined by the discharge amount of a pump that supplies hydraulic oil to a motor that drives wheels, and the rotational speed of an engine that drives the pump. It is determined by controlling based on the traveling load pressure of hydraulic oil (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 5-331878 (FIG. 1)

  The work vehicle of the above-described form has the following problems to be solved.

  That is, as a characteristic of the HST traveling device, the traveling speed of the work vehicle varies because the discharge amount of the pump changes with the variation of the traveling load, so the working vehicle is equipped with a working device such as a road surface cleaning device, When the engine is operated at a medium to low speed and the pump discharge amount is reduced and the operation is performed at a low speed, the traction force is small. Therefore, if the travel load is excessive, the engine performance is deteriorated due to the engine stall or excessive decrease in the engine speed.

  Therefore, each time, the operator needs to perform an operation while controlling the rotational speed of the engine by operating, for example, the accelerator of the operation means. Therefore, the operator needs to pay attention to both the operation of the working device and the operation of the vehicle traveling speed, the driving operation is complicated, the burden on the body is large, and the efficient work is difficult.

  The present invention has been made in view of the above-mentioned facts, and its technical problem is that, in a work vehicle equipped with an HST traveling device, when the HST load torque becomes excessive during low-speed engine rotation, engine stall or excessive engine rotation is caused. An object of the present invention is to provide a work vehicle capable of preventing deterioration in operability due to a decrease.

  According to the present invention, as a work vehicle that solves the above problems, an operation detection means that detects an operation amount of an HST traveling device, a governor operating device that sets a target rotational speed of an engine that drives the HST pump, and a capacity of the HST pump The controller includes a controller that calculates and outputs a control signal corresponding to the target rotation speed, and a rotation detection unit that detects the rotation speed of the engine. The controller further includes a rotation speed detected by the rotation detection unit, A state where the engine speed is lower than the set rotational speed set lower than the target rotational speed corresponding to the operation amount and is lower than the predetermined rotational speed lower than the maximum torque rotational speed of the engine or lower than the maximum torque rotational speed of the engine for a predetermined time or longer. Sometimes, the control signal is reduced, the absorption torque of the HST pump is reduced, and a sudden decrease in rotational speed and engine stop are caused. To stop, a work vehicle is provided, characterized in that.

  The work vehicle configured according to the present invention has a rotation speed detected by the rotation detecting means equal to or lower than a set rotation speed set lower than the target rotation speed and lower than a predetermined rotation speed lower than the maximum torque rotation speed of the engine. When the state below the maximum torque rotation speed continues for a predetermined time or longer, the control signal to the capacity controller of the HST pump is reduced, the absorption torque of the HST pump is reduced, and a sudden decrease in the rotation speed and engine stop are prevented. To do.

  Therefore, when the HST load torque becomes excessive during low-speed rotation in the engine, it is possible to prevent deterioration in operability due to engine stall or excessive decrease in engine rotation. In addition, it is necessary to pay attention to both the operation of the working device and the operation of the vehicle traveling speed, which can solve the problem that the driving operation is complicated, the burden on the body is large, and the efficient work is difficult.

  Hereinafter, a working vehicle configured according to the present invention will be described in more detail with reference to the accompanying drawings illustrating a preferred embodiment of a wheel loader, which is a typical working vehicle.

  The wheel loader will be described with reference to FIG. The wheel loader 2 includes a front vehicle body 8 equipped with a front wheel 4 and a work arm device 6, a rear wheel 10, an engine compartment 12, a cab 14 and a rear vehicle body 16 equipped with an HST traveling device described later. A road surface cleaning device 20 having a rotating brush, a side brush, or the like, which is a working device, is attached to the working arm device 6 via a quick coupler 18. The wheel loader 2 to which the road surface cleaning device 20 is attached travels at a low speed and performs a road surface cleaning operation.

  A description will be given with reference to FIG. The wheel loader 2 (FIG. 6) has an operation amount of a governor pedal 24 which is a governor operating device for setting a target rotational speed of the HST traveling device 22 for driving the front wheel 4 and the rear wheel 10 and the engine E for driving the HST pump 22a. A pedal operation sensor 26 that is an operation detection means for detecting the engine, a controller 28 that calculates and outputs a control signal corresponding to the target rotation speed to the capacity controller 22b of the HST pump 22a, and a rotation that detects the rotation speed of the engine E. A rotation speed sensor 30 as detection means is provided.

  The HST traveling device 22 is a well-known one in which the variable displacement type HST pump 22a driven by the engine E and an HST motor 22c having an output shaft connected to the front wheels 4 and the rear wheels 10 are connected by a closed loop hydraulic circuit. It is. The capacity controller 22b of the HST pump 22a converts an electrical signal, which is a control signal from the controller 28, into a hydraulic signal by an electromagnetic valve in a swash plate type variable displacement pump, for example, and tilts the swash plate by its output hydraulic pressure. It is a well-known thing provided with the control mechanism to operate.

  The pedal operation sensor 26 outputs the depression amount of the governor pedal 24 as an electric signal corresponding to the depression angle by the potentiometer.

  This will be described with reference to FIG. The discharge amount Q of the HST pump 22a is set to increase / decrease between a “small” capacity and a “large” capacity indicated by an arrow X in accordance with the control signal corresponding to the increase / decrease in the engine speed, and the HST motor 22c. For example, the horsepower is controlled to be constant so as to increase when the traveling load (oil pressure P) decreases and decrease when the load increases.

  The controller 28 compares the target rotational speed output from the pedal operation sensor 26 with the actual rotational speed of the engine E output from the rotational speed sensor 30, and the HST pump 22a based on these rotational speeds. The capacity controller 22b is provided with an arithmetic unit 28b that calculates and outputs a control signal corresponding to the rotational speed. The computing unit 28b includes a timer 28c.

  The computing unit 28 b calculates a control signal corresponding to the target rotational speed based on the output of the pedal operation sensor 26 of the governor pedal 24 that sets the target rotational speed of the engine E described above, and the rotational speed detected by the rotational speed sensor 30. Is equal to or lower than a set rotational speed (referred to as threshold value 3) set lower than the target rotational speed and lower than a predetermined rotational speed (referred to as threshold value 2) lower than the maximum torque rotational speed of engine E (referred to as threshold value 1). When a state equal to or lower than the maximum torque rotation speed (threshold 1) continues for a predetermined time (referred to as threshold 4), a reduced control signal is calculated.

  The maximum torque rotation speed as “threshold 1” is the engine rotation speed of the engine maximum torque, as shown in FIG.

  As shown in FIG. 3, the predetermined rotational speed as “threshold value 2” is a rotational speed that is substantially between the maximum torque rotational speed and the low idle rotational speed of the engine.

  As shown in FIG. 4, the set rotational speed as “threshold 3” is higher than that at the same governor operating amount with respect to the target rotational speed that linearly changes from low idle to threshold 1 in accordance with the governor operating amount. This is a linearly changing rotation speed set low. The magnitude of the rotational speed to be set low is determined by the type of work device of the work vehicle, the work mode, and the like.

  The predetermined time T as the “threshold 4” is set by the timer 28c of the computing unit 28b, and the size thereof is determined by the type of work device, the work mode, etc. of the work vehicle.

  Further, the amount by which the control signal is reduced is also determined by the type of work device of the work vehicle, the work mode, and the like.

  The control procedure of the controller 28 will be described with reference to FIG.

  In step S1, the target rotational speed of the engine E that is the output of the pedal operation sensor 26 and the actual rotational speed of the engine E that is the output of the rotational speed sensor 30 are taken in, and the process proceeds to step S2.

  In step S2, it is determined whether the actual rotational speed of the engine E is equal to or less than the threshold value 3. If the threshold value is equal to or less than the threshold value 3, the process proceeds to step S3.

  In step S3, it is determined whether or not the actual rotational speed of the engine E is equal to or lower than a predetermined rotational speed (threshold value 2) lower than the maximum torque rotational speed (threshold value 1). Proceed to step S6.

  In step S4, the control signal calculated according to the governor operation amount is output to the capacity controller 22b, and the process returns to step S1.

  In step S5, the control signal is reduced and calculated according to the governor operation amount, and is output to the capacity controller 22b, and the process returns to step S1.

  In step S6, it is determined whether or not the actual rotational speed of the engine E is equal to or less than the maximum torque rotational speed (threshold 1). If it is equal to or smaller than the threshold 1, the process proceeds to step S7.

  In step S7, it is determined whether the engine torque maximum speed (threshold 1) or less is equal to or longer than a predetermined time T (threshold 4). If so, the process proceeds to step S5. If not, the process proceeds to step S4. .

  The effects of the work vehicle 2 as described above will be described.

  In the work vehicle 2 configured according to the present invention, the rotation speed detected by the rotation detection unit 30 is equal to or lower than a set rotation speed (set rotation speed) set lower than the target rotation speed, and the maximum torque rotation speed (threshold 1) of the engine. ) Lower than a predetermined rotational speed (threshold value 2) or lower than the maximum torque rotational speed (threshold value 1) of the engine continues for a predetermined time (threshold value 4) or more, a control signal to the capacity controller 22b of the HST pump 22a Is reduced, the absorption torque of the HST pump 22a is reduced, and a sudden decrease in the rotational speed and engine stop are prevented.

  Therefore, when the HST load torque becomes excessive during low-speed rotation in the engine, it is possible to prevent deterioration in operability due to engine stall or excessive decrease in engine rotation. In addition, it is necessary to pay attention to both the operation of the working device and the operation of the vehicle traveling speed, which can solve the problem that the driving operation is complicated, the burden on the body is large, and the efficient work is difficult.

The structure explanatory view of the work vehicle constituted according to the present invention. The characteristic line figure of the hydraulic output of an HST pump. FIG. 3 is a diagram in which the maximum torque rotation speed (threshold 1) and a predetermined rotation speed (threshold 2) are shown together in the relationship between the engine rotation speed and the output torque. The diagram which showed the relationship between the governor operation amount and the engine rotation speed at the target rotation speed and the set rotation speed (threshold value 3) set lower than the target rotation speed. The flowchart which shows the control procedure of a controller. The side view of the wheel loader which is a typical example of a work vehicle.

Explanation of symbols

2: Wheel loader (work vehicle)
22: HST traveling device 22a: HST pump 22b: capacity controller 24: governor pedal (governor operating device)
26: Pedal operation sensor (operation detection means)
28: Controller 30: Rotational speed sensor (rotation detection means)
E: Engine

Claims (1)

An HST traveling device;
Operation detecting means for detecting an operation amount of a governor operating device for setting a target rotational speed of an engine for driving the HST pump;
A controller that calculates and outputs a control signal corresponding to the target rotational speed to the capacity controller of the HST pump;
Rotation detection means for detecting the rotation speed of the engine,
The controller further includes:
The rotation speed detected by the rotation detection means is equal to or lower than the set rotation speed set lower than the target rotation speed corresponding to the operation amount.
When a state below a predetermined rotational speed lower than the maximum torque rotational speed of the engine or below the maximum torque rotational speed of the engine continues for a predetermined time
Reducing the control signal, reducing the absorption torque of the HST pump, preventing a sudden decrease in rotational speed and stopping the engine;
A working vehicle characterized by that.

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