KR20240140470A - Control system of hst for working vehicle and control method thereof - Google Patents

Abstract

The present invention relates to a control system for a hydrostatic transmission for a work vehicle and a control method thereof.
According to the present invention, the ratio control valve is controlled based on the operation of both the accelerator pedal and the deceleration pedal, thereby improving driving convenience by facilitating deceleration control while applying a hydrostatic transmission.

Description

{CONTROL SYSTEM OF HST FOR WORKING VEHICLE AND CONTROL METHOD THEREOF}

The present invention relates to a control technology for a hydrostatic transmission for a work vehicle, and more particularly to deceleration control.

Hydro-Static Transmission (HST) is being adopted in some agricultural vehicles and heavy equipment.

A hydraulic transmission consists of a hydraulic pump and a hydraulic motor.

A hydraulic transmission is designed to control the rotational direction and rotational speed of the output shaft of a hydraulic motor by changing the angle of the swash plate in the hydraulic pump.

There are two methods for adjusting the angle of the swash plate: direct and servo.

The direct type connects the accelerator pedal and the swash plate with a link structure so that the driver's operating force is directly applied to the swash plate. However, the direct type requires a large torque to the swash plate when a load is applied to the wheels, so it is difficult to adopt it in reality for vehicles with horsepower exceeding a certain level.

The servo type controls the angle of the swash plate by the advance/retreat rod of the hydraulically operated servo mechanism (servo assist). Since the servo type controls the angle of the swash plate by hydraulic pressure, the angle of the swash plate can be controlled consistently by hydraulic pressure regardless of the load applied to the wheel.

Furthermore, in order to properly control the servo mechanism, there has been a technological advancement in controlling the servo mechanism based on the displacement value of the accelerator pedal. For this purpose, a displacement sensor capable of detecting the displacement according to the rotational movement of the accelerator pedal has been applied. The displacement sensor detects the displacement value of the accelerator pedal and transmits it to the controller. Then, the controller controls the servo mechanism by generating hydraulic force corresponding to the displacement value of the accelerator pedal through the hydraulic valves. In other words, the controller controls the servo mechanism to manipulate the angle of the swash plate in proportion to the displacement value of the accelerator pedal.

Meanwhile, a strong hydraulic force is applied to the swash plate to return the swash plate to the neutral position. Therefore, when the driver removes the operating force from the accelerator pedal, the swash plate is quickly returned to the neutral position by the hydraulic pressure, causing rapid deceleration of the output shaft of the hydraulic motor. In this case, there is a problem in that the driver is subjected to an unintended shock due to the rapid deceleration. To solve this problem, a technology has been proposed to allow the accelerator pedal to be gradually returned by the damper, thereby achieving deceleration similar to that of a normal vehicle when coasting.

However, when a damper is applied, the pedaling force, which is the force used to press the pedal, increases because the resistance of the damper must be overcome, which increases the fatigue of the driver. For this reason, technological progress is being made to control the servo mechanism by adopting an electronic proportional control valve capable of program control. The present invention relates to a technology to which this electronic proportional control valve is applied.

When an electronic proportional control valve is applied, the controller can automatically control the electronic proportional control valve by the installed program.

For example, even if the driver removes the accelerator pedal to remove the operating force, the electronic proportional control valve can be controlled to gradually change the angle of the swash plate as set by the program and return the swash plate to the neutral position. The deceleration at this time can be approximated to the deceleration due to the coasting of a normal vehicle.

However, even if an electronic proportional control valve is applied, it is expected to be difficult to cope with various deceleration situations.

For example, even if the program reflects as many deceleration situations as possible, it is impossible to reflect all deceleration situations that may occur in actual driving situations.

Additionally, to reflect as many deceleration situations as possible, the program would have to be more sophisticated, which would significantly increase the production cost.

Also, as programs become more advanced, the frequency of bugs occurring increases, which can put drivers in unexpected and dangerous situations.

However, if a damper is applied, it deviates from the purpose of introducing an electronic proportional control valve. Rather, it will only have the same deceleration control function as the conventional servo type that simply proportionally increases and decreases hydraulic pressure while increasing the production cost due to the application of an expensive electronic proportional control valve.

Republic of Korea Patent No. 10-2294104 Republic of Korea Publication Patent No. 10-2012-0090268

The present invention was conceived from consideration of a technology capable of appropriately responding to various deceleration situations while controlling a hydrostatic transmission with an electronic proportional control valve.

A control system for a hydrostatic transmission for a work vehicle according to a first aspect of the present invention comprises: an accelerator lever having an accelerator pedal into which a driver's pressure is input for accelerating the work vehicle; a first displacement sensor for detecting displacement of the accelerator lever; a deceleration lever having a deceleration pedal into which a driver's pressure is input for decelerating the work vehicle; a second displacement sensor for detecting displacement of the deceleration lever; an electronic proportional control valve for adjusting an angle of a swash plate in the hydrostatic transmission, the electronic proportional control valve being capable of being controlled based on a first detection value detected by the first displacement sensor and a second detection value detected by the second displacement sensor; and a controller for controlling the electronic proportional control valve based on the first detection value and the second detection value.

It further includes an operation detection sensor that detects operation of the deceleration lever; and the controller controls the electronic proportional control valve based on the second detection value when it is confirmed by the operation detection sensor that the deceleration lever has been operated.

The above-mentioned manipulation sensor may also serve as a brake sensor for turning the brake light on/off.

The above-mentioned deceleration lever has a recognition element that can be recognized by both the second displacement sensor and the operation detection sensor.

The controller includes a first control means for controlling the electronic proportional control valve for acceleration required by the first detection value; and a second control means for controlling the electronic proportional control valve for deceleration according to the first mode when pressure is removed from the accelerator lever, and for controlling the electronic proportional control valve for deceleration according to a second mode different from the first mode when pressure is input to the deceleration lever and the second detection value is generated.

The above first mode is a deceleration control mode according to elastic driving in a state where the pressure from the accelerator lever is removed, and the above second mode is a deceleration control mode in which the deceleration amount per hour is greater than that in the first mode.

In the second mode, the controller controls the electronic proportional control valve so that when the displacement of the deceleration lever is large, the deceleration amount per hour is larger than when the displacement of the deceleration lever is small.

A control system for a hydrostatic transmission for a work vehicle according to a second aspect of the present invention comprises: an accelerator lever having an accelerator pedal into which a driver's pressure is input for acceleration of the work vehicle; a displacement sensor for detecting displacement of the accelerator lever; a deceleration lever having a deceleration pedal into which a driver's pressure is input for deceleration of the work vehicle; an operation detection sensor for detecting operation of the deceleration lever; an electronic proportional control valve for controlling an angle of a swash plate in the hydrostatic transmission, the electronic proportional control valve being controlled by a detection value detected by the displacement sensor; and a controller for controlling the electronic proportional control valve for deceleration according to a first mode when pressure is removed from the accelerator lever, and for controlling the electronic proportional control valve for deceleration according to a second mode different from the first mode when it is confirmed by the operation detection sensor that the deceleration lever has been operated.

The above first mode is a deceleration control mode according to elastic driving in a state where the pressure from the accelerator lever is removed, and the above second mode is a deceleration control mode in which the deceleration amount per hour is greater than that in the first mode.

In the second mode, the controller controls the electronic proportional control valve so that when the displacement of the deceleration lever is large, the deceleration amount per hour is larger than when the displacement of the deceleration lever is small.

The control method of a hydrostatic transmission for a work vehicle according to the present invention comprises: a first determination step of determining whether a pressure has been removed from an accelerator lever; a first deceleration execution step of controlling an electronic proportional control valve for adjusting an angle of a swash plate in a hydrostatic transmission according to a first mode to decelerate the work vehicle if it is determined in the first determination step that the pressure has been removed from the accelerator lever; and a second deceleration execution step of controlling the electronic proportional control valve according to a second mode different from the first mode to decelerate the work vehicle if a pressure is input to the deceleration lever after the first deceleration execution step.

It further includes a second judgment step for judging whether a pressure is input to the deceleration lever between the first deceleration execution step and the second deceleration execution step.

The above first mode is a mode in which deceleration is performed according to elastic driving with the pressure removed from the accelerator lever, and the above second mode is a mode in which deceleration is controlled so that when the displacement of the deceleration lever (13) is large, the deceleration amount per hour is larger than when the displacement of the deceleration lever (13) is small.

According to the present invention, the following effects are achieved.

First, since the deceleration conditions due to elastic driving can be simplified, deceleration control by an electronic proportional control valve can be easily implemented, and accordingly, the adoption of a hydrostatic transmission can be enabled in a wider range of product groups.

Second, by utilizing the brake lever as a deceleration lever, the cost of construction for application of the invention is reduced while maintaining the driver's operational accessibility as before, ensuring convenience of use.

Third, since the output shaft deceleration of the transmission and the braking deceleration by the brake can be synchronized, the imbalance between the output shaft deceleration of the transmission and the braking deceleration by the brake that may occur during the driving process is prevented, which enhances the driver's driving satisfaction and trust in the work vehicle.

Fourth, the adoption rate of hydrostatic transmissions can be improved because the program design can be simplified.

Fifth, since the pressure required to operate the accelerator lever does not increase even when a hydrostatic transmission is applied, the driver's fatigue due to operating the accelerator lever can be prevented from increasing.

FIG. 1 is a schematic conceptual diagram of a control system for a hydrostatic transmission for a work vehicle according to one embodiment of the present invention.
Figure 2 is a schematic excerpt of some configurations applied to the control system of Figure 1.
Figure 3 is a conceptual diagram of a controller applied to the control system of Figure 1.
Figure 4 is a part of a flow chart for a control method of a hydrostatic transmission performed in the control system of Figure 1.

A preferred embodiment of the present invention will be described with reference to the attached drawings, but for the sake of brevity, descriptions of well-known components are omitted or compressed as much as possible.

Before explaining, let's first look at deceleration.

In general, a vehicle can cause two types of intentional deceleration to reduce its driving speed.

One of them is the deceleration of the output shaft of the transmission, and the other is the deceleration due to braking of the wheels.

The present invention relates to deceleration of an output shaft of a hydraulic motor in a hydrostatic transmission, and does not specifically consider deceleration for braking of wheels.

Therefore, the deceleration meant in the description or claims of the present invention means the deceleration of the output shaft of the hydraulic motor. However, if it is necessary to specifically mention the deceleration due to wheel braking in connection with the description of the present invention, it will be clearly stated that it is the deceleration due to wheel braking.

FIG. 1 is a schematic conceptual diagram of a control system (10, hereinafter abbreviated as “control system”) of a hydrostatic transmission for a work vehicle according to one embodiment of the present invention.

Referring to FIG. 1, a control system (10) according to the present embodiment includes an acceleration lever (11), a first displacement sensor (12), a deceleration lever (13), a second displacement sensor (14), an operation detection sensor (15), an electronic proportional control valve (16), and a controller (17).

The accelerator lever (11) is intended to be operated by the driver to accelerate the work vehicle.

The accelerator lever (11) is equipped with an accelerator pedal into which the driver's pressure is input. Therefore, the driver can accelerate the work vehicle by stepping on the accelerator pedal with his foot and inputting the pressure to the accelerator lever (11). At this time, as is known, the driver can control the acceleration or deceleration of the work vehicle by adjusting the amount of pressure on the accelerator pedal while recognizing the driving speed of the work vehicle through the instrument panel or intuition.

The accelerator lever (11) is hinged at one point and can rotate around the hinge axis as the center of rotation, and is installed so that when the pressure is removed, it returns to the initial position by a return spring.

The first displacement sensor (12) detects displacement according to the rotational movement of the accelerator lever (11).

The first detection value detected by the first displacement sensor (12) is transmitted to the controller (17).

The first displacement sensor (12) may preferably be a potentiometer, but any sensor capable of detecting displacement according to the rotational movement of the accelerator lever (11) may be preferably applied.

In addition, it is entirely possible for the first displacement sensor (12) to be provided as a means for detecting only the linear displacement component among the rotational displacement of the accelerator lever (11). In this case, the controller (17) needs to be implemented to calculate or confirm the rotational displacement of the accelerator lever (11) using the linear displacement component.

Fig. 2 is an example of a deceleration lever (13), a second displacement sensor (14), and an operation detection sensor (15). Referring to Fig. 2, the deceleration lever (13), the second displacement sensor (14), and the operation detection sensor (15) and their installation structure will be examined.

The deceleration lever (13) is operated by the driver for deceleration and is a configuration specially introduced for the realization of the present invention.

The deceleration lever (13) is equipped with a deceleration pedal (13a) into which the driver's pressure is input. Therefore, the driver can decelerate the work vehicle according to the driver's intention by stepping on the deceleration pedal (13a) with his foot and inputting the pressure to the deceleration lever (13).

According to a preferred example of this embodiment, the driver can control the degree of deceleration by adjusting the amount of pressure on the deceleration pedal (13a).

The deceleration lever (13) is hinge-joined at one point and can rotate around the hinge axis as the center of rotation, and is installed so that when the pressure is removed, it returns to the initial position by a return spring. (a) of Fig. 2 shows a state in which no pressure is input to the deceleration pedal (13a), and (b) of Fig. 2 shows a state in which the pressure is input to the deceleration pedal (13a).

According to a preferred example of the present invention, the deceleration lever (13) may be a brake lever. That is, rather than installing a separate deceleration lever (13), the brake lever is adopted and utilized as a deceleration lever (13) for adjusting the angle of the swash plate (SP) in the hydrostatic transmission. In this case, the following various advantages may be obtained.

For example, since no separate operating lever other than the brake lever is added, the driving operation structure of the existing driver's seat can be used as is, and this minimizes the construction cost for applying the present invention.

For example, since the deceleration due to wheel braking by the deceleration lever (13) and the deceleration of the output shaft of the hydraulic motor by adjusting the angle of the swash plate (SP) in the hydrostatic transmission can be performed simultaneously, the driver can easily adjust the angle of the swash plate (SP) just by braking the wheels. Of course, the driver will not be aware of the angle adjustment of the swash plate (SP).

For example, since the deceleration of the output shaft of the hydraulic motor and the deceleration due to braking of the wheel are linked, there is no concern about an imbalance occurring between the deceleration of the output shaft of the hydraulic motor and the deceleration due to braking of the wheel. Here, an imbalance situation may be a situation in which the rotation speed of the wheel decreases rapidly while the rotation speed of the output shaft of the hydraulic motor decreases gradually.

In general, an imbalance situation causes the driver to experience discomfort in the driving situation and may reduce the durability of the brake system. In this regard, the present embodiment has the advantage of not causing such an imbalance situation because the deceleration of the output shaft of the hydraulic motor and the deceleration due to braking of the wheels are synchronized.

In particular, the fact that the deceleration of the output shaft of the hydraulic motor and the deceleration due to the braking of the wheels are synchronized means that the deceleration of the output shaft of the hydraulic motor can be appropriately controlled by the driver for many deceleration situations that can be recognized by the driver. This also means that the program to be installed in the controller (17) does not need to be designed considering all deceleration situations. Accordingly, cost reduction due to program design becomes possible, and simplicity of control by the program becomes possible.

The second displacement sensor (14) detects displacement resulting from the rotational movement of the reduction lever (13).

The second detection value detected by the second displacement sensor (14) is transmitted to the controller (17).

In Fig. 2, a potentiometer is applied as a second displacement sensor (14), and the resistance value is implemented to change as the rotary lever (14a) of the potentiometer is rotated. Of course, the change value of the resistance (detection value) can be calculated or confirmed as a displacement value according to the rotational movement in the controller (17).

Likewise, although a potentiometer may be considered preferable as the second displacement sensor (14), any sensor capable of detecting displacement according to the rotational movement of the deceleration lever (13) may be preferably applied. For example, the second displacement sensor (14) may be provided to detect only the linear displacement component among the rotational displacement of the deceleration lever (13), and in this case, the detected value may be calculated or confirmed as a displacement value according to the rotational movement through a certain relational expression. In other words, any type of sensor may be preferably applied as the second displacement sensor (14) as long as it can detect the displacement according to the rotational movement of the deceleration lever (13).

One of the important features in this embodiment is to accurately check the displacement of the reduction lever (13) by the second displacement sensor (14). This is because the electronic proportional control valve (16) needs to be controlled to adjust the angle of the swash plate (SP) in the hydrostatic transmission in response to the accurate displacement value of the reduction lever (13).

In general, all vehicles are equipped with a brake lever with a brake pedal, but there is no requirement for a sensing means for the purpose of controlling the deceleration of the output shaft of the transmission by detecting the displacement of the brake lever.

However, according to the present embodiment, since the angle of the swash plate (SP) in the hydrostatic transmission must be adjusted according to the displacement amount of the reduction lever (13), a second displacement sensor (14) capable of detecting the displacement of the reduction lever (13) simultaneously with the operation of the reduction lever (13) is required.

The manipulation detection sensor (15) detects whether the deceleration lever (13) is manipulated by the driver inputting pressure to the deceleration lever (13).

The manipulation detection sensor (15) is provided to determine the point in time at which control for adjusting the angle of the swash plate (SP) in the hydrostatic transmission begins according to the displacement amount of the reduction lever (13).

The manipulation detection sensor (15) can also serve as a brake sensor for turning the brake light on/off.

Generally, all vehicles are equipped with brake lights. Therefore, when the driver's pressure is input to the brake lever, the brake sensor detects this and the brake lights turn on. Then, when the driver's pressure is removed from the brake lever and the brake lever returns to the initial position, the brake sensor detects this and the brake lights turn off.

In this embodiment, the operation detection sensor (15) is configured to also function as a brake sensor, thereby reducing construction costs.

Preferably, the manipulation detection sensor (15) may be provided as a limit switch.

When a limit switch is applied as a manipulation detection sensor (15), when pressure is input to the deceleration lever (13), the limit switch turns off (the brake light turns on), and when the pressure is removed and the deceleration lever (13) returns to the initial position, the limit switch turns on (the brake light turns off).

Meanwhile, referring again to Fig. 2, the deceleration lever (13) has a recognition element (13b).

Figure 2 (a) shows a situation in which the recognition element (13b) operates the manipulation detection sensor (15) to the on state. Thereafter, when the driver inputs pressure using the deceleration lever (13), the state can be switched to the state as in Figure 2 (b).

Figure 2 (b) shows a state in which the recognition element (13b) is separated from the manipulation detection sensor (15) and the manipulation detection sensor (15) is turned off. In addition, it can be seen that the recognition element (13b) is rotating the rotation lever (14a) of the second displacement sensor (14).

Since the recognition element (13b) is formed or combined integrally with the operating lever (13) and rotates together with the operating lever (13), the operating detection sensor (15) can accurately detect the displacement of the deceleration lever (13).

That is, one of the important features of this embodiment is that the recognition element (13b) in the deceleration lever (13) can be recognized by both the second displacement sensor (14) and the manipulation detection sensor (15). Accordingly, there is an advantage in that the present invention can be applied without changing the structure of the deceleration lever (13).

The electronic proportional control valve (16) is intended to control the angle of the swash plate (SP) in the hydrostatic transmission by manipulating the servo mechanism (SE).

The electronic proportional control valve (16) can be controlled by the first detection value detected by the first displacement sensor (12).

And also, the electronic proportional control valve (16) can be controlled by the second detection value detected by the second displacement sensor (14). The control here is one of the important features of this embodiment.

The controller (17) controls the electronic proportional control valve (16).

The controller (17) controls the electronic proportional control valve (16) so that the swash plate (SP) in the hydrostatic transmission is adjusted to an angle corresponding to the displacement of the accelerator lever (11) based on the first detection value.

In addition, the controller (17) controls the electronic proportional control valve (16) so that the angle of the swash plate (SP) is adjusted to an angle corresponding to the displacement of the deceleration lever (13) based on the second detection value.

According to the present invention, the controller (17) controls the electronic proportional control valve (16) so that when the pressure from the accelerator lever (11) is removed, a deceleration (hereinafter defined as “deceleration due to spring driving”) similar to the deceleration during coasting (inertial driving) in a general vehicle occurs when the pressure from the accelerator pedal is removed.

That is, according to the present invention, the controller (17) controls the electronic proportional control valve (16) in an acceleration mode for acceleration based on the first detection value, but when the pressure from the accelerator lever (11) is removed, it controls the electronic proportional control valve (16) in a first mode for deceleration according to elastic driving, and when the pressure is input to the deceleration lever (13) later, it controls the electronic proportional control valve (16) in a second mode.

For example, in acceleration mode, the electronic proportional control valve (16) is controlled to accelerate in proportion to the displacement value of the acceleration lever (11) according to the first detection value.

For example, in the first mode, the electronic proportional control valve (16) is controlled so that deceleration is achieved according to elastic driving.

For example, in the second mode, the electronic proportional control valve (16) is controlled to decelerate in proportion to the displacement value of the deceleration lever (13) according to the second detection value.

In order to perform control for each mode, the controller (17) has a judgment means (17a), a first control means (17b), a second control means (17c), and a recording means (17d), as shown in Fig. 3.

The judgment means (17a) determines whether it is the acceleration mode, the first mode, or the second mode based on the detection values received from the first displacement sensor (12), the second displacement sensor (14), and the manipulation detection sensor (15).

The first control means (17b) controls the electronic proportional control valve (16) for acceleration required by the first detection value when the acceleration mode is determined by the judgment means (17a).

The second control means (17c) controls the electronic proportional control valve (16) for deceleration according to the first and second modes.

Deceleration control according to the first mode is performed from the point in time when the pressure is removed from the accelerator lever (11). In this embodiment, the point in time when the pressure is removed from the accelerator lever (11) does not mean only the point in time when the pressure is completely removed, but also needs to be understood to include the point in time when the pressure is weakened and the accelerator lever (11) begins to rotate toward the initial position.

That is, in this embodiment, the meaning that the pressure is removed from the accelerator lever (11) includes the following two states.

The first state is when the driver completely removes his foot from the accelerator pedal, thereby completely removing the pressure from the accelerator lever (11).

The second state is a state in which the driver has not lifted his/her foot off the accelerator pedal but has weakened the pressure. In this state, the accelerator lever (11) rotates to a certain degree toward the initial position, so that deceleration control according to the first mode is performed during the time period in which the accelerator lever rotates.

Of course, the first and second states above can be clearly distinguished by adding a separate input detection sensor, and in this case, the second state can be programmatically set to be included in some processes of the acceleration mode. This will be described later in a different table of contents.

Deceleration control according to the second mode is performed from the point in time when pressure is input to the deceleration lever (13).

In this embodiment, the point in time when the pressure is input to the deceleration lever (13) is the point in time when the operation of the deceleration lever (13) is detected by the operation detection sensor (15). Therefore, according to this embodiment, the point in time when the brake light turns on and the point in time when the deceleration control according to the second mode is performed are the same.

Of course, depending on the implementation, the point in time when the pressure is input to the deceleration lever (13) can be set as the point in time when the second detection value by the second displacement sensor (14) occurs. However, in order to prevent deviations due to specifications or mechanical variability of multiple work vehicles, it is necessary to uniformly define and set a clear mode switching point. Therefore, it is desirable to clearly define the mode switching point by defining the point in time when the operation of the deceleration lever (13) is detected by the operation detection sensor (15) as the point in time when the pressure is input to the deceleration lever (13).

For reference, the first control means (17b) and the second control means (17c) are not provided as separate physical objects but are functionally separated by a programmatic function.

Next, a method for controlling a hydrostatic transmission for a work vehicle using a control system (10) having the above configuration is described with reference to FIG. 4.

1. Acceleration mode driving (S51)

When the driver inputs a pressure using the accelerator lever (11), the first displacement sensor (12) transmits a first detection value (+) corresponding to the displacement of the accelerator lever (11) to the controller (17). Then, the judgment means (17a) of the controller (17) determines the acceleration mode according to the first detection value (+). Accordingly, the first control means (17b) of the controller (17) controls the electronic proportional control valve (16) to respond to the acceleration required by the first detection value (+).

Of course, the electronic proportional control valve (16) hydraulically operates the servo mechanism (SE), and the servo mechanism (SE) adjusts the angle of the swash plate (SP) to match the acceleration required by the first detection value (+), thereby driving in the acceleration mode.

2. First Judgment (S52)

When the driver lifts his/her foot off the accelerator pedal or reduces the pressure while driving in acceleration mode, the accelerator lever (11) rotates to the initial position as much as the driver requested with his/her foot. Then, the first displacement sensor (12) detects the displacement due to the rotational movement of the accelerator lever (11) and transmits the detected first detection value (-) to the controller (17). Then, the judgment means (17a) determines that the pressure has been removed from the accelerator lever (11) based on the first detection value (-).

For reference, the first detection value (+) above is the first detection value that occurs when the driver increases the pedaling amount, and the second detection value (-) is the first detection value that occurs when the driver decreases the pedaling amount.

3. First deceleration execution (S53)

If it is determined that the pressure has been removed in step S52, the second control means (17c) of the controller (17) controls the electronic proportional control valve (16) to perform deceleration according to the first mode, thereby adjusting the angle of the swash plate (SP) in the hydrostatic transmission, thereby executing deceleration of the work vehicle.

Here, deceleration according to the first mode means deceleration according to elastic driving. That is, the second control means (17c) decelerates the rotational speed of the output shaft of the hydraulic motor in the hydrostatic transmission according to the deceleration flow according to elastic driving set by the program in the first mode.

4. Second Judgment (S54)

Thereafter, when the driver inputs pressure using the deceleration lever (13), the operation detection sensor (15) recognizes this. Then, the judgment means (17a) determines that the driver inputs pressure using the deceleration lever (13).

5. Second deceleration execution (S55)

If it is determined that a pressure is input to the deceleration lever (13) at step S54, the second control means (17c) controls the electronic proportional control valve (16) according to a second mode different from the first mode to decelerate the work vehicle.

In the second mode, deceleration is executed in response to the displacement amount of the deceleration lever (13) corresponding to the second detection value detected by the second displacement sensor (14).

That is, in the second mode, when the driver's response input to the deceleration lever (13) is large, the displacement is large and the deceleration is large, and when the driver's response is small, the displacement is small and the deceleration is controlled to be small. That is, in the second mode, the controller (17) controls the electronic proportional control valve so that when the displacement of the deceleration lever (13) is large, the deceleration per hour is larger than when the displacement of the deceleration lever (13) is small.

Of course, since deceleration in the second mode is achieved by operating the deceleration lever (13), the deceleration per hour is greater than that in the first mode.

<Supplementary information about the program>

According to the present invention, it is necessary to install a program in the controller (17) to control the electronic proportional control valve (16) according to the acceleration mode, the first mode, and the second mode.

The program can be designed in various ways without departing from the scope of the present invention.

The start and end points of the acceleration mode, the start and end points of the first mode, the start and end points of the second mode, the gradient of deceleration in the first and second modes, the timing of transition from the first mode to the acceleration mode, etc. can be selected according to the type and characteristics of the work vehicle.

<Supplementary explanation on switching modes>

The above description did not describe the transition from mode 1 to acceleration mode or from mode 2 to mode 1.

However, even according to the present invention, a situation in which the first mode is switched to the acceleration mode or the second mode is switched to the first mode naturally occurs.

For example, if the driver removes pressure from the accelerator lever (11) and then inputs pressure again, the vehicle can be switched from the first mode to the acceleration mode.

For example, if the driver removes pressure from the deceleration lever (13) and then does not input pressure from the accelerator lever (11), the vehicle can be switched from the second mode to the first mode.

<Variation 1>

Although the embodiment according to FIGS. 1 and 2 is provided with the second displacement sensor (14) and the manipulation detection sensor (15) separately, a modified example in which the manipulation detection sensor (15) is omitted can also be sufficiently considered. In this case, deceleration control according to the second mode is performed at the time when the second detection value is generated by the second displacement sensor (14), and the brake light can be implemented to be switched on.

<Variation 2>

In the embodiment according to Figs. 1 and 2, a modified example in which the second displacement sensor (14) is omitted may also be considered. In this case, deceleration control according to the second mode is performed at the time when the deceleration lever (13) is operated by the operation detection sensor (15). However, since the displacement of the deceleration lever (13) cannot be confirmed according to this modified example, the deceleration in the second mode needs to be designed programmatically so that the deceleration amount per hour is at least greater than that in the first mode.

Alternatively, it may be sufficiently considered that a sensor for detecting displacement of the brake wire or a sensor for detecting displacement of some other component within the brake system is adopted instead of the second displacement sensor (14). Of course, it should be understood that the sensor for detecting displacement of the brake wire or a sensor for detecting displacement of some other component within the brake system is merely an equivalent replacement for the second displacement sensor (14) according to the present invention.

<Variation 3>

In addition to the embodiments according to FIGS. 1 and 2, the present modified example may further include an input detection sensor.

The input sensor detects whether the driver's foot is lifted from the accelerator pedal or whether the driver's foot is in contact with the accelerator pedal.

If an input detection sensor is installed, the state where the driver's foot is still on the accelerator pedal but the pressure is reduced can be programmed to be processed as part of the acceleration mode.

For example, the driver tends to change the amount of pressure on the accelerator pedal frequently while driving. At this time, it may be difficult to implement a mode change for each change in the amount of pressure. Therefore, it may be more desirable to design a program so that the electronic proportional control valve (16) is controlled by the acceleration mode while the driver's foot is kept on the accelerator pedal.

In this case, the deceleration that occurs during some process of the acceleration mode can be implemented to be proportional to the displacement value of the accelerator lever (11).

<Variation 4>

This modified example adds the technical concept of modified example 3 to the hardware structure according to FIGS. 1 and 2.

This modified example has the same structure as Figs. 1 and 2. That is, there is no input detection sensor in this modified example. Instead, the first displacement sensor (12) is designed programmatically to perform the same role as the input detection sensor of modified example 3.

According to this modified example, in a section where the accelerator lever (11) does not completely return to the initial position, deceleration control is performed based on the degree of change in the amount of pressure, and the deceleration control at this time is executed as part of the acceleration mode.

However, when the accelerator lever (11) is completely returned to the initial position by detection by the first displacement sensor (12), a mode change occurs and deceleration is performed in the first mode in which deceleration according to elastic driving is performed.

The above-described embodiments and modifications are only some of the preferred examples of the present invention, and may have more diverse application forms. Therefore, the present invention should not be understood as being limited to the contents described above. Instead, the scope of the rights of the present invention should be understood by the separately described claims and their equivalents.

10: Control system of hydrostatic transmission for work vehicles
11: Accelerator lever
12: 1st displacement sensor
13: Deceleration lever
13a: Deceleration pedal 13b: Recognition element
14: Second displacement sensor
15: Manipulation detection sensor
17 : Controller
17a: Judgment means 17b: First control means
17c: Second control means 17d: Recording means

Claims (10)

An accelerator lever (11) having an accelerator pedal into which the driver's pressure is input to accelerate the work vehicle;
A first displacement sensor (12) that detects the displacement of the above accelerator lever (11);
A deceleration lever (13) equipped with a deceleration pedal (13a) into which the driver's pressure is input to decelerate the work vehicle;
A second displacement sensor (14) that detects the displacement of the above deceleration lever (13);
An electronic proportional control valve (16) for adjusting the angle of a swash plate (SO) in a hydrostatic transmission, which can be controlled based on a first detection value detected by the first displacement sensor (12) and a second detection value detected by the second displacement sensor (14); and
A controller (17) that controls the electronic proportional control valve (16) based on the first detection value and the second detection value;
Control system of a hydrostatic transmission for work vehicles.
In the first paragraph,
It further includes an operation detection sensor (15) that detects the operation of the above deceleration lever (13);
The above controller (17) controls the electronic proportional control valve (16) based on the second detection value when it is confirmed that the deceleration lever (13) has been operated by the operation detection sensor (15).
Control system of a hydrostatic transmission for work vehicles.
In the second paragraph,
The above deceleration lever (13) has a recognition element (13b) that can be recognized by both the second displacement sensor (14) and the operation detection sensor (15).
Control system of a hydrostatic transmission for work vehicles.
In the first paragraph,
The above controller (17)
A first control means (17b) for controlling the electronic proportional control valve (16) for acceleration required by the first detection value; and
A second control means (17c) that controls the electronic proportional control valve (16) for deceleration according to the first mode when the pressure is removed from the accelerator lever (11), and controls the electronic proportional control valve (16) for deceleration according to the second mode different from the first mode when the pressure is input to the deceleration lever (13) and the second detection value is generated;
Control system of a hydrostatic transmission for work vehicles.
An accelerator lever (11) having an accelerator pedal into which the driver's pressure is input to accelerate the work vehicle;
A displacement sensor (12) that detects the displacement of the above accelerator lever (11);
A deceleration lever (13) equipped with a deceleration pedal (13a) into which the driver's pressure is input to decelerate the work vehicle;
An operation detection sensor (15) that detects the operation of the above deceleration lever (13);
An electronic proportional control valve (16) for adjusting the angle of a swash plate (SP) in a hydrostatic transmission, which can be controlled by a detection value detected by the displacement sensor (12); and
A controller (17) that controls the electronic proportional control valve (16) for deceleration according to the first mode when the pressure from the accelerator lever (11) is removed, and controls the electronic proportional control valve (16) for deceleration according to the second mode different from the first mode when it is confirmed by the operation detection sensor (15) that the deceleration lever (13) has been operated;
Control system of a hydrostatic transmission for work vehicles.
In clause 4 or 5,
The above first mode is a deceleration control mode according to elastic driving that is performed in a state where the pressure from the accelerator lever (11) is removed.
The above second mode is a deceleration control mode with a greater deceleration rate per hour than the above first mode.
Control system of a hydrostatic transmission for work vehicles.
In clause 4 or 5,
In the second mode, the controller (17) controls the electronic proportional control valve so that when the displacement of the deceleration lever (13) is large, the deceleration amount per hour is larger than when the displacement of the deceleration lever (13) is small.
Control system of a hydrostatic transmission for work vehicles.
A first judgment step (S52) for judging whether the pressure has been removed from the accelerator lever (11);
If it is determined in the first judgment step (S52) that the pressure from the accelerator lever (11) has been removed, a first deceleration execution step (S53) is performed to control the electronic proportional control valve (16) that adjusts the angle of the swash plate (SP) in the hydraulic transmission according to the first mode to decelerate the work vehicle; and
A second deceleration execution step (S55) for controlling the electronic proportional control valve (16) according to a second mode different from the first mode to decelerate the work vehicle when a pressure is input to the deceleration lever (13) after the first deceleration execution step (S53);
Control method of a hydrostatic transmission for a work vehicle.
In Article 8,
A second judgment step (S54) for judging whether a pressure is input to the deceleration lever (13) between the first deceleration execution step (S53) and the second deceleration execution step (S55); further comprising:
Control method of a hydrostatic transmission for a work vehicle.
In Article 8,
The above first mode is a mode in which deceleration is performed by elastic driving with the pressure removed from the accelerator lever (11).
The above second mode is a mode in which the deceleration is controlled so that the deceleration amount per hour is larger when the displacement of the deceleration lever (13) is large than when the displacement of the deceleration lever (13) is small.
Control method of a hydrostatic transmission for a work vehicle.

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