JP2021188669A - Vehicle for work - Google Patents

Abstract

To enable constant speed traveling and prevent deterioration in workability of a work device even when a speed at the time of constant speed traveling is set low.SOLUTION: A vehicle 1 for work includes, in a pilot oil passage 24, a proportional solenoid valve 44 for setting a pilot hydraulic pressure on an upstream side of a remote control valve 38, and a selector valve 46 for branching a flow passage between the proportional solenoid valve 44 and the remote control valve 38. The branch oil passage 32 branched by the selector valve 46 is connected to the pilot oil passage 24 through a shuttle valve 48 between the remote control valve 38 and a travel hydraulic pump 26. A control device 40, when a constant speed travel switch 80 is turned on, opens the selector valve 46 to apply the pilot hydraulic oil to the travel hydraulic pump 26 through the branch oil passage 32, and by setting an opening of the proportional solenoid valve 44 according to a set speed set by an adjusting switch 82, sets the pilot hydraulic pressure and performs control for travelling at a desired constant speed.SELECTED DRAWING: Figure 4

Description

The present invention relates to a work vehicle provided with a traveling hydraulic pump and a traveling device driven by a traveling hydraulic motor and capable of constant speed traveling.

Conventionally, an HST (Hydraulic Static Transmission), which is a drive mechanism including a traveling hydraulic pump and a traveling hydraulic motor, has been known. A crawler loader (truck loader) is known as an example of a work vehicle that drives a traveling device (for example, a crawler) by this HST (see Patent Document 1: Japanese Patent Application Laid-Open No. 2020-038002).

Japanese Unexamined Patent Publication No. 2020-038002

In the conventional work vehicle exemplified in Patent Document 1, it is assumed that the work involves running, that is, the work is carried out by hydraulically driving a work device (for example, a concrete cutter or the like) at the same time while running. ing. Therefore, if the operator can travel at a constant speed even if he / she releases his / her hand from the travel lever (hereinafter, simply referred to as “constant speed travel”), he / she can concentrate on the operation of the work device, which is safe and efficient. Work can be done in a targeted manner.

Here, in a work vehicle in which a drive mechanism (HST) is driven by an engine, a configuration is often used in which a set speed during constant speed traveling is adjusted by increasing or decreasing the engine speed. In such a configuration, if the constant speed running speed is set to a low speed, the engine speed decreases and the service hydraulic pressure supplied to the work equipment decreases, so that the workability of the work equipment deteriorates. Problems arise.

The present invention has been made in view of the above circumstances, and is a work vehicle capable of traveling at a constant speed and preventing deterioration of the workability of the work apparatus when the speed at the time of constant speed travel is set to a low speed. The purpose is to realize it.

The present invention solves the above-mentioned problems by means of solutions as described below.

The working vehicle according to the present invention includes a drive source, a traveling hydraulic pump and a pilot hydraulic pump driven by the drive source, a traveling hydraulic motor driven by pressure oil supplied from the traveling hydraulic pump, and a vehicle body. A pair of traveling devices provided on the left and right and driven by the traveling hydraulic motor, a pilot oil passage that communicates from the pilot hydraulic pump to the traveling hydraulic pump, and a control room on which an operator rides and performs a traveling operation. A control device for controlling the operation of the traveling device is provided, and a traveling lever, a constant-speed traveling switch for performing constant-speed traveling, and an adjustment switch for adjusting the speed during constant-speed traveling are provided in the control room. The pilot oil passage is provided with a remote control valve whose opening is set according to the operation amount of the traveling lever, and a proportional solenoid valve that sets the pilot hydraulic pressure at a position upstream of the remote control valve. A switching valve for branching the flow path is provided at a position between the proportional solenoid valve and the remote control valve, and the branch oil passage branched by the switching valve is the remote control valve and the traveling hydraulic pump. It is connected to the pilot oil passage at a position between and via a shuttle valve, and the control device opens the changeover valve when the constant speed traveling switch is turned on. Controls the application of the pilot hydraulic pressure to the traveling hydraulic pump through the branch oil passage, and sets the opening degree of the proportional solenoid valve according to the set speed set by the adjustment switch to control the pilot hydraulic pressure. It is a requirement to set and control to run at a constant speed at a desired speed.

According to the work vehicle according to the present invention, the constant speed traveling function can be realized, and when the constant speed traveling speed is set to a low speed, it is possible to prevent the workability of the work apparatus from deteriorating.

It is a perspective view which shows the example of the work vehicle which concerns on embodiment of this invention. It is a perspective view which shows the structural example of the cockpit part of the work vehicle shown in FIG. It is explanatory drawing which shows the display example of the cluster of the work vehicle shown in FIG. It is a schematic diagram of the hydraulic circuit system of the work vehicle shown in FIG. It is a flowchart which shows the example of the running control of the work vehicle shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view (a perspective view from above the rear portion) showing an example of the work vehicle 1 according to the present embodiment. Further, FIG. 2 is a perspective view showing an example of the internal configuration of the cockpit 16 of the work vehicle 1. In all the drawings for explaining the embodiment, the members having the same function may be designated by the same reference numerals, and the repeated description thereof may be omitted.

First, the overall configuration of the work vehicle 1 will be described. Here, a crawler loader traveling with a crawler will be described as an example, but the present invention is not limited thereto.

As shown in FIG. 1, the work vehicle 1 houses a traveling device 12 in the lower left and right sides, a working device 14 in the front part, a cockpit 16 in the central part, an engine 20 and the like in the rear part of the vehicle body 10. It is configured to include an engine room 18 to be mounted, and an arm post 52 to which an arm 54 for operating a working device 14 is attached. As an example, the traveling device 12 is configured to include a pair of left and right crawlers (endless crawler bands) 22. However, the present invention is not limited to this, and a configuration in which the vehicle travels with a pair of left and right tires (referred to as “skid steer loader”) may be used (not shown).

First, the working device 14 includes a pair of left and right arms 54 swingably pivotally connected to the arm post 52, and a bracket 62 swingably pivoted vertically to the tip of the arm 54. It is configured to include an attachment 64 that is detachably attached to the bracket 62. Here, a pair of left and right arm cylinders 56 are provided straddling the arm post 52 and the arm 54, and a pair of left and right attachment cylinders (commonly known as "bucket cylinders") are provided straddling the bracket 62 and the arm 54. (Not shown).

According to this configuration, the arm 54 can be swung up and down with respect to the vehicle body 10 by expanding and contracting the arm cylinder 56. Further, by expanding and contracting the attachment cylinder, the bracket 62, that is, the attached attachment 64 can be oscillated up and down with respect to the arm 54.

In the present embodiment, a configuration including a bucket as the attachment 64 is given as an example. However, the present invention is not limited to this configuration, and the attachment 64 is appropriately selected and attached according to the work application. As another example, a hydraulically driven attachment such as a concrete cutter or a trencher can be attached (not shown). The attachment 64 is configured to be replaced by itself or as a set with the bracket 62. Alternatively, there is also a configuration in which a bracket and a bucket are integrated (not shown). The work vehicle 1 is provided with a service oil passage for supplying hydraulic oil to the hydraulically driven attachment (not shown).

Next, as shown in FIG. 2, the cockpit 16 includes a seat 70 on which an operator (operator) is boarded and seated, a traveling lever 72 for operating the traveling device 12 and the like (as an example). , The lever on the left side is used as the traveling lever, but the lever is not limited to this, and the lever on the right side or the levers on both the left and right sides can be used as the traveling lever). Further, it is provided with various operation switches and the like for operating the operation of each mechanism, and these are arranged on the operation panel 74 and the like. A cluster 76 for displaying vehicle information may be provided, and the cluster 76 may be configured to display an operation switch for operation.

The traveling of the work vehicle 1 is performed by the operator sitting on the seat 70 and operating the traveling lever 72. That is, according to the operation of the traveling lever 72, the left and right traveling devices 12 are driven to travel the vehicle body 10 in the forward direction and the reverse direction, or the traveling direction is changed by changing the driving speeds on the left and right. , It is possible to change the direction by stopping one of the left and right or changing the driving direction on the left and right.

In the present embodiment, the control room 16 is provided with a constant speed traveling switch 80 for performing constant speed traveling and an adjusting switch 82 for adjusting the speed during constant speed traveling. By turning on the constant speed travel switch 80, constant speed travel becomes possible. At this time, the speed of constant speed traveling can be adjusted by the adjustment switch 82. Therefore, it is possible to realize a usage mode in which work is performed by the work device 14 while traveling at a constant speed. The details of the system configuration for realizing constant speed running will be described later.

The constant speed traveling switch 80 is a switch for switching ON / OFF of constant speed traveling, and as an example, it is configured by a push type switch and is arranged on the traveling lever 72 (see FIG. 2). As another example, it may be configured to be arranged on the operation panel 74. A toggle type switch or the like may be used instead of the push type switch. Alternatively, it may be configured by a touch switch displayed on the cluster 76. On the other hand, the adjustment switch 82 is a switch that variably adjusts the speed during constant speed traveling within a predetermined range (for example, 0.15 km / h to 5.0 km / h), and as an example, a push type switch (UP / It is composed of two systems of DOWN) and is arranged on the traveling lever 72 (see FIG. 2). As another example, it may be configured to be arranged on the operation panel 74. Instead of the push type switch, a slide type switch, a rotary type switch, or the like may be used. Alternatively, it may be configured by a touch switch displayed on the cluster 76.

FIG. 3 shows an example of a screen in which the constant speed traveling switch 80 and the adjustment switch 82 are configured to be displayed on the cluster 76. When the Fn (function) switch of FIG. 3 (a) is touched, the lower display transitions to FIG. 3 (b). In FIG. 3B, the constant speed travel is switched between “ON” and “OFF” each time the constant speed travel switch 80 is touched. Further, in FIG. 3A, each time the UP switch (upward arrow switch) of the adjustment switch 82 is touched, the set speed of constant speed running gradually increases to the high speed side within the set range, and the adjustment switch 82 Each time the DOWN switch (switch with a downward arrow) is touched, the set speed of constant speed running is gradually lowered to the low speed side within the set range. As a modification, instead of the touch type switch displayed on the screen, a push type switch operated by pressing may be provided on the outer edge portion around the screen (not shown).

Next, the engine room 18 is provided in the rear part of the vehicle body 10 (rear position of the cockpit 16), and the engine 20 as a drive source, the equipment described later, and the like are mounted therein in a form accommodated therein. .. As an example, the engine 20 uses, but is not limited to, a water-cooled diesel engine. The traveling device 12 and the working device 14 described above are configured to be driven by receiving hydraulic oil sent from each hydraulic pump driven by the engine 20. The drive source may be configured to use a battery instead of the engine 20 or together with the engine 20 (not shown).

Here, FIG. 4 shows a schematic diagram of the hydraulic circuit system of the work vehicle 1 according to the present embodiment. However, FIG. 4 shows only the main parts related to the present embodiment.

The work vehicle 1 according to the present embodiment is configured to travel with an HST (Hydraulic Static Transmission). More specifically, as an example of the configuration for driving the traveling device 12, from the variable displacement type traveling hydraulic pump 26 (26A, 26B) driven by the engine 20 as a driving source, and the traveling hydraulic pump 26 (26A, 26B). It is equipped with a traveling hydraulic motor 30 (30A, 30B) driven by the supplied hydraulic oil. Further, it is provided with a pilot hydraulic pump 28 driven by the engine 20 to generate pilot hydraulic pressure, and a pilot oil passage 24 that communicates from the pilot hydraulic pump 28 to the traveling hydraulic pumps 26 (26A, 26B) and applies pilot hydraulic pressure. .. Further, it includes a control device 40 that controls the operation of the traveling device 12 and the like of the work vehicle 1, and an engine control unit (ECU) 42 that controls the engine 20 based on a command from the control device 40. Since the hydraulic mechanism and the like for operating the working device 14 are the same as those of a known vehicle, detailed description thereof will be omitted.

Here, the pilot oil passage 24 is provided with remote control valves 38 (38A, 38B) whose opening degree is set according to the operation amount of the traveling lever 72. The remote control valve 38 (38A, 38B) is a traveling hydraulic pump by changing the pilot hydraulic pressure acting on the traveling hydraulic pump 26 (26A, 26B) during normal traveling (state in which the constant speed traveling switch 80 is OFF). It controls the direction and flow rate of the pressure oil supplied from the 26 (26A, 26B) to the traveling hydraulic motor 30 (30A, 30B) via the oil passage 36 (36A or 36C, 36B or 36D). Further, in the pilot oil passage 24, the pressure value of the pilot hydraulic pressure is detected and output to the control device 40 at the position between the remote control valve 38 (38A, 38B) and the traveling hydraulic pump 26 (26A, 26B). Sensors 34 (34FL, 34RL, 34FR, 34RR) are provided.

According to such a configuration, the remote control valve 38 (38A, 38B) is controlled to open and close by the operator operating the traveling lever 72, and the pilot hydraulic pressure acting on the traveling hydraulic pump 26 (26A, 26B) is set. .. Further, the traveling hydraulic motor 30 (30A, 30B) is driven by the traveling hydraulic pump 26 (26A, 26B) whose output is variable according to the pilot hydraulic pressure, and the crawler 22 is operated to drive or turn the vehicle. Will be done.

In the present embodiment, as the traveling hydraulic motor 30, the first traveling hydraulic motor 30A corresponding to one (for example, left) crawler 22 and the second traveling hydraulic motor 30B corresponding to the other (for example, right) crawler 22 are used. There are two of them. Therefore, as the pilot hydraulic pressure, the first pilot hydraulic pressure for controlling the first traveling hydraulic motor 30A and the second pilot hydraulic pressure for controlling the second traveling hydraulic motor 30B are generated.

As described above, the pressure sensor 34 is configured to detect the pressure value of the pilot hydraulic pressure that increases or decreases according to the operation amount of the traveling lever 72 and output it as a signal to the control device 40. In the present embodiment, as the pressure sensor 34, the first forward sensor 34FL and the first traveling hydraulic motor 30A detect and output the pressure value of the first pilot hydraulic pressure when the first traveling hydraulic motor 30A rotates in the forward direction. Is provided with a first reverse sensor 34RL that detects and outputs a pressure value of the first pilot hydraulic pressure when the vehicle rotates in the reverse direction. Further, the second forward sensor 34FR that detects and outputs the pressure value of the second pilot hydraulic pressure when the second traveling hydraulic motor 30B rotates in the forward direction, and the second traveling hydraulic motor 30B when the second traveling hydraulic motor 30B rotates in the reverse direction. It is equipped with a second reverse sensor 34RR that detects and outputs the pressure value of the pilot hydraulic pressure.

Here, as a characteristic feature of the present embodiment, a proportional solenoid valve 44 for setting the pilot hydraulic pressure at a position upstream of the remote control valve 38 is provided in the pilot oil passage 24. Further, a switching valve 46 for branching the pilot oil passage 24 is provided at a position between the proportional solenoid valve 44 and the remote control valve 38. The branch oil passage 32 branched by the switching valve 46 is connected to the pilot oil passage 24 via the shuttle valve 48 at a position between the remote control valve 38 and the traveling hydraulic pump 26. The pressure sensors 34 (34FL, 34RL, 34FR, 34RR) described above are located downstream of the shuttle valve 48 in the pilot oil passage 24 for detection, that is, the shuttle valve 48 and the traveling hydraulic pump 26. It is provided at the position between them.

With such a configuration, the control method unique to the present embodiment, which will be described in detail below, can be realized, so that the above-mentioned problems can be solved.

Specifically, the flowchart of FIG. 5 shows an outline of the operation control of the traveling device 12 (here, the control related to constant speed traveling) performed by the control device 40 according to the present embodiment. First, the control device 40 carries out a step of determining a state in which the constant speed traveling switch 80 is turned “ON” (step S1).

Next, when the control device 40 determines that the constant speed travel switch 80 is in the "ON" state, the control device 40 outputs a constant speed travel execution command in the control circuit and opens the switching valve 46 in the "open" state. (Step S2). That is, the branch oil passage 32 that branches from the pilot oil passage 24 is opened. Therefore, the pilot hydraulic pressure is applied to the traveling hydraulic pump 26 through the branch oil passage 32. As a result, the work vehicle 1 starts running at a constant speed at a speed corresponding to the pilot hydraulic pressure.

At this time, the control device 40 carries out a step of setting the opening degree of the proportional solenoid valve 44 according to the set speed set by the adjustment switch 82 (step S3). That is, the pilot hydraulic pressure is set according to the opening degree of the proportional solenoid valve 44, and constant speed traveling can be performed at a desired speed set by the pilot hydraulic pressure. Therefore, the operator can variably set the speed of the work vehicle 1 during constant speed traveling by operating the adjustment switch 82 to adjust the set speed. As an example, it is possible to set the speed in the range of 0.15 km / h to 5.0 km / h. However, it is not limited to this range.

In the state of constant speed traveling, the control device 40 measures the pressure value of the pilot hydraulic pressure applied to the traveling hydraulic pump 26 by the pressure sensor 34, and feeds back to correct the opening degree of the proportional solenoid valve 44. Control is performed (step S4). As a result, the speed of the work vehicle 1 during constant speed traveling can be kept constant with high accuracy.

Here, the control device 40 is characterized in that when the adjustment switch 82 is operated, the control device 40 performs control that does not change the rotation speed of the engine 20 which is a drive source. Conventionally, when trying to change the traveling speed of a work vehicle, it has been common to control to change the rotation speed of the engine. That is, the control is such that the engine rotation speed is increased when the traveling speed is to be increased, and the engine rotation speed is decreased when the traveling speed is to be decreased. However, research has revealed that such control causes the above-mentioned problems during constant-speed driving. That is, as the set speed during constant speed running becomes lower (particularly, in the so-called very low speed region of about 0.15 km / h to 3.0 km / h), the engine speed decreases and the service hydraulic pressure supplied to the work equipment. This is a problem that the workability of the work device is deteriorated because the work device is deteriorated.

In response to this problem, in the present embodiment, as described above, when the operator operates the adjustment switch 82 to set the speed during constant speed traveling, the opening degree of the proportional solenoid valve 44 is changed. Moreover, the control is performed so as not to change the rotation speed of the engine 20. Therefore, in particular, even if the speed during constant speed traveling is set to a low speed (slow speed), the rotation speed of the engine 20 does not decrease and the service hydraulic pressure does not decrease, so that the workability of the work device 14 deteriorates. Can be prevented.

Further, in the present embodiment, in addition to the configuration in which the opening degree of the proportional solenoid valve 44 is changed to set the speed during constant speed traveling, the position on the upstream side of the remote control valve 38 in the pilot oil pressure passage 24 A switching valve 46 is provided in the vehicle, and the pilot hydraulic pressure is applied to the traveling hydraulic pump 26 through the branch oil passage 32 branched from the switching valve 46, so that the operator carelessly accelerates the traveling lever 72 during constant speed traveling. Since the pilot hydraulic pressure does not change even if the valve is operated in the same way, safe driving without sudden speed change can be realized.

On the other hand, when the traveling lever 72 is operated to the reverse position (forward to reverse or reverse to forward) during constant speed traveling, the control device 40 detects the operation (step S5) and the constant speed traveling switch. At the same time as carrying out the step of turning 80 to "OFF" (that is, the step of canceling the execution command of constant speed running in the control circuit) (step S6), the step of turning the switching valve 46 into the "closed" state is carried out. (Step S8). As a result, the constant speed running of the work vehicle 1 is completed. In this way, by realizing a configuration in which the operator simply operates the traveling lever 72 to the reverse position to end the constant speed traveling, it is possible to quickly release the traveling lever 72 in an emergency or the like, and it is possible to improve safety. Further, since the traveling speed at the time when the constant speed traveling is canceled becomes the speed set by the proportional solenoid valve 44, the sudden change in the speed does not occur, and further safety can be ensured. In the present embodiment, the state in which the traveling lever 72 is operated to the reverse position is determined based on the change in the pressure value detected by the pressure sensor 34.

In order to end the constant speed traveling of the work vehicle 1, as described above, the operation of the traveling lever 72 to the reverse position during the constant speed traveling enables the termination. Alternatively, the step of directly turning off the constant speed travel switch 80 (that is, the step of canceling the execution command of constant speed travel in the control circuit) is performed (step S7), and the switching valve 46 is "closed". The step of making the state is carried out (step S8). This operation also ends the constant speed running of the work vehicle 1.

As described above, according to the work vehicle according to the present invention, it is possible to perform constant speed traveling at a speed arbitrarily set by the operator (for example, 0.15 km / h to 5.0 km / h). Become. Further, when the work is performed by the work device while running at a constant speed, it is possible to prevent the workability of the work device from deteriorating even when the set speed at the time of constant speed running is set to a low speed.

The present invention is not limited to the embodiments described above, and can be variously modified without departing from the present invention. In particular, the explanation has been given by taking a crawler loader as an example of a work vehicle, but the description is not limited to this, and for example, other work vehicles such as a skid steer loader, a crawler carrier, and a power shovel are also used. It goes without saying that it can be applied in the same way.

1 Work vehicle 10 Body 12 Traveling device 14 Working device 16 Control room 20 Engine 22 Crawler 24 Pilot oil passage 26, 26A, 26B Traveling hydraulic pump 28 Pilot hydraulic pump 30, 30A, 30B Traveling hydraulic motor 32 Branch oil passage 34, 34FL , 34FR, 34RL, 34RR Pressure sensor 38, 38A, 38B Remote control valve 40 Control device 42 Engine control unit (ECU)
44 Proportional solenoid valve 46 Switching valve 48 Shuttle valve 54 Arm 64 Attachment 72 Traveling lever 80 Constant speed traveling switch 82 Adjustment switch

Claims (5)

With the drive source
The traveling hydraulic pump and the pilot hydraulic pump driven by the drive source,
A traveling hydraulic motor driven by the pressure oil supplied from the traveling hydraulic pump,
A pair of traveling devices provided on the left and right sides of the vehicle body and driven by the traveling hydraulic motor,
A pilot oil passage that communicates from the pilot hydraulic pump to the traveling hydraulic pump,
The cockpit where workers board and operate the vehicle,
A control device for controlling the operation of the traveling device is provided.
The cockpit is provided with a traveling lever, a constant-speed traveling switch for performing constant-speed traveling, and an adjusting switch for adjusting the speed during constant-speed traveling.
In the pilot oil passage,
A remote control valve whose opening is set according to the amount of operation of the traveling lever, and
A proportional solenoid valve that sets the pilot hydraulic pressure at a position upstream of the remote control valve,
A switching valve for branching the flow path is provided at a position between the proportional solenoid valve and the remote control valve.
The branch oil passage branched by the switching valve is connected to the pilot oil passage at a position between the remote control valve and the traveling hydraulic pump via a shuttle valve.
The control device controls to apply the pilot hydraulic pressure to the traveling hydraulic pump through the branch oil passage by opening the switching valve when the constant speed traveling switch is turned on. A work vehicle characterized in that the pilot hydraulic pressure is set by setting the opening degree of the proportional solenoid valve according to the set speed set by the adjustment switch, and control is performed to run at a constant speed at a desired speed. .. The drive source is an engine.
The work vehicle according to claim 1, wherein the control device performs control that does not change the rotation speed of the engine when the adjustment switch is operated. The work vehicle according to claim 1 or 2, wherein the pilot oil passage is provided with a pressure sensor for detecting the pressure value of the pilot hydraulic pressure at a position downstream of the shuttle valve. .. When the traveling lever is operated to the reverse position during constant speed traveling with the constant speed traveling switch turned on, the control device changes the operating state based on the change in the pressure value of the pressure sensor. The work vehicle according to claim 3, further comprising controlling the determination, turning off the constant speed traveling switch, and closing the changeover valve. The claim is characterized in that the adjustment switch is composed of a push type switch, a slide type switch, or a rotary switch provided on the traveling lever or the operation panel, or a touch type switch provided on the cluster. The work vehicle according to any one of 1 to 4.

Images