JP6456752B2 - Method for controlling hydraulic system of work machine, hydraulic system of work machine, and work machine - Google Patents

Description

  The present invention relates to a method for controlling a hydraulic system for a work machine such as a skid steer loader or a compact truck loader, a hydraulic system for the work machine, and a work machine.

2. Description of the Related Art Conventionally, a hydraulic system that performs a shift using a variable displacement hydraulic motor in a working machine such as a skid steer loader or a compact truck loader is known (see Patent Document 1).
The hydraulic system disclosed in Patent Document 1 is a system that performs a shift using a swash plate type variable displacement axial motor (HST motor). Specifically, pressure oil is supplied to the swash plate switching cylinder via a hydraulic switching valve, and the angle of the swash plate of the HST motor is changed by the operation of the swash plate switching cylinder, so that low speed (first speed) and high speed (second speed) And are configured to be switched.

JP 2013-36276 A

However, in the conventional hydraulic system as disclosed in Patent Document 1, there is a case where a response delay occurs between the time when the speed change operation is performed and the time when the speed is actually changed. In particular, at low temperatures, the viscosity of the oil increases, and shifting may not proceed smoothly.
The present invention has been made in order to solve the above-described problems of the prior art. For example, a working machine capable of appropriately switching a direction switching valve even in various situations such as at low temperatures. It is an object to provide a hydraulic system control method, a working machine hydraulic system, and a working machine.

The technical means taken by the present invention to solve the technical problem is as follows.
The work system hydraulic system control method is such that the pilot pressure applied to the hydraulic switching valve that can be switched to a plurality of switching positions in accordance with the pilot pressure that is the pilot oil pressure can be changed by changing the opening degree. Detecting that the valve has been switched to a first position having a predetermined opening or a second position having an opening larger than a predetermined opening corresponding to the first position; and Measuring a first elapsed time that is an elapsed time at the second position; determining whether the measured first elapsed time has reached a predetermined first predetermined time; Determining whether the pilot pressure has reached a predetermined pressure, and if the pilot pressure has reached a predetermined pressure before the first elapsed time reaches the first predetermined time, Holding the second position of the valve; and if the pilot pressure has not reached a predetermined pressure before the first elapsed time reaches the first predetermined time, the directional control valve is moved from the second position to the second position. A step of switching to one position, a step of detecting that the direction switching valve is held at the second position, a holding of the direction switching valve at the second position is detected, and the pilot pressure is The step of measuring a second elapsed time, which is the time when the pilot pressure has dropped below the predetermined pressure when the pressure drops below the predetermined pressure, and the measured second elapsed time are different from the first predetermined time. Determining whether or not a second predetermined time has been reached, and switching the direction switching valve from the second position to the first position if the second elapsed time reaches the second predetermined time. Includes a step, a.

  Further, according to the control method of the hydraulic system of the work implement, the pilot pressure added to the hydraulic switching valve that can be switched to a plurality of switching positions according to the pilot pressure that is the pressure of the pilot oil can be changed by setting the opening. A step in which the direction switching valve detects switching between a first position having a predetermined opening degree and a second position having an opening degree larger than a predetermined opening degree corresponding to the first position; A step of detecting a change rate of the pilot pressure, a step of determining whether to hold the directional control valve at the second position based on the rate of change of the pilot pressure, and the change rate is determined from a predetermined determination value The direction switching valve is switched from the second position to the first position.

Here, preferably, the second predetermined time is a time based on a temperature of the pilot oil, and the first predetermined time is longer than the second predetermined time.
Further preferably, after the directional control valve is once held in the second position, the second predetermined time is used instead of the first predetermined time.
In addition, preferably, the step of switching the direction switching valve from the second position to the first position is performed at least once by measuring the first elapsed time that is the elapsed time of the direction switching valve at the second position. After being performed, when switching from the first position to the second position is performed.

  The working machine hydraulic system includes a hydraulic pump that supplies pilot oil, a hydraulic switching valve that can be switched to a plurality of switching positions in accordance with a pilot pressure that is the pressure of the pilot oil, and the hydraulic switching valve that is added to the hydraulic switching valve. The direction switching valve capable of changing the pilot pressure by setting the opening, and the direction switching valve are at a first opening which is a predetermined opening or an opening larger than a predetermined opening corresponding to the first position. A switching detection unit that detects that the switch has been switched to the second position; a first measurement unit that measures a first elapsed time that is an elapsed time of the directional switching valve at the second position; and the measured first A first time determination unit that determines whether or not an elapsed time has reached a first predetermined time; a pressure determination unit that determines whether or not the pilot pressure has reached a predetermined pressure; , The first elapsed time before If the pilot pressure has reached a predetermined pressure before reaching the first predetermined time, a holding portion for holding the second position of the direction switching valve, and before the first elapsed time reaches the first predetermined time If the pilot pressure does not reach a predetermined pressure, a first switching unit that switches the direction switching valve from the second position to the first position, and detects that the direction switching valve is held at the second position. When the holding of the directional control valve at the second position is detected and the pilot pressure is lower than the predetermined pressure, the pilot pressure is reduced to less than the predetermined pressure. A second measuring unit that measures a certain second elapsed time; and a second time determining unit that determines whether or not the measured second elapsed time has reached a second predetermined time different from the first predetermined time; , At the second lapse If There reaches the second predetermined time, and a second switching unit for switching to the first position the directional control valve from said second position.

  A working machine provided with the hydraulic system, wherein the working machine includes a cabin mounted on the machine body, traveling devices disposed on the right and left sides of the machine body, and a boom provided on a side of the cabin. And a work tool mounted on the boom.

  According to the present invention, the direction switching valve can be appropriately switched even in various situations such as at low temperatures.

It is a figure which shows the hydraulic circuit of the hydraulic system which concerns on embodiment of this invention. It is a figure which shows the flow of the control method of the hydraulic system which concerns on 1st Embodiment. It is a figure which shows the graph of the time series change of the pilot pressure in the control method of the hydraulic system which concerns on 1st Embodiment. It is a figure which shows the graph of another time series change of the pilot pressure in the control method of the hydraulic system which concerns on 1st Embodiment. It is a figure which shows the flow of the control method of the hydraulic system which concerns on the modification of 1st Embodiment. It is a figure which shows the flow of the control method of the hydraulic system which concerns on 2nd Embodiment. It is a figure which shows the hydraulic circuit of the hydraulic system which concerns on 3rd Embodiment. It is a figure which shows the side surface of the track loader which is an example of a working machine. It is a figure which shows a part of side surface of the track loader which raised the cabin.

A working machine hydraulic system control method, a working machine hydraulic system, and a working machine equipped with the hydraulic system according to a preferred embodiment of the present invention will be described below with reference to the drawings as appropriate.
[First embodiment]
First, with reference to FIG.8 and FIG.9, the whole structure of the working machine 1 by embodiment of this invention is demonstrated.

  8 and 9, a truck loader is shown as an example of the working machine 1 according to the present embodiment. However, the working machine according to the present embodiment is not limited to a truck loader, and for example, a tractor, a skid steer loader, a compact truck loader. , Backhoe or the like. In the present embodiment, the front side (direction indicated by the arrow F shown in FIG. 8) of the driver seated on the driver's seat of the work machine 1 is forward and the rear side of the driver (direction indicated by the arrow R shown in FIG. 8). Will be described as the rear, the left side of the driver (front side toward the page of FIG. 8) as the left side, and the right side of the driver (back side toward the page of FIG. 8) as the right side.

  As shown in FIGS. 8 and 9, the work machine 1 according to the present embodiment includes a machine body frame (machine body) 2, a work device 3 attached to the machine body 2, and a traveling device 4 that supports the machine body 2. ing. A cabin 5 is mounted on the upper portion of the airframe 2 and on the front portion of the airframe 2. The rear portion of the cabin 5 is supported by the support bracket 11 of the airframe 2 and can swing around the support shaft 12. The front part of the cabin 5 can be supported by the front part of the airframe 2.

A driver's seat 13 is provided in the cabin 5. A travel operation device 14 for operating the travel device 4 is disposed on one side (for example, the left side) of the driver seat 13.
The traveling device 4 is a crawler traveling device. The traveling device 4 is provided below the left side of the body 2 and below the right side of the body 2. The traveling device 4 can travel by the driving force of hydraulically driven traveling motors 21L and 21R (wheel motors).

  The work device 3 includes a pair of booms 22 including a left boom 22L and a right boom 22R, and a bucket 23 (work tool) attached to the tip of the boom 22. The left boom 22L is disposed on the left side of the body 2. The right boom 22 </ b> R is disposed on the right side of the airframe 2. The left boom 22L and the right boom 22R are connected to each other by a connecting body (not shown) provided between the left boom 22L and the right boom 22R. The left boom 22L and the right boom 22R are supported by a first lift link 24 and a second lift link 25, respectively. Between the base side of the left boom 22L and the right boom 22R and the rear lower part of the airframe 2, a lift cylinder 26 composed of a double-acting hydraulic cylinder is provided corresponding to the left boom 22L and the right boom 22R. By simultaneously extending and retracting the lift cylinder 26, the left boom 22L and the right boom 22R simultaneously swing up and down. A mounting bracket 27 is pivotally connected to the front ends of the left boom 22L and the right boom 22R so as to be rotatable about the horizontal axis, and the back side of the bucket 23 is attached to the mounting bracket 27.

A tilt cylinder 28 composed of a double-acting hydraulic cylinder is interposed between the mounting bracket 27 and the front end side middle portions of the left boom 22L and the right boom 22R in correspondence with the left boom 22L and the right boom 22R. ing. The bucket 23 swings (squeeze / dump operation) by the expansion and contraction of the tilt cylinder 28.
The bucket 23 is detachable from the mounting bracket 27. The mounting bracket 27 is configured such that if the bucket 23 is removed, various attachments (hydraulic drive working tools having a hydraulic actuator) can be attached, and various operations other than excavation (or other excavation operations) can be performed. Has been.

An engine 29 is provided on the rear side of the bottom wall 6 of the body (vehicle body) 2, and a fuel tank 30 and a hydraulic oil tank 31 are provided on the front side of the bottom wall 6 of the body 2.
A hydraulic drive device 32 that drives the traveling motors 21L and 21R is provided in front of the engine 29. Further, in front of the hydraulic drive device 32, first to third pumps P1, P2, and P3, which are hydraulic pumps, are provided. The machine body 2 is provided with a control valve 33 (hydraulic control device) for the working device 3.

Next, the hydraulic system of the work machine 1 according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a part of a hydraulic system that is a traveling hydraulic system of a work machine 1 according to the present embodiment.
The first to third pumps P 1, P 2, and P 3 that are hydraulic pumps are configured by constant displacement gear pumps that are driven by the power of the engine 29.

  The first pump P1 (main pump) is used to drive a hydraulic actuator of an attachment attached to the lift cylinder 26, the tilt cylinder 28 or the tip side of the boom 22. The second pump P2 (sub pump) is used to increase the flow rate of hydraulic oil supplied to the hydraulic actuator when the hydraulic actuator of the hydraulic attachment attached to the tip side of the boom 22 requires a large capacity. used. The third pump P3 (pilot pump, charge pump) is mainly used to supply pilot oil pressure (pilot pressure) as a control signal.

As shown in FIG. 1, a discharge oil passage 100a through which discharge oil (pilot oil) discharged from the third pump P3 flows is connected to the discharge port of the third pump P3. In FIG. 1, the oil passage connected to the first pump P1 and the second pump P2 is omitted.
Connected to the end of the discharge oil passage 100a of the third pump P3 is a second speed switching valve 64 which is a directional switching valve capable of changing a pilot pressure applied to a hydraulic switching valve described later by setting the opening. A relief valve 52 that sets the maximum pressure of the third pump P3 is connected to the downstream side of the discharge oil passage 100a.

  The hydraulic system of the work machine 1 according to the present embodiment includes an HST motor 257 and a hydraulic switching valve 263. The HST motor 257 is constituted by, for example, a cam motor (radial piston motor). The HST motor 257 is a variable capacity type that can change the capacity (motor capacity) during operation, and the rotation and torque of the output shaft can be changed by changing the motor capacity. Specifically, the HST motor 257 includes a first motor 257A and a second motor 257B. By supplying hydraulic oil to both the first motor 257A and the second motor 257B, the motor capacity is increased, and the HST motor 257 is at the first speed. Further, by supplying hydraulic oil to either the first motor 257A or the second motor 257B, the motor capacity is reduced, and the HST motor 257 is in the second speed.

  The hydraulic switching valve 263 is a hydraulic switching valve that can be switched to a plurality of switching positions according to the pilot pressure that is the pressure of the pilot oil, and is a valve that switches the HST motor 257 to the first speed or the second speed. This is a three-position switching valve that can be switched to three positions: a position 63a, a second switching position 63b, and a neutral position 63c. Specifically, when the pressure of the pilot oil acting on the pressure receiving portion 264 of the hydraulic switching valve 263 is less than a preset pressure that is a predetermined pressure, the hydraulic switching valve 263 is held at the first switching position 63a by a spring. Is done. When the hydraulic switching valve 263 is in the first switching position 63a, hydraulic fluid is supplied to both the first motor 257A and the second motor 257B, and the HST motor 257 is in the first speed. When the pressure of the pilot oil acting on the pressure receiving portion 264 of the hydraulic switching valve 263 is equal to or higher than the set pressure, the hydraulic switching valve 263 is switched to the second switching position 63b through the neutral position 63c. When the hydraulic switching valve 263 is at the second switching position 63b, the hydraulic oil is supplied only to the first motor 257A, and the HST motor 257 is in the second speed.

The hydraulic switching valve 263 and the second speed switching valve (direction switching valve) 64 are connected by a second oil passage 100x. A second throttle 81 is provided between the hydraulic switching valve 263 and the second speed switching valve 64 in the second oil passage 100x.
When the second speed switching valve 64 is switched to the second position 64b, pilot pressure is applied to the pressure receiving portion 264 of the hydraulic switching valve 263. When the pilot pressure applied to the pressure receiving unit 264 reaches the set pressure, the hydraulic switching valve 263 switches from the first switching position 63a to the second switching position 63b via the neutral position 63c.

  The second throttle 81 restricts the amount of pilot oil flowing through the second oil passage 100x, and the second throttle 81 reduces the pilot pressure from the second speed switching valve 64 toward the hydraulic switching valve 263. In this way, the second throttle 81 reduces the change speed of the pilot pressure applied to the hydraulic pressure switching valve 263, so that the switching speed of the hydraulic pressure switching valve 263 can be reduced. As a result, it is possible to avoid abrupt switching of the hydraulic pressure switching valve 263, and to mitigate the impact when the HST motor 257 is switched from the first speed to the second speed.

  The second speed switching valve 64 is a two-position switching valve that can be switched between a first position 64a and a second position 64b by excitation. When the second speed switching valve (direction switching valve) 64 is switched to the second position 64b, the discharge oil passage 100a of the third pump P3 (sometimes referred to as the first oil passage 100a) via the second oil passage 100x. And the hydraulic switching valve 263 are connected. Then, the pilot oil discharged from the third pump P3 acts on the pressure receiving portion 264 of the hydraulic pressure switching valve 263 through the second speed switching valve 64 and the second oil passage 100x. The hydraulic switching valve 263 is switched to the second switching position 63b by the pilot oil pressure (pilot pressure) from the second speed switching valve 64 to the hydraulic switching valve 263. On the other hand, when switched to the first position 64a, the hydraulic oil tank 31 and the hydraulic pressure switching valve 263 are connected, and the pilot oil acting on the hydraulic pressure switching valve 263 is discharged to the hydraulic oil tank 31. As a result, the pilot pressure in the second oil passage 100x decreases, and the hydraulic switching valve 263 switches to the first switching position 63a.

As described above, in the present embodiment, the second speed switching valve (direction switching valve) 64 is controlled based on the pilot pressure in the second oil passage 100x.
As shown in FIG. 1, in the second oil passage 100x, a pressure detection unit 300 that detects a pilot pressure is connected between the pressure receiving unit 264 and the junction VX of the hydraulic switching valve 263. The pressure detection unit 300 includes a pressure gauge (pressure sensor). The pressure detection unit 300 is connected to a control unit 301 configured by a CPU (Central Processing Unit) or the like.

The control unit 301 controls the switching of the second speed switching valve 64 described above based on the operation member 302 connected to the control unit 301 and the pilot pressure detected by the pressure detection unit 300.
The operation member 302 is a switch for setting the first speed or the second speed of the HST motor 257 and instructs the switching of the traveling speed of the work machine 1. The operation member 302 is composed of, for example, a swingable seesaw type switch, a slide type switch that can slide, or a push type switch that can be pressed. The seesaw type switch can be set to the first speed by swinging to one side and to the second speed by swinging to the other side. The slide type switch can be set to the first speed by sliding to one side and to the second speed by sliding to the other side. In the push type switch, every time the push switch is pressed, the first speed and the second speed are switched.

Next, the control by the control unit 301 will be described in detail.
When the operation member 302 is operated and the HST motor 257 is operated to the first speed, the control unit 301 may be referred to as a command for setting the direction switching valve 64 to the first position 64a (hereinafter referred to as “first speed command”). ) Is output to the direction switching valve 64. When the direction switching valve 64 is set to the first position 64a by this first speed command, if the pilot pressure in the second oil passage 100x is less than the set value (less than the set pressure), the hydraulic switch valve 263 is moved to the first switch position. 63a, and the HST motor 257 is set to the first speed.

  In addition, when the operation member 302 is operated and the HST motor 257 is moved to the second speed, the control unit 301 may command the direction switching valve 64 to the second position 64b (hereinafter, referred to as a second speed command). ) Is output to the direction switching valve 64. When the direction switching valve 64 is set to the second position 64b by this second speed command, the discharge oil passage 100a of the third pump P3 and the hydraulic pressure switching valve 263 are connected via the second oil passage 100x. At this time, the pilot oil discharged from the third pump P3 acts on the pressure receiving portion 264 of the hydraulic pressure switching valve 263 through the second speed switching valve 64 and the second oil passage 100x.

  When the second speed switching valve (direction switching valve) 64 is switched to the second position 64b, the hydraulic pressure switching valve 263 is driven by the pilot oil pressure (pilot pressure) from the second speed switching valve 64 to the hydraulic pressure switching valve 263. The position is switched to the second switching position 63b. Under this condition, if the pilot pressure of the second oil passage 100x detected by the pressure detection unit 300 becomes equal to or higher than the set value (set pressure or higher), the hydraulic pressure switching valve 263 is set to the second switching position 63b and the HST motor 257 is set. Becomes 2nd gear.

  Furthermore, the control unit 301 is detected by the pressure detection unit 300 in a state in which a command to set the direction switching valve 64 to the second position 64b is output, that is, in a state in which a second speed command is output to the direction switching valve 64. If the pilot pressure exceeds a predetermined pressure and becomes less than the predetermined pressure (less than the set value), a first speed command is output to the direction switching valve 64. Specifically, after the control unit 301 outputs the second speed command, the pilot pressure in the second oil passage 100x rises above the set pressure, and then the control is performed when the pilot pressure in the second oil passage 100x falls below the set pressure. The unit 301 outputs a first speed command to the direction switching valve 64. As a result, the hydraulic switching valve 263 is set to the second switching position 63b when the pilot pressure exceeds a predetermined pressure, and is set to the first switching position 63a when the pilot pressure drops below the set pressure. Is done.

In addition, when the pilot pressure in the second oil passage 100x does not rise above the set pressure after the output of the 2nd speed command and the state below the set pressure continues for a predetermined time, the control unit 301 sends the 1st speed command to the direction switching valve 64. Is output. At this time, regardless of the state of the direction switching valve 64, the hydraulic switching valve 263 does not move from the first switching position 63a that is the position when the pilot pressure is less than the set pressure.
That is, the control unit 301 monitors the pilot pressure in the second oil passage 100x after outputting the second speed command. If the pilot pressure in the second oil passage 100x is equal to or higher than the set value, the hydraulic switching valve 263 is set to the second switching position 63b in accordance with the second speed command for the direction switching valve 64, and the HST motor 257 is in the second speed state. is there. However, when the pilot pressure in the second oil passage 100x is less than the set value, the control unit 301 outputs the second speed command and the direction switching valve 64 is set to the second position 64b, but the hydraulic pressure switching is performed. The valve 263 is not set to the second switching position 63b. At this time, since the hydraulic pressure switching valve 263 may be set to the neutral position 63c, the control unit 301 outputs the second speed command to the direction switching valve 64 and the pilot pressure in the second oil passage 100x is less than the set value. If it is, the output of the second speed command is stopped and the first speed command is output.

  Therefore, when the pilot pressure in the second oil passage 100x is reduced for some reason under the situation in which the control unit 301 is outputting the second speed command, the first speed command is output to the direction switching valve 64, so that the hydraulic pressure is increased. The switching valve 263 is prevented from being maintained at the neutral position 63c. For example, in a state where the control unit 301 is outputting the second speed command, the pilot in the second oil passage 100x is caused by a rapid decrease in the engine speed, a rapid use of the hitch cylinder, or an extremely high temperature of the hydraulic oil. When the pressure is temporarily lowered, it is possible to prevent an undesired switching to the neutral position 63c.

Hereinafter, the control method of the hydraulic system by the control unit 301 will be described in more detail with reference to FIGS.
The control unit 301 switches the second speed switching valve 64 that is a direction switching valve from the first speed (first position) that is a predetermined opening degree to the second speed (second position) that is an opening degree larger than the first speed. At the same time, based on the pilot pressure applied to the hydraulic pressure switching valve 263, it is determined whether to hold the second speed switching valve 64 at the second speed or to return from the second speed to the first speed, that is, to switch to the first speed. 64 switching is performed.

  The control unit 301 is operated by a computer program. Each of the switching detection unit 320, the first measurement unit 321, the first time determination unit 322, the pressure determination unit 323, the holding unit 324, and the first configuration each configured by a computer program. A switching unit 325, a position detection unit 326, a second measurement unit 327, a second time determination unit 328, and a second switching unit 329 are provided, and these operations are controlled based on a flowchart shown in FIG.

  When the operation member 302 is operated and the HST motor 257 is moved to the first speed, the control unit 301 outputs a first speed command to the direction switching valve 64 and sets the direction switching valve 64 to a predetermined opening degree. When the operation member 302 is operated to change the HST motor 257 to the second speed by switching to the first position 64a, a second speed command is output to the direction switching valve 64, and the direction switching valve 64 corresponds to the first position. It switches to the 2nd position 64b which is an opening larger than the predetermined opening.

  In the switching detection unit 320, the direction switching valve 64 is switched to the first position 64a having a predetermined opening or the second position 64b having an opening larger than the predetermined opening corresponding to the first position 64a. This is to detect whether the control unit 301 is outputting a first speed command or a second speed command. Based on this detection, the switching detection unit 320 detects that the direction switching valve 64 has been switched from the first position 64a, which is the first position, to the second position 64b, which is the second position. It is detected that the second position 64b is switched to the first position 64a. When the switching detection unit 320 detects that the direction switching valve 64 is switched from the first position 64a to the second position 64b, the switching detection unit 320 outputs a second speed switching signal indicating that the direction switching valve 64 has been switched to the second position 64b. When it is detected that the valve 64 has been switched from the second position 64b to the first position 64a, a first speed switching signal indicating that the valve 64 has been switched to the first position 64a is output.

The first measuring unit 321 measures a first elapsed time that is an elapsed time after the direction switching valve 64 is switched to the second position 64b, that is, an elapsed time at the second position 64b of the direction switching valve 64 ( Timer A). The 1st measurement part 321 will start measurement of the 1st elapsed time, if the 2nd speed change signal outputted from change detection part 320 is acquired.
The first time determination unit 322 holds a first predetermined time that is a predetermined length of time, acquires the first elapsed time measured by the first measurement unit 321, and the first elapsed time in advance It is determined whether or not a predetermined first predetermined time has been reached. The first predetermined time is the time required for the direction switching valve 64 to switch to the second position 64b and the hydraulic switching valve 263 to switch to the second switching position 63b after the control unit 301 outputs the second speed command. That is, it is a length of time determined based on the time difference from the output of the second speed command to the switching to the second switching position 63b, and is, for example, 800 ms (milliseconds) in this embodiment.

  Since the time difference from the output of the second speed command to the switching to the second switching position 63b also changes depending on the temperature of the pilot oil, the first predetermined time is not limited to 800 ms, but the operating state of the hydraulic system. Different lengths may be used. For example, if the temperature of the pilot oil decreases and the viscosity increases due to the outside air temperature becoming below freezing point, it may be preferable that the first predetermined time is longer than 800 ms. Conversely, depending on the temperature of the pilot oil, the first predetermined time may be preferably shorter than 800 ms. Therefore, it can be said that the first predetermined time is determined based on the time difference from the output of the second speed command to the switching to the second switching position 63b and the temperature of the pilot oil.

  The pressure determination unit 323 acquires a pilot pressure measured by a pressure gauge such as the pressure detection unit 300 described above, and determines whether or not the acquired pilot pressure has reached a predetermined pressure. The pressure determination unit 323 is a pressure required to switch the hydraulic switching valve 263 to the second switching position 63b as a predetermined pressure, and to hold the hydraulic switching valve 263 at the second switching position 63b. 2 MPa is maintained.

  The holding unit 324 holds the second position 64b of the direction switching valve 64 if the pilot pressure has reached a predetermined pressure before the first elapsed time reaches the first predetermined time. The holding unit 324 has a flag (second position flag) indicating that the direction switching valve 64 is switched to the second position 64b. The holding unit 324 acquires the determination result by the first time determination unit 322 and the pilot pressure acquired by the pressure determination unit 323, the first elapsed time is less than 800 ms that is the first predetermined time, and the pilot pressure is When the pressure is 1.2 MPa or more, a flag (second position flag) indicating that the direction switching valve 64 is switched to the second position 64b is set to valid (ON), and the direction switching valve 64 is set to the second position. Hold at position 64b. Further, the holding unit 324 sets the second position flag to invalid (off OFF) when the direction switching valve 64 is switched to the first position 64a.

  The first switching unit 325 switches the direction switching valve 64 from the second position 64b to the first position 64a if the pilot pressure does not reach the predetermined pressure before the first elapsed time reaches the first predetermined time. . The first switching unit 325 acquires the pilot pressure acquired by the pressure determination unit 323 and the determination result by the first time determination unit 322, the pilot pressure is less than 1.2 MPa, and the determination by the first time determination unit 322 As a result, when the first elapsed time is equal to or longer than the first predetermined time of 800 ms, a first speed command is output to the direction switching valve 64 to switch the direction switching valve 64 from the second position 64b to the first position 64a.

The position detection unit 326 detects that the direction switching valve 64 is held at the second position 64b, and the second position flag of the holding unit 324 is valid (ON) or invalid (OFF). It is detected whether or not the direction switching valve 64 is held at the second position 64b based on the second position flag.
The second measuring unit 327 detects that the direction switching valve 64 is held at the second position 64b and the pilot pressure is lower than the predetermined pressure, that is, the predetermined pressure used by the pressure determination unit 323 is less than 1.2 MPa. A timer that measures a second elapsed time that is an elapsed time since the pilot pressure has decreased below the predetermined pressure of 1.2 MPa (that is, a time during which the pilot pressure has decreased below the predetermined pressure). (Timer B). Since the holding of the direction switching valve 64 at the second position 64b is detected, the pilot pressure once exceeds a predetermined pressure (1.2 MPa). In other words, the second measuring unit 327 measures the time during which the pilot pressure that has once exceeded the predetermined pressure (1.2 MPa) is less than the predetermined pressure.

  The second time determination unit 328 determines whether or not the measured second elapsed time has reached a second predetermined time that is a predetermined length of time unlike the first predetermined time. The second predetermined time is held, the second elapsed time measured by the second measuring unit 327 is acquired, and it is determined whether the second elapsed time has reached a predetermined second predetermined time. The second predetermined time is different from the first predetermined time, and the second predetermined time decreases when the pilot pressure temporarily decreases due to a disturbance or the like and becomes less than the predetermined pressure (1.2 MPa). This is a length of time determined based on the time required for the pilot pressure to return to the predetermined pressure, and is 500 ms (milliseconds) in this embodiment, for example.

  Note that the time required for the pilot pressure that has decreased due to disturbance or the like to return to the predetermined pressure also changes depending on the temperature of the pilot oil. Therefore, the second predetermined time is not limited to 500 ms, and the operating state of the hydraulic system is not limited. Different lengths may be used. For example, if the temperature of the pilot oil decreases and the viscosity increases due to the outside air temperature becoming below freezing point, it may be preferable that the second predetermined time is longer than 500 ms. Conversely, depending on the temperature of the pilot oil, the second predetermined time may be preferably shorter than 500 ms. In the present embodiment, the second predetermined time is set to a time shorter than the first predetermined time. The reason is that the second measuring unit 327 that measures the second elapsed time operates after the holding of the direction switching valve 64 at the second position 64b is detected at least once, so that the pilot oil warms up even slightly. This is because the pressure transmission of the pilot oil is considered to be smooth.

  The second switching unit 329 switches the direction switching valve 64 from the second position 64b to the first position 64a when the second elapsed time reaches the second predetermined time, and the direction switching valve 64 at the second position 64b is switched. When the holding is detected and the pilot pressure becomes less than the predetermined pressure and the second elapsed time reaches the second predetermined time (more than the second predetermined time), the direction switching valve 64 is moved to the second position 64b. To the first position 64a. The second switching unit 329 acquires the pilot pressure acquired by the pressure determination unit 323, the second position flag of the holding unit 324, and the determination result by the second time determination unit 328, and the pilot pressure is less than 1.2 MPa. If the second position flag is valid (ON) and the determination result by the second time determination unit 328 is equal to or longer than 500 ms, which is the second predetermined time, the direction switching valve A first speed command is output to 64, and the direction switching valve 64 is switched from the second position 64b to the first position 64a.

The operation of the control unit 301 having the above configuration will be described with reference to FIG.
FIG. 2 is a diagram illustrating a flow of the control method of the hydraulic system according to the present embodiment.
The control unit 301 outputs a first speed command or a second speed command according to the operation of the operation member 302, but at the beginning (START) of the flowchart of FIG. 2, the operation member 302 is at a position where the HST motor 257 is set to the first speed. The control unit 301 outputs a first speed command. Therefore, the direction switching valve 64 is in the first position 64a.

When the operation member 302 is operated by an operator of the work machine 1 or the like, the control unit 301 detects whether the switching detection unit 320 outputs a first speed command or a second speed command (step S100). ).
If the switching detection unit 320 detects the first speed command (step S100: No), the direction switching valve 64 is in the first position 64a, and if the second speed command is detected (step S100: Yes), the direction. It can be seen that the switching valve 64 has been switched from the first position 64a to the second position 64b or in the second position 64b.

If the switching detection unit 320 detects the first speed command in step S100 (step S100: No), the control unit 301 ends the control shown in the flow of FIG.
If switching detection part 320 has detected the 2nd speed instruction | command in step S100 (step S100: Yes), a process will transfer to step S110. In step S110, the switching detection unit 320 outputs the second speed switching signal to the first measuring unit 321, and the first measuring unit 321 acquires the output second speed switching signal. The 1st measurement part 321 will start measurement of the 1st elapsed time, if a 2nd speed change signal is acquired (Step S110).

Accordingly, the first measurement unit 321 starts measuring the first elapsed time that is the elapsed time since the direction switching valve 64 is switched to the second position 64b, and the process transitions to step S120.
The pressure determination unit 323 acquires the pilot pressure measured by the pressure detection unit 300 if the switching detection unit 320 detects the second speed command in step S100 (S100: Yes), and the acquired pilot pressure is determined in advance. It is determined whether the predetermined pressure is 1.2 MPa or more or less than 1.2 MPa (step S120).

When it is determined in step S120 that the pilot pressure is less than the predetermined pressure (1.2 MPa) (step S120: No), the position detection unit 326 indicates that the second position flag of the holding unit 324 is valid (ON). Or invalid (OFF) is detected (step S130).
When the position detection unit 326 detects that the second position flag is invalid (OFF) in step S130 (step S130: No), the control unit 301 refers to the first elapsed time measured by the first measurement unit 321. Then, it is determined whether the first elapsed time is equal to or longer than the first predetermined time of 800 ms or less (step S140).

  If the first elapsed time is less than 800 ms in step S140 (step S140: No), the process returns to step S120, and the pressure determination unit 323 acquires and acquires the pilot pressure measured by the pressure detection unit 300 again. It is determined whether the pilot pressure is 1.2 MPa, which is a predetermined pressure, or less than 1.2 MPa (step S120).

When it is determined in step S120 that the pilot pressure is equal to or higher than the predetermined pressure (1.2 MPa) (step S120: Yes), the holding unit 324 sets the second position flag of the holding unit 324 to valid (ON). (Step S150).
When the second position flag is set valid (ON) in step S150, the first measurement unit 321 stops measuring the first elapsed time and sets the first elapsed time that has already been measured to an initial value (for example, zero 0). ) Is set (step S160).

When the first elapsed time is set to the initial value (reset) in step S160, the pressure determination unit 323 acquires the pilot pressure measured by the pressure detection unit 300 three times, and the acquired pilot pressure is determined in advance. It is determined whether or not the pressure is a predetermined pressure (step S120).
Thereafter, as long as it is determined that the pilot pressure is equal to or higher than the predetermined pressure (1.2 MPa) in step S120 (step S120: Yes), a loop returning from step S120 to step S120 through steps S150 and S160 is repeated. .

Here, when it is determined that the pilot pressure decreases and is lower than the predetermined pressure (1.2 MPa) (step S120: No), the position detection unit 326 indicates that the second position flag of the holding unit 324 is valid (ON). ) Or invalid (OFF) (step S130).
When it is detected in step S130 that the second position flag is valid (ON) (step S130: Yes), the control unit 301 operates the second measurement unit 327 to start measuring the second elapsed time ( Step S170).

As a result, when the second measuring unit 327 detects that the direction switching valve 64 is held at the second position 64b and the pilot pressure becomes less than 1.2 MPa, the pilot pressure decreases to less than 1.2 MPa. Measurement of the second elapsed time, which is the elapsed time since then, is started.
When the second measurement unit 327 starts operating in step S170, the second time determination unit 328 acquires the second elapsed time, and whether the second elapsed time is equal to or longer than the second predetermined time (500 ms) or the second predetermined time. It is determined whether it is less than (step S180).

If the second elapsed time is less than the second predetermined time in step S180 (step S180: No), the control unit 301 returns the process to step S120.
At this time, the pilot pressure recovers (increases) to become a predetermined pressure (1.2 MPa) or more, and if the pilot pressure acquired four times by the pressure determination unit 323 is 1.2 MPa or more which is a predetermined pressure ( In step S120: Yes), the process proceeds to step S150, but the second position flag is already valid (ON), and the process further proceeds to step S160.

Here, the second measurement unit 327 stops measuring the second elapsed time, and sets the already measured second elapsed time to an initial value (for example, zero 0) (step S160).
Thereafter, if the pilot pressure is less than the predetermined pressure of 1.2 MPa when the process returns to step S120, the process returns to step S180 via steps S120, S130, and S170.

  If the second elapsed time is less than the second predetermined time (step S180: No), the process returns to step S120 as described above, but if the pilot pressure is continuously less than the predetermined pressure of 1.2 MPa, step From S120, the loop returning to step S120 through step S130, step S170 and step S180 is repeated, and the second elapsed time is accumulated.

If it is determined in step S180 that the second elapsed time is equal to or longer than 500 ms, which is the second predetermined time (step S180: Yes), the control unit 301 outputs a first speed command and turns the direction switching valve 64 to the second direction. Switching from the position 64b to the first position 64a (step S190).
Subsequent to step S190, the control unit 301 has a second position flag that the holding unit 324 has and is valid (ON), and indicates that the direction switching valve 64 is in the first position 64a (invalid (OFF)). (Step S200).

After or simultaneously with steps S190 and S200, the second measuring unit 327 stops measuring the second elapsed time, and sets the already measured second elapsed time to an initial value (for example, zero 0) (step S210).
With reference to FIG. 3, the above-described control flow will be supplemented with the description.
FIG. 3 is a graph showing a time-series change of pilot pressure in the control method of the hydraulic system according to the present embodiment. The vertical axis in FIG. 3 indicates pilot pressure, and the horizontal axis indicates time. The pilot pressure indicated by the solid line L1 in FIG. 3 repeatedly decreases up and down several times, such as being a predetermined pressure of 1.2 MPa or more and less, and finally decreases greatly. This pressure change will be described with reference to the control flow described above.

  Since the pilot pressure indicated by the solid line L1 is equal to or higher than 1.2 MPa, which is a predetermined pressure at time 0, the control unit 301 outputs a second speed command, the direction switching valve 64 is at the second position 64b, and the holding unit 324 The second position flag is valid (ON). At this time, in the control flow of FIG. 3, the process repeats a loop from step S120 to step S120 through step S150 and step S160.

  Thereafter, the pilot pressure is less than the predetermined pressure of 1.2 MPa for some reason. At this time, in the control flow of FIG. 3, the process repeats a loop from step S120 to step S120 through step S130, step S170, and step S180, and the second elapsed time (timer B) is accumulated. In FIG. 3, for the first time when the pilot pressure becomes less than 1.2 MPa, when the second elapsed time (timer B) becomes 220 ms, the pilot pressure becomes equal to or higher than the predetermined pressure of 1.2 MPa, and the processing is performed in step S120. To the loop returning to step S120 via steps S150 and S160. The second time, when the second elapsed time (timer B) reaches 250 ms, the pilot pressure becomes equal to or higher than the predetermined pressure of 1.2 MPa, and the process returns from step S120 to step S120 through steps S150 and S160. Is back to

  However, for the third time, the pilot pressure becomes less than the predetermined pressure of 1.2 MPa, and the process of returning from step S120 to step S120 through step S130, step S170, and step S180 is repeated and accumulated in step S180. It is determined that the second elapsed time (timer B) is 500 ms or more (time T1). At this time, as described above, the control unit 301 outputs a first speed command through steps S190 to S210. By this first speed command, the direction switching valve 64 is set to the first position 64a, and the pilot pressure rapidly decreases.

  Here, it returns to the beginning (START) of the flowchart of FIG. 2 irrespective of the above description. The operation member 302 is in a position where the HST motor 257 is set to the first speed, the control unit 301 outputs a first speed command, and the direction switching valve 64 is in the first position 64a. Thereafter, when the operator of the work machine 1 operates the operation member 302 and the operation member 302 moves to a position where the HST motor 257 is set to the second speed, the output of the second speed command is detected in step S100, and further, step S110. In step 1, measurement of the first elapsed time is started.

  At this time, if it is determined in step S120 that the pilot pressure is equal to or higher than the predetermined pressure of 1.2 MPa (step S120: Yes), the process proceeds to step S170 and the above control is executed. If it is determined in step S120 that the pilot pressure is less than the predetermined pressure of 1.2 MPa (step S120: No), the process proceeds to step S130. However, the second position flag is not yet valid (ON) and remains invalid (OFF) (step S130: No), and the process transitions to step S140. If the first elapsed time is less than 800 ms, which is the first predetermined time in step S140 (step S140: No), and the pilot pressure continues to be less than 1.2 MPa, which is the predetermined pressure (step S120: No), from step S140 The loop returning to step S140 through step S120 and step S130 is repeated, and the first elapsed time is accumulated.

  If the pilot pressure does not exceed the predetermined pressure of 1.2 MPa (step S120: No) and it is determined in step S140 that the first elapsed time is equal to or longer than the first predetermined time (800 ms) (step S140: Yes). Then, the process proceeds to step S190, the control unit 301 outputs a first speed command, and the operation member 302 returns to the position where the HST motor 257 is set to the first speed. Thereafter, the process proceeds to step S200, and the second position flag is kept invalid (OFF). In the subsequent step S210, the measurement of the first elapsed time is stopped and reset, and the flow shown in FIG. 2 ends.

With reference to FIG. 4, the above-described control flow will be supplemented with the description.
FIG. 4 is a graph showing a time-series change of pilot pressure in the control method of the hydraulic system according to the present embodiment. The vertical axis in FIG. 4 indicates pilot pressure, and the horizontal axis indicates time. The pilot pressure indicated by the solid line L2 in FIG. 4 starts to increase at time T2, and is 1.2 MPa or more which is a predetermined pressure at time T3. This pressure change will be described with reference to the control flow described above.

Referring to FIG. 3, when the operator of work implement 1 or the like operates operation member 302 at time T2 and operation member 302 moves to a position where HST motor 257 is set to the second speed, control unit 301 moves to the second speed at step S100. A command is output, and the direction switching valve 64 is set to the second position 64b.
The pilot pressure indicated by the solid line L2 starts to rise from time T2 when the direction switching valve 64 is set to the second position 64b. At this time, in the control flow of FIG. 2, the process repeats a loop from step S120 to step S120 through step S130 and step S140.

  Thereafter, the pilot pressure is 1.2 MPa or more which is a predetermined pressure at time T3. At this time, since the time T3 is less than the first predetermined time (800 ms) (step S140: No), it is determined in the following step S120 that the pilot pressure is 1.2 MPa or more (step S120: Yes), and the processing is performed. Then, the process proceeds from step S120 described above to a loop that returns to step S120 through steps S150 and S160.

  However, the pilot pressure indicated by the broken line in FIG. 4 does not exceed 1.2 MPa even if it exceeds the time T3 and exceeds the first predetermined time of 800 ms. At this time, it is determined that the pilot pressure is less than 1.2 MPa (step S120: No), and it is determined that the first elapsed time is equal to or longer than the first predetermined time (800 ms) (step S140: Yes). Then, the process proceeds to step S190, and as described above, the control unit 301 outputs a first speed command through steps S190 to S210. By this first speed command, the direction switching valve 64 is set to the first position 64a.

  Here, referring to FIGS. 3 and 4 again, FIG. 4 shows that after switching from the first speed command to the second speed command at time T2, that is, the direction switching valve 64 is switched from the first position 64a to the second position 64b. It can be said that it is a graph which shows the change of pilot pressure later. Further, FIG. 3 can be said to be a graph showing a change in pilot pressure when the second speed command has already been output and the hydraulic pressure switching valve 263 is set to the second switching position 63b.

  Here, it should be noted that the state shown in FIG. 4 occurs when the operation member 302 is operated for the first time after the engine of the work machine 1 is started. In particular, when the operating member 302 is operated for the first time in a state where the engine is started and the pilot oil is not sufficiently warmed up in extremely cold conditions such as below freezing point, the fluidity of the low-temperature pilot oil is sufficiently ensured. Therefore, the pilot pressure immediately after the direction switching valve 64 is switched to the second position 64b may not rise smoothly.

  Under such conditions that it is difficult to smoothly increase the pilot pressure, the first predetermined time is the same as the second predetermined time (500 ms) on the assumption that the pilot oil has been warmed up even slightly. If it is set to, as shown in FIG. 4, when 500 ms elapses, the pilot pressure does not become a predetermined pressure (1.2 MPa) or more. Therefore, when the first predetermined time is set to a length (700 ms to 900 ms) that is about 1.4 to 1.8 times the second predetermined time, the switching of the hydraulic pressure switching valve 263 is smooth even in extremely cold regions. Done. If the pilot pressure does not rise to the predetermined pressure even after such a first predetermined time, it is determined that the pilot oil needs to be warmed up, and the first speed command is issued to maintain the hydraulic pressure switching valve 263 at the first switching position 63a. Is output to return the direction switching valve 64 to the first position 64a.

However, when the pilot pressure is equal to or higher than the predetermined pressure (1.2 MPa) even once, the first predetermined time may be changed to the same length as the second predetermined time. Setting the first predetermined time to be longer than the second predetermined time is important when the operation member 302 is operated for the first time in an extremely cold region.
In the above-described embodiment, the determination of switching from the second speed command to the first speed command shown in FIG. 4 is based on the first predetermined time and the pilot pressure. However, switching from the second speed command to the first speed command can also be determined based on the rate of change of the pilot pressure immediately after time T2 in FIG.

For example, the first switching unit 325 according to the present embodiment acquires the change rate (increase rate) of the pilot pressure immediately after time T2 from the differential value of the portion in the graph shown in FIG. It is determined whether or not the pilot pressure becomes equal to or higher than a predetermined pressure (1.2 MPa) after the first predetermined time has elapsed.
Hereinafter, a modification of the present embodiment will be described with reference to FIG. FIG. 5 is a control flow for determining switching from the second speed command to the first speed command based on the rate of change of the pilot pressure. In FIG. 5, the same operations as those in the control flow of FIG. Further, in FIG. 5, the operation relating to the timer A is not performed, and the description is advanced.

  As shown in FIG. 5, if the switching detection unit 320 detects the second speed command in step S100 (step S100: Yes), the control unit 301 transitions to step S300. In step S300, when the switching detection unit 320 outputs the second speed switching signal, the control unit 301 continues to acquire the pilot pressure detected by the pressure detection unit 300 for a predetermined time, and the pilot pressure is determined from the transition of the pilot pressure in the predetermined time. The rate of change of pressure is detected. And when the change rate of pilot pressure is smaller than the predetermined determination value (increase determination value) (step S310: No), the control part 301 (1st switching part 325) passes through step S130, A first speed command is output to the direction switching valve 64 to switch the direction switching valve 64 from the second position 64b to the first position 64a (step S190). That is, the first switching unit 325 determines not to hold the direction switching valve 64 at the second position 64b based on the rate of change of the pilot pressure, and moves the direction switching valve 64 from the second position 64b to the first position 64a. Switch.

  The increase determination value is a value for determining whether or not the pilot pressure reaches a predetermined pressure (1.2 MPa) or more in a short time based on the change rate of the pilot pressure, and is based on the oil temperature or the like. It is determined. For example, when the pilot oil is low in temperature and the fluidity of the pilot oil is not sufficiently secured, the rate of change of the pilot pressure is small, and the pilot pressure reaches a predetermined pressure (1.2 MPa) or more. It takes time. On the other hand, when the pilot oil is hot and the fluidity of the pilot oil is sufficiently secured, the rate of change of the pilot pressure is large, and it is short for the pilot pressure to reach a predetermined pressure (1.2 MPa) or higher. It takes time. Thus, the increase determination value is also set based on the temperature of the pilot oil.

  On the other hand, when the change rate of the pilot pressure is larger than a predetermined determination value (increase determination value) (step S310: Yes), the control unit 301 (first switching unit 325) sets the direction switching valve 64 to 2. Hold fast. In addition, regarding each step of S120, S130, S160, S170, S180, S200, and S210 shown in FIG. 5, there is no operation related to the timer A, and although the order is partially different from that in FIG. The same.

According to the control method of the hydraulic system according to the present embodiment described above, the operation of the hydraulic system related to switching from the first speed to the second speed by the hydraulic switching valve is smoothly performed even in an extremely cold region. Can do.
The operation of step S110 in FIG. 2, that is, the first elapsed time, which is the elapsed time at which the direction switching valve 64 is at the second position 64b, is measured at least once, and the direction switching valve 64 is moved from the second position 64b to the second time. After the step of switching to the first position 64a is performed, it may be performed again when switching from the first position 64a to the second position 64b is performed. Specifically, as shown in FIG. 2, after the direction switching valve 64 is switched from the second position 64b to the first position 64a in step S190, the switching detector 320 is set to 2 again in step S100. When the speed command is detected, the operation of step S110 is started. That is, after the engine 29 is started, when the second speed command is first issued by the operation member 302, the step S110 is exceptionally not performed, and then the second speed command is issued by the operation member 302 from the state of the first speed. If it is, step S110 is executed.

According to the control method of the hydraulic system according to the first embodiment described above, the operation of the hydraulic system related to the switching from the first speed to the second speed by the hydraulic switching valve is smoothly performed even in a cold region of extremely cold. be able to.
[Second Embodiment]
FIG. 6 is a diagram illustrating a flow of a control method of the hydraulic system according to the second embodiment. The configuration of the control unit 301 (switching detection unit 320, first measurement unit 321, first time determination unit 322, pressure determination unit 323, holding unit 324, first switching unit 325, position detection unit 326, second measurement unit About 327, the 2nd time determination part 328, and the 2nd switching part 329), it is the same as that of 1st Embodiment. In the second embodiment, the control unit 301 has a “first speed mode” that is a mode for performing control related to the first speed and a “second speed mode” that is a mode for performing control regarding the second speed. As the explanation proceeds.

  When the operation member 302 is operated by an operator or the like, the control unit 301 determines whether or not the operation of the operation member 302 is an operation corresponding to the second speed command (step S300). When the operation of the operation member 302 is an operation corresponding to the second speed command (step S300: Yes), the switching detection unit 320 detects whether or not the control unit 301 is already operating in the second speed mode (step S300). S301). That is, in step S301, the switching detection unit 320 detects that the direction switching valve 64 has been switched to the first position or the second position.

The control unit 301 is not in the second speed mode (step S301: No), and maintains the first speed mode (step S302). If the second speed mode is selected (step S301: Yes), the control unit 301 holds the second speed mode (step S303). That is, the control unit 301 holds the second position flag included in the holding unit 324 valid (ON).
In step S303, the switching detection unit 320 outputs a second speed switching signal to the first measuring unit 321, and the first measuring unit 321 acquires the output second speed switching signal. When acquiring the second speed switching signal, the first measuring unit 321 starts measuring the first elapsed time (operation of the timer A) (step S304). Accordingly, the first measurement unit 321 starts measuring the first elapsed time that is the elapsed time after the direction switching valve 64 is switched to the second position 64b, and the process transitions to step S305.

  Next, the control unit 301 detects again whether or not it is operating in the second speed mode (step S305). Here, if the control unit 301 is in the second speed mode (step S305: Yes), the control unit 301 is the time during which the pilot pressure measured by the pressure detection unit 300 is equal to or less than a predetermined value as shown in S306 to S310. Whether the direction switching valve 64 is held at the second position 64b or switched to the first position 64a is performed depending on whether or not 500 ms is continuously exceeded.

  Specifically, if the control unit 301 is in the second speed mode (step S305: Yes), the process proceeds to step S306. In step S306, the pressure determination unit 323 determines the pilot pressure measured by the pressure detection unit 300. Is determined, and it is determined whether the acquired pilot pressure is equal to or higher than a predetermined pressure of 1.2 MPa or less than 1.2 MPa (step S306).

  When the pilot pressure is 1.2 MPa or less (step S306: Yes), the position detection unit 326 detects whether the second position flag of the holding unit 324 is valid (ON) or invalid (OFF). (Step S307). When the second position flag included in the holding unit 324 is invalid (OFF), the process proceeds to step S308. In step S308, the second time determination unit 328 refers to the second elapsed time, and the second elapsed time is the second time. It is determined whether it is a predetermined time (500 ms) or more or less than a second predetermined time. When the second elapsed time is less than the second predetermined time (500 ms) (step S308: No), the measurement of the second elapsed time (operation of the timer B) in the second measuring unit 327 is continued (step S309). If the second elapsed time is equal to or longer than the second predetermined time (step S308: Yes), the control unit 301 enters the first speed mode, and the control unit 301 (second switching unit 329) outputs a first speed command, The direction switching valve 64 is switched from the second position 64b to the first position 64a (step S310).

In step S305 described above, when the control unit 301 is not in the second speed mode but in the first speed mode, the control unit 301 sets (resets) the second elapsed time to an initial value (step S311).
And after performing any of step S310 and step S311, the control part 301 detects again whether it is operate | moving in 2nd speed mode (step S312). When the control unit 301 is in the second speed mode, the first time determination unit 322 refers to the first elapsed time measured by the first measurement unit 321 and the first elapsed time is 800 ms or more which is the first predetermined time. Or less than 800 ms (step S313). When the first elapsed time is 800 ms or more which is the first predetermined time in the determination result by the first time determination unit 322 (step S313: Yes), the control unit 301 sets the first elapsed time to an initial value (reset). In step S314, the second position flag of the holding unit 324 is invalidated (OFF) (step S315). On the other hand, when the first elapsed time is less than the first predetermined time of 800 ms (step S313: No), the control unit 301 continues to measure the first elapsed time (operation of the timer A) by the first measurement unit 321. (Step S316).

  And after performing any of step S315 and step S316, it returns to step S300. If the control unit 301 has already returned to step S300 in the second speed mode and reaches step S303 and step S304, the second speed mode is maintained in step S303, and the first measurement unit 321 performs the first measurement in step S304. 1. Continue measuring elapsed time (timer A operation).

In the control method of the hydraulic system according to the second embodiment described above as well as in the extremely cold region, particularly the operation of the hydraulic system related to switching from the first speed to the second speed by the hydraulic switching valve is performed smoothly. Can do.
[Third embodiment]
FIG. 7 is a diagram illustrating a hydraulic circuit of the hydraulic system according to the third embodiment. In the third embodiment, descriptions of configurations and methods similar to those in the first embodiment and the second embodiment are omitted.

  As shown in FIG. 7, the pressure detection part 300 is provided in the 1st oil path 100a and the 2nd oil path 100x. Hereinafter, the pressure detector provided in the first oil passage 100a is referred to as a first pressure detector 300a, and the pressure detector provided in the second oil passage 100x is referred to as a second pressure detector 300b. Also in this case, when the pilot pressure detected by the first pressure detection unit 300a becomes less than the set value in the state where the second speed command is output, the control unit 301 sends the first speed command to the direction switching valve. 64.

  When the first pressure detection unit 300a is provided in the first oil passage 100a and the pilot pressure in the first oil passage 100a decreases due to some circumstances, the direction switching valve 64 is moved to the second position by the control of the control unit 301 described above. The hydraulic pressure switching valve 263 can be switched to the first switching position 63a by switching from 64b to the first position 64a. As a result, the HST motor 257 can be forcibly changed from the second speed to the first speed. Thereafter, when the drop in pilot pressure in the first oil passage 100a is recovered, the operator of the work machine 1 can operate the operation member 302 to return the HST motor 257 from the first speed to the second speed.

  The controller 301 outputs the first speed command to the direction switching valve 64 when the pilot pressure detected by the second pressure detector 300b becomes less than the set value in the state where the second speed command is being output. . Here, after the control unit 301 outputs the first speed command to the direction switching valve 64, the pilot pressure detected by the first pressure detection unit 300a may return to a set value or more. If the second speed command from the operation member 302 is maintained when the pilot pressure returns to the set value or higher, the control unit 301 automatically outputs the second speed command to the direction switching valve 64.

  Alternatively, the control unit 301 outputs the first speed command to the direction switching valve 64 as described above, and then the pilot pressure detected by the first pressure detection unit 300a provided in the first oil passage 100a becomes equal to or higher than the set value. When the second speed is set by the operation member 302, a second speed command is output to the direction switching valve 64. On the contrary, an operation (second speed command) for setting the direction switching valve 64 to the second position 64b by the operating member 302 in a state where the pilot pressure detected by the first pressure detector 300a is less than a predetermined value. Is performed, the control unit 301 holds the direction switching valve 64 at the first position 64a (first speed command).

  In other words, the control unit 301 forcibly changes from the second speed to the first speed, that is, in the state where the first speed command for setting the direction switching valve 64 to the first position 64a is being output, to the first oil passage 100a. When the pilot pressure detected by the provided first pressure detector 300a returns to a set value or more, the directional switching valve 64 is set to the second position 64b, whereby the hydraulic switching valve 263 is set to the second switching position 63b. Can be switched to. As a result, the HST motor 257 can be returned from the first speed to the second speed. The pilot pressure (return pressure) detected by the second pressure detection unit 300b when returning from the first speed to the second speed may not be equal to or higher than the set value described above. For example, the pilot pressure (set value) set at the second switching position 63b may be the same as the return pressure for returning from the first speed to the second speed, but the return pressure and the set pressure are different from each other. Also good.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. In the embodiment described above, the hydraulic pressure switching valve 263 is set to the first speed by setting the direction switching valve 64 to the first position 64a and discharging the pilot oil in the second oil passage 100x to the hydraulic oil tank 31. In addition, the hydraulic pressure switching valve 263 may be set to the first speed by switching the direction switching valve 64 to set the pressure of the pilot oil in the second oil passage 100x to a predetermined pressure. That is, when the direction switching valve 64 is in the second position having an opening larger than the predetermined opening, the hydraulic switching valve 263 is in the first speed and is in the first position having the predetermined opening. The hydraulic switching valve 263 may be configured to be 2nd speed.

DESCRIPTION OF SYMBOLS 1 Work implement 29 Engine 52 Relief valve 63a 1st switching position 63b 2nd switching position 63c Neutral position 64 2nd speed switching valve (direction switching valve)
64a 1st position 64b 2nd position 81 2nd throttle part 100a 1st oil path 100x 2nd oil path 257 HST motor 257A 1st motor 257B 2nd motor 263 Hydraulic switching valve 300 Pressure detection part 301 Control part 302 Operation member 320 Switching Detection unit 321 First measurement unit 322 First time determination unit 323 Pressure determination unit 324 Holding unit 325 First switching unit 326 Position detection unit 327 Second measurement unit 328 Second time determination unit 329 Second switching unit P3 Third pump ( Hydraulic pump)

Claims (6)

The directional control valve that can change the pilot pressure applied to the hydraulic switching valve that can be switched to a plurality of switching positions according to the pilot pressure that is the pressure of the pilot oil by setting the opening degree is a predetermined opening degree. Detecting that the position has been switched to the second position, which is an opening larger than a predetermined position corresponding to the first position or the first position;
Measuring a first elapsed time which is an elapsed time at the second position of the direction switching valve;
Determining whether the measured first elapsed time has reached a predetermined first predetermined time; and
Determining whether the pilot pressure has reached a predetermined pressure;
Holding the second position of the directional control valve if the pilot pressure has reached a predetermined pressure before the first elapsed time reaches the first predetermined time;
Switching the direction switching valve from the second position to the first position if the pilot pressure has not reached the predetermined pressure before the first elapsed time reaches the first predetermined time;
Detecting that the direction switching valve is held in the second position;
When the holding of the direction switching valve at the second position is detected and the pilot pressure is lower than the predetermined pressure, a second elapsed time that is a time during which the pilot pressure is reduced below the predetermined pressure is determined. Measuring step,
Determining whether the measured second elapsed time has reached a second predetermined time different from the first predetermined time;
When the second elapsed time reaches the second predetermined time, the step of switching the direction switching valve from the second position to the first position;
A method for controlling a hydraulic system of a work machine comprising: The second predetermined time is a time based on the temperature of the pilot oil,
2. The method of controlling a hydraulic system for a work machine according to claim 1 , wherein the first predetermined time is longer than the second predetermined time. The method of controlling a hydraulic system for a working machine according to claim 1 or 2 , wherein the second predetermined time is used instead of the first predetermined time after the direction switching valve is once held in the second position. The first elapsed time, which is the elapsed time at the second position of the direction switching valve, is measured after the step of switching the direction switching valve from the second position to the first position is performed at least once. The method for controlling the hydraulic system for a working machine according to claim 1, wherein the method is performed when switching from the first position to the second position is performed. A hydraulic pump for supplying pilot oil;
A hydraulic switching valve that can be switched to a plurality of switching positions in accordance with a pilot pressure that is the pressure of the pilot oil;
A directional switching valve capable of changing the pilot pressure applied to the hydraulic switching valve by setting an opening;
A switching detector for detecting that the direction switching valve has been switched to a first position having a predetermined opening or a second position having an opening larger than a predetermined opening corresponding to the first position;
A first measuring unit that measures a first elapsed time that is an elapsed time at the second position of the direction switching valve;
A first time determination unit that determines whether or not the measured first elapsed time has reached a predetermined first predetermined time;
A pressure determining unit that determines whether or not the pilot pressure has reached a predetermined pressure;
A holding portion that holds the second position of the direction switching valve if the pilot pressure has reached a predetermined pressure before the first elapsed time reaches the first predetermined time;
A first switching unit that switches the direction switching valve from the second position to the first position if the pilot pressure does not reach the predetermined pressure before the first elapsed time reaches the first predetermined time;
A position detector for detecting that the direction switching valve is held at the second position;
When the holding of the direction switching valve at the second position is detected and the pilot pressure is lower than the predetermined pressure, a second elapsed time that is a time during which the pilot pressure is reduced below the predetermined pressure is determined. A second measuring unit for measuring;
A second time determination unit for determining whether or not the measured second elapsed time has reached a second predetermined time different from the first predetermined time;
A second switching unit that switches the direction switching valve from the second position to the first position when the second elapsed time reaches the second predetermined time;
A working machine hydraulic system. A working machine comprising the hydraulic system for a working machine according to claim 5,
The aircraft,
A cabin mounted on the aircraft;
Traveling devices disposed on the right and left sides of the aircraft;
A boom provided on the side of the cabin;
A work implement mounted on the boom;
Work machine equipped with.

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