JP2023016501A - work machine - Google Patents

Abstract

To measure a relief pressure of each work machine without introducing a special facility.SOLUTION: A work machine comprises: a left travel motor capable of transmitting driving force to a left travel device and capable of switching between a first speed and a second speed faster than the first speed; a right travel motor capable of transmitting driving force to a right travel device and capable of switching between a first speed and a second speed faster than the first speed; a braking device braking the left travel motor and the right travel motor; a pressure measuring device measuring a pressure of hydraulic oil in a first circulation oil passage and a second circulation oil passage; and a control device obtaining the pressure of the hydraulic oil in the first circulation oil passage and the second circulation oil passage measured by the pressure measuring device when the braking device brakes and the left travel motor and the right travel motor are at the second speed.SELECTED DRAWING: Figure 1

Description

The present invention relates to working machines such as skid steer loaders, compact track loaders, and backhoes.

As a technique for realizing deceleration according to the traveling state of a working machine, the technique disclosed in Patent Document 1 is known. The work machine of Patent Document 1 includes a prime mover provided on a machine body, a traveling device provided on the machine body, a traveling motor capable of transmitting power to the traveling device and capable of switching between a first speed and a second speed, A travel pump having a port for discharging hydraulic oil during forward rotation and another port for discharging hydraulic oil during reverse rotation, and first and second circulation oil passages connected to both ports of the travel pump and to the travel motor , first to fourth relief valves connected to the port-side oil passage in the first to second circulating oil passages, and from the second speed to the first speed when the traveling motor is at the second speed. and a control device for automatically decelerating to . The control device operates based on the first travel relief pressure of the first relief valve, the second travel relief pressure of the second relief valve, the third travel relief pressure of the third relief valve, and the fourth travel relief pressure of the fourth relief valve. A deceleration threshold for determining whether or not to automatically decelerate is set.

Japanese Patent Application No. 2020-137171

The technology disclosed in Patent Document 1 is based on the premise that the travel relief pressure (that is, the relief pressure of the HST pump) for each work implement is known. Therefore, Patent Literature 1 does not disclose a method for measuring the travel relief pressure for each work implement.
As a method for measuring the travel relief pressure for each individual vehicle, it is conceivable to measure the relief pressure of the HST pump before shipping the HST pump alone. However, considering the influence of the engine load, etc., there is a high possibility that the relief pressure of the HST pump when installed in the work machine and measured will differ from the relief pressure when the HST pump is measured alone. Also, since an error occurs in the running pressure sensor used in the automatic deceleration control, it is necessary to measure the relief pressure including this error.

On the other hand, when an HST pump is installed in a work machine to measure the travel relief pressure, it is known to use a dynamo or a parking brake as means for applying a load to the travel system. However, the dynamo is a large-scale facility, and a load can be applied to the travel system of the working machine only at the location where the dynamo is installed. In other words, the travel relief pressure cannot be measured unless the work implement is moved to a location where the dynamo is located.
Also, the parking brake is a device intended to brake the working machine so that it does not move from a stopped state, but the braking force exerted by the parking brake is large enough to resist the weight of the working machine. In other words, when a load near the relief pressure is applied to the HST pump, the driving force of the traveling system may exceed the braking force of the parking brake, and the working machine may begin to move.

In particular, if the HST pump or running pressure sensor used for automatic deceleration control is replaced in a work machine that has been on the market once, the relief pressure of the replaced part is measured and the must be corrected for component errors.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a working machine capable of measuring the relief pressure of each individual working machine without introducing special equipment. With the goal.

The technical measures taken by the present invention to solve the technical problems are as follows.
A work machine according to one aspect of the present invention includes a machine body, a prime mover provided in the machine body, a left traveling device provided on the left side of the machine body, a right traveling device provided on the right side of the machine body, and the left traveling device provided on the right side of the machine body. a left traveling motor capable of transmitting power to the traveling device and capable of being switched between a first speed and a second speed higher than the first speed; a right travel motor switchable to a second speed higher than the first speed; a left travel pump having a first port for discharging hydraulic oil during forward rotation and a second port for discharging hydraulic oil during reverse rotation; A right travel pump having a third port for discharging hydraulic oil and a fourth port for discharging hydraulic oil during reverse rotation; a connected first circulation oil passage, a second circulation oil passage connected to the third port and the fourth port of the right travel pump and connected to the right travel motor, the left travel motor and the a braking device for braking the right traveling motor; a pressure measuring device for measuring the pressure of hydraulic fluid in the first and second circulating oil passages; and a control device that acquires the pressure of hydraulic fluid in the first and second circulation passages measured by the pressure measurement device when the right travel motor is at the second speed.

The work machine described above is switchable between a first position and a second position, and sets the left travel motor and the right travel motor to the first speed when at the first position, and sets the right travel motor at the first speed when at the second position. a travel switching valve that switches the left travel motor and the right travel motor to the second speed when the travel speed is changed; and a control device that controls the travel switching valve and the braking device. The control device switches the travel switching valve to the second position and performs braking of the braking device when executing an acquisition mode for acquiring the pressure of the hydraulic fluid.
The control device is capable of switching the travel switching valve to the first position or the second position when the acquisition mode is not being executed, and is capable of braking or releasing the braking to the braking device. .

The above-described work machine includes a travel operation device that applies hydraulic oil to either the left travel pump or the right travel pump when the travel operation member is operated; A travel oil passage that connects with a travel pump and through which the hydraulic oil flows; and an operating valve that controls the hydraulic oil supplied to the travel oil passage. After executing braking by the braking device and switching the left travel motor and the right travel motor to a second speed, the control device controls the operating valve to supply hydraulic fluid to the travel oil passage. I do.
When the acquisition mode is not executed, the control device changes the speed from the second speed to the first speed based on the pressure of hydraulic fluid in either the first oil circulation passage or the second oil circulation passage. switch.

A work machine according to another aspect of the present invention includes a machine body, a left traveling device provided on the left side of the machine body, a right traveling device provided on the right side of the machine body, and power being able to be transmitted to the left traveling device. a left travel motor switchable between a first speed and a second speed higher than the first speed; and a first speed and a second speed higher than the first speed, capable of transmitting power to the right travel device. and a first swash plate, wherein a first port discharges hydraulic fluid when the first swash plate rotates forward and a first port discharges hydraulic fluid when the first swash plate rotates reversely. A left traveling pump having two ports, a second swash plate, a third port that discharges hydraulic fluid when the second swash plate rotates forward, and a fourth port that discharges hydraulic fluid when the second swash plate rotates backward. a right travel pump having a port; a left travel motor and a braking device for braking the right travel motor; connected to the first swash plate of the left travel pump and the second swash plate of the right travel pump; a travel oil passage through which the hydraulic oil flows; an operating valve that controls the hydraulic oil supplied to the travel oil passage; a controller for switching at least one of the left travel motor and the right motor to the second speed when operating the actuating valve and prior to operating the actuating valve.

A work machine according to still another aspect of the present invention is capable of transmitting power to a machine body, a left traveling device provided on the left side of the machine body, a right traveling device provided on the right side of the machine body, and the left traveling device. and a left travel motor switchable between a first speed and a second speed faster than the first speed; and a second travel motor capable of transmitting power to the right travel device at the first speed and a second speed faster than the first speed. and a first swash plate, wherein a first port discharges hydraulic fluid when the first swash plate rotates forward and hydraulic fluid is discharged when the first swash plate rotates reversely. A left travel pump having a second port, a second swash plate, a third port for discharging hydraulic oil when the second swash plate rotates forward, and a third port for discharging hydraulic oil when the second swash plate rotates reversely. a right travel pump having four ports; a left travel motor and a braking device for braking the right travel motor; and a first swash plate of the left travel pump and a second swash plate of the right travel pump. a traveling oil passage through which the hydraulic oil flows; an operating valve that controls the hydraulic oil supplied to the traveling oil passage; and a controller for inhibiting operation of the actuated valve when at one speed.

The control device increases hydraulic oil supplied to the traveling oil passage in a state in which braking is performed by the braking device and at least one of the left traveling motor and the right traveling motor is switched to the second speed. Or operate the actuated valve to decrease.
The work machine described above includes a prime mover. The control device executes braking by the braking device, at least one of the left travel motor and the right travel motor is switched to the second speed, and hydraulic oil is supplied to the travel oil passage by the operating valve. The number of revolutions of the prime mover is increased or decreased while

The control device switches at least one of the left travel motor and the right travel motor to the second speed when executing an acquisition mode for acquiring the pressure of hydraulic fluid supplied to the travel oil passage, Braking is performed by the braking device.
The above-described work machine includes a first circulation oil passage connected to the first port and the second port of the left travel pump and also connected to the left travel motor, the third port of the right travel pump and the a second circulating oil passage connected to the fourth port and connected to the right travel motor; and a pressure measuring device for measuring the pressure of hydraulic fluid in the first circulating oil passage and the second circulating oil passage. Prepare. The control device acquires the pressure of hydraulic fluid measured by the pressure measurement device.

The work machine described above includes a prime mover rotation speed detection device that acquires the actual revolution speed of the prime mover.
When the acquisition mode is released, the control device switches the left travel motor and/or the right travel motor from the second speed to the first speed and releases the braking by the braking device.
When a predetermined condition is satisfied when at least one of the left travel motor and the right travel motor is at the second speed, the control device controls the left travel motor and/or the right travel motor at the second speed. is automatically switched from the second speed to the first speed, and the control device executes the automatic deceleration control when the acquisition mode is executed. do not.

The actuated valve is composed of a plurality of actuated valves. When the acquisition mode is executed, the control device acquires the pressure of the hydraulic fluid supplied to the traveling oil passage by the operation of at least one of the plurality of operation valves, and then acquires the pressure of the remaining hydraulic fluid. Obtaining the pressure of the hydraulic oil supplied to the traveling oil passage by the operation of at least one of the operating valves.

According to the present invention, the relief pressure for each work machine can be measured by the work machine without introducing special equipment.

1 is a diagram showing a hydraulic system (hydraulic circuit) of a working machine according to an embodiment of the present invention; FIG. FIG. 4 is a diagram showing the operating direction of a travel operating member according to the present embodiment; FIG. 5 is a diagram showing an example of a first travel relief pressure, a second travel relief pressure, a third travel relief pressure, and a fourth travel relief pressure corresponding to the engine speed according to the present embodiment; It is a figure which shows the flowchart showing the flow of a process in the acquisition mode by this embodiment. FIG. 11 is a diagram showing a flowchart representing the flow of processing in a second acquisition mode according to a modified example of the present embodiment; FIG. 6 is a diagram showing part of a hydraulic system (hydraulic circuit) of a working machine according to a second embodiment of the present invention; FIG. 11 is a diagram showing part of a hydraulic system (hydraulic circuit) of a working machine according to a third embodiment of the present invention; It is a side view showing a track loader which is an example of a work machine according to the present embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a hydraulic system for a working machine according to the present invention and a working machine equipped with this hydraulic system will now be described with reference to the drawings as appropriate.
(First embodiment)
FIG. 6 is a side view of the working machine according to the first embodiment of the present invention. FIG. 6 shows a compact track loader as an example of the work machine. However, the work machine according to the present embodiment is not limited to the compact track loader, and may be other types of loader work machine such as a skid steer loader. Also, a work machine other than a loader work machine may be used.

As shown in FIG. 6, the working machine 1 includes a machine body 2, a cabin 3, a working device 4, and a pair of traveling devices 5L and 5R. In this embodiment, the front side of the driver (the left side in FIG. 4) sitting in the driver's seat 8 of the working machine 1 is the front side, the rear side of the driver (the right side in FIG. 4) is the rear side, and the left side of the driver (the left side in FIG. 4 is The front side) will be described as the left side, and the right side of the driver (back side in FIG. 4) will be described as the right side. Also, the horizontal direction, which is a direction orthogonal to the front-rear direction, will be described as the body width direction.

The direction from the central portion of the body 2 to the right or left will be described as the outward direction of the body. In other words, the outer side of the fuselage is the width direction of the fuselage and the direction away from the fuselage 2 . The direction opposite to the outer side of the fuselage will be described as the inner side of the fuselage. In other words, the inner side of the body is the width direction of the body and the direction toward the body 2 .
A cabin 3 is mounted on the airframe 2 . A driver's seat 8 is provided in the cabin 3 . The working device 4 is attached to the machine body 2 . A pair of traveling devices 5L and 5R are provided outside the body 2 . A prime mover 32 is mounted in the rear portion of the body 2 .
The work device 4 has a pair of booms 10 , a work implement 11 , a pair of lift links 12 , a pair of control links 13 , a pair of boom cylinders 14 and a pair of bucket cylinders 15 .

A pair of booms 10 are provided on the right and left sides of the cabin 3 so as to be vertically swingable. The work tool 11 is, for example, a bucket, and the bucket 11 is provided at the tip (front end) of the pair of booms 10 so as to be vertically swingable. The pair of lift links 12 and the pair of control links 13 support the bases (rear portions) of the corresponding booms 10 so that the pair of booms 10 can swing vertically. A pair of boom cylinders 14 raises and lowers the corresponding boom 10 by expanding and contracting. The pair of bucket cylinders 15 swings the bucket 11 by expanding and contracting.

The front portions of the booms 10 provided on the left and right sides are connected to each other by connecting pipes of an irregular shape. The bases (rear portions) of the booms 10 are connected to each other by circular connecting pipes.
A pair of lift links 12, a pair of control links 13, and a pair of boom cylinders 14 are provided on the left and right sides of the fuselage 2, corresponding to the booms 10 provided on the left and right sides, respectively.

A pair of lift links 12 are provided longitudinally at the rear of the base of corresponding booms 10 . The upper portion (one end side) of the pair of lift links 12 is pivotally supported toward the rear portion of the base of the corresponding boom 10 via a pivot shaft 16 (first pivot shaft) so as to be rotatable about a horizontal axis. Lower portions (other end sides) of the pair of lift links 12 are pivotally supported toward the rear portion of the fuselage 2 via pivot shafts 17 (second pivot shafts) so as to be rotatable about the horizontal axis. The second pivot shaft 17 is provided below the first pivot shaft 16 .

Upper portions of the pair of boom cylinders 14 are rotatably supported around a horizontal axis via a pivot shaft 18 (third pivot shaft). The third pivot shaft 18 is the base of the corresponding boom 10 and is provided at the front of the base. The lower portions of the pair of boom cylinders 14 are rotatably supported around the horizontal axis via a pivot shaft 19 (fourth pivot shaft). The fourth pivot shaft 19 is provided near the lower portion of the rear portion of the body 2 and below the third pivot shaft 18 .

A pair of control links 13 are provided in front of the corresponding lift links 12 . One ends of the pair of control links 13 are rotatably supported around the horizontal axis via pivot shafts 20 (fifth pivot shafts). The fifth pivot shaft 20 is provided in the fuselage 2 in front of the corresponding lift link 12 . The other ends of the pair of control links 13 are rotatably supported around the horizontal axis via a pivot shaft 21 (sixth pivot shaft). The sixth pivot shaft 21 is provided in front of the second pivot shaft 17 and above the second pivot shaft 17 in the corresponding boom 10 .

By extending and contracting the pair of boom cylinders 14, the pair of booms 10 swing up and down around the first pivot shaft 16 while the base of the corresponding boom 10 is supported by the pair of lift links 12 and the pair of control links 13. Then, the tip of the boom 10 moves up and down. The pair of control links 13 swings up and down around the fifth pivot shaft 20 as the corresponding boom 10 swings up and down. The pair of lift links 12 swing back and forth around the second pivot shaft 17 as the corresponding control link 13 swings up and down.

Instead of the bucket 11, another working tool can be attached to the front part of the pair of booms 10. - 特許庁Other tools include attachments (preliminary attachments) such as hydraulic crushers, hydraulic breakers, angle blooms, earth augers, pallet forks, sweepers, mowers, snow blowers, and the like.
A connection member 50 is provided on the front portion of the boom 10 on the left side. The connection member 50 is a device that connects the hydraulic equipment mounted on the spare attachment and the first pipe member such as a pipe provided on the boom 10 . Specifically, a first pipe member can be connected to one end of the connection member 50, and a second pipe member connected to the hydraulic equipment of the auxiliary attachment can be connected to the other end. As a result, hydraulic fluid flowing through the first pipe member passes through the second pipe member and is supplied to the hydraulic equipment.

A pair of bucket cylinders 15 are arranged near the front portion of the corresponding boom 10 . The bucket 11 is swung by extending and retracting the pair of bucket cylinders 15 .
Of the pair of traveling devices 5L and 5R, the traveling device 5L is provided on the left side of the body 2, and the traveling device 5R is provided on the right side of the body 2. The pair of traveling devices 5L and 5R are crawler type (including semi-crawler type) traveling devices in this embodiment. The pair of traveling devices 5L and 5R may be wheel-type traveling devices having front wheels and rear wheels. Hereinafter, for convenience of explanation, the traveling device 5L may be referred to as the left traveling device 5L, and the traveling device 5R may be referred to as the right traveling device 5R.

The prime mover 32 is an internal combustion engine such as a diesel engine or a gasoline engine, an electric motor, or the like. In this embodiment, the prime mover 32 is a diesel engine, but is not limited to this.
Next, a hydraulic system for a working machine according to this embodiment will be described with reference to FIG.

As shown in FIG. 1, the hydraulic system of the working machine includes a first hydraulic pump P1 and a second hydraulic pump P2. The first hydraulic pump P1 is a hydraulic pump that is driven by the power of the prime mover 32, and is composed of a constant displacement gear pump. The first hydraulic pump P<b>1 can discharge hydraulic oil stored in the tank 22 . In particular, the first hydraulic pump P1 discharges hydraulic oil that is mainly used for control. For convenience of explanation, the tank 22 that stores hydraulic oil may be referred to as a hydraulic oil tank. Among the hydraulic fluid discharged from the first hydraulic pump P1, the hydraulic fluid used for control is sometimes called pilot oil, and the pressure of the pilot oil is sometimes called pilot pressure.

The second hydraulic pump P2 is a hydraulic pump that is driven by the power of the prime mover 32, and is composed of a constant displacement gear pump. The second hydraulic pump P2 can discharge hydraulic oil stored in the tank 22, and supplies hydraulic oil to, for example, a work system oil passage. For example, the second hydraulic pump P2 includes a pair of boom cylinders 14 for operating a pair of booms 10, a pair of bucket cylinders 15 for operating a bucket, and a control valve (flow control valve) for controlling a preliminary hydraulic actuator for operating a preliminary hydraulic actuator. ) with hydraulic oil.

Moreover, the hydraulic system of the working machine includes a pair of traveling motors 36L, 36R and a pair of traveling pumps 53L, 53R. The pair of travel motors 36L, 36R are motors that transmit power to the pair of travel devices 5L, 5R. Of the pair of travel motors 36L and 36R,
The traveling motor 36L transmits rotational power to the traveling device (left traveling device) 5L, and the traveling motor 36R transmits rotational power to the traveling device (right traveling device) 5R.

The pair of traveling pumps 53L and 53R are pumps driven by the power of the prime mover 32, and are, for example, swash plate type variable displacement axial pumps. The pair of travel pumps 53L, 53R is driven to supply hydraulic fluid to each of the pair of travel motors 36L, 36R. Of the pair of travel pumps 53L and 53R, the travel pump 53L supplies hydraulic fluid to the travel pump 53L, and the travel pump 53R supplies hydraulic fluid to the travel pump 53R.

Hereinafter, for convenience of explanation, the traveling pump 53L will be referred to as the left traveling pump 53L, the traveling pump 53R will be referred to as the right traveling pump 53R, the traveling motor 36L will be referred to as the left traveling motor 36L, and the traveling motor 36R will be referred to as the right traveling motor 36R. Sometimes.
The left traveling pump 53L and the right traveling pump 53R have a pressure receiving portion 53a and a pressure receiving portion 53b on which the pressure (pilot pressure) of hydraulic oil (pilot oil) from the first hydraulic pump P1 acts. The angle of the swash plate (first swash plate, second swash plate) is changed by the pilot pressure acting on the pressure receiving portions 53a and 53b. By changing the angles of the swash plates (the first swash plate and the second swash plate), the output (discharge amount of hydraulic oil) of the left traveling pump 53L and the right traveling pump 53R and the discharge direction of the hydraulic oil can be changed. .

Here, the pressure receiving portion 53a and the pressure receiving portion 53b of the left traveling pump 53L are collectively referred to as a first pressure receiving portion. Further, the pressure receiving portion 53a and the pressure receiving portion 53b of the right traveling pump 53R are collectively referred to as a second pressure receiving portion.
The left traveling pump 53L has a first port 82a that discharges hydraulic oil when the first swash plate rotates forward, and a second port 82b that discharges hydraulic oil when the first swash plate rotates backward. The right travel pump 53R has a third port 82c that discharges hydraulic fluid when the second swash plate rotates forward, and a fourth port 82d that discharges hydraulic fluid when the second swash plate rotates backward.

The first port 82a and the second port 82b of the left travel pump 53L and the left travel motor 36L are connected by a connection oil passage (first circulation oil passage) 57h, and the hydraulic oil discharged by the left travel pump 53L flows left travel. It is supplied to the motor 36L. The third port 82c and the fourth port 82d of the right travel pump 53R and the right travel motor 36R are connected by a connection oil passage (second circulation oil passage) 57i, and the hydraulic oil discharged by the right travel pump 53R travels to the right. It is supplied to the motor 36R.

A first relief valve 81a is connected to the connection oil passage 57h on the side of the first port 82a of the left traveling pump 53L, and a second relief valve 81a is connected to the oil passage on the side of the second port 82b of the left traveling pump 53L. A relief valve 81b is connected. For example, the first relief valve 81a is likely to operate when the pressure acting on the connecting oil passage 57h increases due to the forward rotation of the left travel pump 53L, and the second relief valve 81b is connected by the reverse rotation of the left travel pump 53L. It is easy to operate when the pressure acting on the oil passage 57h is increased.

A third relief valve 81c is connected to the connection oil passage 57i on the side of the third port 82c of the right traveling pump 53R. A relief valve 81d is connected. For example, the third relief valve 81c is likely to operate when the pressure acting on the connecting oil passage 57i increases due to the forward rotation of the right travel pump 53R, and the fourth relief valve 81d is connected by the reverse rotation of the right travel pump 53R. It is easy to operate when the pressure acting on the oil passage 57i increases.

The left travel motor 36L can be rotated by the hydraulic fluid discharged from the left travel pump 53L, and can change the rotational speed (number of rotations) according to the flow rate of the hydraulic fluid. A swash plate switching cylinder 37L is connected to the left traveling motor 36L, and the rotational speed (number of rotations) of the left traveling motor 36L can be changed by extending or contracting the swash plate switching cylinder 37L to one side or the other. can. That is, when the swash plate switching cylinder 37L is contracted, the rotation speed of the left traveling motor 36L is set to a low speed (first speed), and when the swash plate switching cylinder 37L is extended, the left traveling motor 36L rotates. The number is set to fast (second speed). That is, the rotation speed of the left traveling motor 36L can be changed between the first speed on the low speed side and the second speed on the high speed side.

The right travel motor 36R can be rotated by the hydraulic oil discharged from the right travel pump 53R, and can change the rotational speed (number of rotations) according to the flow rate of the hydraulic oil. A swash plate switching cylinder 37R is connected to the right travel motor 36R, and the rotation speed (number of rotations) of the right travel motor 36R can be changed by extending or contracting the swash plate switching cylinder 37R to one side or the other. can. That is, when the swash plate switching cylinder 37R is contracted, the rotation speed of the right traveling motor 36R is set to a low speed (first speed), and when the swash plate switching cylinder 37R is extended, the rotation of the right traveling motor 36R is reduced. The number is set to fast (second speed). That is, the rotation speed of the right traveling motor 36R can be changed between the first speed on the low speed side and the second speed on the high speed side.

As shown in FIG. 1 , the hydraulic system of the working machine according to this embodiment includes a travel switching valve 34 . The traveling switching valve 34 has a first position where the rotation speed stages (revolution stages) of the traveling motors (the left traveling motor 36L and the right traveling motor 36R) are set to the first speed stage, and a second position where the rotation speed stage is set to the second speed stage. can be switched to The traveling switching valve 34 has first switching valves 71L and 71R and a second switching valve 72 .

The first switching valve 71L is a two-position switching valve that is connected to the swash plate switching cylinder 37L of the left traveling motor 36L via an oil passage and switches between a first position 71L1 and a second position 71L2. The first switching valve 71L contracts the swash plate switching cylinder 37L when it is at the first position 71L1, and extends the swash plate switching cylinder 37L when it is at the second position 71L2.
The first switching valve 71R is a two-position switching valve that is connected to the swash plate switching cylinder 37R of the right traveling motor 36R via an oil passage and switches between a first position 71R1 and a second position 71R2. The first switching valve 71R contracts the swash plate switching cylinder 37R when it is at the first position 71R1, and extends the swash plate switching cylinder 37R when it is at the second position 71R2.

The second switching valve 72 is an electromagnetic valve that switches between the first switching valve 71L and the first switching valve 71R, and is a two-position switching valve that can be switched between a first position 72a and a second position 72b by excitation. The second switching valve 72 , the first switching valve 71</b>L and the first switching valve 71</b>R are connected by an oil passage 41 . The second switching valve 72 switches the first switching valve 71L and the first switching valve 71R to the first positions 71L1 and 71R1, respectively, when it is in the first position 72a, and switches the first switching valve 71L when it is in the second position 72b. and the first switching valve 71R are switched to the second positions 71L2 and 71R2, respectively.

That is, when the traveling switching valve 34 is in the first position, the second switching valve 72 is in the first position 72a, the first switching valve 71L is in the first position 71L1, the first switching valve 71R is in the first position 71R1, and the traveling motor The rotational speed stage of (left traveling motor 36L, right traveling motor 36R) is the first speed stage. When the travel switching valve 34 is in the second state, the second switching valve 72 is in the second position 72b, the first switching valve 71L is in the second position 71L2, the first switching valve 71R is in the second position 71R2, and the traveling motor The rotational speed stage of (left traveling motor 36L, right traveling motor 36R) is the second speed stage.

With such a configuration, the travel switching valve 34 can switch the travel motors (left travel motor 36L, right travel motor 36R) between a first speed on the low speed side and a second speed on the high speed side.
As shown in FIG. 1, the hydraulic system of the working machine according to the present embodiment has brake mechanisms (braking devices) 30R and 30L. The brake mechanism 30R can brake the right travel device 5R, that is, stop the rotation of the right travel motor 36R, which is the HST motor, or the rotation of the output shaft that rotates with the rotation of the HST motor 36R. The brake mechanism 30R changes to a braking state for braking the right travel motor 36R or a release state for releasing the braking by the pilot oil (operating oil) discharged from the first hydraulic pump P1.

For example, the brake mechanism 30R includes a first disk provided on the output shaft of the right travel motor 36R, a movable second disk, and a spring that biases the second disk toward the side that contacts the first disk. I have. The brake mechanism 30 also includes a storage portion (storage case) 59 that stores the first disk, the second disk, and the spring. The portion of the accommodating portion 59 in which the second disc is accommodated and the brake switching valve 80a are connected via an oil passage as will be described later.

The brake switching valve 80a is an electromagnetic valve that performs braking and braking release (braking release) in the brake mechanism 30R, and is a two-position switching valve that can be switched between a first position 83a1 and a second position 83a2. When the brake switching valve 80a is in the first position 83a1, the pressure of the hydraulic oil acting on the brake mechanism 30R (the pressure acting on the housing portion 59) is set to the pressure for the brake mechanism 30R to perform braking. Further, when the brake switching valve 80a is in the second position 83a2, it sets the pressure of the hydraulic oil to the pressure for releasing the braking.

The switching of the brake switching valve 80a is performed under the control of the control device 60. FIG. For example, the control device 60 outputs a control signal for demagnetizing the solenoid of the brake switching valve 80a to set the brake switching valve 80a to the first position 83a1. Further, the control device 60 outputs a control signal that excites the solenoid of the brake switching valve 80a to set the brake switching valve 80a to the second position 83a2. Further, a switch provided on work implement 1 may be used as a trigger for control device 60 to output a control signal to brake switching valve 80a. When the operator manually operates the switch, the control device 60 can detect the operation of the switch and output a control signal. Alternatively, the control device 90 may determine the operating status of the work machine and automatically output the control signal.

Therefore, when the brake switching valve 80a takes the first position 83a1, the pilot oil in the storage portion of the housing portion 59 is discharged, the second disc moves in the direction of braking, and braking in the brake mechanism 30 can be performed. When the brake switching valve 80a takes the second position 83a2, the pilot oil is supplied to the storage portion of the housing portion 59, and the second disc moves in the opposite direction of the braking (opposite direction of the spring biasing direction). , the braking in the braking mechanism 30 can be released.

The configuration of the brake mechanism 30L is similar to that of the brake mechanism 30R. Therefore, the above-described brake mechanism 30R and related configurations can be read as the brake mechanism 30L and related configurations, so the description of the configuration of the brake mechanism 30L is omitted.
The operation device (driving operation device) 54 is a device that applies hydraulic oil to the pressure receiving portions 53a and 53b of the traveling pumps (the left traveling pump 53L and the right traveling pump 53R) when the traveling operation member 59 is operated. The angle of the swash plate of the pump (swash plate angle) can be changed. The operation device 54 includes a travel operation member 59 and a plurality of operation valves 55 (also referred to as operation valves 55). The plurality of operation valves 55 are an operation valve 55A, an operation valve 55B, an operation valve 55C and an operation valve 55D.

The travel operation member 59 is an operation lever that is supported by a plurality of operation valves (operating valves) 55 and swings in the left-right direction (body width direction) or the front-rear direction. That is, when the neutral position N is used as a reference, the travel operation member 59 can be operated to the right and left from the neutral position N, and can be operated forward and backward from the neutral position N. In other words, the travel operation member 59 can swing in at least four directions with the neutral position N as a reference. For convenience of explanation, the front and rear directions, that is, the front and rear directions are referred to as the first direction. Also, the left and right bidirectional directions, that is, the left and right direction (body width direction) may be referred to as the second direction.

Also, the plurality of operation valves 55 are operated by a single traveling operation member 59 in common. The plurality of operation valves 55 are operated based on the swing of the traveling operation member 59 . A discharge oil passage 40 is connected to the plurality of operation valves 55, through which hydraulic oil (pilot oil) can be supplied from the first hydraulic pump P1.
When the traveling operation member 59 is swung forward (one side) in the front-rear direction (first direction) (forward operation), the operation valve 55A outputs an output according to the operation amount (operation) of the forward operation. change the pressure of the hydraulic oil that The operation valve 55B outputs an output according to the operation amount (operation) of the rearward operation when the traveling operation member 59 is swung backward (the other direction) in the front-rear direction (first direction) (rearward operation). change the pressure of the hydraulic oil that

When the traveling operation member 59 is swung to the right (one side) in the left-right direction (second direction) (rightward operation), the operation valve 55C is operated according to the amount of operation (operation) of the rightward operation. to change the pressure of the output hydraulic oil. When the traveling operation member 59 is swung to the left (the other direction) in the left-right direction (second direction) (leftward operation), the operation valve 55D changes the operation amount (operation) of the leftward operation. Accordingly, the pressure of the hydraulic oil to be output is changed.

A plurality of operation valves 55 and the swash plates (first swash plate, second swash plate) of the travel pumps (left travel pump 53L, right travel pump 53R) are connected by a travel oil passage 45 . In other words, the traveling pumps (the left traveling pump 53L, the right traveling pump 53R) are driven by hydraulic oil output from the operation valves 55 (the operation valves 55A, 55B, 55C, and 55D). plate, second swash plate) can be operated.

The traveling oil passage 45 has a first traveling oil passage 45a, a second traveling oil passage 45b, a third traveling oil passage 45c, a fourth traveling oil passage 45d, and a fifth traveling oil passage 45e. The first traveling oil passage 45a is an oil passage connected to the pressure receiving portion (first pressure receiving portion) 53a of the left traveling pump 53L, and when the traveling operation member 59 is operated, the pressure receiving portion (first pressure receiving portion) 53a It is an oil passage through which working hydraulic oil passes. The second traveling oil passage 45b is an oil passage connected to the pressure receiving portion (second pressure receiving portion) 53b of the left traveling pump 53L, and when the traveling operation member 59 is operated, the pressure receiving portion (second pressure receiving portion) 53b It is an oil passage through which working hydraulic oil passes.

The third travel oil passage 45c is an oil passage connected to the pressure receiving portion (third pressure receiving portion) 53a of the right travel pump 53R, and when the travel operation member 59 is operated, the pressure receiving portion (third pressure receiving portion) 53a It is an oil passage through which working hydraulic oil passes. The fourth travel oil passage 45d is an oil passage connected to the pressure receiving portion (fourth pressure receiving portion) 53b of the right travel pump 53R, and when the travel operation member 59 is operated, the pressure receiving portion (fourth pressure receiving portion) 53b It is an oil passage through which working hydraulic oil passes. The fifth travel oil passage 45e is an oil passage that connects the operation valve 55, the first travel oil passage 45a, the second travel oil passage 45b, the third travel oil passage 45c, and the fourth travel oil passage 45d.

When the traveling operation member 59 is swung forward (in the direction of the arrow A1 in FIGS. 1 and 2), the operation valve 55A is operated and the pilot pressure is output from the operation valve 55A. This pilot pressure acts on the pressure receiving portion 53a of the left traveling pump 53L through the first traveling oil passage 45a, and acts on the pressure receiving portion 53a of the right traveling pump 53R through the third traveling oil passage 45c. As a result, the swash plate angles of the left travel pump 53L and the right travel pump 53R are changed, the left travel motor 36L and the right travel motor 36R rotate forward (rotate forward), and the work implement 1 travels straight forward.

Further, when the traveling operation member 59 is swung rearward (in the direction of arrow A2 in FIGS. 1 and 2), the operation valve 55B is operated and the pilot pressure is output from the operation valve 55B. This pilot pressure acts on the pressure receiving portion 53b of the left traveling pump 53L via the second traveling oil passage 45b, and acts on the pressure receiving portion 53b of the right traveling pump 53R via the fourth traveling oil passage 45d. As a result, the swash plate angles of the left traveling pump 53L and the right traveling pump 53R are changed, the left traveling motor 36L and the right traveling motor 36R are reversed (reverse rotation), and the work implement 1 travels straight backward.

Further, when the traveling operation member 59 is swung rightward (in the direction of arrow A3 in FIGS. 1 and 2), the operation valve 55C is operated and the pilot pressure is output from the operation valve 55C. This pilot pressure acts on the pressure receiving portion 53a of the left traveling pump 53L via the first traveling oil passage 45a, and acts on the pressure receiving portion 53b of the right traveling pump 53R via the fourth traveling oil passage 45d. As a result, the swash plate angles of the left traveling pump 53L and the right traveling pump 53R are changed, the left traveling motor 36L rotates forward and the right traveling motor 36R rotates backward, causing the work implement 1 to spin turn to the right. )do.

Further, when the traveling operation member 59 is swung leftward (in the direction of arrow A4 in FIGS. 1 and 2), the operation valve 55D is operated and the pilot pressure is output from the operation valve 55D. This pilot pressure acts on the pressure receiving portion 53a of the right traveling pump 53R through the third traveling oil passage 45c, and acts on the pressure receiving portion 53b of the left traveling pump 53L through the second traveling oil passage 45b. As a result, the swash plate angles of the left traveling pump 53L and the right traveling pump 53R are changed, the left traveling motor 36L rotates in the reverse direction, the right traveling motor 36R rotates in the forward direction, and the work implement 1 spins to the left. )do.

Further, when the traveling operation member 59 is swung in an oblique direction (the arrow A5 direction in FIG. 2), the differential pressure between the pilot pressures acting on the pressure receiving portions 53a and 53b causes the left traveling motor 36L and the right traveling motor 36R to rotate. is determined, and the working machine 1 turns to the right or to the left while moving forward or backward.
That is, when the traveling operation member 59 is swung diagonally forward to the left, the working machine 1 moves forward at a speed corresponding to the swing angle of the traveling operation member 59 and turns to the left. When the travel operation member 59 is swung obliquely forward to the right, the work implement 1 moves forward at a speed corresponding to the swing angle of the travel operation member 59 and turns to the right. When the travel operation member 59 is swung obliquely rearward to the left, the working machine 1 moves backward at a speed corresponding to the swing angle of the travel operation member 59 and turns to the left. When the travel operation member 59 is swung obliquely rearward to the right, the work machine 1 moves backward at a speed corresponding to the swing angle of the travel operation member 59 and turns to the right.

As shown in FIG. 1 , the working machine 1 includes a control device 60 . The control device 60 performs various controls of the work machine 1, and is composed of semiconductors such as a CPU and MPU, electric/electronic circuits, and the like. The control device 60 includes a storage device 63, an accelerator 65, a mode switch 66, a speed changeover switch 67, a rotation speed detection device (motor rotation speed detection device) 68, a measurement device (pressure measurement device) 69, and a setting device. A switch 73 is connected.

A mode switch 66 is a switch for enabling or disabling automatic deceleration. For example, the mode switch 66 is a switch that can be switched ON/OFF. When the mode switch 66 is ON, the automatic deceleration is enabled, and when it is OFF, the automatic deceleration is disabled.
The speed changeover switch 67 is provided near the driver's seat 8 and is operable by the driver (operator). The speed changeover switch 67 is a switch that can manually switch the traveling motors (left traveling motor 36L, right traveling motor 36R) to either the first speed or the second speed. For example, the speed changeover switch 67 is a seesaw switch that can be switched between a position corresponding to the first speed and a position corresponding to the second speed. The speed changeover switch 67 can output an instruction (trigger) for a speedup operation for switching from the first speed to the second speed and a deceleration operation for switching from the second speed to the first speed.

The rotational speed detection device 68 is composed of a sensor or the like for detecting the rotational speed, and can detect the motor rotational speed, which is the rotational speed of the motor 32 .
The measuring device 69 is a sensor that detects the respective pressures of the first relief valve 81a, the second relief valve 81b, the third relief valve 81c, and the fourth relief valve 81d.
The setting switch 73 is a switch for setting (selecting) at least an acquisition mode, which will be described later, among control modes executed by the control device 60 .

Further, the control device 60 performs control to prevent stoppage of the prime mover 32, that is, control to prevent engine stall (that is, anti-stall control). In this embodiment, the anti-stall control means that when the difference between the actual rotation speed detected by the rotation speed detection device 68 (referred to as the drop rotation speed) and the It is to reduce the output of the second running pump 53R). For example, in anti-stall control, the control device 60 prevents engine stall by reducing the outputs of the first traveling pump 53L and the second traveling pump 53R when the drop rotation speed of the prime mover 32 is equal to or greater than a threshold. .

The anti-stall control according to this embodiment will be described in detail below.
As shown in FIG. 1 , the hydraulic system of the working machine has an operating valve 67 . The operating valve 67 is a valve that can change the pilot pressure of the pilot oil that operates the two traveling pumps (the first traveling pump 53L and the second traveling pump 53R). The operating valve 67 is provided in the discharge oil passage 40 through which the pilot oil flows, and by changing the degree of opening, the pilot pressure of the pilot oil that operates the two traveling pumps (the first traveling pump 53L and the second traveling pump 53R). (that is, the operating pilot pressure acting on the pressure receiving portions 53a and 53b) is changed. For example, the operating valve 67 is an electromagnetic proportional valve whose opening can be changed based on a control signal (for example, voltage or current) from the control device 60 .

In other words, the control device 60 excites the solenoid 67a of the operating valve 67 to change the pilot pressure (primary traveling pressure) directed from the operating valve 67 to the operation device 54, thereby controlling the two traveling pumps (first traveling pump 53L, The pilot pressure (operating pilot pressure) for operating the second traveling pump 53R) is changed.
The control device 60 includes an automatic deceleration section 61 . The automatic deceleration unit 61 is a program or the like stored in the control device 60 such as an electric/electronic circuit provided in the control device 60 .
The automatic deceleration unit 61 performs automatic deceleration control when the vehicle is in the running mode and the automatic deceleration is valid, and does not perform the automatic deceleration control when the vehicle is in the running mode and the automatic deceleration is invalid. Also, the automatic deceleration unit 61 does not perform automatic deceleration control in the acquisition mode.

In the automatic deceleration control, when a predetermined condition (automatic deceleration condition) is satisfied while the travel motors (left travel motor 36L, right travel motor 36R) are at the second speed, the controller 60 controls the travel motors (left travel motor 36L, the right travel motor 36R) is automatically switched from the second speed to the first speed. In the automatic deceleration control, when the automatic deceleration condition is satisfied at least when the travel motors (the left travel motor 36L and the right travel motor 36R) are at the second speed, the control device 60 demagnetizes the solenoid of the second switching valve 72. Thus, the second switching valve 72 is switched from the second position 72b to the first position 72a. As a result, the travel motors (left travel motor 36L, right travel motor 36R) decelerate from the second speed to the first speed. That is, in the automatic deceleration control, the control device 60 performs automatic deceleration by decelerating both the left travel motor 36L and the right travel motor 36R from the second speed to the first speed.

Note that, after automatic deceleration, the automatic deceleration unit 61 energizes the solenoid of the second switching valve 72 to move the second switching valve 72 from the first position 72a to the second position 72b when the return condition is satisfied. switch. As a result, the traveling motors (left traveling motor 36L, right traveling motor 36R) are accelerated from the first speed to the second speed, that is, the speed of the traveling motors is restored. That is, when returning from the first speed to the second speed after automatic deceleration, the control device 60 speeds up both the left traveling motor 36L and the right traveling motor 36R from the first speed to the second speed.

When the automatic deceleration is disabled, the control device 60 switches the traveling motors (left traveling motor 36L, right traveling motor 36R) to either the first speed or the second speed according to the operation of the speed changeover switch 67. Perform manual switching control.
In manual switching control, when the speed selector switch 67 is switched to the position corresponding to the first speed, the controller 60 deenergizes the solenoid of the second selector valve 72 to move the second selector valve 72 to the first position 72a. Then, the traveling motors (left traveling motor 36L, right traveling motor 36R) are set to the first speed. In manual switching control, when the speed selector switch 67 is switched to the position corresponding to the second speed, the controller 60 energizes the solenoid of the second selector valve 72 to move the second selector valve 72 to the second position. 72b, and the travel motors (left travel motor 36L, right travel motor 36R) are set to the second speed.

Now, the control device 60 automatically decelerates based on the pressure in the circulation oil passages 57h and 57i. A plurality of pressure detectors 80 are connected to the circulation oil passages 57h and 57i. The multiple pressure detection devices 80 include a first pressure detection device 80a, a second pressure detection device 80b, a third pressure detection device 80c, and a fourth pressure detection device 80d.
The first pressure detection device 80a is provided on the first port P11 side of the left travel motor 36L in the circulation oil passage 57h, and detects the pressure on the first port P11 side as a first travel pressure LF(t). The second pressure detection device 80b is provided on the second port P12 side of the left travel motor 36L in the circulation oil passage 57h, and detects the pressure on the second port P12 side as a second travel pressure LB(t).

The third pressure detection device 80c is provided on the third port P13 side of the right travel motor 36R in the circulation oil passage 57i, and detects the pressure on the third port P13 side as a third travel pressure RF(t). The fourth pressure detection device 80d is provided on the fourth port P14 side of the right travel motor 36R in the circulation oil passage 57i, and detects the pressure on the fourth port P14 side as a fourth travel pressure RB(t).

The control device 60 (automatic deceleration unit 61) detects the first running pressure LF (t, rpm) detected by the first pressure detection device 80a and the second running pressure LB (t, rpm) detected by the second pressure detection device 80b. , the third traveling pressure RF(t, rpm) detected by the third pressure detecting device 80c and the fourth traveling pressure RB(t, rpm) detected by the fourth pressure detecting device 80d. Note that the first running pressure LF (t, rpm), the second running pressure LB (t, rpm), the third running pressure RF (t, rpm), and the fourth running pressure RB (t, rpm) ( t, rpm) indicates that it is a value associated with the actual number of revolutions of the prime mover at a certain time t.

Specifically, the automatic deceleration unit 61, as shown in equation (1), first travel pressure LF (t, rpm), second travel pressure LB (t, rpm), third travel pressure RF (t, rpm) rpm), and the fourth running pressure RB(t, rpm) becomes equal to or greater than the deceleration threshold ST(rpm) determined according to the number of rotations of the prime mover, automatic deceleration is performed.

The control device 60 (automatic deceleration unit 61) controls the first travel relief pressure w1 of the first relief valve 81a, the second travel relief pressure w2 of the second relief valve 81b, the third travel relief pressure w2 of the third relief valve 81c, A deceleration threshold ST (rpm) is set based on w3 and the fourth travel relief pressure w4 of the fourth relief valve 81d. For example, the control device 60 (automatic deceleration unit 61) decelerates using the first travel relief pressure w1, the second travel relief pressure w2, the third travel relief pressure w3, the fourth travel relief pressure w4 and the correction coefficient _η1 . Set the threshold ST (rpm).

For convenience of explanation, the first travel relief pressure w1 determined corresponding to the engine speed is the first travel relief pressure w1 (rpm), and the second travel relief pressure w2 is the second travel relief pressure w2 (rpm). ), the third travel relief pressure w3 is denoted by the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 is denoted by the fourth travel relief pressure w4 (rpm).

The deceleration threshold value ST set by the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm). is represented by the deceleration threshold ST (rpm). In setting the deceleration threshold ST (rpm), the control device 60 (automatic deceleration unit 61) sets the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), The third travel relief pressure w3 (rpm) and the fourth travel relief pressure w4 (rpm) are referred to. Also, η ₁ in Equation (2) is a correction coefficient. As shown in equation (2), the control device 60 (automatic deceleration unit 61) controls the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), The deceleration threshold value ST (rpm) is set by multiplying each of the fourth travel relief pressures w4 (rpm) by the correction coefficient _η1 .

At this time, in order to perform accurate automatic deceleration using the deceleration threshold ST (rpm), accurate first travel relief pressure w1, second travel relief pressure w2, third travel relief pressure w3, and fourth travel relief pressure It is necessary to obtain the pressure w4. Therefore, as described above, the control device 60 operates in the acquisition mode for acquiring the first travel relief pressure w1, the second travel relief pressure w2, the third travel relief pressure w3, and the fourth travel relief pressure w4. have.

The acquisition mode executed by the control device 60 (automatic deceleration unit 61) will be described below. When the control device 60 (automatic deceleration unit 61) executes the acquisition mode, first, while changing the engine rotation speed to different engine rotation speeds, the first travel relief pressure w1 and the second travel relief pressure w1 are set for each engine rotation speed. w2, third travel relief pressure w3, and fourth travel relief pressure w4 are acquired. That is, the control device 60 (automatic deceleration unit 61) sets travel relief pressures (first travel relief pressure w1, second travel relief pressure w2, third travel relief pressure w3, fourth Acquire the travel relief pressure w4). Then, the control device 60 (automatic deceleration section 61) sets the deceleration threshold value ST (rpm) in accordance with the travel relief pressure determined corresponding to the engine speed. The travel relief pressure is the pressure of hydraulic oil when the first relief valve 81a, the second relief valve 81b, the third relief valve 81c, and the fourth relief valve 81d start to open, or the pressure of the first relief valve 81a, This is the pressure of hydraulic fluid when the discharge flow rate from the traveling pumps 53L and 53R stabilizes after the second relief valve 81b, the third relief valve 81c and the fourth relief valve 81d start to open.

More specifically, in the acquisition mode, the control device 60 (automatic deceleration unit 61) sets the engine speed to a predetermined speed. The measuring device 69 (see FIG. 1) measures the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), and the third travel relief pressure w3 (rpm) when the number of revolutions of the prime mover is a predetermined number of revolutions. and the fourth travel relief pressure w4 (rpm).
In the acquisition mode, the control device 60 (automatic deceleration unit 61) changes the motor rotation speed in a range from at least the rotation speed corresponding to idling to the upper limit rotation speed, and performs the first travel for each changed motor rotation speed. The relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm) and the fourth travel relief pressure w4 (rpm) are measured.

As shown in FIG. 3, in the acquisition mode, the storage device 63 stores a first travel relief pressure w1 (rpm), a second travel relief pressure w2 (rpm), a third travel relief pressure w3 ( rpm) and the fourth travel relief pressure w4 (rpm). That is, the storage device 63 stores the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w3 (rpm) for one motor rotation speed. One set of relief pressure w4 (rpm) is associated and stored.

The operation of the control device 60 in the acquisition mode, that is, the operation of the work implement 1 will be described in more detail with reference to FIG. FIG. 4 is a flow chart showing the flow of processing in the acquisition mode.
The acquisition mode is control that can be started in a state (idling state) in which the work implement 1 is parked on a flat ground, the prime mover 32 is in operation, and the speed is at idling. In this idling state, the brake switching valve 80a is in the first position 83a1, and the braking of the brake mechanisms 30L and 30R is released. In addition, since the second switching valve 72 of the traveling switching valve 34 is at the first position 72a, the first switching valve 71L is at the first position 71L1, the first switching valve 71R is at the first position 71R1, and the traveling motor (left The rotation speed stage of the traveling motor 36L, the right traveling motor 36R) is the first speed stage.

When the acquisition mode is selected by the setting switch 73 when the prime mover 32 is in the idling state (step S1), the control device 60 (automatic deceleration section 61) starts control in the acquisition mode (step S2).
In the acquisition mode, the control device 60 (automatic deceleration unit 61) first outputs a control signal to the brake switching valve 80a to excite the solenoid of the brake switching valve 80a. Due to this excitation, the brake switching valve 80a is switched to the first position 83a1, and braking is performed in the brake mechanisms 30L and 30R. That is, the brake mechanisms 30L, 30R brake (parking lock) the travel motors 36L, 36R (step S3).

After step S<b>3 , the control device 60 (automatic deceleration section 61 ) outputs a control signal to the second switching valve 72 of the travel switching valve 34 to excite the solenoid of the second switching valve 72 . This excitation switches the second switching valve 72 to the second position 72b, switches the first switching valve 71L to the second position 71L2, and switches the first switching valve 71R to the second position 71R2. That is, the rotation speed stage of the traveling motors (left traveling motor 36L, right traveling motor 36R) becomes the second speed stage (step S4).

After step S4, control device 60 starts anti-stall control for preventing engine stall of prime mover 32 (step S5). Anti-stall control is a technique for preventing engine stall of the prime mover 32 by controlling an anti-stall proportional valve and an unload valve.
After step S5, the control device 60 increases the rotation speed of the prime mover 32 to a predetermined rotation speed (eg, 700 rpm) (step S6).

After step S6, when the rotational speed of the prime mover 32 stabilizes at a predetermined rotational speed, the control device 60 controls the hydraulic oil output from the operation valves 55 (the operation valves 55A, 55B, 55C, and 55D). (pilot pressure) to tilt the swash plates of the traveling pumps (the left traveling pump 53L and the right traveling pump 53R) at the upper limit pilot pressure for the rotational speed (step S7).

As a result, the traveling pumps (the left traveling pump 53L, the right traveling pump 53R) supply the traveling motors (the left traveling motor 36L, the right traveling motor 36R) with a prescribed flow rate of hydraulic oil.
After step S7, the measuring device 69 connected to the control device 60 measures the first travel relief pressure w1 (rpm) and the second travel relief pressure w2 (rpm) of the travel pumps (left travel pump 53L, right travel pump 53R). , the measurement of the third travel relief pressure w3 (rpm) and the fourth travel relief pressure w4 (rpm) is started (step S8).

After step S8, the measuring device 69 measures the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm). starts to occur, when the discharge flow rate of hydraulic oil from the traveling pumps (left traveling pump 53L, right traveling pump 53R) stabilizes, the first travel relief pressure w1 (rpm) and the second The travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm) are acquired (step S9).

After step S9, the storage device 63 connected to the control device 60 stores the acquired first travel relief pressure w1 (rpm), second travel relief pressure w2 (rpm), third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm) are stored in association with the number of revolutions of the engine when the travel relief pressure was measured (step S10).
By the processing in step S10, the storage device 63 stores a set of the first travel relief pressure, the second travel relief pressure, the third travel relief pressure, and the fourth travel relief pressure corresponding to the engine speed, as shown in FIG. memorize

After step S9, the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm) are ) needs to be measured (step S11), the control device 60 returns the process to step S6, and if the measurement is not needed, ends the acquisition mode.
The acquisition mode consisting of steps S1 to S10 described above is executed in work machine 1 in which the traveling pumps (left traveling pump 53L, right traveling pump 53R) are driven by prime mover 32 .
In addition, in step S7, it was explained that the control device 60 controls the pressure (pilot pressure) of the hydraulic oil output from the operation valves 55 (the operation valves 55A, 55B, 55C, and 55D). At this time, the control device 60 sequentially operates the operation valve 55A, the operation valve 55B, the operation valve 55C, and the operation valve 55D.

When the operation valve 55A is operated, the traveling pumps (left traveling pump 53L, right traveling pump 53L, The swash plate of the pump 53R) can be tilted. When the operation valve 55B is operated, the traveling pumps (left traveling pump 53L, right traveling pump 53L, right traveling pump 53L, right traveling pump 53L, and right traveling pump 53L) are operated at the upper limit pilot pressure for the rotation speed by the hydraulic oil pressure (pilot pressure) output when the operation valve 55B is operated. The swash plate of the pump 53R) can be tilted. When the operation valve 55C is operated, the traveling pumps (left traveling pump 53L, right traveling pump 53L, The swash plate of the pump 53R) can be tilted. Further, when the operation valve 55D is operated, the traveling pumps (the left traveling pump 53L, the left traveling pump 53L, the left traveling pump 53L, The swash plate of the right traveling pump 53R) can be tilted.

Furthermore, when the operation valves 55A and 55C are operated, the hydraulic oil pressure (pilot pressure) output when the operation valves 55A and 55C are operated causes the traveling pump (left The swash plates of the traveling pump 53L and the right traveling pump 53R) can be tilted. When the operation valves 55A and 55D are operated, the traveling pump (left traveling pump 53L, the swash plate of the right running pump 53R) can be tilted. When the operation valves 55B and 55C are operated, the traveling pump (left traveling pump 53L, the swash plate of the right running pump 53R) can be tilted. Further, when the operation valves 55B and 55D are operated, the hydraulic oil pressure (pilot pressure) output when the operation valves 55B and 55D are operated causes the traveling pump (left The swash plates of the traveling pump 53L and the right traveling pump 53R) can be tilted.

Thus, in step S7, one or two of the operation valves 55 (the operation valve 55A, the operation valve 55B, the operation valve 55C, and the operation valve 55D) are operated to output hydraulic oil. , is operated by swinging of the traveling operation member 59 . Therefore, in order to operate one or two operation valves 55 to be operated, the control device 60 displays the swing direction of the traveling operation member 59 on a monitor (display device) or the like provided around the driver's seat 8. indicate. An operator who visually recognizes this monitor swings the traveling operation member 59 according to the display on the monitor.

Through the above operations, in each combination of one or two operation valves 55, the travel pumps (left travel pump 53L, right travel pump 53R) send the travel motors (left travel motor 36L, right travel motor 36R) to the specified flow rate. Hydraulic oil is supplied.
In subsequent step S8, the measuring device 69 connected to the control device 60 measures the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w3 (rpm). Measurement of the relief pressure w4 (rpm) is started.

For example, in step S7 of the flow chart shown in FIG. 4, the control device 60 displays the rocking direction of the traveling operation member 59 for operating the operation valve 55A on the monitor (display device). After that, when the operation valve 55A is operated by swinging the travel operation member 59, the control device 60 obtains and stores the first to fourth travel relief pressures w1 to w4 (rpm) through steps S8 to S10. In step S11, if it is necessary to measure the traveling relief pressure when the operation valve 55 different from the operation valve 55A is operated, the control device 60 returns the process to step S7.

After returning to step S7, the control device 60 displays on the monitor (display device) the swinging direction of the traveling operation member 59 for operating the operation valve 55B different from the operation valve 55A, for example, and repeats the above operation. . Thus, by repeating steps S7 to S11, the control device 60 acquires and stores the first to fourth traveling relief pressures w1 to w4 (rpm) when one or two operation valves 55 are operated. do.

(Modification)
An acquisition mode (hereinafter referred to as a second acquisition mode) when the traveling pumps (the left traveling pump 53L, the right traveling pump 53R) of the work implement 1 are composed of electric HSTs will be described below. Here, both the first hydraulic pump P1 and the second hydraulic pump P2 are constituted by electric hydraulic pumps.
The operation of the control device 60 in the second acquisition mode, that is, the operation of the work implement 1 will be described in more detail with reference to FIG. FIG. 5 is a flow chart showing the flow of processing in the second acquisition mode.

The second acquisition mode is a control that can be started on the condition that the work implement 1 is parked on flat ground in an operable state. At this time, the brake switching valve 80a is at the first position 83a1, and the braking of the brake mechanisms 30L and 30R is released. In addition, since the second switching valve 72 of the traveling switching valve 34 is at the first position 72a, the first switching valve 71L is at the first position 71L1, the first switching valve 71R is at the first position 71R1, and the traveling motor (left The rotation speed stage of the traveling motor 36L, the right traveling motor 36R) is the first speed stage.

When the acquisition mode is selected by the setting switch 73 (step S20), the control device 60 (automatic deceleration unit 61) starts control in the acquisition mode (step S21).
In the acquisition mode, the control device 60 (automatic deceleration unit 61) first outputs a control signal to the brake switching valve 80a to excite the solenoid of the brake switching valve 80a. Due to this excitation, the brake switching valve 80a is switched to the first position 83a1, and braking is performed in the brake mechanisms 30L and 30R. In other words, the brake mechanisms 30L and 30R brake the traveling motors 36L and 36R (referred to as parking lock) (step S22).

After step S<b>22 , the control device 60 (automatic deceleration section 61 ) outputs a control signal to the second switching valve 72 of the travel switching valve 34 to excite the solenoid of the second switching valve 72 . This excitation switches the second switching valve 72 to the second position 72b, switches the first switching valve 71L to the second position 71L2, and switches the first switching valve 71R to the second position 71R2. That is, the rotation speed stage of the traveling motors (left traveling motor 36L, right traveling motor 36R) becomes the second speed stage (step S23).
After step S23, the controller 60 increases the rotational speeds of the electric HST pumps (left traveling pump 53L, right traveling pump 53R) to a predetermined rotational speed (eg, 700 rpm) (step S24).

After step S24, when the rotational speeds of the electric HST pumps (the left traveling pump 53L, the right traveling pump 53R) stabilize at a predetermined rotational speed, the control device 60 controls the operation valves 55 (the operation valves 55A, 55B, 55B, and 55B). 55C, operation valve 55D) to control the hydraulic oil pressure (pilot pressure) output from the output, and the electric HST pump (left traveling pump 53L, right traveling pump 53R) is tilted at the upper limit pilot pressure at the rotational speed. The plate is tilted (step S25).
As a result, the traveling pumps (the left traveling pump 53L, the right traveling pump 53R) supply the traveling motors (the left traveling motor 36L, the right traveling motor 36R) with a prescribed flow rate of hydraulic oil.

After step S25, the measuring device 69 connected to the control device 60 measures the first travel relief pressure w1 (rpm) and the second travel relief pressure w2 (rpm) of the travel pumps (left travel pump 53L, right travel pump 53R). , the measurement of the third travel relief pressure w3 (rpm) and the fourth travel relief pressure w4 (rpm) is started (step S26).
After step S26, the measuring device 69 measures the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm). starts to occur, when the discharge flow rate of hydraulic oil from the traveling pumps (left traveling pump 53L, right traveling pump 53R) stabilizes, the first travel relief pressure w1 (rpm) and the second The travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm) are obtained (step S27).

After step S27, the storage device 63 connected to the control device 60 stores the measured first travel relief pressure w1 (rpm), second travel relief pressure w2 (rpm), third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm) are stored in association with the number of revolutions of the engine when the travel relief pressure was measured (step S28).
By the processing of step S28, the storage device 63 stores the first travel relief pressure, the second travel relief pressure, the third travel relief pressure corresponding to the rotation speed of the travel pumps (the left travel pump 53L, the right travel pump 53R), and the A set of four travel relief pressures is stored to obtain information similar to that of FIG.

After step S27, the first travel relief pressure w1 (rpm), the second travel relief pressure w2 (rpm), the third travel relief pressure w3 (rpm), and the fourth travel relief pressure w4 (rpm) are ) needs to be measured (step S29), the control device 60 returns the process to step S24, and if the measurement is not required, ends the acquisition mode.
According to the above-described embodiment and example, the driving motors 36L and 36R are braked (parking locked) in steps S3 and S22 in the acquisition mode. Since the rotational speed stage of the motor 36R) is switched to the second speed stage, the rotational torque of the traveling motor with respect to the same load pressure due to hydraulic oil is increased compared to the case where the rotational speed stage of the traveling motor is the first speed stage. can be reduced. This decrease in rotational torque reduces the load applied to the brake mechanisms 30L and 30R.

In the above description of the embodiment and modifications, the automatic deceleration unit 61 executes the acquisition mode. However, instead of the automatic deceleration section 61, the control device 60 may have a computer program or an electronic circuit that independently executes the acquisition mode independently of the automatic deceleration.
If the control device 60 has a configuration that allows the acquisition mode to be executed independently of automatic deceleration, for example, even if the HST pump or underbody parts are replaced at a dealer, etc., special equipment can be introduced. It is possible to measure the travel relief pressure for each work implement 1 without doing so.

(Second embodiment)
A second embodiment of the present invention will be described below with reference to FIG. FIG. 6 is a diagram showing part of the hydraulic system (hydraulic circuit) of the working machine according to the second embodiment of the present invention. In this embodiment, the same reference numerals are given to the same constituent elements as those explained in the first embodiment, and the explanation thereof will be omitted.

Although not shown, the left traveling pump 53L is connected to the connection oil passage (first circulation oil passage) 57h, and the right traveling pump 53R is connected to the connection oil passage (second circulation oil passage) 57i, as in FIG. 1 according to the first embodiment. It is connected to the. Further, the connecting oil passage 57h is provided with first and second relief valves 81a and 81b, and the connecting oil passage 57i is provided with third and fourth relief valves 81c and 81d.
In the first embodiment, the operating device 54 is of a hydraulic type in which the operating lever 59 and the operating valve 55 change the pilot pressure acting on the traveling pumps (the first traveling pump 53L and the second traveling pump 53R).

As shown in FIG. 6, in the second embodiment, an operation lever 59 composed of an electrically operated joystick and a control device 60, which will be described later, are employed, and an operation valve (operating valve) 55 composed of an electromagnetic proportional valve is used. (operation valves 55a, 55b, 55c, 55d) are adopted. The operation lever 59 is an operation lever that swings in the left-right direction (body width direction) or the front-rear direction. The operation lever 59 has a sensor (operation detection sensor) that detects an operation amount (swing amount) and an operation direction (swing direction). This operation detection sensor is connected to the control device 60 .
The control device 60 outputs a control signal to the operation valves (operation valves) 55 (operation valves 55a, 55b, 55c, 55d) according to the operation amount and the operation direction of the operation lever 59 output by the operation detection sensor. The operating valves 55 (operating valves 55a, 55b, 55c, 55d) are assigned to the operating directions of the operating lever 59 (directions A1 to A4 shown in FIG. 2).

In this embodiment, the operation valves 55 (operation valves 55A, 55B, 55C, 55A, 55B, 55C, 55A, 55B, 55C) according to the first embodiment are operated by operating the operation valves 55 (operation valves 55a, 55b, 55c, 55d) using the operation lever 59 and the control device 60. 55D).
The technology and configuration for measuring the travel relief pressure in the above-described configuration according to this embodiment are the same as the technology and configuration described in the first embodiment using FIGS. By replacing the operation valves 55 (the operation valves 55A, 55B, 55C, and 55D) with the operation valves 55 (the operation valves 55a, 55b, 55c, and 55d), the travel relief pressure can be measured in the same manner as in the first embodiment. .

(Third Embodiment)
A third embodiment of the present invention will be described below with reference to FIGS. FIG. 7 is a diagram showing part of a hydraulic system (hydraulic circuit) of a working machine according to a third embodiment of the present invention. In this embodiment, the same reference numerals are given to the same constituent elements as those explained in the first and second embodiments, and the explanation thereof will be omitted.

Although not shown in FIG. 7, similar to FIG. 6, the third embodiment employs an operating lever 59 and a control device 60 which are configured by an electrically operated joystick. In this embodiment, instead of the operation valve 55 (operation valves 55a, 55b, 55c, 55d) shown in FIG. 156L and 156R are adopted.

As in the second embodiment, the control lever 59 is a control lever that swings in the left-right direction (body width direction) or in the front-rear direction. The operation lever 59 has a sensor (operation detection sensor) that detects an operation amount (swing amount) and an operation direction (swing direction). This operation detection sensor is connected to the control device 60 .
Operation valves (operating valves) 155L and 155R, which are electromagnetic proportional valves, are electrically connected to the control device 60 . Similarly to the operation valves 55 (operation valves 55a, 55b, 55c, 55d) according to the second embodiment, the operation valves 155L, 155R are controlled by the control signal from the control device 60 according to the operation of the operation lever 59. are controlled.

As shown in FIG. 7, the hydraulic regulators 156L and 156R are connected to the swash plates of the travel pumps (the first travel pump 53L and the second travel pump 53R), respectively. Each of the hydraulic regulators 156L, 156R can change the angle of the swash plate (swash plate angle) of the travel pumps 53L, 53R (the first travel pump 53L, the second travel pump 53R), and is supplied with hydraulic oil. It includes a feed chamber 157 and a piston rod 158 mounted in the feed chamber 157 . The piston rod 158 is connected to the swash plate, and movement (that is, extension and contraction) of the piston rod 158 causes the swash plate to swing and change the swash plate angle.

Here, the supply chamber 157 of the hydraulic regulator 156L connected to the swash plate of the left traveling pump 53L is called a first pressure receiving portion. Also, the supply chamber 157 of the hydraulic regulator 156R connected to the swash plate of the right travel pump 53R is called a second pressure receiving portion.
The operation valve 155L is a valve that operates the hydraulic regulator 156L, and is a valve that controls the amount of hydraulic oil output by the travel pump 53L by operating the hydraulic regulator 156L. The operation valve 155L is composed of an electromagnetic proportional valve having a solenoid 160L, and the spool of the operation valve 155L moves based on a control signal output from the control device 60 to the solenoid 160L. This movement of the spool changes the opening of the operation valve 155L. The operation valve 155L has a first position 159a, a second position 159b, and a neutral position 159c, and can be switched to any position.

The first port of the operation valve 155L and the supply chamber 157 of the hydraulic regulator 156L are connected by the first travel oil passage 45a. The second port of the operation valve 155L and the supply chamber 157 of the hydraulic regulator 156L are connected by a second travel oil passage 45b.
The operation valve 155R is a valve that operates the hydraulic regulator 156R, and is a valve that controls the amount of hydraulic oil output by the traveling pump 53R by operating the hydraulic regulator 156R. The operation valve 155R is composed of an electromagnetic proportional valve having a solenoid 160R, and the spool of the operation valve 155R is moved based on a control signal given from the control device 60 to the solenoid 160R. This movement of the spool changes the opening of the operation valve 155R. The operation valve 155R has a first position 159a, a second position 159b, and a neutral position 159c, and can be switched to any position.

The first port of the operation valve 155R and the supply chamber 157 of the hydraulic regulator 156R are connected by a third travel oil passage 45c. The second port of the operation valve 155R and the supply chamber 157 of the hydraulic regulator 156R are connected by a fourth travel oil passage 45d.
When the operating valves 155L and 155R are switched to the first position 159a, the hydraulic regulators 156L and 156R are actuated to swing the swash plates of the traveling pumps 53L and 53R, causing the traveling pumps to rotate forward. When the operating valve 155L and the operating valve 155R are switched to the second position 159b, the hydraulic regulators 156L and 156R are actuated to swing the swash plates of the traveling pumps 53L and 53R, thereby rotating the traveling pumps in reverse.

By switching the operating valve 155L to the first position 159a and switching the operating valve 155R to the second position 159b, the first traveling pump 53L rotates forward and the second traveling pump 53R rotates in the reverse direction. By switching the operating valve 155L to the second position 159b and switching the operating valve 155R to the first position 159a, the first traveling pump 53L rotates in the reverse direction and the second traveling pump 53R rotates in the forward direction.
In this embodiment, the operation valve 155L and the operation valve 155R are operated by the operation lever 59 and the control device 60 to operate the hydraulic regulators 156L and 156R, and the travel pumps 53L and 53R are tilted as in the second embodiment. Rock the plate.

Therefore, the technology and configuration for measuring the travel relief pressure with the above-described configuration according to this embodiment are the same as the technology and configuration described in the second embodiment using FIG. By replacing the operation valve 55 (operation valves 55a and 55b) with an operation valve 155L and a hydraulic regulator 156L and replacing the operation valve 55 (operation valves 55c and 55d) with an operation valve 155R and a hydraulic regulator 156R, the same operation as in the second embodiment is performed. can measure the running relief pressure.

In the first to third embodiments described above, the control device 60 executes braking by the brake mechanisms (braking devices) 30R and 30L, and at least one of the left traveling motor 36L and the right traveling motor 36R is switched to the second speed. , and in a state in which hydraulic oil is being supplied to the traveling oil passages 45a to 45d by the operation valve 55 or 155, the rotational speed of the prime mover 32 is increased or decreased. By increasing or decreasing the rotational speed of the prime mover 32, the pressure of hydraulic fluid supplied from the operation valve 55 or 155 to the travel oil passages 45a-45d can be changed. As a result, the controller 60 can detect the actual rotation speed of the prime mover 32 at which the relief valves 81a to 81d begin to open, using the prime mover rotation speed detector 68. FIG.

At this time, the control device 60 associates and stores the current value of the control signal to be output to the operation valve 55 or 155 and the number of rotations of the motor that has decreased due to the load.
Further, when the acquisition mode is canceled, the control device 60 switches the left traveling motor 36L and/or the right traveling motor 36R from the second speed to the first speed, and brakes the brake mechanisms (braking devices) 30R and 30L. unlock. As a result, the work implement 1 can perform normal operation based on the new relief pressure.

In the above-described first to third embodiments, the speed stage of the traveling motor is exemplified by the two stages of the first speed and the second speed, which is higher than the first speed. However, the speed stage of the traveling motor may be three or more stages. The gist of the present invention and the embodiments described above is to measure travel relief pressure using a speed stage higher than the first speed. Therefore, even in a work machine having speed stages such as a third speed higher than the second speed and a fourth speed higher than the third speed, instead of the second speed in each of the above-described embodiments, the third speed By applying the speed and the fourth speed, similar control can be performed to measure the travel relief pressure.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

1 work machine 2 machine body 5L left travel device 5R right travel device 36L left travel motor 36R right travel motor 57h first circulation oil passage (connection oil passage)
57i second circulation oil passage (connection oil passage)
60 Control device 80a First pressure detection device 80b Second pressure detection device 80c Third pressure detection device 80d Fourth pressure detection device 81a First relief valve 81b Second relief valve 81c Fourth relief valve 81d Fourth relief valve 83a Brake switching valve

Claims (15)

Airframe and
a prime mover provided in the airframe;
a left running device provided on the left side of the fuselage;
a right travel device provided on the right side of the fuselage;
a left travel motor capable of transmitting power to the left travel device and switchable between a first speed and a second speed higher than the first speed;
a right travel motor capable of transmitting power to the right travel device and switchable between a first speed and a second speed higher than the first speed;
a left traveling pump having a first port for discharging hydraulic oil during forward rotation and a second port for discharging hydraulic oil during reverse rotation;
a right traveling pump having a third port for discharging hydraulic oil during forward rotation and a fourth port for discharging hydraulic oil during reverse rotation;
a first circulation oil passage connected to the first port and the second port of the left travel pump and to the left travel motor;
a second circulation oil passage connected to the third port and the fourth port of the right travel pump and connected to the right travel motor;
a braking device that brakes the left travel motor and the right travel motor;
a pressure measuring device that measures the pressure of hydraulic fluid in the first and second circulation oil passages;
When braking is performed by the braking device and the left travel motor and the right travel motor are at the second speed, the pressure measurement device measures the pressure of the first circulation oil passage and the second circulation oil passage. and a control device that acquires the pressure of hydraulic oil. switchable between a first position and a second position, setting the left travel motor and the right travel motor to the first speed when at the first position, and setting the left travel motor at the second position; and a travel switching valve that switches the right travel motor to the second speed;
a control device that controls the travel switching valve and the braking device;
with
2. The work according to claim 1, wherein the control device switches the travel switching valve to the second position and performs braking of the braking device when executing an acquisition mode for acquiring the pressure of the hydraulic fluid. machine. The control device is capable of switching the travel switching valve to the first position or the second position when the acquisition mode is not being executed, and is capable of braking or releasing the braking to the braking device. The working machine according to claim 2. a travel operation device that applies hydraulic oil to either the left travel pump or the right travel pump when the travel operation member is operated;
a travel oil passage that connects the travel operation device and the left travel pump and the right travel pump and through which the hydraulic oil flows;
and an operating valve that controls the operating oil supplied to the traveling oil passage,
After executing braking by the braking device and switching the left travel motor and the right travel motor to a second speed, the control device controls the operating valve to supply hydraulic fluid to the travel oil passage. The work machine according to any one of claims 1 to 3, which performs When the acquisition mode is not executed, the control device changes the speed from the second speed to the first speed based on the pressure of hydraulic fluid in either the first oil circulation passage or the second oil circulation passage. The work machine according to any one of claims 1 to 4, wherein switching is performed. Airframe and
a left running device provided on the left side of the fuselage;
a right travel device provided on the right side of the fuselage;
a left travel motor capable of transmitting power to the left travel device and switchable between a first speed and a second speed higher than the first speed;
a right travel motor capable of transmitting power to the right travel device and switchable between a first speed and a second speed higher than the first speed;
It has a first port that discharges hydraulic fluid during forward rotation and a second port that discharges hydraulic fluid during reverse rotation, and has a first pressure receiving portion on which pressure acts, and responds to the pressure acting on the first pressure receiving portion. a left traveling pump that discharges the hydraulic oil from the first port or the second port;
It has a third port that discharges hydraulic fluid during forward rotation and a fourth port that discharges hydraulic fluid during reverse rotation. a right traveling pump that discharges the hydraulic oil from the third port or the fourth port;
a braking device that brakes the left travel motor and the right travel motor;
a traveling oil passage connected to the first pressure receiving portion of the left traveling pump and the second pressure receiving portion of the right traveling pump and through which the hydraulic oil flows;
an operating valve that controls the operating oil supplied to the traveling oil passage;
When operating the operating valve to supply operating oil to the traveling oil passage in a state in which braking is being performed by the braking device, the left traveling motor and the right motor are operated before operating the operating valve. and a control device that switches at least one of to the second speed. Airframe and
a left running device provided on the left side of the fuselage;
a right travel device provided on the right side of the fuselage;
a left travel motor capable of transmitting power to the left travel device and switchable between a first speed and a second speed higher than the first speed;
a right travel motor capable of transmitting power to the right travel device and switchable between a first speed and a second speed higher than the first speed;
It has a first port that discharges hydraulic fluid during forward rotation and a second port that discharges hydraulic fluid during reverse rotation, and has a first pressure receiving portion on which pressure acts, and responds to the pressure acting on the first pressure receiving portion. a left traveling pump that discharges the hydraulic oil from the first port or the second port;
It has a third port that discharges hydraulic fluid during forward rotation and a fourth port that discharges hydraulic fluid during reverse rotation. a right traveling pump that discharges the hydraulic oil from the third port or the fourth port;
a braking device that brakes the left travel motor and the right travel motor;
a traveling oil passage connected to the first pressure receiving portion of the left traveling pump and the second pressure receiving portion of the right traveling pump and through which the hydraulic oil flows;
an operating valve that controls the operating oil supplied to the traveling oil passage;
and a control device that prohibits the operation of the operating valve when the left traveling motor and the right motor are at the first speed in a state in which braking is being performed by the braking device. The control device increases hydraulic oil supplied to the traveling oil passage in a state in which braking is performed by the braking device and at least one of the left traveling motor and the right traveling motor is switched to the second speed. 8. The work machine according to claim 6 or 7, wherein the actuating valve is operated to reduce or reduce the equipped with a prime mover,
The control device executes braking by the braking device, at least one of the left travel motor and the right travel motor is switched to the second speed, and hydraulic oil is supplied to the travel oil passage by the operation valve. The working machine according to any one of claims 6 to 8, wherein the number of revolutions of the prime mover is increased or decreased in a state where the engine is in a state of being held. The control device switches at least one of the left travel motor and the right travel motor to the second speed when executing an acquisition mode for acquiring the pressure of hydraulic fluid supplied to the travel oil passage, The working machine according to claim 6 or 7, wherein braking is performed by said braking device. a first circulation oil passage connected to the first port and the second port of the left travel pump and to the left travel motor;
a second circulation oil passage connected to the third port and the fourth port of the right travel pump and connected to the right travel motor;
a pressure measuring device that measures the pressure of the hydraulic oil in the first circulation oil passage and the second circulation oil passage,
The working machine according to any one of claims 6 to 10, wherein the control device acquires the hydraulic oil pressure measured by the pressure measuring device. The work machine according to any one of claims 6 to 11, further comprising a prime mover rotation speed detection device that acquires the actual revolution speed of the prime mover. 10. When the acquisition mode is canceled, the control device switches the left travel motor and/or the right travel motor from the second speed to the first speed and releases the braking by the braking device. The working machine described in . When a predetermined condition is satisfied when at least one of the left travel motor and the right travel motor is at the second speed, the control device controls the left travel motor and/or the right travel motor at the second speed. has an automatic deceleration unit that executes automatic deceleration control for automatically switching from the second speed to the first speed,
The working machine according to claim 10, wherein the control device does not execute the automatic deceleration control when executing the acquisition mode. The actuated valve is composed of a plurality of actuated valves,
When the acquisition mode is executed, the control device acquires the pressure of the hydraulic fluid supplied to the traveling oil passage by the operation of at least one of the plurality of operation valves, and then acquires the pressure of the remaining hydraulic fluid. 11. The working machine according to claim 10, wherein the pressure of the hydraulic oil supplied to the traveling oil passage is obtained by operating at least one operating valve among the operating valves.

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