JP7293285B2 - Travel system hydraulic circuit and travel control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to hydraulic systems for work machines such as skid steer loaders, compact track loaders, and backhoes.

2. Description of the Related Art Conventionally, Patent Documents 1 and 2 disclose techniques for obtaining an operation amount of an operation lever provided in a work machine. In Patent Documents 1 and 2, a pressure sensor is provided in a remote control valve provided with an operation lever, and a signal detected by the pressure sensor is converted into an operation amount of the operation lever.
Further, there is a technique disclosed in Patent Document 3 as a technique for changing the travel speed of a working machine. In Patent Document 3, a control device is provided with a changeover switch. By switching the changeover switch between high speed and low speed, the angle of the tilt plate of the hydraulic motor is changed, and the travel speed of the working machine becomes high or low corresponding to the switching of the changeover switch.

Japanese Utility Model Laid-Open No. 5-6155 JP-A-5-106606 Japanese Patent No. 2711829

In Patent Documents 1 and 2, unless a sensor such as a pressure sensor is provided in the remote control valve, the operation amount of the control lever cannot be obtained. That is, unless a pressure sensor is provided, it is impossible to detect how much the remote control valve is moving.
Further, in Patent Document 3, although the traveling speed of the working machine is switched between high speed and low speed by switching the selector switch, the traveling speed after switching cannot be adjusted.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a hydraulic system for a working machine that can easily determine the amount of operation of an operation valve that moves according to the operation of an operation member. Another object of the present invention is to provide a hydraulic system for a working machine that can adjust the travel speed. A further object of the present invention is to provide a travel system hydraulic circuit and a travel control method that can be controlled according to the amount of operation of an operating member, a setting signal from a setting member, and the number of revolutions of a travel motor.

The technical means of the present invention for solving this technical problem are characterized by the following points.
In a travel system hydraulic circuit for controlling the travel devices, the travel system hydraulic circuit includes a plurality of operation valves for controlling the operation of the work implement, An operating valve for adjusting the primary pressure of the hydraulic oil to be supplied, a setting member for making a certain setting for causing the working machine to perform a desired operation, and a control device for controlling the traveling device are provided. The traveling device is configured to be capable of switching the traveling speed of the work implement between a high speed and a lower traveling speed than the high speed according to the amount of operation of each of the operation valves. a traveling pump and a traveling motor are provided, and a second oil passage extending from each operation valve and through which hydraulic oil supplied from each operation valve flows is connected to each operation valve; A third measuring device for measuring the rotation speed of each traveling motor is attached to each of the traveling motors, and the control device responds to the setting signal from the setting member and the rotation speed signal from each of the third measuring devices. the operating valves are actuated independently of manual operation of the operating valves so as to adjust the pressure of the hydraulic fluid supplied from the operating valves, and the operating valves are controlled by the traveling pumps According to the operation amount of the operation valve, the traveling device has a high speed, a medium speed that is slower than the high speed, and a slower traveling speed than the medium speed. The travel speed of the work implement can be switched between a low speed and a low speed, the setting member is configured to set the travel speed of the work implement to the low speed slower than the medium speed, and the control device is a control signal output to the operating valve so that the travel speed of the work implement calculated based on the rotation speed signal does not exceed the set speed at low speed set by the setting member; By changing the primary pressure of the working oil supplied to each of the operation valves, the secondary pressure of the working oil supplied from each of the operation valves is adjusted to a pressure corresponding to the primary pressure. Hydraulic oil is supplied to each of the traveling pumps, and each of the traveling pumps maintains a constant flow rate of the hydraulic oil discharged from each of the traveling pumps according to the secondary pressure. The work machine is operated to travel at the set speed at the low speed set by the member.

The operation valve adjusts the flow rate of hydraulic fluid discharged from each of the traveling pumps by changing or maintaining a constant pressure of hydraulic fluid flowing through the second oil passage.

In a travel control method comprising travel devices provided on the left and right sides of a work machine and a travel system hydraulic circuit for controlling the travel devices, the travel system hydraulic circuit includes a plurality of operation valves for controlling the operation of the work machine. an operating valve for adjusting the primary pressure of the operating oil supplied to the operating valve; a setting member for making a certain setting for causing the working machine to operate as desired; and a setting member for controlling the traveling device. a control device, wherein the travel device is configured to be capable of switching the travel speed of the work implement between a high speed and a lower travel speed, which is slower than the high speed, according to the amount of operation of each of the operation valves; A traveling device is provided with a traveling pump and a traveling motor, and a second oil passage extending from each of the operating valves and through which hydraulic oil supplied from each of the operating valves flows is connected to each of the operating valves of each of the traveling pumps. , each of the traveling motors is attached with a third measuring device for measuring the number of rotations of the traveling motor; to operate the operating valves independently from manual operation of the operating valves so as to adjust the pressure of hydraulic oil supplied from the operating valves, and the operating valves are operated by the traveling pumps. The flow rate of the discharged hydraulic oil is adjusted, and the traveling device operates at a high speed, a medium speed that is slower than the high speed, and a low speed that is slower than the medium speed, depending on the amount of operation of the operation valve. and the setting member is configured to be able to set the traveling speed of the work implement to the low speed lower than the medium speed, and the control device comprises and changing the control signal output to the operating valve so that the traveling speed of the working machine calculated based on the rotation speed signal does not exceed the set speed at low speed set by the setting member. to determine the primary pressure of the hydraulic fluid supplied to each of the operation valves, adjust the secondary pressure of the hydraulic fluid supplied from each of the operation valves to a pressure corresponding to the primary pressure, and operate Each traveling pump operates to supply oil to each traveling pump, and each traveling pump maintains a constant flow rate of the hydraulic oil discharged from each traveling pump in accordance with the secondary pressure, thereby adjusting the setting member. The working machine is operated so as to travel at the set speed at the low speed set by .

The operation valve adjusts the flow rate of hydraulic fluid discharged from each of the traveling pumps by changing or maintaining a constant pressure of the hydraulic fluid flowing through the second oil passage.

According to the present invention, it is possible to easily obtain the operation amount of the operation valve that moves according to the operation of the operation member. Further, according to the present invention, the traveling system hydraulic circuit can be controlled according to the operation amount of the operating member, the setting signal from the setting member, and the rotation speed of the traveling motor.

3 is a schematic diagram of a hydraulic circuit of a travel system in the first embodiment; FIG. FIG. 4 is a diagram showing the relationship between the amount of operation of an operation valve and the pressure of hydraulic fluid (secondary pressure); FIG. 5 is a schematic diagram of a hydraulic circuit of a traveling system in a second embodiment; It is a figure which shows the modification of the hydraulic circuit of the traveling system in 2nd Embodiment. FIG. 5 is a diagram showing the relationship between a set value, a swing amount (swing angle) of a travel lever, and a target travel speed. FIG. 11 is a schematic diagram of a hydraulic circuit of a travel system in a third embodiment; FIG. 4 is a diagram showing the relationship between the engine speed and the degree of opening of the operating valve; It is a figure which shows the modification of the hydraulic circuit of a traveling system. 1 is an overall side view of a skid steer loader; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.
[First embodiment]
FIG. 9 shows a side view of a working machine according to the invention. FIG. 9 shows a skid steer loader as an example of the work machine. However, the work machine according to the present invention is not limited to the skid steer loader, and may be other types of loader work machine such as a compact track loader. Also, a work machine other than a loader work machine may be used.

The skid steer loader 1 includes a body (vehicle body) 2, a cabin 3, a working device 4, and traveling devices 5A and 5B.
A cabin 3 is mounted on the fuselage 2 . A driver's seat 8 is provided in the rear part of the cabin 3 . In the embodiment of the present invention, the front side of the driver (the left side in FIG. 9) sitting in the driver's seat 8 of the skid steer loader 1 is the front side, the rear side of the driver (the right side in FIG. 9) is the rear side, and the left side of the driver ( The front side in FIG. 9) will be described as the left side, and the right side of the driver (back side in FIG. 9) 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 . The work device 4 is a device that performs work and is equipped on the machine body 2 . The traveling device 5A is a device that causes the body 2 to travel, and is provided on the left side of the body 2 . The traveling device 5B is a device that causes the body 2 to travel, and is provided on the right side of the body 2 . A prime mover 7 is provided in the rear portion of the body 2 . The prime mover 7 is a diesel engine (engine). Note that the prime mover 7 is not limited to an engine, and may be an electric motor or the like.

A travel lever 9L is provided on the left side of the driver's seat 8 . A travel lever 9R is provided on the right side of the driver's seat 8 . The left travel lever 9L operates the left travel device 5A, and the right travel lever 9R operates the right travel device 5B.
The work device 4 has a boom 10, a bucket 11, a lift link 12, a control link 13, a boom cylinder C1, and a bucket cylinder C2. Booms 10 are provided on the left and right sides of the body 2 . The bucket 11 is provided at the tip (front end) of the boom 10 . Lift links 12 and control links 13 support the base (rear) of boom 10 . The boom cylinder C1 drives the boom 10 up or down.

Specifically, the lift link 12 , control link 13 and boom cylinder C<b>1 are provided on the left and right sides of the airframe 2 . The upper portion of the lift link 12 is pivoted to the upper portion of the base of the boom 10 . The lower portion of the lift link 12 is pivotally supported on the rear side portion of the fuselage 2 . The control link 13 is arranged in front of the lift link 12 . One end of the lift link 12 is pivotally supported on the bottom of the base of the boom 10 and the other end is pivotally supported on the body 2 .

The boom cylinder C<b>1 is a hydraulic cylinder that raises and lowers the boom 10 . The upper part of the boom cylinder C1 is pivotally supported on the front part of the base of the boom 10. As shown in FIG. A lower portion of the boom cylinder C1 is pivotally supported on a side portion of the rear portion of the machine body 2 . The boom 10 swings up and down by the lift link 12 and the control link 13 when the boom cylinder C1 is extended and retracted. The bucket cylinder C2 is a hydraulic cylinder that swings the bucket 11 . The bucket cylinder C2 connects between the left portion of the bucket 11 and the left boom, and connects between the right portion of the bucket 11 and the right boom. Hydraulic attachments such as a hydraulic crusher, a hydraulic breaker, an angle bloom, an earth auger, a pallet fork, a sweeper, a mower, and a snow blower can be attached to the tip (front) of the boom 10 instead of the bucket 11. there is

Wheel-type traveling devices 5A and 5B having front wheels 5F and rear wheels 5R are employed as the traveling devices 5A and 5B in this embodiment. Crawler type (including semi-crawler type) traveling devices 5A and 5B may be employed as the traveling devices 5A and 5B.
FIG. 1 shows part of the hydraulic circuit (hydraulic system) of the skid steer loader 1 . As shown in FIG. 1 , the hydraulic circuit (hydraulic system) has a main pump 20 , a sub-pump 21 , a pilot pump 23 and a travel pump 24 . The main pump 20 is a pump that discharges hydraulic oil, and is, for example, a hydraulic pump for driving a hydraulic cylinder provided in the work device 4 or a hydraulic actuator of a hydraulic attachment attached to the work device 4 . The sub-pump 21 is a hydraulic pump for increasing the amount of hydraulic oil. The pilot pump 23 is a hydraulic pump that mainly discharges hydraulic fluid for signaling and hydraulic fluid for control. The travel pump 24 is a hydraulic pump for driving the travel devices 5A and 5B.

Main pump 20 , sub-pump 21 , pilot pump 23 and traveling pump 24 are driven by prime mover 7 . The main pump 20, the sub-pump 21, and the pilot pump 23 are constant displacement gear pumps. The traveling pump 24 is a swash plate type variable displacement pump.
Hereinafter, for convenience of explanation, the "pilot pump" will be referred to as the "first pump", and the "traveling pump" will be referred to as the "second pump".

As shown in FIG. 1 , the hydraulic circuit of the skid steer loader 1 has a first oil passage 30 and an operation valve 31 . The first oil passage 30 is made of a steel pipe or the like, and has both ends connected to the first pump 23 and the operation valve 31 .
Specifically, the first oil passage 30 is an oil passage branched from the middle, and includes an oil passage 30a, an oil passage 30b, and an oil passage 30c. The oil passage 30a is an oil passage extending from the first pump 23 to a branching portion. The oil passage 30b is one of the two branched oil passages. The oil passage 30c is the oil passage on the other side of the two branched oil passages. For convenience of explanation, the oil passage 30b is called one first oil passage 30b, and the oil passage 30c is called the other first oil passage 30c.

The operating valve 31 is a valve that can change the pressure of hydraulic oil output according to the operation of the operating member 9, and includes a first operating valve 31a and a second operating valve 31b.
The first operation valve 31a is connected to one first oil passage 30b, and the second operation valve 31b is connected to the other first oil passage 30c. A travel lever 9L, which is one of the operating members, is swingably provided on the first operating valve 31a. A traveling lever 9R, which is one of the operating members, is swingably provided on the second operating valve 31b.

The first operation valve 31a is a valve that can change the pressure of the hydraulic oil to be output according to the operation of the travel lever 9L, that is, the swing amount (swing angle) of the travel lever 9L. Specifically, the first operation valve 31a is provided with a movable rod. The traveling lever 9L can press a rod, and the pressing amount of the rod (the operation amount of the first operation valve 31a) is set according to the swing angle of the traveling lever 9L. For example, the operation amount of the first operation valve 31a increases as the swing angle of the travel lever 9L increases. Further, the operation amount of the first operation valve 31a decreases as the swing angle of the travel lever 9L decreases. The flow rate (pressure) of hydraulic oil output from the first operation valve 31a changes according to the amount of operation of the first operation valve 31a.

That is, the swing amount (swing angle) of the travel lever 9L and the operation amount of the first operation valve 31a correspond to each other, and the operation amount of the first operation valve 31a is replaced with the swing amount of the travel lever 9L. It is also possible to think
The second operation valve 31b is a valve that can change the pressure of the hydraulic oil to be output according to the operation of the travel lever 9R, that is, the swing amount (swing angle) of the travel lever 9R. Specifically, the second operation valve 31b is provided with a movable rod. The travel lever 9R can press a rod, and the pressing amount of the rod (the operation amount of the second operation valve 31b) is set according to the swing angle of the travel lever 9R. For example, the operation amount of the second operation valve 31b increases as the swing angle of the travel lever 9R increases. Further, the operation amount of the second operation valve 31b decreases as the swing angle of the travel lever 9R decreases. The flow rate (pressure) of hydraulic oil output from the second operation valve 31b changes according to the amount of operation of the second operation valve 31b.

That is, the swing amount (swing angle) of the travel lever 9R and the operation amount of the second operation valve 31b correspond to each other, and the operation amount of the second operation valve 31b is replaced with the swing amount of the travel lever 9R. It is also possible to think
Note that the first operation valve 31a and the second operation valve 31b may be provided for one traveling lever. In this case, the first operation valve 31a changes the pressure of the hydraulic oil to be output according to the swing amount when the traveling lever is operated to one side (for example, to the left). Further, the second operation valve 31b changes the pressure of the hydraulic oil to be output according to the swing amount when the travel lever is operated to the other side (for example, to the right).

A second oil passage 32 made of a steel pipe or the like is connected to the output side (the side that outputs hydraulic oil) of the operation valve 31 (first operation valve 31a, second operation valve 31b). A second pump 24 is connected to the second oil passage 32 .
Specifically, the second oil passage 32 includes one second oil passage 32a (referred to as one second oil passage 32a) connected to the first operation valve 31a and the other oil passage connected to the second operation valve 31b. passage 32b (referred to as the other second oil passage 32b).

The second pumps 24 are the left traveling pump 24a connected to one second oil passage 32a for driving the traveling device 5A, and the other pump for driving the traveling device 5B. 2 and a right travel pump 24b connected to oil passage 32b.
Also, the left traveling pump 24a has a swash plate. The tilting angle of the swash plate of the left traveling pump 24a is changed by the pressure of the working oil in one of the second oil passages 32a. When the tilting angle of the swash plate of the left traveling pump 24a is changed, the discharge direction and discharge flow rate of hydraulic oil discharged from the left traveling pump 24a are changed. In other words, the output of the left traveling pump 24a can be changed by the hydraulic oil in one of the second oil passages 32a.

The right travel pump 24b has a swash plate. The tilting angle of the swash plate of the right traveling pump 24b is changed by the pressure of the hydraulic oil in the other second oil passage 32b. When the tilting angle of the swash plate of the right traveling pump 24b is changed, the discharge direction and discharge flow rate of hydraulic oil discharged from the right traveling pump 24b are changed. In other words, the output of the right travel pump 24b can be changed by the hydraulic oil in the other second oil passage 32b.

Therefore, in the hydraulic circuit, hydraulic fluid output from the operation valves 31 (the first operation valve 31a, the second operation valve 31b) flows through the second oil passages 32 (the second oil passage 32a on one side, the second oil passage 32a on the other side). The fuel is supplied to the second pumps 24 (the left traveling pump 24a and the right traveling pump 24b) via the passage 32b).
The second pump 24 (left traveling pump 24a, right traveling pump 24b) is connected to a third oil passage 33 made of a steel pipe or the like. The third oil passage 33 is an oil passage that connects the travel motor 34 and the second pump 24 and circulates hydraulic oil between the travel motor 34 and the second pump 24 .

More specifically, the traveling motor 34 includes a left traveling motor 34a whose traveling speed is changed by hydraulic oil discharged from the left traveling pump 24a, and a right traveling motor 34b whose traveling speed is changed by hydraulic oil discharged from the right traveling pump 24b. contains.
The third oil passage 33 includes an oil passage 33a connecting the left traveling pump 24a and the left traveling motor 34a, and an oil passage 33b connecting the right traveling pump 24b and the right traveling motor 34b.

Therefore, in the hydraulic circuit, the hydraulic fluid discharged from the left travel pump 24a changes the rotation direction and rotation speed of the axle (output shaft) 35 of the left travel motor 34a. In addition, the rotational direction and number of rotations of the axle 35 of the right travel motor 34b are changed by the hydraulic oil discharged from the right travel pump 24b. Depending on the rotation direction and rotation speed of the axle 35 of the left travel motor 34a and right travel motor 34b, the rotation direction and rotation speed of the front wheels 5F and rear wheels 5R are changed, and the travel direction (forward, backward) and travel speed of the skid steer loader 1 are changed. changes.

A first measuring device 41 capable of measuring the pressure (primary pressure) of the working oil flowing through the first oil passage 30 is connected to the first oil passage 30 . Specifically, the first measuring device 41 includes a measuring device 41a connected to one first oil passage 30b and a measuring device 41b connected to the other first oil passage 30c.
The measuring device 41a is a pressure gauge that measures the primary pressure of the working oil flowing through one of the first oil passages 30b. The measuring device 41a outputs a first corresponding value corresponding to the measured primary pressure. The measuring device 41b also outputs a first corresponding value corresponding to the measured primary pressure. The first corresponding value is a value determined according to the magnitude of the measured primary pressure, for example, the value of the primary pressure itself (physical quantity) or a value (level) determined according to the primary pressure. be. The first corresponding value is converted into current, voltage, or the like by each of the measuring devices 41 a and 41 b and output to the control device 43 .

A second measuring device 42 capable of measuring the pressure (secondary pressure) of hydraulic fluid flowing through the second oil passage 32 is connected to the second oil passage 32 . Specifically, the second measuring device 42 includes a measuring device 42a connected to one second oil passage 32a and a measuring device 42b connected to the other second oil passage 32b.
The measuring device 42a is a pressure gauge that measures the secondary pressure of the working oil flowing through one of the second oil passages 32a. The measuring device 42a outputs a second corresponding value corresponding to the measured secondary pressure. The measuring device 42b also outputs a second corresponding value corresponding to the measured secondary pressure. The second corresponding value is a value determined according to the magnitude of the measured secondary pressure. ), etc. The second corresponding value is converted into a current, a voltage, or the like by each of the measuring devices 42 a and 42 b and output to the control device 43 .

The control device 43 can perform various controls regarding the skid steer loader 1 . In addition, the control device 43 is composed of a CPU or the like, and is a first corresponding value corresponding to the primary pressure, which is the pressure of the working oil in the first oil passage 30, and the pressure of the working oil in the second oil passage 32. Based on the second corresponding value corresponding to the secondary pressure, it is possible to obtain the operation amount of the operation valve 31 .
For example, based on the primary pressure (corresponding value) of hydraulic fluid flowing through one first oil passage 30b and the secondary pressure (corresponding value) of hydraulic oil flowing through one second oil passage 32a, the control device 43 , the operation amount of the first operation valve 31a. Alternatively, the control device 43 may be controlled based on the primary pressure (corresponding value) of hydraulic fluid flowing through the other first oil passage 30c and the secondary pressure (corresponding value) of hydraulic oil flowing through the other second oil passage 32b. , the operation amount of the second operation valve 31b.

In the hydraulic circuit of the embodiment described above, as shown in FIG. A two-system circuit composed of a first oil passage 30c, a second oil passage 32b, and a second operation valve 31b is shown. Here, the control device 43 can obtain the operation amount of the first operation valve 31a belonging to the circuit of one system and the operation amount of the second operation valve 31b belonging to the circuit of two systems. In the following description, for the sake of convenience, an example of a circuit of one system will be used to explain how to obtain the manipulated variable. Further, in the embodiment described above, it is explained that the manipulated variable is obtained based on the first corresponding value corresponding to the primary pressure and the second corresponding value corresponding to the secondary pressure. In the following description, for convenience, the first corresponding value is the value of the primary pressure itself (first corresponding value=primary pressure) measured by the first measuring device 41, and the second corresponding value is the second measuring device 42. is the value of the secondary pressure itself (second corresponding value=secondary pressure) measured in .

The control device 43 has a first acquisition section 51 , a second acquisition section 52 , a storage section 53 , a calculation section 54 and a control section 55 . The first acquisition unit 51, the second acquisition unit 52, the calculation unit 54, and the control unit 55 are composed of programs, electric circuits, electronic circuits, and the like incorporated in the control device 43. FIG.
The first acquisition unit 51 acquires, for example, the primary pressure of hydraulic fluid flowing through one first oil passage 30b, and acquires the primary pressure of hydraulic fluid measured by the measuring device 41a. The second acquisition unit 52 acquires, for example, the secondary pressure of hydraulic fluid flowing through one of the second oil passages 32a, and acquires the secondary pressure of hydraulic fluid measured by the measuring device 42a.

The storage unit 53 stores the relationship between the operation amount of the first operation valve 31a as shown in FIG. 2 and the pressure (secondary pressure) of the hydraulic oil output from the first operation valve 31a. It is composed of a physical memory and the like. The storage unit 53 may store a table showing the relationship between the secondary pressure of the hydraulic oil and the operation amount of the first operation valve 31a (a table in which the numerical value of the secondary pressure and the numerical value of the operation amount are associated). Alternatively, a function indicating the relationship between the secondary pressure of hydraulic fluid and the amount of operation of the first operation valve 31a may be stored, and is not limited.

Based on the primary pressure (referred to as the acquired primary pressure) acquired by the first acquirer 51 and the secondary pressure (referred to as the acquired secondary pressure) acquired by the second acquirer 52, the calculator 54 determines the first operation valve 31a. Calculate the manipulated variable of
A method of obtaining the manipulated variable of the first operation valve 31a using the obtained primary pressure and the obtained secondary pressure and the calculation unit will be described below with reference to FIG. In the following description, the operation amount of the second operation valve 31b can be obtained by replacing the first operation valve 31a with the second operation valve 31b.

The first acquisition unit 51 acquires the primary pressure of hydraulic fluid measured by the measuring device 41a, that is, the acquired primary pressure, under the condition that the prime mover 7 or the first pump 23 is driven. The second acquiring unit 52 also acquires the secondary pressure of hydraulic fluid measured by the measuring device 42a, that is, the acquired secondary pressure, under the condition that the prime mover 7 or the first pump 23 is driven.
Next, the calculation unit 54 compares the acquired primary pressure and the acquired secondary pressure. When the obtained primary pressure is equal to or higher than the obtained secondary pressure, the calculation unit 54 calculates the first operation valve based on the obtained secondary pressure and the relationship between the secondary pressure and the operation amount stored in the storage unit 53. 31a is calculated.

For example, as shown in FIG. 2, when the storage unit 53 stores a function F indicating the relationship between the secondary pressure of the hydraulic fluid and the operation amount of the first operation valve 31a, the calculation unit 54 stores the function F By substituting the numerical value of the obtained secondary pressure into (for example, the calculated operation amount = α obtained secondary pressure + β), the operation amount of the first operation valve 31a (referred to as the calculated operation amount) is obtained. Then, the calculation unit 54 determines the operation amount of the first operation valve 31a as the operation amount. The function F stored in the storage unit 53 may take any form as long as it indicates the relationship between the secondary pressure and the amount of operation of the first operation valve 31a.

For example, given a function F and an acquired secondary pressure P1, when the acquired primary pressure is equal to or higher than the acquired secondary pressure, the operation amount M1 is the operation amount of the first operation valve 31a. That is, the calculation unit 54 uses the operation amount derived from the relationship between the secondary pressure and the operation amount stored in the storage unit 53 as the operation amount of the first operation valve 31a.
Therefore, when the obtained primary pressure is equal to or higher than the obtained secondary pressure, the calculation unit 54 can easily obtain the operation amount of the first operation valve 31a using the obtained primary pressure and the obtained secondary pressure. For example, without providing a sensor or the like for measuring the swinging amount of the travel lever 9L provided in the first operation valve 31a, the swinging amount of the travel lever 9L can be determined by simply acquiring the acquired primary pressure and the acquired secondary pressure. can be asked for.

On the other hand, when the acquired primary pressure is less than the acquired secondary pressure, the computing unit 54 substitutes the acquired secondary pressure just before the acquired primary pressure becomes less than the acquired secondary pressure into the function F, thereby calculating the operation amount Ask for Then, the calculation unit 54 determines that the operation amount of the first operation valve 31a is the calculated operation amount. In other words, when the obtained primary pressure is less than the obtained secondary pressure, the calculation unit 54 sets the operation amount of the first operation valve 31a to the obtained secondary pressure before the obtained primary pressure becomes less than the obtained secondary pressure. is used to obtain the operation amount of the first operation valve 31a.

For example, let us consider a case where the primary pressure has decreased in the case of the obtained secondary pressure P1 and the operation amount M1. When the primary pressure drops to P2, which is lower than the secondary pressure (acquired secondary pressure) P1, the acquired secondary pressure tends to become the same value as the primary pressure P2. When the primary pressure drops in this way, if the manipulated variable is calculated using the obtained secondary pressure P2 immediately after the primary pressure drops, the calculated manipulated variable is M2. However, even if, for example, the obtained primary pressure < the obtained secondary pressure, the operation of the operating lever 9L is in the state before the obtained primary pressure < the obtained secondary pressure for several seconds. There are many things. Therefore, by adopting the acquired secondary pressure immediately before the acquired primary pressure<the acquired secondary pressure, the manipulated variable of the first operation valve 31a can be easily obtained.

The control unit 55 can output a signal for performing various controls of the skid steer loader 1 . For example, a signal for increasing or decreasing the number of revolutions of the prime mover 7 is output to the prime mover 7, or the opening of various valves (for example, proportional solenoid valves) mounted on the skid steer loader 1 is set. A signal is output to the solenoid valve. The control unit 55 also outputs signals for controlling various electronic/electrical devices mounted on the skid steer loader 1 to the electronic/electrical devices.

Now, as described above, when the acquired primary pressure is less than the acquired secondary pressure, the control unit 55 performs control to increase the output of the first pump 23 . For example, the controller 55 increases the output of the first pump 23 until the first corresponding value becomes equal to or greater than the second corresponding value. For example, by increasing the rotational speed of the prime mover 7, the output of the first pump 23 is increased.
According to the control unit 55, for example, when the skid steer loader 1 travels downhill, the running speed of the skid steer loader 1 may increase regardless of control due to the influence of the downhill. Therefore, in the skid steer loader 1, the control to temporarily suppress the output of the first pump 23 works. However, this control may cause the acquired primary pressure to become less than the acquired secondary pressure. In this case, as described above, control is performed to increase the output of the first pump 23 until at least the obtained primary pressure becomes equal to or higher than the obtained secondary pressure, so the machine can be operated according to the operator's operation.

[Second embodiment]
FIG. 3 shows part of the hydraulic circuit of the skid steer loader in the second embodiment. In the second embodiment, description of the same configuration as in the first embodiment is omitted. As shown in FIG. 3 , the hydraulic circuit of the skid steer loader has a first oil passage 30 and an operating valve 60 .
The first oil passage 30 includes an oil passage 30a, an oil passage 30b, and an oil passage 30c. The oil passage 30 a is an oil passage from the first pump 23 to the operating valve 60 . The oil passage 30 b is an oil passage (one first oil passage) connected to one of the two output ports of the operating valve 60 . The oil passage 30 c is an oil passage (the other first oil passage) connected to the other of the two output ports of the operating valve 60 .

The operation valve 31 is a valve provided downstream of the operation valve 60 in the first oil passage 30 . The operating valve 31 includes a first operating valve 31a and a second operating valve 31b. The first operation valve 31a is connected to one first oil passage 30b, and the second operation valve 31b is connected to the other first oil passage 30c.
The operating valve 60 is a valve that can change the pressure of hydraulic oil, and is, for example, an electromagnetic proportional valve whose opening can be changed by a control signal. A control device 43 is connected to the operating valve 60 . A setting member 61 is also connected to the control device 43 . The control device 43 can acquire the set value set by the setting member 61 .

The control device 43 has a control section 62 . The control unit 62 is composed of a program, an electric circuit, an electronic circuit, etc. incorporated in the control device 43 .
The control unit 62 can output a signal for performing various controls for the skid steer loader 1 . For example, a signal for increasing or decreasing the number of revolutions of the prime mover 7 is output to the prime mover 7, or the opening of various valves (for example, proportional solenoid valves) mounted on the skid steer loader 1 is set. A signal is output to the solenoid valve. The control unit 62 also outputs signals for controlling various electronic/electrical devices mounted on the skid steer loader 1 to the electronic/electrical devices.

Now, the controller 62 can change the opening degree of the operating valve 60 based on the set value set by the setting member 61 .
The setting member 61 is a switch having a plurality of switching positions. The set value of the setting member 61 is determined by each switching position. For example, the setting member 61 can be switched between a first switching position, a second switching position, and a third switching position. The first switching position is a position for setting the upper limit of the traveling speed of the skid steer loader 1 to high speed, and when the first switching position is set, the set value becomes a value indicating "high speed". The second switching position is a position where the upper limit of the running speed is set to medium speed, and when the second switching position is set, the set value becomes a value indicating "medium speed". The third switching position is a position where the upper limit of the running speed is set to low speed, and when the third switching position is set, the set value becomes a value indicating "low speed".

When the setting value set by the setting member 61 is "high speed", the control unit 62 keeps the opening of the operating valve 60 fully open. That is, when the set value indicates high speed, the control unit 62 outputs a control signal to the operating valve 60 to fix the opening of the operating valve 60 to 100%.
Therefore, when the set value is set to a high speed by the setting member 61, the opening of the operating valve 60 is fully opened. It is possible to flow to the operation valve 31 (first operation valve 31a, second operation valve 31b) without lowering. Therefore, when the travel lever 9 (travel lever 9L, travel lever 9R), which is the operating member 9, is swung to the maximum (when the swing amount is the maximum value), the travel pump 24 (left travel pump 24a, right travel The pump 24b) can be driven with maximum power. As a result, the traveling motors 34 (the left traveling motor 34a and the right traveling motor 34b) rotate at maximum speed, so that the traveling speed of the skid steer loader 1 can be increased.

Further, by setting the operation member 9 to a predetermined position, it is possible to set the flow rate of the hydraulic oil flowing toward the traveling pump 24, etc., so that the traveling speed can be adjusted in the range from zero to high speed by the operation member 9. can be done.
When the setting value set by the setting member 61 is "middle speed", the control unit 62 maintains the opening of the operating valve 60 at approximately half of the full opening. That is, when the set value indicates the medium speed, the control unit 62 outputs a control signal to the operating valve 60 to fix the opening degree of the operating valve 60 to approximately 50%.

Therefore, when the set value is set to the medium speed by the setting member 61, the degree of opening of the operating valve 60 is halved. It can flow to the operation valve 31 . Therefore, when the operating member 9 is swung to the maximum, the traveling pump 24 can be driven at approximately half the maximum output. As a result, the rotation speed of the travel motor 34 is reduced, so that the travel speed of the skid steer loader 1 can be set to medium speed.

Also in this case, by setting the operating member 9 to a predetermined position, it is possible to set the flow rate of the hydraulic oil flowing toward the travel pump 24, and the operating member 9 can be used to adjust the travel speed from zero to medium speed. Range can be adjusted.
When the setting value set by the setting member 61 is "low speed", the control unit 62 maintains the opening of the operating valve 60 at approximately 1/4 of the full opening. That is, when the set value indicates the low speed, the control unit 62 outputs a control signal to the operating valve 60 to fix the opening degree of the operating valve 60 to approximately 25%.

Therefore, when the set value is set to a low speed by the setting member 61, the degree of opening of the operating valve 60 is reduced to 1/4. , to the operating valve 31 . Therefore, when the operating member 9 is swung to the maximum, the traveling pump 24 can be driven at approximately 1/4 of the maximum output. As a result, the rotation speed of the travel motor 34 is reduced, so that the travel speed of the skid steer loader 1 can be reduced. Also in this case, by setting the operating member 9 to a predetermined position, it is possible to set the flow rate of the hydraulic oil flowing toward the traveling pump 24, etc., and the traveling speed can be set within a range from zero to low speed by the operating member 9. can be adjusted with

As described above, according to the hydraulic system, the setting member 61 is provided for setting the upper limit of the flow rate and pressure of the hydraulic oil discharged from the first pump 23. By setting the setting member 61, the operation member 9 is swung to the maximum. The upper limit of the travel speed of the skid steer loader 1 can be set when the skid steer loader 1 is fully stroked. In the above-described embodiment, the setting values set by the setting member 61 are three stages of "high speed", "medium speed", and "low speed". , and may be more than three stages or less than three stages.

Note that FIG. 4 shows a hydraulic system of a modification of the second embodiment. As shown in FIG. 4, a third measuring device 63 is provided on the axle 35 of the travel motors 34 (left travel motor 34a, right travel motor 34b). This third measuring device 63 is a device for measuring the number of revolutions of the axle 35 . The number of revolutions measured by the third measuring device 63 is input to the control section 62 . That is, the number of revolutions of the axle 35, that is, the actual running speed is fed back to the control section 62. FIG.

The control unit 62 changes the opening of the operating valve 60 based on the rotation speed (actual running speed) of the axle measured by the third measuring device 63 and the set value. For example, in a situation where the set value is set to medium speed and the operation member 9 is rocked to the maximum (medium speed-full stroke), if the running speed of the skid steer loader 1 does not reach the medium speed for a predetermined time, the control The unit 62 increases the opening of the operating valve 60 to correct the running speed to medium speed. Further, in medium speed-full stroke, when the traveling speed exceeds the medium speed, the opening degree of the operating valve 60 is decreased to correct the traveling speed to the medium speed.

That is, under the condition that the operating member 9 is fully stroked, when the actual traveling speed deviates from the traveling speed (target traveling speed) predetermined corresponding to the set value of the setting member 61, the control A unit 62 corrects the opening degree of the operating valve 60 so that the actual running speed becomes the target running speed.
In the above-described embodiment, the opening degree of the operating valve 60 is corrected based on the actual traveling speed when the operating member 9 is fully stroked. The opening of the operating valve 60 may be corrected based on the actual running speed of the vehicle. In this case, for example, as shown in FIG. 5, the control unit 62 includes a table that associates each set value with the swing amount (swing angle) of the operation member 9 and the target travel speed. Then, the control unit 62 adjusts the opening degree of the operating valve 60 so that the actual travel speed matches the target travel speed shown in the table.

Further, in the second embodiment, the swing amount of the operation member 9 (the operation amount of the operation valve 31) obtained by the calculation unit 54 shown in the first embodiment may be used, or the swing amount of the operation member 9 may be A device for measurement may be provided, and the swing amount of the operation member 9 measured by the device may be employed.

[Third Embodiment]
FIG. 6 shows part of the hydraulic circuit of the skid steer loader in the third embodiment. In the third embodiment, description of the same configuration as in the first embodiment or the second embodiment is omitted.
As shown in FIG. 6, the hydraulic circuit of the skid steer loader is provided with a fourth measuring device 70 . This fourth measuring device 70 is a device for measuring the number of revolutions of the prime mover 7 (for example, the number of revolutions of the engine). The engine speed measured by the fourth measuring device 70 is input to the controller 62 .

The controller 62 sets the opening degree of the operating valve 60 based on the engine speed measured by the fourth measuring device 70 . The control unit 62 has a table, functions, etc. that associate the engine speed and the opening degree of the operating valve 60 as shown in FIG. 7 . The control unit 62 decreases the opening of the operating valve 60 as the engine speed increases and increases the opening of the operating valve 60 as the engine speed decreases.

According to the third embodiment, when the engine speed is high and the work load is large, the travel speed can be reduced by reducing the opening of the operating valve 60 . When the engine speed is low and the work load is small, the traveling speed can be increased by increasing the opening of the operating valve 60 . In other words, in the skid steer loader 1, the upper limit of the running speed can be increased or decreased according to the work load, and well-balanced work can be executed.

In the above-described embodiment, the computing unit 54 measures the primary pressure of hydraulic fluid measured by the first measuring device 41 (acquired primary pressure), the secondary pressure of hydraulic fluid measured by the second measuring device 42 (acquired secondary pressure ), the operation amount of the operation valve 31 is calculated based on the first corresponding value corresponding to the primary pressure and the second corresponding value corresponding to the secondary pressure. you may ask.
For example, as shown in FIG. 8 , the actuated valve 60 is connected to the control device 43 having the first acquisition section 51 , the second acquisition section 52 , the storage section 53 , the calculation section 54 and the control section 62 . In this case, since the primary pressure acting on the first operation valve 31 is determined by the degree of opening of the operating valve 60, the degree of opening is the first corresponding value corresponding to the primary pressure. A measuring device 42a is connected to one of the second oil passages 32a, and a measuring device 42b is connected to the other second oil passage 32b. The secondary pressure measured by the measuring device 42a and the measuring device 42b is the second corresponding value.

The calculation unit 54 converts the degree of opening of the operating valve 60 into primary pressure. For example, the storage unit 53 stores the relationship between the degree of opening of the operating valve 60 and the primary pressure (referred to as the degree-of-opening pressure relationship). The computing unit 54 obtains the primary pressure based on the degree of opening (first corresponding value) acquired by the first acquiring unit 51 and the degree-of-opening pressure relationship stored in the storage unit 53 .
For convenience of explanation, the primary pressure obtained from the opening degree pressure relationship and the first corresponding value will be referred to as the acquired primary pressure. The secondary pressure measured by the second measuring device (measuring device 42a, measuring device 42b) is called acquired secondary pressure.

The calculation unit 54 compares the acquired primary pressure and the acquired secondary pressure. When the acquired primary pressure is equal to or higher than the acquired secondary pressure, the calculation unit 54 adjusts the operation valve 31 ( The operation amounts of the first operation valve 31a and the second operation valve 31b) are obtained.
As described above, the operation is performed based on the opening degree of the operating valve 60, which is the first corresponding value corresponding to the primary pressure, and the measured value measured by the second measuring device 42, which is the second corresponding value corresponding to the secondary pressure. The manipulated variable of the valve 31 can be determined. Note that the hydraulic circuit shown in FIG. 8 is an example. The first corresponding value corresponding to the primary pressure is not limited to the degree of opening of the operating valve 60, and may be obtained from another device. Further, as long as the calculation unit 54 is configured to determine the operation amount of the operation valve 31 based on the first corresponding value corresponding to the primary pressure and the second corresponding value corresponding to the secondary pressure, other configurations are possible. Not limited.

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. In the above-described embodiment, the second pump 24 is a pump that drives the travel motor 34, but is not limited to this, and any pump can be used as long as the output changes according to the pressure and flow rate of hydraulic oil. may be

Reference Signs List 1 working machine 7 prime mover 9 operating member 23 first pump 24 second pump 30 first oil passage 31 operation valve 32 second oil passage 33 third oil passage 34 traveling motor 35 axle 41 first measuring device 42 second measuring device 51 First acquisition unit 52 Second acquisition unit 53 Storage unit 54 Calculation unit 55, 62 Control unit 61 Setting member 63 Third measuring device

Claims (4)

In a traveling system hydraulic circuit that is provided with traveling devices on the left and right sides of the work machine and that controls the traveling devices,
The travel system hydraulic circuit includes a plurality of operation valves for controlling the operation of the work machine, operation valves for adjusting the primary pressure of hydraulic oil supplied to the operation valves, and a desired movement of the work machine. a setting member for setting a certain value for the travel device; and a control device for controlling the travel device,
The traveling device is configured to be able to switch the traveling speed of the working machine between a high speed and a lower traveling speed, which is slower than the high speed, according to the amount of operation of each of the operation valves,
The traveling device is provided with a traveling pump and a traveling motor,
a second oil passage extending from each operation valve and through which hydraulic oil supplied from each operation valve flows is connected to each operation valve;
A third measuring device for measuring the number of revolutions of each traveling motor is attached to each of the traveling motors,
The control device adjusts the pressure of hydraulic fluid supplied from each of the operation valves based on the setting signal from the setting member and the rotation speed signal from each of the third measuring devices. actuating the actuating valve independently from manual operation of
each of the operation valves adjusts the flow rate of hydraulic oil discharged from each of the traveling pumps;
The traveling device adjusts the traveling speed of the work implement between a high speed, a medium speed that is lower than the high speed, and a low speed that is lower than the medium speed, according to the amount of operation of the operation valve. configured to be switchable,
The setting member is configured to be able to set the travel speed of the work implement to the low speed lower than the medium speed,
The control device outputs an output to the operating valve so that the travel speed of the work machine calculated based on the rotation speed signal does not exceed a set speed at low speed set by the setting member. A control signal is changed to determine the primary pressure of hydraulic fluid supplied to each of the operation valves, and the secondary pressure of the hydraulic fluid supplied from each of the operation valves is adjusted to the pressure corresponding to the primary pressure. adjust and operate to supply hydraulic oil to each of the traveling pumps;
Each of the traveling pumps maintains a constant flow rate of the hydraulic oil discharged from each of the traveling pumps in accordance with the secondary pressure, so that the working machine can be operated at a set speed at a low speed set by the setting member. A travel system hydraulic circuit characterized in that it is operated so as to travel . 3. The operation valve adjusts the flow rate of the hydraulic fluid discharged from each of the traveling pumps by changing or maintaining a constant pressure of the hydraulic fluid flowing through the second oil passage. 2. The traveling system hydraulic circuit according to 1. In a travel control method comprising travel devices provided on the left and right sides of a work machine, respectively, and a travel system hydraulic circuit for controlling the travel devices,
In the travel system hydraulic circuit, a plurality of operation valves for controlling the operation of the work machine, operation valves for adjusting the primary pressure of the hydraulic oil supplied to the operation valve, and for causing the work machine to perform a desired operation. A setting member for setting a certain value to the travel device, and a control device for controlling the travel device,
The traveling device is configured to be able to switch the traveling speed of the working machine between a high speed and a lower traveling speed that is slower than the high speed according to the amount of operation of each of the operation valves,
The traveling device is provided with a traveling pump and a traveling motor,
a second oil passage extending from each of the operation valves through which hydraulic oil supplied from each of the operation valves flows is connected to each of the operation valves;
A third measuring device for measuring the number of revolutions of each traveling motor is attached to each of the traveling motors;
each of the operation valves so that the control device adjusts the pressure of hydraulic fluid supplied from each of the operation valves based on the setting signal from the setting member and the rotation speed signal from each of the third measuring devices; actuating the actuating valve independently from manual operation of
each of the operation valves adjusts the flow rate of hydraulic oil discharged from each of the traveling pumps;
The traveling device adjusts the traveling speed of the work implement between a high speed, a medium speed that is lower than the high speed, and a low speed that is lower than the medium speed, according to the amount of operation of the operation valve. configured to be switchable,
The setting member is configured to be able to set the travel speed of the work implement to the low speed lower than the medium speed,
The control device outputs an output to the operating valve so that the travel speed of the work machine calculated based on the rotation speed signal does not exceed a set speed at low speed set by the setting member. A control signal is changed to determine the primary pressure of hydraulic fluid supplied to each of the operation valves, and the secondary pressure of the hydraulic fluid supplied from each of the operation valves is adjusted to the pressure corresponding to the primary pressure. adjust and operate to supply hydraulic oil to each of the traveling pumps;
Each of the traveling pumps maintains a constant flow rate of the hydraulic oil discharged from each of the traveling pumps in accordance with the secondary pressure, so that the working machine can be operated at a set speed at a low speed set by the setting member. A travel control method characterized by operating the vehicle so as to travel . 3. The operation valve adjusts the flow rate of the hydraulic fluid discharged from each of the traveling pumps by changing or maintaining a constant pressure of the hydraulic fluid flowing through the second oil passage. 3. The travel control method according to 3 .

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