JP3923242B2 - Actuator control device for hydraulic drive machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for driving and controlling two hydraulic actuators.
[0002]
[Prior art]
Construction machines such as wheel loaders and skid steer loaders are provided with an arm 10 and a bucket 11 as work machines as shown in FIG. The arm 10 and the bucket 11 are connected to an arm hydraulic cylinder 2 and a bucket hydraulic cylinder 3, respectively.
[0003]
For example, in the wheel loader, after excavating the earth and sand with the bucket 11, the arm 10 is lifted to load the earth and sand in the bucket 11 onto the dump truck. In order to operate the arm 10 in the upward direction during this work, it is necessary to operate the bucket 11 in the dumping direction so that the attitude of the bucket 11 maintains a constant attitude horizontal to the ground. This is called leveling control. Leveling control is indispensable for preventing the earth and sand in the bucket 11 from spilling down.
[0004]
However, if the leveling control is left only to the manual operation of the operator, the arm operation lever 4 and the bucket operation lever 5 must be combined and operated as shown in FIG. Such combined operation places a heavy burden on the operator and requires skill. For this reason, an invention that can perform leveling control without burdening the operator and without requiring skill has been conventionally known. That is, an invention in which not only the arm 10 but also the bucket 11 is simultaneously operated only by operating the arm operating lever 4 to perform horizontal holding control has been known.
[0005]
On the other hand, a series circuit and a parallel circuit are known as hydraulic circuits for supplying pressure oil to a plurality of hydraulic actuators such as an arm hydraulic actuator and a bucket hydraulic actuator.
[0006]
FIGS. 9A and 9B conceptually show the configuration of the series circuit and the parallel circuit. As shown in FIG. 9A, the series circuit supplies the pressure oil discharged from the hydraulic pump 1 to the leading arm hydraulic cylinder 2 through the first pressure oil supply passage 24a and discharges it from the arm hydraulic cylinder 2. The returned pressure oil is supplied to the bucket hydraulic cylinder 3 via the return pressure oil supply passage 40 to drive both hydraulic cylinders 2 and 3. On the other hand, as shown in FIG. 9B, the parallel circuit uses the pressure oil discharged from the hydraulic pump 1 for the arm via the first pressure oil supply path 24a and the second pressure oil supply path 24b, respectively. The hydraulic cylinder 2 and the bucket hydraulic cylinder 3 are supplied to drive both hydraulic cylinders 2 and 3.
[0007]
The series circuit has an advantage that the driving speed of the leading arm hydraulic cylinder 2 does not decrease, that is, the operating speed of the leading arm 10 does not decrease when performing complex operation. Therefore, the series circuit is suitable for leveling control. However, in the series circuit, the driving pressure due to the pressure oil discharged from the hydraulic pump 1 is divided and reduced by the head arm hydraulic cylinder 2 and the rear bucket hydraulic cylinder 3, respectively. For this reason, when the load of the hydraulic cylinder 3 for buckets of the back | latter stage becomes large, there exists a problem that a drive pressure reduces and a hydraulic actuator cannot be driven with the drive pressure corresponding to a load.
[0008]
On the other hand, the parallel circuit has a drawback that the operating speed of the arm 10 is reduced when performing a complex operation compared to a single operation, but the driving pressure of the bucket hydraulic cylinder 3 is not reduced. There are advantages. Therefore, the parallel circuit is suitable for the case where the bucket hydraulic cylinder 3 and the arm hydraulic cylinder 2 perform an operation requiring a large thrust at the same time during the complex operation.
[0009]
In Japanese Patent Laid-Open No. 10-219730, a hydraulic circuit is constituted by a series circuit, and return pressure oil discharged from the arm hydraulic cylinder 2 when the arm operation lever 4 is operated in the arm raising direction is supplied to the bucket 11. The pressure is divided by a pressure control valve so as to be held horizontally and supplied to the bucket hydraulic cylinder 3, and when the load on the bucket 11 exceeds a certain value, the arm hydraulic cylinder 2 remains in a series circuit state. The invention describes that the return pressure oil is communicated to the tank via the arm operation valve.
[0010]
[Problems to be solved by the invention]
According to the invention described in the above publication, the arm hydraulic cylinder 2 is driven in the series circuit regardless of the load of the bucket 11. For this reason, even if the bucket hydraulic cylinder 3 reaches the stroke end and the load on the bucket 11 increases, the arm hydraulic cylinder 2 continues to move without obtaining a sufficient driving force. This becomes a problem when the load applied to the arm 11 is large.
[0011]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to switch between a series circuit and a parallel circuit in accordance with a load state so as not to cause a decrease in driving pressure of the work machine and a reduction in speed of the work machine.
[0012]
[Means, actions and effects for solving the problems]
  In order to achieve the above-mentioned solution, the first invention of the present invention
  The hydraulic pump (1) and the first and second hydraulic actuators that are driven by supplying the discharge pressure oil of the hydraulic pump (1) through the first and second pressure oil supply passages (24a, 24b) (2, 3),First and second operating means (4, 5) provided corresponding to the first and second hydraulic actuators (2, 3), respectively, and switchable in two directions;In an actuator control device of a hydraulic drive machine equipped with
  A return pressure oil supply path (35, 35a, 35d, 48, 51) for supplying discharged pressure oil discharged from the first hydraulic actuator (2) to the second hydraulic actuator (3);
  When the operation amount of the first operation means (4) is equal to or greater than a predetermined amount, the return pressure oil supply passage (35, 35a, 35d) is connected to the hydraulic oil discharge side hydraulic chamber of the first hydraulic actuator (2). , 48, 51) and communicated with the hydraulic chamber on the pressure oil inflow side of the second hydraulic actuator (3) and discharged from the first hydraulic actuator (2) to the second hydraulic actuator (3). When the second operating means (5) is operated and the operation amount of the first operating means (4) is smaller than a predetermined amount, the pressure oil to be supplied is supplied. The discharge port of the hydraulic pump (1) communicates with the hydraulic chamber on the pressure oil inflow side of the second hydraulic actuator (3) and is discharged from the hydraulic pump (1) to the second hydraulic actuator (3). Pressure oil supply switching means for supplying pressure oil And 7,58,59),
  Pressure oil supplied to the second hydraulic actuator (3) via the return pressure oil supply passage (35, 35a, 35d, 48, 51) according to the load pressure of the second hydraulic actuator (3). Control means (54, 55) for controlling the tank to communicate with the tank (14);
  It is provided with.
[0013]
The first invention will be specifically described with reference to FIG.
[0014]
According to the first aspect of the invention, when the load pressure of the bucket hydraulic cylinder 3 is not more than a certain value, the regeneration cancellation valve 54 is located on the closing side. Therefore, not all of the pressure oil discharged from the boom hydraulic cylinder 2 is discharged to the tank 14, and a predetermined ratio of the pressure oil is discharged from the arm operation valve 6 and the return oil passage 35. , 35a, the fixed regeneration rate valve 43, the return oil passage 35d, the check valve 48, the return oil passage 51, and the bucket operation valve 7 are supplied to the bucket hydraulic cylinder 3. That is, when the load on the bucket hydraulic cylinder 3 is small, the return hydraulic oil of the arm hydraulic cylinder 2 configured in a series circuit is supplied to the bucket hydraulic cylinder 3.
[0015]
On the other hand, when the load pressure of the bucket hydraulic cylinder 3 exceeds a certain value, the regeneration cancellation valve 54 is positioned on the open side. For this reason, the pressure of the pilot oil passage 53 connected to the pressure control valve 55 becomes the tank pressure, and the pressure control valve 55 is located at the communication position 55c, and all of the pressure oil discharged from the arm hydraulic cylinder 2 is returned to the return oil passage 35, 35 b, the fixed regeneration rate valve 43 and the pressure control valve 55 are discharged to the tank 14.
[0016]
As described above, according to the first invention, when the load on the bucket hydraulic cylinder 3 is small, a series circuit is formed, and the bucket hydraulic cylinder 3 is driven by the return pressure oil of the arm hydraulic cylinder 2. For this reason, the problem that the operating speed of the leading arm 10 decreases during the leveling control does not occur. When the load on the bucket hydraulic cylinder 3 is large, the circuit is switched to a parallel circuit, and the return pressure oil from the arm hydraulic cylinder 2 communicates with the tank 14, so that the arm hydraulic cylinder 2 can be moved with a sufficient driving force. .
[0017]
As described above, according to the first invention, the return pressure oil of the arm hydraulic cylinder 2 is switched to the parallel circuit according to the load state and communicates with the tank 14, so even if the load on the bucket 11 increases, The hydraulic cylinder 2 can be moved with a sufficient driving force.
[0018]
  Also, the second invention is
  The hydraulic pump (1) and the first and second hydraulic actuators that are driven by supplying the discharge pressure oil of the hydraulic pump (1) through the first and second pressure oil supply passages (24a, 24b) (2, 3) and the first and second hydraulic actuators (2, 3), respectively.Switchable in two directionsIn an actuator control device for a hydraulically driven machine comprising first and second operating means (4, 5),
  A return pressure oil supply path (35, 35a, 35d, 48, 51) for supplying discharged pressure oil discharged from the first hydraulic actuator (2) to the second hydraulic actuator (3);
  When the load pressure of the second hydraulic actuator (3) is below a certain value and the first and second operating means (4, 5) are operated in a specific operating direction, The discharge pressure oil discharged from the first hydraulic actuator (2) is divided into a predetermined ratio, and the pressure oil divided into the predetermined ratio is returned to the return pressure oil supply path (35, 35a, 35d, 48, 51). To the second hydraulic actuator (3), and according to the change in the operation amount of the second operating means (5), the return pressure oil supply path (35, 35a, 35d, 48, 51)From the first hydraulic actuator (2)Control means (36, 54, 55) for changing the ratio of the flow rate of the pressure oil supplied to the second hydraulic actuator (3);
  It is provided with.
[0019]
The second invention will be specifically described with reference to FIG.
[0020]
According to the second aspect of the invention, when the load pressure of the bucket hydraulic cylinder 3 is equal to or less than a certain value, the regeneration cancellation valve 54 is positioned on the closing side. When the arm operation lever 4 is operated in a specific operation direction (boom raising direction), the pressure oil discharged from the arm hydraulic cylinder 2 is predetermined by the fixed regeneration rate valve 43 and the pressure control valve 55. Shunt to ratio. The pressure oil divided into the predetermined ratio is supplied to the arm operation valve 6, the return oil passages 35 and 35a, the fixed regeneration rate valve 43, the return oil passage 35d, the check valve 48, the return oil passage 51, and the bucket operation valve 7. To the bucket hydraulic cylinder 3. That is, when the load on the bucket hydraulic cylinder 3 is small and the arm operation lever 4 is operated in a specific operation direction (boom raising direction), the return pressure of the arm hydraulic cylinder 2 is configured as a series circuit. Pressure oil obtained by diverting oil to a predetermined ratio is supplied to the bucket hydraulic cylinder 3. Therefore, the ratio between the flow rate supplied to the arm hydraulic cylinder 2 and the flow rate supplied to the bucket hydraulic cylinder 3 has a constant relationship, and leveling control is performed to keep the bucket 11 in a constant posture.
[0021]
On the other hand, when the bucket operation lever 5 is operated in a specific operation direction (bucket dumping direction), the regeneration rate increasing valve 36 is operated to supply the hydraulic oil to the bucket hydraulic cylinder 3 according to the operation amount. Increase the flow rate ratio.
[0022]
As described above, according to the second invention, when the load on the bucket hydraulic cylinder 3 is small and the arm operation lever 4 is operated in a specific operation direction (boom raising direction), the arm hydraulic pressure is increased. The bucket hydraulic cylinder 3 is driven by pressure oil obtained by dividing the return pressure oil of the cylinder 2 into a predetermined ratio. When the bucket operation lever 5 is operated in a specific operation direction (bucket dumping direction), the regeneration rate increasing valve 36 is activated, and the ratio of the flow rate of the pressure oil supplied to the bucket hydraulic cylinder 3 according to the operation amount. Increases, the operating speed of the bucket 11 can be increased. Therefore, according to the second aspect of the present invention, the driving speed of the bucket hydraulic cylinder 3 can be increased by operating the bucket operation lever 5 during leveling control.
[0023]
  Also, the third invention is
  When the second operation means (5) is operated in an operation direction other than the specific operation direction,Control is performed to supply pressure oil to the second hydraulic actuator (3) via the second pressure oil supply path (24b).
  It is characterized by.
[0024]
The third invention will be specifically described with reference to FIG.
[0025]
When the arm operation lever 4 and the bucket operation lever 5 are operated in a specific operation direction (boom raising direction, bucket dumping direction), the pressure oil discharged from the arm hydraulic cylinder 2 is changed to the arm operation valve 6, The oil is supplied to the bucket hydraulic cylinder 3 through the return oil passages 35 and 35a, the fixed regeneration rate valve 43, the return oil passage 35d, the check valve 48, the return oil passage 51, and the bucket operation valve 7. Here, the arm operation lever 4 and the bucket operation lever 5 are switched to a state in which they are operated in an operation direction (arm raising direction, bucket tilt direction) other than a specific operation direction (boom raising direction, bucket dumping direction). When the bucket hydraulic cylinder 3 is driven only by the return pressure oil from the arm hydraulic cylinder 2 sometimes, sufficient thrust cannot be obtained by the arm hydraulic cylinder 2 as described above.
[0026]
Therefore, when the operation is switched to the operation of raising the arm and bucket tilt, the operation is switched to the parallel circuit, and the discharge hydraulic oil of the hydraulic pump 1 is supplied to the bucket hydraulic cylinder 3 via the second pressure oil supply passage 24b. At this time, when the load pressure of the bucket hydraulic cylinder 3 exceeds a certain value, the return pressure oil of the arm hydraulic cylinder 2 communicates with the tank 14 and becomes a tank pressure, and sufficient thrust is obtained in the arm hydraulic cylinder 2.
[0027]
That is, stroke restriction control valves 58 and 59 are provided on both sides of the spool of the arm operation valve 7 in FIG. When the arm operation lever 4 is operated in the arm raising direction, the stroke restriction control valve 58 is positioned at the valve position 58a, and the bucket operation valve 7 is set so that the second pressure oil supply passage 24b and the bucket hydraulic cylinder 3 do not communicate with each other. The spool stroke is regulated. Therefore, the return oil passage 51 is in communication with the arm hydraulic cylinder 3 to form a series circuit.
[0028]
At this time, when the pilot pressure in the bucket tilt direction becomes higher than the pilot pressure in the arm raising direction, the stroke restriction control valve 58 is switched to the valve position 58b. Then, the oil passage 18c communicates with the tank 14, and the pilot pressure acting on the bucket operation valve 7 via the throttle 18d becomes the tank pressure.
[0029]
Therefore, the bucket operation valve 7 is stroked to the valve position 7e by the pilot pressure in the bucket tilt direction. When the bucket operation valve 7 strokes to the valve position 7e, the discharge pressure oil of the hydraulic pump 1 is supplied to the bucket hydraulic cylinder 3 via the oil passages 24, 24b, the pressure compensation valve 9, and the bucket operation valve 7.
[0030]
For this reason, the bucket hydraulic cylinder 3 is driven by the pressure oil discharged from the hydraulic pump 1. When the load pressure of the bucket hydraulic cylinder 3 exceeds a certain value, the return pressure oil of the arm hydraulic cylinder 2 becomes the tank pressure, and the arm hydraulic cylinder 2 is driven with sufficient thrust.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an actuator control apparatus for a hydraulic drive machine according to the present invention will be described below with reference to the drawings.
[0032]
In the embodiment, a hydraulic circuit mounted on a construction machine such as a wheel loader or a skid steer loader is assumed. These construction machines are assumed to have an arm 10 and a bucket 11 as work machines.
[0033]
FIG. 1 shows a hydraulic circuit according to the first embodiment.
[0034]
A hydraulic pump 1 shown in FIG. 1 is driven by an engine (not shown) to discharge pressure oil. This discharge pressure oil is supplied to the arm operation valve 6 and the bucket operation valve 7 as described later. A pilot hydraulic pump (not shown) is also driven by the engine to discharge pilot pressure oil. The pilot pressure oil is supplied to a hydraulic operation lever device 40 shown in FIG. The operation lever device 40 includes an arm operation lever 4 and a bucket operation lever 5. The arm operation lever 4 is provided corresponding to the arm operation valve 6. The bucket operation lever 5 is provided corresponding to the bucket operation valve 7.
[0035]
From the operation lever device 40, pilot pressure oil of pilot pressure corresponding to the operation amount of the arm operation lever 4 and pilot pressure oil of pilot pressure corresponding to the operation amount of the bucket operation lever 5 are output.
[0036]
That is, when the arm operation lever 4 is operated to the “arm raising side”, pilot pressure oil having a pressure corresponding to the operation amount (hereinafter referred to as arm raising pressure) is output to the pilot oil passage 18.
[0037]
Similarly, when the arm operation lever 4 is operated to the “arm lowering side”, pilot pressure oil having a pressure corresponding to the operation amount (hereinafter referred to as arm lowering pressure) is output to the pilot oil passage 19.
[0038]
Similarly, when the bucket operating lever 5 is operated to the “dump side”, pilot pressure oil having a pressure corresponding to the operation amount (hereinafter referred to as bucket dump pressure) is output to the pilot oil passage 20.
[0039]
Similarly, when the bucket operating lever 5 is operated to the “tilt side”, pilot pressure oil having a pressure corresponding to the operation amount (hereinafter referred to as bucket tilt pressure) is output to the pilot oil passage 21.
[0040]
The arm hydraulic cylinder 2 and the bucket hydraulic cylinder 3 are driven by the supply of the discharge hydraulic oil from the hydraulic pump 1 through the arm operation valve 6 and the bucket operation valve 7, respectively.
[0041]
The valve positions of the arm operation valve 6 and the bucket operation valve 7 move in accordance with the arm raising pressure, arm lowering pressure, bucket dump pressure, and bucket tilt pressure.
[0042]
FIG. 8 shows a configuration of the working machine of the construction machine according to the embodiment.
[0043]
As shown in FIG. 8, arm hydraulic cylinder 2 and bucket hydraulic cylinder 3 are provided corresponding to arm 10 and bucket 11, respectively. The arm hydraulic cylinder 2 corresponds to the arm operation valve 6. The bucket hydraulic cylinder 3 corresponds to the bucket operation valve 7. The arm hydraulic cylinder 2 and the bucket hydraulic cylinder 3 are respectively driven by pressure oil supplied via the arm operation valve 6 and the bucket operation valve 7.
[0044]
The rod of the arm hydraulic cylinder 2 and the rod of the bucket hydraulic cylinder 3 are connected to the arm 10 and the bucket 11, respectively. The bucket 11 is connected to the arm 10.
[0045]
The arm hydraulic cylinder 2 includes a bottom chamber 2a and a head chamber 2b. When pressure oil is supplied from the arm operation valve 6 to the bottom chamber 2a of the arm hydraulic cylinder 2 via the oil passage 28, the rod of the arm hydraulic cylinder 2 is extended and the arm 10 is operated to the "arm raising side". Is done. When pressure oil is supplied from the arm operation valve 6 to the head chamber 2b of the arm hydraulic cylinder 2 via the oil passage 29, the rod of the arm hydraulic cylinder 2 is retracted and the arm 10 is moved to the “arm lowering side”. Actuated.
[0046]
The bucket hydraulic cylinder 3 includes a bottom chamber 3a and a head chamber 3b. When pressure oil is supplied from the bucket operation valve 7 to the bottom chamber 3a of the bucket hydraulic cylinder 3 via the oil passage 31, the rod of the bucket hydraulic cylinder 3 is extended and the bucket 11 is operated to the "dump side". The Further, when pressure oil is supplied from the bucket operation valve 7 to the head chamber 3b of the bucket hydraulic cylinder 3 via the oil passage 32, the rod of the bucket hydraulic cylinder 3 is retracted and the bucket 11 is moved to the "tilt side". Is done.
[0047]
Hereinafter, the connection relationship between the operation lever device 40 (operation levers 4 and 5), the operation valves 6 and 7, and the hydraulic cylinders 2 and 3 and the connection relationship between the operation valves 6 and 7 and the hydraulic pump 1 will be described in detail.
The operation lever device 40 is connected to the pilot ports of the operation valves 6 and 7 via shuttle valves 49 and 50.
[0048]
That is, the pilot oil passage 18 from which the arm raising pressure is output is branched into the pilot oil passage 18a and the pilot oil passage 18b. The pilot oil passage 19 from which the arm lowering pressure is output is branched into a pilot oil passage 19a and a pilot oil passage 19b.
[0049]
The pilot oil passage 18 b and the pilot oil passage 20 through which the bucket dump pressure is output communicate with each inlet port of the shuttle valve 50. The outlet port of the shuttle valve 50 communicates with the pilot oil passage 22. Similarly, the pilot oil passage 19 b and the pilot oil passage 21 where the bucket tilt pressure is output communicate with each inlet port of the shuttle valve 49. The outlet port of the shuttle valve 49 communicates with the pilot oil passage 23.
[0050]
For this reason, from the outlet port of the shuttle valve 50, the pilot pressure oil having the larger pilot pressure of the arm raising pressure and the bucket dump pressure is output to the pilot oil passage 22 and is supplied to the pilot port 7g of the bucket operation valve 6. To be supplied.
[0051]
Similarly, from the outlet port of the shuttle valve 49, the pilot pressure oil having the larger pilot pressure of the arm lowering pressure and the bucket tilt pressure is output to the pilot oil passage 23 and is opposite to the bucket operation valve 6. Is supplied to the pilot port 7h.
[0052]
The arm raising pressure is output to the pilot oil passage 18 a and supplied to the pilot port 6 g of the arm operation valve 6. The arm lowering pressure is output to the pilot oil passage 19 a and supplied to the pilot port 6 h on the opposite side of the arm operation valve 6.
[0053]
The arm operation valve 6 is a control valve that controls the flow rate and direction of the pressure oil discharged from the hydraulic pump 1 and supplies it to the arm hydraulic cylinder 2.
[0054]
That is, the pressure oil discharged from the hydraulic pump 1 flows into the arm operation valve 6 through the oil passage 24 and the branch oil passage 24a. The pressure oil flowing out from the arm operation valve 6 is supplied to the arm hydraulic cylinder 2 via the oil passage 28 or 29.
[0055]
The arm operation valve 6 has three valve positions 6c (neutral position), 6a (arm raised position), and 6e (arm lowered position). When the arm raising pressure is supplied to the arm raising side pilot port 6g of the arm operating valve 6 via the pilot oil passage 18a, the opening area (opening amount) of the arm operating valve 6 is changed according to the arm raising pressure. The arm operation valve 6 is positioned on the arm raising position 6a side. When the arm operation valve 6 is positioned at the position 6 a, pressure oil having a flow rate corresponding to the opening area is supplied to the bottom chamber 2 a of the arm hydraulic cylinder 2 via the arm operation valve 6 and the oil passage 28. As a result, the arm 10 is actuated to the arm raising side.
[0056]
When the arm lowering pressure is supplied to the pilot port 6h of the arm operating valve 6 through the pilot oil passage 19a, the opening area (opening amount) of the arm operating valve 6 is changed according to the arm lowering pressure, The arm operation valve 6 is positioned on the arm lowering position 6e side. When the arm operation valve 6 is positioned at the position 6 e, pressure oil having a flow rate corresponding to the opening area is supplied to the head chamber 2 b of the arm hydraulic cylinder 2 via the arm operation valve 6 and the oil passage 29. As a result, the arm 10 is operated to the arm lowering side.
[0057]
When the arm operation valve 6 is positioned at the valve position 6a, the pressure oil discharged from the head chamber 2b of the arm hydraulic cylinder 2 (hereinafter referred to as return pressure oil) is output to the return oil passage 35 via the arm operation valve 6. The When the arm operation valve 6 is positioned at the valve position 6e, the return pressure oil discharged from the bottom chamber 2a of the arm hydraulic cylinder 2 is output to the return oil passage 35 via the arm operation valve 6.
[0058]
The arm operation valve 6 is connected to the tank 14 via an oil passage 25 c and an oil passage 25.
[0059]
Similarly, the flow rate and direction of the pressure oil discharged from the hydraulic pump 1 are controlled by the bucket operation valve 7, and the controlled pressure oil is supplied to the bucket hydraulic cylinder 3.
[0060]
That is, the pressure oil discharged from the hydraulic pump 1 is introduced into the bucket operation valve 7 through the oil passage 24 and its branch oil passage 24b. The pressure oil output from the bucket operation valve 7 is supplied to the bucket hydraulic cylinder 3 via the oil passage 31 or 32.
[0061]
The bucket operation valve 7 has five valve positions 7c (neutral position), 7b (bucket dump position), 7a (bucket dump position), 7d (bucket tilt position), and 7e (bucket tilt position). Note that the valve position of the bucket operation valve 7 changes continuously, and the opening area also changes continuously. When the higher pilot pressure of the arm raising pressure or the bucket dump pressure is supplied to the bucket dump side pilot port 7g of the bucket operation valve 7 through the pilot oil passage 22, the bucket operation valve is set according to the pilot pressure. 7 is changed, and the bucket operation valve 7 is positioned on the bucket dump positions 7b and 7a side. When the bucket operation valve 7 is located at the position 7 a, the discharge hydraulic oil from the hydraulic pump 1 flows in, and the pressure oil having a flow rate corresponding to the opening area flows through the bucket operation valve 7 and the oil passage 31 to the bottom of the bucket hydraulic cylinder 3. It is supplied to the chamber 3a. As a result, the bucket 11 is operated to the dump side.
[0062]
When the higher pilot pressure of the arm lowering pressure or the bucket tilt pressure is supplied to the bucket tilt side pilot port 7h of the bucket operation valve 7 via the pilot oil passage 23, the bucket operation is performed according to the pilot pressure. The opening area (opening amount) of the valve 7 is changed, and the bucket operation valve 7 is positioned on the bucket tilt 7d, 7e side. When the bucket operating valve 7 is positioned at the position 7 e, pressure oil having a flow rate corresponding to the opening area is supplied to the head chamber 3 b of the bucket hydraulic cylinder 3 through the bucket operating valve 7 and the oil passage 32. As a result, the bucket 11 is actuated to the tilt side.
[0063]
When the bucket operating valve 7 is positioned at the valve positions 7b and 7a, the pressure oil discharged from the head chamber 3b of the bucket hydraulic cylinder 3 is output to the return oil passage 25b via the bucket operating valve 7. When the bucket operation valve 7 is positioned at the valve positions 7d and 7e, the pressure oil discharged from the bottom chamber 3a of the bucket hydraulic cylinder 3 is output to the return oil passage 25d via the bucket operation valve 7. The pressure oil output to the return oil passages 25 b and 25 d is discharged to the tank 14 through the oil passage 25.
[0064]
A return oil passage 51 is connected to the bucket operation valve 7. The return oil passage 51 communicates with the return oil passage 35.
[0065]
When the bucket operation valve 7 is positioned at the valve position 7 b, the return oil passage 51 communicates with the oil passage 31 via the bucket operation valve 7. Therefore, the return pressure oil discharged from the arm hydraulic cylinder 2 is supplied to the bottom chamber 3 a of the bucket hydraulic cylinder 3 via the return oil path 35, the return oil path 51, the bucket operation valve 7, and the oil path 31. . Similarly, when the bucket operation valve 7 is positioned at the valve position 7 d, the return oil passage 51 communicates with the oil passage 32 via the bucket operation valve 7. Therefore, the return pressure oil discharged from the arm hydraulic cylinder 2 is supplied to the head chamber 3 b of the bucket hydraulic cylinder 3 through the return oil path 35, the return oil path 51, the bucket operation valve 7, and the oil path 32. .
[0066]
The bucket operation valve 7 is connected to the tank 14 via an oil passage 26 b and an oil passage 25.
[0067]
In this embodiment, pressure compensating valves 8 and 9 are provided for the respective operation valves 6 and 7.
[0068]
The pressure compensation valve 8 is provided on the upstream side of the arm operation valve 6 as viewed from the hydraulic pump 1, that is, on the pressure oil supply path between the hydraulic pump 1 and the arm operation valve 6. Similarly, the pressure compensation valve 9 is provided on the upstream side of the bucket operation valve 7 as viewed from the hydraulic pump 1, that is, on the pressure oil supply path between the hydraulic pump 1 and the bucket operation valve 7.
[0069]
The pressure compensation valves 8 and 9 are valves that make the pressure difference between the pressure oil pressure upstream of the operation valves 6 and 7 and the pressure oil pressure downstream of the operation valves 6 and 7 the same value. The following formula (1), which is a general formula of a hydraulic circuit,
Q = c · A · √ (ΔP) (1)
As described above, the flow rate Q proportional to the operation amount of the operation lever 4 (opening area A of the operation valve 6) operated by the operator is irrelevant to the magnitude of the load. Is obtained. Similarly, a flow rate Q proportional to the operation amount of the operation lever 5 (opening area A of the operation valve 7) is obtained regardless of the magnitude of the load.
[0070]
The pressure compensation valve 8 corresponding to the arm operation valve 6 includes a flow control valve portion 8a and a pressure reducing valve portion 8b. The pressure oil discharged from the hydraulic pump 1 flows into the flow control valve portion 8a through the oil passage 24 and the branch oil passage 24a. The pressure oil discharged from the hydraulic pump 1 flows into the pressure reducing valve portion 8b through the oil passage 24 and the branched oil passage 24c.
[0071]
Similarly, the pressure compensation valve 9 corresponding to the bucket operation valve 7 includes a flow control valve portion 9a and a pressure reducing valve portion 9b. The pressure oil discharged from the hydraulic pump 1 flows into the flow control valve portion 9a through the oil passage 24 and the branch oil passage 24b. The pressure oil discharged from the hydraulic pump 1 flows into the pressure reducing valve portion 9b through the oil passage 24 and the branch oil passage 24d.
[0072]
The outlet of the pressure reducing valve portion 8b communicates with the oil passages 27 and 27b through the oil passage 27a. The outlet of the pressure reducing valve portion 9b communicates with the oil passage 27 through the oil passage 27b.
[0073]
Therefore, the maximum load pressure (hereinafter referred to as the maximum load pressure) is applied to the pressure reducing valve portion 8b through the oil passages 27 and 27a in the direction in which the pressure reducing valve portion 8b is closed. .
[0074]
The oil passage 27b is branched to the oil passage 27c. The oil passage 27 c communicates with the inlet port of the shuttle valve 57. The other inlet port of the shuttle valve 57 communicates with the oil passage 47. The oil passage 47 communicates with the return oil passage 35 via the return oil passage 35d. The outlet port of the shuttle valve 57 communicates with the oil passage 27d. The oil passage 27d is connected in a direction to close the pressure reducing valve portion 9b.
[0075]
Therefore, the maximum load pressure is input to the shuttle valve 57 via the oil passage 27c. Further, the pressure of the pressure oil used to drive the bucket hydraulic cylinder 3 out of the return pressure oil of the arm hydraulic cylinder 2 (hereinafter referred to as a regeneration pressure) is input to the shuttle valve 57 via the oil passage 47. Note that “regeneration” is used in the sense that the return pressure oil is used to drive the bucket hydraulic cylinder 3. The shuttle valve 57 outputs the larger pressure of the regeneration pressure and the maximum load pressure.
[0076]
For this reason, the larger pressure of the regeneration pressure and the maximum load pressure is applied to the pressure reducing valve portion 9b through the oil passage 27d in the direction in which the pressure reducing valve portion 9b is closed.
[0077]
By operating the pressure compensating valves 8 and 9, the differential pressure ΔP across the operation valves 6 and 7 is made constant and constant. As a result, the flow rate is determined by the opening area of the operation valves 6 and 7 regardless of the magnitude of the load on the hydraulic cylinders 2 and 3. That is, from the above equation (1) (Q = c · A · √ (ΔP)), the flow rate of each operation valve 6, 7 according to the opening area (opening amount) A of each operation valve 6, 7 regardless of the load fluctuation. Q is uniquely determined.
[0078]
The unload valve 34 is connected to the discharge oil passage 24 of the hydraulic pump 1. A maximum load pressure is applied to the unload valve 34 through the oil passage 27 in the direction in which the unload valve 34 is closed.
[0079]
The unload valve 34 sets the differential pressure between the pressure of the discharge pressure oil of the hydraulic pump 1 and the maximum load pressure of the hydraulic cylinders 2 and 3 regardless of the fluctuation of the load of the hydraulic cylinders 2 and 3. A constant value according to the set pressure.
[0080]
That is, the unload valve 34 opens and closes by the spring force of the spring provided in the unload valve 34, the maximum load pressure, and the discharge pressure of the hydraulic pump 1. The unload valve 34 is operated to the closed side by the spring force and the maximum load pressure. The unload valve 34 is operated to the opening side by the discharge pressure of the hydraulic pump 1. As a result, the differential pressure between the discharge pressure of the hydraulic pump 1 and the maximum load pressure becomes constant according to the set pressure of the unload valve 34.
[0081]
A relief valve 33 is connected to the discharge oil passage 24 of the hydraulic pump 1. The relief valve 33 limits the pressure of the pressure oil discharged from the hydraulic pump 1 to the oil passage 24 to a set relief pressure or less.
[0082]
The return oil passage 35 is branched into three return oil passages 35a, 35b, and 35c.
[0083]
The return oil passages 35 a and 35 b are connected to the respective inlet ports of the fixed regeneration rate valve 43. The return oil passage 35 c is connected to the inlet port of the regeneration rate increasing valve 36. The return oil passage 35a and the return oil passage 35c merge at the outlet ports of the fixed regeneration rate valve 43 and the regeneration rate increase valve 36 and communicate with the return oil passage 35d. The return oil passage 35 d communicates with the inlet port of the check valve 48. The outlet port of the check valve 48 communicates with the return oil passage 51. The check valve 48 allows the flow of pressure oil only in the direction from the return oil passage 35d to the return oil passage 51. The return oil passage 35 d branches to an oil passage 47.
[0084]
The return oil passage 35 b is connected to the inlet port of the pressure control valve 55 through the outlet port of the fixed regeneration rate valve 43. The outlet port of the pressure control valve 55 communicates with the tank 14 via the oil passage 25.
[0085]
The fixed regeneration rate valve 43 has three valve positions 43c (neutral position), 43a (arm raised position), and 43b (arm lowered position).
[0086]
The pilot oil passage 22 is branched into a pilot oil passage 22 a, and the pilot oil passage 22 a is connected to one pilot port 43 d of the fixed regeneration rate valve 43. Similarly, the pilot oil passage 23 is branched into a pilot oil passage 23 a, and the pilot oil passage 23 a is connected to the other pilot port 43 e of the fixed regeneration rate valve 43.
[0087]
Therefore, when the pressures in the pilot oil passages 22a and 23a are the same, the fixed regeneration rate valve 43 is positioned at the neutral position 43c. When the fixed regeneration rate valve 43 is positioned at the neutral position 43c, the pressure oil in the return oil passage 35a is shut off by the fixed regeneration rate valve 43, and the pressure oil in the return oil passage 35b passes through the fixed regeneration rate valve 43. It passes through and flows into the inlet port of the pressure control valve 55.
[0088]
When the pilot pressure in the pilot oil passage 22a is larger than the pilot pressure in the pilot oil passage 23a, the fixed regeneration rate valve 43 is located at the arm raising position 43a. When the fixed regeneration rate valve 43 is positioned at the arm raising position 43a, the pressure oil in the return oil passage 35a passes through the throttle 43f in the fixed regeneration rate valve 43 and is output to the return oil passage 35d, and the return oil passage The pressure oil in 35 b passes through the throttle 43 g in the fixed regeneration rate valve 43 and flows into the inlet port of the pressure control valve 55. Here, the throttle diameter (opening area) of the throttle 43f corresponding to the return oil path 35a and the throttle diameter (opening area) of the throttle 43g corresponding to the return oil path 35b are set to predetermined values. These throttle diameters (opening areas) are determined in accordance with the supply flow rate to the hydraulic cylinder 3 required to hold the bucket 11 horizontally when the arm 10 is operated to the arm raising side.
[0089]
Similarly, when the pilot pressure in the pilot oil passage 23a is larger than the pilot pressure in the pilot oil passage 22a, the fixed regeneration rate valve 43 is located at the arm lowering position 43b. When the fixed regeneration rate valve 43 is positioned at the arm lowering position 43b, the pressure oil in the return oil passage 35a passes through the throttle 43h in the fixed regeneration rate valve 43 and is output to the return oil passage 35d, and the return oil passage The pressure oil in 35 b passes through the throttle 43 i in the fixed regeneration rate valve 43 and flows into the inlet port of the pressure control valve 55.
[0090]
The regeneration rate increasing valve 36 has three valve positions 36c (neutral position), 36a (bucket dump position), and 36b (bucket tilt position).
[0091]
The pilot oil passage 20 is branched into a pilot oil passage 20a, and the pilot oil passage 20a is connected to one pilot port 36d of the regeneration rate increasing valve 36. Similarly, the pilot oil passage 21 is branched into a pilot oil passage 21a, and the pilot oil passage 21a is connected to the other pilot port 36e of the regeneration rate increasing valve 36.
[0092]
Therefore, when the pressures in the pilot oil passages 20a and 21a are the same, the regeneration rate increasing valve 36 is located at the neutral position 36c. When the regeneration rate increasing valve 36 is located at the neutral position 36 c, the pressure oil in the return oil passage 35 c is blocked by the regeneration rate increasing valve 36.
[0093]
When the pilot pressure in the pilot oil passage 20a is larger than the pilot pressure in the pilot oil passage 21a, the regeneration rate increasing valve 36 is located at the bucket dump position 36a. When the regeneration rate increase valve 36 is located at the bucket dump position 36a, the pressure oil in the return oil passage 35c passes through the regeneration rate increase valve 36 and is output to the return oil passage 35d. Similarly, when the pilot pressure in the pilot oil passage 21a is larger than the pilot pressure in the pilot oil passage 20a, the regeneration rate increasing valve 36 is located at the bucket tilt position 36b. When the regeneration rate increase valve 36 is positioned at the bucket tilt position 36b, the pressure oil in the return oil passage 35c passes through the regeneration rate increase valve 36 and is output to the return oil passage 35d.
[0094]
The pressure control valve 55 has two valve positions 55a (blocking position) and 55c (communication position). As the pressure control valve 55 moves from the cutoff position 55a to the communication position 55c, the opening area continuously increases. The input port pressure is applied as a pilot pressure to one pilot port 55f of the pressure control valve 55 through the pilot oil passage 55e.
[0095]
The return oil passage 51 branches to an oil passage 51 a and communicates with the oil passage 53 via a throttle 52. The oil passage 53 is connected to each of the inlet port of the regeneration cancellation valve 54 and the other pilot port 55g of the pressure control valve 55.
[0096]
Therefore, the pressure control valve 55 is balanced at a position where the pressure in the oil passage 53 and the pressure in the pilot oil passage 55 e are balanced, and the upstream pressure of the pressure control valve 55 becomes equal to the pressure in the return oil passage 51. Therefore, the return pressure oil discharged from the arm hydraulic cylinder 2 is diverted at a constant ratio and distributed to the return oil passage 35d and the return oil passage 35b. The return pressure oil distributed to the return oil passage 35d is supplied to the bucket hydraulic cylinder 3 via the check valve 48, the return oil passage 51, and the bucket operation valve 7. On the other hand, the pressure oil distributed to the return pressure oil 35 b is discharged to the tank 14 via the pressure control valve 55 and the oil passage 25.
[0097]
When the regeneration rate increasing valve 36 is located at the neutral position 36c, the pressure control valve 55 is configured to reduce the pressure oil flowing in the return oil passage 35d at a ratio of the opening area of the throttle 43f and the opening area of the throttle 43g of the fixed regeneration rate valve 43. The flow rate (supply flow rate to the hydraulic cylinder 3) and the flow rate of pressure oil flowing through the return oil passage 35b (discharge flow rate to the tank 14) are divided. This diversion ratio is set to a ratio for holding the bucket 11 horizontally.
[0098]
When the regeneration rate increasing valve 36 is located at the bucket dump position 36a or the tilt position 36b, the flow rate diverted toward the return oil passage 35d increases as the bucket dump pressure or the tilt pressure increases.
[0099]
The regeneration cancel valve 54 is provided to discharge the entire flow rate in the return pressure oil 35 to the tank 14 when the pressure in the return oil passage 51, that is, the load pressure of the bucket hydraulic cylinder 3 exceeds a certain value.
[0100]
The regeneration cancel valve 54 is provided with the spring force of the spring 54a on the closing side. The load pressure in the return pressure oil 51 is applied as a pilot pressure to the pilot port 54b facing the spring 54a of the regeneration cancel valve 54. As will be described later, a pilot pressure is applied to the pilot port 54c facing the spring 54a of the regeneration cancel valve 54 via the pilot oil passage 19g.
[0101]
Therefore, when the force acting on the pilot ports 54b and 54c is smaller than the spring force of the spring 54a, the regeneration cancellation valve 54 is positioned on the closing side.
[0102]
In contrast, when the force acting on the pilot ports 54b and 54c becomes equal to or greater than the spring force of the spring 54a, the regeneration cancel valve 54 is positioned on the open side. Therefore, the pressure oil in the return oil passage 51 is discharged to the tank 14 via the oil passage 51 a, the throttle 52, the oil passage 53, the regeneration cancellation valve 54, and the oil passage 25. Then, the pressure in the return oil passage 51 is reduced by the throttle 52 to become a tank pressure, and this tank pressure acts on the pilot port 55g of the pressure control valve 55 as a pilot pressure. Therefore, the upstream pressure of the pressure control valve 55 becomes a tank, and the entire flow rate of the return pressure oil is discharged to the tank 14 via the pressure control valve 55.
[0103]
In the present embodiment, a counter balance valve 39 is built in the bucket dump position 7 a of the bucket operation valve 7. When the spool of the bucket operation valve 7 strokes, the pressure in the oil passage 31 is applied to the side of the counter balance valve 39 that faces the side where the spring is provided. The counter balance valve 39 has a valve position 39 a for blocking communication between the oil passage 32 and the oil passage 25, and a valve position 39 b for connecting the oil passage 32 and the oil passage 25.
[0104]
When the pressure in the oil passage 31 is equal to or higher than a certain pressure, the counter balance valve 39 is switched to the valve position 39b. For this reason, the return pressure oil from the oil passage 32 is discharged to the tank 14 through the oil passage 25b. When the pressure in the oil passage 31 is smaller than the above constant pressure, the counter balance valve 39 is switched to the valve position 39a by the spring force. For this reason, the return pressure oil from the oil passage 32 is blocked, and the discharge amount of the return pressure oil to the tank 14 is eliminated.
[0105]
A counter balance valve 41 having the same function as the counter balance valve 39 is also incorporated in the bucket dump position 7 b of the bucket operation valve 7.
[0106]
Similarly, at the bucket tilt positions 7e and 7d of the bucket operation valve 7, as with the counter balance valve 39, if the pressure in the oil passage 32 is equal to or higher than a certain pressure, the return pressure oil from the oil passage 31 is passed through the oil passage 25d. Counter balance valves 42 and 65 are provided to shut off the return pressure oil and eliminate the return pressure oil discharge amount to the tank 14 when the pressure in the oil passage 32 is lower than the predetermined pressure. .
[0107]
The bucket operation valve 6 is provided with stroke restriction control valves 58 and 59 for restricting the stroke position of the spool. The stroke restriction control valve 58 controls the movement of the spool so that the stroke is restricted at the bucket dump position 7b and not positioned at the bucket dump position 7a when the bucket operation valve 7 is moved to the bucket dump position 7b, 7a side. .
[0108]
That is, the stroke restriction control valve 58 is provided with a piston 58c that can come into contact with the end of the bucket operation valve 7 on the pilot port 7h side. The stroke restriction control valve 58 has two valve positions 58a (blocking position) and 58b (discharge position).
[0109]
The pilot oil passage 18b is branched into a pilot oil passage 18c, and the pilot oil passage 18c is connected to one pilot port 58d of the stroke restriction control valve 58. Similarly, the pilot oil passage 23 is connected to a pilot port 58e on the piston 58c side of the stroke restriction control valve 58.
[0110]
The pilot oil passage 18 c is branched to the oil passage 18 d and connected to the inlet port of the stroke restriction control valve 58. The outlet port of the stroke restriction control valve 58 is connected to the oil passage 18e. The oil passage 18 e communicates with the tank 14 through the oil passage 25.
[0111]
Therefore, the stroke restriction control valve 58 is positioned at the shut-off position 58a by the pilot pressure in the pilot oil passage 18c. For this reason, even if the bucket operation valve 7 tries to move to the bucket dump positions 7b and 7a, the stroke is restricted by the piston 58c at the bucket dump position 7b and does not move to the bucket dump position 7a.
[0112]
When the pilot pressure in the pilot oil passage 23 is larger than the pilot pressure in the pilot oil passage 18c, the stroke restriction control valve 58 is located at the passage position 58b.
[0113]
The pilot pressure oil in the pilot oil passage 18c is discharged to the tank 14 through the pilot oil passage 18d, the stroke restriction control valve 58, and the oil passages 18e and 25. Therefore, the pilot pressure in the pilot oil passages 18c and 18b becomes the tank pressure.
[0114]
The stroke restriction control valve 59 on the pilot port 7 g side of the bucket operation valve 7 is the same as the stroke restriction control valve 58. In this case, the stroke restriction control valve 59 is positioned at the shut-off position by the pilot pressure in the pilot oil path 19c branched from the pilot oil path 19b, and the movement position of the bucket operation valve 7 is regulated at the bucket tilt position 7d.
[0115]
In the present embodiment, a floating control circuit is provided. Here, the floating control means that both arm chambers 2a and 2b of the arm hydraulic cylinder 2 are tank pressures when the arm 10 is operated to the arm lowering side, and the arm 10 raises and lowers the arm according to the external force. It is the control that makes it possible to operate freely.
[0116]
The command to execute the floating control is given, for example, by operating the arm operating lever 4 in the arm lowering direction and simultaneously turning on a floating control switch provided on a knob or the like of the operating lever 4. When the floating control switch is turned on, an electrical signal is output from the floating control switch.
The floating control circuit is configured around the switching valves 60, 61, and 62.
[0117]
The switching valve 60 is an electromagnetic switching valve and has two valve positions 60a and 60b. The pilot oil passage 19 is connected to the inlet port of the switching valve 60. The outlet port of the switching valve 60 is connected to the oil passages 19f and 19g. An electric signal indicating an on operation of the floating control switch is applied to the electromagnetic solenoid 60c of the switching valve 60. When the electromagnetic solenoid 60c of the switching valve 60 is not energized, the switching valve 60 is positioned at the valve position 60a, and the pilot pressure oil in the pilot oil passage 19 passes through the switching valve 60 and is output to the oil passage 19g. When an electric signal is applied to the electromagnetic solenoid 60c of the switching valve 60, the switching valve 60 is positioned at the valve position 60b, and the pilot pressure oil in the pilot oil passage 19 passes through the switching valve 60 and is output to the oil passage 19f.
[0118]
The switching valve 61 has two valve positions 61a (blocking position) and 61b (passing position). The downstream of the restrictor 63 is connected to the inflow / outlet port of the switching valve 61. The other inlet / outlet port of the switching valve 61 is connected to the oil passage 29b. The oil passage 29 b communicates with the tank 14 through the oil passage 25. Pilot pressure oil that has passed through the oil passage 19 f is supplied to the pilot port 61 c of the switching valve 61. When pilot pressure is applied to the pilot port 61 c of the switching valve 61, the switching valve 61 is positioned at the passage position 61 b, and the downstream of the throttle 63 communicates with the tank 14 via the switching valve 61 and the oil passages 29 b and 25.
[0119]
The oil passage 29 is branched into an oil passage 29a. The oil passage 29 a communicates with the upstream of the throttle 63.
[0120]
The switching valve 62 has two valve positions 62a (blocking position) and 62b (passing position). The oil passage 29 a is connected to the inflow / outflow port of the switching valve 62. The other inlet / outlet port of the switching valve 61 is connected to the oil passage 29b. A pilot pressure downstream of the throttle 63 is applied to the pilot port 62 c of the switching valve 62. The upstream pressure of the throttle 63 is applied to the side of the switching valve 62 facing the pilot port 62c. Therefore, when the pressure downstream of the throttle 63 becomes low, the switching valve 62 is positioned at the passage position 62b, and the oil passage 29a communicates with the tank 14 via the switching valve 62 and the oil passages 29b and 25.
[0121]
Next, the operation of the hydraulic circuit of the first embodiment shown in FIG. 1 will be described.
[0122]
It is assumed that the operator has operated the arm operation lever 4 of the operation lever device 40 to the arm raising side. At this time, it is assumed that the bucket operation lever 5 is not tilted from the neutral position.
[0123]
For this reason, the arm raising pressure corresponding to the operation amount of the arm operation lever 4 is output to the pilot oil passage 18a. This arm raising pressure is supplied to the arm raising side pilot port 6g of the arm operation valve 6 through the pilot oil passage 18a.
[0124]
Further, an arm raising pressure corresponding to the operation amount of the arm operation lever 4 is output to the pilot oil passage 18 b and applied to one inlet port of the shuttle valve 50. Since the bucket operating lever 5 is now in the neutral position, the pressure in the pilot oil passage 20, that is, the pressure in the other inlet port of the shuttle valve 50 is the pressure in the tank 14. Therefore, the arm raising pressure corresponding to the operation amount of the arm operation lever 4 is output to the pilot oil passage 22 via the shuttle valve 50. The arm raising pressure is supplied to the dump side pilot port 7g of the bucket operation valve 7 through the pilot oil passage 22.
[0125]
Therefore, the arm operation valve 6 is positioned on the arm raising position 6a side according to the arm raising pressure applied to the operation valves 6 and 7, and the bucket operation valve 7 is positioned on the dump position 7b side.
[0126]
When the arm operation valve 6 is positioned at the arm raising position 6a, the pressure oil discharged from the hydraulic pump 1 flows into the inlet port of the arm operation valve 6 through the oil passages 24, 24a and the pressure compensation valve 8. Then, the pressure oil having a flow rate corresponding to the opening area flows out and is supplied to the bottom chamber 2 a of the arm hydraulic cylinder 2 through the oil passage 28. As a result, the arm 10 is actuated to the arm raising side.
[0127]
When the arm operation valve 6 is positioned at the arm raising position 6 a, the return pressure oil discharged from the head chamber 2 b of the arm hydraulic cylinder 2 passes through the oil passage 29 and the arm operation valve 6 to the return oil passage 35. Is output.
[0128]
Since the bucket operating lever 5 is now in the neutral position, the bucket dump pressure and the bucket tilt pressure are the same tank pressure. Therefore, the pilot pressure in each pilot oil passage 20a, 21a is a tank pressure, and the pilot pressure applied to each pilot port 36d, 36e of the regeneration rate increasing valve 36 is a tank pressure. As a result, the regeneration rate increase valve 36 is located at the shut-off position 36 c, and the pressure oil in the return oil passage 35 c is shut off by the regeneration rate increase valve 36. Accordingly, the return pressure oil flows only in the return oil passages 35a and 35b.
[0129]
Since the arm raising pressure is applied to the pilot port 43d of the fixed regeneration rate valve 43, the fixed regeneration rate valve 43 is located at the arm raising position 43a. When the fixed regeneration rate valve 43 is positioned at the arm raising position 43a, the pressure oil in the return oil passage 35a passes through the throttle 43f in the fixed regeneration rate valve 43 and is output to the return oil passage 35d. The pressure oil in the return oil passage 35 b passes through the throttle 43 g in the fixed regeneration rate valve 43 and flows into the inlet port of the pressure control valve 55.
[0130]
The pressure control valve 55 has a flow rate of pressure oil flowing through the return oil passage 35d and a pressure oil flowing through the return oil passage 35b at a predetermined ratio determined by the opening area of the throttle 43f and the opening area of the throttle 43g of the fixed regeneration rate valve 43. The flow rate (discharge flow rate to the tank 14) is divided. This diversion ratio is a diversion ratio for holding the bucket 11 horizontally.
[0131]
When the bucket operation valve 7 is located at the bucket dump position 7b, the return oil passage 51 is in communication with the oil passage 31 via the bucket operation valve 7. However, the oil passage 24 a communicating with the discharge port of the hydraulic pump 1 is blocked by the bucket operation valve 7 and is not in communication with the oil passage 31. That is, the hydraulic circuit in FIG. 1 is a series circuit.
[0132]
Next, the operation when the operation lever 5 in the bucket dumping direction is added to the operation of the arm operation lever 4 in the arm raising direction, that is, the operation during the combined operation will be described.
[0133]
When the bucket operating lever 5 is operated in the bucket dump direction, the bucket dump pressure in the pilot oil passage 20a becomes larger than the pilot pressure (tank pressure) in the pilot oil passage 21a. Therefore, the regeneration rate increasing valve 36 is located at the bucket dump position 36a. When the regeneration rate increase valve 36 is located at the bucket dump position 36a, the pressure oil in the return oil passage 35c passes through the regeneration rate increase valve 36 and joins the return oil passage 35d. This merge increases the flow rate of the pressure oil passing through the return oil passage 35d. For this reason, as the bucket dump pressure increases, the flow rate of the pressure oil divided into the return pressure oil 35d increases.
[0134]
Accordingly, as the bucket dump pressure increases, the flow rate of the pressure oil supplied to the bucket hydraulic cylinder 3 increases and the operating speed of the bucket 11 increases.
[0135]
At this time, the arm raising pressure acts on the pilot oil passage 18c, and the stroke restriction control valve 58 is located at the blocking position 58a. When the stroke restriction control valve 58 moves to the cutoff position 58a side, the piston 58c comes into contact with the spool of the bucket operation valve 7. For this reason, even if the bucket operation lever 5 is operated in the bucket dump direction and the bucket dump pressure is applied to the pilot port 7g of the bucket operation valve 7 via the pilot oil passage 22, the bucket operation valve 7 remains at the bucket dump position 7b. Therefore, the stroke is restricted by the piston 58c, and it does not move to the bucket dump position 7a.
[0136]
In this way, during the combined operation of the operation in the arm raising direction and the operation in the bucket dump direction, the bucket operation valve 7 holds the state located at the bucket dump position 7b. Even if the bucket dump pressure rises, the bucket operation valve 7 does not move to the bucket dump position 7a. That is, the oil passage 24 a communicating with the discharge port of the hydraulic pump 1 is blocked by the bucket operation valve 7 and is not in communication with the bottom chamber 3 a of the bucket hydraulic cylinder 3 via the oil passage 31. In this way, the state of the series circuit is maintained during the combined operation. Accordingly, the arm hydraulic cylinder 2 is driven by the discharge pressure oil of the hydraulic pump 1, and the bucket hydraulic cylinder 3 is driven only by the return pressure oil of the arm hydraulic cylinder 2. The bucket hydraulic cylinder 3 is not driven by the discharge pressure oil of the hydraulic pump 1. As a result, it is possible to operate the arm 10 which is the leading work machine during the combined operation at the same operating speed as when operating alone in the arm raising direction.
[0137]
However, when the operation amount of the arm operation lever 4 is reduced and the arm raising pressure is reduced, the stroke restriction state of the bucket operation valve 7 is released.
[0138]
That is, when the arm raising pressure in the pilot oil passage 18c decreases, the force by which the piston 58c pushes the bucket operation valve 7 is weakened. For this reason, when the bucket operating lever 5 is operated in the bucket dump direction and the bucket dump pressure is applied to the pilot port 7g of the bucket operating valve 7 via the pilot oil passage 22, the bucket operating valve 7 controls the stroke of the piston 58c. It moves to the bucket dump position 7a without being done. That is, the oil passage 24 a communicating with the discharge port of the hydraulic pump 1 is in a state of communicating with the bottom chamber 3 a of the bucket hydraulic cylinder 3 via the bucket operation valve 7 and the oil passage 31. Thus, the bucket hydraulic cylinder 3 is driven by the discharge pressure oil of the hydraulic pump 1.
[0139]
The series circuit has the advantage that the operating speed of the arm 10 that is the leading work machine does not decrease during the combined operation, but there is a problem that sufficient driving force cannot be obtained with the bucket 11 that is the subsequent work machine. In this embodiment, this problem is solved by switching from the series circuit to the parallel circuit when the load on the bucket 11 increases.
[0140]
As described above, when the operation amount of the arm operation lever 4 is reduced, the oil passage 24a communicates with the bottom chamber 3a of the bucket hydraulic cylinder 3. If the load pressure of the bucket hydraulic cylinder 3 exceeds a certain value in this state, the force acting on the pilot port 54b of the regeneration cancel valve 54 becomes equal to or greater than the spring force of the spring 54a. Therefore, the regeneration cancellation valve 54 is located on the open side. Therefore, the pressure oil in the return oil passage 51 is discharged to the tank 14 via the oil passage 51 a, the throttle 52, the oil passage 53, the regeneration cancellation valve 54, and the oil passage 25. For this reason, the pilot pressure acting on the pilot port 55g of the pressure control valve 55 via the oil passage 53 becomes the tank pressure, and accordingly, the pressure on the upstream side of the pressure control valve 55 also becomes the tank pressure. The flow rate is discharged to the tank 14. As a result, the pressure in the cylinder chamber 2b on the return side of the arm hydraulic cylinder 2 becomes the tank pressure. That is, the series circuit is switched to the parallel circuit.
[0141]
Further, in this embodiment, when the arm operation lever 4 and the bucket operation lever 5 are operated in the operation directions such as the arm raising direction and the bucket tilt direction, the spool stroke is not restricted by the bucket operation valve 7, and the hydraulic pump 1. The bucket hydraulic cylinder 3 is driven by the discharged pressure oil. That is, the bucket hydraulic cylinder 3 is driven by the parallel circuit.
[0142]
When the arm operation lever 4 and the bucket operation lever 5 are operated in the operation directions of the arm raising direction and the bucket tilt direction, an arm raising pressure and a bucket tilt pressure are generated in the pilot oil passages 22 and 23. Here, when the bucket tilt pressure becomes higher than the arm raising pressure, the stroke restriction control valve 58 is switched to the passage position 58b. Therefore, the pilot oil passage 18 c communicates with the tank 14 through the oil passage 18 d, the stroke restriction control valve 58, the oil passage 18 e, and the oil passage 25. As a result, the arm raising pressure in the pilot oil passage 18c is throttled by the throttle 18d and lowered to the tank pressure. For this reason, the arm raising pressure applied to the pilot port 7g of the bucket operation valve 7 via the pilot oil passage 22 decreases. On the other hand, bucket tilt pressure is applied to the pilot port 7h facing the bucket operation valve 7.
[0143]
For this reason, the bucket operation valve 7 moves to the bucket tilt position 7e by the bucket tilt pressure. When the bucket operation valve 7 is positioned at the bucket tilt position 7e, the hydraulic oil discharged from the hydraulic pump 1 is supplied to the bucket hydraulic cylinder 3 via the oil passages 24, 24b, the pressure compensation valve 9, the bucket operation valve 7, and the oil passage 32. To the head chamber 3b.
[0144]
For this reason, the bucket hydraulic cylinder 3 is driven by the pressure oil discharged from the hydraulic pump 1. That is, a parallel circuit is configured.
[0145]
The case where the arm operating lever 4 is operated in the arm raising direction has been described above. The same operation occurs when the arm operating lever 4 is operated in the arm lowering direction.
[0146]
One of the advantages of the series circuit is the regenerative function. For example, when the arm 10 falls by its own weight, the holding pressure on the bottom chamber 2 a side of the arm hydraulic cylinder 2 can be used to drive the bucket hydraulic cylinder 3. At this time, it is not necessary to increase the pressure oil from the hydraulic pump 1, and the bucket hydraulic cylinder 3 can be driven only by the load pressure (holding pressure) of the return pressure oil of the arm hydraulic cylinder 2.
[0147]
In this embodiment, a load sensing system is employed, and the operation is performed so that the differential pressure between the hydraulic pump 1 and the maximum load pressure of the hydraulic cylinders 2 and 3 becomes a constant value. Therefore, if the maximum load pressure is the load pressure of the bucket hydraulic cylinder 3, the discharge pressure of the hydraulic pump 1 is increased to a pressure obtained by adding a constant value to the load pressure of the bucket hydraulic cylinder 3. This leads to energy loss.
[0148]
According to this embodiment, the maximum load pressure is input to the shuttle valve 57 via the oil passages 27 and 27c. In addition, the pressure (regeneration pressure) of the return pressure oil from the arm hydraulic cylinder 2 is input to the shuttle valve 57 via the return oil passage 35 d and the oil passage 47. The shuttle valve 57 outputs the larger pressure of the regeneration pressure and the maximum load pressure. Here, when the regeneration pressure is larger than the maximum load pressure, the regeneration pressure is output from the check valve 57 and applied to the pressure reducing valve portion 9b of the pressure compensation valve 9 via the oil passage 27d. For this reason, the pressure reducing valve portion 9b operates in the closing direction, and the regeneration pressure is not output to the load sensing circuit. Since the discharge pressure of the hydraulic pump 1 does not increase corresponding to the regeneration pressure, energy loss can be eliminated.
[0149]
The first embodiment described above may be modified as appropriate.
[0150]
2 to 6 respectively show the second embodiment, the third embodiment, the fourth embodiment, the fifth embodiment, and the sixth embodiment in which a part of the hydraulic circuit of FIG. 1 is omitted. Show.
[0151]
As shown in FIG. 2, in the second embodiment, stroke restriction control valves 58 and 59 for restricting the stroke of the spool of the bucket operation valve 7 are omitted from the hydraulic circuit of FIG.
[0152]
As shown in FIG. 3, in the third embodiment, the stroke restriction control valves 58 and 59 for regulating the spool stroke of the bucket operation valve 7 are omitted from the hydraulic circuit of FIG. The switching valves 60, 61, 62, etc. to be performed are omitted.
[0153]
As shown in FIG. 4, in the fourth embodiment, the counter balance valves 39, 41, 42, 65 that limit the discharge amount of the return pressure oil of the bucket hydraulic cylinder 3 to the tank 14 in the hydraulic circuit of FIG. 1. Are omitted, the switching valves 60, 61, 62, and the like that perform floating control are omitted, and the stroke restriction control valves 58, 59 that restrict the spool stroke of the bucket operation valve 7 are omitted.
[0154]
As shown in FIG. 5, in the fifth embodiment, counter balance valves 39, 41, 42, 65 that limit the discharge amount of the return pressure oil of the bucket hydraulic cylinder 3 to the tank 14 in the hydraulic circuit of FIG. 1. Are omitted, the switching valves 60, 61, 62 and the like for performing the floating control are omitted, and the stroke restriction control valves 58, 59 for restricting the spool stroke of the bucket operation valve 7 are omitted. Further, in the sixth embodiment, in the hydraulic circuit of FIG. 1, the shuttle valve 50 for moving the bucket operation valve 7 to the bucket dump position 7b, 7a side in conjunction with the arm raising operation, interlocked with the arm lowering operation. Thus, the shuttle valve 49 and the like for moving the bucket operation valve 7 to the bucket tilt positions 7d and 7e are omitted.
[0155]
As shown in FIG. 6, in the sixth embodiment, the counter balance valves 39, 41, 42, 65 for limiting the discharge amount of the return pressure oil of the bucket hydraulic cylinder 3 to the tank 14 in the hydraulic circuit of FIG. Are omitted, the switching valves 60, 61, 62 and the like for performing the floating control are omitted, and the stroke restriction control valves 58, 59 for restricting the spool stroke of the bucket operation valve 7 are omitted. Further, in the seventh embodiment, in the hydraulic circuit of FIG. 1, the shuttle valve 50 for moving the bucket operation valve 7 to the bucket dump position 7b, 7a side in conjunction with the arm raising operation, interlocked with the arm lowering operation. Thus, the shuttle valve 49 and the like for moving the bucket operation valve 7 to the bucket tilt positions 7d and 7e side are omitted, and in the hydraulic circuit of FIG. For the pressure compensation valve 9 is omitted.
[0156]
However, in any case of the second to sixth embodiments, as in the first embodiment, when the load pressure of the bucket hydraulic cylinder 3 is small, the regeneration cancel valve 54 is positioned on the closed side, thereby causing a series circuit. The bucket hydraulic cylinder 3 can be driven by the return pressure oil of the arm hydraulic cylinder 2. For this reason, similarly to the first embodiment, it is possible to operate the work implement without reducing the operating speed of the leading arm 10 during the combined operation. Further, when the load pressure of the bucket hydraulic cylinder 3 is large, the regeneration cancel valve 54 is positioned on the open side to switch to the parallel circuit, and the bucket hydraulic cylinder 3 is driven by the discharge pressure oil of the hydraulic pump 1. Therefore, the bucket hydraulic cylinder 3 can be driven with the driving pressure corresponding to the load when the load on the latter bucket hydraulic cylinder 3 increases.
[0157]
As described above, according to each embodiment, the parallel circuit and the series circuit are switched by changing the flow rate of supplying the return pressure oil of the arm hydraulic cylinder 2 to the bucket hydraulic cylinder 3 according to the load state. Thus, it is possible to prevent a decrease in the working machine drive pressure and a decrease in the speed of the work machine.
[0158]
In the embodiment described above, the case where the present invention is applied to a construction machine has been described. However, the present invention can be applied to any hydraulic drive machine having a plurality of hydraulic actuators.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram of a first embodiment.
FIG. 2 is a hydraulic circuit diagram of a second embodiment.
FIG. 3 is a hydraulic circuit diagram of a third embodiment.
FIG. 4 is a hydraulic circuit diagram of a fourth embodiment.
FIG. 5 is a hydraulic circuit diagram of a fifth embodiment.
FIG. 6 is a hydraulic circuit diagram of a sixth embodiment.
FIG. 7 is a diagram illustrating a configuration of an operation lever device.
FIG. 8 is a diagram illustrating a configuration of a working machine of the construction machine according to the embodiment.
FIGS. 9A and 9B are diagrams conceptually showing a series circuit and a parallel circuit.
[Explanation of symbols]
1 ... Hydraulic pump
2 ... Hydraulic cylinder for arm
3 ... Hydraulic cylinder for bucket
4 ... Arm control lever
5 ... Bucket control lever
6 ... Operating valve for arm
7 ... Control valve for bucket
8, 9 ... Pressure compensation valve
10 ... arm
11 ... bucket
35, 35a, 35b, 35c, 35d, 51 ... return oil passage
36 ... Regeneration rate increase valve
43 ... Fixed regeneration rate valve
54 ... Regeneration cancel valve
55 ... Pressure control valve
40 ... Control lever device
49, 50 ... Shuttle valve

Claims (3)

The hydraulic pump (1) and the first and second hydraulic actuators that are driven by supplying the discharge pressure oil of the hydraulic pump (1) through the first and second pressure oil supply passages (24a, 24b) (2, 3) and first and second operating means (4, 5) provided corresponding to the first and second hydraulic actuators (2, 3), respectively, and switchable in two directions. In the actuator control device of the hydraulic drive machine
A return pressure oil supply path (35, 35a, 35d, 48, 51) for supplying discharged pressure oil discharged from the first hydraulic actuator (2) to the second hydraulic actuator (3);
When the operation amount of the first operation means (4) is equal to or greater than a predetermined amount, the return pressure oil supply passage (35, 35a, 35d) is connected to the hydraulic oil discharge side hydraulic chamber of the first hydraulic actuator (2). , 48, 51) and communicated with the hydraulic chamber on the pressure oil inflow side of the second hydraulic actuator (3) and discharged from the first hydraulic actuator (2) to the second hydraulic actuator (3). When the second operating means (5) is operated and the operation amount of the first operating means (4) is smaller than a predetermined amount, the pressure oil to be supplied is supplied. The discharge port of the hydraulic pump (1) communicates with the hydraulic chamber on the pressure oil inflow side of the second hydraulic actuator (3) and is discharged from the hydraulic pump (1) to the second hydraulic actuator (3). Pressure oil supply switching means for supplying pressure oil And 7,58,59),
Pressure oil supplied to the second hydraulic actuator (3) via the return pressure oil supply passage (35, 35a, 35d, 48, 51) according to the load pressure of the second hydraulic actuator (3). An actuator control device for a hydraulically driven machine, comprising: control means (54, 55) for controlling the fuel tank to communicate with the tank (14). The hydraulic pump (1) and the first and second hydraulic actuators that are driven by supplying the discharge pressure oil of the hydraulic pump (1) through the first and second pressure oil supply passages (24a, 24b) (2, 3) and first and second operating means (4, 5) provided corresponding to the first and second hydraulic actuators (2, 3), respectively, and switchable in two directions. In the actuator control device of the hydraulic drive machine
A return pressure oil supply path (35, 35a, 35d, 48, 51) for supplying discharged pressure oil discharged from the first hydraulic actuator (2) to the second hydraulic actuator (3);
When the load pressure of the second hydraulic actuator (3) is below a certain value and the first and second operating means (4, 5) are operated in a specific operating direction, The discharge pressure oil discharged from the first hydraulic actuator (2) is divided into a predetermined ratio, and the pressure oil divided into the predetermined ratio is returned to the return pressure oil supply path (35, 35a, 35d, 48, 51). To the second hydraulic actuator (3), and according to the change in the operation amount of the second operating means (5), the return pressure oil supply path (35, 35a, 35d, 48, 51) control means (36, 54, 55) for changing the ratio of the flow rate of the pressure oil supplied from the first hydraulic actuator (2) to the second hydraulic actuator (3) via the first hydraulic actuator ( 51). Hydraulic drive machine Tutor control device. The control means includes
When the second operation means (5) is operated in an operation direction other than the specific operation direction, the second hydraulic actuator supplies pressure oil via the second pressure oil supply path (24b). The actuator control device for a hydraulic drive machine according to claim 2, wherein control to be supplied to (3) is performed.

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