JP2007057001A - Hydraulic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic circuit having simple construction for recovering the energy of operating oil. <P>SOLUTION: The hydraulic circuit comprises: a plurality of hydraulic actuators; a hydraulic pump 31 to be driven by an engine 15 for forcibly feeding operating oil to the hydraulic actuators; operation selector valves 32 arranged between each of the hydraulic actuators and the hydraulic pump for selecting the operation of the hydraulic actuators; a hydraulic pressure regulating mechanism 37 using at least one hydraulic actuator as a hydraulic cylinder 22 for regulating a difference between pressure on the side of the discharge port of the hydraulic pump for forcibly feeding hydraulic pressure to the hydraulic cylinder and pressure on the side of a feed port of the hydraulic cylinder of the operation selector valve to be a predetermined value; and a regeneration pipe 36 for supplying the operating oil returned from a drain port of the hydraulic cylinder to the operation selector valve 32 to the hydraulic pump. The operation selector valve 32 for the hydraulic cylinder is formed integrally with the operation selector valves 201, 202, 203, 204, 205, 206, 207 for the other hydraulic actuators. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique of a hydraulic device that regenerates energy of hydraulic oil circulating in a hydraulic circuit.

  Conventionally, a hydraulic cylinder, a hydraulic pump driven by a drive source and pumping hydraulic oil to the hydraulic cylinder, a switching valve disposed between the hydraulic cylinder and the hydraulic pump, and switching an operation of the hydraulic cylinder; A hydraulic circuit comprising the above is well known.

  In general, such a hydraulic circuit switches hydraulic oil pumped from a hydraulic pump by a switching valve and supplies it to either the bottom chamber or the rod chamber of the hydraulic cylinder to extend or contract the hydraulic cylinder. is there. Further, in such a hydraulic circuit, as a result of the hydraulic oil being supplied to one of the bottom chamber or the rod chamber of the hydraulic cylinder, the hydraulic oil discharged from the other is once returned to the hydraulic oil tank via the return pipe, The hydraulic pump is configured to suck hydraulic oil from the hydraulic oil tank.

In addition, a hydraulic circuit provided with a so-called “load sensing function” is also known.
Here, the load sensing function refers to the hydraulic actuator by adjusting the difference between the pressure on the discharge port side of the hydraulic pump and the pressure on the oil supply port side of the hydraulic actuator within a predetermined range across the switching valve. It refers to a function of maintaining the flow rate of hydraulic oil supplied to the hydraulic actuator substantially constant regardless of the magnitude of the load (maintaining the operation speed of the hydraulic actuator substantially constant).
For example, as described in Patent Document 1.

Furthermore, a hydraulic motor disposed in the middle of the return pipe and driven by hydraulic oil passing through the return pipe, a generator driven by the hydraulic motor, and a battery connected to the generator, A hydraulic circuit having a function of recovering the energy (kinetic energy and potential energy) of the hydraulic oil passing through the return pipe as electric energy, that is, a so-called “energy regeneration function” is also known.
For example, as described in Patent Document 2.
JP 2000-257712 A JP 2001-207482 A

However, no hydraulic circuit that drives a hydraulic cylinder and has a load sensing function performs energy regeneration.
In addition, the hydraulic circuit having the “energy regeneration function” needs to be additionally provided with a hydraulic motor, a generator, a battery, and the like in order to achieve the energy regeneration function, resulting in an increase in manufacturing cost. .

  In addition, the hydraulic circuit is configured to regenerate energy for one hydraulic actuator. When other hydraulic actuators are provided, it is necessary to arrange them separately, and the hydraulic circuit becomes complicated and large. There is.

  In view of the above problems, the present invention provides a hydraulic circuit that can recover the energy of hydraulic oil with a simple configuration.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

That is, in claim 1,
A plurality of hydraulic actuators such as hydraulic cylinders and hydraulic motors;
A hydraulic pump driven by a drive source and pumping hydraulic oil to the hydraulic actuator;
An operation switching valve that is disposed between each of the hydraulic actuators and the hydraulic pump, and switches the operation of each of the hydraulic actuators;
Using the at least one hydraulic actuator as a hydraulic cylinder, the difference between the pressure on the discharge port side of the hydraulic pump that pumps hydraulic pressure to the hydraulic cylinder and the pressure on the oil supply port side of the hydraulic cylinder of the operation switching valve is adjusted to a predetermined value Hydraulic adjustment mechanism to
A regenerative pipe for supplying hydraulic oil returned from the oil cylinder exhaust port to the operation switching valve to the hydraulic pump;
The operation switching valve of the hydraulic cylinder and the operation switching valve of the other hydraulic actuator are integrally configured.

In claim 2,
A communication mechanism that is disposed between the hydraulic cylinder and the operation switching valve, and that communicates between a lower pressure of the bottom chamber and the rod chamber of the hydraulic cylinder and a drain pipe;
The communication mechanism is configured integrally with an operation switching valve of the hydraulic cylinder and an operation switching valve of the other hydraulic actuator.

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect of the present invention, the operation switching valve constituting the regenerative circuit that recovers the energy of the hydraulic oil returning from the hydraulic cylinder as the driving force of the hydraulic pump can be configured integrally with the other operation switching valve. The plurality of operation switching valves can be configured in a compact manner, and can be collectively gathered, the piping can be made short and simple, and the oil feeding resistance can be reduced.

  According to the second aspect of the present invention, since the operation switching valve and the communication mechanism are integrally formed, the valve mechanisms can be collectively arranged and the piping configuration can be configured short and easily.

  Below, the whole structure of the backhoe 1 which is an Example of the excavation work vehicle which comprises the hydraulic circuit which concerns on this invention using FIG. 1 and FIG. 2 is demonstrated.

  In addition, let the arrow direction be the front in FIG. The hydraulic circuit according to the present invention can be widely applied to hydraulic cylinders and other hydraulic actuators, and the application range is not limited to the excavation work vehicle as in this embodiment.

  As shown in FIG. 1, the backhoe 1 mainly includes a crawler type traveling device 2, a turning frame 3, a cabin 4, a working machine 5, and the like.

The crawler type traveling device 2 is a member constituting the lower structure of the backhoe 1, and is provided with a pair of left and right crawlers 11 and 11 (only the crawler 11 on the left side of the machine body is shown in FIG. 1).
Further, at the front part of the crawler type traveling device 2 of the present embodiment, there is a soil discharge plate 12 and a soil discharge plate cylinder 13 which is a hydraulic cylinder for rotating the soil discharge plate 12 in the vertical direction (FIG. 2). Are shown).

The swivel frame 3 is a member constituting the upper structure of the backhoe 1 and is pivotally attached to the upper part of the crawler type traveling device 2 via a swivel bearing 14.
The revolving frame 3 accommodates an engine 15 (shown in FIG. 2) as a driving source and other members, as well as a cabin 4 and a working machine 5.

  The cabin 4 is provided on the upper part of the revolving frame 3. The cabin 4 protects an operator who operates the backhoe 1 from wind and rain and direct sunlight, and a seat on which the operator is seated and a lever group (not shown) for various operations of the backhoe 1 Is provided.

  The work machine 5 mainly includes a bucket 16, an arm 17, a boom 18, a boom bracket 19, a bucket cylinder 20, an arm cylinder 21, a boom cylinder 22, a swing cylinder 25 (shown in FIG. 2), and the like, and the backhoe 1 turns. Provided at the front of the frame 3.

  The bucket 16 is an attachment for excavation work that forms the tip of the work machine 5, and its base is pivotally attached to the tip of the arm 17.

  The arm 17 is a rod-shaped member that forms the structure of the work machine 5, and a base portion of the arm 17 is pivotally attached to a tip end portion of the boom 18.

  The boom 18 is a member that forms the structure of the work machine 5. The boom 18 is bent in the middle and forward of the machine body, and its base is pivotally attached to the boom bracket 19.

The boom bracket 19 is a member that forms the base of the work machine 5, and its rear end is pivotally attached to the front end of the revolving frame 3.
A rod end portion of a swing cylinder (not shown) is pivotally attached to the right side portion of the boom bracket 19, and a cylinder side end portion is pivotally attached to the revolving frame 3. The swing cylinder is a hydraulic cylinder for rotating the working machine 5 to the left and right with respect to the revolving frame 3.

The bucket cylinder 20 is a hydraulic cylinder for rotating the bucket 16 with respect to the arm 17.
A cylinder end of the bucket cylinder 20 is pivotally attached to a bracket 17 a provided at the base of the arm 17. The rod end of the bucket cylinder 20 is pivotally attached to the bucket 16 via a link 23 and a rod 24.

The arm cylinder 21 is a hydraulic cylinder for rotating the arm 17 with respect to the boom 18.
A cylinder end portion of the arm cylinder 21 is pivotally attached to a bracket 18 a provided in the middle portion of the boom 18 and on a surface facing the cabin 4. The rod end of the arm cylinder 21 is pivotally attached to the bracket 17a.

The boom cylinder 22 is a hydraulic cylinder for rotating the boom 18 with respect to the revolving frame 3 (more precisely, the boom bracket 19).
The cylinder end of the boom cylinder 22 is pivotally attached to the front end of the boom bracket 19 so as to be rotatable. Further, the rod end of the boom cylinder 22 is pivotally attached to a bracket 18b provided in the middle of the boom 18 and on the surface opposite to the surface on which the bracket 18a is provided.
The swing cylinder 25 is interposed between the boom bracket 19 and the swing frame 3 and is a hydraulic cylinder for rotating the work machine 5 to the left and right with respect to the machine.

  Below, the structure of the hydraulic circuit 100 which is the Example of the hydraulic circuit based on this invention is demonstrated using FIG.

  The hydraulic circuit 100 is a hydraulic circuit provided in the backhoe 1 shown in FIG. 1 and mainly includes a boom cylinder 22, a hydraulic pump 31, an operation switching valve (control valve) 32, a feed pipe 33, and a pipe as shown in FIG. 34, a pipe 35, a regenerative pipe 36, a hydraulic pressure adjustment mechanism 37, an oil supply circuit 47, a fall prevention circuit 51, a pipe 54, a communication mechanism 55, and the like.

The boom cylinder 22 is a hydraulic cylinder for rotating the boom 18 with respect to the revolving frame 3 (more strictly speaking, the boom bracket 19) as described above.
A regenerative hydraulic circuit having the load sensing function of the present invention will be described using a boom cylinder 22.
As shown in FIG. 3, the boom cylinder 22 includes a cylinder having a space formed therein, a cylinder rod inserted into the cylinder from one end of the cylinder, and one end of the cylinder rod fixed to the inside of the cylinder. And a piston to be disposed.
The internal space of the cylinder is divided into a bottom chamber and a rod chamber by a piston that is provided at one end of the cylinder rod and is in airtight and slidable contact with the inner peripheral surface of the cylinder.
Here, the bottom chamber is the base of the cylinder, that is, the space on the end side where the cylinder rod does not protrude, and the rod chamber is the end of the cylinder, that is, the end side where the cylinder rod protrudes. Refers to space.

On the outer peripheral surface of the cylinder of the boom cylinder 22, a cylinder port 22a that is an opening that communicates the bottom chamber and the outside, and a cylinder port 22b that is an opening that communicates the rod chamber and the outside are provided.
Here, when the boom cylinder 22 extends, the hydraulic oil is supplied to the bottom chamber and the hydraulic oil is discharged from the rod chamber. Therefore, the cylinder port 22a on the bottom chamber side is an oil supply port, and the cylinder port on the rod chamber side. 22b is an oil drain port.
When the boom cylinder 22 contracts, hydraulic oil is supplied to the rod chamber and hydraulic oil is discharged from the bottom chamber. Therefore, the cylinder port 22b on the rod chamber side is the oil supply port and the cylinder port 22a on the bottom chamber side. Becomes the oil drain port.

  The boom cylinder 22 of this embodiment is a hydraulic cylinder in which a rod protrudes from one end of the cylinder, that is, a “one-sided rod type hydraulic cylinder”, but the hydraulic circuit of the present invention has rods from both ends of the cylinder. The present invention can also be applied to a protruding hydraulic cylinder, that is, a “double-sided rod type hydraulic cylinder”.

The hydraulic pump 31 pumps hydraulic oil to the boom cylinder 22. The hydraulic pump 31 is driven by the engine 15 as a drive source.
As shown in FIG. 4, the hydraulic pump 31 of this embodiment is provided with a discharge port 31 a that is an opening for discharging hydraulic oil and an intake port 31 b that is an opening for sucking hydraulic oil.
The hydraulic pump 31 is a so-called swash plate type axial piston pump, and changes the angle formed between the plate surface of the swash plate 31c swingably attached to the case and the axial direction of the rotary shaft 15a. It is possible to change the discharge amount of hydraulic oil when the rotation of 15a is rotated, and thus the discharge amount of hydraulic oil per unit time.
It should be noted that the “drive source” in the present application may have a configuration other than the engine as long as the hydraulic pump 31 can be driven, such as an electric motor.
Further, the hydraulic pump 31 of the present embodiment is an axial piston pump, but may be of any other configuration as long as it is a variable displacement pump that can change the discharge amount of hydraulic oil when the rotating shaft 15a is rotated once. .

  As shown in FIGS. 2 and 3, the operation switching valve 32 is disposed between the boom cylinder 22 and the hydraulic pump 31, and switches the flow path of the hydraulic oil pumped from the hydraulic pump 31 to the boom cylinder 22. , A switching valve for switching the operation of the boom cylinder 22.

  The operation switching valve 32 of this embodiment has a total of four ports, a primary side port 32a and 32b and a secondary side port 32c and 32d, and is operated by sliding a spool provided therein. (A) The “neutral state” in which the port 32a, the port 32c, and the port 32d are closed and the port 32b is in communication with the pilot pipe 41 is changed. “Cylinder extended state” in which the port 32a and the port 32c are communicated and the port 32b and the port 32d are communicated, and (C) the “cylinder in which the port 32a and the port 32c are communicated and the port 32b and the port 32c are communicated. It is possible to switch between “contracted state”.

The feed pipe 33 is a pipe that connects the discharge port 31 a of the hydraulic pump 31 and the port 32 a of the operation switching valve 32. The hydraulic oil pumped from the hydraulic pump 31 is supplied to the primary side of the operation switching valve 32 through the feed pipe 33.
The pipe 34 is a pipe that connects the secondary port 32 c of the operation switching valve 32, the fall prevention circuit 51, and the cylinder port 22 a on the bottom chamber side of the boom cylinder 22 via the pipe 54.
The piping 35 is a piping that connects the port 32 d on the secondary side of the operation switching valve 32 and the cylinder port 22 b on the rod chamber side of the boom cylinder 22.
The regenerative pipe 36 is a pipe that supplies hydraulic oil returned to the operation switching valve 32 from the oil drain port of the boom cylinder 22 to the hydraulic pump 31. 28 is a relief valve.

  When the operation switching valve 32 is in the “neutral state” of (A), the port 32 a is closed and the port 32 b is communicated with the pilot pipe 41. A switching valve 26 and a relief valve 27 are connected in parallel between a feed pipe 33 communicating between the hydraulic pump 31 and the port 32a and a discharge pipe 56 serving as a drain pipe communicating with the hydraulic oil tank 46. When the hydraulic pressure between the feed pipe 33 and the regenerative pipe 36 is higher than a predetermined pressure, the switching valve 26 is switched, and the hydraulic oil pumped from the hydraulic pump 31 passes through the feed pipe 33 and the switch valve 26 to the oil discharge pipe. 56 is returned to the hydraulic oil tank 46. Further, the port 32c and the port 32d are closed, and the hydraulic oil filled in the bottom chamber and the rod chamber of the boom cylinder 22 is confined. As a result, the cylinder rod of the boom cylinder 22 is fixed with a predetermined protrusion amount with respect to the cylinder, and the boom cylinder 22 is held with a predetermined length. In addition, the relief valve 27 is returned from the oil discharge pipe 56 to the hydraulic oil tank 46 when the hydraulic pressure exceeds the set hydraulic pressure, such as when an overload is applied during expansion or contraction.

When the operation switching valve 32 is in the “cylinder extended state” of (B), the port 32a and the port 32c communicate with each other, and the hydraulic oil pumped from the hydraulic pump 31 is fed through the feed pipe 33, the operation switching valve 32, the pipe 34, It is supplied to the bottom chamber of the boom cylinder 22 through the fall prevention circuit 51 and the pipe 54.
Further, the hydraulic oil filled in the rod chamber of the boom cylinder 22 is communicated with the port 32b and the port 32d, and is supplied to the hydraulic pump 31 through the pipe 35, the operation switching valve 32, and the regenerative pipe 36.
As a result, the cylinder rod of the boom cylinder 22 protrudes from the cylinder, and the boom cylinder 22 extends.

When the operation switching valve 32 is in the “cylinder contraction state” of (C), the port 32a and the port 32d communicate with each other, and hydraulic fluid pumped from the hydraulic pump 31 passes through the feed pipe 33, the operation switching valve 32, and the pipe 35. Then, it is supplied to the rod chamber of the boom cylinder 22.
Further, the hydraulic fluid that is communicated with the port 32b and the port 32c and is filled in the bottom chamber of the boom cylinder 22 passes through the pipe 54, the fall prevention circuit 51, the pipe 34, the operation switching valve 32, and the regenerative pipe 36, and is a hydraulic pump. 31.
As a result, the cylinder rod of the boom cylinder 22 is immersed in the cylinder, and the boom cylinder 22 contracts.

Hereinafter, the configuration of the hydraulic pressure adjustment mechanism 37 will be described with reference to FIGS. 2 and 4.
The hydraulic adjustment mechanism 37 adjusts a difference ΔP between the pressure P1 on the discharge port 31a side of the hydraulic pump 31 and the pressure P2 on the oil supply port side of the boom cylinder 22 to a predetermined value.
The hydraulic adjustment mechanism 37 of the present embodiment includes a hydraulic adjustment valve 38, a pipe 39, a pilot pipe 40, a pilot pipe 41, an adjustment cylinder 42, a pipe 43, a return pipe 44, and the like.

  The hydraulic pressure adjusting valve 38 includes the pressure on the discharge port 31a side of the hydraulic pump 31 (in other words, the pressure on the feed pipe 33), the pressure on the port 32b side when the operation switching valve 32 is neutral, and the operation switching valve 32 is a cylinder. At the time of operation, the pressure on the oil supply port side of the boom cylinder 22 (in other words, the pipe 34 when the boom cylinder 22 is extended or when the boom cylinder 22 is contracted) is sandwiched between the throttles provided in the operation switching valve 32. This is a pilot-type switching valve that switches the flow path of hydraulic oil passing through the inside based on the difference between the pressure of the piping 35).

The hydraulic pressure adjusting valve 38 of this embodiment includes three ports 38a, 38b, and 38c, and by changing the flow path of the hydraulic oil inside the hydraulic pressure adjusting valve 38 by sliding a spool provided therein, (A) Switch between “state A” in which the port 38a and the port 38b are communicated to block the port 38c, and (b) “state B” in which the port 38a and the port 38c are communicated to block the port 38b. It is possible.
A pilot pipe 40 and a pilot pipe 41 are connected to the operation portions at both ends of the spool of the hydraulic pressure adjusting valve 38, respectively.

  The pipe 39 is a pipe that connects the port 38 b of the hydraulic pressure regulating valve 38 and the middle part of the feed pipe 33.

The pilot pipe 40 is a pipe that connects one end of the spool operation portion of the hydraulic pressure regulating valve 38 and a midway portion of the feed pipe 33.
Therefore, the pressure of the pilot pipe 40 (more strictly, the pressure of the hydraulic oil in the pilot pipe 40) is substantially the same as the pressure of the feed pipe 33, and hence the pressure P1 on the discharge port 31a side of the hydraulic pump 31.

The pilot pipe 41 is connected to the other end of the spool operating portion of the hydraulic pressure regulating valve 38 and a midway portion of the path that communicates the port 32a with another port (port 32b, port 32c, or port 32d) inside the operation switching valve 32. , Are pipes for connecting.
Accordingly, the pressure of the pilot pipe 41 (more precisely, the pressure of the hydraulic oil in the pilot pipe 41) is the pressure of the pipe 34 when the operation switching valve 32 is in the cylinder extension state of (B), (C) When the cylinder is in the contracted state, the pressure of the pipe 35, and thus the pressure P2 on the oil supply port side of the boom cylinder 22 is substantially the same.
Further, when the operation switching valve 32 is in the neutral state (A), the pressure of the pilot pipe 41 is substantially the same as the pressure of the regenerative pipe 36 and consequently the pressure on the suction port 31b side of the hydraulic pump 31.

The adjustment cylinder 42 is a single-acting hydraulic cylinder, and a cylinder port 42c, which is an opening that communicates the bottom chamber and the outside, is provided on the outer peripheral surface of the cylinder of the adjustment cylinder 42.
The tip of the cylinder rod 42b is connected to the swash plate 31c of the hydraulic pump 31, and the angle formed between the plate surface of the swash plate 31c of the hydraulic pump 31 and the axial direction of the rotary shaft 15a is changed by the expansion / contraction of the adjustment cylinder 42. To do.

The pipe 43 is a pipe that connects the port 38 a of the hydraulic adjustment valve 38 and the cylinder port 42 c of the adjustment cylinder 42.
The return pipe 44 is a pipe that connects the port 38 c of the hydraulic pressure adjustment valve 38 and the suction pipe 50.
The suction pipe 50 is a pipe having one end connected to the suction side of the pumps 31, 131, and 71 and the other end arranged inside the hydraulic oil tank 46. The hydraulic oil tank 46 is a container for storing hydraulic oil.

Hereinafter, the operation of the hydraulic pressure adjustment mechanism 37 will be described with reference to FIGS. 2 and 4.
A pilot pipe 40 is connected to one end of a spool operation section provided inside the hydraulic pressure adjusting valve 38, and a pilot pipe 41 is connected to the other end of the spool operation section. The spool slides based on the difference. The spring 38d urges the spool in the same direction as the direction in which the spool slides due to the pressure of the pilot pipe 41.

  When the difference ΔP (= P1−P2) between the pressure P1 on the discharge port 31a side of the hydraulic pump 31 and the pressure P2 on the oil supply port side of the boom cylinder 22 becomes larger than the “predetermined value”, the pressure in the pilot pipe 40 Thus, the force that pushes the spool is greater than the force that pushes the spool due to the pressure of the spring 38d and the pilot pipe 41. Then, the spool provided inside the hydraulic pressure adjusting valve 38 slides in the direction of “state A” in FIG.

  When the difference ΔP (= P1−P2) between the pressure P1 on the discharge port 31a side of the hydraulic pump 31 and the pressure P2 on the oil supply port side of the boom cylinder 22 becomes smaller than the “predetermined value”, the pressure in the pilot pipe 40 Thus, the force for pushing the spool is smaller than the force for pushing the spool by the pressure of the spring 38d and the pilot pipe 41. Then, the spool provided in the hydraulic pressure adjusting valve 38 slides in the direction of “state B” in FIG.

Thus, the force of pushing the spool by the spring 38d corresponds to the “predetermined value”.
Therefore, the “predetermined value” can be adjusted by adjusting the spring constant of the spring 38d.

When the hydraulic control valve 38 is in the “state A” of (a), the port 38 a and the port 38 b are communicated, and a part of the hydraulic oil in the feed pipe 33 passes through the pipe 39, the hydraulic control valve 38, and the pipe 43. It is supplied to the bottom chamber of the adjustment cylinder 42.
As a result, the adjustment cylinder 42 is extended, and the swash plate 31c of the hydraulic pump 31 is discharged in the direction in which the plate surface is orthogonal to the axial direction of the rotary shaft 15a, that is, the hydraulic oil discharge amount per unit time of the hydraulic pump 31. Tilt in the direction of decreasing.
When the hydraulic oil discharge amount per unit time of the hydraulic pump 31 is reduced, the difference ΔP between the pressure P1 on the discharge port 31a side of the hydraulic pump 31 and the pressure P2 on the oil supply port side of the boom cylinder 22 is reduced.

When the hydraulic pressure adjusting valve 38 is in the “state B” of FIG. 5B, the port 38a and the port 38c are communicated, and the hydraulic oil filled in the bottom chamber of the adjusting cylinder 42 is connected to the piping 43, the hydraulic pressure adjusting valve 38, and the return piping. 44, sucked into the hydraulic pump through the suction pipe 50;
As a result, the adjustment cylinder 42 contracts, and the swash plate 31c of the hydraulic pump 31 discharges hydraulic oil in a direction in which the plate surface is parallel to the axial direction of the rotary shaft 15a, that is, the unit time of the hydraulic pump 31. Tilt in the direction of increasing the amount.
When the hydraulic oil discharge amount per unit time of the hydraulic pump 31 is increased, the difference ΔP between the pressure P1 on the discharge port 31a side of the hydraulic pump 31 and the pressure P2 on the oil supply port side of the boom cylinder 22 increases.

  By operating the hydraulic pressure adjustment mechanism 37 as described above, the difference ΔP between the pressure P1 on the discharge port 31a side of the hydraulic pump 31 and the pressure P2 on the oil supply port side of the boom cylinder 22 is adjusted to a predetermined value.

The speed of expansion or contraction of the boom cylinder 22 is proportional to the flow rate Q of hydraulic oil supplied to the bottom chamber or rod chamber of the boom cylinder 22. A so-called “throttle” is provided in the middle of the hydraulic oil pumping path (in the present embodiment, the path from the hydraulic pump 31 to the bottom chamber or rod chamber of the boom cylinder 22 via the operation switching valve 32). When there is a pressure difference ΔP between the upstream side and the downstream side of the throttle, the following equation (1) is established.
Q = α × A × (ΔP / ρ) ^0.5 formula (1)
Here, α is a coefficient, A is the cross-sectional area of the “throttle” portion, and ρ is the density of the hydraulic oil.
In the above formula (1), α is a constant specific to the hydraulic circuit 100, and ρ is a constant specific to the type of hydraulic oil used.

  The configuration of the hydraulic pressure adjustment mechanism 37 is not limited to the present embodiment, and the pressure P1 on the discharge port 31a side of the hydraulic pump 31 and the pressure on the oil supply port side of the boom cylinder 22 with the operation switching valve 32 interposed therebetween. Another configuration may be used as long as the difference ΔP with P2 can be adjusted to a predetermined value.

Below, the structure of the oil replenishment circuit 47 is demonstrated using FIG. 2, FIG.
The oil replenishment circuit 47 replenishes the shortage of hydraulic oil circulating in the hydraulic circuit 100.
The oil supply circuit 47 includes a check valve 49 provided in a pipe 48 between the regenerative pipe 36 and the suction pipe 50.

  The pipe 48 is a pipe connected to the middle part of the regenerative pipe 36 and the other end connected to the middle part of the suction pipe 50. A check valve 49 is arranged in the middle of the pipe 50. The check valve 49 opens only when the pressure on the regenerative pipe 36 side is lower than the pressure on the suction pipe 50 side, and the inflow resistance at the time of suction is as small as possible. I am doing so.

Hereinafter, the operation of the oil supply circuit 47 will be described with reference to FIGS.
When the hydraulic oil circulating in the hydraulic circuit 100 is insufficient, the pressure on the cylinder port 22a side or the pressure on the cylinder port 22b side (the pressure in the pipe 34 or the pressure in the pipe 35) of the boom cylinder 22 is usually reduced.

For example, when the pressure on the cylinder port 22a side of the boom cylinder 22 becomes equal to or lower than the predetermined value, the check valve 49 is opened, and the hydraulic oil stored in the hydraulic oil tank 46 passes through the suction pipe 50, the pipe 48, and the check valve 49. Inhaled and replenished. In other words, it is self-sufficient.
When the pressure in the regenerative piping 36 of the hydraulic circuit 100 is equal to or higher than a predetermined value, the check valve 49 remains closed to prevent hydraulic fluid from flowing out.

  The main reason for the shortage of hydraulic fluid circulating inside the hydraulic circuit 100 is that the boom cylinder 22 is a one-side rod type hydraulic cylinder, so that the cylinder port is the same even if the cylinder rod slide amount is the same. This is because the amount of hydraulic oil passing through 22a is different from the amount of hydraulic oil passing through cylinder port 22b.

The configuration of the fall prevention circuit 51 will be described with reference to FIG.
The fall prevention circuit 51 includes a logic valve 52 and a switching valve 53 and is disposed between the pipes 34 and 54.

  The primary port 52 a of the logic valve 52 is communicated with the pipe 34, and the secondary port 52 b is communicated with the cylinder port 22 a via the pipe 54.

The switching valve 53 is a 3-port 2-position switching pilot-type switching valve having ports 53a, 53b, and 53c, a position where the ports 53a and 53c are connected to block the port 53b, and the ports 53a and 53b are connected. The position can be switched to a position where it communicates and is connected to the port 53c via a check valve.
The port 53a communicates with the back pressure side of the logic valve 52 through a pilot oil passage, and the port 53b communicates with the pipe 54 through a pilot oil passage. The port 53c communicates with the hydraulic oil tank 46 through a pilot oil passage.
One end of the operation portion on both sides of the spool is connected to the lower operation valve 80 via a pilot oil passage, and the other end of the operation portion is connected to the hydraulic oil tank 46.

The operation of the fall prevention circuit 51 will be described.
When the boom 18 is raised and rotated, the operation valve 80 is switched by operating the operation lever, and when the pressure oil is fed from the pilot oil passage to the operation portion of the operation switching valve 32 and pushed by the spool, the piping is switched. The pressure oil is fed to 34, enters the port 52 a of the logic valve 52, pushes the valve body, and is fed from the port 52 b to the cylinder port 22 a of the boom cylinder 22 through the pipe 54 to extend the boom cylinder 22. When this extended state is maintained with the operating lever in the neutral position, hydraulic pressure is applied from the pipe 54 via the pilot oil passage to the back pressure side of the logic valve 52 from the port 53b of the switching valve 53 via the port 53a. 52 is closed, the reduction of the boom cylinder 22 is prevented, and the natural fall can be prevented.

  In order to rotate the boom 18 downward, the operation valve 80 is switched by operating the operation lever, and the pressure oil is supplied from the pilot oil passage to the operation portion of the operation switching valve 32 and the operation portion of the switching valve 53, respectively. When the spool is pushed and switched, the pipe 34 communicates with the regenerative pipe 36. At the same time, the back pressure side of the logic valve 52 is drained, the logic valve 52 is opened, and the hydraulic oil from the cylinder port 22a on the bottom chamber side is opened. The boom cylinder 18 can be reduced by flowing to the suction port 31b of the hydraulic pump 31 via the pipes 54 and 34.

Next, the structure of the communication mechanism 55 is demonstrated using FIG. 2, FIG.
The communication mechanism 55 is disposed between the boom cylinder 22 and the operation switching valve 32, and communicates the lower pressure of the cylinder bottom chamber and the cylinder rod chamber with the oil discharge pipe 56. Here, the oil discharge pipe 56 is a pipe having one end connected to the communication mechanism 55 and the other end connected to the return pipe 45.
The communication mechanism 55 mainly includes an excess flow discharge valve 57, a pipe 58, a pipe 59, a pipe 65, a pilot pipe 60, a pilot pipe 61, an intake / exhaust circuit in which a throttle 66 and a check valve 67 are connected in parallel, a pipe 56, and the like. To do.

  The surplus flow discharge valve 57 is a pilot-type switching valve that switches the flow path of the internal hydraulic oil based on the pressure in the bottom chamber of the boom cylinder 22 and the pressure in the rod chamber.

The surplus flow discharge valve 57 of this embodiment is provided with three ports 57a, 57b, and 57c, and the flow path of hydraulic oil inside the surplus flow discharge valve 57 is changed by sliding a spool provided inside. (Α) a “closed state” in which all the ports 57a, 57b, and 57c are closed, (β) a “bottom chamber open state” in which the port 57a and the port 57b are connected and the port 57c is closed, and (γ) It is possible to switch between the “rod chamber open state” in which the port 57a and the port 57c communicate with each other and the port 57b is closed.
A pilot pipe 60 and a pilot pipe 61 are respectively connected to the operation portions at both ends of the spool of the surplus flow discharge valve 57 and are urged in a neutral direction by a spring.

The pipe 58 is a pipe that connects the port 57 b and the middle part of the pipe 34. The pipe 59 is a pipe that connects the port 57c and a midway part of the pipe 35.
The throttle 66 and the check valve 67 are connected in parallel. One end of the parallel circuit is connected to the port 57 a via the pipe 65, and the other end of the parallel circuit is connected to the oil discharge pipe 56.

The pilot pipe 60 is a pipe that connects one end of the spool operation portion of the surplus flow discharge valve 57 and the pipe 34.
Accordingly, the pressure in the pilot pipe 60 is substantially the same as the pressure in the pipe 34 and, consequently, the pressure in the bottom chamber of the boom cylinder 22.
The pilot pipe 61 is a pipe that connects the other end of the spool operation portion of the surplus flow discharge valve 57 and the pipe 35.
Therefore, the pressure of the pilot pipe 61 is substantially the same as the pressure of the pipe 35 and consequently the rod chamber of the boom cylinder 22.

When the pressure in the bottom chamber of the boom cylinder 22 and the pressure in the rod chamber are substantially the same, the surplus flow discharge valve 57 is in the closed state (α).
In the present embodiment, as a case where the pressure in the bottom chamber of the boom cylinder 22 and the pressure in the rod chamber occur in substantially the same state, the work machine 5 is not loaded and the boom cylinder 22 is stopped. Can be mentioned.

When the pressure in the bottom chamber of the boom cylinder 22 is lower than the pressure in the rod chamber, the spool is pushed by the pressure oil from the pilot oil passage 61, and the surplus flow discharge valve 57 enters the bottom chamber open state of (β). In the “state”, the hydraulic oil filled in the bottom chamber of the boom cylinder 22 is sent from the pipe 34 to the suction port 31b side of the hydraulic pump 31 via the operation switching valve 32, and the surplus flow is supplied to the pipe. 58, the excess flow discharge valve 57, the pipe 65, and the oil discharge pipe 56 are returned to the hydraulic oil tank 46.
In the “cylinder extended state”, the hydraulic oil filled in the rod chamber of the boom cylinder 22 is fed from the pipe 35 to the suction port 31b side of the hydraulic pump 31 through the operation switching valve 32. The deficient flow is sucked (supplied) from the hydraulic oil tank 46 through the oil discharge pipe 56, the pipe pipe 65, the surplus flow discharge valve 57, and the pipe 58.

  The intake / exhaust circuit including the throttle 66 is disposed between the surplus flow discharge valve 57 and the oil discharge pipe 56, thereby preventing cavitation. That is, when the boom cylinder 22 is extended or contracted, the pressure of the pipe 34 or the pipe 35 is increased and the pressure of the pilot pipe 60 or the pilot pipe 61 is also increased and communicated with the oil discharge pipe 56 serving as a drain pipe. When the pressure fluctuates, the pressure between the pipe 34 and the pipe 35 may reverse, and the surplus flow discharge valve 57 may suddenly reciprocate and cavitation may occur. However, the oil passage leading to the drain pipe may be throttled 66. Therefore, the flow is restricted, the hydraulic pressure fluctuation of the pipe 58 or the pipe 59 is reduced, and cavitation can be suppressed.

As a case where the pressure in the bottom chamber of the boom cylinder 22 is lower than the pressure in the rod chamber, for example, in a normal excavation operation, the boom cylinder 22 is used when digging up a groove or breaking a mountain with the bucket 16. The hydraulic oil filled in the bottom chamber is returned to the hydraulic oil tank 46 via the surplus flow discharge valve 57 and the oil discharge pipe 56.
Alternatively, when lowering from a step or when lowering a crawler on one side by rotating the bucket to the side for maintenance work, the boom cylinder 22 may be extended and the operation discharged from the rod side chamber The amount entering the bottom side chamber is larger than the oil amount. At this time, since the shortage cannot be replenished from the check valve 49, there is a shortage in the bottom chamber via the oil discharge pipe 56, the check valve 67, the pipe 65, the surplus flow discharge valve 57, the pipe 58, and the pipe 34. To be replenished.

When the pressure in the rod chamber of the boom cylinder 22 is lower than the pressure in the bottom chamber, the surplus flow discharge valve 57 is opened in the (γ) rod chamber, and the hydraulic oil filled in the rod chamber of the boom cylinder 22 is piped. 35, the pipe 59, the surplus flow discharge valve 57, the pipe 65, the throttle 66, and the oil discharge pipe 56, and is returned to the hydraulic oil tank 46.
As a case where the pressure in the rod chamber of the boom cylinder 22 is lower than the pressure in the bottom chamber, for example, when the boom cylinder 22 is extended for lifting in normal excavation work, the hydraulic oil discharged from the rod side chamber Since the amount of inflow into the bottom chamber is insufficient only by the amount, the shortage is replenished to the regenerative pipe 36 via the suction pipe 50, the check valve 49, and the pipe 48.
Alternatively, when the boom cylinder 22 is contracted to lower the boom 18, the surplus flow discharge valve 57 is switched, and the pipe 35, the pipe 59, the surplus flow discharge valve 57, the throttle 66, and the oil discharge pipe 56 are switched. The surplus is discharged.

The operation of the communication mechanism 55 as described above has the following effects.
That is, since the boom cylinder 22 is a one-side rod type hydraulic cylinder, the amount of hydraulic oil that passes through the cylinder port 22a and the amount of hydraulic oil that passes through the cylinder port 22b even if the amount of sliding of the cylinder rod of the boom cylinder 22 is the same. And is different. On the other hand, since hydraulic fluid is an incompressible fluid (fluid density is constant regardless of time and place), the discharge amount and suction amount of hydraulic fluid at a certain time during the operation of the hydraulic pump 31 are substantially the same. is there.
Therefore, when the hydraulic oil discharged from the hydraulic cylinder is once returned to the hydraulic oil tank as in the conventional hydraulic circuit and the hydraulic pump sucks the hydraulic oil from the hydraulic oil tank, there is no particular problem. As described above, when the hydraulic oil discharged from the boom cylinder 22 is not returned to the hydraulic oil tank and is directly supplied by the regenerative pipe 36, an imbalance in the flow rate of the hydraulic oil occurs in the hydraulic circuit 100. This will increase the pressure imbalance within the circuit 100.
In this embodiment, since the hydraulic circuit 100 includes the communication mechanism 55, a part of the hydraulic oil circulating inside the hydraulic circuit 100 is discharged or replenished to the outside of the hydraulic circuit 100, and the check valve 49 Therefore, it is possible to eliminate the imbalance in the flow rate of the hydraulic oil in the hydraulic circuit 100.

  Note that the configuration of the communication mechanism 55 is not limited to the present embodiment, and is arranged between the boom cylinder 22 and the operation switching valve 32. Another configuration may be used as long as the replenishment circuit 47 or the oil discharge pipe 56 can communicate with each other.

As described above, the hydraulic circuit 100 of this embodiment is
The boom cylinder 22, a hydraulic pump 31 that is driven by the engine 15 and feeds hydraulic oil to the boom cylinder 22, and an operation switching valve 32 that is disposed between the boom cylinder 22 and the hydraulic pump 31 and switches the operation of the boom cylinder 22. A hydraulic adjustment mechanism 37 that adjusts the difference between the pressure P1 on the discharge port 31a side of the hydraulic pump 31 and the pressure P2 on the oil supply port side of the boom cylinder 22 to a predetermined value across the operation switching valve 32, and a boom cylinder And a regenerative pipe 36 for supplying the hydraulic oil returned from the oil discharge port 22 to the operation switching valve 32 to the hydraulic pump 31.

With this configuration, the hydraulic pump 31 is supplied with hydraulic oil “pressure-fed” by the boom cylinder 22 via the regenerative pipe 36.
As a result, the hydraulic pump 31 functions as a motor by the high-pressure hydraulic oil, and supplies hydraulic oil to hydraulic actuators 13, 20, 21, 25, 62, 63, 64 of the hydraulic circuit 200 described later. To drive part or all of
Therefore, when the hydraulic pumps 31 and 131 of the hydraulic circuits 100 and 200 are driven by the same engine, the driving load of the hydraulic pump 131 is reduced by the motor operation of the hydraulic pump 31, so that the overall work load of the engine is reduced. The fuel efficiency is improved.
That is, it is possible to recover part or all of the energy (kinetic energy, potential energy) of the hydraulic oil returning from the boom cylinder 22 with a simple configuration as the driving force of the hydraulic pump.
Further, the hydraulic circuit 100 can operate a hydraulic cylinder that is operated by hydraulic oil fed from the hydraulic pump 31 at a substantially constant speed regardless of the magnitude of the load.

Further, in the hydraulic circuit 100 of the present embodiment, the boom cylinder 22 is a one-side rod type hydraulic cylinder, and is disposed between the boom cylinder 22 and the operation switching valve 32, and the pressure in the bottom chamber and the rod chamber is Is provided with a communication mechanism that communicates the lower one with the oil discharge pipe 56.
With this configuration, even when the boom cylinder 22 is a one-side rod type hydraulic cylinder, it is possible to eliminate an imbalance in the flow rate of hydraulic oil in the hydraulic circuit 100.

  The operation switching valve 32 is integrally formed with operation switching valves 201, 202, 203, 204, 205, 206, and 207 of the hydraulic circuit 200 described later. In other words, the operation switching valves 32, 201, 202, 203, 204, 205, 206, and 207 have substantially the same configuration, and are housed in valve cases, arranged in a stacked manner, and assembled together by bolts or the like. As a compact structure, it is housed in the dashboard of the control section, below the steps, and the like.

  Specifically, the operation switching valve 32 is stored in a valve case 90, the switching valve 26 and the relief valve 27 are stored in a valve case 98, the operation switching valve 201 is stored in a valve case 91, and the operation switching valve 202 is The operation switching valve 203 is stored in the valve case 93, the operation switching valve 204 is stored in the valve case 94, the operation switching valve 205 is stored in the valve case 95, and the operation switching valve 206 is stored in the valve case 92. The operation switching valve 207 is housed in the valve case 97. These valve cases 90, 91, 92, 93, 94, 95, 96, 97, and 98 are laminated in the left-right direction or the up-down direction and are integrally formed.

  Further, the valve case 90 may be configured integrally with an excess flow discharge valve 57, a throttle 66, a check valve 67, a logic valve 52, a switching valve 53, and the like constituting the communication mechanism 55. Is possible. That is, the operation switching valve 32, the communication mechanism 55, the drop prevention circuit 51, and the operation switching valves 201, 202, 203, 204, 205, 206, and 207 of other actuators can be integrally configured.

  By configuring in this way, it is possible to arrange the valve case in a compact manner and easily perform hydraulic piping, and it is possible to make the drain oil passage and the oil passage from the pump in common, the piping route can be shortened, and the loss is also reduced. It can be reduced.

Below, the structure of the hydraulic circuit 200 is demonstrated using FIG.
The hydraulic circuit 200 is a hydraulic circuit provided in the backhoe 1 in the same manner as the hydraulic circuit 100, and as shown in FIG. 2, the earth discharge plate cylinder 13, the bucket cylinder 20, the arm cylinder 21, and the swing cylinder 25 mainly serving as hydraulic actuators. , Turning motor 62, left travel motor 63, right travel motor 64, hydraulic pump 131, suction pipes 136a and 136b, operation switching valve unit 132, feed pipe 133, operation switching valve unit 132 and piping connecting the actuator. And a hydraulic pressure adjusting mechanism 137, a discharge amount suppressing mechanism 70, and the like.
Here, the hydraulic cylinders such as the earth discharging plate cylinder 13, the bucket cylinder 20, and the arm cylinder 21 and the hydraulic motors such as the turning motor 62, the left traveling motor 63, and the right traveling motor 64 are all operated by hydraulic pressure. Yes, and included in the “hydraulic actuator” in this application.

The earth discharge plate cylinder 13 is a hydraulic cylinder for rotating the earth removal plate 12 in the vertical direction as described above, and the bucket cylinder 20 is an oil pressure for rotating the bucket 16 relative to the arm 17 as described above. The arm cylinder 21 is a hydraulic cylinder for rotating the arm 17 with respect to the boom 18 as described above.
A cylinder port that is an opening that communicates the bottom chamber and the outside and a cylinder port that is an opening that communicates the rod chamber and the outside are provided on the outer peripheral surface of the cylinder of each cylinder.

  The turning motor 62 is a hydraulic motor for turning the turning frame 3 with respect to the crawler type traveling device 2. The turning motor 62 has two ports, and changes the port from which hydraulic oil is supplied. By doing so, it is possible to change the turning direction of the turning frame 3.

  The left traveling motor 63 and the right traveling motor 64 are hydraulic motors that are provided in the crawler traveling device 2 and rotationally drive the crawlers 11 on both the left and right sides of the body of the backhoe 1, and each traveling motor has two ports. It is possible to change the rotation direction of the crawlers 11 on both the left and right sides of the body of the backhoe 1 by changing from which port the hydraulic oil is supplied.

The hydraulic pump 131 pumps hydraulic oil to the earth discharging plate cylinder 13, the bucket cylinder 20, the arm cylinder 21, the swing cylinder 25, the turning motor 62, the left traveling motor 63 and the right traveling motor 64. The hydraulic pump 131 is driven by the engine 15 as a drive source.
The hydraulic pump 131 of this embodiment is provided with a discharge port 131a that is an opening for discharging hydraulic oil and a suction port 131b that is an opening for sucking hydraulic oil.
The hydraulic pump 131 is a so-called swash plate type axial piston pump, and changes the angle formed by the plate surface of the swash plate 131c swingably attached to the case and the axial direction of the rotary shaft 15a. It is possible to change the discharge amount of hydraulic oil when the rotation of 15a is rotated, and thus the discharge amount of hydraulic oil per unit time.
The hydraulic pump 131 of the present embodiment is an axial piston pump, but may be of any other configuration as long as it is a variable displacement pump that can change the discharge amount of hydraulic oil when the rotating shaft 15a is rotated once.

The suction pipe 136a is a pipe having one end connected to the suction port 131b of the hydraulic pump 131 and the other end connected to a midway portion of the suction pipe 136b.
The suction pipe 136 b is a pipe whose one end is connected to a suction port 71 b of a hydraulic pump 71 described later and the other end is disposed inside the hydraulic oil tank 46.

In the case of this embodiment, the operation switching valve unit 132 is an assembly of the operation switching valves 201, 202, 203, 204, 205, 206, and 207 having substantially the same configuration as the operation switching valve 32, and each is a discharge plate. The operation of the cylinder 13, the bucket cylinder 20, the arm cylinder 21, the swing cylinder 25, the turning motor 62, the left traveling motor 63, and the right traveling motor 64 is switched.
Adjustment of the sliding amount of the spool provided in each of the operation switching valves 201, 202, 203, 204, 205, 206, and 207 is performed by an operator using an operation lever (not shown) provided in the cabin 4. This is done by operating.

  The feed pipe 133 is a pipe having one end connected to the discharge port 131a of the hydraulic pump 131 and the other end branched to be connected to the operation switching valves 201, 202, 203, 204, 205, 206, and 207, respectively.

  As described above, one end of the return pipe 45 is connected to the operation switching valve unit 132 (more precisely, the operation switching valves 201, 202, 203, 204, 205, 206, and 207), and the other end is connected to the hydraulic oil tank 46. It is piping arranged inside.

  The hydraulic fluid pumped from the hydraulic pump 131 is supplied to the operation switching valves 201, 202, 203, 204, 205, 206, and 207 constituting the operation switching valve unit 132 through the feed pipe 133, respectively.

  Below, the relationship between the state of the operation switching valve 201 and the operation of the earth discharge plate cylinder 13 will be described.

When the operation switching valve 201 is in the “neutral state”, the feed piping 133 and the return piping 45 are communicated with each other inside the operation switching valve 201, and the ends of the piping 134a and the piping 134b on the operation switching valve 201 side are closed.
For this reason, the hydraulic pump 131 sucks the hydraulic oil from the hydraulic oil tank 46 through the intake pipe 136b and the intake pipe 136a, and the hydraulic oil to be pressure-fed is returned to the hydraulic oil tank 46 through the feed pipe 133, the operation switching valve 201, and the return pipe 45. . Further, the hydraulic oil filled in the bottom chamber and the rod chamber of the earth discharging plate cylinder 13 is confined.
As a result, the cylinder rod of the soil discharge plate cylinder 13 is fixed to the cylinder with a predetermined protrusion amount, and the soil discharge plate cylinder 13 is held at a predetermined length.

When the operation switching valve 201 is in the “cylinder extended state”, the feed piping 133 and the piping 134 a are communicated with each other and the piping 134 b and the return piping 45 are communicated inside the operation switching valve 201.
For this reason, the hydraulic pump 131 sucks the hydraulic oil from the hydraulic oil tank 46 through the suction pipe 136b and the suction pipe 136a, and the hydraulic oil to be pressure-fed passes through the feed pipe 133, the operation switching valve 201, and the pipe 134a, so To be supplied. Further, the hydraulic oil filled in the rod chamber of the earth discharge plate cylinder 13 is returned to the hydraulic oil tank 46 through the pipe 134b, the operation switching valve 201, and the return pipe 45.
As a result, the cylinder rod of the earth discharging plate cylinder 13 protrudes from the cylinder, and the earth discharging plate cylinder 13 extends.

When the operation switching valve 201 is in the “cylinder contraction state”, the feed piping 133 and the piping 134 b are communicated with each other and the piping 134 a and the return piping 45 are communicated inside the operation switching valve 201.
Therefore, the hydraulic pump 131 sucks the hydraulic oil from the hydraulic oil tank 46 through the suction pipe 136b and the suction pipe 136a, and the hydraulic oil to be pressure-fed passes through the feed pipe 133, the operation switching valve 201, and the pipe 134b, and the rod chamber of the soil discharge cylinder 13. To be supplied. Further, the hydraulic oil filled in the bottom chamber of the earth discharge plate cylinder 13 is returned to the hydraulic oil tank 46 through the pipe 134 a, the operation switching valve 201, and the return pipe 45.
As a result, the cylinder rod of the earth discharging plate cylinder 13 is immersed in the cylinder, and the earth discharging plate cylinder 13 contracts.

  The relationship between the state of the operation switching valve 202 and the operation of the bucket cylinder 20, the relationship between the state of the operation switching valve 203 and the operation of the arm cylinder 21, and the relationship between the operation switching valve 207 and the swing cylinder 25 are described above. The relationship between the state 201 and the operation of the earth discharging plate cylinder 13 is substantially the same.

  Hereinafter, the relationship between the state of the operation switching valve 204 and the operation of the turning motor 62 will be described.

When the operation switching valve 204 is in the “neutral state”, the feed piping 133 and the return piping 45 are communicated with each other inside the operation switching valve 204, and the ends of the piping 135a and the piping 135b on the operation switching valve 204 side are closed.
Therefore, the hydraulic pump 131 sucks from the hydraulic oil tank 46 through the suction pipe 136b and the suction pipe 136a, and the hydraulic oil to be pressure-fed is returned to the hydraulic oil tank 46 through the feed pipe 133, the operation switching valve 204, and the return pipe 45. . Further, the hydraulic oil filled in the turning motor 62 is confined.
As a result, the rotation shaft of the turning motor 62 is fixed, and the turning frame 3 is held at a predetermined turning angle with respect to the crawler type traveling device 2.

When the operation switching valve 204 is in the “left-turning state”, the feed piping 133 and the piping 135a communicate with each other and the piping 135b and the return piping 45 communicate with each other inside the operation switching valve 204.
Therefore, the hydraulic pump 131 sucks from the hydraulic oil tank 46 through the suction pipe 136b and the suction pipe 136a, and the hydraulic oil to be pressure-fed is supplied from the port 62a to the turning motor 62 through the feed pipe 133, the operation switching valve 204, and the pipe 135a. Is done. The hydraulic oil discharged from the port 62b to the outside of the turning motor 62 is returned to the hydraulic oil tank 46 through the pipe 135b, the operation switching valve 204, and the return pipe 45.
As a result, the turning motor 62 turns the turning frame 3 to the left with respect to the crawler type traveling device 2 (rotates counterclockwise in plan view).

When the operation switching valve 204 is in the “right turn state”, the feed piping 133 and the piping 135 b are communicated with each other and the piping 135 a and the return piping 45 are communicated inside the operation switching valve 204.
Therefore, the hydraulic pump 131 sucks in the hydraulic oil tank 46 through the suction pipe 136b and the suction pipe 136a, and the hydraulic oil to be pressure-fed is supplied to the turning motor 62 from the port 62b through the feed pipe 133, the operation switching valve 204, and the pipe 135b. Is done. Further, the hydraulic oil discharged from the port 62a to the outside of the turning motor 62 is returned to the hydraulic oil tank 46 through the pipe 135a, the operation switching valve 204, and the return pipe 45.
As a result, the turning motor 62 turns the turning frame 3 to the right with respect to the crawler type traveling device 2 (rotates clockwise in plan view).

  The relationship between the state of the operation switching valve 205 and the operation of the left traveling motor 63, and the relationship between the state of the operation switching valve 206 and the operation of the right traveling motor 64 are the same as the state of the operation switching valve 204 and the operation of the turning motor 62. The relationship is almost the same.

Hereinafter, the configuration of the hydraulic pressure adjustment mechanism 137 will be described with reference to FIGS. 2 and 4.
The hydraulic pressure adjusting mechanism 137 of this embodiment includes a hydraulic pressure adjusting valve 138, a pipe 139, a pilot pipe 140, a pilot pipe 141, an adjustment cylinder 142, a pipe 143, a return pipe 44a, and the like. The configuration and operation of each part are basically the same as those of the hydraulic pressure adjustment mechanism 37.
The hydraulic adjustment mechanism 137 of the present embodiment is different from the hydraulic adjustment mechanism 37 in that the hydraulic adjustment mechanism 137 is an operation switching that is an aggregate of a total of seven operation switching valves 201, 202, 203, 204, 205, 206, and 207. It corresponds to the valve unit 132 with one hydraulic pressure regulating valve 138.
More specifically, the pressure of the pilot pipe 141 is the pressure on the oil supply port side of the earth discharge plate cylinder 13, bucket cylinder 20, arm cylinder 21, swing cylinder 25, swing motor 62, left travel motor 63, and right travel motor 64. Of these, it is almost the same as the one with the highest pressure.
Accordingly, the hydraulic adjustment mechanism 137 includes the pressure on the discharge port 131a side of the hydraulic pump 131 with the operation switching valve unit 132 interposed therebetween, the earth discharge plate cylinder 13, the bucket cylinder 20, the arm cylinder 21, the swing cylinder 25, the swing motor 62, The difference between the pressure on the oil supply port side of the left traveling motor 63 and the right traveling motor 64 and the highest pressure is adjusted to a predetermined value.

Below, the discharge amount suppression mechanism 70 is demonstrated using FIG. 2, FIG.
The discharge amount suppression mechanism 70 greatly contributes to the hydraulic pump driven by the engine 15 when the load of the engine 15 as a driving source becomes a predetermined value or more (in the case of this embodiment, in particular, in the present embodiment). The discharge amount of the hydraulic pump 31 and the hydraulic pump 131) is suppressed.

  The discharge amount suppression mechanism 70 of the present embodiment mainly includes a hydraulic pump 71, a pressure adjustment valve 72, a pipe 73, a pipe 74, a pilot pipe 75, a control device 76, a wiring 78, and the like.

Below, the structure of the discharge amount suppression mechanism 70 is demonstrated using FIG. 2, FIG.
The hydraulic pump 71 is driven by the engine 15 as a drive source, and pumps hydraulic oil.
The hydraulic pump 71 is provided with a discharge port 71a that is an opening for discharging hydraulic oil and a suction port 71b that is an opening for sucking hydraulic oil. One end of a suction pipe 136b is connected to the suction port 71b.

The pressure adjustment valve 72 is a solenoid-type electromagnetic proportional valve that controls the hydraulic pressure of the pipe 75 based on a signal from a control device 76 described later.
The pressure regulating valve 72 has two ports 72a and 72b, and the spool provided inside is slid by the command signal of the control device 76 to change the flow area of the hydraulic oil passing through the pressure regulating valve 72. Then, the hydraulic pressure of the pipe 75 is adjusted.
In the pressure regulating valve 72, the spool is closed so that the hydraulic pressure is not applied to the pipe 75 at the normal time (when there is no signal from the control device 76 described later).

The pipe 73 is a pipe having one end connected to the discharge port 71 a of the hydraulic pump 71 and the other end connected to the operation valve 80.
The pipe 74 is a pipe that connects the middle part of the pipe 73 and the port 72 a of the pressure regulating valve 72. 29 is a relief valve for setting the hydraulic pressure.

  One end of the pilot pipe 75 is connected to the port 72b of the pressure adjustment valve 72, branches in the middle, and the other ends of the pilot pipe 75 out of the spool ends of the hydraulic adjustment valve 38 and the hydraulic adjustment valve 138, respectively. The force that pushes the spool with the pressure of 75 is a pipe connected to the end of the spool that pushes the spool in the direction of “state A” in FIG.

The control device 76 outputs a signal to the pressure regulating valve 72 based on the load of the engine 15, and more specifically, a configuration in which a CPU, a ROM, a RAM, and the like are connected by a bus may be used. Alternatively, it may be configured by a one-chip LSI or the like. Alternatively, it may be a sensor that outputs only when an overload is detected.
Further, the control device 76 can be omitted by providing the other control device for controlling the other components of the backhoe 1 with the function of the control device 76.

  The wiring 78 is a wiring that connects the control device 76 and the pressure regulating valve 72, more precisely, a solenoid that slides the spool of the pressure regulating valve 72.

The operation of the discharge amount suppression mechanism 70 will be described.
In this embodiment, a position sensor that detects the rack position of the engine 15 and an engine speed sensor that detects the speed of the engine 15 are used as the engine load detecting means.
The control device 76 calculates the load factor based on the rotational speed of the engine 15 and the rack position detected by the engine load detecting means. When the rack position of the engine 15 is equal to or greater than the limit rack position, it is determined that the engine 15 is overloaded and a signal is output to the pressure adjustment valve 72.

As a result, as shown in FIG. 2, the hydraulic pump 71 sucks in from the hydraulic oil tank 46 through the intake pipe 136b, and the hydraulic oil to be pressure-fed is hydraulically adjusted through the pipe 73, the pipe 74, the pressure adjustment valve 72, and the pilot pipe 75. The spool 38 reaches one end of the spool operation portion of the valve 38 and the hydraulic pressure adjusting valve 138, and both of the spools are pushed in the direction of “state A” in (a), and the hydraulic oil discharge amounts of the hydraulic pump 31 and the hydraulic pump 131 are as follows. Is suppressed (the discharge amount is reduced).
When the hydraulic oil discharge amount of the hydraulic pump 31 and the hydraulic pump 131 is suppressed, the load on the engine 15 is reduced.

The hydraulic circuit 100 can be applied not only to the regenerative hydraulic circuit of the boom cylinder 22 but also to the regenerative hydraulic circuit of the arm cylinder 21 and / or the swing motor 62.
That is, as shown in FIG. 5, similarly to the hydraulic circuit 100 that drives the boom cylinder 22, an arm cylinder driving hydraulic circuit and a swing motor driving hydraulic circuit are configured. The arm cylinder drive hydraulic circuit is configured to be drivable by connecting the drive shaft of the hydraulic pump 231 to the rotating shaft 15a of the engine 15, and the hydraulic oil can be pumped to the single rod type arm cylinder 21 by the operation of the hydraulic pump 231. It is said. Between the arm cylinder 21 and the hydraulic pump 231, an operation switching valve 203 for switching the expansion / contraction operation of the arm cylinder 22 is disposed. A hydraulic adjustment mechanism 237 is provided for adjusting the difference between the pressure on the discharge port side of the hydraulic pump 231 and the pressure on the oil supply port side of the operation switching valve 203 to the arm cylinder 21 to a predetermined value. Further, between the arm cylinder 21 and the operation switching valve 203, a communication mechanism 256 that connects a lower one of the bottom chamber and the rod chamber of the arm cylinder 21 and a drain pipe (oil discharge pipe) 56. Is arranged.

  A regenerative pipe 236 is provided to supply hydraulic oil returned to the operation switching valve 203 from the oil discharge port of the arm cylinder 21 to the hydraulic pump 231. Further, a check valve 249 is provided between the regenerative pipe 236 and the suction pipe 50 communicating with the hydraulic oil tank 46 so as to be able to supply a shortage of hydraulic oil.

  Further, the drive hydraulic circuit of the swing motor 62 can be configured in the same manner as the drive hydraulic circuit of the arm cylinder 21. In other words, the drive shaft of the hydraulic pump 331 is connected to the rotating shaft 15a of the engine 15 so that the drive shaft can be driven, and the hydraulic oil can be pumped to the turning motor 62 formed of a hydraulic motor by the operation of the hydraulic pump 331. Between the swing motor 62 and the hydraulic pump 331, an operation switching valve 204 for switching the rotation direction of the swing motor 62 is disposed. A hydraulic adjustment mechanism 337 is provided for adjusting the difference between the pressure on the discharge port side of the hydraulic pump 331 and the pressure on the oil supply port side of the operation switching valve 204 to the swing motor 62 to a predetermined value. In addition, a communication mechanism 356 is provided between the swing motor 62 and the operation switching valve 204 to connect the lower pressure side and the drain pipe (oil discharge pipe) 56.

  A regenerative pipe 336 is provided to supply hydraulic oil returned to the operation switching valve 204 from the oil discharge port of the swing motor 62 to the hydraulic pump 331. Further, a check valve 349 is provided between the regenerative pipe 336 and the suction pipe 50 communicating with the hydraulic oil tank 46 so that a shortage of hydraulic oil can be replenished.

Therefore, when the hydraulic pump 231 of the arm cylinder driving hydraulic circuit and the hydraulic pump 331 of the swing motor driving hydraulic circuit are driven by the same engine, the driving load of the hydraulic pumps 231 and 331 is caused by the motor operation of the hydraulic pumps 231 and 331. This reduces the overall work of the engine and improves fuel economy.
That is, it is possible to recover a part or all of the hydraulic oil energy (kinetic energy and potential energy) returned from the arm cylinder 21 and the swing motor 62 as a driving force of the hydraulic pump with a simple configuration.
Further, the drive hydraulic circuit can operate the hydraulic cylinder and the hydraulic motor that are operated by the hydraulic oil pumped from the hydraulic pumps 231 and 331 at a substantially constant speed regardless of the magnitude of the load.

  Similarly to the above, the operation switching valves 203 and 204 of the drive hydraulic circuit of the arm cylinder 21 and the drive hydraulic circuit of the swing motor 62 and the excess flow discharge valves of the communication mechanisms 256 and 356 are respectively integrated into one valve case. It can be provided and can be integrally formed by stacking with other valve cases, and a compact valve case can be obtained.

The left view of the backhoe which comprises the hydraulic circuit concerning the present invention. The schematic diagram which shows the Example of the hydraulic circuit which concerns on this invention. The figure which shows the hydraulic circuit of an operation switching valve and a communication mechanism. The figure which shows the hydraulic circuit of a hydraulic adjustment mechanism. The figure which shows the hydraulic circuit which enables regeneration of the hydraulic pressure of a boom cylinder, an arm cylinder, and a turning motor.

Explanation of symbols

15 Engine (drive source)
21 Arm cylinder 22 Boom cylinder (hydraulic cylinder)
31 Hydraulic Pump 32 Operation Switching Valve 36 Regenerative Piping 37 Hydraulic Adjustment Mechanism 50 Suction Piping 66 Throttle 67 Check Valve 201/202/203/204/205/206/207 Operation Switching Valve

Claims (2)

A plurality of hydraulic actuators such as hydraulic cylinders and hydraulic motors;
A hydraulic pump driven by a drive source and pumping hydraulic oil to the hydraulic actuator;
An operation switching valve that is disposed between each of the hydraulic actuators and the hydraulic pump, and switches the operation of each of the hydraulic actuators;
Using the at least one hydraulic actuator as a hydraulic cylinder, the difference between the pressure on the discharge port side of the hydraulic pump that pumps hydraulic pressure to the hydraulic cylinder and the pressure on the oil supply port side of the hydraulic cylinder of the operation switching valve is adjusted to a predetermined value Hydraulic adjustment mechanism to
A regenerative pipe for supplying hydraulic oil returned from the oil cylinder exhaust port to the operation switching valve to the hydraulic pump;
A hydraulic apparatus comprising an operation switching valve for the hydraulic cylinder and an operation switching valve for the other hydraulic actuator. A communication mechanism that is disposed between the hydraulic cylinder and the operation switching valve, and that communicates between a lower pressure of the bottom chamber and the rod chamber of the hydraulic cylinder and a drain pipe;
2. The hydraulic apparatus according to claim 1, wherein the communication mechanism is configured integrally with an operation switching valve of the hydraulic cylinder and an operation switching valve of the other hydraulic actuator.

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