JP6434112B2 - Hydraulic circuit for loader - Google Patents

Description

  The present invention relates to a hydraulic circuit of a loader to which at least a bucket, an arm, and an optional attachment are attached.

  As this type of technology, for example, there is one described in Patent Document 1. In the loader hydraulic circuit described in Patent Document 1, a boom direction switching valve, a bucket direction switching valve, and a service valve are arranged in series in an unload passage connected to a hydraulic pump in order from the upstream side. Circuit. The boom direction switching valve is a valve for operating the boom cylinder, and the bucket direction switching valve is a valve for operating the bucket cylinder. The service valve is a valve for operating the optional cylinder.

JP 2011-208693 A

  The option cylinder described in Patent Document 1 reciprocates. For example, it is assumed that a rotating attachment such as a rotary blade for mowing is attached to the loader as an option attachment. In this case, the optional actuator does not reciprocate like a cylinder but a hydraulic motor that rotates.

  In such a loader, it is assumed that the boom or bucket and the rotary blade (option attachment) for mowing are simultaneously operated. At this time, if the service valve is disposed downstream of the boom direction switching valve and the bucket direction switching valve as in the hydraulic circuit described in Patent Document 1, the boom direction switching valve is located more than the service valve.・ Pressure oil can easily flow to the bucket direction switching valve.

  With such a hydraulic circuit, a skilled operator can adjust the rotation speed of the rotary blade, but an operator unfamiliar with the operation can adjust the rotation speed of the rotary blade as desired. May not be possible.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydraulic circuit having a circuit configuration capable of improving the operability of an optional attachment attached to a loader as compared with the conventional one. .

  The present invention provides an unload passage connected to a hydraulic pump, an arm direction switching valve for supplying and discharging pressure oil from the hydraulic pump to an arm actuator, and supplying and discharging pressure oil from the hydraulic pump to a bucket actuator. A loader hydraulic circuit comprising: a bucket direction switching valve; and an option direction switching valve for supplying and discharging pressure oil from the hydraulic pump to an option actuator. Here, the option direction switching valve is disposed in the unload passage on the upstream side of the arm direction switching valve and the bucket direction switching valve. The option directional control valve is supplied with pressure oil from an option pressure oil supply passage branched from the unload passage on the upstream side of the option directional control valve. The pressure oil is supplied from the arm pressure oil supply passage branched from the unload passage between the option direction switching valve and the arm direction switching valve. The circuit is configured so that the pressure oil is supplied from the bucket pressure oil supply passage branched from the unload passage between the direction switching valve and the bucket direction switching valve.

  According to the hydraulic circuit of the present invention, since the pressure oil flows to the option direction switching valve has priority over the pressure oil flowing to the arm direction switching valve or the bucket direction switching valve, the arm direction The operation of the optional directional control valve is prioritized over the operation of the directional control valve or bucket directional control valve. Thereby, the operativity of the option attachment attached to the loader can be improved compared with the past.

1 is a hydraulic circuit diagram of a multiple direction switching valve for a loader according to an embodiment of the present invention. FIG. 2 is an enlarged view of an upper portion of the hydraulic circuit shown in FIG. 1, and regarding the optional directional control valve, the state of the stroke intermediate region of the spool is indicated by a dotted line. FIG. 3 is a hydraulic circuit diagram showing a state when a spool of an option direction switching valve has moved from an intermediate stroke area shown in FIG. 2 to a full stroke position.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(Circuit configuration of hydraulic circuit)
With reference to FIGS. 1 to 3, a hydraulic circuit 1 for a loader multiple direction switching valve according to an embodiment of the present invention will be described. The hydraulic circuit 1 is a hydraulic circuit including a plurality of directional control valves 6, 7, 8 arranged in series in an unload passage 21 connected to the hydraulic pump 2. The hydraulic circuit 1 shown in FIG. 1 can also be grasped as a multiple directional switching valve including a plurality of directional switching valves 6, 7, 8 arranged in series. In this case, reference numeral 1 denotes a multiple direction switching valve.

  Here, the loader (not shown) includes an attachment such as an arm attached to the front portion of the loader body and a bucket attached to the tip portion of the arm. In addition to these attachments, an optional attachment is attached to the loader to which the hydraulic circuit 1 of the present embodiment is applied. Examples of the optional attachment include a mowing rotary blade and a drill. In the following description, a rotary blade for mowing is attached to the loader as an optional attachment. The optional attachment is not limited to the rotary blade and drill for mowing.

  The arm (not shown) is operated by the arm cylinder 4 (arm actuator), and ascends when the pressure oil is supplied to the head side chamber 4a of the arm cylinder 4, and the pressure oil is supplied to the rod side chamber 4b. Descend. The bucket is operated by a bucket cylinder 5 (bucket actuator), and is dumped (forward-inclined direction) when pressure oil is supplied to the head side chamber 5a of the bucket cylinder 5, and the pressure oil is supplied to the rod side chamber 5b. Operates in the rake direction (backward direction). The rotary blade is operated by a hydraulic motor 3 (optional actuator), and rotates when pressure oil is supplied to the hydraulic motor 3.

  As shown in FIG. 1, the hydraulic circuit 1 of this embodiment includes an arm direction switching valve 7, a bucket direction switching valve 8, an option direction switching valve 6, a distribution valve 9, and a flow rate adjustment valve 10. It has. The hydraulic circuit 1 is a circuit connected to the hydraulic pump 2, the arm cylinder 4 for operating the arm, the bucket cylinder 5 for operating the bucket, the hydraulic motor 3 for rotating the rotary blade, and the tank 13 for returning the oil.

  Here, the option direction switching valve 6 is arranged in the unload passage 21 upstream of the arm direction switching valve 7 and the bucket direction switching valve 8. The arm direction switching valve 7 is disposed in the unload passage 21 on the upstream side of the bucket direction switching valve 8. The arm direction switching valve 7 may be arranged in the unload passage 21 on the downstream side of the bucket direction switching valve 8.

  The distribution valve 9 is disposed in the unload passage 21 on the upstream side of the option direction switching valve 6. In addition, although it is preferable to provide the distribution valve 9 as one element which comprises the hydraulic circuit of this invention, it is not an essential component.

  The unload passage 21 upstream of the option direction switching valve 6 and the distribution valve 9 and the unload passage 21 between the option direction switching valve 6 and the arm direction switching valve 7 are connected by a bypass passage 25. Has been. The flow rate adjusting valve 10 is disposed in the bypass passage 25. An unload passage 21 upstream of the option direction switching valve 6 and the distribution valve 9 and an unload passage 21 between the arm direction switching valve 7 and the bucket direction switching valve 8 are connected to the bypass passage 25. And the flow rate adjusting valve 10 may be disposed in the bypass passage 25.

  When the arm direction switching valve 7 is disposed in the unload passage 21 on the downstream side of the bucket direction switching valve 8, for example, the unload passage on the upstream side of the option direction switching valve 6 and the distribution valve 9 is used. 21 and an unload passage 21 between the option direction switching valve 6 and the bucket direction switching valve 8 are connected by a bypass passage 25, and the flow rate adjusting valve 10 is disposed in the bypass passage 25. An unload passage 21 upstream of the option direction switching valve 6 and the distribution valve 9 and an unload passage 21 between the bucket direction switching valve 8 and the arm direction switching valve 7 are connected by a bypass passage 25. The flow rate adjusting valve 10 may be disposed in the bypass passage 25. In addition, although it is preferable to provide the bypass passage 25 and the flow rate adjustment valve 10 as one element which comprises the hydraulic circuit of this invention, it is not an essential component.

<Direction switching valve for arm>
The arm direction switching valve 7 is a three-position direction switching valve that supplies and discharges the pressure oil from the hydraulic pump 2 to and from the arm cylinder 4. The arm direction switching valve 7 is supplied with pressure from a pressure oil supply passage 23 (arm pressure oil supply passage) branched from an unload passage 21 between the option direction switching valve 6 and the arm direction switching valve 7. Oil is supplied.

<Buck direction switch>
The bucket direction switching valve 8 is a three-position direction switching valve that supplies and discharges the pressure oil from the hydraulic pump 2 to the bucket cylinder 5. The bucket direction switching valve 8 is supplied with pressure from a pressure oil supply passage 24 (bucket pressure oil supply passage) branched from an unload passage 21 between the arm direction switching valve 7 and the bucket direction switching valve 8. Oil is supplied.

<Optional directional valve>
The option direction switching valve 6 is a three-position direction switching valve that supplies and discharges the hydraulic oil from the hydraulic pump 2 to and from the hydraulic motor 3. The option directional control valve 6 is supplied with pressure from a pressure oil supply passage 22 (option pressure oil supply passage) branched from the unload passage 21 upstream of the option directional control valve 6 via the distribution valve 9. Oil is supplied. When the distribution valve 9 is not provided, the pressure oil supply passage 22 (option pressure oil supply passage) is directly branched from the unload passage 21 upstream of the option direction switching valve 6.

<Distributing valve>
The distribution valve 9 is configured to change the flow distribution between the pressure oil flowing in the unload passage 21 and the pressure oil flowing in the pressure oil supply passage 22 in accordance with the load pressure of the hydraulic motor 3. It is a valve. In one chamber (position 9 c side) of the distribution valve 9, the pressure of the hydraulic oil supply passage 22 to the hydraulic motor 3 (pump pressure of the hydraulic pump 2, hydraulic pressure between the distribution valve 9 and the optional directional switching valve 6 is provided. The pressure of the tank passage 25 is input to the other chamber (position 9a side) of the distribution valve 9 when the optional directional control valve 6 is in the position 6b (neutral position) (FIG. 1). A spring 26 is disposed in the other chamber (position 9a side) of the distribution valve 9.

  As shown in FIG. 3, when the optional directional control valve 6 is in the position 6a or the position 6c (full stroke position), the other valve (position 9a side) of the distribution valve 9 is placed in the load of the hydraulic motor 3. Pressure is input. Further, as shown in FIG. 2, even when the optional directional control valve 6 is in the stroke intermediate region 6x, 6y, the load pressure of the hydraulic motor 3 remains in the other chamber (position 9a side) of the distribution valve 9. Entered.

<Flow control valve>
The flow rate adjusting valve 10 is a valve configured to allow a predetermined amount of pressure oil to flow through the bypass passage 25. The flow rate adjusting valve 10 includes a variable throttle 11 provided in the bypass passage 25 and a bypass valve 12 to which the pressure before and after the variable throttle 11 is input and the differential pressure across the variable throttle 11 is kept constant. The The pressure on the upstream side of the variable throttle 11 in the bypass passage 25 is input to one (position 12 b side) chamber of the bypass valve 12, and the variable throttle is input to the other chamber (position 12 a side) of the bypass valve 12. 11 downstream pressure is input. A spring 27 is disposed in the other chamber (position 12 a side) of the bypass valve 12.

(Hydraulic circuit operation (action / effect))
(When the optional directional control valve 6 is in the neutral position (position 6b))
The operation of the hydraulic circuit 1 will be described. First, it is assumed that the operator does not operate the hydraulic motor 3 that rotates the rotary blade, that is, does not operate the option direction switching valve 6. At this time, the option direction switching valve 6 is in a neutral position (position 6b) (see FIG. 1). In this case, the differential pressure between the hydraulic pressures acting on one (position 9c side) chamber and the other (position 9a side) chamber of the distribution valve 9 is larger than the spring force of the spring 26. Moves to position 9c. Therefore, the pressure oil from the hydraulic pump 2 flows through the unload passage 21.

(When the optional directional control valve 6 is in the stroke intermediate region 6x, 6y)
It is assumed that the operator simultaneously operates the arm cylinder 4 that moves the arm and the hydraulic motor 3 that rotates the rotary blade, that is, the arm direction switching valve 7 and the option direction switching valve 6 are simultaneously operated. It is assumed that the optional directional control valve 6 is not in the full stroke position but in the stroke intermediate region 6x (or 6y) as shown in FIG. 2 (see FIG. 2). At this time, pressure oil is supplied from the pressure oil supply passage 22 branched from the unload passage 21 upstream of the arm direction switching valve 7 to the option direction switching valve 6. The flow of pressure oil to the optional directional control valve 6 is prioritized over the flow of pressure oil. As a result, the operation of the option direction switching valve 6 has priority over the operation of the arm direction switching valve 7. Thereby, the operativity of the rotary blade attached to the loader is improved as compared with the prior art. Note that the same action and effect are obtained when the operator simultaneously operates the bucket cylinder 5 and the hydraulic motor 3 (the same applies when the optional directional switching valve 6 is at the full stroke position).

  Here, the distribution valve 9 includes the pressure in the pressure oil supply passage 22 (pump pressure of the hydraulic pump 2, hydraulic pressure between the distribution valve 9 and the optional directional switching valve 6), and the load pressure ( The differential pressure with respect to the pressure on the downstream side of the restrictor 28 of the option direction switching valve 6 is balanced at a position (any position between the positions 9a, 9b, 9c) equal to the spring force of the spring 26.

<When the load pressure of the hydraulic motor 3 increases>
The pressure in the chamber on the position 9a side of the distribution valve 9 increases, and the distribution valve 9 moves to the position 9a side. Since the distribution valve 9 moves in a direction to reduce the passage area flowing to the unload passage 21, the pressure in the pressure oil supply passage 22 (pump pressure of the hydraulic pump 2, between the distribution valve 9 and the optional directional switching valve 6). The hydraulic pressure) increases. The distribution valve 9 balances at a position where the differential pressure between the hydraulic pressures acting on one (position 9 c side) chamber and the other (position 9 a side) chamber of the distribution valve 9 becomes equal to the spring force of the spring 26.

<When the load pressure of the hydraulic motor 3 becomes low>
The pressure in the chamber on the position 9a side of the distribution valve 9 decreases, and the distribution valve 9 moves to the position 9c side. Since the distribution valve 9 moves in the direction of increasing the passage area flowing to the unload passage 21, the pressure in the pressure oil supply passage 22 (pump pressure of the hydraulic pump 2, between the distribution valve 9 and the directional switching valve 6 for options) The hydraulic pressure is reduced. The distribution valve 9 balances at a position where the differential pressure between the hydraulic pressures acting on one (position 9 c side) chamber and the other (position 9 a side) chamber of the distribution valve 9 becomes equal to the spring force of the spring 26.

  Thus, even if the load pressure of the hydraulic motor 3 fluctuates because the differential pressure before and after the throttle 28 of the optional directional control valve 6 is constantly controlled by the distributing valve 9 (load of the hydraulic motor 3). According to the pressure, a constant flow rate of pressure oil is supplied to the hydraulic motor 3 (the flow rate distribution between the pressure oil flowing in the unload passage 21 and the pressure oil flowing in the pressure oil supply passage 22 is changed).

  The throttle 28 is formed by narrowing the passage of pressure oil because the option direction switching valve 6 is in the stroke intermediate region 6x.

(When the optional directional control valve 6 is at the full stroke position (positions 6a and 6c))
Here, it is assumed that the operator sets the option direction switching valve 6 to the full stroke position (see FIG. 3). In the present embodiment, the meter-in side opening area of the optional directional control valve 6 at the full stroke position (position 6a) is not reduced. In this case, the pressure difference before and after the pressure oil passing through the option direction switching valve 6 becomes smaller than the cracking force of the spring 26 of the distribution valve 9. Therefore, the distribution valve 9 is in the position 9a, and the pressure oil does not flow to the unload passage 21 downstream of the distribution valve 9. The pressure oil from the hydraulic pump 2 flows into the directional switching valve 6 for the entire flow rate and option.

  In addition, when the meter-in side opening area of the optional directional control valve 6 at the full stroke position (position 6a) is throttled (a throttle is provided), the distribution directional valve 6 is stroked by the optional directional control valve 6. The same movement as in the intermediate zone 6x (see FIG. 2) is performed (the same applies to the full stroke position (position 6c)).

<Effect of distribution valve>
By disposing the distribution valve 9 in the hydraulic circuit 1, the pressure oil supplied from the hydraulic pump 2 corresponds to the operation amount of the option direction switching valve 6 regardless of the change of the load pressure acting on the hydraulic motor 3. While flowing to the hydraulic motor 3 at a constant flow rate, pressure oil of a predetermined flow rate or more can flow to the arm cylinder 4 or the bucket cylinder 5.

<Operation and effect of flow control valve>
In the present embodiment, the bypass circuit 25 and the flow rate adjusting valve 10 are provided in the hydraulic circuit 1. It is assumed that the operator operates the arm direction switching valve 7 and the option direction switching valve 6 simultaneously. Then, it is assumed that the load pressure acting on the arm cylinder 4 has changed. At this time, even if the load pressure acting on the arm cylinder 4 changes, the differential pressure across the variable throttle 11 provided in the bypass passage 25 is kept constant by the bypass valve 12, so that excess oil is unloaded from the unload passage 21. To return to tank 13. That is, by providing the bypass passage 25 and the flow rate adjusting valve 10 in the hydraulic circuit 1, the pressure oil supplied from the hydraulic pump 2 can be supplied to the arm direction switching valve regardless of the change in the load pressure acting on the arm cylinder 4. 7 can flow through the arm cylinder 4 at a constant flow rate corresponding to the amount of operation. It should be noted that the same actions and effects are obtained when the operator operates the bucket cylinder 5 and the hydraulic motor 3 simultaneously.

  Further, by making the throttle variable (variable throttle 11), pressure oil is supplied to the arm cylinder 4 (or bucket cylinder 5) when the arm cylinder 4 (or bucket cylinder 5) and the hydraulic motor 3 are operated simultaneously. The balance of quantity can be changed arbitrarily.

1: Hydraulic circuit (hydraulic circuit for loader)
2: Hydraulic pump 3: Hydraulic motor (optional actuator)
4: Arm cylinder (arm actuator)
5: Bucket cylinder (bucket actuator)
6: Direction switching valve for option 7: Direction switching valve for arm 8: Direction switching valve for bucket 9: Distribution valve 10: Flow rate adjusting valve 11: Variable throttle 12: Bypass valve 13: Tank 21: Unload passage 22: Pressure oil Supply passage (optional pressure oil supply passage)
23: Pressure oil supply passage (pressure oil supply passage for arm)
24: Pressure oil supply passage (pressure oil supply passage for bucket)
25: Bypass passage

Claims (1)

An unload passage connected to the hydraulic pump;
An arm direction switching valve for supplying and discharging pressure oil from the hydraulic pump to an arm actuator;
A bucket direction switching valve for supplying and discharging pressure oil from the hydraulic pump to a bucket actuator;
An optional directional control valve for supplying and discharging pressure oil from the hydraulic pump to an optional actuator,
In the loader hydraulic circuit in which the optional directional control valve is disposed upstream of the arm directional control valve and the bucket directional control valve,
The option direction switching valve is supplied with pressure oil from an option pressure oil supply passage branched from the unload passage upstream of the arm direction switching valve and the bucket direction switching valve via a distribution valve. And
The arm direction switching valve is supplied with pressure oil from the arm pressure oil supply passage branched from the unload passage between the distribution valve and the arm direction switching valve,
The bucket direction switching valve is supplied with pressure oil from a bucket pressure oil supply passage branched from the unload passage between the distribution valve and the bucket direction switching valve,
The pressure of the optional pressure oil supply passage is input to one chamber of the distribution valve,
A spring is disposed in the other chamber of the distribution valve, and when the optional directional control valve is in the neutral position, the pressure of the tank passage is input, and the optional directional control valve is in the full stroke position. When the load pressure of the optional actuator is input,
The distribution valve changes a flow rate distribution between the pressure oil flowing in the unload passage and the pressure oil flowing in the option pressure oil supply passage according to a load pressure of the option actuator. Hydraulic circuit for

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