JPH11181819A - Hydraulic retaining device for coupler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the production cost and improve the durability by connecting a pump line receiving hydraulic oil from a main pump to an actuator through an opening/closing means and a fixed side hydraulic oil supply line and connecting a relief valve in the supply line and further connecting a pilot line supplying a pilot pressure to an hydraulic instrument to the supply line through a check valve. SOLUTION: A pump line LP for a coupler is arranged to diverge from the main pump line LMP of a main pump 2, and the pump line LP and a tank line Lγ connected to the oil tank 5 are connected to the T-port and the P-port of the primary side of a directional changeover valve 6. The secondary side A port and B port are connected to a fixed side hydraulic oil supply line LH and an unfixed side hydraulic oil supply line LR. On the other hand, a pilot check valve 7 is interposed in the supply line LH and a relief valve 8 is connected between the pilot check valve 7 and the fixed port 1a of the coupler opening/ closing cylinder 1. And hence, the production coat can be reduced and the durability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic pressure holding device for a coupler mounted on a working machine such as a hydraulic shovel so that a bucket or other attachment can be easily attached to and detached from an end of an arm.

[0002]

2. Description of the Related Art In a hydraulic excavator, various operations can be performed by one hydraulic excavator by exchanging attachments such as a bucket, a hydraulic breaker, and a crusher. In order to easily and quickly replace such an attachment, for example, Japanese Unexamined Patent Publication No. Hei 6-3227
No. 88 discloses a coupler 20 as shown in FIG.

[0003] The coupler 20 includes two connecting members 22 and 23 pivotally supported by a fulcrum pin 21.
At each end of 23, U-shaped receiving portions 24 and 25 are provided, which face in mutually opposite directions. Connecting member 22
Reference numeral 23 denotes an arm 28 on the hydraulic excavator body side and a front link 30 driven by a bucket swing cylinder 29 by pins 26 and 27 provided at an intermediate portion between the fulcrum pin 21 and each of the receiving portions 24 and 25. Is pivotally attached to each tip.

[0004] A coupler opening / closing cylinder 31 is provided between the connecting members 22 and 23, and the expansion and contraction of the cylinder 31 causes the connecting members 22 and 23 to open and close about the fulcrum pin 21.

Therefore, with the connecting members 22 and 23 closed, the receiving portions 24 and 25 are inserted between the mounting pins 33 and 34 of the attachment 32 such as a bucket, and then the coupler opening / closing cylinder 31 is extended to connect the two. Members 22 and 23
To open the receiving portions 24 and 25 and the mounting pins 33.
Attachment 32 is attached to coupler 20 by pressing against 34.

The above publication further describes a hydraulic pressure holding device for driving the coupler opening / closing cylinder 31 as described above. In the apparatus, as shown in FIG. 3, a pump line 43 branched from a discharge pipe 42 of a hydraulic pump 41 and a tank line 45 connected to an oil tank 44 are connected to a direction switching valve 46 composed of an electromagnetic valve. The direction switching valve 46 is connected to a fixed-side pressure oil supply line 47.
The head-end side and the rod-end side of the coupler opening / closing cylinder 31 are connected to each other via the fixed-release-side pressure oil supply line 48.

A pressure reducing valve 49 is provided in the pump line 43,
A pilot check valve 50 is interposed in the fixed-side pressure oil supply line 47, and a relief valve 51 is connected to the fixed-side pressure oil supply line 47 at a position after the pilot check valve 50.

The hydraulic pump 41 is installed on the main body side of a hydraulic shovel. The hydraulic pump 41 is connected to a main valve 52 to which a discharge pipe 42 is connected. Pressurized oil is supplied to the dynamic cylinder 29 and the like while changing the supply pressure according to the work load.

When the above-described attachment 32 is attached to the coupler 20 by operating the hydraulic holding device having the above structure,
First, the direction switching valve 46 is turned on, the cylinder rod of the coupler opening / closing cylinder 31 is retracted, and the connecting members 22 and 23 of the coupler 20 are closed. In this state,
As described above, the receiving portions 24.2 of the connecting members 22 and 23
5 is inserted between the attachment pins 33 and 34 of the attachment 32. Next, the direction switching valve 46 is turned off. As a result, the supply of pressure oil from the hydraulic pump 41 is switched to the head end side of the coupler opening / closing cylinder 31, the coupler opening / closing cylinder 31 is extended, and the receiving portions 24 and 25 abut against the mounting pins 33 and 34, respectively. Further, a pressing force corresponding to the oil supply pressure to the coupler opening / closing cylinder 31 acts as a thrust force, and the attachment 3 is attached to the coupler 20.
2 is fixedly held.

During the subsequent operation, the hydraulic pump 41 is operated by a load acting on the arm cylinder and the bucket swing cylinder 29 on the power shovel body side.
Even if the discharge pressure increases, the oil pressure supplied to the coupler opening / closing cylinder 31 is reduced by the pressure reducing valve 49 to, for example, 100 kg.
/ Cm ² is maintained at a set pressure.
1 even if the discharge pressure of
The pressure of the oil inside 1 is equal to the pilot check valve 50.
Is held by

Further, when an excessive impact force acts on the attachment 32 during the operation to generate a large peak pressure in the coupler opening / closing cylinder 31, this peak pressure is released to the tank side through the relief valve 51. The maximum value of the peak pressure is the set pressure at the relief valve 51, for example, 20
0 kg / cm ² is suppressed below, therefore, and is able to prevent damage to the coupler opening cylinder 31 be subject to such impact.

[0012]

However, in the hydraulic holding apparatus described in the above-mentioned conventional publication, when the discharge pressure of the hydraulic pump 41 rises during the operation, the pressure is not directly applied to the coupler opening / closing cylinder 31. Pressure reducing valve 49
, There is a problem that the overall manufacturing cost increases.

After the attachment 32 is once attached to the coupler 20, even if the supply pressure of oil to the coupler opening / closing cylinder 31 is about 30 kg / cm ² , the fixed holding state of the attachment 32 is sufficiently maintained. In the above, a high pressure corresponding to the set pressure of the pressure reducing valve 49 is applied to the coupler opening / closing cylinder 31 even after the attachment 32 is attached. That is, the pressure set by the pressure reducing valve 49 is a pressure (for example, 100 kg / kg) required to promptly open and close the coupler when the attachment 32 is attached.
cm ² ), and therefore, after the attachment 32 is attached, an excessive pressure always acts on the coupler opening / closing cylinder 31.
In addition, there is a problem that the durability of the oil is reduced and the amount of oil leakage increases.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has as its object to provide a hydraulic pressure holding device for a coupler which can reduce manufacturing costs, further improve durability and reduce oil loss. It is intended to be.

[0015]

According to the first aspect of the present invention, there is provided a hydraulic pressure holding device for a coupler, comprising: a connecting member attached to a tip end of an arm of a work machine; and an actuator for operating the connecting member in a direction in which the attachment is fixed. In a coupler hydraulic pressure holding device comprising: a pump line L _P to which pressure oil is supplied from a main pump 2 provided in a work machine main body.
While connected to the actuator 1 sequentially via the opening and closing means 6 and the fixed side pressure oil supply line L _H, tank line pressure oil when this line pressure inside the fixed lateral pressure oil supply line L _H exceeds the set pressure connect the relief valve 8 to the relief to L _T, and connects the pilot line L _AP that supplies the pilot pressure to the hydraulic devices in the working machine body via a check valve 9 on the fixed side pressure oil supply line L _H It is characterized by:

In the above configuration, when the attachment is mounted by engaging the coupling member of the coupler with the mounting pin of the attachment, the opening / closing means 6 is opened, so that high-pressure hydraulic oil is supplied from the main pump 2 to the actuator 1. The attachment can be mounted by promptly causing the connecting member to move in the fixing direction at this time.

By closing the opening / closing means 6 after the attachment is completed, the pressure oil supplied to the actuator 1 is sealed off from the main pump 2 and sealed therein. Attachment fixing force is maintained. In this state, when an impact force acts on the attachment during work and a large peak pressure occurs in the oil in the actuator 1 and exceeds the set pressure of the relief valve 8, oil is discharged through the relief valve 8. When an impact force is eliminated after the discharge of such oils has occurred, the pressure of the encapsulated oil will decrease rapidly, in this case, a lower pressure than the supply pressure from the main pump 2 through a pilot line L _AP Is supplied to the actuator 1, and the attachment is held in a fixed holding state with a fixing force corresponding to the pressure state.

That is, in the above description, even if the discharge pressure of the main pump 2 on the working machine main body side increases or decreases in response to a change in load during operation, the main pump 2 is attached to the actuator 1 before the operation. Only at this time, the discharge pressure of the main pump 2 is relatively low. Therefore, even if the pressure oil from the main pump 2 is directly supplied to the actuator 1 without providing the pressure reducing valve, the actuator 1 is not damaged and the attachment mounting operation can be promptly performed.

Further, the decrease of the oil pressure sealed in the actuator 1 after the closing of the opening / closing means 6 is caused not only by the impact force at the time of the work but also by a slight oil leak. after the closing means 6 is closed is reduced to an oil pressure supplied through the pilot line L _AP in a relatively short period of time, after will be within the actuator 1 is maintained at this low pressure state.

Thus, in the above, the actuator 1 can be prevented from being damaged without providing the pressure reducing valve, so that the overall manufacturing cost can be reduced. Further, after the attachment is attached, the inside of the actuator 1 can be maintained at a fixed pressure by setting the inside of the actuator 1 to a lower pressure state, so that its durability is improved and the amount of oil leakage can be reduced.

According to a second aspect of the present invention, when the actuator 1 is operated in the fixed releasing port and the fixed side connection port 1a to which the hydraulic oil is supplied when the actuator 1 operates the connecting member in the fixing direction of the attachment. And a fixed-side pressure oil supply line L _H connected to each of these connection ports 1a and 1b.
And the fixed release side pressure oil supply line L _R to the pump line L _P
While providing a three-position directional control valve having a tank line L _T and the switching換連through the neutral position P _N to block the first and second switching position P _1, P ₂ and the pump line L _P to as the opening and closing means 6 , the pilot line L _AP, is characterized in that it is connected to an auxiliary pump 3 consisting of a gear pump for supplying the pilot pressure to the hydraulic equipment in the work machine body.

[0022] In this case, when the attachment attached to the coupler, firstly, by positioning the directional control valve to the second switching position P _2, coupling necessary for positioning the connecting member of the coupler between the attaching pins of the attachment Movement in the unlocking direction of the member, and then from the first switching position P
_{By the} operation of switching to ₁ , the connecting member can be operated in the fixing direction so as to engage the connecting member with the attachment.

The directional control valve is constituted by a three-position directional control valve having the above-mentioned neutral position _PN, and the function of the opening / closing means 6 is also used. Therefore, the manufacturing cost can be further reduced.

Further, the amount of oil supplied to the actuator 1 through the pilot line L _AP is requires a slight amount of only compensate for emissions and leakage of through the relief valve 8. For this reason, even if the auxiliary pump 3 composed of a small-capacity gear pump is provided in the main body of the work machine and the pilot pressure is supplied to the hydraulic equipment, the auxiliary pump 3 supplies the hydraulic oil to the actuator 1. be able to. Therefore, there is no need to change the capacity of the auxiliary pump 3 or the like, so that the manufacturing cost can be reduced.

[0025]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram of a hydraulic pressure holding device according to the present embodiment. In FIG. 1, reference numeral 1 denotes a coupler opening / closing cylinder, and although this coupler opening / closing cylinder 1 is not shown, An actuator that is provided in the same coupler as that described above and that opens and closes a connecting member. At both ends of the cylinder tube of the coupler opening / closing cylinder 1, a fixed side to which pressure oil is supplied when the attachment is fixed to the coupler, for example, when the coupler opening / closing cylinder 1 is extended to open the connecting member. Connection port 1a,
A fixing releasing side connection port 1b to which pressure oil is supplied when operating in a fixing releasing direction, for example, in a direction in which the coupler opening / closing cylinder 1 is contracted to close the coupling member.

On the other hand, the lower part of the figure shows a main pump 2 composed of an axial radial pump and an auxiliary pump 3 composed of a gear pump provided on the working machine body side. Pressure oil is supplied from the main pump 2 to hydraulic equipment such as an arm cylinder, a boom cylinder, and a bucket cylinder (not shown) on the machine main body through the main pump line L _MP and the main valve 4, and the discharge pressure thereof is determined according to the load at the time of work. For example, it is increased or decreased in a range of 150 to 350 kg / cm ² . The auxiliary pump 3
Is for supplying pilot pressure to various control valves for controlling the device of the pressure oil to the hydraulic device, and the supply pressure is set to, for example, about 30 kg / cm ² .

The pump line L _P for the coupler is branched from the main pump line L _MP of the main pump 2,
And the line L _P, and connected to tank line L _T to the oil tank 5, are connected to the P port and the T port of the primary side in the directional control valve 6 made of an electromagnetic valve, the two in the directional control valve 6 and the following side of the a and B ports, the fixed side pressure oil supply line L _H, via the unlocking side pressure oil supply line L _R, said coupler opening cylinder 1 of the fixed-side connection ports 1a and unlocking side connection port 1b.

The directional control valve 6 has a first switching position P ₁ for connecting the A port to the P port, the B port for the T port, the B port for the P port, and the A port for the T port. In addition to the second switching position P _{2 for} communicating with each other, and further, with the B port communicating with the T port,
It is constituted by a three-position directional control valve comprising a neutral position P _N which disconnects the P port and the A port.

On the other hand, the the fixed side pressure oil supply line L _H is interposed pilot check valve 7, further relief valve part between the fixed-side connection port 1a of the pilot check valve 7 and the coupler off the cylinder 1 8 is connected, furthermore, a pilot line L _AP connected to the auxiliary pump 3 is connected via a check valve 9.

The relief valve 8 is configured to relieve the pressure oil to the fixed-side pressure oil supply line L _R when the pressure in the fixed-side pressure oil supply line L _H exceeds, for example, 200 kg / cm ² .

Next, a description will be given of an operation procedure of the hydraulic device when attaching an attachment to the coupler.

Firstly, in order to the coupling members of the coupler moving in the closing direction to be smaller than the spacing between the pair of mounting pins in the attachment positions the directional control valve 6 to the second switching position P _2. Thus, through the pressure oil pump line L unlocking side pressure oil supply line from the _P L _R from the main pump 2 is supplied to the unlocking side connection port 1b of the coupler opening and closing the cylinder 1. At this time, opening operation to allow reverse oil flow is generated in the pilot check valve 7 the pilot port is connected to the unlocking side pressure oil supply line L _R, whereby, coupler opening cylinder 1 stationary side connection port 1a communicates with the tank line L _T through a fixed lateral pressure oil supply line L _H · directional control valve 6. As a result,
Pressure oil flows into the coupler opening / closing cylinder 1 through the fixing release side connection port 1b, the piston rod 1c retreats, and the coupler opening / closing cylinder 1 contracts. Accordingly, the connecting member of the coupler operates in the closing direction, and becomes smaller than the interval between the mounting pins.

In this state, the connecting member is positioned between the mounting pins in the attachment, and then the directional control valve 6
The switch to the first switch position P ₁ from above. This allows
The fixed release side connection port 1b of the coupler opening / closing cylinder 1 is
Tank line L through the unlocking side pressure oil supply line L _R
Communicated with the _T, the pressure oil from the main pump 2, through a fixed lateral pressure oil supply line L _H from the pump line L _P, it switched to a state that is supplied to the fixed-side connection port 1a of the coupler opening and closing the cylinder 1. As a result, the piston rod 1c moves forward, and the coupler opening / closing cylinder 1 extends. Accordingly, the connecting member of the coupler operates in the opening direction and engages with the attachment pin of the attachment. Furthermore, after the operation in the opening direction is blocked by these mounting pins, the pushing force in the opening direction against the connecting member acts as a thrust force,
The attachment is fixedly held by the coupler.

When the attachment is attached as described above, the hydraulic equipment on the working machine body side is stopped, or
If it is necessary to attach the attachment, the above-described operation is performed while causing the arm to swing. However, even in this case, the discharge pressure is increased or decreased according to the work load because the arm is almost in a no-load state as compared with the operation. The supply pressure of the pressurized oil from the main pump 2 is set to 150 near the lower limit of the variable range.
It is about kg / cm ² . Therefore, even if this pressure oil is supplied directly to the coupler opening / closing cylinder 1 without reducing the pressure, the cylinder 1 will not be damaged, and 100 kg
Since the high pressure exceeds / cm ² , the above-described opening and closing operation of the coupler occurs quickly, and the attachment can be mounted in a short time.

[0036] When the mounting of the attachment in the above operation is completed, by performing an operation for stopping the passing heat transfer to the solenoid of the directional control valve 6, to position the directional control valve 6 to the the neutral position P _N. As a result, the pump line L _P
And the fixed side pressure oil supply line L _H is isolated in the direction changeover valve within 6, switching switched to a state where the fixed side pressure oil supply line L _H and coupler-off cylinder 1 is sealed. The fixing force to the attachment is maintained according to the sealing pressure.

In this way, the attachment is fixed to the coupler, and thereafter, each hydraulic device on the working machine main body side is operated to perform required work. When an impact force acts on the attachment during the operation and a large peak pressure is generated in the oil in the coupler opening / closing cylinder 1 and exceeds the set pressure of the relief valve 8, the oil is discharged through the relief valve 8, so that the coupler is opened. The pressure inside the opening / closing cylinder 1 is suppressed to the set pressure or less, and therefore, damage to the coupler opening / closing cylinder 1 due to such an impact is also prevented.

After the oil is discharged at the time of the above-described impact, the oil filling pressure in the coupler opening / closing cylinder 1 decreases. When the pressure is lower than the supply pressure from the auxiliary pump 3 through a check valve 9, the pressure oil from the auxiliary pump 3 is of the coupler off the cylinder 1 via a pilot line L _AP · fixed side pressure oil supply line L _H It is supplied to the fixed connection port 1a. As a result, the pressure in the coupler opening / closing cylinder 1 becomes the supply pressure of the auxiliary pump 3, for example, 3
The attachment is held at 0 kg / cm ² , and the attachment is held in a fixed holding state with a fixing force corresponding thereto.

[0039] Incidentally, the decrease of the oil pressure sealed in the coupler opening cylinder 1 at after positioning the directional control valve 6 to the neutral position P _N, not only due to impact during work described above, It also occurs with a slight oil leak. Therefore, after the state of enclosing the coupler opening cylinder 1 is decreased in a relatively short time to a pressure supplied through the pilot line L _AP, it will be held at this pressure. For this reason, only the high pressure oil is supplied from the main pump 2 to the coupler opening / closing cylinder 1 at the time of the opening / closing operation of the coupler. The durability is improved and the amount of oil leakage is reduced.

As described above, in this embodiment, the pressure oil from the main pump 2 is supplied to the coupler opening / closing cylinder 1 only when the attachment is mounted while the operation on the working machine body is stopped. The opening / closing operation when the attachment is attached to the coupler is performed, and in the subsequent work involving the increase and decrease of the discharge pressure of the main pump 2, the application of the pressure oil from the main pump 2 is stopped, and the lower pressure oil is supplied from the auxiliary pump 3. Is applied, the attachment is held in a fixed holding state. Therefore, even if the pressure reducing valve is not provided in the supply line of the pressure oil from the main pump 2 to the coupler opening / closing cylinder 1, the coupler opening / closing cylinder 1 is not damaged, and the attachment mounting operation can be promptly performed. it can.

As described above, since the required operation and the attachment holding force can be performed on the coupler without providing the pressure reducing valve, the overall manufacturing cost can be reduced. Further, as described above, after the attachment is attached to the coupler, the inside of the coupler opening / closing cylinder 1 is maintained at a relatively low pressure from the auxiliary pump 3, so that its durability is improved and the amount of oil leakage is improved. Can also be reduced.

In the above-described embodiment, a gear pump provided for supplying pilot pressure to hydraulic equipment in the work machine body is used as the auxiliary pump 3.
That is, the amount of oil supplied to the coupler opening cylinder 1 through the pilot line L _AP, so requires only a small amount of only compensate for emissions and leakage of through the relief valve 8 consists of a gear pump of small capacity to the working machine main body Even if an auxiliary pump is provided to supply pilot pressure to hydraulic equipment, a configuration in which pressure oil is supplied from this auxiliary pump to the coupler opening / closing cylinder 1 can be adopted. Therefore, it is not necessary to change the capacity of the auxiliary pump or the like, so that the manufacturing cost can be reduced.

Further, in the above, the directional control valve 6 is constituted by a three-position directional control valve, which has a built-in function of shutting off the supply line from the main pump 2 to the coupler opening / closing cylinder 1, so that the whole In addition to a simpler configuration, the manufacturing cost can be further reduced.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be variously modified within the scope of the present invention. For example, in the above, the pilot check valve 7 to the fixed side pressure oil supply line L _H showing a conventional similarly interposed with the structure, it is also possible to configure the check valve 7 is also removed, whereby the overall Production cost is further reduced.

Further, in the above embodiment, 3 a directional control valve 6 consisting position directional control valve is provided, to which the pump line L _P and tank line L _T of the primary side, the fixed side pressure oil supply of the secondary side Line L _H and fixed release side pressure oil supply line L
A function as a direction switching means for switching換連with the and _R, has been the features and was also used configuration as a closing means for opening and closing the pump line L _P, the scope of the claims 1, of the primary line L _P · L _T and 2 comprising only the function as a direction switching means described above between the line L _H · L _R of the secondary side
While interposed position directional control valve, which as is can be configured is interposed off valve separate the pump line L _P.

[0046] In the above, the configuration in which the auxiliary pump 3 consisting of a gear pump supplying pressure oil to the pilot line L _AP is taken as an example, the main pump 2 in the working machine main body
Branches the discharge pipe, in the configuration that supplies the pilot pressure by providing a pressure reducing valve to be constructed by connecting to the fixed side pressure oil supply line L _H additional branches connected pilot line to the pressure reducing valve It is possible.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a hydraulic pressure holding device of a coupler according to an embodiment of the present invention.

FIG. 2 is a main part front view showing an example of a coupler mounted on an end of an arm in a hydraulic shovel as a working machine.

FIG. 3 is a circuit diagram of a conventional coupler hydraulic pressure holding device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Coupler opening / closing cylinder (actuator) 1a Fixed side connection port 1b Fixed side connection port 2 Main pump 3 Auxiliary pump 5 Oil tank 6 Direction switching valve (opening / closing means) 8 Relief valve 9 Check valve L _P pump line L _T tank line L _H Fixed pressure oil supply line L _R Releasing release pressure oil supply line L _AP pilot line P ₁ 1st switching position P ₂ 2nd switching position P _N Neutral position

Claims (2)

[Claims] 1. A hydraulic holding device for a coupler, comprising: a connecting member attached to a tip end side of an arm of a work machine main body; and an actuator (1) for operating the connecting member in a fixing direction of an attachment. with a pump (2) pump line pressure oil is supplied from (L _P) of the closing means (6) and the fixed side pressure oil supply line (L _H) and successively through the connected to the actuator (1), said fixed lateral pressure connect the oil supply line (L _H) to the relief valve to a relief of the pressure oil to the tank line (L _T) when the in-line pressure exceeds a set pressure (8), and the hydraulic equipment in the working machine body oil coupler, characterized in that a pilot line (L _AP) supplies the pilot pressure is connected via a check valve (9) to the fixed side pressure oil supply line (L _H) Holding device. 2. The fixed-side connection port (1a) to which the actuator (1) is supplied with pressure oil when the connecting member is operated in the attachment fixing direction and the pressure oil is supplied when the actuator (1) is operated in the fixing release direction. Connection port (1
b), and a fixed pressure oil supply line (L _H ) and a fixed release oil pressure supply line (L _R ) respectively connected to these connection ports (1a) (1b) are connected to a pump line (L _P ).
A tank line (L _T) and the switching換連first and second to pass
A three-position directional control valve having a switching position (P ₁ ) (P ₂ ) and a neutral position (P _N ) for shutting off the pump line (L _P ) is provided as the opening / closing means (6), while the pilot line (L) is provided. _2. The hydraulic pressure holding device for a coupler according to claim 1, wherein the auxiliary pump ( _AP ) is connected to an auxiliary pump (3) comprising a gear pump for supplying pilot pressure to hydraulic equipment in the work machine body.