EP2479349A1

EP2479349A1 - Hydraulic control apparatus for work machine

Info

Publication number: EP2479349A1
Application number: EP12152038A
Authority: EP
Inventors: Hiroshi Tsumura
Original assignee: Hitachi Construction Machinery Co Ltd
Current assignee: Hitachi Construction Machinery Co Ltd
Priority date: 2011-01-25
Filing date: 2012-01-23
Publication date: 2012-07-25
Anticipated expiration: 2032-01-23
Also published as: JP5631762B2; JP2012154383A; EP2479349B1

Abstract

A hydraulic control apparatus for a work machine exchangeably mountable a standard front attachment (6a) and a long front attachment (6b) includes a front type detecting unit (200) for work machine. The front type detecting unit includes a primary side coupler (30) with which driving power is provided from a main body side of the work machine and a secondary side coupler (31,32) to be coupled to the primary side coupler. The secondary side coupler is disposed at the front attachment side. The hydraulic pressure circuit includes a control valve (150) and a variable relief valve (141,142) which switches a relief pressure for a driving actuator (10) of a front attachment. When the long front attachment (6b) is mounted to the work machine body, an operating state of the switching valve (130) is changed, and the variable relief valve (141,142) is switched to the low pressure side. Thus, the amount of movement of the spool in the control valve is (150) limited.

Description

Background of the Invention

The present invention relates to hydraulic control apparatuses for work machines, and more particularly to a hydraulic control apparatus for a work machine suitable for a construction machine.
Conventional work machines such as a construction machine are sometimes operated exchanging front attachments depending on the content of the work, in order to improve the operation rate of the machine. This may require an exchange operation of a standard type front attachment and a long type front attachment. The standard type front attachment is set as a standard specification corresponding to the work machine, while the long type front attachment called "long front" is longer than that of the standard type front attachment, in order to expand a working range from the center of the work machine. In an exchange operation of the standard type front attachment and the long type front attachment, a worker manually couples attaching portions confirming the safety for every exchange.
Japanese Unexamined Patent Application Publication No. 2010-1613 discloses an example of exchange operation of a boom portion and a front attachment portion in the work machines. The work machine disclosed in the Japanese Unexamined Patent Application Publication No. 2010-1613 includes detecting means at an exchange portion to detect the type of the front attachment and determines the type of the coupled front attachment based on a detection result of the detecting means.
When exchanging the front attachments of the work machine, it is necessary not only to mechanically couple the attaching portion but also change a setting of a hydraulic control circuit for a hydraulic cylinder to drive the front attachment. However, the setting of the hydraulic control circuit is manually operated. When urgent change of the front attachment at a construction site or the like is required, there is no choice but to depend on on-site workers unfamiliar to the specification change of the device. This may cause prolonged work. Neglect of the setting operation causes inappropriate values for the exchanged front attachment in the setting such as an operation range and a moving speed of the front attachment. In the worst case, the work machine makes collision with a nearby construction, and this possibly increases process of works and construction cost along with a damage of the work machine.
In the work machine disclosed in Japanese Unexamined Patent Application Publication No. 2010-1613 , use of a non-contact sensor and a limit switch in the exchange portion determines the exchanged component. This ensures an advantage of preventing the human failure. However, in the work machine disclosed in Japanese Unexamined Patent Application Publication No. 2010-1613 , a change of the front attachment automatically makes it display the centric position of the vehicle body only. The change of setting for the hydraulic control circuit is not mentioned.

Brief Summary of the Invention

The present invention has been made to solve the problems, which is not considered in the above-described conventional configuration, when exchanging the front attachment, and it is an object of the present invention is to ensure even when a worker unfamiliar to the setting of the hydraulic control circuit operates the exchanging operation of the front attachment for the work machine, the worker unfailingly change the setting for the hydraulic control circuit. Another object of the present invention is to ensure that the setting of the hydraulic control circuit, which is associated with the front attachment exchange of the work machine, is unfailingly changed within short time. In order to achieve the above-described object, according to characteristic of the present invention, a hydraulic control apparatus is for a work machine exchangeably mountable a standard front attachment and a long front attachment. The long front attachment is longer than the standard front attachment. The hydraulic control apparatus includes: a primary side coupler with which driving power is provided from a main body side of the work machine; and a secondary side coupler to be coupled to the primary side coupler. The secondary side coupler is at the front attachment side. A hydraulic pressure circuit of the work machine includes: a control valve; a variable relief valve configured to switch relief pressure of a driving actuator that drives the front attachment; and a switching valve configured to switch depending on a coupling condition between the primary side coupler and the secondary side coupler. The hydraulic pressure circuit is configured to change operational state of the switching valve so as to switch the variable relief valve to a low pressure side and to limit an amount of movement of a spool in the control valve when the long front attachment is mounted to the main body side of the work machine.
In this characteristic, the driving power from the main body side of the work machine to the primary side coupler is preferred to be electric power. The primary side coupler and the secondary side coupler are preferred to be connectors. The switching valve preferably includes an electromagnetic switching valve. Additionally, the primary side coupler preferably includes a terminal coupled to the electromagnetic switching valve and a terminal coupled to a power supply. The secondary side coupler of the standard front attachment may preferably short-circuit both of the terminals at the primary side. The secondary side coupler of the long front attachment may preferably make the both terminal at the primary side in non-conducting state.
In this characteristic, the driving power from the main body side of the work machine to the primary side coupler is preferred to be hydraulic pressure. The primary side coupler and the secondary side coupler are preferred to be hydraulic couplers. The switching valve preferably includes a hydraulic switching valve. Additionally, the primary side coupler preferably includes a coupler coupled to the hydraulic pump, a coupler coupled to a hydraulic tank for oil discharge, and a coupler coupled to the switching valve. The secondary side coupler of the standard front attachment is preferably configured to supply pressure from the hydraulic pump to the switching valve. The secondary side coupler of the long front attachment is preferably configured to couple the hydraulic tank to the switching valve.
In the present invention, the work machine includes the detecting unit to automatically determine the front attachment at the front attachment exchanging portion, while the front attachment side includes the discrimination means corresponding to the detecting unit. This reduces the coupling failure at the exchanging operation of the front attachment and ensures that the setting of the hydraulic control circuit is unfailingly changed even by a worker unfamiliar to the setting of the hydraulic control circuit. The change of the setting of the hydraulic control circuit is unfailingly operated within a short time for the front attachment exchange of the work machine.

Brief Description of Several Views of the Drawing

FIG. 1 is a side view of a work machine with a standard front attachment according to an embodiment where a long front attachment is overlaid. FIG. 2 is a exemplary circuit diagram of a hydraulic pressure circuit where a type of a front attachment is determined by electrical signal. FIG. 3 is a partial perspective view of a detail of A part shown in FIG. 1. FIGS. 4A and FIG. 4B are hydraulic circuit diagrams at front attachment coupling portions where the type of the front attachment is determined by hydraulic pressure: FIG. 4A shows a case of the standard front attachment; and FIG. 4B shows a case of the long front attachment. FIG.5 is a circuit diagram of a hydraulic pressure circuit illustrating a detail of a control valve shown in FIGS. 4A and 4B where the type of the front attachment is determined by the hydraulic pressure.

Detailed Description of the Invention

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a front view of a exemplary work machine with a standard front attachment mounted where a front attachment, which is longer than the standard front attachment (hereinafter referred to as long front attachment), is overlaid. FIG. 2 and FIG. 3 are drawings of a type detecting unit of a work machine according to the present invention. FIG. 2 is a circuit diagram of a hydraulic control circuit to determine the type of the front attachment using the electrical coupling. FIG.3 is a schematic perspective view of the electrical connecting portion to determine the front attachment with the electrical coupling.
The work machine is, for example, a hydraulic shovel for excavation. This work machine has the maximum excavation radius of approximately 11 m with the standard front attachment mounted. In the work machine thus configured, changing from the standard front attachment 6a to the long front attachment 6b, which is for river improvement or the like, may increase the maximum excavation radius to 22 m.
The work machine shown in FIG. 1 is a hydraulic shovel including a lower traveling body 1 with crawler belts and an upper rotary body 2, which is rotatably mounted on the lower traveling body 1. Between the lower traveling body 1 and the upper rotary body 2, a rotation unit 3, which controls rotation of the upper rotary body 2, is disposed. The upper rotary body 2 includes a cab 4 in the front and the machine room 5 in the back. A worker boards the cab 4 and operates the work machine. The machine room 5 houses an engine and a hydraulic pump for drive and control of the work machine.
In front of the upper rotary body 2, the front attachment 6 is elevatably mounted. The front attachment 6 includes a boom 7, an arm 8 and an attachment 9. The boom 7 has a base end side coupled to the rotary body 2. The arm 8 is coupled to an opposite end side of the base end side of the boom 7. The attachment 9, such as a bucket used for the excavation or the like, is mounted on the tip of the arm 8. The boom 7, the arm 8, and the bucket respectively include a boom cylinder 10, an arm cylinder 11, and a bucket cylinder 12, which are hydraulic pressure actuators.
As described above, when changing from the standard front attachment 6a to the long front attachment 6b for river improvement or the like, a pin (not shown), which is fitted to the mounting portion disposed at the base end side of the boom 7, is pulled out. Then, the base end side of the long front attachment 6b to be mounted is positioned to the upper rotary body 2, and the pin is inserted into the mounting portion of the boom 7 and fixed to complete the exchange. This is similar to changing from the long front attachment 6b to the standard front attachment 6a.
By the way, when the front attachments 6 are exchanged, the setting of the maximum moving speed of the front attachment 6 for the long front attachment 6b needs reduction of a setting maximum moving speed compared with the standard front attachment 6a. This is because the more power is required as the moving speed of the front attachment 6 increases, and the safety is considered. This is indispensable in a use of the long front attachment 6b which has twice as large as the maximum excavation radius of the standard front attachment 6a. In order to reduce the setting maximum speed, a relief pressure of the hydraulic pressure circuit, which drives the long front attachment 6b, is reduced compared with a use of the standard front attachment 6a.
Although these settings have been manually operated by on-site workers, the automatic setting is preferred to eliminate human failure and to improve work efficiency. The work machine according to the embodiment includes a detecting unit 200, which automatically determines the type of the front attachment for the automatic setting. An embodiment of the detecting unit 200 will be described referring to FIG. 2 and FIG. 3.
In FIG. 2, an engine 120 is coupled to the main hydraulic pump 121, which drives the boom cylinder 10, and the pilot pump 122. The pilot pump 122 generates pilot pressure of a control valve 150, which controls operation of the boom cylinder 10. FIG. 2 shows only a driving circuit of the boom cylinder 10. This work machine includes a plurality of actuators such as an arm cylinder 11, a bucket cylinder 12, a rotating motor and a travelling motor along with the boom cylinder 10, and also includes a plurality of hydraulic pumps and control valves (not shown) along with the actuators.
The main hydraulic pump 121 is coupled to the control valve 150 via a main pipeline 125. The control valve 150 is coupled to the boom cylinder 10 via main pipelines 151 and 152.
On the other hand, the pilot pump 122 is coupled to the relief valves 141 and 142 via an electromagnetic switching valve 130, which is disposed between the pilot pipelines 132 and 136. The relief valves 141 and 142 are disposed in the main pipelines 151 and 152. The pilot pipeline 132, which is coupled to the pilot pump 122, includes a bifurcating portion. The bifurcating portion is coupled to a pilot valve 195 disposed at an operating lever 190. The operating lever 190 includes pressure reducing valves 191 and 192. Here, the relief valves 141 and 142 are two-tier variable relief valves which may be set at two different pressures.
Additionally, the pilot pressure generated at the pilot valve 195 is introduced to a pair of electromagnetic valve circuits 160 and 170. The electromagnetic valve circuits 160 and 170 includes electromagnetic switching valves 164 and 174, pressure reducing valves 163 and 173, and shuttle valves 162 and 172, though which the pilot pressure passes and are introduced to a pilot portion of the control valve 150.
As a characteristic configuration of the present invention, three electromagnetic switching valves 130, 164, and 174 each have a solenoid having discrimination of energization/non-energization depending on the type of the front attachment 6 of the work machine. Specifically, as shown in FIG. 3, at a portion where the base portion of the front attachment 6 is to be mounted and at the work machine side, a power feeding cable 50 is disposed to feed power to an illuminating light 51 and is fixed to the boom 7 with a fixture 44.
As shown in FIG. 2, the power feeding cable 50 includes a power feeding line 40 for solenoids of the electromagnetic switching valves 130, 134, and 174 along with a 24V power supply line 23 and a working light line 24. The power feeding cable 50, which includes three lines of the 24V power supply line 23, the working light line 24, and the solenoid power feeding line 40, are connectable with a primary side connector 30 disposed at the distal end.
The secondary side connectors, which can be coupled to the primary side connector 30, are disposed at respective base portions of exchangeable front attachments 6a and 6b. The secondary side connectors include a connector 31 and a connector 32 which have internal connections which are different from one another. In the connector 31 for the standard front attachment, the terminal 34a, which is to be coupled to the 24V power supply line 23, and the terminal 35a, which is to be coupled to the solenoid power feeding line 40, are short-circuited. This couples the solenoid power feeding line 40 to the 24V power supply line 23 when the connector 31 is coupled to the primary side connector 30. The working light line 24 is to be coupled to the front attachment side. At the front attachment side, a working light line 33 is disposed with an illuminating light 51 mounted at the distal end of the working light line 33. The working light line 33 supplies the 24V power from the battery 25 to solenoids of the electromagnetic switching valves 130, 164, and 174.
In contrast, when mounting the long front attachment 6b to the work machine, the working light line 33 of the connector 32 for the long front attachment is coupled to the working light line 24 at the primary side. Since the terminal 34b, which corresponds to the 24V power supply line 23, and the terminal 35b, which corresponds to the solenoid power feeding line 40, are not wired, the power is not fed to the solenoids of the electromagnetic switching valves 130, 164, and 174.
In the work machine thus configured, when, for example, the long front attachment 6b is selected, and the connector 32 for the long front attachment is coupled to the connector 30 at the primary side, only the working light line 24 and the working light line 33 are coupled to one another. As a result, the solenoid of the electromagnetic switching valve 130 is not energized, thus the setting pressure of the relief valves 141 and 142 are set at the lower side of setting pressures. The solenoids of the electromagnetic switching valves 164 and 174 are also not energized. Thus, the pilot pressure generated at the pilot valve 195 passes through the pressure reducing valves 163 and 173 so as to reduce the pressure. The pressure supplied to the pilot portion of the control valve 150 is reduced. As a result, a movement amount of the spool in the control valve 150 decreases. Then, flow of the pressure oil supplied to the boom cylinder 10 decreases to reduce the moving speed of the boom 7b.
On the other hand, when the standard front attachment 6a is selected, the solenoid of the electromagnetic switching valve 130 is energized. As a result, the setting pressure of the relief valves 141 and 142 are set at higher pressure than the pressure in the use of the long front attachment 6b. The solenoids of the electromagnetic switching valves 164 and 174 are also energized. Thus, the pilot pressure generated at the pilot valve 195 is directly supplied to the pilot portion of the control valve 150 without passing through the pressure reducing valves 163 and 173. As a result, the flow supplied to the boom cylinder 10 via the control valve 150 is not specifically reduced.
Simply connecting the terminals (connector) 31 and 32 disposed at the front attachment 6 side and the terminal (connector) 30 disposed at the work machine side enable to automatically discriminate between the long front attachment 6b and the standard front attachment 6a. This provides the controller of the work machine with precise information on the front attachment. An appropriate specification for the exchanged front attachment 6 can automatically be set. As a result, when using the long front attachment 6b, excessive moving speed of the front attachment and excessive pressure load can be prevented.
Another embodiment of the present invention will be described referring to FIGS. 4A and 4B and FIG. 5. In the embodiment described above, the electrical signal, that is, whether the solenoids of the electromagnetic switching valves 130, 164, and 174 are energized or not, controls the flow of the pressure oil supplied from the control valve 150 to the arm cylinder 110. According to this embodiment, the hydraulic signal controls the flow of the pressure oil supplied to the arm cylinder 110. FIGs. 4A and 4B are hydraulic circuit diagrams for illustrating the hydraulic pipe coupling portion disposed adjacent to the front attachment mounting portion. FIG. 5 is a hydraulic pressure circuit diagram where the detecting unit 200 shown in FIGs. 4A and 4B are used to determine the type of the front attachment by the hydraulic pressure. FIG. 5 corresponds to FIG. 2.
Adjacent to the front attachment mounting portion of the work machine, a hydraulic pipe 85, a hydraulic pipe 86, and an oil discharging pipe 84 are disposed. The hydraulic pipe 85 is coupled to the pilot pump 123. The hydraulic pipe 86 is coupled to pilot operated switching valves 130b, 164b, and 174b (indicated as B in the drawing) . The oil discharging pipe 84 discharges oil to an oil tank 185. The couplings 81 to 83 of different specifications are mounted at respective distal ends of the pipes 84 to 86.
In contrast, adjacent to the mounting end of the front attachment 6, a front attachment mounting unit 60 or 70 is fixed. The front attachment mounting unit 60 includes three couplings 61 to 63 at the end, which are different from each other and can be respectively coupled to the couplings 81 to 83 at the work machine side. The front attachment mounting unit 70 includes three couplings 71 to 73 at the end, which are different from each other and can be respectively coupled to the couplings 81 to 83 at the work machine side. Here, when the standard front attachment 6a is used, the couplings 61 to 63 are coupled to the couplings 81 to 83 at the work machine side. The couplings 61 to 63 are disposed at the standard front attachment mounting unit 60 of the standard front attachment 6a side. Then, since the passage to the oil tank 185 is cut off, the pilot pump 123 is communicated with the pilot operated switching valves 130b, 164b, and 174b.
On the other hand, assuming that the long front attachment 6b is used when the couplings 71 to 73 at the front attachment mounting unit 70 in the long front attachment 6b side are coupled to the couplings 81 to 83 at the work machine side, the passage to the pilot pump 123 is cut off, and the oil tank 185 is communicated with the pilot operated switching valves 130b, 164b, and 174b.
In the front attachment mounting units 60 and 70 thus configured, when the standard front attachment 6a is selected, the pilot pump 123 supplies hydraulic pressure to the pilot operated switching valve 130b shown in FIG. 5, thus switching the pilot operated switching valve 130b to set the relief valves 141 and 142 at the high pressure side. The pilot operated switching valves 164b and 174b are also switched. Thus, the flow supplied to the boom cylinder 10 is not specifically limited. On the other hand, when the long front attachment 6b is selected, the relief valves 141 and 142 are set at the low pressure side and limit the moving speed of the boom 7b, similarly to the embodiment as shown in FIG. 2. The mounting unit 60 includes the couplings 61 to 63 of different specifications. The mounting unit 70 includes the couplings 71 to 73 of different specifications. Simply selecting each coupling that can be coupled to each of couplings 81 to 83 at the work machine side can complete the coupling operation. As a result, this provides the controller with the discrimination information between the long front attachment and the standard front attachment without failure, and automatically set an appropriate specification to the exchanged front attachment.

Claims

A hydraulic control apparatus for a work machine exchangeably mountable a standard front attachment and a long front attachment, the long front attachment being longer than the standard front attachment, the hydraulic control apparatus comprising:
a primary side coupler with which driving power is provided from a main body side of the work machine; and

a secondary side coupler to be coupled to the primary side coupler, the secondary side coupler being at the front attachment side, wherein

a hydraulic pressure circuit of the work machine including:
a control valve;

a variable relief valve configured to switch relief pressure of a driving actuator that drives the front attachment; and

a switching valve configured to switch depending on a coupling condition between the primary side coupler and the secondary side coupler, wherein

the hydraulic pressure circuit is configured to change operational state of the switching valve so as to switch the variable relief valve to a lowpressure side and to limit an amount of movement of a spool in the control valve when the long front attachment is mounted to the main body side of the work machine.
The hydraulic control apparatus for the work machine according to claim 1, wherein
the driving power from the main body side of the work machine to the primary side coupler is electric power,
the primary side coupler and the secondary side coupler are connectors, and
the switching valve includes an electromagnetic switching valve.
The hydraulic control apparatus for the work machine according to claim 2, wherein
the primary side coupler includes a terminal coupled to the electromagnetic switching valve and a terminal coupled to a power supply,
the secondary side coupler of the standard front attachment short-circuits both of the terminals at the primary side, and
the secondary side coupler of the long front attachment makes the both terminal at the primary side in non-conducting state.
The hydraulic control apparatus for the work machine according to claim 1, wherein
the driving power from the main body side of the work machine to the primary side coupler is hydraulic pressure,
the primary side coupler and the secondary side coupler are hydraulic couplers, and
the switching valve includes a hydraulic switching valve.
The hydraulic control apparatus for the work machine according to claim 4, wherein
the primary side coupler includes a coupler coupled to a hydraulic pump, a coupler coupled to a hydraulic tank for oil discharge, and a coupler coupled to the switching valve,
the secondary side coupler of the standard front attachment is configured to supply pressure from the hydraulic pump to the switching valve, and
the secondary side coupler of the long front attachment is configured to couple the hydraulic tank to the switching valve.