JP2003013913A - Hydraulic control circuit and crane therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the hydraulic circuit having at least two systems of a feed pipeline supplying hydraulic oil from a hydraulic oil source to a control valve and a return pipeline returning the hydraulic oil supplied to the control valve to a tank, to effectively cool the hydraulic oil. SOLUTION: A temperature sensor 11 and an electromagnetic changeover valve 10 are installed in a pipeline 7 converging return pipelines 6A, 6B and an oil cooler 8 is interposed in one side of the downstream pipelines of the electromagnetic changeover valve 10. When a detected value of the temperature sensor 11 exceeds a specified value T0, the electromagnetic changeover valve 10 is switched over to the position B to lead the whole quantity of the return oil to the oil cooler 8. When the detected value of the temperature sensor 11 is lower than the specified value T0, the electromagnetic changeover valve 10 is switched over to the position A to lead the whole quantity of the return oil to a bypass pipeline 9 to bypass the oil cooler 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control circuit having at least two hydraulic circulation paths for supplying pressure oil from a hydraulic source to a hydraulic actuator and returning it to a tank, and a crane having the hydraulic control circuit.

[0002]

2. Description of the Related Art At least two circulation paths are provided in which pressure oil from a hydraulic pressure source is guided to a control valve via a supply pipeline and return oil from the control valve is returned to a tank via a return pipeline.
A hydraulic control circuit having a system is disclosed in, for example, Japanese Patent Laid-Open No. 10-274.
No. 211 is disclosed. In the circuit described in this publication, an oil cooler is provided in one of the return pipes to cool a part of the entire return oil, and a switching valve is provided in the other return pipe. The rest of the oil is passed or bypassed by the oil cooler. The switching valve is switched according to the return oil temperature on the upstream side of the oil cooler.

[0003]

By the way, in order to quickly start the work immediately after the engine is started, it is desirable to quickly raise the temperature of the hydraulic oil to a temperature suitable for the work. However, in the circuit described in the above publication, the return oil from one of the return pipes passes through the oil cooler regardless of the oil temperature, so that the rise of the operating oil temperature is hindered and the warm-up time becomes longer. As a result, the fuel consumption increases and the operating cost increases.

An object of the present invention is to provide a hydraulic control circuit capable of effectively controlling the temperature of pressure oil flowing through at least two circulation paths, and a crane having the hydraulic control circuit.

[0005]

An embodiment will be described with reference to the drawings. (1) The hydraulic pressure control circuit according to the invention of claim 1 includes a hydraulic pressure source 2
A first circulation path for guiding the pressure oil from A, 2B to the first hydraulic equipment 4A, 3A from the first supply pipeline 5A and returning it to the tank via the first return pipeline 6A; A hydraulic control circuit having at least a second circulation path that leads from the supply pipeline 5B to the second hydraulic equipment 4B, 3B, 30 and returns to the tank via the second return pipeline 6B. The first return pipe 6A and the second return pipe 6B join together, the oil cooler 8 that cools the return oil in the join conduit 7, and the merge conduit 7 that bypasses the oil cooler 8. A bypass pipe 9 for guiding pressure oil from the tank to the tank, an oil temperature detector 11 for detecting the oil temperature in the circulation passage, and an oil cooler 8 and a bypass pipe 9 according to the temperature detected by the oil temperature detector 11.
Distribution control means 10, 12, for controlling the distribution amount of return oil to the
The above-described object is achieved by including 13, 20, and 21. (2) According to the invention of claim 2, in the hydraulic control circuit according to claim 1, the distribution control means moves from the merging pipe line 7 to the oil cooler 8 when the temperature detected by the oil temperature detection means 11 exceeds a predetermined value T0. It has a switching valve 10 that guides the return oil and switches so that the return oil is guided from the merging pipe line 7 to the bypass pipe line 9 at a predetermined value T0 or less. (3) According to the invention of claim 3, in the hydraulic control circuit according to claim 1, the distribution control means increases the amount of return oil guided to the oil cooler 8 as the temperature detected by the oil temperature detection means 11 increases. Flow control valve 2 whose valve opening is controlled
It has 0. (4) The invention of claim 4 is the hydraulic control circuit according to any one of claims 1 to 3, wherein the first circulation path is an actuator drive path for supplying drive pressure oil to the hydraulic actuator 3A. Brake device 30
It is a brake cooling path for supplying cooling oil to the. (5) The crane according to the invention of claim 5 includes:
The above-described object is achieved by including the hydraulic control circuit according to any one of the above.

In the section of the means for solving the above-mentioned problems for explaining the structure of the present invention, the drawings of the embodiments of the invention are used for the sake of easy understanding of the present invention. It is not limited to this form.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment Hereinafter, a first embodiment of a hydraulic control circuit according to the present invention will be described with reference to FIGS. 1 and 5. 1 is a circuit diagram showing a configuration of a hydraulic control circuit according to a first embodiment of the present invention, and FIG. 4 is a side view of a crane having the hydraulic control circuit. Although the crane is equipped with a plurality of hydraulic actuators, only two of them are shown in FIG. As shown in FIG. 4, the mobile crane includes a traveling body 101, a swingable swinging body 102 mounted on the traveling body 101, and a boom 103 supported by the swinging body 102 so as to be capable of undulating. Then, the revolving structure 102
The wire rope 104 is wound up or down by driving the hoisting drum 100 mounted on the wire rope 104.
The suspended load 106 is lifted by the hook 105 connected to the. Further, by driving the hoisting drum 107, the hoisting rope 108 is hoisted or lowered, and the boom 103 is hoisted.

As shown in FIG. 1, the hydraulic control circuit includes a pair of hydraulic pumps 2A, 2B driven by the engine 1.
And a pair of hydraulic actuators 3A and 3B (for example, a hydraulic motor for driving the hoisting drum 100 and a hydraulic motor for driving the undulating drum), which are respectively driven by the pressure oil from the hydraulic pumps 2A and 2B, and the hydraulic pumps 2A and 2B. From the hydraulic actuators 3A and 3B to the hydraulic actuators 3A and 3B, respectively, and a pair of control valves 4A and 4B and hydraulic pumps 2A and 2B.
B, a pair of supply pipes 5A, 5B for guiding pressure oil to the control valves 4A, 4B, a pair of return pipes 6A, 6B for returning the return oil from the control valves 4A, 4B to the tank, and a return pipe 6A. ,
6B, a confluence pipe 7, an oil cooler 8 for cooling the return oil in the confluence pipe 7, a bypass pipe 9 for bypassing the oil cooler 8, and a return oil in the confluence pipe 7 for the oil cooler 8 Alternatively, it has an electromagnetic switching valve 10 that selectively guides it to the bypass conduit 9 and a temperature sensor 11 that detects the return oil temperature in the merging conduit 7 upstream of the electromagnetic switching valve 10.

The temperature sensor 11 is connected to the temperature switch 12, and the switch 12 is turned on when the temperature detection value by the temperature sensor 11 exceeds a predetermined value T0 set in advance. When this switch is turned on, electricity flows to the relay 13, the relay contact is closed, and the solenoid 10a of the electromagnetic switching valve 10 is excited. When the detected temperature value is equal to or lower than the predetermined value T0, the switch 12 is turned off and the solenoid of the electromagnetic switching valve 10 is demagnetized. In FIG. 1, a filter 14 is provided on the downstream side of the oil cooler 8 and the bypass pipe line 9, and relief valves 15 and 16 are attached to the filter 14 and the oil cooler 8, respectively. In addition, the supply pipelines 5A, 5B
Are provided with relief valves 17A and 17B for limiting the maximum pressure from the hydraulic pumps 2A and 2B.

The operation of the present embodiment configured as above will be described. Immediately after the engine is started, the oil temperature detection value by the temperature sensor 11 is lower than the predetermined value T0, and the temperature switch 12 is turned off. As a result, the electromagnetic switching valve 10
The solenoid 10a is excited and the solenoid operated directional control valve 10 is switched to position A. In this state, the hydraulic pumps 4A, 4A
The hydraulic oil from B is supplied to the supply pipes 5A, 5B and the control valves 4A, 4
B, the return conduits 6A and 6B, the merging conduit 7, the bypass conduit 9, and the filter 14 are returned to the tank. As a result, all return oil bypasses the oil cooler 8,
The temperature of hydraulic oil rises quickly. During work, the control valves 4A and 4B are switched from the neutral position to the work position by operating an operation lever or the like (not shown). As a result, hydraulic oil from the hydraulic pumps 2A and 2B is supplied to the actuators 3A and 3B, and the actuators 3A and 3B are driven. As a result, hoisting work of the suspended load 106 can be performed.

In this case, if the actuators 3A and 3B are driven in a state where the hydraulic oil temperature is low, the oil viscosity is high, so that the pressure loss in the circuit increases, which may adversely affect the hydraulic equipment. Therefore, it is usually necessary to perform warm-up operation and wait until the temperature of the hydraulic oil rises. In this respect, in the present embodiment, since all the return oil bypasses the oil cooler 8, the temperature of the hydraulic oil rises quickly and the warm-up operation can be completed in a short time.

When the temperature of the return oil exceeds a predetermined value T0, the temperature switch 12 is turned on. As a result, the electromagnetic switching valve 10
Is switched to the position b, and the return oil from the control valves 4A, 4B is returned to the tank via the return pipes 6A, 6B, the joining pipe 7, the oil cooler 8, and the filter 8. As a result, the entire amount of the return oil passes through the oil cooler 8, so that the working oil is cooled efficiently and the working oil temperature drops. As a result, the decrease in oil viscosity is suppressed, and the amount of leak from the hydraulic device can be reduced. Further, it is possible to prevent deterioration of the hydraulic oil, deterioration of the sealing material, and the like due to the decrease of the hydraulic oil temperature, and it is possible to reduce adverse effects on the durability of the hydraulic equipment.

As described above, in the first embodiment, the electromagnetic switching valve 10 is provided in the merging conduit 7 that joins the pair of return conduits 6A and 6B, and the electromagnetic switching valve 10 is switched according to the temperature of the return oil. The distribution amount of the return oil to the oil cooler 8 and the bypass pipe 9 was controlled so that the entire amount of the return oil was selectively guided to the oil cooler 8 or the bypass pipe 9. As a result, the temperature of the return oil can be quickly raised when the engine is started, and the rise of the oil temperature can be suppressed within the predetermined value T0. As a result, the warm-up operation time is shortened, the fuel consumption amount is saved, and the oil temperature rise is limited, so that the deterioration of the working oil and the deterioration of the seal material can be prevented.

-Second Embodiment- A second embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a circuit diagram showing the configuration of a hydraulic control circuit according to the second embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals, and the differences will be mainly described below. As shown in FIG. 2, in the second embodiment, an electromagnetic proportional valve 20 is provided instead of the electromagnetic switching valve 10, and a signal from the temperature sensor 11 is taken into the controller 21. The controller 21 has a preset relationship of control signals with respect to the oil temperature detection value. The control signal from the controller 21 distributes the return oil to the oil cooler 8 as the oil temperature increases as shown in FIG. The valve opening of the solenoid proportional valve 20 is controlled so that the amount increases. In FIG. 3, the distribution amount to the oil cooler 8 is 0 when the return oil temperature is equal to or lower than the predetermined value T0, the distribution amount gradually increases when the return oil temperature exceeds the predetermined value T0, and the oil cooler is equal to or higher than the return oil temperature T1. The amount of return oil distributed to 8 becomes 100%.

As described above, in the second embodiment, the electromagnetic proportional valve 20 is provided in the merging pipe line 7 so that the distribution amount of the return oil to the oil cooler 8 gradually increases as the temperature of the return oil increases. Therefore, the fluctuation range of the return oil temperature can be suppressed to be small, and the return oil temperature can be accurately brought close to the predetermined value T0. The deviation between the detected oil temperature value and the predetermined value T0 may be calculated, and the valve opening degree of the electromagnetic proportional valve 20 may be increased or decreased according to the deviation.

-Third Embodiment- A third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram showing the configuration of a hydraulic control circuit according to the third embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals, and the differences will be mainly described below. As shown in FIG. 4, in the third embodiment,
A cooling circuit for the wet multi-plate brake 30 is used instead of the driving circuit for the hydraulic actuator 3B.

As shown in FIG. 4, the hydraulic motor 31 is connected to the hoisting drum 100 via a planetary speed reduction mechanism 32. A plurality of inner discs 34 are engaged with the carrier shaft 33 of the planetary reduction mechanism 32 so as to be movable in the axial direction, and a plurality of outer discs 35 are engaged with the inner peripheral surface of the brake case 40 so as to be movable in the axial direction. Have been combined. The discs 34 and 35 are pressed against each other by a brake disc 36, whereby the rotation of the inner disc 34 is blocked by a frictional force and the brake is operated. Cooling oil is supplied to the brake case 40 via the supply pipe 5B and the control valve 4B, and the cooling oil is guided to the merging pipe 7 via the control valve 4B and the return pipe 6B. The cooling oil flowing in the brake case 40 cools the disks 34 to 36. The brake disc 36 is pushed by the hydraulic cylinder 37, and the hydraulic cylinder 37 is driven according to the degree of pressure reduction of the pressure reducing valve 38. The degree of pressure reduction of the pressure reducing valve 38 is adjusted by operating the brake pedal 39.

When the hydraulic pressure on the hydraulic cylinder 37 is reduced by operating the brake pedal 39, the hydraulic cylinder 37 is expanded by the spring force. As a result, the brake disc 36 is pushed, the discs 34, 35 are pressed against each other, and the brake is activated. When the brake pedal 39 is not operated, the maximum pressure acts on the hydraulic cylinder 37, and the hydraulic cylinder 37 is retracted against the spring force. As a result, the pressure contact force acting on the disks 34, 35 is removed and the brake is released.

In the third embodiment, when the temperature of the return oil is equal to or lower than the predetermined value T0, the electromagnetic switching valve 10 is operated as described above.
Is switched to position A, and the entire amount of return oil bypasses the oil cooler 8. As a result, the oil temperature rises rapidly, the viscosity of the cooling oil introduced into the brake case 40 becomes small, and the resistance force (drag resistance) acting on the disks 34, 35 from the oil in the case 40 when the brake is released is reduced. Decrease. As a result, it is possible to efficiently perform the free fall work or the like due to the free fall of the suspended load 106.

When the return oil temperature exceeds a predetermined value T0, the electromagnetic switching valve 10 is switched to the position B, and the entire amount of return oil passes through the oil cooler 8. This allows the brake case 4
The temperature of the cooling oil introduced into zero is reduced, and the frictional heat generated by the pressure contact of the disks 34, 35 during brake operation can be efficiently removed. As a result, disk 3
4 to 36 are cooled, the friction coefficient on the surfaces of the disks 34 and 35 is increased, and a stable braking force can be obtained.

As described above, in the third embodiment, the cooling oil that has passed through the inside of the brake case 40 of the wet multi-plate brake 30 is guided to the oil cooler 8 or the bypass line 9 depending on the oil temperature. Therefore, the temperature rise of the cooling oil above the predetermined value T0 is suppressed, the disks 34 to 36 are cooled, a stable braking force can be obtained, and the drag resistance at the time of releasing the brake can be reduced. Further, since the cooling circuit for the wet multi-plate brake 30 is incorporated in the driving circuit for the actuator 3A, the oil cooler 8 can be shared, the number of parts can be reduced, and the hydraulic circuit can be simplified.

In the above embodiment, the hydraulic pumps 2A, 2
The hydraulic control circuit having two systems of the supply pipelines 5A, 5B from B to the control valves 4A, 4B and the return pipelines 6A, 6B from the control valves 4A, 4B to the tank has been described. Can be similarly applied. Further, although the temperature sensor 11 is provided in the upstream pipe line 7 of the oil cooler 8, it may be provided in another place having a correlation with the return oil temperature. Further, in the above embodiment, a thermostat may be used instead of the temperature sensor 11 and the electromagnetic switching valve 20.

In the correspondence between the above-described embodiment and claims, the hydraulic pumps 2A and 2B serve as hydraulic pressure sources, and the supply pipelines 5A and 5B return to the first supply pipeline and the second supply pipeline, respectively. The pipelines 6A and 6B respectively serve as a first return pipeline and a second return pipeline, the control valve 4A and the hydraulic actuator 3A serve as the first hydraulic equipment, and the control valve 4B, the hydraulic actuator 3B, the control valve 4B and the wet type. The multi-plate brake 30 is the second hydraulic device, the temperature sensor 11 is the oil temperature detecting means, the electromagnetic switching valve 10, the temperature switch 12 and the relay 13, the electromagnetic proportional valve 20 and the controller 21 are the distribution control means, respectively. The multi-plate brake 30 constitutes a braking device.

[0024]

As described in detail above, according to the present invention, at least two return lines of hydraulic circulation paths are joined, and an oil cooler and a bypass line for bypassing the oil cooler are connected to the joining lines. The distribution amount of return oil to the oil cooler and the bypass pipe is controlled according to the detected oil temperature value in the circulation path. As a result, the return oil temperature can be quickly raised when the engine is started, the rise in oil temperature can be suppressed within a predetermined value, and the temperature of the pressure oil flowing through the circulation path can be effectively controlled. .

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a configuration of a hydraulic control circuit according to a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a configuration of a hydraulic control circuit according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an example of an operation by a hydraulic control circuit according to a second embodiment.

FIG. 4 is a hydraulic circuit diagram showing a configuration of a hydraulic control circuit according to a third embodiment of the present invention.

FIG. 5 is a side view of a crane to which the present invention is applied.

[Explanation of symbols]

2A, 2B Hydraulic pump 3A, 3B Hydraulic actuator 4A, 4B Control valve 5A, 5B Supply pipeline 6A, 6B Return pipeline 7 Confluence pipeline 8 Oil cooler 9 Bypass pipeline 10 Electromagnetic switching valve 11 Temperature sensor 12 Temperature switch 13 Relay 20 Electromagnetic proportional valve 21 Controller 30 Wet multi-plate brake

Claims (5)

[Claims] 1. A first circulation path for guiding pressure oil from a hydraulic pressure source to a first hydraulic device from a first supply pipeline, and further returning it to a tank via a first return pipeline; and a second circulation path. A hydraulic control circuit having at least a second circulation path that leads from a supply pipeline to a second hydraulic device and further returns to a tank via a second return pipeline, the first return pipeline and the first A confluent conduit in which the two return conduits join, an oil cooler that cools the return oil in the combined conduit, and a bypass conduit that bypasses the oil cooler and guides the pressure oil from the merged conduit to the tank. An oil temperature detecting means for detecting the oil temperature in the circulation path; and a distribution control means for controlling the distribution amount of the return oil to the oil cooler and the bypass pipeline according to the temperature detected by the oil temperature detecting means. And a hydraulic control circuit comprising: 2. The hydraulic control circuit according to claim 1, wherein when the temperature detected by the oil temperature detecting means exceeds a predetermined value, the distribution control means guides the return oil from the merging conduit to the oil cooler, A hydraulic control circuit having a switching valve that switches so as to guide the return oil from the merging conduit to the bypass conduit at a predetermined value or less. 3. The hydraulic control circuit according to claim 1, wherein the distribution control means opens the valve so that the amount of return oil guided to the oil cooler increases as the temperature detected by the oil temperature detection means increases. A hydraulic control circuit having a flow control valve whose degree is controlled. 4. The hydraulic control circuit according to claim 1, wherein the first circulation path is an actuator drive path that supplies drive pressure oil to a hydraulic actuator, and the second circulation path. The hydraulic control circuit is characterized in that the path is a brake cooling path for supplying cooling oil to the brake device. 5. A crane provided with the hydraulic control circuit according to claim 1.