JPH0960609A - Operating oil bubble eliminating device in hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify piping by arranging a bubble eliminating means on a return oil passage from an operating oil control valve arranged in an operating oil passage for switching control, for operating oil supplied from a hydraulic pump to a hydraulic actuator. SOLUTION: In a bubble eliminating device 5, operating oil is supplied from an outer peripheral part side to a cylindrical body 5a so as to generate spiral flow, bubbles whose specific gravity is smaller than that of operating oil are collected to the center side of the cylindrical body 5a, become large bubbles, and passed the hole of a bubble discharging pipe 5b, and they are discharged to the oil surface part of an oil tank 6 passing an air trap piping E. Bubbles in operating oil are eliminated by the bubble eliminating device 5 in a return oil passage A which is positioned between an operating oil control valve 3 and the oil tank 6. As a result, deairing is carried out effectively even if the capacity in the oil tank 6 can not be enlarged owing to the space, cost, and the like, or even if it is used in a strong vibrating condition. It is thus possible to efficiently carry out deairing in a simple structure without necessitating an oil feed pump and the like, and without complexing piping.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of hydraulic circuits arranged in hydraulic working machines such as hydraulic excavators.

[0002]

2. Description of the Related Art Generally, this type of hydraulic working machine has
A hydraulic actuator that is operated by the hydraulic oil supplied from the hydraulic pump is provided. However, in the hydraulic actuator, bubbles are included in the hydraulic oil due to the compression and expansion of the hydraulic oil accompanying the operation of the hydraulic actuator. When the hydraulic oil containing the bubbles is supplied to the hydraulic pump via the suction line, the bubbles are subjected to a rapid adiabatic compression in the pump, which causes large noise and vibration, and the hydraulic oil. However, there is a problem that heat is generated and deterioration is promoted. Further, there is a possibility that the operating efficiency of the hydraulic actuator may be reduced or destabilized, the control performance may be deteriorated, and degassing is required there. However, such degassing of air bubbles does not pose a problem because the air bubbles in the hydraulic oil spontaneously float on the oil surface when the oil tank is sufficiently large or in stationary use. However, in the case where the capacity of the oil tank cannot be increased to a large extent due to cost and space, or in a machine used in a state where it vibrates violently, it is difficult to remove the air bubbles and the air bubbles remain.

[0003]

Therefore, it has been proposed to use a bubble removing means for deaerating bubbles in the hydraulic oil. In the conventional one, a dedicated bubble removing oil passage is formed from an oil tank. Then, a bubble removing means is provided in the bubble removing oil passage to remove bubbles in the hydraulic oil. In this case, however, an oil feed pump or the like for sending the hydraulic oil in the oil tank to the bubble removing means. However, the number of parts is large and the piping is complicated, and there is a problem to be solved by the present invention.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances in order to solve these problems. In the hydraulic oil supplied from the hydraulic pump to the hydraulic actuator, In providing the bubble removing means for removing the bubbles, the bubble removing means controls the operation of the hydraulic oil supplied from the hydraulic pump to the hydraulic actuator by operating the hydraulic oil control valve arranged in the hydraulic oil passage. It is provided in the return oil passage. As a result, efficient deaeration can be performed with a simple structure in which a bubble removing means is provided in the return oil passage from the hydraulic oil control valve without forming a dedicated bubble removing oil passage. In this structure, a cooling device for cooling the hydraulic oil may be provided upstream or downstream of the bubble removing means in the return oil passage.
Further, the return oil passage is provided with a bypass oil passage that bypasses the bubble removing means, and the bypass oil passage is further provided with opening means for opening the bypass oil passage when the hydraulic pressure of the bypass oil passage exceeds a predetermined pressure. As a result, it is possible to avoid a large flow rate of hydraulic oil that does not effectively act on the bubble removing means from passing through the bubble removing means, and it is possible to avoid that the peak pressure acts on the bubble removing means. The bubble removing means can be effectively protected. Further, in the present invention, when the bubble removing means for removing bubbles in the hydraulic oil supplied from the hydraulic pump to the hydraulic actuator is provided, the hydraulic oil arranged to switch the control of the hydraulic oil from the hydraulic pump to the hydraulic actuator. The control valve is switched by the supply of pilot pressure oil from the pilot control valve, and the bubble removing means is provided in the return oil passage of the pilot pressure oil.
Stable bubble removal can be performed. In this structure, a back pressure adding means for providing a back pressure to the bubble removing means is provided in the return oil passage of the pilot pressure oil and is located on the downstream side of the bubble removing means to ensure the bubble removing function of the bubble removing means. You may do it.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Next, two embodiments of the present invention will be described with reference to the drawings. First, a first embodiment is shown in FIG. 1. In the drawing, reference numeral 1 is a cylinder type hydraulic actuator provided in a construction machine such as a hydraulic excavator. A hydraulic oil bubble removal device is implemented. Here, 2 is a hydraulic pump for supplying hydraulic oil to the hydraulic actuator 1. In the oil passage from the hydraulic pump 2 to the hydraulic actuator 1, hydraulic oil supply control to the hydraulic actuator 1 is performed. A hydraulic oil control valve 3 is provided for this purpose.

The hydraulic oil control valve 3 is a three-position switching valve. The first port 3a is connected to the hydraulic pump 2 and the second port 3b is connected via a cooler 4, a bubble removing device 5 and the like which will be described later. In the return oil passage A leading to the oil tank 6, the third port 3
c is on the extension side port 1a of the hydraulic actuator 1,
The fourth ports 3d are respectively connected to the reduction side ports 1b. Further, the hydraulic oil control valve 3 is formed with extension-side and reduction-side pilot ports 3e and 3f. Then, in a state in which the pilot pressure oil is not supplied to both pilot ports 3e and 3f, the first to fourth ports 3a to 3d are located in the closed neutral position, but the pilot pressure oil to the extension side pilot port 3e. Is supplied, hydraulic oil from the hydraulic pump 2 is supplied to the expansion side port 1
The hydraulic pump 2 is supplied to the hydraulic pressure pump 2a by switching to the expansion side position where the hydraulic oil from the reduction side port 1b is discharged to the return oil passage A, and the pilot pressure oil is supplied to the reduction side pilot port 3f. Hydraulic oil from the reduction side port 1
It is configured to switch to the reduction side position in which the hydraulic oil supplied to b and discharged from the extension side port 1a is discharged to the return oil passage A.

On the other hand, 7 is a pilot pump, and the pilot pressure oil supplied from the pilot pump 7 is
A pilot port 3e of the hydraulic oil control valve 3 via a filter 8 and a pilot control valve 9 described later,
It is configured to be supplied to 3f.

That is, the pilot control valve 9 is
Although the extension side valve portion 9X and the contraction side valve portion 9Y are configured, since the both valve portions 9X and 9Y have the same structure, the extension side valve portion 9X will now be described. Has a first port 9a connected to the filter 8 and a second port 9b connected to the hydraulic oil control valve 3
Is connected to the expansion side pilot port 3e. The third port 9c is connected to a pilot return oil passage C that joins a suction line B extending from the oil tank 6 to the hydraulic pump 2 and the pilot pump 7. When the operation lever (not shown) is in the neutral position, the valve portions 9X and 9Y are in a state in which the first port 9a is closed and the second port 9b and the third port 9c are in communication with each other. Based on the operation on the extension side or the reduction side, the first port 9a and the second port 9b of the corresponding extension side valve portion 9X or reduction side valve portion 9Y are brought into communication with each other, whereby the pilot pump 7 The pilot pressure oil is supplied to the corresponding pilot port 3e or 3f. In addition, 1
Reference numeral 0 denotes a pilot relief valve provided in a relief oil passage G that branches from an oil passage extending from the filter 8 to the pilot control valve 9 and joins the pilot return oil passage C. The supply pressure of the pressure oil supplied to the pilot control valve 9 is determined.

In the return oil passage A from the hydraulic oil control valve 3 to the oil tank 6, a cooler 4, a bubble removing device 5, and a filter 11 are arranged from the hydraulic oil control valve 3 side. Here, the cooler 4 is for cooling the hydraulic oil, but in the cooler bypass oil passage D connected in parallel to the cooler 4, the bypass oil passage D is connected to the oil tank 6 side. A check valve 12 with a spring is provided which opens when the pressure of the hydraulic oil flowing toward it becomes equal to or higher than a predetermined pressure, so that it is possible to prevent excessive pressure from being applied to the cooler 4. . The cooler 4 may be provided on the downstream side of the bubble removing device 5 as shown in FIG.

On the other hand, the bubble removing device 5 in the present embodiment, as shown in FIG. 2, generates a vortex flow by feeding hydraulic oil into the cylindrical body 5a from the outer peripheral side, and the vortex flow causes the vortex flow to occur. The generated centrifugal force separates the hydraulic oil and the bubbles having different specific gravities. In this case, the bubbles having a smaller specific gravity than the hydraulic oil are concentrated on the center side of the cylindrical body 5a to become large bubbles. Passing through the hole of the bubble discharge pipe 5b, and this is the air trap pipe (drain line) E.
It is configured to be discharged to the oil surface surface portion of the oil tank 6 via.

Further, F is a bypass circuit for a bubble removing device which is connected in parallel to the bubble removing device 5,
The bypass oil passage F is provided with a spring-equipped check valve 13 that opens when the pressure of the working oil flowing toward the oil tank 6 side becomes equal to or higher than a predetermined pressure. It is possible to avoid that a large amount of hydraulic fluid that the removing device 5 does not work effectively passes through the bubble removing device 5, and
It is possible to prevent the peak pressure from acting on the bubble removing device 5. By the way, check valve with spring 13
Instead of this, it goes without saying that an opening means such as a relief valve which is opened by being appropriately pressurized can be employed.

In the structure configured as described above, the bubbles contained in the hydraulic oil are removed by the bubble removing device 5 provided in the return oil passage A from the hydraulic oil control valve 3 to the oil tank 6. Become. As a result, even when the capacity of the oil tank 6 cannot be increased so much due to space and cost, or even when the oil tank 6 is used in a state where it vibrates violently, it can be effectively degassed and bubbles remain. It is possible to avoid the occurrence of a problem such as a decrease in the operating efficiency of the hydraulic actuator 1 that occurs in some cases.

Moreover, since the bubble removing device 5 is provided in the return oil passage A from the hydraulic oil control valve 3 to the oil tank 6, a dedicated bubble removing oil passage is formed from the conventional oil tank to remove bubbles. As in the case where the means is provided, there is no need for a dedicated member device such as an oil feed pump and the piping is not complicated, and the bubble removing device 5 is provided in the return oil passage A necessary for the pressure oil circuit of the hydraulic actuator 1. With a simple structure provided with only, it is possible to perform efficient deaeration without affecting the control of the hydraulic actuator 1.

Next, a second embodiment is shown in FIG.
In the drawings, components common to the first embodiment (the same components) are denoted by the same reference numerals, are drawn, and the details are omitted. In this device, the bubble removing device 5 is not provided in the return oil passage A from the hydraulic oil control valve 3 to the oil tank 6, but is in the pilot return oil passage C that joins the pilot release valve 10 to the suction line B.
It is provided in. Furthermore, this pilot return oil passage C
Is provided with a check valve 14 with a spring, which is located on the downstream side of the bubble removing device 5 and opens when a pressure equal to or higher than a predetermined pressure is applied. As a result, it is possible to promote the bubble discharging efficiency from the hole of the bubble discharging pipe 5b of the bubble removing device 5.

In the second embodiment described above, the return oil flowing through the pilot return oil passage C is a stable flow with a small flow rate but little fluctuation in the amount of oil discharged from the pilot relief valve 10. There is an advantage that the removal can be performed stably.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment.

FIG. 2A is a sectional view of a bubble removing device, and FIG. 2B is a sectional view taken along line AA of FIG.

FIG. 3 is a hydraulic circuit diagram showing another example of the first embodiment.

FIG. 4 is a hydraulic circuit diagram showing a second embodiment.

[Explanation of symbols]

 1 Hydraulic Actuator 2 Hydraulic Pump 3 Hydraulic Oil Control Valve 4 Cooler 5 Bubble Remover 9 Pilot Control Valve 10 Pilot Relief Valve 13 Spring Check Valve 14 Spring Check Valve A Return Oil Path C Pilot Return Oil Path F For Bubble Remover Bypass oil passage

Claims (5)

[Claims] 1. When providing a bubble removing means for removing bubbles in hydraulic oil supplied from a hydraulic pump to a hydraulic actuator, the bubble removing means controls the hydraulic oil supplied from the hydraulic pump to the hydraulic actuator. A hydraulic oil bubble removing device in a hydraulic circuit provided in a return oil passage from a hydraulic oil control valve arranged in a hydraulic oil passage for switching. 2. The hydraulic oil bubble removing device in a hydraulic circuit according to claim 1, wherein a cooling device for cooling hydraulic oil is provided upstream or downstream of the bubble removing means in the return oil passage. 3. The return oil passage according to claim 1, wherein a bypass oil passage bypassing the bubble removing means is provided in the return oil passage, and the bypass oil passage is bypassed when the hydraulic pressure of the bypass oil passage exceeds a predetermined pressure. A hydraulic oil bubble removing device in a hydraulic circuit, further comprising opening means for opening an oil passage. 4. A hydraulic fluid arranged to switch control of hydraulic fluid from the hydraulic pump to the hydraulic actuator when providing a bubble removing means for removing bubbles in the hydraulic fluid supplied from the hydraulic pump to the hydraulic actuator. The control valve is switched by supplying pilot pressure oil from the pilot control valve, and the bubble removing means is
A hydraulic oil bubble removing device in a hydraulic circuit provided in a return oil passage for pilot pressure oil. 5. The hydraulic pressure according to claim 4, wherein the return oil passage for the pilot pressure oil is provided with a back pressure adding means located downstream of the bubble removing means for applying a back pressure to the bubble removing means. Oil bubble removal device in circuit.