JPH07331698A - Hydraulic oil tank for construction machinery - Google Patents

Abstract

(57) [Abstract] [Purpose] The small and compact structure increases the liquid level of the hydraulic oil tank only when the hydraulic pump stops working and the hydraulic oil tank is almost at atmospheric pressure. Prevents air from getting inside. [Structure] An auxiliary tank 20 is connected to a tank body 11 of a hydraulic oil tank 10, and an oil chamber 20 is connected to the auxiliary tank 20.
a and a piston 21 that is partitioned into the air chamber 20b,
A compression spring 22 acting on the piston 21 is provided, and the atmosphere opening port 23 is provided on the upper surface of the auxiliary tank 20.
Is formed, and the air chamber 20b is open to the atmosphere.
An oil passage 24 is connected to the bottom surface of the auxiliary tank 20, and the other end of the oil passage 24 is connected below the lowest liquid level of the tank body 11. As a result, the hydraulic pump 12
When the inside of the tank body 11 of the hydraulic oil tank 10 is brought to an almost atmospheric pressure state, the hydraulic oil flows into the tank body 11 from the auxiliary tank 20 side, and the pressure in the tank body 11 rises. , Tank body 11 to auxiliary tank 2
Hydraulic fluid flows to zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic oil tank provided in a construction machine such as a hydraulic excavator.

[0002]

2. Description of the Related Art A construction machine is equipped with a hydraulic pump 1 as shown in FIG. 5, and a hydraulic oil supply pipe 1a and a discharge pipe 1b are connected to the hydraulic pump 1 to form a hydraulic oil supply pipe. The hydraulic oil supplied via 1a is pressurized, and this hydraulic oil is supplied from a discharge pipe 1b via a direction switching valve 2 to a hydraulic actuator 3 composed of a hydraulic cylinder, a hydraulic motor, etc., to drive the hydraulic actuator 3. It is supposed to do. A hydraulic oil tank 4 is provided to supply hydraulic oil to the hydraulic pump 1 and to recirculate the return oil from the hydraulic actuator 3. The hydraulic oil tank 4 has a tank main body 4a having a predetermined capacity, which is connected to the other end of the hydraulic oil supply pipe 1a to the hydraulic pump 1 and a return pipe 4b into which the return oil from the hydraulic actuator 3 flows. Is.

A hydraulic cylinder, which is a type of hydraulic actuator 3, is divided into a bottom chamber and a rod chamber by a piston. A piston rod is connected to the piston, and the piston rod penetrates the rod chamber. Therefore, since the amount of hydraulic oil stored in the cylinder changes between when the piston rod is extended and when the piston rod is contracted, the amount of hydraulic oil in the hydraulic oil tank also changes according to the operation of the hydraulic actuator 3. Will be done. In FIG. 5, a single hydraulic cylinder is shown as a hydraulic actuator for simplification. However, in the hydraulic excavator, one or more boom cylinders are provided to drive the front working mechanism, An arm cylinder, a bucket cylinder, etc. are mounted, and it is the hydraulic oil tank 4 that supplies hydraulic oil to these hydraulic cylinders and recirculates the return oil. Therefore, there is a considerable difference in the amount of hydraulic oil in the hydraulic oil tank 4 between when the piston rods of all these hydraulic cylinders are extended and when they are contracted. Further, in the case of a hydraulic excavator, in addition to this front work mechanism, there are also those equipped with blades, outriggers, etc., which are also driven by a hydraulic cylinder to supply hydraulic oil from the same hydraulic oil tank 4. As a result, these hydraulic cylinders are driven. As the hydraulic actuator, there is a hydraulic motor in addition to the hydraulic cylinder, but the hydraulic motor does not change the volume of the hydraulic oil during operation.

As described above, when the hydraulic actuator 3 is operated, the height position of the liquid level in the hydraulic oil tank 4 changes, so that the amount of hydraulic oil contained in the hydraulic oil tank 4 is the liquid level. 5 is the level L _max shown by the phantom line in FIG. 5, and the lowest position is the level L _min shown by the solid line.
To be set. A relief valve 5 is attached to the hydraulic oil tank 4 in order to prevent the pressure in the hydraulic oil tank 4 from changing due to a change in the liquid level of the hydraulic oil tank 4. When the liquid level rises, the internal air pressure is released, and when the liquid level falls, air is taken in from the outside.

[0005]

In a construction machine such as a hydraulic excavator, the hydraulic pump 1 and the hydraulic oil tank 4 are generally installed on the upper swing body 6 as shown in FIG. It is installed in the machine room 7 where
In addition to the hydraulic pump 1 and the hydraulic oil tank 4, various machines and members are arranged in the machine room 7. And
The positional relationship between the hydraulic pump 1 and the hydraulic oil tank 4 is determined by the structure of the machine room 7, various devices mounted therein, and the like, and they are normally arranged at substantially the same height position.

By the way, while the hydraulic pump 1 is in operation, the hydraulic oil is sucked from the hydraulic oil tank 4, so that the hydraulic oil circulates in the entire hydraulic circuit. However, the hydraulic pump 1 is kept in the neutral position with the directional control valve 2 held in the neutral position. When 1 stops, the pressure in the hydraulic oil tank 4 becomes substantially atmospheric pressure, and the center bypass passages of the hydraulic pump 1 and the direction switching valve 2 also become atmospheric pressure. On the other hand, the liquid level of the hydraulic oil tank 4 changes depending on the state of the hydraulic actuator 3. Therefore, when all the hydraulic cylinders constituting the hydraulic actuator 3 are in the extended state, the liquid level of the hydraulic oil tank 4 is at the lowest position, and is considerably lower than the return pipe 4b. It will be located above the liquid level of the tank 4. As a result, the hydraulic oil on the path from the hydraulic pump 1 to the hydraulic oil tank 4 via the center bypass flow path of the directional control valve 2 is returned to the hydraulic oil tank 4, and thus the hydraulic oil is transferred to the hydraulic pump 1. Air may enter. If the hydraulic pump 1 is restarted in this state, cavitation may occur in the hydraulic pump 1 or in the path from the hydraulic pump 1 to the hydraulic actuator 3, resulting in damage to the hydraulic circuit components. Inconvenience occurs.

Of course, if the hydraulic pump 1 and the directional control valve 2, especially the hydraulic pump 1 is arranged below the lowest liquid level of the hydraulic oil tank 4, there is no possibility of air mixing as described above. However, the hydraulic pump 1 and the hydraulic oil tank 4
The hydraulic pump 1 cannot always be arranged at a position lower than the liquid level of the hydraulic oil tank 4 because the positional relationship between the hydraulic pump 1 and the hydraulic fluid is restricted by other members. It is also possible to increase the liquid level of the hydraulic oil tank 4 while keeping the positional relationship between the hydraulic pump 1 and the hydraulic oil tank 4 as is. For this purpose, the depth of the hydraulic oil tank 4 should be increased. , Or it is necessary to raise the liquid level itself, and in the former case, the hydraulic oil tank 4 becomes large,
With the latter configuration, the air layer of the hydraulic oil tank 4 is reduced, which causes a problem that the pressure fluctuation in the hydraulic oil tank 4 becomes large during operation.

The present invention has been made in view of the above points, and an object thereof is to ensure that air enters the hydraulic pump when the operation of the hydraulic pump is stopped by the small and compact structure. To prevent it.

[0009]

In order to achieve the above-mentioned object, the present invention provides a tank main body with an oil chamber having a variable volume, and pressurizing so as to reduce the volume of the oil chamber. It is characterized in that an auxiliary tank on which the means is operated is additionally provided, and the oil chamber of the auxiliary tank and the inside of the tank body are connected by an oil passage.

[0010]

When the hydraulic pump is stopped, the inside of the tank body of the hydraulic oil tank is substantially at atmospheric pressure. On the other hand, since the pressurizing means acts on the oil chamber of the auxiliary tank, the hydraulic oil in the auxiliary tank flows into the tank body, and the liquid level in the tank body rises. As a result, the hydraulic pump is located at a position lower than the liquid level in the tank body, and there is no possibility that air will enter the hydraulic pump. On the other hand, when the hydraulic pump operates, the liquid level of the hydraulic oil in the tank body rises and falls. The liquid level rises and the pressure in the tank body rises. However, if this pressure exceeds the pressure applied by the pressurizing means, the hydraulic oil in the tank body will flow into the auxiliary tank, so there is no risk of the air pressure in the tank body rising abnormally, and of course the operation. There is no risk of the oil level reaching the top wall of the tank body.

As described above, by providing the auxiliary tank, it is not necessary to increase the capacity of the tank main body, so that the installation space of the tank main body can be secured without interfering with other members and devices. Moreover, the auxiliary tank may be much smaller than the tank body,
Moreover, the auxiliary tank can be provided at an arbitrary position by connecting the auxiliary tank and the tank body with a pipe. In the machine room, various members and devices are arranged, but there are parts that are dead spaces to some extent, such as between devices, and by using such dead spaces, The auxiliary tank can be installed without changing the layout of the machine room.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a schematic configuration of a hydraulic oil tank and a hydraulic circuit of a construction machine according to the present invention. In the figure, a hydraulic oil tank 10 includes a tank main body 11, a hydraulic oil supply pipe 11a, and a return pipe 1 in the tank main body 11.
It is configured by connecting with 1b. The hydraulic oil supply pipe 11a is opened at the bottom surface of the tank body 11, and the return pipe 11b is opened at a relatively upper position of the tank body 11.

The hydraulic oil supply pipe 11a is connected to the suction port 12a of the hydraulic pump 12, and the hydraulic pump 1
The pipe 13 from the second outlet 12b is connected to the direction switching valve 14, and the return pipe 1 is connected to the direction switching valve 14.
1b is also connected. Piping 15 from the direction switching valve 14
The bottom chamber 16a and the rod chamber 16b of the hydraulic cylinder 16 as a hydraulic actuator are connected to a and 15b.

Now, when the hydraulic pump 12 is operated, hydraulic oil circulates in the hydraulic circuit. In this state, the direction switching valve 14 is used to cause the bottom chamber 1 of the hydraulic cylinder 16 to move.
6a is connected to the hydraulic pump 12, and the rod chamber 16b is switched to a state in which it is connected to the return pipe 11b. As a result, hydraulic oil is sucked from the tank body 11 of the hydraulic oil tank 10 to the hydraulic pump 12, and the hydraulic pump 1
The pressure oil is pressurized at 2, and the pressure oil is supplied to the bottom chamber 16a of the hydraulic cylinder 16 through the pipe 13, the direction switching valve 14 and the pipe 15a in order, and at the same time, the hydraulic oil in the rod chamber 16b switches the direction from the pipe 15b. Return pipe 1 via valve 14
It flows to 1b and returns to the inside of the tank main body 11. As a result, the hydraulic cylinder 16 operates and the piston rod 17 thereof extends. When the direction switching valve 14 is switched in the opposite direction, the piston rod 17 of the hydraulic cylinder 16 operates in the contracting direction. Further, the directional control valve 14 has a neutral position, and at this neutral position,
The hydraulic oil sucked into the hydraulic pump 12 is fed from the pipe 13.
It will be returned to the tank main body 11 via the return pipe 11b through the center bypass passage provided in the direction switching valve 14, and at this time, no work is performed. In the figure, 17 is a relief valve provided in the hydraulic oil tank 10.

In the tank body 11 of the hydraulic oil tank 10,
The auxiliary tank 20 is connected. This auxiliary tank 20
Is a piston 21 and this piston 2 as pressurizing means.
1 and a compression spring 22 that acts on the auxiliary tank 20.
By means of the piston 21, the oil chamber 20a and the air chamber 20b
It is divided into sections. An atmosphere opening port 23 is formed on the upper surface of the auxiliary tank 20, and the air chamber 20b is opened to the atmosphere through the atmosphere opening port 23. An oil passage 24 is connected to the bottom surface of the auxiliary tank 20, and the oil passage 24 is connected to the tank body 11. The connection position of the oil passage 24 is from the lowest liquid level in the tank body 11. It is below. Here, the minimum liquid level is a state in which the maximum amount of hydraulic oil is taken in by the hydraulic actuator,
That is, it is a position below the liquid surface of the tank main body 11 when all the hydraulic cylinders constituting the hydraulic actuator are in the most extended state.

The present embodiment is constructed as described above, and its operation will be described below.

First, in a construction machine such as a hydraulic excavator, in general, when the hydraulic oil tank 10, the hydraulic pump 12, and the directional control valve 14 are arranged such that their respective height positions are substantially in the positional relationship shown in FIG. There are many. In FIG. 1, a single hydraulic cylinder 16 is shown as a hydraulic actuator for simplification.
To boom cylinders, arm cylinders,
In some cases, a bucket cylinder or the like is mounted, and in addition to the front working mechanism, a member driven by a hydraulic cylinder is provided. The hydraulic oil tank 10 is adapted to supply hydraulic oil to all of these hydraulic cylinders.

Thus, when the hydraulic pump 12 is stopped, the inside of the tank body 11 of the hydraulic oil tank 10 is substantially at atmospheric pressure. Oil chamber 20a of the auxiliary tank 20
Is pressurized by the compression spring 22 acting on the piston 21, so that the working oil in the auxiliary tank 20 flows through the oil passage 24.
Will be introduced into the tank main body 11 via. As a result, as shown in FIG. 1, since the liquid level in the tank body 11 rises and the hydraulic pump 12 is positioned below the liquid level of the tank body 11, air may enter the hydraulic pump 12. There is no.

On the other hand, when the hydraulic pump 12 is actuated and pressure oil is supplied to the hydraulic cylinder 16 and the like, depending on the state of the hydraulic cylinder 16, the hydraulic cylinder 16 is more likely to be supplied than the amount of hydraulic oil supplied to the hydraulic pump 12. As a result, the amount of hydraulic oil flowing back from the tank main body 11 to the tank main body 11 becomes larger.
The liquid level inside is about to rise. Since the volume of the air layer in the tank main body 11 is quite small as described above, the pressure of this air layer increases relatively early. However, as shown in FIG. 2, this pressure reaches the auxiliary tank 20 through the oil passage 24, and the pressure in the oil chamber 20a in the auxiliary tank 20 increases in conjunction with this, and the piston 21 is compressed. Since it is pushed up against the spring 22, the liquid level in the tank body 11 does not rise further, and the internal pressure does not become abnormally high.

As described above, when the hydraulic pump 12 is stopped, the auxiliary tank 20 supplies hydraulic oil into the tank body 11 to raise the liquid level in the tank body 11, and the hydraulic actuator operates. When the amount of return oil increases, hydraulic oil flows in from the tank body 11 to prevent the inside of the tank body 11 from becoming an abnormal pressure state.
This is based on the action of the compression spring 22 on the piston 21. Therefore, when the pressure applied to the piston 21 by the compression spring 22 is set to an intermediate value between the atmospheric pressure and the pressure set by the relief valve 17, when the inside of the tank body 11 is in the atmospheric pressure state, the inside of the auxiliary tank 20 is When almost the entire amount of the hydraulic oil of (1) flows into the tank main body 11 and the hydraulic actuator operates to increase the pressure inside the tank main body 11, the auxiliary tank 20 quickly becomes almost full. By adjusting the pressing force in this way, even the small-sized auxiliary tank 20 having a small capacity can sufficiently exhibit its function.

Next, FIG. 3 shows a second embodiment of the present invention. In this embodiment, the piston 31 mounted on the auxiliary tank 30 is horizontally reciprocated by the compression spring 32 elastically mounted in the horizontal direction. An oil passage 33 connected to the tank body 11 of the hydraulic oil tank 10 is formed at the end surface of the oil chamber 30a of the auxiliary tank 30.

That is, the auxiliary tank may be placed upright as shown in the first embodiment, or may be placed horizontally as shown in the second embodiment. According to the shape of the dead space in the room, the arrangement, direction, etc. of the auxiliary tank can be arbitrarily set, and the degree of freedom in the arrangement layout is increased.

FIG. 4 shows a third embodiment of the present invention. In this embodiment, the auxiliary tank 40 is formed of a bellows type flexible container, and the auxiliary tank 40 has Is connected to an oil passage 41, one end of which is connected to the tank body 11. A weight 42 abuts on the auxiliary tank 40, and the weight of the weight 42 pressurizes the hydraulic oil in the auxiliary tank 40. Further, the auxiliary tank 40 is surrounded by a protective cylinder 43, and the protective cylinder 43 protects the auxiliary tank 40 made of a flexible bag so as not to be damaged, and also has a weight 42.
It also functions as a weight guide member for vertically guiding the.

Even with this construction, the working oil is supplied and discharged from the auxiliary tank 40 in accordance with the pressure fluctuations in the tank body 11, and as in the first embodiment, the inside of the tank body 11 is discharged. When the pressure is at atmospheric pressure, the hydraulic oil flows from the auxiliary tank 40 into the tank body 11, the liquid level in the tank body 11 rises, and the auxiliary tank 40 shrinks. When the hydraulic pump operates and the hydraulic actuator is driven, and the pressure in the tank body 11 rises, hydraulic oil flows into the auxiliary tank 40 from the tank body 11 side, and the auxiliary tank 40 expands. And the auxiliary tank 4
Since the pressure applied to 0 is based on the weight of the weight 42, even if the amount of hydraulic oil in the auxiliary tank 40 changes and the volume changes, the auxiliary tank 40 still has
An almost constant pressing force can always be applied, and the pressing force can be adjusted accurately.

[0025]

As described above, according to the present invention, the auxiliary tank is attached to the tank body, and the pressurizing means is acted on the auxiliary tank so that the auxiliary tank can be operated in accordance with the fluctuation of the pressure in the tank body. Since the hydraulic oil is supplied to and discharged from the tank body, the small and compact structure has an effect such that it is possible to reliably prevent air from entering the hydraulic pump when the hydraulic pump is stopped.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a hydraulic circuit of a construction machine showing a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a hydraulic circuit showing an operating state different from that in FIG.

FIG. 3 is a schematic configuration diagram of a hydraulic circuit of a construction machine showing a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a hydraulic circuit of a construction machine showing a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a hydraulic circuit of a construction machine in the related art.

FIG. 6 is an explanatory diagram showing a configuration of a machine room of a hydraulic excavator as a construction machine.

[Explanation of symbols]

 10 Hydraulic Oil Tank 11 Tank Body 12 Hydraulic Pump 14 Directional Switching Valve 16 Hydraulic Cylinder 20, 30, 40 Auxiliary Tank 21, 31 Piston 22, 32 Compression Spring 24, 33, 41 Oil Path 42 Weight

Claims (2)

[Claims] 1. A tank main body which supplies hydraulic oil to a hydraulic pump, pressurizes the hydraulic oil by the hydraulic pump, and supplies pressure oil to a hydraulic actuator to drive the hydraulic oil, and to circulate return oil from the actuator. In the provided hydraulic oil tank, the tank main body is provided with an oil chamber having a variable volume, and an auxiliary tank having a pressurizing means for pressurizing it so that the volume of the oil chamber becomes small is attached. A hydraulic oil tank for a construction machine, characterized in that the oil chamber and the inside of the tank body are connected by an oil passage. 2. When the hydraulic oil tank is at atmospheric pressure, the amount of hydraulic oil in the auxiliary tank becomes substantially zero,
When the pressure of the hydraulic oil tank reaches the maximum value, the pressure of the pressurizing means for the auxiliary tank is set so that the auxiliary tank is almost filled with hydraulic oil. A hydraulic oil tank for a construction machine according to claim 1.