JPH0335904Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The invention relates to a pneumatic circuit for civil engineering construction machinery.
In particular, the present invention relates to a circuit for draining a tank that stores compressed air discharged from an air compressor.

(Conventional technology) The conventional pneumatic circuit for civil engineering and construction machinery is
It is configured as shown in the figure. In Figure 3, 2
is an air compressor, and the air compressor 2 includes a fourth
As shown in figures a and b (a indicates the on-load state and b indicates the unload state), the discharge valve 13 is pushed down when the air pressure inside the compressor 2 increases.
, an unload valve 14 that is pushed down by an unload signal, and an air supply valve 15 that is opened by negative pressure in the cylinder during the air supply process and is pushed open by the unload valve 14 during unloading. is installed.

Also, in Fig. 3, 3 is a wet tank that cools the high temperature, high pressure compressed air discharged from the air compressor 2, stores condensed water at the bottom, and sends dry air downstream; 4 is the air pressure of the wet tank 3. This is a governor that outputs an unload signal to the air compressor 2 when the pressure rises above a predetermined pressure. 6 is a dry tank that stores compressed air after dehumidification sent from the wet tank 3 via the check valve 5; 7 is a safety valve connected to the dry tank 6; 10 is a safety valve 10
The hydraulic oil tank 10 is connected to the dry tank 6 via a filter 8, a pressure reducing valve 9 and a check valve 11. The dry tank 6 is also connected to a pneumatic pump 12A that discharges lubricating grease and an accumulator 12B that backs up pilot oil pressure.

In such a pneumatic circuit, the air compressor 2
After the lubricating oil lubricates between the cylinder 2b and piston 2a of the air compressor 2, a portion of the lubricating oil is supplied to the discharge valve 1.
3 and lubricates the discharge valve 13, most of it remains exposed and is discharged together with the compressed air.
Furthermore, in the high-temperature, high-pressure compressed air created by the air compressor 2, the lubricating oil is oxidized, and as a result, carbon is generated. Moreover, when the compressed air created in this way is cooled, the moisture in this compressed air condenses to become water, which mixes with the lubricating oil and becomes highly viscous drain. Such carbon and drain are removed by the pneumatic pump 12A and the accumulator 1.
In the pneumatic discharge system including the pneumatic equipment such as 2B, this may cause blockage of the flow path, malfunction, damage, and contamination of the hydraulic oil in the hydraulic oil tank 10.

For this reason, in conventional pneumatic circuits, for example, a manual drain valve is attached to the wet tank 3, and when the operator opens this drain valve, the drain containing carbon is discharged to the outside. That's what I do. Therefore, in this conventional pneumatic circuit, when draining the drain, it is necessary to get close to the wet tank 3 and to manually open and close the drain valve. Drainage work becomes troublesome, and moreover, there is a risk that the drain containing carbon may adhere to the operator, making him or her more likely to be contaminated.

Furthermore, in this conventional pneumatic circuit, compressed air is hardly consumed after the hydraulic oil tank 10 is pressurized, and therefore the air compressor 2 is operated mostly in an unloaded state. During this unloading, as shown by the arrow 4a in FIG. 4b, a signal 4a from the governor 4 shown in FIG.
5 remains open, and the air piston 2a in the air compressor 2 moves up and down to repeatedly move in and out via the air supply valve 15. In such a case, the amount of oil carried out from the air compressor 2 along with the air is larger than when on-road, and this oil adheres to the portion of the air supply valve 15 where the passage is constricted. The amount of oil adhering to the air supply valve 15 increases due to unloading over a long period of time, and this oil is pressurized together with the air supply and discharged to the discharge system within a short on-load time.
Furthermore, in such a state, the amount of carbon produced also increases.

Therefore, in order to avoid such a situation where the amount of carbon generated increases, it is necessary to open the wet tank 3 to the outside as appropriate in consideration of releasing the unloading, but in the conventional pneumatic circuit, As mentioned above, it is difficult to open the drain valve due to the trouble of having to open it manually. There was a problem in that hydraulic equipment was susceptible to malfunction, damage, and staining due to carbon.

(Problems to be solved by the invention) In view of the above-mentioned problems of the conventional pneumatic circuit, the present invention is a civil engineering project that enables reliable draining without the troublesome effort of manually opening the drain valve of a wet tank. The purpose is to provide pneumatic equipment for construction machinery.

(Means for solving the problem) In order to achieve this object, the present invention includes an air compressor driven by a prime mover, a tank for storing compressed air discharged from the air compressor, and a tank connected to the tank. A pneumatic circuit for civil engineering construction machinery equipped with a drain valve, comprising a detection means for detecting a stoppage of the prime mover, and a control means for opening the drain valve for a predetermined period of time from the time when the detection means detects a stoppage of the prime mover. This is characterized in that the drain valve is automatically opened even if the operator does not care about the drain valve, so that the drain is reliably discharged.

(Example) The details of the present invention will be explained below with reference to an example shown in the drawings. FIG. 1 shows an embodiment of the pneumatic circuit of the present invention, and the same parts as in FIG. 3 are given the same reference numerals. In FIG. 1, 1 is a prime mover that drives an air compressor 2, and 12 is the aforementioned pneumatic pump 12A.
and pneumatic equipment such as the accumulator 12B.
16 is a drain valve connected to wet tank 3, 1
7 is a solenoid valve provided as a pilot valve for the drain valve 16;
It is inserted into a circuit 23 that connects the pilot port of the dry tank 6 and the discharge side circuit 22 of the dry tank 6.
Reference numeral 20 denotes a control circuit that controls the energization of the solenoid of the solenoid valve 17. After the motor 1 has stopped, the solenoid is energized for a predetermined time from the power supply 21, and during this predetermined time, the solenoid valve 17 is turned on as shown in FIG. The position is switched from the position to the B position, compressed air is introduced from the discharge side circuit 22 of the dry tank 6 to the pilot port of the drain valve 16, the drain valve 16 is opened, and the drain in the wet tank 3 is discharged. In the control circuit 20, various means can be considered to detect the stoppage of the prime mover 1, such as detecting the actual operation of the prime mover, but in this embodiment, the on/off state of the key switch 19 of the prime mover 1 In view of this, the stoppage of the prime mover 1 is detected by detecting that the voltage of the secondary circuit of the key switch 19 becomes zero.

FIG. 2 shows an example of the control circuit 20, which includes a detection circuit 24 that detects the OFF state of the key switch 19, and a detection circuit 24 that turns on the output for a set time from the time when the detection circuit 24 detects the OFF state of the key switch 19. and a drive circuit 26 that energizes the solenoid of the electromagnetic valve 17 for a set time. Note that the detection circuit 24 and the timer circuit 25 can also be configured using a microcomputer.

According to the circuit shown in FIGS. 1 and 2, the solenoid valve 17 is switched to the B position for the time set in the timer circuit 25 (for example, 5 seconds) from the time the key switch 19 is turned off. The drain valve 16 is opened and the drain containing carbon in the wet tank 3 is discharged to the outside, and after the set time, the solenoid valve 17 is opened.
Since the drain valve 16 returns to the position and closes, the drain valve 16 automatically closes without requiring operator operation.
6 is opened and closed, and the drain can be automatically discharged.

When restarting the prime mover 1, the air pressure in the wet tank 3 has decreased due to the opening operation of the drain valve 16, so the governor 4 closes, and the air compressor 2 becomes on-load.
Since the oil adhering to the air supply valve 15 is discharged to the discharge system, the amount of oil adhering to the air supply valve 15 can be suppressed.

In the above embodiment, the drain valve 16 may be a solenoid valve, and the output of the drive circuit 26 may be applied to the solenoid of the drain valve.

(Effects of the invention) As described above, the pneumatic circuit of the invention includes a means for detecting the stoppage of the prime mover and a control means for opening the drain valve for a predetermined period of time from the time when the prime mover stops. Since the drain can be automatically discharged without worrying about the drain valve or performing any operations, the drain can be discharged more reliably than when the drain valve is opened manually. Therefore, it is possible to reliably suppress the amount of oil adhering to the air supply valve portion of the air compressor, thereby reducing the amount of carbon contained in the compressed air downstream of the wet tank.
It is possible to prevent malfunction, damage, and staining of pneumatic equipment and various hydraulic equipment due to carbon. Further, according to the present invention, there is no need for the operator to approach the drain valve, which reduces the burden on the operator and prevents contamination due to drain.
In addition, in this invention, the drain is discharged for a predetermined period of time after the prime mover stops, so even when used in cold regions or during cold weather, the drain discharge operation occurs before the wet tank cools down. - Like the one disclosed in No. 121983 that discharges condensate at the time of starting the compressor motor, the drain valve does not become inoperable due to freezing, and condensate does not remain and solidify, ensuring that condensate is discharged reliably. It will be done.

Furthermore, as disclosed in the above-mentioned publication, if the drain is discharged when the prime mover is started, it may cause a drop in the tank internal pressure and impair the compressor function. Therefore, the drain is discharged while the internal pressure of the wet tank is sufficiently increased, and the compressor function is not impaired.

Furthermore, according to the present invention, by discharging the drain after stopping the prime mover, no compressed air remains in the wet tank, which is not only safe, but also prevents unnecessary loads from being placed on the pneumatic piping system, improving the durability of the pneumatic piping system. Sex increases.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of the pneumatic circuit according to the present invention, Fig. 2 is a circuit diagram showing an example of the control circuit shown in Fig. 1, and Fig. 3 is a conventional pneumatic circuit. The circuit diagram and FIGS. 4a and 4b are cross-sectional views showing the air compressor included in the pneumatic circuit shown in FIG. 3 in an on-load state and an unload state, respectively.

Claims (1)

[Claims for Utility Model Registration] 1. A pneumatic circuit for a civil engineering construction machine comprising an air compressor driven by a prime mover, a tank for storing compressed air discharged from the air compressor, and a drain valve connected to the tank. A pneumatic circuit for civil engineering and construction machinery, characterized in that it comprises a detection means for detecting stoppage of the prime mover, and a control means for opening the drain valve for a predetermined period of time from the time when the stoppage of the prime mover is detected by the detection means. 2. The pneumatic circuit for civil engineering and construction machinery according to claim 1, wherein the detection means detects whether a key switch of the prime mover is turned off.