JPH0539202Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a self-diagnosis device that detects an abnormal drop in gas pressure in an accumulator.

[Conventional technology]

The gas in the accumulator is mixed with the hydraulic oil and degraded over time due to gas molecules permeating through the rubber membrane in the Prada type accumulator, or leaking from the piston ring seal in the piston type accumulator. When the gas pressure in the accumulator decreases in this manner, filling the accumulator with hydraulic oil to bring it to a predetermined pressure requires a larger amount of oil than normal, and the filling time becomes longer.

To explain this, from the Boyle-Charles formula, P ₁ ⁿ = P ₂ ⁿ V ₂ ⁿ = P ₁ ÷ P ₂ × V ₁ ⁿ ...(1) n: Polytropic exponent P ₁ ; Accumulator filling normal gas pressure V ₁ ; Initial gas volume P ₂ ; Maximum gas compression pressure V ₂ ; Gas volume at P ₂ For normal gas pressure, P ₁ = 100Kg/cm ² and P ₂ = 150Kg/cm ² , then (1)
From the formula, ₁₀₀ V ₂ ⁿ = 100÷150×V ₁ ⁿ ≒0.67V ₁ ⁿ ……(2) In case of gas pressure drop, P ₁ = 90Kg/cm ² , P ₂ = 150Kg/cm ² ∴90V ₂ ⁿ = _{90 ÷} ^{150 ​} Requires.

Here, if the amount of oil in the accumulator at a given gas pressure (e.g. 150 Kg/cm ² ) is V ₀ , then ₁₀₀ V ₀ = V ₁ ⁿ −100V ₂ ⁿ = V ₁ ⁿ −0.67V when the gas pressure is 100 Kg/cm ² ₁ ⁿ =0.33V ₁ ⁿ ……(4) Gas pressure 90Kg/cm ^2:90 _{V 0 =} V ₁ ⁿ −90V ₂ ⁿ =V ₁ ⁿ −0.6V ₁ ⁿ =0.4V ₁ ⁿ ……(5) Now , if the discharge rate of the hydraulic pump is Q/sec, then the theoretical accumulator filling time T ₀ is: Gas pressure 100Kg/cm ² : ₁₀₀ T ₀ = 100V ₀ /Q = 0.33V ₁ ⁿ /Qsec Gas pressure 90Kg/cm ^2:00 ₉₀ T ₀ = 90V ₀ /Q = 0.40V ₁ ⁿ /Qsec Therefore, the filling time is 0.40/0.33=1.2 times longer than the normal time.

In addition, the accumulator filling time when the gas pressure decreases
T ₀ ' is expressed by the following general formula (6).

T ₀ ′=T ₀ (P ₂ −P ₁ ′)/(P ₂ −P ₁ ) ……(6) P ₁ ′;Accumulator reduced gas pressure When the gas pressure inside the accumulator decreases, the time to fill the hydraulic oil increases. As mentioned above, this causes the following problems.

The load operation time of the electric motor that drives the hydraulic pump becomes longer, and power consumption increases.

If the actuator operated by the accumulator is at high speed or high cycle, the accumulator will not be filled with hydraulic oil in time.
There may be a constant pump load.

In the worst case, the gas pressure may be so low that a predetermined pressure cannot be obtained even if the accumulator is filled with hydraulic oil.

For this reason, conventionally, a pressure gauge is attached to the gas volume of the accumulator to periodically visually check the gas pressure when the oil pressure is 0 kg/cm ² .

[The problem that the idea aims to solve]

However, in the case of an injection metering machine, for example, the electric motor for driving the hydraulic pump is operated unattended by a timer or the like, and after the pressure in the accumulator has been raised to a predetermined pressure, a worker comes and starts operation. However, in such cases there is no opportunity to visually check the pressure gauge. Furthermore, since gas pressure drops in the accumulator do not occur very often, it is easy to forget to visually check the pressure gauge, and the drop in gas pressure is often noticed only after the above-mentioned problem occurs.

The present invention provides a gas pressure drop self-diagnosis device for an accumulator that can quickly detect a drop in gas pressure at the initial stage of operation of a driving electric motor of a hydraulic pump without requiring regular inspections of the gas pressure by a worker. With the goal.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a starting switch for an electric motor that drives a hydraulic pump that supplies hydraulic oil to an accumulator, and a starting switch that is turned on when the hydraulic oil pressure in the accumulator is approximately zero. A time measuring device that starts measuring time at the same time as the electric motor starts, compares a preset set time with the time measured by the time measuring device, and activates an alarm when the measured time exceeds the set time. A measurement time comparison/judgment device detects the gas pressure in the accumulator, and the oil supply to the accumulator is started by the operation of a hydraulic pump by an electric motor. The structure includes a pressure gauge that stops the time measuring device when a predetermined pressure is reached.

[Effect]

Set a predetermined time on the measurement time comparison and judgment device,
When you turn on the starting switch and start the electric motor,
The hydraulic pump is driven and starts filling the accumulator with hydraulic oil. At the same time, the time measuring device operates and starts measuring time. The measurement time comparison and judgment device compares the measurement time of the time measurement device with a preset time set in itself, and determines that the gas pressure has decreased if the measurement time of the time measurement device exceeds the set time. Activate the alarm. Therefore, there is no need for the operator to take the trouble to check the gas pressure, and the above-mentioned problems caused by a drop in gas pressure can be avoided.

If the gas pressure in the accumulator reaches a predetermined pressure before the time measured by the time measuring device has elapsed before the set time, the pressure gauge stops the time measuring device. Therefore, the alarm will not activate.

[Embodiment] Figures 1 and 2 show an embodiment of the present invention applied to an accumulator of an injection metering machine. It is a hydraulic pump driven. The discharge port of this hydraulic pump 2 is connected to an accumulator 4 through a pipe line 3, and a check valve 5 is provided in the middle of the pipe line 3 in a direction that allows the flow of hydraulic oil to the accumulator 4. It is being Further, a safety valve 7 is connected to the pipe line 3 on the upstream side of the check valve 5 via a pipe line 6.

The safety valve 7 is of a balanced piston type, and has a drain port connected to a tank 9 via a drain line 8, and a vent port connected to a solenoid valve 11 via a pilot line 10.

The solenoid valve 11 has 2 ports with 4 ports A, B, P, and T.
When the solenoid 11a is in the neutral position, all ports are open, and when the solenoid 11a is energized, the P and A ports and the B and T ports are connected. And the solenoid valve 11
, the P port is connected to the pilot conduit 10,
The T port connects to the drain pipe 8 via the tank pipe 12.
is connected to. Further, plugs 11b and 11c are provided at the A and B ports of the solenoid valve 11, respectively, to prevent hydraulic oil from flowing out from the A and B ports.

Further, a tank line 13 connected to a tank 9 is connected to the line 3 on the downstream side of the check valve 5, and a stop valve 14 is provided in the middle of the tank line 13. . Furthermore, the check valve 5
A pressure gauge 15 is provided in the pipeline 3 on the downstream side. In addition, in the pipe line 3 downstream of the check valve 5,
A hydraulic cylinder 17 is connected via an electromagnetic switching valve 16, and other electromagnetic switching valves, actuators, etc. (not shown) are also provided, and the injection molding machine is controlled by the pressure oil stored in the accumulator 4. Various operations are being performed in devices, mold clamping devices, etc. A pressure gauge 18 is attached to the accumulator 4 to detect gas pressure.

The electric motor 1, electromagnetic valve 11, etc. shown in FIG. 1 are controlled by a control circuit shown in FIG. That is, numerals 21 and 22 are busbars of the control power supply,
These busbars 21 and 22 are connected from the busbar 21 side to a start switch ST with an a contact, a stop switch STP with a b contact, a b contact _R1 of a relay R, and an electric motor 1.
Electromagnetic contactors MC are connected in series. In addition, the starting switch ST
A contact mc ₁ of the magnetic contactor MC is connected in parallel to ST. Further, from the bus bar 21 side, the a contact mc ₂ of the electromagnetic contactor MC is connected to the bus bars 21 and 22,
B contact 18b of pressure gauge 18 and electromagnetic switching valve 11
Solenoids 11a are connected in series, and a time measuring device 23 is connected in parallel to the solenoid 11a.

Furthermore, a measurement time comparison and judgment device 24 and a relay R are connected in series to the busbars 21 and 22 from the busbar 21 side. In addition, the busbars 21, 2
2, a contact _R2 of the relay R and a buzzer (alarm) BZ are connected in series from the bus bar 21 side, and a warning lamp (alarm) LMP is connected in parallel to the buzzer BZ.

Here, the time measuring device 23 measures the time after the electric motor 1 is activated, and the measured time comparing and determining device 24 compares a preset time and the measured time of the time measuring device 23. , when the measurement time has passed the set time, the relay R is turned on and the relay R is energized. The time set in the measurement time comparison and judgment device 24 is usually determined by experiment, calculation, or the like.

Next, the operation of the gas pressure drop self-diagnosis device for an accumulator according to the present invention constructed as described above will be explained.

In the injection molding machine, at the end of the previous molding operation, the pressure of the hydraulic oil in the accumulator 4 is released to the atmosphere by the stop valve 14 and has become almost zero. In this state, the stop valve 14 is closed.

In the above state, when the starting switch ST is turned on, current flows through the electromagnetic contactor MC and the electromagnetic contactor MC is turned on. Then, the a contact mc ₁ of the relay MC turns on, and the current flowing to the electromagnetic contactor MC is maintained,
Electric power is supplied to the electric motor 1 and the electric motor 1 rotates. Therefore, the hydraulic pump 2 is driven to rotate and starts feeding oil. At the same time, the a contact mc ₂ of the magnetic contactor MC also turns on, so the solenoid 11a
And current flows through the time measuring device 23. For this reason, the time measuring device 23 starts measuring time, and the solenoid valve 11 is switched, and the solenoid valve 1
The P port and A port, and the B port and T port of No. 1 are connected. Then, the flow of hydraulic oil from the vent port of the safety valve 7 to the tank 9 is blocked, and the safety valve 7 is set at a predetermined set pressure. Therefore, the hydraulic oil discharged from the hydraulic pump 2 flows into the accumulator 4 through the check piece 5 without flowing out from the safety valve 7 into the tank 9, and the pressure inside the accumulator 4 is gradually increased.

The measurement time comparison and judgment device 24 is the time measurement device 23
At the same time that the time measuring device 23 starts measuring, it starts comparing the measured time of the time measuring device 23 with the time set in advance for itself. When the gas pressure in the accumulator 4 is normal and the time measured by the time measuring device 23 does not reach the set time, when the gas pressure in the accumulator 4 reaches a predetermined pressure set by the pressure gauge 18, the pressure gauge 18 The B contact 1 of the pressure gauge 18 is turned ON.
8b opens. Therefore, time measurement by the time measuring device 23 is interrupted, and the solenoid 11a of the solenoid valve 11 is turned off, and the solenoid 11a of the solenoid valve 11 is turned off.
1 is switched to the neutral position, and each port of A, B, P, and T becomes connected. Then, the vent port of the safety valve 7 is brought into communication with the tank 9, and the set pressure of the safety valve 7 becomes approximately zero. Therefore, the discharge pressure of the hydraulic pump 2 rapidly decreases to the unloading pressure caused by the passage resistance of the pipeline and the safety valve 7. However, the pressure inside the accumulator 4 is blocked by the check valve 5 and does not escape from the safety valve 7 to the tank 9, and is maintained at a high pressure.

Furthermore, if the gas pressure in the accumulator 4 is abnormally low and it takes time for the pressure gauge 18 to turn on, and the time set by the measurement time comparison and judgment device 24 is reached, the measurement time comparison and judgment device 24 turns on. , relay R is energized, so relay R
The B contact _r1 opens, the magnetic contactor MC turns OFF, and the motor 1 stops, and the A contact _R2 closes, the buzzer BZ sounds, and the alarm sensor LMP lights up.

Note that the pressure gauge 15 provided in the pipe line 3 indicates the same pressure as the pressure gauge 18 of the accumulator 18 after the start of filling the accumulator 4 with hydraulic oil, so this pressure gauge 15 moves the b contact 18b. You can do it like this. Further, if there is no need to automatically stop the electric motor 1 when a decrease in gas pressure is detected, the b contact _r1 of the relay R is omitted. The hydraulic pump 2 may be provided with an abnormality detector 25 that detects abnormalities such as poor suction of the hydraulic pump 2 based on the flow rate of hydraulic oil, the load current of the electric motor 1, and the like.

[Effect of idea]

As explained above, the accumulator gas pressure drop self-diagnosis device according to the present invention detects a starting switch for the electric motor that drives the hydraulic pump that supplies hydraulic oil to the accumulator, and a state in which the hydraulic oil pressure in the accumulator is approximately zero. When the starting switch is turned on and the motor starts, the time measuring device starts measuring the time, and the preset time is compared with the time measured by the time measuring device, and the measured time is determined as the set time. A measurement time comparison and judgment device activates an alarm when the time has elapsed, and a gas pressure in the accumulator is detected, and a hydraulic pump is activated by an electric motor to start supplying oil to the accumulator, so that the time measured by the time measurement device does not exceed the set time. Since the structure is equipped with a pressure gauge that stops the time measuring device when the gas pressure in the accumulator reaches a predetermined pressure, the drop in gas pressure in the accumulator can be detected without the need for visual confirmation by an operator. can be known reliably and automatically. Therefore, the above-mentioned troubles do not occur, and the accumulator can always be operated normally and various operations can be carried out smoothly.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a hydraulic circuit diagram of a gas pressure drop self-diagnosis device for an accumulator for an injection molding machine according to the present invention, and FIG. 2 is a control circuit diagram thereof. 1...Electric motor, 2...Hydraulic pump, 4...Accumulator, 18...Pressure gauge, 23...Time measuring device, 24...Measuring time comparison/judgment device, ST...
Starting switch, BZ...buzzer (alarm),
LMP...Warning lamp (alarm device).

Claims (1)

[Scope of utility model registration request] A starting switch for the electric motor that drives the hydraulic pump that sends hydraulic oil to the accumulator, and when the hydraulic oil pressure in the accumulator is almost zero, the starting switch is turned on and the electric motor starts, and at the same time, time measurement begins. a time measuring device; a measured time comparison and judgment device that compares a preset set time with the measured time of the time measuring device and activates an alarm when the measured time passes the set time;
The gas pressure in the accumulator is detected, and when the oil supply to the accumulator is started by the operation of the hydraulic pump by the electric motor and the gas pressure in the accumulator reaches a predetermined pressure before the time measured by the time measuring device has elapsed, the above-mentioned time has elapsed. A gas pressure drop self-diagnosis device for an accumulator, characterized by comprising a pressure gauge for stopping a measuring device.