JPH0147642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a hydraulic circuit for driving a hydraulic motor connected to a large inertial load.

[Conventional technology]

FIG. 1 is a diagram showing a conventional hydraulic circuit for driving a hydraulic motor connected to a large inertial load. In the figure, 4 is a hydraulic pump, 1 is a hydraulic motor connected to a large inertial load, 2 is a manual directional switching valve provided between the hydraulic pump 4 and the hydraulic motor 1, and 3a and 3b are directional switching valves. 2 and the hydraulic motor 1; 5, the hydraulic pump 4 and the directional control valve 2; 7, a tank; 6, the directional control valve 2 and the tank 7; 9 is a connecting pipe connecting the suction and exhaust pipe 3a and the suction and exhaust pipe 3b;
8a and 8b are the first and second pipes provided in the connection pipe 9.
The check valves 8a and 8b block the flow from the center of the connecting pipe 9 to the suction and exhaust pipes 3a and 3b. Reference numeral 11 denotes a connecting pipe line that connects the suction/discharge pipe line 3a and the suction/discharge pipe line 3b, and the connecting pipe line 11 is connected to the side closer to the hydraulic motor 1 than the connecting pipe line 9 is. 12
The check valves a and 12b are third and fourth check valves provided in the conduit 11, and the check valves 12a and 12b block the flow from the suction and discharge conduits 3a and 3b to the center of the connecting conduit 11. 10 is a relief valve whose inlet port is connected to the center of the connection pipe 9 and whose outlet port is connected to the center of the connection pipe 11;
A tank 7 is connected to the outlet port of 0.

In this hydraulic circuit, when the directional control valve 2 is switched to the operating position and the hydraulic motor 1 is started, the hydraulic motor 1 is not easily accelerated due to a large inertial load, and for example, the pressure in the suction and exhaust pipe 3a increases. When the pressure of the suction/discharge pipe 3a becomes higher than the set pressure of the relief valve 10, the excess pressure oil supplied from the hydraulic pump 4 is removed from the check valve 8a and the relief valve 1.
0 to the suction/discharge pipe 3b and the tank 7. Then, when the hydraulic motor 1 is accelerated and the rotational speed of the hydraulic motor 1 approaches the rotational speed corresponding to the amount of oil supplied from the hydraulic pump 4, the pressure in the suction/discharge pipe 3a becomes lower than the set pressure of the relief valve 10. , the release of oil from the relief valve 10 is stopped. next,
Return the directional control valve 2 to the neutral position and turn the hydraulic motor 1
When trying to stop the hydraulic motor 1, which continues to rotate due to the inertial force of the inertial load, the suction/discharge pipe 3b
However, since the suction and discharge pipe 3b is blocked by the directional switching valve 2, the pressure in the suction and discharge pipe 3b increases, and when the pressure in the suction and discharge pipe 3b becomes higher than the set pressure of the relief valve 10. The oil discharged from the hydraulic motor 1 is discharged into the suction/discharge pipe 3a and the tank 7 via the check valve 8b and the relief valve 10.
Then, the hydraulic motor 1 is decelerated, and the hydraulic motor 1
When the rotational speed of the valve 10 decreases, the pressure in the suction/discharge pipe 3b becomes lower than the set pressure of the relief valve 10, and the release of oil from the relief valve 10 stops. As a result, the pressure at the center of the connecting pipe 9 changes over time as shown in FIG. 2A, and the driving acceleration and braking acceleration of the hydraulic motor 1 become as shown in FIG. 2B.

[Problem to be solved by the invention]

However, in such a hydraulic circuit, the pressure in the center of the connecting pipe 9 rapidly increases from 0 to the set pressure of the relief valve 10 during acceleration and deceleration, resulting in an increase in surge pressure, which causes damage to the hydraulic equipment. The life of the hydraulic motor 1 will be shortened, failures will increase, and the absolute value of the acceleration of the hydraulic motor 1 during acceleration and deceleration will increase from 0 to the maximum value in a short period of time, so the acceleration of the hydraulic motor 1 during acceleration and deceleration will Since the change in speed is large, the shock during acceleration and deceleration is large.

This invention was made to solve the above-mentioned problems, and the surge pressure during acceleration and deceleration is small.
The purpose is to provide a hydraulic circuit with small shock during acceleration and deceleration.

[Means to solve the problem]

In order to achieve this object, the first invention includes a hydraulic pump, a hydraulic motor connected to a large inertial load, and a connecting pipe connecting both suction and exhaust pipes connected to both ports of the hydraulic motor, In the hydraulic circuit, the hydraulic circuit includes first and second check valves that are provided in the connecting pipe and prevent flow from the central part of the connecting pipe to both the suction and exhaust pipes, and the outlet port is connected to the tank side. a low-pressure relief valve, a high-pressure relief valve whose outlet port is connected to the tank and whose set pressure is higher than the set pressure of the low-pressure relief valve, and outlet ports of the low-pressure relief valve and the high-pressure relief valve. When the differential pressure across the throttle is smaller than a predetermined value, the central part of the connecting pipe is connected to the inlet port of the low-pressure side relief valve, and the differential pressure across the throttle is lower than the predetermined value. When the pipe is large, a pilot-operated directional control valve is provided to connect the central portion of the connecting pipe and the inlet port of the high-pressure side relief valve.

Further, in the second invention, a hydraulic pump, a hydraulic motor connected to a large inertial load, a connecting pipe connecting both suction and exhaust pipes connected to both ports of the hydraulic motor, and a connecting pipe connecting the connecting pipe A low-pressure side relief valve having an outlet port connected to a tank side in a hydraulic circuit having first and second check valves that are provided and prevent flow from a central portion of the connecting pipe line to both the suction and exhaust pipe lines. , a high-pressure side relief valve whose outlet port is connected to the tank side and whose set pressure is higher than the set pressure of the low-pressure side relief valve, and a throttle connected to the outlet ports of the low-pressure side relief valve and the high-pressure side relief valve. When the differential pressure across the throttle is smaller than a predetermined value, the position is A, which connects the central part of the connecting pipe and the inlet port of the low-pressure side relief valve, and when the differential pressure across the throttle is larger than the predetermined value. B that connects the central part of the connecting pipe and the inlet port of the high pressure side relief valve.
a pilot-operated directional valve serving as a pilot-operated directional valve; a pilot conduit connecting the downstream side of the throttle to the pilot port of the pilot-operated directional valve; and the upstream side of the throttle and the pilot port of the pilot-operated directional valve. Directional switching speed adjusting means is provided on at least one of the pilot conduits connecting the port and reduces the switching speed of the pilot operated directional switching valve from the A position to the B position.

[Effect]

In the hydraulic circuit of the first invention, during acceleration,
During deceleration, the pressure in the center of the connecting pipe increases from 0 to the set pressure of the low-pressure side relief valve, and after the low-pressure side relief valve opens, the pilot operated directional control valve changes from position A with a time delay. Switching to position B, the pressure in the center of the connecting pipe increases from the set pressure of the low-pressure side relief valve to the set pressure of the high-pressure side relief valve. Also, the absolute value of the acceleration of the hydraulic motor during acceleration and deceleration increases from 0 to an intermediate value, holds the intermediate value until the pilot operated directional control valve switches from position A to position B, and then increases to the intermediate value. increases from to the highest value.

In addition, in the hydraulic circuit of the second invention, the time during which the pressure in the center of the connecting pipe is maintained at the set pressure of the low-pressure side relief valve and the time during which the absolute value of the acceleration of the hydraulic motor is maintained at an intermediate value are long. Become.

〔Example〕

FIG. 3 is a diagram showing a hydraulic circuit according to the present invention. In the figure, 10a is a low pressure side relief valve whose outlet port is connected to the center of the connecting pipe 11;
0b is a high-pressure side relief valve whose outlet port is connected to the center of the connecting pipe 11, and the high-pressure side relief valve 1
The set pressure of 0b is higher than the set pressure of the low pressure side relief valve 10b. 14 is a low pressure side relief valve 10
a, a throttle provided between the outlet port of the high pressure side relief valve 10b and the center of the connecting pipe 11, 13;
When the differential pressure across the throttle 14 is smaller than a predetermined value, the central part of the connecting pipe 9 and the low pressure side relief valve 10a
The A position connects the inlet port of the
When the differential pressure across the valve 4 is larger than a predetermined value, the pilot-operated directional control valve 15a assumes position B, which connects the center of the connecting pipe 9 and the inlet port of the high-pressure side relief valve 10b; 15b is a pilot pipe connecting the upstream side of the throttle 14 and the pilot port of the directional control valve 13; 16a and 16b are pilot pipes 15;
The throttle check valves 16a and 16b constitute directional switching speed adjusting means for reducing the switching speed of the directional switching valve 13 from the A position to the B position.

In this hydraulic circuit, when the directional control valve 2 is switched to the operating position and the hydraulic motor 1 is started, the hydraulic motor 1 is not easily accelerated due to a large inertial load, and for example, the pressure in the suction and exhaust pipe 3a increases. However, initially the directional control valve 13 is in the A position,
When the pressure in the suction/discharge pipe 3a becomes higher than the set pressure of the low-pressure side relief valve 10a, excess pressure oil supplied from the hydraulic pump 4 passes through the check valve 8a and the low-pressure side relief valve 10a to the suction/discharge pipe 3b, tank 7
While the rotational speed of the hydraulic motor 1 is low, the flow rate passing through the throttle 14 is large and the differential pressure across the throttle 14 becomes larger than a predetermined value, so the directional control valve 13 is switched to the B position. In this case, since the throttle check valves 16a, 16b are provided in the pilot lines 15a, 15b, the switching speed of the directional control valve 13 from the A position to the B position is slow. When the pressure in the suction/discharge pipe 3a becomes higher than the set pressure of the high pressure side relief valve 10b, the excess pressure oil supplied from the hydraulic pump 4 is removed from the check valve 8.
aa, is discharged to the suction/discharge pipe 3b and the tank 7 via the high pressure side relief valve 10b. Then, when the hydraulic motor 1 is accelerated and the rotational speed of the hydraulic motor 1 increases, the differential pressure across the throttle 14 becomes smaller than a predetermined value, so the directional control valve 13 is switched to the A position, and the suction/discharge pipe 3a pressure also decreases. Next, when the directional control valve 2 is returned to the neutral position and an attempt is made to stop the hydraulic motor 1, oil is discharged from the hydraulic motor 1, which continues to rotate due to the inertial force of the inertial load, into the suction/discharge pipe 3b. Since the suction and exhaust pipe line 3b is blocked by the directional switching valve 2, the pressure of the suction and discharge line 3b increases, and when the pressure of the suction and discharge line 3b becomes higher than the set pressure of the low pressure side relief valve 10a, the hydraulic motor 1 The discharged oil is discharged into the suction/discharge pipe 3a and the tank 7 via the check valve 8b and the low-pressure side relief valve 10a, and while the rotation speed of the hydraulic motor 1 is high, the flow rate passing through the throttle 14 is large, and the 1
4 becomes larger than a predetermined value, the directional control valve 13 is switched to the B position, and the suction/discharge pipe 3
When the pressure of b becomes higher than the set pressure of the high-pressure side relief valve 10b, the oil discharged from the hydraulic motor 1 is released into the suction/discharge pipe 3a and the tank 7 via the check valve 8b and the high-pressure side relief valve 10b. . Then, when the hydraulic motor 1 is decelerated and the rotational speed of the hydraulic motor 1 becomes smaller, the differential pressure across the throttle 14 becomes smaller than a predetermined value, so the directional control valve 13 is
position, and the pressure in the suction and exhaust pipe line 3b also decreases. As a result, the temporal change in pressure at the center of the connecting pipe 9 becomes as shown in FIG. 4A, and the driving acceleration and braking acceleration of the hydraulic motor 1 become as shown in FIG. 4B.

In this way, in this hydraulic circuit, the pressure in the center of the connecting pipe 9 during acceleration and deceleration increases from 0 to the set pressure of the low pressure side relief valve 10a,
After the low pressure side relief valve 10a is opened until the directional control valve 13 is switched from the A position to the B position,
The pressure in the center of the connecting pipe 9 is low pressure side relief valve 1
After the set pressure of 0a is maintained, the surge pressure is increased to the set pressure of the high-pressure side relief valve 10b, so the surge pressure becomes small. Also, the absolute value of the acceleration of the hydraulic motor 1 during acceleration and deceleration increases from 0 to an intermediate value, maintains the intermediate value until the directional control valve 13 switches from the A position to the B position, and then reaches the maximum value. Since the change in the acceleration of the hydraulic motor 1 during acceleration and deceleration is small, the shock during acceleration and deceleration is small.

FIG. 5 is a diagram showing another hydraulic circuit according to the present invention. In the figure, 17a and 17b are accumulators connected to the pilot port side of the directional switching valve 13 of the throttle check valves 16a and 16b, and the throttle check valves 16a and 16b and the accumulators 17a and 17b constitute a directional switching speed adjusting means. has been done.

In this hydraulic circuit, A of the directional control valve 13 is
The switching speed from the position to the B position can be made smaller.

In the above embodiment, the pilot line 15a and the pilot line 15b are provided with a direction switching speed adjusting means, but the valves generally have a delay in operation due to the compressibility of the oil, the inertia of the oil, the valve, etc. Therefore, even if the pilot pipe 15a and the pilot pipe 15b are not provided with direction switching speed adjusting means,
After a time delay after the low-pressure side relief valve 10a opens, the pilot-operated directional control valve switches from the A position to the B position, and the pressure in the center of the connecting pipe 9 reaches the set pressure of the low-pressure side relief valve 10a. Since the pressure increases from 1 to the set pressure of the high-pressure side relief valve 10b, it is not necessarily necessary to provide a direction switching speed adjustment means. Further, in the above embodiment, the pilot pipe line 15a and the pilot pipe line 15b are provided with direction switching speed adjusting means, but the pilot line 1
Even when the directional switching speed adjusting means is provided only in the pilot pipe 15b, the switching speed of the directional switching valve 13 from the A position to the B position can be reduced. Since the switching speed of the directional switching valve 13 from the A position to the B position can be made small even in such a case, it is sufficient to provide a directional switching speed adjusting means in at least one of the pilot conduits 15a and 15b. Furthermore, in the above-mentioned embodiment, the connection pipe line 11, which is an oil supply means for supplying oil to the suction side of the hydraulic motor 1, is provided, but if the hydraulic motor 1 is resistant to cavitation, the oil supply means may not be provided. good.

〔Effect of the invention〕

As explained above, in the hydraulic circuit according to the first invention, the pressure in the center of the connecting pipe increases from 0 to the set pressure of the low-pressure side relief valve during acceleration and deceleration, and the low-pressure side relief valve closes. Then, with a time delay, the pilot-operated directional valve switches from position A to position B, and the pressure in the center of the connecting pipe increases from the set pressure of the low-pressure side relief valve to the set pressure of the high-pressure side relief valve. Because it rises, when accelerating,
Since the surge pressure during deceleration is reduced, the life of hydraulic equipment is extended and failures are reduced. Also, the absolute value of the acceleration of the hydraulic motor during acceleration and deceleration increases from 0 to an intermediate value, holds the intermediate value until the pilot operated directional control valve switches from position A to position B, and then increases to the intermediate value. Since the change in the acceleration of the hydraulic motor during acceleration and deceleration is small, the shock during acceleration and deceleration is small.

Furthermore, in the hydraulic circuit according to the second aspect of the invention, the pressure in the center of the connecting pipe is maintained at the set pressure of the low-pressure side relief valve for a long time.
Since the surge pressure during deceleration becomes smaller and the time during which the absolute value of the acceleration of the hydraulic motor is held at an intermediate value becomes longer, changes in the acceleration of the hydraulic motor during acceleration and deceleration become smaller.

As described above, the effects of this invention are remarkable.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional hydraulic circuit, FIG. 2 is a graph for explaining the operation of the hydraulic circuit shown in FIG. 1, FIG. 3 is a diagram showing a hydraulic circuit according to the present invention, and FIG. is a graph for explaining the operation of the hydraulic circuit shown in FIG. 3, and FIG. 5 is a diagram showing another hydraulic circuit according to the present invention. 1... Hydraulic motor, 2... Directional switching valve, 3a,
3b...Suction/exhaust pipe line, 4...Hydraulic pump, 8a...
First check valve, 8b... second check valve,
9... Connection pipe line, 10a... Low pressure side relief valve,
10b... High pressure side relief valve, 11... Connection pipe, 12a... Third check valve, 12b... Fourth check valve, 13... Pilot operated directional valve, 14... Throttle, 15a, 15b... Pilot pipe line, 16a, 16b... Throttle check valve, 17a, 17b... Accumulator.

Claims (1)

[Claims] 1. A hydraulic pump, a hydraulic motor connected to a large inertial load, a connecting pipe connecting both suction and exhaust pipes connected to both ports of the hydraulic motor, and a connecting pipe provided in the connecting pipe. In the hydraulic circuit, the hydraulic circuit includes first and second check valves that prevent flow from the central portion of the connecting pipe to both the suction and exhaust pipes; , a high-pressure side relief valve whose outlet port is connected to the tank side and whose set pressure is higher than the set pressure of the low-pressure side relief valve, and a throttle connected to the outlet port of the low-pressure side relief valve and the high-pressure side relief valve. , when the differential pressure across the throttle is smaller than a predetermined value, the center of the connecting pipe is connected to the inlet port of the low-pressure side relief valve, and when the differential pressure across the throttle is larger than the predetermined value, the connecting pipe is connected. A hydraulic circuit comprising: a pilot-operated directional control valve connecting a central portion of the valve and an inlet port of the high-pressure side relief valve. 2. A hydraulic pump, a hydraulic motor connected to a large inertial load, a connecting pipe connecting both suction and exhaust pipes connected to both ports of the hydraulic motor, and a connecting pipe provided in the connecting pipe and the connecting pipe. In the hydraulic circuit, the hydraulic circuit has first and second check valves that prevent flow from the central part of the pump to both the suction and exhaust pipes, a low pressure side relief valve whose outlet port is connected to the tank side, and a low pressure side relief valve whose outlet port is connected to the tank side. a high-pressure side relief valve connected to and whose set pressure is higher than the set pressure of the low-pressure side relief valve, a throttle connected to the outlet port of the low-pressure side relief valve and the high-pressure side relief valve, and a difference between the front and back of the said throttle. When the pressure is lower than a predetermined value, the position is A, which connects the central part of the connecting pipe and the inlet port of the low-pressure side relief valve, and when the differential pressure across the throttle is larger than the predetermined value, the central part of the connecting pipe is connected. a pilot-operated directional control valve at position B that connects the inlet port of the high-pressure side relief valve; and a pilot pipe line that connects the downstream side of the throttle and the pilot port of the pilot-operated directional control valve. Provided in at least one of the pilot pipes connecting the upstream side of the throttle and the pilot port of the pilot-operated directional control valve, and reducing the switching speed of the pilot-operated directional control valve from the A position to the B position. A hydraulic circuit characterized in that it comprises a direction switching speed adjustment means. 3. The hydraulic circuit according to claim 2, wherein a throttle check valve is provided in the pilot conduit as the direction switching speed adjusting means. 4. The hydraulic circuit according to claim 3, wherein an accumulator is connected between the pilot port of the pilot-operated directional control valve and the throttle check valve.