JPS58193901A - Capacity compensation device for closed hydraulic circuit - Google Patents

Abstract

PURPOSE:To get a large effective capacity with a small pressure difference by a method wherein a pressurizied tank is provided with an oil chamber and an air chamber which are separated by a flexible membrane, and the air chamber is provided with a neumatic pressure supplying source and means for setting air discharging pressure set to such a higher pressure than said predetermined pressure through the pressure setting means. CONSTITUTION:A pressurized tank 15 is divided into an oil chamber A and an air chamber B by a flexible membrane 16, and guards 17 and 18 are arranged in each of the chambers so as to define the maximum deformation degree of the spacer film 16. To the air chamber B is connected a safety valve 19 and its setting pressure is lower than the set pressure in the relief valve 11. The air chamber B is connected to a compressor 23 through an air tank 22, the set pressure in a pressure relief valve 21 in the midway thereof is lower than the predetermined pressure in the safety valve 19. In the air tank 22 is arranged a safety valve 24.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacity compensation device for a hydraulic closed circuit that compensates for excess or deficiency of hydraulic fluid occurring in the hydraulic closed circuit.

Generally, a single rond cylinder used as an actuator in a hydraulic circuit has different pressure receiving areas on the rond side and the head side, so if it is connected to a hydraulic closed circuit and driven equally to the rond side or head @, the volume of that circuit will be changes.

In order to compensate for the excess or deficiency of hydraulic fluid due to this volume change, conventional methods have been adopted such as providing a hydraulic motor or a hydraulic cylinder in the circuit, or connecting a separate accumulator. However, since hydraulic motors and hydraulic cylinders are expensive, accumulators are usually used.

FIG. 1 is a diagram showing a conventional hydraulic closed circuit in which an accumulator is connected to the hydraulic closed circuit.

In FIG. 1, 1 is a variable displacement pump, and 2 is a single rod cylinder. 3 is a circuit for connecting the variable displacement pump 1 and the single rod cylinder 20 Rondo side, 4 is the variable displacement pump 1
This is a circuit that connects the head side of the single rod cylinder 2. 5 is a switching valve disposed between circuits 3 and 4, and 06 is a flushing valve for supplying pressure oil from the variable displacement pump 1 to the single cylinder cylinder 2. This is a low pressure selection valve that connects the low pressure side circuit and the charge circuit 14. l.

8. 9 and 30 are check valves, which are connected to a charge pump and a lashing valve 7, which will be described later.If the flow rate is insufficient than K due to a change in volume or leakage of the single cylinder cylinder 2, the check valves 8 and 30 The stop valves 8 and 30, which are supplied via the stop valves 7.8.9 and 30v to the circuit 3 or 4, are primarily connected to the variable displacement pump 1.
Also, the check valve 1 is used as a king to supply the single rod cylinder 2.

10 is a charge pump, and when there is a shortage of Ci in circuit 3 or 41 as described above, check valves 1°8, 9
, 30.7 supplies pressure oil to the circuit 3 or 4 via the lashing valve 6 and the charging circuit 14.

11 is a +7 +J-7 valve, and a constant pressure is set, and when the pressure in circuit 14 exceeds the set pressure, circuit 1
This is to return the pressure oil from step 4 to the tank. Reference numeral 12 indicates a tank, to which one side of the charge bong 110 and the relief valve 11 are connected.

Reference numeral 13 denotes a 7-cumulator of a type such as a bladder type that encloses gas. The accumulator 13 accumulates pressurized oil having excess energy generated in the circuits 3 and 4, and compensates for insufficient flow rate due to volume change or leakage of the single cylinder cylinder 2 described above. The accumulator 13 supplies the accumulated pressure oil to the circuits 3 and 4 via the check valves 1 and 30 and the flushing valve 6, and
The accumulation of pressure oil takes place from the charge pump 10 via the check valve 9 or from the circuits 3 and 4 via the 7 lashing valve 6 and the charge circuit 14.

In such a hydraulic closed circuit, when a flow shortage occurs in the circuit 3.4, the charge pump 10 supplies pressure oil via the check valve 9, the charge circuit 14, the check valves 7 and 30, and the flushing valve 6. However, since the capacity of the charge pump 10 is small and not sufficient to compensate for the insufficient flow rate, the accumulator 13 is also connected to the charge (b) path 14°, the check valves I, 30 and 7, and the lashing valve 6. Supply pressure oil through. - When the pressure difference between circuits 3 and 4 increases, the pressure oil passes through the 7 lashing valve 6 and the charge circuit 141 and is accumulated in the accumulator 13, and the pressure oil from the charge pump 10 also passes through the check valve 9. The accumulator 13KmF is overturned.

Pressure on the low side of circuits 3-4 and therefore charge circuit 1
4 exceeds the relief valve 110 set pressure, the pressure oil is returned to the tank 12 through the relief valve 11, so that +
Pressure oil is not accumulated in the accumulator 13 at a pressure equal to or higher than the 7+7-7 valve 110 set pressure.

In this way, the accumulator 13 repeatedly accumulates and supplies pressure oil during closed circuit operation, but in order for the accumulator 13 to perform its operation sufficiently, the accumulator 13 itself,
It is necessary to have a large effective area. By the way, K for which the accumulator 13 has a large effective answer t# is
#! As shown in Figure 2, either a large pressure difference must be set or the volume of the container of the accumulator itself must be increased.

FIG. 2 shows a valley test-pressure curve of the gas enclosed in an accumulator of 13 yen, with the horizontal axis representing the volume (2) and the vertical axis representing the pressure P. This curve follows the well-known Pv-K (K is a constant) (however, the temperature is constant). In the figure, Pl is the set pressure of the relief valve 11, P2 is the minimum operating pressure of the accumulator 13 13 is not used at a pressure lower than this based on the volume of the container.) ■
1 is when the pressure is Pl, and ■2 is 7 when the pressure is P2.
The volume of gas enclosed in the cumulator 13 is shown.

When the accumulator 13 is at the minimum working pressure P2, if an excessive flow rate occurs in the circuits 3 and 4, pressure oil is accumulated in the accumulator 13. As pressure oil accumulates,
The accumulated pressure oil compresses the gas enclosed in the accumulator 13 yen. The volume and pressure of this new gas decrease from point 2 to point 5 on the curve in Figure 2, and the pressure increases in the direction of 5. On the other hand, the volume of pressure oil that occupies 13 yen of the accumulator increases. Pressure increases and pressure IJ1
When the pressure is reached, the relief valve 11 opens and connects the charge circuit 14 to the tank 12, so that the pressure of the sealed gas does not exceed pressure 11. The volume 1 at this time becomes the minimum volume of the gas enclosed in the accumulator 13.

In this state, if a flow shortage occurs in the circuit 3.4, the pressure oil accumulated in the accumulator 13 will be transferred to the charge circuit 14,
It is discharged via the check valves 7 and 30 and the flushing valve 6. Therefore, the volume-pressure change is from point 1 to point on the curve in the direction 'IK'.Therefore, the volume of the enclosed gas increases and naturally the volume of the hydraulic fluid decreases. ), the pressure decreases. When the pressure reaches the minimum working pressure P2, the pressure does not become lower than that, and the volume v2 of the sealed gas at that time becomes the maximum volume of the sealed gas in the 7 cumulator 13.0 As is clear from the above explanation, , accumulator 1
The effective volume of 3 is V, -Vl, and the pressure difference to obtain this effective volume is Pl-P. Therefore, if the volume of the accumulator 13 is constant, in order to obtain a larger effective area, the pressure Pl, that is, the set pressure Pl of the relief valve, is increased to further reduce the volume VxY, and the pressure However, if the set pressure P of the IJ IJ-7 valve is increased, the pressure loss in the circuit will increase, which is undesirable.
As is clear from the curve, the effective volume increases very little even if the pressure F1 is increased. Furthermore, when the pressure P1 is increased to increase the pressure difference, the sealed gas becomes adiabatically compressed and instantly becomes high temperature. For example, in the case of a bladder type accumulator, the bladder separating the pressure oil and the sealed gas burns. Air cannot be used as the sealing gas, and an inert gas such as nitrogen must be used, as there is a risk of fire or explosion.

On the other hand, increasing the size of the accumulator itself in order to obtain a large effective volume increases the area occupied by the accumulator and increases the number of units.The purpose of the present invention is to obtain a large ringing volume with a small pressure difference. The object of the present invention is to provide a capacity compensation device for a hydraulic closed circuit that can also use air as a gas.

To achieve this objective, the present invention provides a pressurized tank having an oil chamber connected to a closed hydraulic circuit, an air chamber to which air is supplied, a deformable diaphragm separating both chambers, and the air chamber. a pressure setting means connected to the air chamber via a check valve; an air pressure supply source connected to the pressure setting means; and air set to a pressure higher than the set pressure of the pressure setting means connected to the air chamber. An embodiment of the present invention shown in FIG. 3 will be described below.

In Fig. 3, variable displacement pump 1, single cylinder cylinder 2, circuit 3.4, switching valve 5, flushing valve 6, check valves 7, 8, 9, 30, charge pump 10, and relief valve constitute a closed circuit. 11, tank 12, and their connections are the same as those of the hydraulic closed circuit shown in Fig. wE1, so the explanation will be omitted. 15 is a pressurized tank. Pressurized tank 1
5 is divided into an oil chamber A and an air chamber B by a diaphragm [K provided approximately in the center thereof. The diaphragm 16 is made of a stretchable and deformable material such as rubber, and separates the compartments so that the pressurized oil in the oil chamber A does not enter the air i[B, and the air in the air chamber B does not enter the oil chamber A. . The volume ratio between the oil chamber A and the air chamber B changes as the diaphragm 16 deforms.・17 and 18 are oil chamber A and air chamber BK & cut guard respectively. Each of the guards 17 and 18 is formed, for example, in a mesh shape or in a spherical shape so that oil and air can freely communicate with each other.
Furthermore, when the diaphragm 16 comes into contact with the guard 17 or 18 due to hydraulic or pneumatic pressure, the diaphragm 16 It will not deform any further.

19 is a safety valve communicating with the air chamber B of the pressurized tank 15. A predetermined pressure can be set in the safety valve 19, and when the air pressure in the air chamber B exceeds this set pressure, the safety valve 19 opens and the air in the air chamber B is released. safety valve 1
The set pressure 9 is selected to be lower than the set pressure of the relief valve 11.

20 is a check valve that communicates with the air chamber B and blocks the flow of air from the air chamber B.

21 is a pressure reducing valve connected to the check valve 20 on one side and the air tank 22 on the other side. A predetermined pressure is set in the pressure reducing valve 21, and when the air pressure in the air chamber B exceeds this set pressure, the pressure reducing valve 21 closes and the air tank 2
2, the supply of air to air chamber B is cut off. Pressure reducing valve 21
The set pressure is selected to be lower than the set pressure of the safety valve 190.

A near compressor 23 supplies air to the air chamber B of the pressurized tank 15, and compressed air from the near compressor 23 is stored in the air tank 22. 24 is an air tank 220 safety valve, which releases air when the pressure of the air tank 22 exceeds a predetermined value to maintain the pressure below a predetermined value and prevent danger. Pressurized tank 1 shown in Figure 4
The explanation will be based on the volume-pressure curve of air chamber B in No. 5.

The pressurized tank 15 of this embodiment is the same as the accumulator 13 in the hydraulic circuit shown in FIG. 1 in that it repeatedly supplies and accumulates hydraulic oil. That is, if a circuit shortfall of 3.4Kd occurs, the flow from oil chamber A to charge circuit 14, check valves I and 3
Pressure oil is supplied to the circuits 3 and 4 through the flushing valve 6 and the flushing valve 6, and when the flow rate of red sea bream occurs in the circuit 3 and 4, the pressure oil is accumulated through the flushing valve 6 and the charging circuit 14. However, its operation is different from that of the accumulator 13 described above.

Here, in FIG. 4, which describes the volume-pressure curve in FIG. 4, which explains the operation of the pressurized tank 15,
The horizontal axis represents the volume of the air chamber B, and the vertical axis represents the pressure P of the air chamber B. Pr indicates the set pressure of the relief valve 11, Pa indicates the set pressure of the safety valve 19, and Pc indicates the constant pressure of the pressure reducing valve 210.

As described above, the relationship between the set pressures is Pr>Pa>Pc. Further, (1) indicates the volume of the air chamber B when the diaphragm 16 contacts the guard 18, and (2) indicates the volume of the air chamber B when the diaphragm 16 contacts the guard 17.

Now assume that an excess flow occurs in circuit 3 or 4, and that circuit 3 has an excessive flow rate. This accumulation continues as long as the pressure on the low pressure side of circuit 3 or 4 is higher than the pressure in oil chamber A, until the pressure in oil chamber A reaches the set pressure Pr of relief valve 11 (at this time, diaphragm 1
6 contacts guard 18 and air ii! The pressure B is equal to the pressure Pa of the safety valve 19. Since the pressure Pc of the pressure reducing valve 21 is set lower than the pressure Pa, the air chamber B and the pressure reducing valve 21 are shut off by the check valve 20. Oil room A
The pressure in the air chamber B is higher than the pressure Pa in the air chamber B.

In this state, if a shortage of circuit 3 or nKi occurs, pressure oil is released from oil chamber A, and its pressure decreases from pressure Fr to become equal to pressure Pa of air chamber B. This state is the state at the point shown in FIG.

Furthermore, if the flow rate in circuit 3 or 4 continues to be insufficient, pressure oil continues to be released from oil gA due to the air pressure in air chamber B.
Diaphragm 16 separates from guard 18.

The air pressure in the air chamber B is lower than the set pressure Pa of the safety valve 19, but lower than the set pressure Pc of the pressure reducing valve 21, so the supply of air to the air gB is fiwlr by the reduced pressure 9F:21. Since the diaphragm 16 is pushed and deformed by the air pressure in the air chamber B, the Hiiragi St in the air chamber B increases and its pressure decreases (this change in volume and pressure is calculated from the point Kl to the curve ml). During this period, the pressure in the air chamber B and the pressure in the oil chamber A are equal.

The pressure in the air chamber B decreases to the set pressure PC of the pressure reducing valve 21,
When the transition reaches point 4 on the curve idI, the pressure reducing valve 21
is opened to supply air from the air tank 22 to the air chamber B. Once that happens, the pressure of the air 4B will not decrease any further. On the other hand, the V4 membrane 16 further softens its deformation toward the guard 17 due to the pressure in the air chamber B, so hydraulic oil continues to be released from the oil chamber A, and the volume of the pressure chamber B increases. Let's go. That is, the volume of Ikeshi B increases while the pressure PC remains constant. The stiffness changes directly from 4 to the point #Mll
It will be rejected.

When the 1111i expansion 16 continues to deform and comes into contact with the guard 17 one by one and reaches a point on the straight line, the air chamber B has a pressure PC.
It becomes a constant state of 1 volume v2. At this time, if the pressure in circuit 3 or 4 is still lower than the pressure in oil chamber B, pressure oil is released from the oil blind person.

In this state, when excess flow occurs in circuit 3 or 4 and the pressure in circuit 14 increases, pressure oil accumulates in oil chamber A, so the pressure in oil chamber A increases, and the air i [B] increases. pressure P
It becomes equal to C. As the accumulation continues, the diaphragm 16 is pushed away from the guard 17 by the pressure in the oil chamber A. At this time,
As the volume of the air chamber B decreases, its pressure increases and becomes equal to or higher than the set pressure 20 of the pressure reducing valve 21, so the check valve 20 blocks the passage of air from the air chamber B to the pressure reducing valve 21. Oil room A
As pressure oil accumulates in the diaphragm 16, the guard 18
As the air chamber A continues to deform toward , the volume of the air chamber A decreases and the pressure increases. This volume-pressure change changes along the curve IK from the point Ks, during which time the air iB
The oil NA pressure is in a strange state.

The pressure in the air chamber H increases to the set pressure Pa of the safety valve 19,
When the transition along the 4 ml curve reaches the point ., the safety valve 19 opens and releases air amount B to the outside. Once upon a time,
The pressure in air chamber B will not increase any further. on the other hand,
Since the spacer M#16 continues to deform further toward the card 18 due to the pressure in the oil chamber A, the threading pressure oil is accumulated in the oil chamber A, and the volume of the air chamber B17) continues to decrease. This impoverishment is indicated by a straight line ``D'' from point 6. When the diaphragm 16 undergoes deformation and finally fits into the guard 18 and reaches point 3 on the direct resistance ■, the air chamber B has a pressure Pa, Volume ■
It will be in a negative state of 1. At this time, it was still I! 12I Approximately 3 or 4 pressure is high (if accumulation in oil chamber A continues, oil 4
The pressure of A is higher than the pressure Pa of air %H, and IJ
In such an operation in which the pressure rises to the set pressure Pr of the IJ-) valve 11, the change in volume-pressure
When the pressure in the air chamber B remains constant, the diaphragm 16 deforms toward the guard 1r, and the pressure oil is released from the oil chamber A. Jjt
When the shortage is eliminated, the deformation of the diaphragm 16 stops (at this time, the relationship between the volume of the air chamber B and the pressure is 11).
The point on s11 is indicated by 7. )0 After that, when pressure oil accumulates in oil chamber A, the change in volume-pressure of air chamber B is:
Transitioning along the curve VIK from point 7 to point Ks on the straight line ■
After the pressure reaches K and becomes constant at P1, the diaphragm 16 deforms and the straight line I reaches the point where it contacts the guard 18.
It moves along VK.

If the 5 transition along the straight line ■ stops before reaching point 3, that is, if the accumulation of pressure oil in the oil chamber λ stops, the deformation of the diaphragm 16 toward the guard 18 also stops. (At this time, the relationship between the volume and pressure of air chamber B is at a point on the straight line ■,
It is indicated by. ) Then, when pressure oil is released from oil chamber A, air! ! The change in volume-pressure of B changes from point 9 along the curve ■, and reaches point Klo on the straight line n, where the pressure P
It becomes constant at c, and then changes along [line ■].

In this way, in this embodiment, a pressure reducing valve is connected to the air chamber of the pressurized tank via a safety valve and a check valve, and the safety valve is set so that the pressure difference to obtain the effective volume is lower than the set pressure of the relief valve. Since the difference is between the pressure and the set pressure of the pressure reducing valve, the pressure difference can be made small.

As a result, the pressure drop in the circuit does not increase due to the high set pressure of the relief valve, and the temperature rise due to adiabatic compression of gas can also be reduced, making it possible to use air. In such cases, an on-vehicle near compressor can be used, and the volume of the pressurized tank can also be small.

Therefore, it is possible to reduce the pressure difference to obtain the effective volume for capacity compensation, which makes it possible to reduce the pressure loss in the circuit and to use air in the capacity compensation device. The volume of the device can also be reduced.

[Brief explanation of drawings]

Figure 1 is a system diagram of a conventional hydraulic closed circuit, and Figure 2 is a diagram of 1eE.
A characteristic diagram showing the relationship between the volume and pressure of the gas enclosed in the accumulator shown in IK, FIG. 3 is a system diagram of a pressurized tank in a hydraulic closed circuit according to one embodiment of the present invention, and FIG. FIG. 3 is a characteristic diagram showing the relationship between the volume and pressure of a pressure tank air chamber. 1...Variable displacement pump, 2...Single rod cylinder, 5...Switching valve, 10...
Charge pump, 11...Relief valve, 15.
... Pressurized tank, 19 ... Safety valve, 20
...Check valve, 21...Reducing valve, 22.
...Air tank, A...Oil chamber, B...
...Air chamber. Figure 1 Figure 2 Figure 4 Figure 1 Figure '3 B\ /6-A'

Claims (1)

[Claims] In a hydraulic closed circuit comprising a cylinder, a low pressure selection valve, a charge pump, a discharge pressure setting means, and a variable displacement pump, an oil chamber connected to the hydraulic closed circuit, an air chamber to which air is supplied, and A gap H that changes the ratio of the volumes of the two types by cutting the oil chamber and the air chamber and deforming the oil chamber and the air chamber.
a pressurized tank, a pressure setting means connected to the air chamber via a check valve, an air pressure supply source connected to the pressure setting means, and a pressure setting means connected to the air W1. A hydraulic closed circuit capacity compensator comprising an air discharge pressure setting means set to a higher pressure than the set pressure.