JPH07103850B2 - Surge pressure absorption circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surge pressure absorption circuit suitable for use in a hydraulic device that controls the pressure of a pump line.

(Prior Art) As a concrete example of a surge pressure absorption circuit of a hydraulic device for controlling the pressure of a pump line, there is a surge pressure absorption circuit previously proposed by the applicant (see Japanese Patent Application No. 61-101823). . The circuit is schematically shown in FIG. 5, and in the figure, 51 indicates a hydraulic pump, and the primary side of the constant difference type normally closed type pressure reducing valve 52 is connected to the hydraulic pump 51. The secondary side thereof is connected to the hydraulic cylinder 53 by a pump line 54 and a supply line 55, respectively. On the other hand, the supply line 55 is connected to a branch line 58 communicating with the tank 56 and provided with a surge pressure absorption valve 57. A primary side of the flow control valve 59 with pressure compensation is connected to the pump line 54, and a secondary side of the flow control valve 59 communicates with a tank 61 via an electromagnetic pilot relief valve 60. . When the fluid flows from the pump line 54 to the tank 61 through the flow control valve 59 and the relief valve 60, on the secondary side of the flow control valve 59, the pressure is set at the relief valve 60 (hereinafter, It is designed to be maintained at a pilot pressure), and this pilot pressure is applied to the pilot chamber 62 of the pressure reducing valve 52 and the surge pressure absorbing valve 57.
Are led to the spring chamber 63 and the spring chamber 63 via lines 64 and 65, respectively.

In the circuit having the above configuration, the working fluid is supplied from the supply line 55 to the hydraulic cylinder 53, and the hydraulic cylinder 53 is operated.However, when the stroke end is reached during the operation, etc. The pressure in the supply line 55 causes a sharp rise. At this time, the increased pressure value is the sum of the pilot pressure in the surge pressure absorption valve 57 and the pressure equivalent to the spring force of the spring chamber 63 (hereinafter referred to as surge pressure absorption pressure value).
When the pressure exceeds, the surge pressure absorption valve 57 automatically opens to suppress the pressure increase in the supply line 55.

(Problems to be Solved by the Invention) FIG. 3 shows a pressure change in the supply line 55 in the above circuit configuration. As shown in the figure, when the above stroke end is reached, a sharp pressure increase is shown as shown in A of the figure, and the surge pressure absorption valve 57 opens,
The rising pressure can be suppressed at the point B in the figure, but in general, the opening operation of the surge pressure absorption valve 57 as described above cannot sufficiently follow a rapid pressure increase such as surge pressure. ,
The pressure value at the point B greatly exceeds the surge pressure absorption pressure value of the surge pressure absorption valve 57. Therefore, next, as shown in FIG. 6C, a pressure drop toward the surge pressure absorption pressure value occurs. At this time, since the difference between the surge pressure absorption pressure value and the pressure value at the point B is large, the surge pressure absorption valve 57 is, for example, fully opened. That is, a large amount of high-pressure working fluid in the supply line 55 is discharged to the tank 56 through the surge pressure absorption valve 57 in the fully opened state. Therefore, in C, a sudden pressure drop occurs, and the drop speed at this time cannot be followed by the closing operation of the surge pressure absorbing valve 57 and the secondary pressure adjusting operation of the pressure reducing valve 52 as in the above case. The pressure in the line 55 lowers below the surge pressure absorption pressure value as shown in FIG. 3D, which causes a so-called undershoot phenomenon. In such an undershoot phenomenon, for example, when the hydraulic cylinder 53 is used as an injection cylinder in an injection molding machine, it may cause resin leakage in the injection molding die, resulting in burrs, short circuits, sink marks, etc. Will cause defective molding.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a surge pressure absorbing circuit capable of preventing an undershoot phenomenon at the time of absorbing a surge pressure.

(Means for Solving the Problems) Therefore, in the surge pressure absorbing circuit of the present invention, the pump line 3 is provided on the primary side of the constant pressure reducing valve 2 and the supply line 4 is provided on the secondary side.
While connecting the spring chamber 6 of the pressure reducing valve 2 to the supply line 4 and the pilot chamber 7 to the pump line 3 by the pilot line 9 provided with the flow control valve 8 with pressure compensation. The pilot chamber 7 is connected to the pilot type relief valve 12, the surge pressure absorption valve 15 is connected to the branch line 14 branched from the supply line 4, and the spring chamber of the surge pressure absorption valve 15 is connected.
16 is connected to the pilot chamber 7 of the pressure reducing valve 2 and the pilot chamber 18 of the surge pressure absorbing valve 15 is connected to the front side of the surge pressure absorbing valve 15, and further, the supply line 4 and the surge pressure absorbing valve 15 are connected. The spring chamber 16 is connected by a bypass line 21 in which a check valve 20 which allows a fluid flow from the supply line 4 toward the spring chamber 16 and a throttle 19 are interposed in series.

(Operation) First, the normal operation of the surge pressure absorbing circuit having the above-described configuration will be described in which no surge pressure is generated. In this state, in the relief valve 12, since the predetermined flow rate is flowing through the flow control valve 8, the pressure in the front of the relief valve 12, that is, the pilot line 9 is maintained at the set pressure determined by the relief valve 12, This pressure is surge pressure absorption valve
It acts on 15 spring chambers 16. At this time, the fluid pressure in the supply line 4 is not high enough to open the surge pressure absorbing valve 15, so the surge pressure absorbing valve 15 is kept closed by the fluid pressure in the pilot line 9 and the spring force. ing. In this state, the check valve 20 is connected to the pilot line 9
The fluid is prevented from flowing out from the supply line 4 to the supply line 4.

Next, the operation when a surge pressure occurs in the supply line 4 will be described. First, a surge pressure is generated in the supply line 4, and when this pressure exceeds the surge pressure absorption pressure value of the surge pressure absorption valve 15, the surge pressure absorption valve 15 will open. It occurs with a certain time delay from the point when the surge pressure absorption pressure value is exceeded. With such a time delay, in the stairs before the surge pressure absorption valve 15 opens,
Since the fluid pressure in the supply line 4 becomes higher than the fluid pressure in the pilot line 9 due to the surge pressure, the working fluid in the supply line 4 flows from the bypass line 21 to the tank 10 through the relief valve 12. By the way, in the relief valve 12, the pressure at the preceding position (for example, point P in FIG. 1) is maintained at the set pressure when a predetermined flow rate flows through the relief valve 12 through the flow control valve 8. That is, the throttle (set opening) is set so that the P point pressure becomes the set pressure at the predetermined flow rate, and when the fluid flow rate through the bypass line 21 is further added to this, The point pressure becomes a pressure exceeding the above set pressure. When the pressure in the supply line 4 is high as described above, P which is higher than the set pressure in accordance with the pressure.
The point pressure acts on the spring chamber 16 of the surge pressure absorption valve 15. Therefore, the opening when the surge pressure absorption valve 15 opens with a time delay does not reach the fully open state as in the case where the P point pressure is the set pressure, and the opening is smaller within the control range. Become. As a result, the rapid discharge operation through the surge pressure absorption valve 15 is suppressed, and the rapid pressure drop in the supply line 4 can be suppressed. Further, as described above, even if the surge pressure absorption valve 15 is opened to lower the fluid pressure in the supply line 4 and the fluid pressure is lower than the pressure in the pilot line 9, the surge pressure absorption valve 15 passes from the pilot line 9 via the bypass line 21. The flow of fluid to the supply line 4 is blocked by the check valve 20. That is, even if the fluid pressure in the supply line 4 decreases, the pressure in the spring chamber 16 of the surge pressure absorbing valve 15 does not decrease accordingly, and the pressure in the spring chamber 16 can be maintained to some extent. 15 quick valve closing operations can be ensured.

In this way, the surge pressure absorption valve 15 can be quickly closed while preventing a sudden pressure drop in the supply line 4 due to the operation of the surge pressure absorption valve 15 when a surge pressure is generated. It is possible to shift to a predetermined set pressure while suppressing the undershoot phenomenon.

(Example) Next, a specific example of the surge pressure absorbing circuit of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a hydraulic pump. The primary side of a constant difference type normally closed type pressure reducing valve 2 is connected to the hydraulic pressure pump 1 by a pump line 3 and the pressure reducing valve 2 is The secondary side is connected by a supply line 4 to a hydraulic cylinder 5 as an actuator.
The spring chamber 6 of the pressure reducing valve 2 is connected to the supply line 4, and the pilot chamber 7 acts as a throttle resistance and keeps the passing flow rate constant even if the pressure before and after the valve varies. It is connected to the pump line 3 by a pilot line 9 provided with a pressure compensation flow control valve 8 having a function. A tank line 11 communicating with the tank 10 is connected to the pilot line 9 at a position closer to the pressure reducing valve 2 than the flow control valve 8. The tank line 11 is connected to an electromagnetic pilot type relief valve 12 Is installed.

On the other hand, a branch line 14 communicating with the tank 13 is connected to the supply line 4, and a surge pressure absorption valve 15 is provided in the branch line 14. The spring chamber 16 of the surge pressure absorption valve 15 is a tank line to the pilot line 9 described above.
It is connected by a line 17 to 11 connection points P. The pilot chamber 18 of the surge pressure absorption valve 15 is connected to the branch line 14 on the supply line 4 side of the surge pressure absorption valve 15. And the supply line 4 and the line
17 is connected by a bypass line 21 in which a throttle 19 and a check valve 20 that allows a fluid flow from the supply line 4 toward the line 17 side are interposed.

Next, the operating state of the surge pressure absorption circuit configured as described above will be described. First, a case where the pressure state in the circuit is in an equilibrium state will be described. At this time, a predetermined flow rate of working fluid flows from the pump line 3 through the flow rate control valve 8 and the relief valve 12 to the tank 10, and in this flow state. The pressure in front of the relief valve 12 (hereinafter referred to as P point pressure) is maintained at a predetermined set pressure. This P point pressure acts on the pilot chamber 7 of the pressure reducing valve 2 and the spring chamber 16 of the surge pressure absorbing valve 15, so that the pressure reducing valve 2 causes its secondary pressure, that is, the pressure in the supply line 4. Is adjusted to a pressure equal to the difference between the P point pressure and the spring force equivalent pressure in the spring chamber 6 (for example, 3 kgf / cm ² ), and is supplied to the hydraulic cylinder 5. At this time, the surge pressure absorption valve 15 has a sum of the pressure equivalent to the spring force of the spring chamber 16 of the surge pressure absorption valve 15 (for example, 1 kgf / cm ² ) and the P point pressure (hereinafter, the surge pressure absorption pressure value and Since the pressure of the supply line 4 is lower than that of the above), the closed state is maintained.

On the other hand, during the operation of the above-described device, the fluid pressure in the supply line 4 is rapidly increased due to the hydraulic cylinder 5 reaching the stroke end, and the surge pressure is increased as shown in FIG. 2 (A). When it occurs, when the value rises in the process of the pressure rise and causes the surge pressure absorption pressure value of the surge pressure absorption valve 15, the surge pressure absorption valve 15 opens and the high pressure fluid in the supply line 4 Will be discharged to the tank 13 through the surge pressure absorption valve 15. However, the closing operation of the surge pressure absorption valve 15 is opened with a time delay from the time when the pressure on the supply line 4 side exceeds the surge pressure absorption pressure value, so the pressure of the supply line 4 is The surge pressure rises to a value indicated by point B in FIG. 2 which exceeds the absorption pressure value, that is, an overshoot occurs. From this point onward, the pressure in the supply line 4 becomes the second pressure because the internal high-pressure fluid is discharged through the surge pressure absorption valve 15.
A pressure drop will occur as shown in FIG.

In the circuit of the above embodiment, the working fluid can flow from the bypass line 21 to the tank 10 through the relief valve 12 when the pressure in the supply line 4 is high. In the relief valve 12, the preceding position,
That is, the P point pressure is maintained at the set pressure when the predetermined flow rate flows through the flow rate control valve 8, that is, the throttle (set opening) at which the P point pressure becomes the set pressure at the predetermined flow rate. And the above bypass line
When the fluid flow rate through 21 is added, the P point pressure becomes a pressure exceeding the above set pressure. That is, the P point pressure indicates a pressure change corresponding to the pressure change in the supply line 4, as a pressure determined by the flow resistance and the fluid flow rate in the throttle valve 19 and the relief valve 12 provided in the bypass line 21. When the pressure in the supply line 4 is high as described above, the P point pressure corresponding to the pressure acts on the spring chamber 16 of the surge pressure absorption valve 15,
The opening degree of the surge pressure absorption valve 15 does not reach the fully open state unlike the conventional device, and can be set to a smaller opening degree within the control range. At this time, as indicated by C in FIG. 2, the pressure decrease rate can be made slower than that in the case of the conventional device (C in FIG. 3). When the value becomes equal to or lower than the surge pressure absorption pressure value set in advance by the valve 12, it is possible to sufficiently follow the decreasing speed of the closing operation of the surge pressure absorption valve 15. As a result, it is possible to shift to a predetermined set pressure state and hold it without causing the undershoot phenomenon as shown in FIG.

The third figure, in the conventional device, the surge pressure of age in a stable pressure state E (e.g. 50 kgf / cm ^2), by operating the electromagnetic pilot relief valve 60, low pressure pressure conditions G (e.g. 20 kgf / cm ² ), The pressure change in the supply line 55 is also shown. In this case as well, the undershoot phenomenon F in which the pressure is set to the low pressure side G or less occurs in the supply line 55. In other words, the pilot fluid introduced into the spring chamber 63 of the surge pressure absorption valve 57 is operated by instantaneously operating the relief valve 60 to a predetermined opening corresponding to the low pressure side set pressure G so as to open the valve. Are rapidly discharged through the relief valve 60. At this time, as a result of the follow-up delay in the flow control valve 8, the fluid pressure in the pilot line 9 drops significantly. Therefore, the spring chamber 63 of the surge pressure absorption valve 57 is
And a large differential pressure state occurs between the supply line 55 and the surge pressure absorption valve 57 from the closed state to the fully opened state. The fluid in the supply line 55 is discharged through the surge pressure absorption valve 57,
When a sudden pressure drop occurs, an undershoot as shown in the figure occurs due to the delay in the operating speed of the surge pressure absorption valve 57, as described above. This phenomenon causes defects such as burrs, short circuits, and sink marks similar to those described above when the pressure is changed when the pressure process is changed from the pressure process during injection molding to the cooling process.

Even when shifting to such a low pressure side set pressure, in the circuit of the above embodiment of the present invention, the bypass line 21
Similarly to the above, when the pressure capable of suitably suppressing the pressure decrease rate in the supply line 4 acts and when the pressure falls below the surge pressure absorption pressure value, the surge pressure absorption valve also follows the pressure decrease rate. 15 closing movements are given. Therefore, as shown by D->E-> F in FIG. 2, it is possible to shift to the low pressure side set pressure without causing an undershoot.

FIG. 4 shows a circuit diagram of a surge pressure absorbing circuit in another embodiment of the present invention. In the apparatus configuration shown in the figure, the same functional parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In this device,
A variable throttle 31 is provided in the supply line 4, and the secondary side of the variable throttle 31 is connected to a pilot line 9 leading to the pilot chamber 7 of the pressure reducing valve 2 by a supply pressure feedback line 32. A diaphragm 33 for setting a differential pressure is provided. The flow rate supplied to the hydraulic cylinder 5 is kept substantially constant by the throttles 31 and 33 even under a low load condition, for example, when the hydraulic cylinder 5 moves forward, and a predetermined forward speed is maintained. It is done like this. The reason is as follows. First, when the hydraulic cylinder 5 is in a low load state as described above, the entire amount of the fluid that has passed through the flow control valve 8 passes through the feedback throttle 33 until the P point pressure reaches the set pressure of the relief valve 12. As a result, a differential pressure ΔP ₃ is generated before and after the feedback throttle 33. On the other hand, the pressure reducing valve 2 supplies to its secondary side a fluid having a fluid pressure lower than the fluid pressure at the point P acting on the pilot chamber 7 by the spring force equivalent pressure ΔP _{s of} the spring chamber 6, which is variable. Since the differential pressure ΔP ₁ generated before and after the throttle 31 is decreased, the pressure reducing valve 2 is eventually ΔP ₃ = ΔP _s + Δ.
The action that satisfies the relationship of P ₁ will be performed. That is, as described above, by feeding back the supply pressure to the pilot chamber 7 of the pressure reducing valve 2 via the differential pressure setting throttle 33, the differential pressure generated in the variable throttle 31 is reduced by the throttle resistance in the feedback throttle 33. The secondary pressure adjusting operation of the pressure reducing valve 2 is performed so that it becomes equal to the pressure difference obtained by subtracting the spring force equivalent pressure of the spring chamber 6 of the pressure reducing valve 2 from the equivalent pressure, and therefore the variable throttle 31 is circulated. The flow rate of the working fluid supplied to the hydraulic cylinder 5 is
It is maintained almost constant regardless of the supply pressure. Then, when the hydraulic cylinder 5 whose speed is controlled to be constant as described above is moved forward to reach the stroke end thereof, the pressure in the supply line 4 is increased and Similar to the first embodiment, a surge pressure exceeding the set pressure at the relief valve 12 will be generated. At this time, similarly to the above, due to the action of the fluid flowing through the surge pressure absorption valve 15 and the bypass line 21, the surge pressure is suppressed with overshoot suppressed and undershoot does not occur. Further, even when the pressure is changed to the low-side set pressure by changing the set pressure of the relief valve 12, the undershoot does not occur in the same manner as described above.

In each of the above-mentioned embodiments, the relief valve 12 is of a fixed opening type, that is, a set pressure changing operation, so that when the predetermined flow rate flows through the pressure compensating flow rate control valve 8, the pressure becomes a predetermined pressure in front of it. At times, the description has been given of the type in which the opening degree is changed by electromagnetic operation, but the present invention can also be applied to a device in which the relief valve 12 is a spring pressure setting type relief valve.

(Effect of the Invention) As described above, in the surge pressure absorbing circuit of the present invention,
When the high pressure generated in the supply line is discharged through the surge pressure absorption valve, the opening degree of the surge pressure absorption valve is also appropriately controlled by the high pressure, and the discharge speed is suppressed. Therefore, since the closing operation of the surge pressure absorption valve that follows the pressure decrease rate of the supply line can be given, it is possible to absorb the surge pressure without causing the undershoot phenomenon. When used as a control circuit for an injection cylinder of a machine, it is possible to reduce defects such as burrs and sink marks caused by the undershoot phenomenon.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a surge pressure absorbing circuit according to a first embodiment of the present invention, FIG. 2 is a graph showing pressure change in the supply line of the apparatus of FIG. 1, and FIG. A graph similar to FIG. 2 in the conventional device, FIG. 4 is a circuit diagram of the surge pressure absorbing circuit in the second embodiment of the present invention, and FIG. 5 is a circuit diagram of the surge pressure absorbing circuit in the conventional device. 2 ... Pressure reducing valve, 3 ... Pump line, 4 ... Supply line, 6, 16 ... Spring chamber, 7, 18 ... Pilot chamber, 8 ...
… Flow control valve, 9… Pilot line, 12… Relief valve, 14… Branch line, 15… Surge pressure absorption valve, 19…
… Throttle, 20 …… Check valve, 21 …… Bypass line.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F15B 11/028

Claims (1)

[Claims] 1. A pump line (3) is connected to the primary side of a constant pressure reducing valve (2) and a supply line (4) is connected to the secondary side thereof, and a spring chamber () of the pressure reducing valve (2) is connected. 6) to the supply line (4), and the pilot chamber (7) to the pilot line (9) in which the flow control valve with pressure compensation (8) is provided.
Connect to the pump line (3) respectively, connect the pilot chamber (7) to the pilot type relief valve (12), and absorb the surge pressure in the branch line (14) branching from the supply line (4). The valve (15) is connected, and the spring chamber (16) of the surge pressure absorption valve (15) is connected to the pilot chamber (7) of the pressure reducing valve (2) and the pilot chamber of the surge pressure absorption valve (15) ( 18) is connected to the front of the surge pressure absorption valve (15), and the supply line (4) and the spring chamber (16) of the surge pressure absorption valve (15) are connected to each other. 4) A check valve (20) that allows a fluid flow from the spring chamber (16) to the throttle chamber (19) is connected by a bypass line (21) interposed in series. And surge pressure absorption circuit.