JPH07160341A - Pressure control valve - Google Patents

Abstract

PURPOSE:To effectively prevent a peak pressure from being produced at the time of a transient response of relief control by providing a correcting means which corrects a command for set pressure by the use of time function that makes system pressure reach the set pressure a specific time later when the system pressure rises exceeding a specific pressure value lower than the set pressure. CONSTITUTION:The correction part 20 of a controller 5 corrects the command for the set pressure Po by the time function which makes the system pressure P reaches the set pressure Po the specific time later when the system pressure rises exceeding the specific pressure value Po.k lower than the set pressure Po, and the set pressure Po, a correction time To, and a constant (0<k<1) determining the pressure value P-k at the start of correction are inputted in addition to a detected value (system pressure P) of a pressure sensor 6. If the system pressure P rises and exceeds the specific pressure value Po.k lower than the set pressure Po, the command for the set pressure Po is corrected, so the relief operation of a poppet reacting to the pilot pressure of a proportional solenoid valve 4 is started at the point to of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control valve for keeping a system pressure in a circuit constant.

[0002]

2. Description of the Related Art For example, as a pressure control valve for an industrial machine such as a press molding machine, one having a structure as shown in FIG. 7 is known. Reference numeral 1 denotes a main relief valve that opens and closes a relief passage 2 of the circuit, and includes a poppet 3 that can slide freely inside the valve housing. Two oil chambers A and B are formed on both sides of the piston 3a of the poppet 3, and the opening area of the relief passage 2 is adjusted according to the hydraulic pressure from the pilot proportional solenoid valve 4 to the oil chamber A. The system pressure P of the circuit is directly introduced into the oil chamber B.

The pilot proportional solenoid valve 4 has a supply position for guiding the system pressure P of the circuit to the oil chamber A of the main relief valve 1, a discharge position for releasing the pressure of the oil chamber A to the reservoir side, and a main relief valve 1. It has a neutral position for oil-locking the oil chamber A, and is controlled as described later according to the output of the controller 5.

A pressure sensor 6 for detecting the system pressure P of the circuit is provided as detection means necessary for controlling the controller 5,
A displacement sensor 7 that detects the opening of the main relief valve 1 is provided. The controller 5 compares the detected value (system pressure P) of the pressure sensor 6 with the set pressure P _0, and an arithmetic unit 9 that calculates the opening of the poppet 3 based on the comparison value.
And an adder 10 for comparing the calculated value with the detected value of the displacement sensor 7 and outputting a control signal to the pilot proportional solenoid valve 4.
And an amplifier 11.

The system pressure P of the circuit is the set pressure P.
_When it becomes higher than ₀ , the controller 5 operates the pilot proportional solenoid valve 4 to the discharge position side. Since the oil chamber A of the main relief valve 1 is released to the reservoir via the pilot proportional solenoid valve 4, the poppet 3 opens the relief passage 2 while compressing the return spring 12 and the flow rate Q.
Flows.

When the system pressure P becomes lower than the set P ₀ , the controller 5 operates the pilot proportional solenoid valve 4 to the supply position side. The main relief valve 1 receives the hydraulic pressure from the pilot proportional solenoid valve 4 to the oil chamber A, and therefore is displaced toward the closing side to shut off the flow rate Q of the relief passage 2.

Therefore, by repeating such an operation, the system pressure P is controlled so as to match the set pressure P ₀ as shown in FIG.

[0008]

However, in such a conventional example, the servo control of the pilot proportional solenoid valve 4 is started from the time when the hydraulic pump in the circuit is driven and the system pressure P rises to reach the set pressure P _0. Figure 9
As described above, since it takes some time from the start of control until the flow rate Q flows when the main relief valve 1 is opened, the system pressure P further increases during that time, and a peak pressure is likely to be generated. In particular, there is a problem that the peak pressure is large when the system pressure P rises rapidly.

An object of the present invention is to effectively solve such a problem.

[0010]

Therefore, a valve that opens and closes a relief passage of a circuit in response to a pilot pressure, a means for detecting a system pressure in the circuit, and the detected value are fed back to set the system pressure. In a pressure control valve equipped with a controller that servo-controls to match
When the system pressure rises above a predetermined pressure value which is lower than the set pressure, a command for the set pressure is corrected by a correction function of a time function such that the system pressure reaches the set pressure after a lapse of a predetermined time.

[0011]

According to this, when the system pressure exceeds a predetermined pressure value lower than the set pressure, the command for the set pressure is corrected, so that the relief operation of the valve in response to the pilot pressure is started from that point. . Since the command value of the set pressure changes with time, the system pressure follows the change and rises in a gentle continuous curve, and reaches the set pressure after a lapse of a predetermined time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is a main relief valve, 4 is a pilot proportional solenoid valve, 5 is a controller, 6 is a pressure sensor, and 12 is a displacement sensor.
Since the components other than 0 are the same as those in FIG. 7, the same reference numerals are given and duplicate description is omitted. Correction unit 20 of controller 5
A command set pressure P ₀ when the system pressure rises above the predetermined pressure value P ₀ · k is lower than the set pressure P _0, the system pressure P is time that reaches the set pressure P ₀ after a predetermined time The function is modified, and in addition to the detected value of the pressure sensor 6 (system pressure P), the set pressure P ₀ and the modification time T ₀ are added.
And a constant k (however, 0 <k <1) that determines the correction start pressure value P · k is input.

FIG. 2 is a flow chart for explaining the control contents of the correction section. In addition to reading the system pressure P and the set pressure P ₀ , the correction time T ₀ and the constant k, a predetermined pressure value lower than the set pressure P ₀ is read. Set P ₀ · k (1.01,
1.02). Then, when the system pressure P exceeds the pressure value P ₀ · k, when the flag N is zero, the pressure command value P ′ of the time function such that the system pressure P reaches the set pressure P ₀ after the elapse of the predetermined time T _0. (T) In this example, the pressure command of the first-order lag function is output to the adder 8 and the flag N is set to 1 after the correction time T ₀ has elapsed (1.03 to 1.06).

Even if the system pressure P exceeds the pressure value P ₀ · k, if the flag N is not zero, the pressure command value P ′ to the adder 8 is given.
The set pressure P ₀ is output as (t) (1.04 → 1.
07). When the system pressure is equal to or lower than the predetermined pressure value P ₀ · k, the set pressure P ₀ (which may be the predetermined pressure value P ₀ · k) is output to the adder 8 as the pressure command value P ′ (t) ( 1.0
3 → 1.08).

With such a configuration, the hydraulic pump in the circuit is driven, the system pressure P rises, and the set pressure P
_{When the} predetermined pressure value P ₀ · k lower than ₀ is exceeded, the command of the set pressure P ₀ is corrected, and at that time point t ₀ , the relief operation of the poppet 3 in response to the pilot pressure of the proportional solenoid valve 4 starts. To be done. Pressure command value P '(t) of the correction unit 20
3 changes to the first-order lag by the correction time T ₀ as shown in FIG. 3, so the system pressure P follows the change as shown in FIG. 4 and is a gentle continuous curve, and the set pressure P ₀ after a lapse of a predetermined time.
Will be reached.

Therefore, it is possible to effectively prevent the peak occurrence of the system pressure P, and by changing the setting of the constant k and the time T ₀ , it is possible to easily obtain the transient characteristic matching the system. Also the system pressure P is set a predetermined pressure value P ₀ · k or less of the pressure command value P '(t) to a pressure value P ₀ · k, 5
As described above, when the system pressure P exceeds the pressure value P ₀ · k, the pressure command of the first-order lag function is output to the adder 8, so the system pressure P changes with the same characteristics as in FIG. In order to obtain a transient characteristic that matches the system, the pressure command value P ′ (t) is not limited to the ramp shape as shown in FIG. May be.

Further, the function shown in FIG. 2 may be configured by an electronic circuit. Further, although the relief valve using the pilot type poppet valve is illustrated as the relief valve in FIG. 1, a spool valve may be used instead of the poppet valve.

[0018]

In summary, according to the present invention, a valve that opens and closes a relief passage of a circuit in response to pilot pressure,
In a pressure control valve equipped with a means for detecting the system pressure in the circuit and a controller which feeds back the detected value and servo-controls so that the system pressure matches the set pressure, a pressure value lower than a predetermined pressure value lower than the set pressure is exceeded. When the system pressure rises, the set pressure command is corrected by a time function so that the system pressure reaches the set pressure after a lapse of a predetermined time. Can be effectively prevented. Also, by changing the settings such as the correction time, it is possible to easily obtain the transient characteristics that match the system.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart illustrating correction control in a controller.

FIG. 3 is an output characteristic diagram of a correction unit.

FIG. 4 is a transient characteristic diagram of system pressure.

FIG. 5 is an output characteristic diagram of a correction unit.

FIG. 6 is an output characteristic diagram of a correction unit.

FIG. 7 is a configuration diagram illustrating a conventional technique.

FIG. 8 is a control characteristic diagram of system pressure.

FIG. 9 is a transient characteristic diagram of system pressure.

[Explanation of symbols]

 1 Main Relief Valve 2 Relief Passage 3 Poppet 4 Pilot Proportional Solenoid Valve 5 Controller 6 Pressure Sensor 7 Displacement Sensor 8,10 Adder 9 Calculation Section 20 Correction Section

Claims (1)

[Claims] 1. A valve for opening and closing a relief passage of a circuit in response to a pilot pressure, a means for detecting a system pressure in the circuit, and a servo for adjusting the system pressure to a set pressure by feeding back the detected value. In a pressure control valve equipped with a controller for controlling, when the system pressure rises above a predetermined pressure value lower than the set pressure, a command of the set pressure is given as a time function such that the system pressure reaches the set pressure after a lapse of a predetermined time. A pressure control valve comprising a correction means for applying a correction.