JP2003021103A - Hydraulic circuit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the controlling performance of the supplying amount and pressure of hydraulic oil while suppressing a increase in a cost, and expand a controllable area of pressure to a zero point, in a hydraulic circuit devices 2, 20 wherein a solenoid proportional valve 6 is interposed in a supplying passage 5 of hydraulic oil to a main machine hydraulic circuit 1. SOLUTION: The solenoid proportional valve 6 is provided with a supply position supplying hydraulic oil to the main machine side, a discharge position discharging the hydraulic oil from the main machine side, and a stop position stopping supplying/discharging of the hydraulic oil. A pressure sensor 10 detecting the pressure of hydraulic oil of a downstream supplying passage 5b and a position sensor 11 detecting a spool position (opening) of the solenoid proportional valve 6 are provided, the opening of the solenoid proportional valve 6 is feedback controlled by a digital controller 12 so as to make the supplying amount Q and the supplying pressure P of the hydraulic oil to the main machine side become command values Qi, Pi, on the basis of signals from the pressure sensor 10 and the position sensor 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit device for driving a hydraulic actuator of a mechanical device such as an injection molding machine, and more particularly, to properly control the operating speed and operating force of the actuator. Belongs to the technical field of hydraulic fluid flow rate and pressure control.

[0002]

2. Description of the Related Art Conventionally, as a hydraulic circuit device of this type, an electromagnetic proportional valve (hereinafter, simply referred to as a flow rate proportional valve) for controlling a flow rate of hydraulic oil supplied to an actuator and a pressure adjusting valve have been used. There is an electromagnetic proportional type flow rate adjusting valve device with a relief valve which has a built-in electromagnetic proportional valve (hereinafter, also simply referred to as a pressure proportional valve) and each proportional valve is controlled by a dedicated driver circuit.

In this case, as shown in FIG.
A flow proportional valve (6) is provided in the hydraulic oil supply passage (5) to the hydraulic actuator of the main machine hydraulic circuit (1).
The actuator is connected to the A port on the downstream side of (6), while a constant displacement type pump is installed on the P port on the upstream side.
(3) is connected. Further, by receiving pilot pressures from the upstream side and the downstream side of the flow rate proportional valve (6), the hydraulic oil is bypassed from the upstream side supply passage (5a) to the T port so that the pressure difference between them is substantially constant. A differential pressure compensating valve (7) is provided.

Further, an orifice (17) is provided in the pilot passage (15) on the downstream side for guiding the pilot pressure from the downstream side of the proportional flow valve (6) to the differential pressure compensating valve (7). In the pilot passage (15) between the orifice (17) and the differential pressure compensating valve (7), a pressure proportional valve (8) for relieving hydraulic oil from there and adjusting the pilot pressure on the downstream side is connected. ing. Then, the flow rate proportional valve (6) and the pressure proportional valve
The opening of (8) is controlled by a separate current driver (9, 9).

The operation of the conventional flow rate pressure regulating valve device having such a configuration is automatically switched between the flow rate control mode and the pressure control mode according to the operating state of the actuator. That is, for example, describing the case of supplying hydraulic oil to the hydraulic cylinder of the main engine, when the hydraulic cylinder makes a stroke, the differential pressure across the flow proportional valve (6) is maintained substantially constant by the differential pressure compensating valve (7). Flow rate proportional valve
By controlling the opening of (6), the amount of oil supplied to the hydraulic cylinder can be adjusted and its operating speed can be controlled (flow control mode). At this time, the hydraulic oil discharged from the pump (3) is supplied to the hydraulic cylinder via the P port, the flow rate proportional valve (6) and the A port, and the excess hydraulic oil is supplied from the differential pressure compensating valve (7). It is bypassed to the oil tank (4) via the T port.

When the cylinder reaches the stroke end, the supply passage (5b) on the downstream side is accompanied by a sudden increase in load.
When the oil pressure increases, and this oil pressure exceeds the set pressure of the pressure proportional valve (8), the pressure proportional valve (8), the differential pressure compensating valve (7), and the orifice (17) are so-called pilot type electromagnetic proportional relief. It functions as a valve and prevents further increase in hydraulic pressure. At that time, the pilot pressure of the downstream side pilot passage (15) can be changed by controlling the relief pressure of the pressure proportional valve (8), whereby the relief pressure of the differential pressure compensating valve (7) is changed, and the pump ( It is possible to control the discharge pressure of 3) and thus the supply pressure to the hydraulic cylinder (pressure control mode).

[0007]

However, in the case of the conventional flow rate pressure regulating valve device as described above, both the flow rate and the pressure of the hydraulic oil supplied to the actuator are the characteristics of the solenoid of the solenoid valve (6, 8). Because it will be reflected as it is,
The changes in the flow rate and pressure of the hydraulic oil with respect to the output current value from the current driver (9) are non-linear and have hysteresis (see the broken line graph in FIG. 4). For this reason, it is difficult to obtain sufficient accuracy in controlling the flow rate and pressure of the hydraulic oil, and because the open control does not use an electric sensor, the response speed to the change in the command value cannot be increased so much. There's a problem.

Further, particularly in controlling the supply pressure of the hydraulic oil, even if the current value to the pressure proportional valve (8) is reduced to zero, the relief pressure of the differential pressure compensating valve (7) is not affected by the spring member. The supply pressure to the actuator cannot be made lower than the predetermined pressure because it drops only to the predetermined pressure corresponding to the force. In other words, in the structure of the conventional example, the minimum control pressure of the supply hydraulic pressure is generated due to the pressure control by the relief valve, and the pressure control at a low pressure below this cannot be performed. With respect to this point, for example, in an injection molding machine, there is a low-pressure mold clamping step that is set for protecting the mold, and pressure control at low pressure is also greatly improved.

The present invention has been made in view of the above points, and an object of the present invention is to provide an electromagnetic proportional valve (6) in a hydraulic fluid supply passage (5) to a hydraulic actuator to operate it. In the hydraulic circuit device (2, 20) that controls the liquid supply flow rate and pressure, improve the control accuracy and responsiveness, and especially for the supply liquid pressure, eliminate the minimum control pressure and increase the control range. To expand to zero pressure,
In addition, it is to provide a valve structure capable of suppressing cost increase.

[0010]

In order to achieve the above-mentioned object, the hydraulic circuit device (2, 20) of the present invention comprises an electromagnetic proportional valve (6) for adjusting the supply flow rate of hydraulic fluid to an actuator, A discharge position for discharging hydraulic fluid from the actuator is added, and a supply passage (5b) on the downstream side of the solenoid proportional valve (6) is added.
Pressure sensor (10) that detects the hydraulic fluid pressure of the
A position sensor (11) for detecting the spool position of (6) is provided, and the spool position of the solenoid proportional valve (6) is feedback-controlled based on output signals from these sensors.

Specifically, according to the first aspect of the invention, an electromagnetic proportional valve (6) for adjusting the supply flow rate of the hydraulic fluid is provided in the hydraulic fluid supply passage (5) to the hydraulic actuator, and A differential that receives pilot pressure from the upstream side and downstream side of the solenoid proportional valve (6) and bypasses the hydraulic fluid from the upstream supply passage (5a) to the tank (4) so that the differential pressure becomes constant. It is premised on a hydraulic circuit device (2, 20) provided with a pressure compensation valve (7). The solenoid proportional valve (6) has at least a discharge position for discharging the working fluid from the actuator in addition to the supply position for supplying the working fluid to the actuator, and the downstream side supply passage (5b) A pressure sensor (10) that detects hydraulic fluid pressure and outputs an electric signal, a position sensor (11) that detects the spool position of the solenoid proportional valve (6) and outputs an electric signal, and the pressure sensor (10 ) And position sensor
A controller that receives signals output from (11) and feedback-controls the opening of the solenoid proportional valve (6) so that the supply flow rate or supply pressure of the hydraulic fluid to the actuator reaches a control command value. (12) and can be provided.

According to this structure, while the actuator is operating, the differential pressure across the solenoid proportional valve (6) is maintained substantially constant by the function of the differential pressure compensating valve (7), and the controller (12) controls the differential pressure. The spool position of the solenoid proportional valve (6) is controlled, thereby controlling the flow rate supplied to the actuator (flow rate control mode). At that time, the actual spool position of the solenoid proportional valve (6) is detected by the position sensor (11), and feedback control is performed based on the detection result, so the control of the flow rate of the hydraulic fluid is greatly improved in both accuracy and responsiveness. To be done. Further, since the non-linear characteristic of the solenoid can be apparently absorbed by the feedback control, the characteristic of the flow rate control of the hydraulic fluid can be linearized and the hysteresis can be eliminated.

On the other hand, when the actuator reaches the stroke end and becomes almost inoperative, the hydraulic pressure in the supply passage (5b) on the downstream side increases as the load increases, which is caused by the pressure sensor (10). After being detected, the controller (12) performs feedback control of the solenoid proportional valve (6) according to the detected value. That is, when the solenoid proportional valve (6) is in the supply position, it is supplied by controlling the opening (spool position) of the solenoid proportional valve (6) based on the deviation between the value detected by the pressure sensor (10) and the pressure command value. While adjusting the flow rate, when the solenoid proportional valve (6) is in the discharge position, by adjusting the discharge amount from the supply passage (5b) on the downstream side, the fluid pressure in the supply passage (5b) is finally adjusted. The spool position is controlled so that the pressure command value can be maintained. In this pressure control mode as well, similar to the flow rate control mode, feedback control can improve control accuracy, responsiveness, non-linear characteristics of the solenoid, and the like. Further, by switching the solenoid proportional valve (6) to the discharge position and discharging the hydraulic fluid from the actuator as described above, the hydraulic pressure supplied to the actuator can be reduced to zero.

In addition, according to the above-mentioned structure, the pressure sensor (10) and the position sensor (11) are newly added as compared with the conventional structure.
On the other hand, since the pressure proportional valve (8) and the current driver circuit therefor are unnecessary, the cost increase due to the use of the electric sensor is offset.

In the invention of claim 2, the hydraulic circuit device (2, 20)
As the controller (12) of the flow sensor, the actual flow rate of the hydraulic fluid supplied to the actuator is calculated based on the signal from the position sensor (11), and the actual flow rate is subtracted from the flow rate command value to calculate the flow rate deviation. The actual supply hydraulic pressure of the hydraulic fluid to the actuator is calculated based on the signal from the calculation unit (12b) and the pressure sensor (10), and the actual supply hydraulic pressure is subtracted from the pressure command value to calculate the pressure deviation. PQ selection for selecting the deviation of the flow rate deviation and the pressure deviation, whichever is smaller, and calculating the target spool position of the solenoid proportional valve (6) based on the selected deviation. Department
(12c) and a current driver (12d) that applies a current to the solenoid (6b) of the spool (6a) of the solenoid proportional valve (6) so as to reach the target position calculated by the PQ selection unit (12c). The configuration is provided.

In this configuration, the flow deviation calculator (12b) calculates the flow deviation between the actual supply flow rate of the hydraulic fluid and the flow command value, and the pressure deviation calculator (12a) actually supplies the hydraulic fluid. A pressure deviation between the hydraulic pressure and the pressure command value is calculated. Then, when the actual supply flow rate or the actual supply hydraulic pressure exceeds the control command value, the one that is larger than the control command value, and if both are the command values or less, the one that is closer to the command value is determined by the PQ selection unit (12c). To be selected. That is, the PQ selection unit (12c) judges that it is dangerous to exceed the command value of the pressure or the flow rate, judges the degree of the danger from the deviations of the flow rate and the pressure, and determines the degree of the danger. By selecting the larger deviation, the operation and effect of the invention of claim 1 is realized.

In the invention of claim 3, the hydraulic circuit device (2, 20)
The differential pressure compensating valve (7) has a spring member (7b) for urging the valve body (7a) to the closing side, and the valve body (7a) is closed on the downstream side of the solenoid proportional valve (6). While the pilot pressure from the side is received, the pilot pressure from the upstream side of the solenoid proportional valve (6) is received on the side where the valve body (7a) opens. And the solenoid proportional valve
An orifice (17) for restricting the flow of hydraulic fluid is provided in the pilot passage (15) on the downstream side that guides the pilot pressure from the downstream side of (6) to the differential pressure compensating valve (7). ) And the differential pressure compensating valve (7), the pilot relief valve (18) is connected to the pilot passage (15).

In this structure, even if the spool (6a) of the solenoid proportional valve (6) is stuck at the supply position due to an electrical failure of the controller (12) or dust of hydraulic fluid, the downstream supply Fluid pressure in passage (5b) is pilot relief valve
When the set pressure in (18) is exceeded, the pilot relief valve
(18), the differential pressure compensating valve (7) and the orifice (17) function as a so-called pilot type relief valve, and an increase in hydraulic pressure in the downstream side supply passage (5b) is prevented. Further, when opening / closing the valve body (7a) of the differential pressure compensating valve (7), the flow of hydraulic fluid in the pilot passageway (15) on the downstream side becomes the orifice.
By receiving the passage resistance from (17), appropriate damping is imparted to the operation of the valve body (7a), and stabilization is achieved.

By the way, the pilot passage (15)
Restricting the flow of hydraulic fluid by arranging the orifice (17) in the valve will reduce the operating speed of the valve body (7a) of the differential pressure compensating valve (7). When the supply flow rate of is increased, the response may be deteriorated. That is, when the opening of the solenoid proportional valve (6) is increased in order to increase the flow rate of the hydraulic fluid supplied to the actuator, the differential pressure across the solenoid proportional valve (6) is temporarily reduced, and the differential pressure The valve body (7a) of the compensating valve (7) will be closed. At this time, the pilot passage on the downstream side
At (15), hydraulic fluid flows toward the differential pressure compensation valve (7),
Although the valve body (7a) of the differential pressure compensating valve (7) is moved to the closing side, the force to close the valve body (7a) is about the biasing force of the spring member (7b) in the first place. When the flow of the hydraulic fluid is restricted by the orifice (17) as described above, the closing operation of the valve body (7a) of the differential pressure compensating valve (7) is delayed, which causes There is a response delay in the increase in the flow rate supplied to the solenoid proportional valve (6).

In consideration of such a transient phenomenon, in the invention of claim 4 of the present application, in the hydraulic circuit device (20) of the invention of claim 3, in the pilot passage (15) on the downstream side, The first orifice (21) and the second with a narrower degree than that
And the orifice (22) of the
A check valve (24) that allows the flow of the working fluid toward the differential pressure compensating valve (7) while blocking the reverse flow is provided in the passage (23) that bypasses the orifice (22) of the above.

In this configuration, for example, in order to increase the flow rate of the hydraulic fluid supplied to the actuator, the proportional solenoid valve is used.
When the opening degree of (6) is increased, the hydraulic fluid flows in the downstream pilot passage (15) toward the differential pressure compensating valve (7). The second orifice (22), which passes through the first orifice (21) but has a large degree of throttling, is bypassed, so the passage resistance is relatively reduced and the differential pressure compensating valve (7).
The valve body (7a) can be closed promptly, and thus the flow rate of the hydraulic fluid supplied to the actuator can be increased rapidly.

On the other hand, when the flow rate of hydraulic fluid supplied to the actuator is reduced, the opening of the solenoid proportional valve (6) is reduced. At this time, the hydraulic pressure on the upstream side of the solenoid proportional valve (6) is The pressure suddenly rises, and an extremely high hydraulic pressure acts on the valve body (7a) of the differential pressure compensating valve (7) to open the valve body (7a). At this time, in the downstream pilot passage (15), the hydraulic fluid flows from the differential pressure compensating valve (7) toward the downstream supply passage (5b), and this flow is caused by both the first and second orifices (21, 21). You will receive passage resistance from 22). However, since the extremely high upstream pilot pressure is acting on the valve body (7a) of the differential pressure compensating valve (7) as described above, the flow of the hydraulic fluid is restricted in the downstream pilot passage (15). However, the valve body (7a) of the differential pressure compensating valve (7) is opened sufficiently quickly, and in the end, the response delay does not become a problem when the supply flow rate decreases, rather, rather, the downstream pilot passage (15). The flow of is sufficiently restricted by the second orifice (22),
The stable operation of the differential pressure compensation valve (7) is maintained.

That is, according to the present invention, the orifices (21, 22) arranged in the downstream pilot passage (15) prevent the valve body (7a) opening operation of the differential pressure compensating valve (7) from impairing responsiveness. To ensure stability, while the valve body (7a) closing action is not restricted to ensure responsiveness, which stabilizes and stabilizes the flow rate of hydraulic fluid supplied to the actuator. It is possible to achieve compatibility with the higher level.

According to the invention of claim 5, the hydraulic actuator is for driving the injection molding machine. That is, in general, in the case of an actuator of an injection molding machine, high reproducibility is required while responding to a wide range of molding conditions depending on the shape and material difference of the molded product. It is extremely effective that the pressure circuit device (2, 20) can improve the accuracy of the control of the operating speed and the operating force of the actuator, and by this, the molding quality can be significantly improved.

Further, according to the present invention, since the supply pressure of the hydraulic fluid to the actuator can be controlled to be reduced to zero, it is possible to sufficiently meet the demand in the low-pressure mold clamping process in the injection molding machine. In particular, the supply flow rate of the hydraulic fluid can be increased with high responsiveness as in the invention of claim 4,
Since a thin molded product can be easily molded by an injection molding machine and the molding cycle can be further shortened, the action and effect of the present invention are extremely effective from this point of view.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which a hydraulic circuit device according to the present invention is applied to a servo valve device for driving a hydraulic (hydraulic) cylinder of an injection molding machine or the like will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is connected to a hydraulic circuit (1) of a main machine such as an injection molding machine and supplies hydraulic oil to an actuator such as a hydraulic cylinder (not shown), and the supply flow rate Q and supply thereof. A pressure flow servo valve device (2) (hereinafter referred to as a PQS valve) for adjusting the pressure P to control the operating speed and operating force of the actuator is shown. This PQS
The valve (2) has an A port connected to the main hydraulic circuit (1),
A P port connected to the fixed displacement pump (3) and a T port and a Y port respectively connected to the oil tank (4) are provided, and a hydraulic oil supply passage from the P port to the A port ( An electromagnetic proportional valve (6) for adjusting the supply flow rate is provided in the middle of 5), and the upstream side of the electromagnetic proportional valve (6)
By receiving pilot pressure from each of the (5a) and downstream (5b) supply passages, the hydraulic oil is bypassed from the upstream supply passage (5a) to the oil tank (4) so that the pressure difference between them is substantially constant. A differential pressure compensating valve (7) is provided.

In addition, the PQS valve (2) includes an electromagnetic proportional valve.
A pressure sensor (10) that detects an operating oil pressure P in a supply passage (5b) downstream of (6) and outputs an electric signal, and a solenoid proportional valve.
A position sensor (11) for detecting the position of the spool (6a) of (6) and outputting an electric signal is provided, and further, a signal output from each of these sensors (10), (11). Accordingly, the position of the spool (6a) of the solenoid proportional valve (6) is adjusted so that the supply flow rate Q and the supply pressure P of the hydraulic oil supplied to the main machine hydraulic circuit (1) become the command values Qi and Pi, respectively. That is, a controller (12) for feedback-controlling the opening of the solenoid proportional valve (6) is provided.

Specifically, the solenoid proportional valve (6) is a solenoid operated by a control signal (current) from the controller (12).
(6b) operates, the position of the spool (6a) is controlled against the pressing biasing force of the spring (6c), and the supply position for supplying hydraulic oil to the main engine side and the discharge of hydraulic oil from the main engine side It is configured to be switched between a discharge position and a stop position for stopping the supply and discharge of the hydraulic oil, and is configured to continuously control the passage cross section of the hydraulic oil at the supply position or the discharge position. . Then, as shown, the solenoid proportional valve (6)
The spool (6a) is biased by the spring (6c) toward the discharge position to the right in the figure, and in this discharge position, the solenoid proportional valve (6) opens the upstream supply passage (5a). While closing, connect the supply passage (5b) on the downstream side to the discharge passage (1
The hydraulic oil on the main engine side is returned to the oil tank (4) by communicating with 3). At this time, the passing cross-sectional area of the return oil is continuously controlled by the continuous change of the position of the spool (6a).

As shown in FIG. 2, the solenoid (6b)
When the spool (6a) moves to the left side of the figure against the biasing force of the spring (6c) by the operation of, and reaches the supply position,
The solenoid proportional valve (6) closes the discharge passage (13) and
Connect the upstream and downstream sides of the supply passage (5) so that the pump
The hydraulic oil discharged from (3) will be supplied to the main engine side. At this time, the cross-sectional area of passage of the hydraulic oil is continuously changed due to the continuous change of the position of the spool (6a), and the pump (3)
The supply flow rate Q of the hydraulic oil from the engine to the main engine side is continuously controlled. Further, when the spool (6a) is at a stop position intermediate between the supply position and the discharge position, the solenoid proportional valve (6) is
Upstream and downstream of the supply passage (5), and the discharge passage (13)
Will be closed.

The position sensor (11) is attached to the solenoid proportional valve (6) by mounting the spool (6a) on the solenoid proportional valve (6).
The sensor output becomes zero when is in the central stop position, and when the spool (6a) is in the supply position on the right side of the drawing, the cross-sectional area of passage of the hydraulic oil increases due to the change in the position of the spool (6a). Accordingly, the positive sensor output is increased, and when the spool (6a) is in the discharge position on the left side of the drawing, as the position of the spool (6a) changes, the passage cross section of the hydraulic oil increases. The negative sensor output is reduced.

The differential pressure compensating valve (7) is a relief valve in which a valve body (7a) made of a poppet or the like is biased toward a closing side by a spring (7b) (spring member), and an upstream side supply valve is provided. The branch passage (14) branched from the passage (5a) is arranged so that the branch passage (14) can be bypassed with respect to the discharge passage (13). That is, in the valve body (7a) of the differential pressure compensating valve (7),
The downstream pilot passage (15) branched from the downstream supply passage (5b) is connected to the same side as the spring (7b),
The downstream pilot pressure is received on the closing side of the valve body (7a), while the opposite side receives the hydraulic pressure (upstream pilot pressure) of the upstream supply passage (5a) via the branch passage (14). It is received on the open side of the body (7a).

In the differential pressure compensating valve (7), the pressing force acting on the valve element (7a) by the upstream pilot pressure is higher than the pressing force acting on the valve element (7a) by the downstream pilot pressure. When it becomes larger than the biasing force of the spring (7b), it opens to bypass the hydraulic oil in the upstream supply passage (5a) to the discharge passage (13) via the branch passage (14). As a result, when the upstream pilot pressure decreases, the valve body (7a) closes, the bypass of hydraulic oil is interrupted, and the upstream pilot pressure increases again.
By repeating such opening / closing operation of the valve element (7a), the differential pressure across the solenoid proportional valve (6) is maintained substantially constant. By thus compensating the differential pressure across the solenoid proportional valve (6) to be constant, the opening of the solenoid proportional valve (6) communicating from the upstream supply passage (5a) to the downstream supply passage (5b), That is, the spool position corresponding to the passage cross-section of the hydraulic oil has a fixed correspondence with the actual supply flow rate, which makes it possible to obtain the actual supply flow rate based on the spool position.

The downstream pilot passage (15) is provided with an orifice (17) for restricting the flow of hydraulic oil, and
A branch path is provided between the orifice (17) and the differential pressure compensation valve (7).
(15a) is connected, and a safety valve (18) (pilot relief valve) is arranged in this branch passage (15a). The safety valve (18)
Is to open when the oil pressure in the branch passage (15a) becomes higher than the set pressure of the spring, and to relieve the oil pressure in the downstream pilot passage (15) via the branch passage (15a). As a result, a differential pressure across the orifice (17) is generated, and the hydraulic pressure in the downstream pilot passage (15) decreases, causing a differential pressure compensation valve.
(7) is opened. Then, by opening the differential pressure compensating valve (7), the hydraulic oil in the supply passage (5) is discharged from the T port to the oil tank (4). That is, the differential pressure compensating valve (7) is a safety valve (18) when the hydraulic pressure in the supply passage (5) rises excessively.
It also has a function of releasing hydraulic pressure as a so-called pilot type relief valve in cooperation with.

The orifice (17) has a circular cross section with a diameter of, for example, about 1 mm, and the differential pressure compensation is performed by throttling the flow of hydraulic oil in the downstream pilot passage (15) to give passage resistance. Appropriate damping is applied to the opening / closing operation of the valve body (7a) of the valve (7) to stabilize the operation of the differential pressure compensating valve (7), and thereby the flow rate of the hydraulic oil in the supply passage (5). It also has the function of suppressing the decrease in pressure vibration.

The controller (12) is a digital controller that reads out and executes a control program, which is electronically stored in a memory (not shown), by the CPU at predetermined time intervals, and outputs a signal from the pressure sensor (10). Based on the above, an actual supply pressure P (actual supply pressure) of the hydraulic oil to the main engine side is obtained, and this is subtracted from the pressure command value Pi (target pressure) to calculate a pressure deviation, and a pressure deviation calculation unit (12a) Similarly, on the basis of the signal from the position sensor (11), the actual supply flow rate Q (actual supply flow rate) of the hydraulic oil to the main machine side is obtained, and this is subtracted from the flow rate command value Qi (target flow rate). A flow rate deviation calculating unit (12b) for calculating a flow rate deviation is provided. In other words, the memory of the controller (12) stores a control program that implements the functions of the pressure deviation calculation unit (12a) and the flow rate deviation calculation unit (12b) by software.

Further, the controller (12) compares the pressure deviation and the flow rate deviation calculated by the pressure deviation calculating section (12a) and the flow rate deviation calculating section (12b) with each other, and A PQ selector (12c) is provided which selects the smaller one and calculates the target opening of the solenoid proportional valve (6), that is, the position of the spool (6a) based on the selected deviation according to the so-called PID control law. . Then, this PQ selection unit (12
From the current driver circuit (12d) receiving the output from c) to the solenoid (6b) of the solenoid proportional valve (6), the solenoid proportional valve (6)
An electric current for moving to the target opening degree is applied.

The calculation processing by the PQ selection section (12c) is also realized by executing the control program stored in the memory, and the smaller value of the pressure deviation and the flow rate deviation is selected. Has become. Specifically, if the pressure deviation and the flow rate deviation are both positive values, the one with the smaller absolute value is selected, and if either one of these deviations is a positive value and the other is a negative value. For example, select the negative value. Furthermore, if both the pressure deviation and the flow rate deviation are negative values, the one with the larger absolute value is selected. In other words, the control logic of the PQ selection unit (12c) determines that the actual supply flow rate Q or the actual supply pressure P exceeds the command values Qi and Pi as a dangerous state, and determines the degree of the danger as the flow rate and the pressure. The solenoid proportional valve (6) can be controlled based on the deviation having the greater degree of danger, judging from the respective deviations.

(Operation of PQS Valve) Next, the operation of the PQS valve (2) having the above-described structure will be described.

For example, when operating the hydraulic cylinder for moving and tightening the mold in the mold clamping device of the injection molding machine which is the main machine, first, the solenoid proportional valve (6) is moved to the supply position and the pump (3 ) To supply the hydraulic oil to the main machine side. At this time, since the pressure command Pi is generally set to a value larger than the required actual supply pressure P until the cylinder reaches the stroke end, the controller (12)
The solenoid proportional valve (6) is opened until the actual supply flow rate Q exceeds the flow rate command value Qi, and the differential pressure across the solenoid proportional valve (6) is made substantially constant by the function of the differential pressure compensating valve (7). In a maintained state,
The position of the spool (6a) is feedback-controlled so that the amount of oil supplied to the main machine side becomes a substantially constant amount corresponding to the flow rate command value Qi (flow rate control mode). As a result, as shown in FIG. 3, the actual amount of supplied oil Q substantially corresponds to the flow rate command value Qi, and the hydraulic cylinder operates at a constant speed.

At this time, the spool position of the solenoid proportional valve (6) is detected by the position sensor (11), and feedback control is performed based on the detection result. Therefore, the control of the solenoid proportional valve (6) and thus the flow rate of the hydraulic oil are performed. The control of is extremely accurate. That is, the non-linearity, hysteresis, variation, etc. of the attraction force characteristic of the solenoid (6b) with respect to the applied current value are completely corrected by the feedback control based on the signal from the position sensor (11). As indicated by the solid line, the static characteristics in flow rate control are greatly improved. Further, since the feedback control is used, the operating speed of the spool (6a) can be significantly increased as compared with the open control, and the response of the flow rate control is also improved.

In addition, in the above flow rate control mode,
Excess hydraulic oil discharged from the pump (3) is bypassed at a constant differential pressure by the function of the differential pressure compensation valve (7).
This allows the discharge pressure of the pump (3) to be kept slightly higher than the load on the main machine side.
Energy saving can be realized by reducing the operation load of (3).

Next, when the hydraulic cylinder of the main engine reaches the stroke end and does not move any further (time t1 in FIG. 3), thereafter, the downstream side supply passage (5b) of the PQS valve (2) is closed. The pressure P gradually rises, and this pressure P
Is detected by the pressure sensor (10) and fed back to the controller (12). When the detected pressure P exceeds the pressure command value Pi (time t2 in the figure), the controller
By the PQ selection section (12c) of (12), the pressure deviation calculation section (12a)
The calculated value, that is, the pressure deviation is selected, and the opening of the solenoid proportional valve (6) is feedback-controlled based on this pressure deviation so that the supply pressure P to the main machine side matches the pressure command value Pi. (Pressure control mode).

At this time, the supply flow rate Q to the main engine side does not immediately become zero, but first, the solenoid proportional valve at the supply position is
By gradually moving the spool (6a) of (6) and narrowing the passage cross section of the hydraulic oil, the supply flow rate Q of the hydraulic oil gradually decreases as shown in the figure (t2 to t3), and the electromagnetic proportional valve
(6) is switched to the stop position, and the supply flow rate Q becomes zero (t3). During this time, since the hydraulic oil is continuously supplied to the hydraulic cylinder, the pressure (≈P) of the hydraulic cylinder becomes maximum when the supply flow rate Q becomes zero. After that, the solenoid proportional valve (6)
When the spool (6a) is further moved to the discharge position and the hydraulic oil is discharged from the hydraulic cylinder, the pressure P decreases to the pressure command value Pi and settles there (t4).
Actually, the supply and stop of the hydraulic oil from the solenoid proportional valve (6) to the main engine side are repeated according to the leakage of the hydraulic oil from the main engine hydraulic circuit.

In such a pressure control mode as well, as in the case of the flow rate control mode, the static characteristics are improved by the feedback control as shown by the solid line in FIG. 4 (b). In the pressure control mode, the proportional solenoid valve (6)
By switching to the discharge position, the minimum control pressure (Pmin) of the supply pressure P to the main machine side can be eliminated and the supply pressure P can be controlled to 0 point.

Therefore, the PQS according to the first embodiment is
According to the valve (2) (hydraulic circuit device), the electromagnetic proportional valve (6) that adjusts the supply flow rate of hydraulic oil to the main hydraulic circuit (1) has a discharge position where the hydraulic oil can be discharged from the main engine side. Along with
A pressure sensor (10) for detecting the pressure P in the supply passage (5b) on the downstream side of the solenoid proportional valve (6) and a position sensor (11) for detecting the spool position of the solenoid proportional valve (6) are provided. , Those sensors
By controlling the spool position based on the signals from (10) and (11), feedback control of the supply flow rate Q and the supply pressure P of the hydraulic oil to the main engine side is performed. The static characteristics such as linearity and hysteresis, and the dynamic characteristics such as response can be greatly improved as compared with the conventional one.

As a result, when the PQS valve (2) is applied to, for example, an injection molding machine, a wide range of molding conditions can be dealt with depending on the shape of the molded product and the difference in the material, and yet high reproducibility is obtained. Therefore, the molding quality can be significantly improved.

Further, since the electromagnetic proportional valve (6) is provided with the discharge position and the opening thereof is feedback-controlled based on the signal from the pressure sensor (10) as described above, the supply to the main engine side is performed. With respect to the pressure P, the minimum control pressure Pmin can be eliminated, and the pressure can be controlled up to zero pressure. This makes it possible to sufficiently meet the requirements of the low-pressure mold clamping process in the injection molding machine.

Moreover, the structure of the PQS valve (2) has a new pressure sensor (10) and position sensor even when compared with the flow control valve device with proportional solenoid type relief valve (see FIG. 6) up to now.
While (11) is required, the pressure proportional valve (8) and the current driver circuit (9) for it, which were required until now, are no longer required, which offsets the cost increase of the sensor (10, 11). It

(Second Embodiment) FIG. 5 shows the structure of a PQS valve (20) (hydraulic circuit device) according to a second embodiment of the present invention. The PQS valve (20) is different from the PQS valve (2) of the first embodiment only in the configuration of the orifice in the downstream pilot passage (15), and the other configurations are the same as those in the first embodiment. Hereinafter, the same members will be denoted by the same reference numerals and the description thereof will be omitted. Then, the PQ of the second embodiment
The S valve (20) has its valve body (7) when the differential pressure compensating valve (7) is opened and closed.
Similar to the first embodiment, appropriate damping is applied to the operation of a) while the closing operation speed of the valve body (7a) is further increased.

That is, in the first embodiment, the orifice (17) of the downstream pilot passage (15) is provided with the safety valve (1
8) and the differential pressure compensating valve (7) as well as a source of differential pressure when functioning as a pilot type relief valve, and at the same time imparting appropriate damping to the operation of the valve body (7a) of the differential pressure compensating valve (7) However, it also works to stabilize the operation of the valve body (7a), but as a result, the valve body is closed when the differential pressure compensating valve (7) is closed.
The operation of (7a) is delayed, and as described above, even if the operating speed of the spool (6a) of the solenoid proportional valve (6) is increased, the response of the flow rate startup to the main machine side does not become so fast. Become.

Explaining this point in detail, in the PQS valve (2) of the first embodiment, in order to increase the flow rate of the hydraulic oil supplied to the main engine side in the flow rate control mode, the flow rate command value Qi is changed. It is necessary to increase the opening of the solenoid proportional valve (6) and increase the flow rate of hydraulic oil from the pump (3) toward the solenoid proportional valve (6). At this time, first, the opening of the solenoid proportional valve (6) in the supply position is increased by a signal from the controller (12), which causes the differential pressure across the solenoid proportional valve (6) to temporarily decrease. The valve element (7a) of the differential pressure compensating valve (7) that receives the upstream and downstream pilot pressures is closed.

At this time, the hydraulic oil flows toward the differential pressure compensating valve (7) in the downstream pilot passage (15), but the valve body (7a) of the differential pressure compensating valve (7) is closed in the first place. Power is
Since it is at most about the biasing force of the spring (7b), if the flow of hydraulic fluid is restricted by the orifice (17) as described above, the closing operation of the valve body (7a) will be delayed,
The hydraulic oil discharged from the pump (3) can be quickly transferred to the solenoid proportional valve.
You can no longer turn to (6). In other words, even if the opening operation of the solenoid proportional valve (6) itself can be speeded up, the flow rate of the hydraulic oil supplied to the main engine side cannot be increased as desired, and there is room for improvement in flow rate response. become.

In consideration of such a transient phenomenon, in the PQS valve (20) of the second embodiment, as shown in the drawing, the PQS valve (20) is provided in the downstream pilot passage (15) rather than the orifice (17) of the first embodiment. First orifice (21) with a large hydraulic oil passage cross section
And a second orifice (22) having a smaller degree of throttling than this first orifice (21), that is, a small passage cross-sectional area, are arranged in series, and the second orifice (22) is bypassed. A check valve (24) is provided in the bypass passage (23) to allow the flow of the hydraulic oil toward the differential pressure compensating valve (7) while blocking the reverse flow thereof.

More specifically, the first orifice (21)
Has a circular cross section with a diameter of about 2 mm, for example, and the second orifice (22) has a circular cross section with a diameter of about 1 mm like the orifice (17) of the first embodiment. When the working oil flows through the downstream pilot passage (15) from the differential pressure compensating valve (7) toward the downstream supply passage (5b), the working oil flows in both the first and second orifices ( It is throttled by 21) and (22), and in particular, the second orifice (22) receives the same passage resistance as in the case of the first embodiment. On the other hand, when the working oil flows through the downstream pilot passage (15) toward the differential pressure compensating valve (7), the working oil flow is relatively weak in the first degree.
The passage resistance is received only from the orifice (21), and the passage speed of the flow becomes relatively high.

As a result, when the opening of the solenoid proportional valve (6) is increased in order to increase the flow rate of the hydraulic oil supplied to the main engine side, the differential pressure compensating valve in the downstream pilot passage (15)
The flow of hydraulic oil flowing toward (7) becomes faster than that in the first embodiment, and the valve body (7a) of the differential pressure compensating valve (7) closes correspondingly faster. Therefore, the delay of the closing operation of the differential pressure compensating valve (7) with respect to the opening operation of the solenoid proportional valve (6) is significantly reduced, and the flow rate of the hydraulic oil from the pump (3) to the solenoid proportional valve (6) immediately increases. Therefore, the responsiveness can be further enhanced when the supply flow rate of the hydraulic oil is increased.

Moreover, when the valve body (7a) of the differential pressure compensating valve (7) is opened, the working oil passing through the downstream pilot passage (15) is supplied with the first and second orifices (21), (22). ), The valve body (7
As in the first embodiment, appropriate damping is given to the operation a).

Further, when the flow rate of the hydraulic oil supplied to the main engine side is reduced, the controller (12) controls the opening of the solenoid proportional valve (6) to be small. At this time, the solenoid proportional valve (6) is controlled. The hydraulic pressure on the upstream side of the
It acts on the valve body (7a) of the differential pressure compensating valve (7) via (14). At this time, the hydraulic oil flows from the differential pressure compensating valve (7) toward the downstream supply passage (5b) in the downstream pilot passage (15) along with the opening operation of the valve body (7a), and the flow of this operating oil Passage resistance is received from both the first and second orifices (21) and (22), but as described above, extremely high upstream pilot pressure acts on the valve body (7a), The opening operation of this valve body (7a) is sufficiently fast,
After all, the response delay does not become a problem when the supply flow rate decreases.

Therefore, the PQS according to the second embodiment
According to the valve (20), the same operational effect as that of the first embodiment can be obtained, and the two orifices (21) and (22) arranged in the downstream pilot passage (15) and the check valve ( While ensuring the stability of the operation of the differential pressure compensation valve (7),
It is possible to further speed up the closing operation of the valve body (7a),
Thereby, the responsiveness can be sufficiently increased even when the flow rate of the hydraulic oil supplied to the main engine side is increased.

As a result, when applied to an injection molding machine, it becomes easier to form a thin-walled molded product as compared with the conventional one.
In addition, the cost can be reduced by shortening the molding cycle. In this regard, thin-walled products made by injection molding may cool and solidify while the injected resin reaches the inside of the mold, and in order to prevent this, a particularly high-speed flow rise response is required. It is particularly effective that the response can be improved as in the PQS valve according to this embodiment.

(Other Embodiments) The present invention is not limited to the structures of the first and second embodiments, but includes various other actual structures. That is, in each of the first and second embodiments, the hydraulic circuit device according to the present invention is one PQS valve (2, 20), but the hydraulic circuit according to the present invention is not necessarily configured as an integrated type composite valve. No need.
Further, the main machine is not limited to the injection molding machine, and can be applied to various mechanical devices having a hydraulic actuator such as a hydraulic cylinder and a hydraulic motor.

Further, the configuration of the controller is not limited to the digital controller (12) of each of the above embodiments, and for example, an analog controller having a similar function may be constructed by using a comparator, an operational amplifier or the like.

Further, the solenoid proportional valve of the present invention is not limited to the above-mentioned respective embodiments, but the A port, the P port, and the T port.
Any throttle valve having a port and an electrically variable throttle amount may be used. That is, it may be a direct acting type in which the spool (6a) is directly pressed by the solenoid (6b), or a pilot type in which the spool is indirectly operated by a small pilot valve. Further, in the case of the pilot type, either a type using a proportional valve as a pilot valve or a type using a servo valve such as a nozzle flapper may be used. Further, in the present invention, since the spool position sensor is provided, it is common to replace the solenoid proportional valve (6) with a servo valve.

[0064]

As described above, according to the hydraulic circuit device (2, 20) of the first aspect of the invention, the solenoid proportional valve (6) is provided in the hydraulic fluid supply passage (5) to the hydraulic actuator. ), And receives pilot pressure from the upstream side and the downstream side of the solenoid proportional valve (6), respectively, and hydraulic fluid is supplied from the supply passage (5a) on the upstream side so that their differential pressure becomes constant. If a differential pressure compensating valve (7) to bypass is installed, the solenoid proportional valve (6)
In addition to the discharge position for discharging the hydraulic fluid from the actuator, the supply passage on the downstream side of the solenoid proportional valve (6)
A pressure sensor (10) that detects the hydraulic fluid pressure of (5b) and a position sensor (11) that detects the spool position of the solenoid proportional valve (6) are provided, and the solenoid proportional valve is based on the output signals from those sensors. Since the spool position (opening degree) of the valve (6) is feedback-controlled, it is possible to control the supply flow rate and pressure of the hydraulic fluid with extremely high precision.

In addition, since the non-linear characteristic of the solenoid can be apparently canceled by the feedback control, the control characteristic of the hydraulic fluid supply flow rate and pressure can be linearized, and the opening / closing speed of the solenoid proportional valve (6) can be made conventional. It is possible to improve the flow rate responsiveness by making it higher than that. Also, a solenoid proportional valve
By switching (6) to the discharge position, the hydraulic fluid can be discharged from the actuator, so that the control pressure can be reduced to zero and the uncontrollable region can be eliminated.

Therefore, when applied to, for example, an injection molding machine, productivity can be improved by shortening the cycle time, molding quality can be greatly improved, and thin-walled molded products can be easily molded. Furthermore, it becomes possible to sufficiently meet the requirements in the low-pressure mold clamping process.

In addition, the pressure proportional valve that was required until now
(8) and the current driver circuit for it are unnecessary,
The cost increase due to the addition of the sensor is offset.

According to the invention of claim 2, the hydraulic circuit device.
Flow rate deviation calculator (12, 20) controller (12)
b), pressure deviation calculation unit (12a), PQ selection unit (12c), etc.
The feedback control of the solenoid proportional valve (6) is performed according to the actual supply state of the hydraulic fluid, and the effect of the invention of claim 1 can be sufficiently obtained.

According to the invention of claim 3, the hydraulic circuit device.
Downstream pilot passage (15) that guides pilot pressure from the downstream side of the solenoid proportional valve (6) to the differential pressure compensation valve (7) of (2, 20)
In addition, the orifice (17) that throttles the flow of hydraulic fluid and the pilot relief valve (18) are provided, so sufficient safety can be obtained even in the unlikely event of failure of the controller (12) or the solenoid proportional valve (6). At the same time, appropriate damping can be applied to the operation of the valve body (7a) of the differential pressure compensating valve (7) to stabilize the operation.

According to the invention of claim 4, as the orifice of the invention of claim 3, first and second orifices (21, 22) having different degrees of throttling are arranged in series, and the degree of throttling is strong. By arranging the check valve (24) in the passage (23) bypassing the second orifice (22), the stability of the operation of the differential pressure compensating valve (7) is ensured while the valve body (7a) is secured. )
It is possible to further improve the flow rate response when increasing the supply amount of the hydraulic fluid to the actuator by accelerating the closing operation of.

According to the invention of claim 5, when the hydraulic actuator is for driving an injection molding machine,
It is extremely effective that the hydraulic circuit device (2, 20) of the present invention can improve the controllability of the operating speed and the operating force thereof, and thus, the molding quality can be significantly improved. In particular, the responsiveness of the supply flow rate of the hydraulic fluid can be improved as in the invention of claim 4 and the control pressure can be reduced to zero as in the invention of claim 1, so that the low pressure mold clamping step is performed. It will be possible to fully meet the requirements of the above and also to reduce the cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a PQS valve according to a first embodiment of the present invention.

FIG. 2 is a view corresponding to FIG. 1 when an electromagnetic proportional valve is in a supply position.

FIG. 3 is a time chart showing changes in the supply flow rate and supply pressure of hydraulic oil when operating the mold clamping cylinder of the injection molding machine.

FIG. 4 is a characteristic diagram showing a correlation between a control signal (current value) input to a solenoid proportional valve and a supply flow rate or a supply pressure of hydraulic oil in comparison with a conventional example.

FIG. 5 is a view corresponding to FIG. 1 according to the second embodiment.

FIG. 6 is a view corresponding to FIG. 1 showing an example of a conventional hydraulic circuit device.

[Explanation of symbols]

1 Main engine hydraulic circuit 2 PQS valve (hydraulic circuit device) 5 supply passages 5a upstream side supply passage 5b Downstream supply passage 6 solenoid proportional valve 6a spool 6b solenoid 7 Differential pressure compensation valve 7a valve body 7b Spring (spring member) 10 Pressure sensor 11 Position sensor (position sensor) 12 Controller 12a Pressure deviation calculation unit 12b Flow rate deviation calculation unit 12c PQ selection section 12d current driver 15 Downstream pilot passage 17,21,22 Orifice 23 Bypass passage 24 Check valve

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3H089 AA22 AA65 AA67 BB14 BB17                       CC01 DA02 DB24 DB45 DB49                       EE36 FF05 FF07 GG02 JJ05                 4F202 AP02 AP06 AR02 AR07 AR14                       CA11 CL18 CL25                 4F206 AP02 AP06 AR02 AR07 AR14                       JA07 JP13 JT02 JT05 JT21

Claims (5)

[Claims] 1. An electromagnetic proportional valve (6) for adjusting a supply flow rate of the hydraulic fluid is provided in a hydraulic fluid supply passage (5) to the hydraulic actuator, and an upstream side of the electromagnetic proportional valve (6). And a liquid provided with a differential pressure compensating valve (7) for bypassing the hydraulic fluid from the upstream supply passage (5a) to the tank (4) so that the differential pressures thereof are received by the pilot pressures from the downstream side and the downstream side, respectively. In the pressure circuit device (2, 20), the solenoid proportional valve (6) has at least a discharge position for discharging hydraulic fluid from the actuator in addition to a supply position for supplying hydraulic fluid to the actuator, and the downstream side Pressure sensor (10) that detects hydraulic fluid pressure in the supply passage (5b) and outputs an electric signal, and position sensor (11) that detects the spool position of the solenoid proportional valve (6) and outputs an electric signal. And receiving signals output from the pressure sensor (10) and the position sensor (11), As the supply flow rate to the supply pressure of the hydraulic fluid to the serial actuator is a control command value,
A hydraulic circuit device comprising: a controller (12) for feedback-controlling the opening of the solenoid proportional valve (6). 2. The hydraulic circuit device (2, 20) according to claim 1, wherein the controller (12) obtains an actual supply flow rate of the hydraulic fluid to the actuator based on a signal from the position sensor (11), This actual supply flow rate is subtracted from the flow rate command value to calculate the flow rate deviation (12b), and the actual supply fluid pressure of the hydraulic fluid to the actuator is calculated based on the signal from the pressure sensor (10). , The pressure deviation calculation unit (12a) for calculating the pressure deviation by subtracting the actual supply hydraulic pressure from the pressure command value, and the deviation having the smaller value of the flow rate deviation and the pressure deviation is selected and selected. Solenoid proportional valve based on deviation (6)
Of the spool (6a) of the solenoid proportional valve (6) so that the target position calculated by the PQ selection unit (12c) is calculated.
A hydraulic circuit device comprising a current driver (12d) for applying a current to b). 3. The hydraulic circuit device (2, 20) according to claim 1 or 2, wherein the differential pressure compensating valve (7) is a spring member (5) for urging the valve body (7a) toward the closing side. 7b), the valve body (7a) receives the pilot pressure from the downstream side of the solenoid proportional valve (6) on the closing side, while the valve body
The pilot pressure from the upstream side of the solenoid proportional valve (6) is received on the side where (7a) opens, and the downstream side that guides the pilot pressure from the downstream side of the solenoid proportional valve (6) to the differential pressure compensation valve (7). An orifice (17) for restricting the flow of hydraulic fluid is provided in the pilot passage (15) of the pilot passage (15), and the pilot passage between the orifice (17) and the differential pressure compensating valve (7) is further provided.
A hydraulic circuit device characterized in that a pilot relief valve (18) is connected to (15). 4. The hydraulic circuit device (20) according to claim 3, wherein the pilot passage (15) on the downstream side has a first orifice (2).
1) and a second orifice (22) with a narrower degree than that
And are arranged in series, and in the passage (23) bypassing the second orifice (22),
While allowing the flow of hydraulic fluid to the differential pressure compensation valve (7),
A hydraulic circuit device comprising a check valve (24) for blocking the reverse flow. 5. The hydraulic circuit device (20) according to any one of claims 1 to 4, wherein the hydraulic actuator is for driving an injection molding machine.