JP3783582B2 - Hydraulic circuit device - Google Patents

Description

[0001]
BACKGROUND 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 a flow rate of hydraulic fluid for appropriately controlling the operating speed and operating force of the actuator. It belongs to the technical field of pressure control.
[0002]
[Prior art]
  Conventionally, as this type of hydraulic circuit device, an electromagnetic proportional valve (hereinafter also simply referred to as a flow proportional valve) for controlling the supply flow rate of hydraulic oil to the actuator and an electromagnetic proportional valve (hereinafter referred to as a flow proportional valve) for adjusting the pressure. There is a flow regulating valve device with an electromagnetic proportional relief valve in which each proportional valve is controlled by a dedicated driver circuit.
[0003]
  In this example, as shown in FIG. 6, a flow rate proportional valve (6) is provided in the hydraulic oil supply passage (5) to the hydraulic actuator of the main hydraulic circuit (1), and this flow rate proportional valve (6 The actuator is connected to the A port on the downstream side of), while the constant displacement pump (3) is connected to the P port on the upstream side. Also, the pilot pressure is received from the upstream side and the downstream side of the flow proportional valve (6), and the hydraulic oil is bypassed from the upstream supply passage (5a) to the T port so that the differential pressure between them is substantially constant. A differential pressure compensation valve (7) is provided.
[0004]
  Furthermore, an orifice (17) is provided in the downstream pilot passage (15) for introducing the pilot pressure from the downstream side of the flow rate proportional valve (6) to the differential pressure compensating valve (7). Connected to the pilot passage (15) between 17) and the differential pressure compensating valve (7) is a pressure proportional valve (8) for relieving the hydraulic oil therefrom and adjusting the downstream pilot pressure. The openings of the flow proportional valve (6) and the pressure proportional valve (8) are controlled by separate current drivers (9, 9).
[0005]
  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, when the hydraulic oil is supplied to the hydraulic cylinder of the main engine, when the hydraulic cylinder strokes, the differential pressure across the flow proportional valve (6) is maintained substantially constant by the differential pressure compensating valve (7). In this state, by controlling the opening degree of the flow rate proportional valve (6), the amount of oil supplied to the hydraulic cylinder can be adjusted to control the operation speed (flow rate control mode). At this time, hydraulic oil discharged from the pump (3) is supplied to the hydraulic cylinder via the P port, the flow proportional valve (6), and the A port, and surplus hydraulic oil is supplied from the differential pressure compensation valve (7). Bypassed to oil tank (4) via T port.
[0006]
  When the cylinder reaches the stroke end, the hydraulic pressure in the downstream supply passage (5b) increases with a sudden increase in load, and when this hydraulic pressure exceeds the set pressure of the pressure proportional valve (8), the pressure proportional The valve (8), the differential pressure compensating valve (7), and the orifice (17) function as a so-called pilot-type electromagnetic proportional relief valve, and further increase in hydraulic pressure is prevented. At that time, the pilot pressure of the downstream pilot passage (15) can be changed by controlling the relief pressure of the pressure proportional valve (8), thereby changing the relief pressure of the differential pressure compensating valve (7), The discharge pressure of 3) and hence the supply pressure to the hydraulic cylinder can be controlled (pressure control mode).
[0007]
[Problems to be solved by the invention]
  However, in the case of the conventional flow rate pressure regulating valve device as described above, the supply flow rate and pressure of hydraulic oil to the actuator both reflect the solenoid characteristics of the solenoid valve (6, 8) as they are. Changes in the flow rate and pressure of the hydraulic oil with respect to the output current value from the driver (9) are nonlinear and have hysteresis (see the broken line graph in FIG. 4). For this reason, it is difficult to obtain sufficient accuracy in the control of the flow rate and pressure of the hydraulic oil, and because the open control without using the electric sensor, the response speed to the change of the command value cannot be increased very much. There's a problem.
[0008]
  Furthermore, especially for the control of the hydraulic oil supply pressure, even if the current value to the pressure proportional valve (8) is reduced to zero, the relief pressure of the differential pressure compensation valve (7) corresponds to the biasing force of the spring member. Therefore, the supply pressure to the actuator cannot be lower than the predetermined pressure. 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 lower pressure than this cannot be performed. Regarding this point, for example, in an injection molding machine, there is a low pressure clamping process set for protection of a mold, and pressure control at a low pressure is also greatly improved.
[0009]
  The present invention has been made in view of such various points, and an object of the present invention is to provide an electromagnetic proportional valve (6) in the hydraulic fluid supply passage (5) to the hydraulic actuator to supply hydraulic fluid. Hydraulic circuit device for controlling flow rate and pressure(2In (0), the control accuracy and responsiveness are improved, and in particular for the supply hydraulic pressure, the minimum control pressure is eliminated and the control range is expanded to zero pressure. Is to provide.
[0010]
[Means for Solving the Problems]
  In order to achieve the object, the hydraulic circuit device of the present invention(20) adds a discharge position for discharging the hydraulic fluid from the actuator to the electromagnetic proportional valve (6) that adjusts the supply flow rate of the hydraulic fluid to the actuator, and supplies the downstream of the electromagnetic proportional valve (6). A pressure sensor (10) for detecting the hydraulic fluid pressure in the passage (5b) and a position sensor (11) for detecting the spool position of the electromagnetic proportional valve (6) are provided, and an electromagnetic signal is generated based on output signals from these sensors. The spool position of the proportional valve (6) is feedback controlled.
[0011]
  Specifically, according to the first aspect of the present invention, an electromagnetic proportional valve (6) for adjusting the flow rate of hydraulic fluid is provided in the hydraulic fluid supply passage (5) from the fixed displacement pump (3) to the hydraulic actuator. In addition, the pilot pressure is received from the upstream and downstream sides of the electromagnetic proportional valve (6), and the differential pressure is actuated from the upstream supply passage (5a) to the tank (4). Hydraulic circuit device provided with differential pressure compensation valve (7) for bypassing the liquid(20) is assumed. The electromagnetic 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.The differential pressure compensation valve (7) Its valve body (7a) Spring member for biasing to the closing side (7b) The valve body (7a) Proportional solenoid valve on the closing side (6) While receiving pilot pressure from the downstream side of the valve (7a) Solenoid proportional valve on the open side (6) It is assumed that the pilot pressure is received from the upstream side.
[0012]
  Further, the electromagnetic proportional valve (6) Differential pressure compensation valve from downstream (7) Downstream pilot passage leading pilot pressure to (15) The first orifice for restricting the flow of hydraulic fluid (twenty one) And a second orifice with a more restrictive degree (twenty two) Are arranged in series, and the second orifice (twenty two) Passage to bypass (twenty three) The differential pressure compensation valve (7) Check valve that allows the flow of hydraulic fluid toward the (twenty four) And the first orifice (twenty one) And second orifice (twenty two) Pilot passage between (15) There is a pilot relief valve (18) Connect.
[0013]
  further,A pressure sensor (10) for detecting the hydraulic fluid pressure in the downstream supply passage (5b) and outputting an electric signal, and a position sensor for detecting the spool position of the electromagnetic proportional valve (6) and outputting an electric signal (11) and the signals output from the pressure sensor (10) and the position sensor (11), respectively, so that the supply flow rate or supply fluid pressure of the hydraulic fluid to the actuator becomes a control command value. And a controller (12) for feedback control of the opening degree of the electromagnetic proportional valve (6).
[0014]
  Thus, the electromagnetic proportional valve (6), the differential pressure compensation valve (7), the pressure sensor (10) and the position sensor (11) are integrally provided to constitute a composite valve having a pressure and flow rate servo function. At the same time, when the controller (12) controls the supply flow rate of the downstream supply passage (5b), the solenoid proportional valve (6) is set to the supply position, and the spool position is continuously changed to change the upstream supply. While adjusting the passage cross-sectional area of the hydraulic fluid flowing from the passage (5a) to the downstream supply passage (5b), when controlling the supply hydraulic pressure of the downstream supply passage (5b), the electromagnetic proportional valve (6) is By switching between the supply position and the discharge position, the downstream supply path (5b) is switched and connected to the upstream supply path (5a) and the discharge path (13).
[0015]
  According to this configuration, during the operation of the actuator, the electromagnetic proportional valve (6) is maintained by the controller (12) in a state where the differential pressure across the electromagnetic proportional valve (6) is maintained substantially constant by the function of the differential pressure compensating valve (7). The spool position of the valve (6) is controlled, thereby adjusting the passage cross-sectional area of the hydraulic oil flowing from the upstream supply passage (5a) to the downstream supply passage (5b) and controlling the supply flow rate to the actuator. (Flow control mode). At that time, the actual spool position of the electromagnetic proportional valve (6) is detected by the position sensor (11), and feedback control is performed based on the detection result, so the flow rate control of the hydraulic fluid is greatly improved in both accuracy and responsiveness. Is done. Further, since the non-linear characteristic of the solenoid can be apparently absorbed by the feedback control, the characteristic of the flow control of the hydraulic fluid can be linearized and hysteresis can be eliminated.
[0016]
  On the other hand, if the actuator reaches the stroke end and becomes almost inoperative, the hydraulic pressure in the downstream supply passage (5b) increases as the load increases, and this is detected by the pressure sensor (10). The controller (12) performs feedback control of the electromagnetic proportional valve (6) according to the detected value. In other words, when the solenoid proportional valve (6) is in the supply position, the solenoid proportional valve (6) is supplied by controlling the opening degree (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 electromagnetic proportional valve (6) is at the discharge position, the amount of discharge from the downstream supply passage (5b) is adjusted, and the downstream supply passage (6) is adjusted by the electromagnetic proportional valve (6). By switching and connecting 5b) to the upstream supply passage (5a) and the discharge passage (13), the spool pressure is finally adjusted so that the hydraulic pressure in the downstream supply passage (5b) can maintain the pressure command value. Control the position. In such a pressure control mode, as in 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 electromagnetic proportional valve (6) to the discharge position and discharging the hydraulic fluid from the actuator as described above, the supply hydraulic pressure to the actuator can be reduced to zero.
[0017]
  Moreover, according to the above configuration, the pressure sensor (10) and the position sensor (11) are newly required as compared with the conventional configuration, while the pressure proportional valve (8) and the current driver circuit therefor are provided. Since it becomes unnecessary, the cost increase by adopting the electric sensor is offset..
[0018]
  In addition,In this configuration, even if the spool (6a) of the electromagnetic proportional valve (6) becomes stuck in the supply position due to electrical failure of the controller (12) or dust of hydraulic fluid, the downstream supply passage (5b ) Fluid pressure exceeds the set pressure of the pilot relief valve (18), the pilot relief valve (18) and the differential pressure compensation valve (7)FirstOrifice (twenty one) Function as a so-called pilot-type relief valve, and an increase in hydraulic pressure in the downstream supply passage (5b) is prevented. Further, when the valve body (7a) of the differential pressure compensating valve (7) is opened and closed, the flow of the hydraulic fluid in the downstream pilot passage (15)First and secondOrifice (twenty one , twenty two), A moderate damping is applied to the operation of the valve body (7a), and stabilization is achieved.
[0019]
  By the way, in the pilot passage (15), an orifice (twenty one , twenty two) To limit the flow of hydraulic fluid, which reduces the operating speed of the valve body (7a) of the differential pressure compensation valve (7). When it is increased, the response may be lowered. That is, when the opening of the electromagnetic proportional valve (6) is increased in order to increase the supply flow rate of the hydraulic fluid to the actuator, the differential pressure across the electromagnetic proportional valve (6) temporarily decreases accordingly, and the differential pressure The valve body (7a) of the compensation valve (7) is closed. At this time, the working fluid flows toward the differential pressure compensating valve (7) in the downstream pilot passage (15), and the valve body (7a) of the differential pressure compensating valve (7) is moved to the closing side. However, in the first place, the force to close the valve body (7a) is about the biasing force of the spring member (7b).twenty one , twenty two), The closing operation of the valve body (7a) of the differential pressure compensating valve (7) is delayed, which causes a response delay in the increase in the supply flow rate to the electromagnetic proportional valve (6). is there.
[0020]
  Considering such a transient phenomenon,Main departureIn the morningAs mentioned above,In the downstream pilot passage (15), the first orifice (21) and the second orifice (22) with a higher degree of restriction are arranged in series, and the second orifice (22) is bypassed. A check valve (24) that allows the flow of hydraulic fluid toward the differential pressure compensation valve (7) while preventing the reverse flow is disposed in the passage (23) that ising.
[0021]
  thisForFor example, when the opening of the electromagnetic proportional valve (6) is increased in order to increase the supply flow rate of the hydraulic fluid to the actuator, the hydraulic fluid flows to the differential pressure compensation valve (7) in the downstream pilot passage (15). Although the flow of the hydraulic fluid passes through the first orifice (21) having a small throttle degree, the second orifice (22) having a strong throttle degree is bypassed. It becomes possible to close the valve element (7a) of the differential pressure compensating valve (7) quickly by relatively reducing the passage resistance, and this can quickly increase the supply flow rate of hydraulic fluid to the actuator. it can.
[0022]
  On the other hand, when reducing the flow rate of the hydraulic fluid supplied to the actuator, the opening of the electromagnetic proportional valve (6) is reduced, but at this time, the hydraulic pressure upstream of the electromagnetic proportional valve (6) increases rapidly. Therefore, an extremely high hydraulic pressure acts on the valve body (7a) of the differential pressure compensating valve (7), and this valve body (7a) is opened. At this time, in the downstream pilot passage (15), the working fluid flows from the differential pressure compensating valve (7) toward the downstream supply passage (5b), and this flow is performed by both the first and second orifices (21, 21). 22) will pass through. However, since the extremely high pilot pressure acts on the valve body (7a) of the differential pressure compensating valve (7) as described above, the flow of hydraulic fluid is restricted in the downstream pilot passage (15). However, the valve element (7a) of the differential pressure compensating valve (7) is opened sufficiently fast, and as a result, the response delay does not become a problem when the supply flow rate decreases, rather, the downstream pilot passage (15) Is sufficiently throttled by the second orifice (22), the stable operation of the differential pressure compensating valve (7) is maintained.
[0023]
  That meansBookIn the invention, the orifice (21, 22) disposed in the downstream pilot passage (15) is limited to the degree that the opening of the valve body (7a) of the differential pressure compensation valve (7) does not impair the responsiveness. On the other hand, the responsiveness can be secured without restricting the closing operation of the valve body (7a), thereby improving the stability and responsiveness of the supply flow rate of the hydraulic fluid to the actuator. Can be compatible.
[0024]
  stillThe hydraulic actuator shall be for driving the injection molding machineIs preferred. That is, in general, in the case of an actuator for an injection molding machine, high reproducibility is required while corresponding to a wide range of molding conditions depending on the shape and material of the molded product. Pressure circuit device(20) is extremely effective in improving the accuracy of the control of the operating speed and the operating force of the actuator, and this can realize a significant improvement in molding quality.
[0025]
  In addition, according to the present invention, the supply pressure of the hydraulic fluid to the actuator can be controlled to be reduced to zero, so that it can sufficiently meet the demand in the low-pressure mold clamping process in the injection molding machine.SaidIn this way, the flow rate of the hydraulic fluid can be increased with good responsiveness, facilitating the molding of thin molded products with an injection molding machine, and the molding cycle can be further shortened. The operational effects of the present invention are extremely effective.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, 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 such as an injection molding machine will be described with reference to the drawings.For convenience of explanation, a reference example having the same basic configuration as that of the embodiment of the present invention will be described first, and then the embodiment of the present invention will be described.
[0027]
  (Reference example)
  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 adjusts its supply flow rate Q and supply pressure P to 1 shows a pressure / flow rate servo valve device (2) (hereinafter referred to as a PQS valve) for controlling the operating speed and operating force of an actuator. The PQS valve (2) includes an A port connected to the main hydraulic circuit (1), a P port connected to the fixed displacement pump (3), and a T port connected to the oil tank (4). And a Y port, an electromagnetic proportional valve (6) for adjusting the supply flow rate is provided in the middle of the hydraulic oil supply passage (5) from the P port to the A port. Receiving the pilot pressure from the upstream (5a) and downstream (5b) supply passages of the valve (6), the oil tank ( A differential pressure compensation valve (7) for bypassing hydraulic oil to 4) is provided.
[0028]
  The PQS valve (2) includes a pressure sensor (10) for detecting the hydraulic pressure P in the supply passage (5b) downstream of the electromagnetic proportional valve (6) and outputting an electrical signal, and an electromagnetic proportional valve. A position sensor (11) for detecting the position of the spool (6a) of (6) and outputting an electrical signal, and signals output from these sensors (10), (11) In response, the position of the spool (6a) of the electromagnetic proportional valve (6) so that the supply flow rate Q and supply pressure P of the hydraulic oil supplied to the main hydraulic circuit (1) become the command values Qi and Pi, respectively. That is, a controller (12) for feedback control of the opening degree of the electromagnetic proportional valve (6) is provided.
[0029]
  Specifically, in the solenoid proportional valve (6), the solenoid (6b) is actuated by a control signal (current) from the controller (12), and the position of the spool (6a) is resisted against the pressing biasing force of the spring (6c). Is switched to one of a supply position for supplying hydraulic oil to the main engine side, a discharge position for discharging hydraulic oil from the main machine side, and a stop position for stopping supply and discharge of the hydraulic oil. In the supply position or the discharge position, the passage cross-sectional area of the hydraulic oil is continuously controlled. Then, as shown in the figure, the spool (6a) of the electromagnetic proportional valve (6) is pressed and urged to the right side of the drawing by the spring (6c) toward the discharge position, and in this discharge position, the electromagnetic proportional valve (6 ) Closes the upstream supply passage (5a) and connects the downstream supply passage (5b) to the discharge passage (13) to return the hydraulic oil on the main engine side to the oil tank (4). Become. At this time, the passage cross-sectional area of the return oil is continuously controlled by the continuous change in the position of the spool (6a).
[0030]
  Further, as shown in FIG. 2, when the solenoid (6b) is actuated, the spool (6a) moves to the left side in the figure against the urging force of the spring (6c) and reaches the supply position. ) Closes the discharge passage (13) and connects the upstream side and the downstream side of the supply passage (5) to supply hydraulic oil discharged from the pump (3) to the main engine side. At this time, the passage cross-sectional area of the hydraulic oil is continuously changed by the continuous change of the position of the spool (6a), and the supply flow rate Q of the hydraulic oil from the pump (3) to the main engine side is continuously controlled. The Further, when the spool (6a) is at a stop position between the supply position and the discharge position, the electromagnetic proportional valve (6) has an upstream and a downstream side of the supply passage (5) and a discharge passage (13), respectively. It comes to close.
[0031]
  Then, the position sensor (11) is attached to the electromagnetic proportional valve (6) .When the spool (6a) of the electromagnetic proportional valve (6) is at the central stop position, the sensor output becomes zero and the spool ( 6a) is at the supply position on the right side of the figure, the positive sensor output increases as the hydraulic oil passage sectional area increases due to the change in the position of the spool (6a), while the spool (6a) ) Is at the discharge position on the left side of the drawing, the negative sensor output decreases as the cross-sectional area of the hydraulic oil increases due to the change in the position of the spool (6a).
[0032]
  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 to a side to be closed by a spring (7b) (spring member), and an upstream supply passage (5a ) Is branched to the branch passage (14) so that the branch passage (14) can be bypassed with respect to the discharge passage (13). That is, the downstream pilot passage (15) branched from the downstream supply passage (5b) is connected to the valve element (7a) of the differential pressure compensation valve (7) on the same side as the spring (7b). The pilot pressure on the downstream side is received by the closing side of the valve body (7a), while the hydraulic pressure (upstream pilot pressure) of the upstream supply passage (5a) is received on the opposite side via the branch passage (14). It is received on the opening side of the valve body (7a).
[0033]
  The differential pressure compensating valve (7) has a spring (7b) in which the pressing force acting on the valve body (7a) by the upstream pilot pressure is larger than the pressing force acting on the valve body (7a) by the downstream pilot pressure. ), The hydraulic oil in the upstream supply passage (5a) is bypassed to the discharge passage (13) via the branch passage (14). If the upstream pilot pressure is thereby reduced, the valve body (7a) is closed, the hydraulic oil bypass is interrupted, and the upstream pilot pressure rises again. The opening / closing operation of the valve body (7a) is repeated, so that the differential pressure across the electromagnetic proportional valve (6) is maintained substantially constant. In this way, the differential pressure across the electromagnetic proportional valve (6) is compensated to be constant, so that the degree of opening of the electromagnetic 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-sectional area of the hydraulic oil has a certain correspondence with the actual supply flow rate, and this makes it possible to obtain the actual supply flow rate based on the spool position.
[0034]
  The downstream pilot passage (15) is provided with an orifice (17) for restricting the flow of hydraulic oil, and a branch passage (15a) between the orifice (17) and the differential pressure compensating valve (7). Are connected to each other, and a safety valve (18) (pilot relief valve) is disposed in the branch passage (15a). The safety valve (18) is opened when the hydraulic pressure of the branch passage (15a) becomes higher than the set pressure of the spring, and the hydraulic pressure of the downstream pilot passage (15) is relieved through 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) is lowered to open the differential pressure compensating valve (7). Then, by the opening operation of the differential pressure compensation 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) has a function of releasing the hydraulic pressure as a so-called pilot-type relief valve in cooperation with the safety valve (18) when the oil pressure in the supply passage (5) rises excessively. is doing.
[0035]
  The orifice (17) has, for example, a circular cross section with a diameter of about 1 mm, and by restricting the flow of hydraulic oil in the downstream pilot passage (15) to provide passage resistance, the differential pressure compensation valve (7 Appropriate damping is applied to the opening and closing operation of the valve body (7a) to stabilize the operation of the differential pressure compensation valve (7), thereby reducing the flow rate and pressure of hydraulic oil in the supply passage (5). ShakeMoveIt also has a function to suppress.
[0036]
  The controller (12) is a digital controller that reads and executes a control program electronically stored in a memory (not shown) by a CPU at predetermined time intervals, and based on a signal from the pressure sensor (10), In the same manner as the pressure deviation calculation unit (12a) that calculates the pressure deviation by calculating the actual supply pressure P (actual supply pressure) of hydraulic oil to the main engine side and subtracting this from the pressure command value Pi (target pressure) Based on the signal from the position sensor (11), the actual supply flow rate Q (actual supply flow rate) of the hydraulic fluid to the main engine is obtained, and this is subtracted from the flow rate command value Qi (target flow rate) to obtain the flow rate deviation. And a flow rate deviation calculating section (12b) for calculating. In other words, the memory of the controller (12) stores a control program for realizing the functions of the pressure deviation calculation unit (12a) and the flow rate deviation calculation unit (12b) in software.
[0037]
  Further, the controller (12) compares the pressure deviation and the flow rate deviation calculated by the pressure deviation calculation unit (12a) and the flow rate deviation calculation unit (12b), respectively, and calculates the smaller one of them. There is provided a PQ selection section (12c) for selecting and calculating the target opening of the electromagnetic proportional valve (6), that is, the position of the spool (6a) by the so-called PID control law based on the selected deviation. Then, the current driver circuit (12d) receiving the output from the PQ selector (12c) moves to the target opening of the solenoid proportional valve (6) with respect to the solenoid (6b) of the solenoid proportional valve (6). A current is applied for this purpose.
[0038]
  The calculation process by the PQ selection unit (12c) is also realized by executing a control program stored in the memory, and selects the smaller one of the pressure deviation and the flow deviation. . Specifically, if both the pressure deviation and the flow deviation are positive values, the smaller absolute value is selected, and if one of these deviations is a positive value and the other is a negative value, For example, select a negative value. Furthermore, if the pressure deviation and the flow deviation are both negative values, 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 danger of the flow rate and the pressure. Judging from the respective deviations, the electromagnetic proportional valve (6) can be controlled based on the deviation with the greater degree of danger.
[0039]
  (PQS valve operation)
  Next, the operation of the PQS valve (2) configured as described above will be described.
[0040]
  For example, when operating the hydraulic cylinder that moves and tightens the mold in the mold clamping device of the main injection molding machine, first move the electromagnetic proportional valve (6) to the supply position and discharge from the pump (3). Is supplied to the main engine. At this time, until the cylinder reaches the stroke end, generally, the pressure command Pi is set to a value larger than the necessary actual supply pressure P. Therefore, the controller (12) allows the actual supply flow rate Q to be set to the flow rate command value Qi. The solenoid proportional valve (6) is opened until the pressure exceeds, and the oil supplied to the main engine is maintained in a state where the differential pressure across the solenoid proportional valve (6) is maintained substantially constant by the function of the differential pressure compensating valve (7). The position of the spool (6a) is feedback controlled so that the amount 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 supply oil amount Q roughly corresponds to the flow rate command value Qi, and the hydraulic cylinder is operated at a constant speed.
[0041]
  At that time, the spool position of the electromagnetic 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 electromagnetic proportional valve (6) and the control of the flow rate of hydraulic oil are performed. Extremely accurate. That is, the non-linearity, hysteresis, variation, etc. of the attractive force characteristics of the solenoid (6b) with respect to the applied current value are completely corrected by feedback control based on the signal from the position sensor (11). As indicated by the solid line, the static characteristics in the flow rate control are greatly improved. In addition, since the feedback control is performed, the operating speed of the spool (6a) can be remarkably increased compared to the open control, thereby improving the response of the flow rate control.
[0042]
  In addition, in the flow rate control mode, surplus of the hydraulic fluid discharged from the pump (3) is bypassed with a constant differential pressure by the function of the differential pressure compensation valve (7). Since the discharge pressure of 3) can be kept slightly higher than the load on the main engine side, the operation load of the pump (3) can be reduced and energy saving can be realized.
[0043]
  Next, when the hydraulic cylinder of the main engine reaches the stroke end and does not move any more (time t1 in FIG. 3), the pressure P in the downstream supply passage (5b) in the PQS valve (2) is then increased. The pressure P gradually increases, and the 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 PQ selection unit (12c) of the controller (12) selects the calculation value by the pressure deviation calculation unit (12a), that is, the pressure deviation. Then, based on this pressure deviation, the opening degree of the electromagnetic proportional valve (6) is feedback-controlled so that the supply pressure P to the main engine side coincides with the pressure command value Pi (pressure control mode).
[0044]
  At that time, the supply flow rate Q to the main engine side does not immediately become zero, but first, the spool (6a) of the electromagnetic proportional valve (6) in the supply position gradually moves to reduce the passage cross-sectional area of the hydraulic oil. As a result, the supply flow rate Q of the hydraulic oil gradually decreases (t2 to t3) as shown in the figure, and the electromagnetic proportional valve (6) is switched to the stop position, so that the supply flow rate Q becomes zero (t3). During this time, since the hydraulic oil continues to be supplied to the hydraulic cylinder, the pressure (≈P) of the hydraulic cylinder becomes maximum when the supply flow rate Q becomes zero. After that, when the spool (6a) of the electromagnetic proportional valve (6) is further moved and switched 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 here. (T4). Actually, the supply and stop of the hydraulic oil from the electromagnetic proportional valve (6) to the main engine side are repeated according to the leakage of the hydraulic oil from the main engine hydraulic circuit.
[0045]
  In such a pressure control mode, as in the flow rate control mode, the static characteristics are improved by feedback control as shown by a solid line in FIG. Further, by switching the electromagnetic proportional valve (6) to the discharge position as described above in the pressure control mode, the supply pressure P is controlled to 0 point by eliminating the minimum control pressure (Pmin) of the supply pressure P to the main engine side. be able to.
[0046]
  So thisReference exampleAccording to the PQS valve (2) (hydraulic circuit device), the hydraulic proportional valve (6) that adjusts the supply flow rate of hydraulic oil to the main hydraulic circuit (1) can be discharged from the main engine side. In addition to adding a position, a pressure sensor (10) for detecting the pressure P of the supply passage (5b) on the downstream side of the electromagnetic proportional valve (6), and a position sensor for detecting the spool position of the electromagnetic proportional valve (6) 11), and the spool position is controlled based on signals from the sensors (10) and (11), so that the supply flow rate Q and the supply pressure P of hydraulic oil to the main engine are feedback-controlled. Therefore, the controllability, that is, the static characteristics such as linearity and hysteresis, and the dynamic characteristics such as responsiveness can be greatly improved as compared with the prior art.
[0047]
  As a result, when the PQS valve (2) is applied to, for example, an injection molding machine, high reproducibility can be obtained while supporting a wide range of molding conditions depending on the shape and material of the molded product. Therefore, a significant improvement in molding quality can be realized.
[0048]
  Further, as described above, the electromagnetic proportional valve (6) is provided with a discharge position, and its opening degree is feedback controlled based on a signal from the pressure sensor (10). The minimum control pressure Pmin can be eliminated, and control up to zero pressure can be achieved. This makes it possible to sufficiently meet demands such as a low pressure clamping process in an injection molding machine.
[0049]
  Moreover, the PQS valve (2) has a new pressure sensor (10) and position sensor (11) compared to the conventional flow rate regulating valve device with proportional electromagnetic relief valve (see FIG. 6). On the other hand, since the pressure proportional valve (8) and the current driver circuit (9) for the pressure proportional valve (8), which have been necessary in the past, are unnecessary, the increase in cost of the sensors (10, 11) is offset.
[0050]
  (Execution formstate)
  FIG. 5 shows an embodiment of the present invention.StateThe structure of the PQS valve (20) (hydraulic circuit device) is shown. This PQS valve (20)Reference exampleThe PQS valve (2) is different from the PQS valve (2) only in the configuration of the orifice in the downstream pilot passage (15).Reference exampleIn the following, the same members are denoted by the same reference numerals, and description thereof is omitted. And this implementationStateThe PQS valve (20) is the same as the valve body (7a) when the differential pressure compensating valve (7) is opened or closed.Reference exampleIn the same manner as described above, only the closing operation speed of the valve body (7a) is further increased while applying appropriate damping.
[0051]
  That is, the aboveReference exampleIn this case, the orifice (17) of the downstream pilot passage (15) is a differential pressure generation source when functioning as a pilot type relief valve together with the safety valve (18) and the differential pressure compensation valve (7). Appropriate damping is given to the operation of the valve body (7a) of the pressure compensation valve (7), and the operation of the valve body (7a) is also stabilized, but as a result, the differential pressure compensation valve When the closing operation of (7) is closed, the operation of the valve body (7a) becomes slow, and as described above, even if the operating speed of the spool (6a) of the electromagnetic proportional valve (6) is increased, the flow rate to the main engine is increased. This will cause the response to not be very fast.
[0052]
  Explaining this point in detail,Reference exampleIn the PQS valve (2), in order to increase the supply flow rate of hydraulic oil to the main engine in the flow rate control mode, the flow rate command value Qi is changed to increase the opening of the electromagnetic proportional valve (6). It is necessary to increase the flow rate of hydraulic fluid from the pump (3) to the electromagnetic proportional valve (6). At this time, first, the opening degree of the electromagnetic proportional valve (6) in the supply position is increased by a signal from the controller (12), whereby the differential pressure across the electromagnetic proportional valve (6) is temporarily reduced. Then, the valve body (7a) of the differential pressure compensating valve (7) that receives the upstream and downstream pilot pressures is closed.
[0053]
  At this time, the hydraulic oil flows toward the differential pressure compensation valve (7) in the downstream pilot passage (15), but the force to close the valve body (7a) of the differential pressure compensation valve (7) is Since it is at most about the urging force of the spring (7b), if the flow of hydraulic oil is restricted by the orifice (17) as described above, the closing operation of the valve body (7a) is delayed, and the pump ( The hydraulic fluid discharged from 3) cannot be quickly directed to the electromagnetic proportional valve (6). In other words, even if the speed of the solenoid proportional valve (6) opening operation itself can be increased, the flow rate of hydraulic oil supplied to the main engine cannot be increased as intended, leaving room for improvement in the flow rate response. become.
[0054]
  Considering such a transient phenomenon, this embodimentStateIn the PQS valve (20), as shown in the figure, the downstream pilot passage (15)Reference exampleThe first orifice (21) having a hydraulic oil passage cross-sectional area larger than that of the first orifice (17), and the second orifice (the passage cross-sectional area smaller than that of the first orifice (21), that is, the passage cross-sectional area is smaller). 22) are arranged in series, and the bypass passage (23) bypassing the second orifice (22) allows the flow of hydraulic oil toward the differential pressure compensating valve (7), while the reverse A check valve (24) was installed to block the flow.
[0055]
  More specifically, the first orifice (21) has, for example, a circular cross section with a diameter of about 2 mm, and the second orifice (22)Reference exampleThe orifice (17) has a circular cross section with a diameter of about 1 mm. When the hydraulic oil flows through the downstream pilot passage (15) from the differential pressure compensation valve (7) toward the downstream supply passage (5b), the flow of the hydraulic oil flows in both the first and second orifices ( 21) and (22), and in particular by the second orifice (22)Reference exampleThe same pass resistance as in the case of. On the other hand, when the hydraulic oil flows in the downstream pilot passage (15) toward the differential pressure compensation valve (7), the flow of the hydraulic oil passes through only the first orifice (21) having a relatively small throttle degree. The flow velocity of the flow is relatively high.
[0056]
  As a result, when the opening of the solenoid proportional valve (6) is increased in order to increase the supply flow rate of hydraulic oil to the main engine, the downstream pilot passage (15) moves toward the differential pressure compensation valve (7). The flow of hydraulic oilReference exampleAccordingly, the valve body (7a) of the differential pressure compensating valve (7) closes at a higher speed. For this reason, the delay in the closing operation of the differential pressure compensation valve (7) relative to the opening operation of the electromagnetic proportional valve (6) is greatly reduced, and the flow rate of hydraulic oil from the pump (3) to the electromagnetic proportional valve (6) is immediately increased. Therefore, the responsiveness can be further improved when the supply flow rate of the hydraulic oil is increased.
[0057]
  In addition, when the valve body (7a) of the differential pressure compensating valve (7) is opened, the hydraulic oil passing through the downstream pilot passage (15) is relative to the first and second orifices (21), (22). Therefore, a moderate damping is given to the operation of the valve body (7a).Reference exampleIt is the same.
[0058]
  Also, when reducing the supply flow rate of hydraulic fluid to the main engine side, the controller (12) controls the opening of the electromagnetic proportional valve (6) to be small, but at this time, the upstream side of the electromagnetic proportional valve (6) is controlled. The hydraulic pressure of the pressure increases rapidly and acts on the valve body (7a) of the differential pressure compensating valve (7) via the branch path (14). At this time, the hydraulic oil flows in the downstream pilot passage (15) from the differential pressure compensation valve (7) toward the downstream supply passage (5b) with the opening operation of the valve body (7a), and the flow of the hydraulic oil is Although the passage resistance is received from both the first and second orifices (21) and (22), as described above, the extremely high upstream pilot pressure acts on the valve body (7a). The opening operation of the valve body (7a) becomes sufficiently fast, and as a result, response delay does not become a problem when the supply flow rate is reduced.
[0059]
  Therefore, this implementationStateAccording to the PQS valve (20),Reference exampleIn addition, the differential pressure compensation valve (7) can be obtained by two orifices (21), (22) and a check valve (24) arranged in the downstream pilot passage (15). The valve body (7a) can be closed more quickly while ensuring the stability of the operation of the engine, which improves the responsiveness even when the flow rate of hydraulic oil supplied to the main engine is increased. Can be high enough.
[0060]
  As a result, when applied to an injection molding machine, it becomes easier to form a thin molded product as compared with the prior art, and the cost can be reduced by shortening the molding cycle. In this regard, thin-walled molded products 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 rate rise response is required. The ability to improve the responsiveness like the PQS valve according to this embodiment is particularly effective.
[0061]
  (Other embodiments)
  The present invention is the above embodiment.StateIt is not limited to the configuration, and includes various other actual configurations. That is, the aboveReference examples and embodimentsHowever, in all cases, an example of an injection molding machine is given as a main machine, but the main machine is not limited to an injection molding machine, and can be applied to various mechanical devices having a hydraulic actuator such as a hydraulic cylinder or a hydraulic motor. .
[0062]
  Further, the configuration of the controller is not limited to the digital controller (12) of each of the above embodiments, and an analog controller having the same function may be configured using, for example, a comparator or an operational amplifier.
[0063]
  Furthermore, the electromagnetic proportional valve of the present invention isRealThe throttle valve is not limited to that of the embodiment, and any throttle valve having an A port, a P port, and a T port with an electrically variable throttle amount may be used. That is, 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 may be used. 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. In the present invention, since the spool position sensor is provided, the electromagnetic proportional valve (6) is generally read as a servo valve.
[0064]
【The invention's effect】
  As described above, the hydraulic circuit device according to the invention of claim 1(2According to (0), an electromagnetic proportional valve (6) is interposed in the hydraulic fluid supply passage (5) to the hydraulic actuator, and pilot pressure is received from the upstream side and the downstream side of the electromagnetic proportional valve (6), respectively. When the differential pressure compensation valve (7) for bypassing the hydraulic fluid from the upstream supply passage (5a) is provided so that the differential pressure becomes constant, the electromagnetic proportional valve (6) is operated from the actuator. A pressure sensor (10) for detecting the hydraulic fluid pressure in the supply passage (5b) on the downstream side of the electromagnetic proportional valve (6) and a spool position of the electromagnetic proportional valve (6), as well as adding a discharge position for discharging the liquid And a position control (11) for detecting the feedback, and the spool position (opening) of the electromagnetic proportional valve (6) is feedback controlled based on the output signals from these sensors. The pressure can be controlled with extremely high accuracy.
[0065]
  In addition, the non-linear characteristics of the solenoid can be apparently canceled by feedback control, so that the control characteristics of the supply flow rate and pressure of the hydraulic fluid can be linearized, and the opening / closing speed of the electromagnetic proportional valve (6) is higher than before. Thus, the flow response can be improved. Further, if the electromagnetic proportional valve (6) is switched to the discharge position, the hydraulic fluid can be discharged from the actuator, so the control pressure can be lowered to zero and the uncontrollable area can be eliminated.
[0066]
  Therefore, when applied to, for example, an injection molding machine, productivity can be improved by shortening the cycle time, a significant improvement in molding quality can be realized, and molding of a thin molded product is facilitated. It is possible to fully meet the demands in the low-pressure mold clamping process.
[0067]
  In addition, the pressure proportional valve (8) and the current driver circuit required for it are no longer necessary..
[0068]
  AlsoHydraulic circuit device(2The orifice that restricts the flow of hydraulic fluid to the downstream pilot passage (15) that guides the pilot pressure from the downstream side of the electromagnetic proportional valve (6) to the differential pressure compensation valve (7) of (0)twenty one , twenty two) And the pilot relief valve (18), it is possible to obtain sufficient safety in the event of a failure of the controller (12) or the electromagnetic proportional valve (6), and the differential pressure compensation valve (7). Appropriate damping is applied to the operation of the valve body (7a), and the operation can be stabilized.
[0069]
  further,in frontRecordingLifisu(twenty one , twenty two)The first and second orifices (21, 22) having different degrees of restriction are arranged in series, and a check valve (23) bypasses the second orifice (22) having a strong degree of restriction. 24) is provided, the operation of the differential pressure compensation valve (7) is secured and the closing speed of the valve body (7a) is increased to increase the amount of hydraulic fluid supplied to the actuator. The flow responsiveness can be further improved when.
[Brief description of the drawings]
FIG. 1 of the present inventionReference exampleIt is a figure which shows the structure of the PQS valve which concerns on.
FIG. 2 is a view corresponding to FIG. 1 when the electromagnetic proportional valve is in a supply position.
FIG. 3 is a time chart showing changes in hydraulic oil supply flow rate and supply pressure when operating a mold clamping cylinder of an injection molding machine.
FIG. 4 is a characteristic diagram showing a correlation between a control signal (current value) input to an electromagnetic proportional valve and a supply flow rate or supply pressure of hydraulic oil in comparison with a conventional example.
[Figure 5]Of the present inventionImplementationStateFIG. 2 is a diagram corresponding to FIG. 1.
FIG. 6 is a view corresponding to FIG. 1 showing an example of a conventional hydraulic circuit device.
[Explanation of symbols]
1 Main machine hydraulic circuit
20          PQS valve (hydraulic circuit device)
5 Supply passage
5a Upstream supply passage
5b Downstream supply passage
6 Solenoid proportional valve
6a spool
6b Solenoid
7 Differential pressure compensation valve
7a Disc
7b Spring (spring member)
10 Pressure sensor
11 Position sensor (position sensor)
12 Controller
12a Pressure deviation calculator
12b Flow rate deviation calculator
12c PQ selector
12d current driver
15 Downstream pilot passage
21,22 Orifice
23 Bypass passage
24 Check valve

Claims (1)

An electromagnetic proportional valve (6) for adjusting the supply flow rate of the hydraulic fluid is provided in the hydraulic fluid supply passage (5) from the fixed displacement pump (3) to the hydraulic actuator, and the electromagnetic proportional valve (6) A differential pressure compensation valve (7) that receives the pilot pressure from the upstream side and the downstream side of the tank and bypasses the hydraulic fluid from the upstream supply passage (5a) to the tank (4) so that the differential pressure is constant. In the provided hydraulic circuit device (20 ),
The electromagnetic 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,
The differential pressure compensation valve (7) is downstream of the valve element to urge the (7a) close to the side has a spring member (7b), the solenoid proportional valve the valve element (7a) is closed side (6) While receiving the pilot pressure from the side, it receives the pilot pressure from the upstream side of the solenoid proportional valve (6) on the side where the valve body (7a) opens ,
In the downstream pilot passage (15) for introducing the pilot pressure from the downstream side of the electromagnetic proportional valve (6) to the differential pressure compensating valve (7) , a first orifice (21) for restricting the flow of hydraulic fluid and The second orifice (22) having a high degree of throttling is arranged in series, and the hydraulic fluid flowing toward the differential pressure compensating valve (7) is passed through the passage (23) bypassing the second orifice (22) . A check valve (24) is provided that allows flow while preventing reverse flow ,
Further, a pilot relief valve (18) is connected to the pilot passage (15) between the first orifice (21) and the second orifice (22) ,
A pressure sensor (10) for detecting the hydraulic fluid pressure in the downstream supply passage (5b) and outputting an electrical signal;
A position sensor (11) for detecting the spool position of the electromagnetic proportional valve (6) and outputting an electrical signal;
The electromagnetic proportional valve (6) receives the signals output from the pressure sensor (10) and the position sensor (11), respectively, so that the supply flow rate or supply pressure of hydraulic fluid to the actuator becomes a control command value. ) And a controller (12) for feedback control of the opening degree of
The electromagnetic proportional valve (6), the differential pressure compensation valve (7), the pressure sensor (10) and the position sensor (11) are integrally provided to constitute a composite valve having a pressure and flow servo function,
When the controller (12) controls the supply flow rate of the downstream supply passage (5b), the solenoid proportional valve (6) is set to the supply position, and the spool position is continuously changed to change the upstream supply passage ( While adjusting the passage cross-sectional area of hydraulic fluid flowing from 5a) to the downstream supply passage (5b), when controlling the supply hydraulic pressure of the downstream supply passage (5b), supply the electromagnetic proportional valve (6). Switching between the position and the discharge position, the downstream supply passage (5b) is configured to switch and connect to the upstream supply passage (5a) and the discharge passage (13). Pressure circuit device .

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