JP2006132783A - Hydraulic circuit device - Google Patents

Abstract

A hydraulic circuit device (2, which is provided with an electromagnetic proportional valve (6) in a hydraulic oil supply passage (5) to a main machine hydraulic circuit (1) to adjust the hydraulic oil supply flow rate and pressure. In 20), while controlling the increase in cost, the controllability of the supply flow rate and pressure of hydraulic oil is improved, and in particular, the controllable area for pressure is expanded to zero.
A solenoid proportional valve (6) is provided with a supply position for supplying hydraulic oil to the main machine side, a discharge position for discharging hydraulic oil from the main machine side, and a stop position for stopping supply and discharge of hydraulic oil. A pressure sensor (10) for detecting the pressure of hydraulic oil in the downstream supply passage (5b) and a position sensor (11) for detecting the spool position (opening) of the electromagnetic proportional valve (6) are provided. 10) and a solenoid proportional valve (6) by a digital controller (12) so that the supply flow rate Q or supply pressure P of hydraulic oil to the main engine side becomes the command values Qi, Pi based on signals from the position sensor (11). ) Feedback control.
[Selection] Figure 1

Description

  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.

  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.

  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.

  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).

  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.

  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).

  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.

  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.

  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. In the hydraulic circuit device (2, 20) that controls the flow rate and pressure, the control accuracy and responsiveness are improved, and the control range is reduced to zero pressure by eliminating the minimum control pressure especially for the supply hydraulic pressure. In addition, it is to provide a valve structure that can suppress an increase in cost.

  In order to achieve the above object, the hydraulic circuit device (2, 20) of the present invention discharges 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. A position sensor that detects the spool position of the solenoid proportional valve (6) and a pressure sensor (10) that detects the hydraulic fluid pressure in the supply passage (5b) downstream of the solenoid proportional valve (6) (11) is provided, and the spool position of the electromagnetic proportional valve (6) is feedback-controlled based on the output signals from these sensors.

  Specifically, in the first aspect of the invention, an electromagnetic proportional valve (6) for adjusting the supply flow rate of the hydraulic fluid is interposed in the hydraulic fluid supply passage (5) to the hydraulic actuator, and the electromagnetic proportional valve A differential pressure compensation valve that receives the pilot pressure from the upstream side and the downstream side of (6) and bypasses the hydraulic fluid from the upstream supply passage (5a) to the tank (4) so that the differential pressure between them is constant. The hydraulic circuit device (2, 20) provided with (7) 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, and the downstream supply passage (5b) A pressure sensor (10) for detecting the hydraulic pressure 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; and the pressure sensor (10 ) And the position sensor (11), respectively, and the opening of the electromagnetic proportional valve (6) is adjusted 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.

  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, and thereby the supply flow rate to the actuator is controlled (flow rate 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.

  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 solenoid proportional valve (6) is at the discharge position, the hydraulic pressure in the supply passage (5b) is finally adjusted by adjusting the discharge amount from the downstream supply passage (5b). The spool position is controlled so that the pressure command value can be maintained. 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.

  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 due to the adoption of the electric sensor is offset.

  In the invention of claim 2, as the controller (12) of the hydraulic circuit device (2, 20), the actual supply flow rate of the working fluid to the actuator is obtained based on the signal from the position sensor (11), and this actual supply Based on the signal from the flow rate deviation calculation unit (12b) that calculates the flow rate deviation by subtracting the flow rate from the flow rate command value, and the signal from the pressure sensor (10), the actual supply fluid pressure to the actuator is obtained. A pressure deviation calculation unit (12a) that calculates a pressure deviation by subtracting the supply hydraulic pressure from the pressure command value, and selects a deviation of the smaller one of the flow rate deviation and the pressure deviation, and based on the selected deviation A PQ selector (12c) for calculating a target spool position of the electromagnetic proportional valve (6), and a spool (6a) of the electromagnetic proportional valve (6) so as to be the target position calculated by the PQ selector (12c). A current driver (12d) for applying current to the solenoid (6b) And it formed.

  In this configuration, the flow deviation between the actual supply flow rate of the hydraulic fluid and the flow command value is calculated by the flow rate deviation calculation unit (12b), and the actual supply hydraulic pressure of the hydraulic fluid is calculated by the pressure deviation calculation unit (12a). A pressure deviation from the pressure command value is calculated. When the actual supply flow rate or the actual supply hydraulic pressure exceeds the control command value, the larger one is exceeded, and if both are less than the command value, the one closer to the command value is determined by the PQ selection unit (12c). Selected. That is, the PQ selection unit (12c) determines that it is dangerous to exceed the command value of pressure or flow rate, and determines the degree of danger from the respective deviations of flow rate and pressure, thereby increasing the degree of danger. By selecting the larger deviation, the effect of the invention of claim 1 is realized.

  In the invention of claim 3, the differential pressure compensating valve (7) of the hydraulic circuit device (2, 20) has a spring member (7 b) that biases the valve body (7 a) toward the closing side, and the valve The body (7a) receives the pilot pressure from the downstream side of the proportional solenoid valve (6) on the closing side, while the valve body (7a) opens the pilot pressure from the upstream side of the solenoid proportional valve (6) And Then, an orifice (17) for restricting the flow of hydraulic fluid is disposed in the pilot passage (15) on the downstream side that guides the pilot pressure from the downstream side of the electromagnetic proportional valve (6) to the differential pressure compensation valve (7), Further, the pilot relief valve (18) is connected to the pilot passage (15) between the orifice (17) and the differential pressure compensating valve (7).

  In this configuration, even if the spool (6a) of the electromagnetic proportional valve (6) becomes stuck at the supply position due to an electrical failure of the controller (12) or dust of hydraulic fluid, the downstream supply passage (5b ) Exceeds the set pressure of the pilot relief valve (18), the pilot relief valve (18), the differential pressure compensation valve (7) and the orifice (17) function as a so-called pilot type relief valve, 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) receives a passage resistance from the orifice (17), so that the valve body Appropriate damping is given to the operation of (7a), and stabilization is achieved.

  By the way, when the orifice (17) is arranged in the pilot passage (15) and the flow of the hydraulic fluid is restricted in this way, this reduces the operating speed of the valve body (7a) of the differential pressure compensating valve (7). As a result, when the supply flow rate of the hydraulic fluid to the actuator 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 urging force of the spring member (7b), and when the flow of hydraulic fluid is restricted by the orifice (17) as described above, As a result, 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).

  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, the first pilot passage (15) is provided with the first An orifice (21) and a second orifice (22) having a higher degree of restriction are arranged in series, and a differential pressure compensating valve (7) is provided in a passage (23) bypassing the second orifice (22). A check valve (24) that allows the flow of the hydraulic fluid toward) but prevents the reverse flow is provided.

  In this configuration, for 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 in the differential pressure compensation valve (15) in the downstream pilot passage (15). 7) Although the flow of the working fluid passes through the first orifice (21) having a small throttle degree, the second orifice (22) having a strong throttle degree is to be bypassed. Therefore, it becomes possible to quickly close the valve body (7a) of the differential pressure compensating valve (7) by relatively reducing the passage resistance, thereby rapidly increasing the supply flow rate of the hydraulic fluid to the actuator. Can be made.

  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.

  That is, in the present invention, the opening operation of the valve body (7a) of the differential pressure compensating valve (7) is limited to the extent that the responsiveness is not impaired by the orifices (21, 22) arranged in the downstream pilot passage (15). On the other hand, responsiveness can be ensured without restricting the closing operation of the valve body (7a), thereby improving the stability and responsiveness of the supply flow rate of hydraulic fluid to the actuator. Can be compatible at a higher level.

  In the invention of claim 5, the hydraulic actuator is for driving an injection molding machine. 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. It is extremely effective that the pressure circuit device (2, 20) can improve the accuracy of controlling the operating speed and the operating force of the actuator, and this can realize a significant improvement in molding quality.

  In addition, according to the present invention, since the supply pressure of the hydraulic fluid to the actuator can be controlled to zero, it is possible to sufficiently meet the requirements in the low-pressure mold clamping process in the injection molding machine. Since the supply flow rate of the hydraulic fluid can be increased with good responsiveness as in the invention of claim 4, it becomes easy to form a thin molded product by the injection molding machine, and further, the molding cycle can be shortened. From this point of view, the effects of the present invention are extremely effective.

  As described above, according to the hydraulic circuit device (2, 20) according to the invention of claim 1, the electromagnetic proportional valve (6) is provided in the hydraulic fluid supply passage (5) to the hydraulic actuator. In addition, differential pressure compensation that receives the pilot pressure from the upstream side and the downstream side of the electromagnetic proportional valve (6) and bypasses the hydraulic fluid from the upstream supply passage (5a) so that the differential pressure thereof is constant. When providing the valve (7), a discharge position for discharging the hydraulic fluid from the actuator is added to the electromagnetic proportional valve (6), and the operation of the supply passage (5b) on the downstream side of the electromagnetic proportional valve (6) A pressure sensor (10) for detecting the hydraulic pressure and a position sensor (11) for detecting the spool position of the electromagnetic proportional valve (6) are provided, and the electromagnetic proportional valve (6) of the electromagnetic proportional valve (6) is provided based on an output signal from these sensors. Since the spool position (opening) is feedback controlled, the hydraulic fluid supply flow rate and pressure can be controlled. It can be of extremely high accuracy.

  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.

  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.

  In addition, since the pressure proportional valve (8) and the current driver circuit therefor which have been required up to now are unnecessary, the cost increase due to the addition of the sensor is offset.

  According to the invention of claim 2, by the flow rate deviation calculation unit (12b), the pressure deviation calculation unit (12a), the PQ selection unit (12c), etc. provided in the controller (12) of the hydraulic circuit device (2, 20), The feedback control of the electromagnetic 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 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) of the hydraulic circuit device (2, 20). In addition, the orifice (17) and pilot relief valve (18) for restricting the flow of hydraulic fluid are provided, so that sufficient safety can be obtained even in the event of a failure of the controller (12) or the electromagnetic 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, the first and second orifices (21, 22) having different throttling degrees are arranged in series, and the second throttling degree is strong. By disposing the check valve (24) in the passage (23) bypassing the orifice (22), the valve element (7a) can be closed while ensuring the stability of the operation of the differential pressure compensation valve (7). When the operation speed is increased and the amount of hydraulic fluid supplied to the actuator is increased, the flow rate responsiveness can be further improved.

According to the invention of claim 5, when the hydraulic actuator is for driving the injection molding machine, the controllability of the operating speed and the operating force is improved by the hydraulic circuit device (2, 20) of the present invention. It is extremely effective to be able to do this, and this can realize a significant improvement in molding quality. Particularly, 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 lowered to zero as in the invention of claim 1, so that the low-pressure mold clamping process. This makes it possible to sufficiently meet the demands and reduce costs.

  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.

(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 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.

  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.

  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).

  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.

  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).

  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).

  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.

  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.

  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). It also has the function of suppressing vibration phenomena.

  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.

  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.

  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.

(PQS valve operation)
Next, the operation of the PQS valve (2) configured as described above will be described.

  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.

  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 responsiveness of the flow rate control.

  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.

  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).

  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.

  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.

  Therefore, according to the PQS valve (2) (hydraulic pressure circuit device) according to the first embodiment, the electromagnetic proportional valve (6) for adjusting the supply flow rate of hydraulic oil to the main engine hydraulic circuit (1) is operated from the main engine side. 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 spool position of the electromagnetic proportional valve (6), as well as adding a discharge position capable of discharging oil And a supply flow rate Q and supply pressure P of hydraulic oil to the main engine side by controlling the spool position based on signals from the sensors (10) and (11). 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.

  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.

  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.

  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 cost increase of the sensors (10, 11) is offset.

(Embodiment 2)
FIG. 5 shows a configuration of a PQS valve (20) (hydraulic circuit device) according to Embodiment 2 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 other configurations are the same as those of the first embodiment. Hereinafter, the same members are denoted by the same reference numerals, and the description thereof is omitted. The PQS valve (20) of the second embodiment applies an appropriate damping to the operation of the valve body (7a) when the differential pressure compensating valve (7) is opened and closed as in the first embodiment. Only 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) serves as a pilot pressure relief valve together with the safety valve (18) and the differential pressure compensation valve (7). At the same time, the valve body (7a) of the differential pressure compensating valve (7) is moderately damped and works to stabilize the operation of the valve body (7a). When the differential pressure compensation valve (7) is closed, the operation of the valve body (7a) becomes slow, and as described above, even if the operation speed of the spool (6a) of the electromagnetic proportional valve (6) is increased, the main engine This will cause the response of the flow rate rise to the side not to speed up much.

  This point will be described in detail. In the PQS valve (2) of the first embodiment, in order to increase the supply flow rate of the hydraulic oil to the main engine side in the flow rate control mode, the flow rate command value Qi is changed and the electromagnetic proportional valve is changed. In addition to increasing the opening degree of (6), it is necessary to increase the flow rate of hydraulic oil from the pump (3) toward 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.

  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.

  In consideration of such a transient phenomenon, in the PQS valve (20) of the second embodiment, as shown in the drawing, the hydraulic oil is supplied to the downstream pilot passage (15) more than the orifice (17) of the first embodiment. A first orifice (21) having a large passage cross-sectional area and a second orifice (22) having a greater degree of restriction than the first orifice (21), ie, having a small passage cross-sectional area, are arranged in series. A check valve (24) for allowing the flow of hydraulic oil toward the differential pressure compensating valve (7) in the bypass passage (23) bypassing the second orifice (22) while preventing the reverse flow Arranged.

  More specifically, the first orifice (21) has a circular cross section having a diameter of about 2 mm, for example, and the second orifice (22) is the same as the orifice (17) of the first embodiment. Similarly, it 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 the second orifice (22) receives the same passage resistance as in the first embodiment. 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.

  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). Accordingly, the flow of the working oil flows faster than that of the first embodiment, and the valve body (7a) of the differential pressure compensation valve (7) closes at a higher speed accordingly. 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.

  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). In the same manner as in the first embodiment, a moderate damping is applied to the operation of the valve body (7a).

  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.

  Therefore, according to the PQS valve (20) according to the second embodiment, the same effect as that of the first embodiment can be obtained, and the two orifices (21) disposed in the downstream pilot passage (15) can be obtained. , (22) and the check valve (24) can further increase the speed of the closing operation of the valve body (7a) while ensuring the stability of the operation of the differential pressure compensating valve (7). As a result, the response can be sufficiently increased even when the supply flow rate of hydraulic oil to the main engine side is increased.

  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.

(Other embodiments)
The present invention is not limited to the configurations of the first and second embodiments, but includes other various actual configurations. That is, in the first and second embodiments, the hydraulic circuit device according to the present invention is a single PQS valve (2, 20), but the hydraulic circuit of the present invention is not necessarily configured as an integrated composite valve. There is no need. 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 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 an analog controller having the same function may be configured using, for example, a comparator or an operational amplifier.

  Furthermore, the electromagnetic proportional valve of the present invention is not limited to those of the above-described embodiments, and may be any throttle valve having an A port, a P port, and a T port and having an electrically adjustable throttle amount. 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.

It is a figure which shows the structure of the PQS valve which concerns on Embodiment 1 of this invention. FIG. 2 is a view corresponding to FIG. 1 when the electromagnetic proportional valve is in a supply position. It is a time chart which shows the change of the supply flow rate and supply pressure of hydraulic fluid when operating the mold clamping cylinder of an injection molding machine. FIG. 6 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. FIG. 3 is a view corresponding to FIG. 1 according to a second embodiment. FIG. 2 is a view corresponding to FIG. 1 illustrating an example of a conventional hydraulic circuit device.

Explanation of symbols

1 Main machine hydraulic circuit 2 PQS valve (hydraulic circuit device)
5 Supply passage 5a Upstream supply passage 5b Downstream supply passage 6 Electromagnetic proportional valve 6a Spool 6b Solenoid 7 Differential pressure compensation valve 7a Valve element 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 unit 12d Current driver 15 Downstream pilot passage 17, 21, 22 Orifice 23 Bypass passage 24 Check valve

Claims (5)

In the hydraulic fluid supply passage (5) to the hydraulic actuator, an electromagnetic proportional valve (6) for adjusting the hydraulic fluid supply flow rate is interposed, and from the upstream side and the downstream side of the electromagnetic proportional valve (6), respectively. A hydraulic circuit device (2) that is provided with a differential pressure compensation valve (7) that bypasses the hydraulic fluid from the upstream supply passage (5a) to the tank (4) so that the differential pressure of the pilot pressure is constant. , 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,
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-controlling the opening of the hydraulic circuit device. The hydraulic circuit device (2,20) according to claim 1,
Controller (12)
Based on the signal from the position sensor (11), the actual supply flow rate of the hydraulic fluid to the actuator is obtained, and the flow rate deviation calculation unit (12b) that calculates the flow rate deviation by subtracting this actual supply flow rate from the flow rate command value;
Based on the signal from the pressure sensor (10), obtain the actual supply fluid pressure of the hydraulic fluid to the actuator, and subtract the actual supply fluid pressure from the pressure command value to calculate the pressure deviation (12a) When,
A PQ selector (12c) that selects a smaller one of the flow deviation and the pressure deviation, and calculates a target spool position of the electromagnetic proportional valve (6) based on the selected deviation;
A current driver (12d) for applying a current to the solenoid (6b) of the spool (6a) of the electromagnetic proportional valve (6) so that the target position calculated by the PQ selection unit (12c) is obtained; A hydraulic circuit device. In the hydraulic circuit device (2,20) according to claim 1 or 2,
The differential pressure compensating valve (7) has a spring member (7b) that urges the valve body (7a) to the closing side, and the valve body (7a) closes to the downstream side of the electromagnetic proportional valve (6). While receiving the pilot pressure from the upstream side of the proportional solenoid valve (6) on the side where the valve element (7a) opens,
The downstream pilot passage (15) for guiding the pilot pressure from the downstream side of the electromagnetic proportional valve (6) to the differential pressure compensation valve (7) is provided with an orifice (17) for restricting the flow of hydraulic fluid, And a pilot relief valve (18) connected to a pilot passage (15) between the orifice (17) and the differential pressure compensating valve (7). The hydraulic circuit device (20) according to claim 3,
In the pilot passage (15) on the downstream side, a first orifice (21) and a second orifice (22) having a higher degree of restriction are arranged in series.
The passage (23) bypassing the second orifice (22) is provided with a check valve (24) that allows the flow of hydraulic fluid toward the differential pressure compensation valve (7) while preventing the reverse flow. A hydraulic circuit device characterized by being provided. In the hydraulic circuit device (20) according to any one of claims 1 to 4,
A hydraulic circuit device, wherein the hydraulic actuator is for driving an injection molding machine.

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