Patent Description:
Conventionally, a fluid pressure control device has been known which adjusts the pressure of a pressure fluid from a fluid supply source to a desired pressure, and supplies the fluid to a fluid actuator. For example, <CIT> discloses a fluid pressure adjusting device that opens and closes a supply valve element and a discharge valve element by controlling, using an air supply solenoid valve and an air discharge solenoid valve, a pilot pressure that acts on a diaphragm, to displace a rod member provided integrally with the diaphragm. In such a fluid pressure adjusting device, when the supply valve element is placed in an open state, a supply port connected to a fluid supply source and a pressure adjusting port connected to fluid pressure equipment communicate with each other, whereas when the discharge valve element is placed in an open state, the pressure fluid on the side of the pressure adjusting port is discharged to the exterior through a discharge port.

Further, a fluid control device that changes a target value of a fluid pressure supplied to a fluid actuator in accordance with an operating state of the fluid actuator is also known. For example, in the specification of <CIT>, a fluid control device is disclosed in which, when a decrease of a flow rate in a certain amount or more is detected, a transition is made from a normal operating mode to a standby mode, and at the time of the standby mode, a fluid having a pressure which is set to a lower pressure than at the time of the normal operating mode is supplied to the fluid actuator. Such a fluid control device has a configuration in which a shutoff valve is connected in series to and downstream of a proportional pressure regulating valve.

<CIT> discloses a proportional pressure control valve assembly including a valve member functioning jointly with a valve seat, a movable division wall configured to abut against the valve member, and a pilot chamber separated from an operating chamber by the movable division wall. The assembly controls the pressure at the pilot chamber using an air supply valve and a venting valve in order to adjust the pressure at the outlet.

The multifunctional fluid control apparatus disclosed in <CIT> includes a poppet valve for opening/closing a communication path between an inlet passage and an outlet passage, a diaphragm to which a push pin configured to be pushed against the poppet valve is connected, a pilot chamber separated by the diaphragm, a pressurizing pilot valve for increasing the pressure in the pilot chamber, a depressurizing pilot valve for decreasing the pressure in the pilot chamber, an inlet pressure sensor and an outlet pressure sensor. The apparatus controls the outlet pressure at a predetermined level.

As seen in the fluid pressure adjusting device of <CIT>, in order to control the pressure on the port side (secondary port side) that is connected to the fluid pressure equipment from a high pressure to a low pressure, it is common technical knowledge to use a discharge valve element. In this case, it is inevitable that a portion of the pressure fluid from the fluid supply source will end up being discarded without being used in the fluid pressure equipment. The proportional pressure regulating valve disclosed in the specification of <CIT> is also equipped with a port for discharging fluid on the secondary side, and therefore a similar phenomenon occurs.

Further, in the fluid control device disclosed in the specification of <CIT>, a configuration is required in which a shutoff valve is connected in series to and downstream of a proportional pressure regulating valve, and since the shutoff valve is provided in a flow path having a large flow rate, there is a concern that the size and scale of the device may become large. Furthermore, in the fluid control device disclosed in the specification of <CIT>, it is necessary to provide a flow rate sensor in addition to a pressure sensor.

The present invention has the object of solving the aforementioned problems.

According to the invention there is provided a fluid pressure control device according to claim <NUM>. Preferred embodiments of the invention are provided by the depending claims.

A fluid pressure control device according to the present invention is disposed between a fluid supply source and a fluid actuator, and is configured to transition from a normal mode, in which a fluid pressure supplied to the fluid actuator is set to an operating pressure, to a standby mode, in which the fluid pressure is set to a standby pressure that is lower than the operating pressure. In addition, the fluid pressure control device comprises an inlet port connected to the fluid supply source, an outlet port connected to the fluid actuator, a supply valve configured to adjust an area of a flow path connecting the inlet port and the outlet port, and a diaphragm configured to displace a valve element of the supply valve.

A pilot chamber is formed on one side of the diaphragm, and a feedback chamber communicating with the outlet port is formed on another side of the diaphragm. A pilot pressure supply solenoid valve is disposed in a flow path connecting the inlet port and the pilot chamber, and a pilot pressure discharge solenoid valve is disposed in a flow path through which a pressure fluid in the pilot chamber is discharged to an exterior. Furthermore, the fluid pressure control device further comprises a control unit configured to control the pilot pressure supply solenoid valve and the pilot pressure discharge solenoid valve. The fluid pressure control device does not comprise a flow path through which the pressure fluid that has passed through the supply valve is discharged to the exterior.

According to the above-described fluid pressure control device, all of the pressure fluid that has passed through the supply valve is supplied to the fluid actuator, and loss of the pressure fluid can be suppressed to a minimum. Further, while performing a control to change a target value (set pressure) of the fluid pressure supplied to the fluid actuator from a high operating pressure to a low standby pressure, the fluid pressure control device does not include a flow path through which the pressure fluid that has passed through the supply valve is discharged to the exterior. Therefore, there is no need to separately provide a shutoff valve, and the device as a whole can be made small in scale.

According to the present invention, when transitioning from the normal mode to the standby mode, the fluid pressure control device performs a control to change the target value of the fluid pressure supplied to the fluid actuator from the high operating pressure to the low standby pressure, but the fluid pressure control device does not include a flow path through which the pressure fluid that has passed through the supply valve is discharged to the exterior. Therefore, in addition to enabling a loss of the pressure fluid to be suppressed to a minimum, there is no need to separately provide a shutoff valve, and the device as a whole can be made small in scale.

The fluid used in the present invention is a pressure fluid such as compressed air or the like. In the following description, when terms in relation to up and down directions are used, such terms refer to the directions shown in the drawings for the sake of convenience, and the actual arrangement of the constituent members and the like is not necessarily limited to this feature.

A fluid pressure control device <NUM> according to an embodiment of the present invention is disposed between a fluid supply source and a fluid actuator (neither of which is shown). When a flow rate flowing toward the fluid actuator falls continuously below a predetermined value for a predetermined time period, the fluid pressure control device <NUM> sets the fluid pressure supplied to the fluid actuator to a standby pressure which is lower than an operating pressure. First, a description will be given concerning the configurations and functions possessed by the fluid pressure control device <NUM> in order to perform such a control.

As shown in <FIG>, the fluid pressure control device <NUM> comprises a valve body <NUM> in which a supply valve <NUM> is incorporated, and a control housing <NUM> in which a pilot pressure supply solenoid valve <NUM> and a pilot pressure discharge solenoid valve <NUM> are incorporated. The control housing <NUM> is connected to an upper part of the valve body <NUM>.

The valve body <NUM> includes an inlet port <NUM> connected to a fluid supply source (air compressor), and an outlet port <NUM> connected to a fluid actuator such as an air cylinder or the like. The inlet port <NUM> and the outlet port <NUM> are disposed coaxially. A cylindrical wall portion <NUM> having a valve seat 22a at an end part thereof intersects with a connecting passage <NUM> that connects the inlet port <NUM> and the outlet port <NUM>. At a position facing toward the wall portion <NUM>, a circular recess <NUM> that extends downward from the connecting passage <NUM> is disposed.

A valve element <NUM> constitutes the supply valve <NUM> together with the valve seat 22a. The valve element <NUM> is made up from a disk-shaped plate portion 28a capable of abutting against the valve seat 22a, and a cylindrical guide portion 28b that extends downward from a lower surface of the plate portion 28a. A seal member 28c that abuts against the valve seat 22a is mounted on an outer circumference of an upper part of the plate portion 28a. The seal member 28c is constituted by an elastic material such as rubber or the like.

The guide portion 28b of the valve element <NUM> is supported so as to be capable of sliding in up and down directions in the recess <NUM> of the valve body <NUM>. A seal ring 30a that is in sliding contact with a wall surface of the recess <NUM> is mounted on an outer circumference of the guide portion 28b. In a space on an inner side of the guide portion 28b, a first spring <NUM> for biasing the valve element <NUM> toward the valve seat 22a is disposed between the lower surface of the plate portion 28a and a bottom surface of the recess <NUM>. The plate portion 28a includes a plurality of holes 28d that allows communication between the space on the inner side of the guide portion 28b and a space above the plate portion 28a.

In a central portion of the valve body <NUM>, an elongated rod <NUM> that extends in the up and down directions is supported so as to be capable of moving in an axial direction thereof. A seal ring 30b that is in sliding contact with an outer circumference of the rod <NUM> is disposed on the valve body <NUM>. An upper end of the rod <NUM> integrally includes a disk-shaped flange portion 40a that extends in a horizontal direction. A lower end of the rod <NUM> projects into the connecting passage <NUM>, and is capable of abutting against an upper surface of the plate portion 28a of the valve element <NUM>.

When the seal member 28c of the valve element <NUM> is placed in a state of being pressed against the valve seat 22a due to the biasing force of the first spring <NUM>, communication between the inlet port <NUM> and the outlet port <NUM> is shut off. On the other hand, as will be discussed later, when a force, which drives the valve element <NUM> downward against the biasing force of the first spring <NUM>, acts on the rod <NUM>, the seal member 28c of the valve element <NUM> separates away from the valve seat 22a, and the inlet port <NUM> and the outlet port <NUM> communicate with each other. In this case, the area of the flow path connecting the inlet port <NUM> and the outlet port <NUM> (a degree of opening V of the supply valve <NUM>) is adjusted in accordance with the driving force that acts on the rod <NUM>.

The upper part of the valve body <NUM> includes a diaphragm chamber <NUM>. In the diaphragm chamber <NUM>, there are accommodated an upper portion of the rod <NUM> including the flange portion 40a, and a diaphragm <NUM> that is made of a flexible material. An outer circumferential portion of the diaphragm <NUM> is attached to a groove portion that is formed in the valve body <NUM>. An inner circumferential portion of the diaphragm <NUM> is sandwiched between the flange portion 40a of the rod <NUM> and a disc member <NUM> that is inserted over and fixed to the rod <NUM>. Consequently, the inner circumferential portion of the diaphragm <NUM> is fixed to the rod <NUM>.

The diaphragm chamber <NUM> is partitioned into a pilot chamber <NUM> and a feedback chamber <NUM>. The pilot chamber <NUM> is formed upwardly of the diaphragm <NUM> and the flange portion 40a. The feedback chamber <NUM> is formed downwardly of the diaphragm <NUM> and the disc member <NUM>. The feedback chamber <NUM> communicates with the outlet port <NUM> via a first passage 52a that is formed in the valve body <NUM>. A second spring <NUM> is disposed in the feedback chamber <NUM>. One end of the second spring <NUM> abuts against the disc member <NUM>. Another end of the second spring <NUM> abuts against the valve body <NUM>.

Due to the fluid pressure in the pilot chamber <NUM> acting on upper surfaces of the diaphragm <NUM> and the flange portion 40a, a downward pushing force acts on the rod <NUM>. Further, due to the fluid pressure in the feedback chamber <NUM> acting on lower surfaces of the diaphragm <NUM> and the disc member <NUM>, and a biasing force of the second spring <NUM>, an upward pushing force acts on the rod <NUM>. When the former force exceeds the latter force, the rod <NUM> drives the valve element <NUM> downward against the biasing force of the first spring <NUM>, and displaces the valve element <NUM> downward to a position balanced with the reaction force of the first spring <NUM>. If a pressure P1 in the pilot chamber <NUM> is increased, the degree of opening V of the supply valve <NUM> becomes larger.

The valve body <NUM> includes a second passage 52b that branches off from the first passage 52a, and reaches an upper surface of the valve body <NUM>. Further, the valve body <NUM> additionally includes a third passage 52c and a fourth passage 52d. A lower end of the third passage 52c is connected to the inlet port <NUM>. An upper end of the third passage 52c reaches the upper surface of the valve body <NUM>. A lower end of the fourth passage 52d is connected to the pilot chamber <NUM>. An upper end of the fourth passage 52d reaches the upper surface of the valve body <NUM>. The control housing <NUM> includes a fifth passage 52e that connects the upper end of the third passage 52c and the upper end of the fourth passage 52d to each other. The pilot pressure supply solenoid valve <NUM> is disposed in the fifth passage 52e. The pilot pressure supply solenoid valve <NUM> is a normally closed type two-way valve that is capable of being switched between a position to allow communication between the third passage 52c and the fourth passage 52d, and a position to shut off the communication between the third passage 52c and the fourth passage 52d.

Accordingly, the pilot pressure supply solenoid valve <NUM> can be switched between a communicating position to allow the pressure fluid in the inlet port <NUM> to be introduced into the pilot chamber <NUM>, and a shutoff position to shut off the pilot chamber <NUM> from the inlet port <NUM>. The pilot pressure supply solenoid valve <NUM> is disposed in a flow path connecting the inlet port <NUM> and the pilot chamber <NUM>. Since the pilot pressure supply solenoid valve <NUM> is not interposed in a flow path having a large flow rate, a small scale solenoid valve is sufficient.

The control housing <NUM> comprises a discharge port <NUM> that is open to the atmosphere. In order to connect the upper end of the fourth passage 52d and the discharge port <NUM>, the control housing <NUM> includes a sixth passage 52f that branches off from a midway location of the fifth passage 52e, and reaches the discharge port <NUM>. The pilot pressure discharge solenoid valve <NUM> is disposed in the sixth passage 52f. The pilot pressure discharge solenoid valve <NUM> is a normally closed type two-way valve that is capable of being switched between a position to allow communication between the fourth passage 52d and the discharge port <NUM>, and a position to shut off the communication between the fourth passage 52d and the discharge port <NUM>.

Accordingly, the pilot pressure discharge solenoid valve <NUM> can be switched between a communicating position to allow the pressure fluid in the pilot chamber <NUM> to be discharged, and a shutoff position to shut off the pilot chamber <NUM> from the discharge port <NUM>. The pilot pressure discharge solenoid valve <NUM> is disposed in a flow path through which the pressure fluid in the pilot chamber <NUM> is discharged to the exterior. Since the pilot pressure discharge solenoid valve <NUM> is not interposed in a flow path having a large flow rate, a small scale solenoid valve is sufficient. Further, since the volume of the pilot chamber <NUM> is limited and the amount of the pressure fluid in the pilot chamber <NUM> discharged to the exterior is extremely small, loss of the pressure fluid can be kept to a minimum.

A control unit <NUM> made up from an integrated circuit (IC) is disposed in the control housing <NUM>. The pilot pressure supply solenoid valve <NUM> and the pilot pressure discharge solenoid valve <NUM> are controlled on the basis of signals from the control unit <NUM>. When the pilot pressure supply solenoid valve <NUM> is switched to the communicating position and the pilot pressure discharge solenoid valve <NUM> is switched to the shutoff position, the pressure fluid in the inlet port <NUM> is introduced into the pilot chamber <NUM>. Consequently, the pressure P1 in the pilot chamber <NUM> increases, and the degree of opening V of the supply valve <NUM> becomes larger. When the pilot pressure supply solenoid valve <NUM> is switched to the shutoff position and the pilot pressure discharge solenoid valve <NUM> is switched to the communicating position, the pressure fluid in the pilot chamber <NUM> is discharged to the exterior. Consequently, the pressure P1 in the pilot chamber <NUM> decreases, and the degree of opening V of the supply valve <NUM> becomes smaller.

In the case that the pilot pressure supply solenoid valve <NUM> and the pilot pressure discharge solenoid valve <NUM> are PWM-controlled, the pressure P1 in the pilot chamber <NUM> can be finely controlled by controlling the timing at which current is supplied to the solenoid valves <NUM> and <NUM>, and therefore, the degree of opening V of the supply valve <NUM> can be adjusted in a stepless manner.

The control housing <NUM> includes a seventh passage <NUM> that branches off from a midway location of the fifth passage 52e. A first pressure sensor <NUM> that detects the pressure P1 in the pilot chamber <NUM> is disposed so as to face the seventh passage <NUM>. Further, the control housing <NUM> includes an eighth passage <NUM> connected to the second passage 52b of the valve body <NUM>. A second pressure sensor <NUM> that detects a pressure P2 in the outlet port <NUM> is disposed so as to face the eighth passage <NUM>. Signals detected by the first pressure sensor <NUM> and the second pressure sensor <NUM> are input to the control unit <NUM>.

An operating pressure Ps1, which is a set pressure in a normal mode (at a time of normal operation), a standby pressure Ps2, which is a set pressure in a standby mode, a flow rate threshold value L, and a monitoring time period T are stored in the control unit <NUM>. These values can be arbitrarily set and modified by a user, and are fed into the control unit <NUM> as input signals G1. The operating pressure Ps1 is a target value (set pressure) of the fluid pressure supplied to the fluid actuator when the fluid actuator is operating. The standby pressure Ps2 is a target value (set pressure) of the fluid pressure supplied to the fluid actuator when the fluid actuator is in a paused state. The standby pressure Ps2 is lower than the operating pressure Ps1.

A standby release signal G2 for returning from the standby mode to the normal mode is input as a pulse signal to the control unit <NUM> from the exterior. In the case that a change from the normal mode to the standby mode is made capable of being manually performed, a mode switching signal G3 is input to the control unit <NUM> from the exterior. Further, a pressure display unit <NUM>, which is capable of displaying the set operating pressure Ps1 and the set standby pressure Ps2 together with displaying the pressure P2 in the outlet port <NUM>, is connected to the control unit <NUM>. Moreover, the control unit <NUM> is capable of outputting the pressure P2 in the outlet port <NUM> and a later-described estimated flow rate Qe as output signals G4 to the exterior.

The fluid pressure control device <NUM> according to the present embodiment is provided with the aforementioned configurations and functions. Next, a description will be given with reference to <FIG>, concerning a control for a case in which transitioning from the normal mode to the standby mode is automatically performed. A state, in which the fluid actuator is in the operating state and the fluid pressure control device <NUM> is operating in the normal mode, is regarded as an initial state. Referring to <FIG>, for example, the state at time t2 corresponds to such an initial state.

When the fluid pressure control device <NUM> is operating in the normal mode, the control unit <NUM> controls the operations of the pilot pressure supply solenoid valve <NUM> and the pilot pressure discharge solenoid valve <NUM>, and thereby adjusts the degree of opening V of the supply valve <NUM> in a manner so that the pressure P2 in the outlet port <NUM>, which is detected by the second pressure sensor <NUM>, coincides with a target value, which is the operating pressure Ps1. Consequently, the pressure P2 in the outlet port <NUM> is maintained at the set operating pressure Ps1. When the fluid actuator is in the operating state, the pressure P1 in the pilot chamber <NUM> significantly exceeds the pressure P2 in the outlet port <NUM> that is maintained at the operating pressure Ps1, and the degree of opening V of the supply valve <NUM> is also sufficiently large (from time t1 to time t2).

Even when the fluid pressure control device <NUM> is operating in the normal mode, in the case that the pressure P2 in the outlet port <NUM> is greater than the operating pressure Ps1, and further, the pressure P1 in the pilot chamber <NUM> is less than or equal to a predetermined value, the pilot pressure discharge solenoid valve <NUM> is set to the shutoff position. The reason therefor is as follows.

Depending on the operating condition of the fluid actuator, even if the pilot pressure discharge solenoid valve <NUM> is maintained at the communicating position, cases may occur in which the pressure P2 in the outlet port <NUM> does not become less than or equal to the operating pressure Ps1. Further, even if the pilot pressure discharge solenoid valve <NUM> is maintained at the communicating position, cases may occur in which the pressure P1 in the pilot chamber <NUM> is not lowered to atmospheric pressure. Accordingly, a value which is slightly greater than atmospheric pressure (for example, <NUM> kPa in gauge pressure) is set as a predetermined value Pk, and in the case that the inequalities P2 > Ps1 and P1 ≤ Pk are satisfied, the pilot pressure discharge solenoid valve <NUM> is set to the shutoff position. This is because supplying electrical power to the pilot pressure discharge solenoid valve <NUM> and maintaining it at the communicating position leads to the electrical power being needlessly consumed. It should be noted that such a situation is not depicted in the timing chart of <FIG>.

When the fluid pressure control device <NUM> is operating in the normal mode, the control unit <NUM> estimates the flow rate of the fluid flowing toward the fluid actuator (the flow rate Q of the fluid passing through the supply valve <NUM>) based on the signals detected by the first pressure sensor <NUM> and the second pressure sensor <NUM>. The method of estimating the flow rate Q is as follows.

The flow rate Q becomes greater as the differential pressure between the pressure P1 in the pilot chamber <NUM> and the pressure P2 in the outlet port <NUM> becomes greater. Further, the flow rate Q differs depending on the set pressure, even if the differential pressure between the pressure P1 in the pilot chamber <NUM> and the pressure P2 in the outlet port <NUM> is the same. <FIG> is a graph showing a relationship between the differential pressure (P1 - P2) between the pressure P1 in the pilot chamber <NUM> and the pressure P2 in the outlet port <NUM>, and the flow rate Q, with the set pressure serving as a parameter. More specifically, with the set pressure being set to the two values PsA and PsB (PA < PB), the pressure P1 in the pilot chamber <NUM>, the pressure P2 in the outlet port <NUM>, and the flow rate Q are actually measured using the pressure sensors and a flow rate sensor, and are shown based on the obtained data. As can be understood from <FIG>, the relationship between the differential pressure (P1 - P2) and the flow rate Q is approximated by a straight line, and the slope thereof differs depending on the set pressure.

Thus, for the flow rate Q of the fluid passing through the supply valve <NUM>, the estimated flow rate Qe is obtained by the following expression, where K is a constant corresponding to the set pressure (a constant corresponding to the set value of the operating pressure Ps1).

The control unit <NUM> has stored therein a table relating to the constant K as determined for each of set pressures, and calculates the estimated flow rate Qe based on signals input from the first pressure sensor <NUM> and the second pressure sensor <NUM>.

In this manner, by including the second pressure sensor <NUM> in addition to the first pressure sensor <NUM>, the fluid pressure control device <NUM> can estimate the flow rate of the fluid flowing toward the fluid actuator. Therefore, the fluid pressure control device <NUM> does not require a flow rate sensor. In the case of wanting to improve the accuracy with which the flow rate is estimated, a pressure sensor that detects the pressure in the inlet port <NUM>, and a temperature sensor that detects the temperature of the fluid passing through the supply valve <NUM> may be added, and in addition to the set pressure, a table relating to a constant (K') that is set by also taking into consideration the pressure in the inlet port <NUM> and the temperature of the fluid may be used.

When the control unit <NUM> determines that the estimated flow rate Qe has continuously fallen below the predetermined flow rate threshold value L for the monitoring time period T (predetermined time period) in the normal mode, the control unit <NUM> considers that the fluid actuator has entered into the paused state, and determines to transition to the standby mode (time t3). In the standby mode, the control unit <NUM> controls the operations of the pilot pressure supply solenoid valve <NUM> and the pilot pressure discharge solenoid valve <NUM>, and thereby adjusts the degree of opening V of the supply valve <NUM> in a manner so that the pressure P2 in the outlet port <NUM>, which is detected by the second pressure sensor <NUM>, coincides with a target value, which is the standby pressure Ps2. Consequently, the pressure P2 in the outlet port <NUM> is set to the standby pressure Ps2, which is lower than the operating pressure Ps1. Transitioning from the normal mode to the standby mode is automatically performed in this manner.

Immediately after transitioning from the normal mode to the standby mode and at least while the pressure P2 in the outlet port <NUM> falls from the operating pressure Ps1 to the standby pressure Ps2 (from time t3 to immediately before time t4), the supply valve <NUM> is controlled so as to be maintained in the closed position, and communication between the inlet port <NUM> and the outlet port <NUM> is shut off. This is because the pressure P2 in the outlet port <NUM>, which is detected by the second pressure sensor <NUM>, continues to remain higher than the standby pressure Ps2, which is the target value. Accordingly, the pressure fluid is not newly supplied from the fluid supply source toward the fluid actuator, and consumption of the pressure fluid becomes zero. At this time, the fluid that is accumulated in the fluid actuator gradually escapes.

The standby mode is a mode for preparing return of the fluid actuator in the paused state to the operating state. The fluid actuator does not need to be supplied with the pressure fluid in the paused state, however, by supplying the fluid at the standby pressure Ps2 beforehand, it is possible for the fluid actuator to be quickly and smoothly returned to the operating state. Moreover, while the fluid, which is at the standby pressure Ps2, is being supplied to the fluid actuator in the paused state, a constant leakage of the fluid occurs in the fluid actuator. The amount of such leakage is smaller than the amount of leakage that occurs in the case that the fluid, which is at the operating pressure Ps1, is supplied to the fluid actuator in the paused state.

Even when the fluid pressure control device <NUM> is operating in the standby mode, in the case that the pressure P2 in the outlet port <NUM> is greater than the standby pressure Ps2, and further, the pressure P1 in the pilot chamber <NUM> is less than or equal to the predetermined value, the pilot pressure discharge solenoid valve <NUM> is set to the shutoff position. This is because, similar to when operating in the normal mode, even if the pilot pressure discharge solenoid valve <NUM> is maintained at the communicating position, cases may occur in which the pressure P2 in the outlet port <NUM> does not become less than or equal to the standby pressure Ps2. Further, since the pressure P1 in the pilot chamber <NUM> is not lowered to atmospheric pressure, unnecessary operation of the pilot pressure discharge solenoid valve <NUM> is suppressed. It should be noted that such a situation is not depicted in the timing chart of <FIG>.

Returning from the standby mode to the normal mode is performed in accordance with the standby release signal G2 (time t5). The standby release signal G2 is a pulse signal that is input to the control unit <NUM> from the exterior, in order to return the fluid actuator, which is in the paused state, to the operating state. For example, the signal may be a signal which is input by an operation performed by the user on a touch panel, or may be a signal which is automatically input at a time that is set by the user for resuming operation of the fluid actuator. When returning from the standby mode to the normal mode, in order to realize a soft start, the set pressure may be changed in a stepwise manner from the standby pressure Ps2 to the operating pressure Ps1. Further, returning to the normal mode need not necessarily be performed in accordance with the standby release signal G2, but may be performed at a time that the estimated flow rate Qe has become greater than the flow rate threshold value L.

Incidentally, in the fluid pressure control device <NUM>, when transitioning from the normal mode to the standby mode, the set pressure of the outlet port <NUM> is changed from the high operating pressure Ps1 to the low standby pressure Ps2. However, the fluid pressure control device <NUM> is not provided with a valve that controls the change from the high pressure to the low pressure (a valve for discharging fluid from the outlet port <NUM>). This is because, when the fluid actuator enters into the paused state, there is no need to rapidly cause the pressure P2 in the outlet port <NUM> to decrease to the standby pressure Ps2, and it is satisfactory to wait for the pressure P2 in the outlet port <NUM> to decrease naturally to the standby pressure Ps2 by allowing the fluid accumulated in the fluid actuator to escape to a certain extent. In the foregoing manner, since the fluid pressure control device <NUM> is not provided with a valve for discharging the fluid from the outlet port <NUM>, loss of the pressure fluid can be suppressed.

Next, a description will be given with reference to <FIG>, concerning a control for a case in which transitioning from the normal mode to the standby mode is manually performed.

Similar to the case in which transitioning from the normal mode to the standby mode is automatically performed, when the fluid pressure control device <NUM> is operating in the normal mode, the control unit <NUM> calculates the estimated flow rate Qe. In addition, at time t3, when the control unit <NUM> determines that the estimated flow rate Qe has continuously fallen below the flow rate threshold value L for the monitoring time period T, the control unit <NUM> waits for a change in the mode switching signal G3 which is manually input from the exterior. At time t3', when the mode switching signal G3 changes from OFF to ON, the control unit <NUM> determines to transition from the normal mode to the standby mode. Returning from the standby mode to the normal mode is performed in accordance with changing of the mode switching signal G3 from ON to OFF (time t5').

As noted previously, transitioning from the normal mode to the standby mode is performed on the condition that the mode switching signal G3 undergoes a change after the estimated flow rate Qe has continuously fallen below the flow rate threshold value L for the monitoring time period T. However, transitioning from the normal mode to the standby mode may be performed only on the condition that the mode switching signal G3 undergoes a change.

Flowcharts for realizing the aforementioned controls are shown in <FIG>. <FIG> is a flowchart for a case in which transitioning from the normal mode to the standby mode is automatically performed, and returning to the normal mode is performed in accordance with the standby release signal G2. <FIG> is a flowchart for a case in which transitioning from the normal mode to the standby mode is automatically performed, and returning to the normal mode is automatically performed based on a flow rate. <FIG> is a flowchart for a case in which transitioning from the normal mode to the standby mode is performed manually.

In step S1 shown in <FIG>, the control unit <NUM> reads the latest signals input from the first pressure sensor <NUM> and the second pressure sensor <NUM>, and thereby acquires the pressure P1 in the pilot chamber <NUM> and the pressure P2 in the outlet port <NUM>. Then, the control unit <NUM> compares the pressure P2 in the outlet port <NUM> with the operating pressure Ps1. When the pressure P2 in the outlet port <NUM> is less than the operating pressure Ps1, the control unit <NUM> controls the pilot pressure supply solenoid valve <NUM> and the pilot pressure discharge solenoid valve <NUM>, and thereby increases the degree of opening V of the supply valve <NUM>. When the pressure P2 in the outlet port <NUM> is greater than the operating pressure Ps1, the control unit <NUM> controls the pilot pressure supply solenoid valve <NUM> and the pilot pressure discharge solenoid valve <NUM>, and thereby decreases the degree of opening V of the supply valve <NUM>.

Next, upon proceeding to step S2, the control unit <NUM> determines whether or not the pressure P2 in the outlet port <NUM>, which has been acquired in step S1, is greater than the operating pressure Ps1, and further, whether or not the pressure P1 in the pilot chamber <NUM>, which has been acquired in step S1, is less than or equal to the predetermined value Pk. In the case that such a determination result is YES, the control unit <NUM> outputs, to the pilot pressure discharge solenoid valve <NUM>, a signal for switching to the shutoff position, and then the process proceeds to step S3. In the case that the determination result is NO, the process immediately proceeds to step S3.

In step S3, the control unit <NUM> obtains the estimated flow rate Qe based on the pressure P1 in the pilot chamber <NUM> and the pressure P2 in the outlet port <NUM>, which have been acquired in step S1, while referring to the table relating to the constant K, and then the process proceeds to step S4. In step S4, the control unit <NUM> compares the estimated flow rate Qe obtained in step S3 with the flow rate threshold value L, and in the case that the estimated flow rate Qe is less than or equal to the flow rate threshold value L, the process proceeds to step S5. In the case that the estimated flow rate Qe is greater than the flow rate threshold value L, the process returns to step S1.

In step S5, the control unit <NUM> determines whether or not a time period of greater than or equal to the monitoring time period T has elapsed since the estimated flow rate Qe has become less than or equal to the flow rate threshold value L. More specifically, the control unit <NUM> determines whether or not the state in which the estimated flow rate Qe is less than or equal to the flow rate threshold value L has continued for a time period of greater than or equal to the monitoring time period T. If the state in which the estimated flow rate Qe is less than or equal to the flow rate threshold value L has continued for a time period of greater than or equal to the monitoring time period T, the process proceeds to step S6. If the state in which the estimated flow rate Qe is less than or equal to the flow rate threshold value L has not continued for a time period of greater than or equal to the monitoring time period T, the process returns to step S1. In step S6, in order to transition from the normal mode to the standby mode, the control unit <NUM> changes the set pressure from the operating pressure Ps1 to the standby pressure Ps2, and then the process proceeds to step S7.

In step S7, the control unit <NUM> reads the latest signals input from the first pressure sensor <NUM> and the second pressure sensor <NUM>, and thereby acquires the pressure P1 in the pilot chamber <NUM> and the pressure P2 in the outlet port <NUM>. Then, the control unit <NUM> compares the pressure P2 in the outlet port <NUM> with the standby pressure Ps2. When the pressure P2 in the outlet port <NUM> is less than the standby pressure Ps2, the control unit <NUM> controls the pilot pressure supply solenoid valve <NUM> and the pilot pressure discharge solenoid valve <NUM>, and thereby increases the degree of opening V of the supply valve <NUM>. When the pressure P2 in the outlet port <NUM> is greater than the standby pressure Ps2, the control unit <NUM> controls the pilot pressure supply solenoid valve <NUM> and the pilot pressure discharge solenoid valve <NUM>, and thereby decreases the degree of opening V of the supply valve <NUM>.

Next, upon proceeding to step S8, the control unit <NUM> determines whether or not the pressure P2 in the outlet port <NUM>, which has been acquired in step S7, is greater than the standby pressure Ps2, and further, whether or not the pressure P1 in the pilot chamber <NUM>, which has been acquired in step S7, is less than or equal to the predetermined value Pk. In the case that such a determination result is YES, the control unit <NUM> outputs, to the pilot pressure discharge solenoid valve <NUM>, a signal for switching to the shutoff position, and then the process proceeds to step S9. In the case that the determination result is NO, the process immediately proceeds to step S9.

In step S9, the control unit <NUM> determines whether or not the standby release signal G2 for returning from the standby mode to the normal mode has been input from the exterior. In the case that the standby release signal G2 has been input from the exterior, the process returns to step S1. In the case that the standby release signal G2 has not been input from the exterior, the process returns to step S7.

As shown in <FIG>, the flowchart for a case in which returning to the normal mode is performed based on the flow rate is a flowchart in which step S91 and step S92 are provided instead of step S9 in the flowchart of <FIG>. Hereinafter, a description will be given focusing on the changed portions.

In step S91, the control unit <NUM> obtains the estimated flow rate Qe based on the pressure P1 in the pilot chamber <NUM> and the pressure P2 in the outlet port <NUM>, which have been acquired in step S7, while referring to the table relating to the constant K, and then the process proceeds to step S92. In step S92, the control unit <NUM> compares the estimated flow rate Qe obtained in step S91 with the flow rate threshold value L. In the case that the estimated flow rate Qe is greater than the flow rate threshold value L, the process returns to step S1. In the case that the estimated flow rate Qe is less than or equal to the flow rate threshold value L, the process returns to step S7.

As shown in <FIG>, the flowchart for a case in which transitioning from the normal mode to the standby mode is performed manually is a flowchart in which, in the flowchart of <FIG>, step SA is added between steps S5 and S6, and step S9 is changed to step S9'. Hereinafter, a description will be given focusing on the added and changed portions.

In step S5, the control unit <NUM> determines whether or not the state in which the estimated flow rate Qe is less than or equal to the flow rate threshold value L has continued for a time period of greater than or equal to the monitoring time period T. If the state in which the estimated flow rate Qe is less than or equal to the flow rate threshold value L has continued for a time period of greater than or equal to the monitoring time period T, the process proceeds to step SA. If the state in which the estimated flow rate Qe is less than or equal to the flow rate threshold value L has not continued for a time period of greater than or equal to the monitoring time period T, the process returns to step S1.

In step SA, the control unit <NUM> determines whether or not the mode switching signal G3 has been changed from OFF to ON. In the case that the mode switching signal G3 has been changed from OFF to ON, the process proceeds to step S6. In the case that the mode switching signal G3 remains OFF, the process returns to step S1. In step S6, in order to transition from the normal mode to the standby mode, the control unit <NUM> changes the set pressure from the operating pressure Ps1 to the standby pressure Ps2, and then the process proceeds to step S7.

In step S9', the control unit <NUM> determines whether or not the mode switching signal G3 has been changed from ON to OFF. In the case that the mode switching signal G3 has been changed from ON to OFF, the process returns to step S1. In the case that the mode switching signal G3 remains ON, the process returns to step S7.

Claim 1:
A fluid pressure control device (<NUM>) disposed between a fluid supply source and a fluid actuator comprising:
an inlet port (<NUM>) connected to the fluid supply source;
an outlet port (<NUM>) connected to the fluid actuator;
a supply valve (<NUM>) configured to adjust an area of a flow path connecting the inlet port and the outlet port; and
a diaphragm (<NUM>) configured to displace a valve element (<NUM>) of the supply valve, wherein
a pilot chamber (<NUM>) is formed on one side of the diaphragm,
a feedback chamber (<NUM>) communicating with the outlet port is formed on another side of the diaphragm,
a pilot pressure supply solenoid valve (<NUM>) is disposed in a flow path connecting the inlet port and the pilot chamber, and
a pilot pressure discharge solenoid valve (<NUM>) is disposed in a flow path through which a pressure fluid in the pilot chamber is discharged to an exterior, and wherein
the fluid pressure control device further comprises a control unit (<NUM>) configured to control the pilot pressure supply solenoid valve and the pilot pressure discharge solenoid valve,
characterized in that
the fluid pressure control device is configured to transition from a normal mode, in which a fluid pressure supplied to the fluid actuator is set to an operating pressure, to a standby mode, in which the fluid pressure is set to a standby pressure that is lower than the operating pressure, wherein
a transition from the normal mode to the standby mode is performed automatically on the condition that a flow rate flowing toward the fluid actuator continuously falls below a predetermined value for a predetermined time period or
the transition is performed manually on the condition that a mode switching signal input from the exterior is changed after a flow rate flowing toward the fluid actuator continuously falls below a predetermined value for a predetermined time period
and that
the fluid pressure control device does not comprise a flow path through which the pressure fluid that has passed through the supply valve is discharged to the exterior.