Patent Application
20180348797
The present invention relates generally to a fluid control valve device.
Conventionally known fluid control valve devices include a spool valve that electrically controls open and closed positions of a pressure increasing valve and a pressure reducing valve to adjust a pilot pressure, thereby adjusting pressure and a flow rate of a fluid to be supplied to an object to control (for example, Patent Document 1).
Patent Document 1: International Publication No. WO2015/080277
In such a fluid control valve device, however, a problem in movement of a spool in the spool valve may lead to, for example, undesirable inconveniences including lowering responsiveness to changes in the pressure and the flow rate of the supply of the fluid to the object to control. It is therefore an object of the present invention to attain a fluid control valve device that includes a spool valve that allows the spool to move more smoothly, for example.
A fluid control valve device of the present invention includes, for example, a spool valve including: a housing; and a spool housed in the housing so as to be movable in a first direction and a second direction opposite to the first direction, the housing and the spool defining a control pressure chamber and a supply pressure chamber, the control pressure chamber that applies a control pressure that gives the spool a force to move in the first direction and the supply pressure chamber that applies a supply pressure that gives the spool a force to move in the second direction, the housing provided with an introduction port, a discharge port, and a supply port, the introduction port that is opened to introduce fluid into the supply pressure chamber when the spool moves in the first direction and is closed when the spool moves in the second direction, the discharge port that is opened to discharge the fluid from the supply pressure chamber when the spool moves in the second direction and is closed when the spool moves in the first direction, and the supply port that supplies the fluid from the supply pressure chamber to an object to control; a control valve that changes an open or closed state to control pressure in the control pressure chamber; a control unit that controls the open or closed state of the control valve in accordance with a command value; and storage that stores therein past data on at least one of a control value by which the control unit controls the control valve, a value calculated by the control unit, and a detection value of a sensor, wherein the control unit changes, according to the past data, the open or closed state of the control valve based on the command value.
In the fluid control valve device, the control unit changes, according to the past data, the open or closed position of the control valve based on the command value. Thus, even when the spool is hard to move depending on a movement history of the spool, for example, the control unit can move the spool more swiftly to thereby more promptly vary pressure or flow rate of the fluid to be supplied to the object to control.
In the fluid control valve device, the control unit temporarily corrects the control value based on the command value when estimating a reversal of a moving direction of the spool.
In the fluid control valve device, even when, for example, the spool is hard to move due to a change in the direction of the sliding resistance to the spool, the control unit can move the spool more swiftly to thereby more promptly vary the pressure or flow rate of the fluid to be supplied to the object to control.
In the fluid control valve device, the control unit temporarily corrects the control value based on the command value when estimating a reversal of the moving direction of the spool before and after a stop of the spool.
In the fluid control valve device, even when, for example, the spool is hard to move due to a change in the direction of the sliding resistance to the spool before and after a stop of the spool, the control unit can move the spool more swiftly to thereby more promptly vary the pressure or flow rate of the fluid to be supplied to the led object to control.
In the fluid control valve device, the control unit temporarily corrects the control value based on the command value such that a force at least twice a sliding resistance, which acts on the spool, acts on the spool.
In this case, the sliding resistance force can act in the opposite direction due to the difference in pressure of fluids as a result of changes in the open or closed position of the control valve, and the force acting on the spool in the reversed moving direction approaches the equilibrium. Thus, the control unit can, for example, move the spool more swiftly to thereby more promptly vary the pressure or flow rate of the fluid to be supplied to the object to control.
In the fluid control valve device, the control unit estimates a position of the spool and determines whether to temporarily correct the control value based on the command value, according to the estimated position of the spool.
In this case, the control unit can determine the necessity of correction of the control amount (control value) more accurately on the basis of the estimated position of the spool, for example.
An exemplary embodiment of the present invention will be disclosed below. The configuration of the embodiment described below and actions and results (effects) achieved by the configuration are for illustrative only. The present invention can also be achieved by any configuration other than the configuration disclosed in the embodiment described below. The present invention can achieve at least one of various effects (including derivative effects) to be achieved by the configuration. In this specification, ordinal numbers are used to simply distinguish components or parts and regions and are not intended to indicate any order of priority or precedence.
Configuration of Fluid Control Valve Device
As illustrated in
The spool 12 is housed axially movably inside the cylinder face 11a. The spool 12 includes two large-diameter parts 12a and a small-diameter part 12b. The small-diameter part 12b is disposed between the two large-diameter parts 12a. A clearance between outer surfaces 12c of the large-diameter parts 12a and the cylinder face 11a may be set to, for example, about 10 micrometers. The small-diameter part 12b is a recess 12d extending annularly along the circumference of the spool 12. The housing 11 is provided with a chamber Ro2 between the small-diameter part 12b and the cylinder face 11a.
One of the two large-diameter parts 12a, i.e., the left large-diameter part 12a in the axial direction in
The housing 11 includes the chamber Rp on one side in the axial direction of the spool 12, i.e., the left side in
The housing 11 includes a chamber Ro1 on the other side in the axial direction of the spool 12, i.e., on the right side in
The chamber Ro1 communicates with the chamber Ro2 via a passage 12e in the spool 12. The chamber Ro1 communicates with the chamber Ro2 via the passage 12e having a relatively low resistance, so that a fluid pressure in the chamber Ro1 can be regarded substantially same as a fluid pressure in the chamber Ro2. Thus, the chamber Ro1 and the chamber Ro2 can be regarded as the same chamber Ro. The chamber Ro1 and the chamber Ro2 may communicate with each other via a passage in the housing 11. The chamber Ro is an exemplary supply pressure chamber and may be referred to also as a servo pressure chamber. The spool 12 receives a force from the fluid pressure in the chamber Ro toward one side in the axial direction. The fluid pressure in the chamber Ro is an exemplary supply pressure and one side in the axial direction is an exemplary second direction.
The housing 11 is provided with ports 11p, 11h, 11d, and 11o in the cylinder face 11a. The ports 11p, 11h, 11d, and 11o may be referred to as openings. The ports 11p, 11h, 11d, and 11o constitute part of a fluid passage.
The port lip is open to one side in the axial direction of the cylinder face 11a, that is, to the left in
When the spool 12 is located at the position p1 as illustrated in
When the spool 12 is located at the position p1 as illustrated in
While the spool 12 is located at any of the positions p1 to p3 as illustrated in
The port 11h communicates with a pressure unit via a passage 50h. The pressure unit includes a pump 30 that is driven by a motor 31, and an accumulator 32. The pump 30 is, for example, a displacement pump, and suctions a fluid from a drain 33 of a reservoir, for example, and ejects the fluid to the passage 50h. A pressure in the passage 50h can be regulated to a higher level than in the drain 33. The accumulator 32 can store therein the fluid at the regulated pressure. The accumulator 32 may be referred to as a pressure accumulator. With the spool 12 at the position p3 illustrated in
The port 11d communicates with the drain 33 via a passage 50d. When the spool 12 is located at the position p1 illustrated in
The control valve 20 includes a valve 21 that is disposed between the passage 50p communicating with the port lip and the passage 50h, and the valve 22 that is disposed between the passage 50p and the passage 50d. The valves 21 and 22 each include an electrically controlled mover (valve element, not illustrated), and change its open or closed position depending on the position of the mover. According to such structure, the larger the opening of the valve 21 is or the smaller the opening of the valve 22 is, the higher the fluid pressure in the chamber Rp is. The smaller the opening of the valve 21 is or the larger the opening of the valve 22 is, the lower the fluid pressure in the chamber Rp is. The valves 21 and 22 may be formed as valves with variable opening, such as a linear valve. The valve 21 may be referred to as a pressure increasing valve. The valve 22 may be referred to as a pressure reducing valve. The positions of the variable parts of the control valve 20, or the open or closed positions of the valves 21 and 22 such as the opening of the valves 21 and 22 and the flow rate of the fluid passing through the valves 21 and 22 are controlled by a not-illustrated control unit. The valve 21 is, for example, what is called a normally-closed type, and is thus closed when de-energized. The valve 22 is, for example, what is called a normally-open type, and is thus open when de-energized.
In addition, as illustrated in
Operation of Fluid Control Valve Device
Although not illustrated, while the valve 21 is open and the valve 22 is closed, the chamber Rp communicates with the pump 30 or the accumulator 32 via the port 11p, the passage 50p, the valve 21, and the passage 50h. In this case, upon receiving a larger force toward the other side in the axial direction (rightward in
When the valve 21 is opened and the valve 22 is closed from the positions in
Sliding Resistance of Spool
The inventors have found through their assiduous research that the force from sliding resistance between the spool 12 and the cylinder face 11a caused by, for example, the seal member 13, may affect the equilibrium of the spool 12. For example, when moving from the position in
The inventors have further found that, due to the equilibrium of forces acting on the spool 12 as described above, the spool 12 may be easier or harder to move depending on the combination of the movement history of the spool 12 and the intended moving direction of the spool 12. Specifically, when moving toward one side in the axial direction and stops, for example, the spool 12 stops, receiving the sliding resistance force in the direction opposite to the moving direction, that is, toward the other side in the axial direction (case A1). In the case A1, the seal member 13 is elastically deformed into a certain shape or posture by a force from the spool 12 and the cylinder face 11a, i.e., a force corresponding to the sliding resistance force. The shape or posture in this case will be referred to as a first shape and a first posture. In the case A1, while the spool 12 is moved toward one side in the axial direction (case A11), the direction of the force acting on the seal member 13 from the spool 12 and the cylinder face 11a does not change, so that the seal member 13 does not greatly change in shape and posture from the first shape and the first posture. Thus, the spool 12 can be relatively smoothly moved through the regulation of the pressures in the chamber Rp and the chamber Ro. In contrast, in the case A1, while the spool 12 is moved toward the other side in the axial direction (case A12), the direction of the force acting on the seal member 13 from the spool 12 and the cylinder face 11a changes, so that the seal member 13 changes from the first shape and the first posture into a second shape and a second posture which are axially opposite to the first shape and the first posture. Thus, in the case A12, along with the change in the moving direction of the spool 12, or the direction of the sliding resistance, the spool 12 is harder to move than in the case A11 since the deformation of the seal member 13 requires energy. Similarly, when the spool 12 is moved toward the other side in the axial direction and stops (case A2), the spool 12 is harder to move toward one side in the axial direction (case A21) than toward the other side in the axial direction (case A22). A similar phenomenon occurs when the direction of the sliding resistance reverses before and after the stop, regardless of the structure including the seal member 13. The similar phenomenon also occurs when the moving direction of the spool 12 quickly reverses with substantially no stop.
Controller of Fluid Control Valve Device
As described above, the inventors have found that the spool 12 is harder to move when the moving direction of the spool 12 reverses than when the moving direction of the spool 12 remains unchanged. In view of this, in the embodiment, a controller 50 (see
The control unit 51 includes, for example, a control amount calculator 51a, a correction necessity determiner 51b, a control amount corrector 51c, a control signal output 51d, and a data writer 51e.
The control amount calculator 51a calculates, on the basis of, for example, a command signal received from an external device, the control amount of the control valve 20, e.g., flow rates, openings, and positions of the valves 21 and 22. The control amount calculator 51a calculates, for example, the control amount for feedback control.
The correction necessity determiner 51b determines, on the basis of acquired data, whether the control amount needs to be corrected, i.e., whether the moving direction of the spool 12 is to start reversing. In this case, the correction necessity determiner 51b can determine whether to correct on the basis of current data and data stored in the storage 52. The data stored in the storage 52 includes history data (past data). Examples of data used for determining the necessity of correction include data indicating the control amount or status of the control valve 20, data indicating an estimated position of the spool 12, data indicating the moving direction of the spool 12, and data indicating detection values of pressure detected by the pressure sensors 41 and 42. Data indicating the control status includes, for example, data that enables the statuses of pressure increasing, pressure decreasing, and pressure maintaining to be distinguished, and may be flags associated with the respective statuses by way of example. The control amount and the control statuses are exemplary control values of the control unit 51. The estimated position and the moving direction of the spool 12 are exemplary values calculated by the control unit 51.
When the correction necessity determiner 51b determines the necessity of correction of the control amount, the control amount corrector 51c adds a correction amount to (or subtracts the correction amount from) the control amount.
The control signal output 51d outputs to the control-valve drive circuit 53 a command signal that corresponds to a corrected or non-corrected control amount.
The data writer 51e writes, to the storage 52, data for later use in determining the necessity of correction. The data serves as history data (past data) of the control amounts or the detection values at later correction-necessity determination timing. The storage 52 is, for example, a random access memory (RAM).
The control unit 51 is, for example, a central processing unit (CPU) that operates by software. At least part of the control unit 51 may be hardware, such as a field programmable gate array (FPGA), a programmable logic device (PLD), a digital signal processor (DSP), and an application specific integrated circuit (ASIC).
The control-valve drive circuit 53 receives a control signal from the control signal output 51d and applies electric power to the valves 21 and 22 in accordance with the control signal to control the operation of the valves 21 and 22.
Determination on Whether to Correct Control Amount
The correction necessity determiner 51b next determines the necessity of correction on the basis of the data acquired at S1 (S2).
Determination on Whether to Correct Based on History of Control Status
At S2, the correction necessity determiner 51b can determine the necessity of correction on the basis of, for example, a history of the control statuses of the valves 21 and 22, specifically, open or closed control statuses. As described above, with the valve 21 opened or the valve 22 closed, the spool 12 moves rightward in
(a-1) Pressure increasing control over the valves 21 and 22 are changed to pressure decreasing control over the valves 21 and 22. In this case, correction requirements may additionally include a condition that the valves 21 and 22 are continuously controlled under the pressure increasing control for a first threshold time or longer.
(a-2) Pressure decreasing control over the valves 21 and 22 are changed to pressure increasing control over the valves 21 and 22. In this case, correction requirements may additionally include a condition that the valves 21 and 22 are continuously controlled under the pressure decreasing control for the first threshold time or longer.
(a-3) The valves 21 and 22 are controlled under pressure maintaining control after the pressure increasing control, and the maintaining control is changed to the pressure increasing control. This is because the spool 12 under the pressure maintaining control after the stop of the pressure increasing control moves in a pressure decreasing direction (leftward in
(a-4) The valves 21 and 22 are controlled under the pressure maintaining control after the pressure decreasing control, and the maintaining control is changed to the pressure decreasing control. This is because the spool 12 under the pressure maintaining control after the stop of the pressure increasing control moves in a pressure increasing direction (rightward in
Determination on Whether to Correct Based on Estimation of Spool Position
At S2, the correction necessity determiner 51b can more accurately determine the necessity of correction on the basis of, for example, an estimated position of the spool 12. The moving direction of the spool 12 may be acquired from changes in position of the spool 12 over time or on the basis of the changes in position of the spool 12 over time and the control status of the spool 12.
Method for Estimating Spool Position (1): Position Estimation Based on Detected Pressures
The correction necessity determiner 51b can estimate the position of the spool 12 on the basis of, for example, a detection value of pressure detected by the pressure sensor 42. The pressure sensor 42 detects pressure in the chamber Ro. The pressure in the chamber Ro may be referred to as a servo pressure or a supply pressure. The pressure detection value of the pressure sensor 42 varies according to the position of the spool 12. For example, the pressure detection value of the pressure sensor 42 under the condition of
Specifically, for example, under the control of the control unit 51 to increase the opening of the valve 21 or decrease the opening of the valve 22, that is, under pressure increasing control, when a difference between a pressure detection value of the pressure sensor 42 at the start of the pressure increasing control (past data) and a current pressure detection value of the pressure sensor 42 is equal to or greater than a predetermined threshold, the correction necessity determiner 51b can regard the spool 12 as having reached the position p3 of
Method for Estimating Spool Position (2): Position Estimation Based on Control Amount of Control Valve during Pressure Increasing Control or Pressure Decreasing Control
The correction necessity determiner 51b can estimate the position of the spool 12 on the basis of, for example, the control amounts of the valves 21 and 22. The position of the spool 12 is an exemplary value calculated by the control unit 51. As described above, the position of the spool 12 varies depending on the control statuses, or the open and closed positions of the valves 21 and 22. Specifically, during the pressure increasing control, for example, a current position x(i) of the spool 12 can be calculated by expression (1) given below:
x(i)=x(i−1)+qi×t/A (1)
where i denotes a parameter indicating a time step of calculation, i denotes a current time step and i−1 denotes a preceding time step; x(i−1) denotes the position of the spool 12 at the preceding time step i−1 (past data); qi denotes the flow rate of fluid passing through the valves 21 and 22 (flow rate in pressure increasing); t denotes a calculation cycle, specifically, a time interval between time steps; and A denotes a cross-sectional area of the spool 12. The position estimation of the spool 12 by expression (1) is based on a technical idea that the spool 12 moves rightward in
During the pressure decreasing control, the current position x(i) of the spool 12 can be calculated by expression (2) given below:
x(i)=x(i−1)+qd×t/A (2)
where qd denotes the flow rate of fluid passing through the valves 21 and 22 (flow rate in pressure decreasing). The position estimation of the spool 12 by expression (2) is based on a technical idea that the spool 12 moves leftward in
Method for Estimating Spool Position (3): Position Estimation Based on Elapsed Time in Maintained State
As described above, when the positions of the valves 21 and 22 are maintained to hold the spool 12 at the position p2 between the position p1 and the position p3, the spool 12 moves toward the equilibrium position in accordance with the open and closed positions of the valves 21 and 22 and stops at the equilibrium position, after the valves 21 and 22 are maintained in position. In this case, the correction necessity determiner 51b can calculate the position of the spool 12 by, for example, expression (3) given below:
x(i)=x(i0)+s×f(i−i0) (3)
where i0 denotes the time step at the start of the maintaining control of the valves 21 and 22; x(i0) denotes the position of the spool 12 at the start of the maintaining control (past data); i−i0 denotes the number of time steps elapsed since the start of the maintaining control of the valves 21 and 22 (elapsed time); and f(i−i0) denotes the position of the spool 12 corresponding to the number of elapsed time steps. For example, f(i−i0) may be set as a map indicating a function of the number of time steps and a value corresponding to the number of time steps. f(i−i0) may be set by, for example, an experiment or simulation conducted in advance. In addition, s denotes a sign function according to the moving direction of the spool 12. For example, s is set to +1 when the moving direction of the spool 12 is rightward in
During the pressure increasing control or the pressure decreasing control of the valves 21 and 22 by the controller 50, the correction necessity determiner 51b can estimate the position of the spool 12 by expression (1) or expression (2). During the pressure maintaining control of the valves 21 and 22 by the controller 50, the correction necessity determiner 51b can estimate the position of the spool 12 by expression (3).
The correction necessity determiner 51b can determine the necessity of correction on the basis of the estimated position of the spool 12. Specifically, the correction necessity determiner 51b can estimate the reversal of the spool 12 or the reversal of the spool 12 after the stop in the following conditions (b-1) to (b-4), for example, and can determine that the correction is required.
(b-1) The pressure decreasing control is initiated when the spool 12 is located at the position p3 in an immediately preceding time step. Condition (b-1) corresponds to a situation that the pressure decreasing control is initiated immediately after the end of the pressure increasing control.
(b-2) The pressure increasing control is initiated when the spool 12 is located at the position p1 in an immediately preceding time step. Condition (b-2) corresponds to a situation that the pressure increasing control is initiated immediately after the end of the pressure decreasing control.
(b-3) The pressure increasing control is initiated when the spool 12 is located at the position p2 between the position p1 and the position p3 in an immediately preceding time step and the moving direction of the spool 12 to the position p2 is the pressure decreasing direction (leftward in
(b-4) The pressure decreasing control is initiated when the spool 12 is located at the position p2 between the position p1 and the position p3 in an immediately preceding time step and the moving direction of the spool 12 toward the position p2 is the pressure increasing direction (rightward in
Under the conditions (b-1) to (b-4) for determining the necessity of correction, the necessity for correcting the control amount can be further accurately determined, taking the estimated position of the spool 12 into account.
If the correction necessity determiner 51b determines that the control amount needs to be corrected (Yes at S3), the control amount corrector 51c temporarily corrects the control amount for a certain period of time (S4). If the correction necessity determiner 51b does not determine that the control amount needs to be corrected (No at S3), the control amount corrector 51c refrains from correcting the control amount.
First, the changes over time in comparative example C1 with no increase in the control amount unlike the embodiment is described. During the pressure increasing control up to time t1, the valve 21 is maintained at a certain flow rate in accordance with the opening. During the pressure maintaining control from time t1 to time t2, substantially no fluid flows through the valve 21. During the pressure increasing control from time t2, the valve 21 is again maintained at the certain flow rate.
Along with the changes in the control statuses of the valves 21 and 22, the spool 12 gradually moves from the position p3 under the pressure increasing control up to time 1 to the position p2 under the pressure maintaining control up to time t2. The moving direction of the spool 12 in this case is the pressure decreasing direction.
At time t2 the pressure maintaining control over the valve 21 is switched to the pressure increasing control and the flow rate of the valve 21 is increased. However, the spool 12 move in a direction different from the moving direction before the stop (pressure decreasing direction), so that large sliding resistance occurs. Thus, with the comparative example C1, the spool 12 does not start moving until time t4 and both the pilot pressure Pp and the servo pressure Po delay in rising.
In contrast, with the embodiment C2, the flow rate (opening) of the valve 21 is temporarily corrected to an increased rate for the period from time t2 to time t3. As a result, the pilot pressure Pp increases over the period from time t2 to time t3 and the spool 12 starts moving at time t3 earlier than the moving start time t4 in comparative example C1, so that both the pilot pressure Pp and the servo pressure Po start rising earlier than in comparative example C1.
When the servo pressure Po is higher by ΔP than the pilot pressure Pp in the pressure maintaining control as illustrated in
q
c≥2·k·ΔP/tc (4)
where qc denotes a corrected flow rate; k denotes a coefficient; ΔP denotes a difference in pressure between the pilot pressure Pp and the servo pressure Po, corresponding to the sliding resistance force; and tc denotes correction time (=t3−t2). The coefficient k is, for example, a reciprocal of a stiffness value of the chamber Rp. By such a correction of the control amounts of the valves 21 and 22, the sliding resistance force can act in the opposite direction due to the difference in pressure of fluids in the chambers Rp and Ro. That is, the force acting on the spool 12 in the reversed moving direction approaches the equilibrium, so that the spool 12 can move more swiftly to more quickly vary the pressure or the flow rate of the fluid to be supplied to the object to control. The valve 22 is controlled from time t2 to time t3 to increase a decrease in the flow rate or opening.
As described above, in the embodiment, the control unit 51 changes the open or closed positions of the valves 21 and 22 (control valve 20) on the basis of the past data stored in the storage 52. Specifically, when the correction necessity determiner 51b determines that the control amounts (control values) of the valves 21 and 22 need to be corrected, the control amount corrector 51c corrects the control amounts. Thus, in the embodiment, in the situation that the spool 12 is hard to move, the control unit 51 can move the spool 12 more swiftly to thereby more promptly vary the pressure or flow rate of the fluid to be supplied to the object to control.
In the embodiment, upon estimating the reversal of the moving direction of the spool 12 or the reversal of the moving direction of the spool 12 before and after a stop, the control unit 51 corrects the control amounts (control values) of the valves 21 and 22. Thus, in the embodiment, for example, even when a change in the direction of the sliding resistance to the spool 12 makes it difficult for the spool 12 to move, the control unit 51 can move the spool 12 more swiftly to thereby more promptly vary the pressure or flow rate of the fluid to be supplied to the object to control.
In the embodiment, the control unit 51 can correct the control amounts (control values) of the valves 21 and 22 such that the force at least twice the sliding resistance, which acts on the spool 12, acts on the spool 12. In this case, the sliding resistance force acts in the opposite direction by the difference in pressure of fluids in the chambers Rp and Ro as a result of the changes in the open or closed positions of the valves 21 and 22, and the force acting on the spool 12 in the reversed moving direction approaches equilibrium. Thus, the control unit 51 can move the spool 12 more swiftly to thereby more quickly vary the pressure or flow rate of the fluid to be supplied to the object to control, for example.
In addition, in the embodiment, the control unit 51 can estimate the position of the spool 12 and determine the necessity of correction of the control amounts (control values) of the valves 21 and 22 on the basis of the estimated position of the spool 12. In this case, the control unit 51 can more accurately determine the necessity of correction of the control amounts (control values) on the basis of the estimated position of the spool 12, for example.
While a certain embodiment has been described, the embodiment has been presented by way of example only, and is not intended to limit the scope of the invention. Indeed, the novel configuration described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, combinations, and changes in the form of the configuration described herein may be made without departing from the spirit of the invention. The specifications of each of the elements (structure, type, direction, shape, size, length, width, thickness, height, quantity, disposition, position, material, and the like) may be changed as appropriate. For example, the past data is not limited to that described above. The past data needs to pertain to at least one of the control value by which the control unit controls the control valve, the value calculated by the control unit, and the detection values of the sensors. The determination on the necessity of correction may be made on the basis of a detection value of any sensor other than the pressure sensors, for example.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-231605 | Nov 2015 | JP | national |
This application is national stage application of International Application No. PCT/JP2016/085064, filed Nov. 25, 2016, which designates the United States, incorporated herein by reference, and which is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-231605, filed Nov. 27, 2015, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/085064 | 11/25/2016 | WO | 00 |
