Device for acquiring characteristics of solenoid valve and vehicle braking control device equipped with said device

Abstract

To provide a characteristic acquisition device of an electromagnetic valve which can properly acquire a characteristic in consideration of a hysteresis of a solenoid.SOLUTION: A characteristic acquisition device for acquiring operation characteristics Zip, Ziq of a linear-type electromagnetic valve for adjusting pressure Pa of a working fluid discharged by a fluid pump which is driven by an electric motor comprises: "a supply part for supplying a current Ia to the electromagnetic valve"; "an adjustment part for adjusting a rotation number Na of the electric motor"; "a detection part for detecting the pressure Pa"; and "a learning part for storing data Dp, Dq of the pressure Pa to the current Ia, and deciding the operation characteristics Zip. Ziq on the basis of the data Dp Dq". When the supply part keeps the current Ia constant, and the adjustment part changes the rotation number Na and then keeps it constant, the learning part stores the data Dp, Dq.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a characteristic acquisition device for a solenoid valve and a braking control device for a vehicle equipped with the device. [Background technology]

[0002] Patent Document 1 describes an operation characteristic acquisition device that acquires operation characteristics close to the true operation characteristics when learning the operation characteristics of a linear valve. Specifically, in the operation characteristic acquisition device, for a target linear valve, the supply current to the coil is held for a holding period and then gradually changed for a gradual change period. An open-valve determination threshold is determined based on the change in hydraulic pressure during the holding period. When the hydraulic pressure reaches the open-valve determination threshold during the gradual change period, the linear valve is considered to have switched from a closed state to an open state, and the differential pressure between the front and rear ends and the supply current value are detected and acquired as a data pair. Because the open-valve determination threshold is determined based on the change in hydraulic pressure during the holding period, even if there is a leak in the booster linear valve, it is possible to accurately detect whether the booster linear valve has switched from a closed state to an open state, thereby acquiring characteristics close to the true operation characteristics. In other words, Patent Document 1 describes a method for acquiring the operation characteristics of a linear valve that switches from a closed state to an open state and is boosted by introducing high pressure from an accumulator.

[0003] The applicant has developed a braking control device employing a linear solenoid valve (also called a "pressure regulating valve") that throttles the flow of hydraulic fluid (brake fluid) discharged from a fluid pump (see, for example, Patent Document 2). When acquiring the operating characteristics (characteristics of differential pressure versus current, also called "IP characteristics") of such a pressure regulating valve, the influence of hysteresis of the pressure regulating valve (particularly the solenoid) must be taken into consideration. Specifically, in Patent Document 1, the relationship between current and differential pressure during the retention period is acquired after the supply of current to the coil of the pressure regulating valve is maintained. However, if this retention period is long enough, it may become unclear whether the solenoid is pushing against the fluid force of the brake fluid (corresponding to the pressure-increasing characteristics of the pressure regulating valve) or being pushed against (corresponding to the pressure-decreasing characteristics of the pressure regulating valve). For this reason, it is desirable to consider the hysteresis of the solenoid when acquiring the IP characteristics of the pressure regulating valve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-165913 [Patent Document 2] Japanese Patent Application Publication No. 2019-059294 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a characteristic acquisition device for acquiring the operating characteristics of a linear solenoid valve, which takes into account the hysteresis of the solenoid and can acquire the characteristics appropriately. [Means for solving the problem]

[0006] The characteristic acquisition device (DT) according to the present invention acquires the operating characteristics (Zip, Ziq) of a linear solenoid valve (UA) that adjusts the pressure (Pa) of a working fluid (BF) discharged by a fluid pump (QA) driven by an electric motor (MA), and comprises a "supply unit (DU) that supplies a current (Ia) to the solenoid valve (UA)", an "adjustment unit (DM) that adjusts the rotation speed (Na) of the electric motor (MA)", a "detection unit (PA) that detects the pressure (Pa), and a learning unit (DG) that stores data (Dp, Dq) of the pressure (Pa) relative to the current (Ia) and determines the operating characteristics (Zip, Ziq) based on the data (Dp, Dq). The learning unit (DG) stores the data (Dp, Dq) when the supply unit (DU) maintains the current (Ia) constant and the adjustment unit (DM) changes and then maintains the rotation speed (Na) constant.

[0007] For example, in the characteristic acquisition device (DT) according to the present invention, the learning unit (DG) determines the operating characteristic (Zip) when the pressure (Pa) is increased based on the data (Dp) when the adjustment unit (DM) reduces the rotation speed (Na) and then maintains it constant. Also, the learning unit (DG) determines the operating characteristic (Ziq) when the pressure (Pa) is decreased based on the data (Dq) when the adjustment unit (DM) increases the rotation speed (Na) and then maintains it constant.

[0008] Because the solenoid SD of the linear solenoid valve UA (pressure regulating valve) has hysteresis, its operating characteristics may not uniquely determine the regulated pressure Pa adjusted by the pressure regulating valve UA even if the supply current Ia is the same. With the above configuration, the relationship between the solenoid SD and the fluid force Fb of the brake fluid BF is clarified by changes in the motor rotation speed Na. This eliminates the effects of hysteresis, allowing Zip and Ziq to be accurately determined.

[0009] The vehicle braking control device (SC) of the present invention adjusts the wheel pressure (Pw), which is the pressure of the brake fluid (BF) in the wheel cylinder (CW) provided on the wheel (WH), and comprises a "fluid pump (QA) driven by an electric motor (MA)", "linear solenoid valves (UA, UB) that control the brake fluid (BF) discharged by the fluid pump (QA) to an adjusted pressure (Pa, Pb) and adjust the wheel pressure (Pw) using the adjusted pressure (Pa, Pb)", and "a controller (ECU) that controls the electric motor (MA) and the solenoid valves (UA, UB)". Then, when the controller (ECU) maintains the currents (Ia, Ib) supplied to the solenoid valves (UA, UB) constant and changes and then maintains the rotation speed (Na) of the electric motor (MA) constant, it acquires data (Dpa, Dqa, Dpb, Dqb) of the regulated pressures (Pa, Pb) relative to the currents (Ia, Ib) and determines the operating characteristics (Zipa, Ziqa, Zipb, Ziqb) of the solenoid valves (UA, UB) based on the data (Dpa, Dqa, Dpb, Dqb). Furthermore, the controller (ECU) controls the regulated pressures (Pa, Pb) based on the operating characteristics (Zipa, Ziqa, Zipb, Ziqb).

[0010] According to the above configuration, the influence of the hysteresis of the solenoid SD is compensated for and the operating characteristics (Zip, etc.) of the linear solenoid valve (UA, etc.) are determined. That is, the solenoid valve is controlled based on the appropriately acquired operating characteristics, so that the pressure Pw of the wheel cylinder CW can be adjusted with high precision. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram for explaining an embodiment of a characteristic acquisition device DT for a solenoid valve according to the present invention. [Figure 2] 10A and 10B are a time series diagram for explaining the operation of acquiring data Dp during pressure increase, and a characteristic diagram for explaining the operating characteristic Zip. [Figure 3] 10A and 10B are a time series diagram for explaining the operation of acquiring data Dq and a characteristic diagram for explaining the operating characteristic Ziq during pressure reduction. [Figure 4] 1 is a schematic diagram for explaining a first configuration example of a vehicle braking control device SC equipped with a characteristic acquisition device DT. [Figure 5] 10 is a schematic diagram for explaining a second configuration example of a vehicle braking control device SC equipped with a characteristic acquisition device DT. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Symbols of components> In the following explanation, components, signals, values, and other elements with the same symbol, such as "CW," have the same function. The subscripts "f" and "r" added to the end of various symbols related to wheels are generic symbols that indicate whether the element relates to the front or rear wheels. Specifically, "f" indicates "element related to the front wheels," and "r" indicates "element related to the rear wheels." For example, a wheel cylinder CW is written as "front wheel cylinder CWf, rear wheel cylinder CWr." Furthermore, the subscripts "f" and "r" may be omitted. When omitted, each symbol represents its generic name.

[0013] <Embodiment of the characteristic acquisition device DT> An embodiment of a characteristic acquisition device DT for a solenoid valve UA according to the present invention will be described with reference to the schematic diagram of Fig. 1. The solenoid valve UA (also called a "pressure regulating valve") is a normally open linear solenoid valve whose valve opening amount (lift amount) is continuously controlled based on the energization state (for example, the supply current). The linear solenoid valve UA is also called a "proportional valve" or a "differential pressure valve."

[0014] <Pressure Regulating Valve UA> First, the pressure regulating valve UA will be described. The pressure regulating valve UA is disposed in a return path HK (fluid path) connecting the suction port Qi and discharge port Qo of the fluid pump QA. The suction port Qi of the fluid pump QA is also connected to a reservoir RV (atmospheric pressure reservoir). When the fluid pump QA is driven by an electric motor MA, the fluid pump QA draws brake fluid BF from the reservoir RV at the suction port Qi and discharges the brake fluid BF from the discharge port Qo. A circulating flow KN of brake fluid BF (referred to as a "circulating flow") is generated through the return path HK, including the fluid pump QA and the pressure regulating valve UA. When the circulating flow KN of brake fluid BF is throttled by the pressure regulating valve UA, the hydraulic pressure Pa (referred to as an "adjusted pressure") between the discharge port Qo of the fluid pump QA and the pressure regulating valve UA is increased from atmospheric pressure. The regulated pressure Pa is also called "differential pressure" because it is the pressure difference from atmospheric pressure.

[0015] The pressure regulating valve UA is composed of a solenoid SD, a valve body VT, a guide member GD, a holding member HJ, and a spring member SB.

[0016] The solenoid SD is composed of a fixed coil CL and a plunger (movable iron core) PL. The fixed coil CL is fixed to the housing (e.g., guide member GD) of the pressure regulating valve UA. A valve disc VT is fixed to the plunger PL. The tip Vt of the valve disc VT is machined into a spherical shape. In the pressure regulating valve UA, the gap (i.e., the valve opening amount) Li between the spherical tip Vt and the valve seat Vz, which is machined into a conical shape on the holding member HJ, is linearly controlled according to the amount of electricity (current value) passed through the fixed coil CL. This linear control utilizes a force Fa (a downward thrust in the figure, called the "attraction force") that draws the plunger PL into the fixed coil CL when current is passed through the fixed coil CL.

[0017] The guide member GD has two holes with different diameters. The smaller of the two holes is called the "guide hole Ag," and the larger of the two holes is called the "sealing hole Af." The valve element VT is inserted into the guide hole Ag of the guide member GD so that it can move smoothly along its central axis Jv. The sealing hole Af, located on the side of the guide member GD opposite the plunger PL, is sealed by a retaining member HJ. Specifically, the retaining member HJ is press-fitted into the cylindrical inner periphery of the sealing hole Af.

[0018] The valve chamber Rz is formed by the inner periphery of the sealing hole Af of the guide member GD, the end face of the holding member HJ, and the valve disc VT. A conical valve seat Vz is formed on the end face of the holding member HJ on the side of the valve chamber Rz. An inlet hole Ai is provided in the center of the valve seat Vz. The inlet hole Ai is connected to the discharge port Qo of the fluid pump QA via a return path HK. A check valve is provided in the holding member HJ to allow brake fluid BF to move from the valve chamber Rz side to the discharge port Qo of the fluid pump QA. An outlet hole Ao is provided on the inner periphery of the sealing hole Af that forms the valve chamber Rz. The outlet hole Ao is connected to the suction port Qi of the fluid pump QA via the return path HK.

[0019] A spring member SB (e.g., a compression coil spring) is provided between the retaining member HJ and the valve disc VT to press the valve disc VT toward the plunger PL. The spring member SB presses the valve disc VT toward the plunger PL with an elastic force Fs (an upward thrust in the figure). Here, the plunger PL, valve disc VT (tip end Vt), spring member SB, valve seat Vz, and inlet hole Ai are coaxially arranged on the central axis Jv of the valve disc VT. Therefore, the suction force Fa and the elastic force Fs oppose each other on the central axis Jv of the valve disc VT.

[0020] When the supply of current Ia to the fixed coil CL is stopped and zero, no attractive force Fa is generated (i.e., Fa = 0). Therefore, the valve disc VT is pressed toward the solenoid SD (plunger PL, fixed coil CL) by the elastic force Fs, and its tip Vt is separated from the valve seat Vz. In other words, the pressure regulating valve UA is fully open.

[0021] When the fixed coil CL is energized and the current Ia supplied to the coil CL increases, the attractive force Fa increases. The attractive force Fa presses the tip Vt of the valve disc VT toward the valve seat Vz. At this time, in addition to the elastic force Fs, a force Fb (an upward thrust in the figure, referred to as the "fluid force") acts on the valve disc VT, which causes the brake fluid BF to flow into the valve chest Rz. Therefore, the valve opening Li of the pressure regulating valve UA (the gap between the tip Vt and the valve seat Vz) is determined based on the relationship between the attractive force Fa and the resultant force Fg (i.e., "Fs + Fb") of the elastic force Fs and the fluid force Fb.

[0022] The magnitude of the fluid force Fb is determined by the flow rate of the brake fluid BF passing through the gap Li and the pressure difference across the gap Li. Here, the flow rate depends on the rotation speed Na of the electric motor MA. The pressure difference is the difference between the hydraulic pressure on the suction side Qi (i.e., the adjustment pressure Pa) and the hydraulic pressure in the valve chest Rz (i.e., "0 (atmospheric pressure)"), with the position of the valve seat Vz as the reference.

[0023] Therefore, in the pressure regulating valve UA, the relationship between the supply current Ia, the motor rotation speed Na, and the regulating pressure Pa is as follows: The larger the supply current Ia, the larger the attractive force Fa, and the smaller the supply current Ia, the smaller the attractive force Fa. Therefore, when the rotation speed Na of the electric motor MA is constant (i.e., when the flow rate of the circulating flow KN is constant), the regulated pressure Pa increases as the supply current Ia increases. Conversely, the regulated pressure Pa decreases as the supply current Ia decreases. - When the supply current Ia to the pressure regulating valve UA is constant (i.e., when the suction force Fa is constant), the fluid force Fb increases as the motor rotation speed Na increases, and decreases as the motor rotation speed Na decreases. Therefore, as the motor rotation speed Na increases, the regulated pressure Pa increases. On the other hand, as the motor rotation speed Na decreases, the regulated pressure Pa decreases.

[0024] When adjusting the regulated pressure Pa in response to the supply current Ia, the pressure regulating valve UA experiences hysteresis due to magnetic hysteresis in the solenoid SD, friction of the components, etc. Here, "hysteresis" is also called "history phenomenon," and is a phenomenon in which the magnitude of the output is not uniquely determined by the input value but depends on past conditions. Because the operating characteristics of the pressure regulating valve UA have hysteresis, the value of the regulated pressure Pa differs when the supply current Ia increases and when it decreases, even if the supply current Ia is the same.

[0025] The relationship between the supply current Ia and the regulated pressure Pa (i.e., the operating characteristic of the pressure regulating valve UA, or IP characteristic) is determined by the equilibrium state between the suction force Fa and the resultant force Fg (= Fb + Fs). However, even when the supply current Ia to the pressure regulating valve UA (particularly the coil CL) is maintained constant, the resultant force Fg fluctuates slightly. For this reason, when the supply current Ia is maintained continuously for a relatively long period of time, it is unclear whether the solenoid SD (i.e., the valve disc VT) is pushing against the fluid force Fb (corresponding to pressure increase) or being pushed by the fluid force Fb (corresponding to pressure decrease).

[0026] ≪Characteristics acquisition device DT≫ The characteristic acquisition device DT acquires the operating characteristics of the pressure regulating valve UA (the characteristics of the hydraulic pressure Pa relative to the current Ia). Specifically, the operating characteristics Zip when the regulating pressure Pa is increased (also referred to as the "pressure increase characteristics") and the operating characteristics Ziq when the regulating pressure Pa is decreased (also referred to as the "pressure decrease characteristics") are acquired separately. The characteristic acquisition device DT is composed of a supply unit DU, a regulating unit DM, a detection unit PA (hydraulic pressure sensor), and a learning unit DG.

[0027] A current Ia is supplied to the pressure regulating valve UA by a supply unit DU. The supply unit DU is a drive circuit for the pressure regulating valve UA that is composed of a switching element (such as a MOS-FET). The supply unit DU is provided with a current sensor IA to detect the supply current Ia. The supply unit DU performs current feedback control, and controls the switching element so that the supply current Ia (actual value) approaches and matches the target current It, which is the target value of the supply current Ia.

[0028] The adjustment unit DM adjusts the rotation speed Na of the electric motor MA. The adjustment unit DM is a drive circuit for the electric motor MA, which is composed of switching elements (MOS-FETs, etc.). For example, in a configuration in which a brushless DC motor is used as the electric motor MA, the adjustment unit DM is provided with a three-phase bridge circuit. The adjustment unit DM is provided with a rotation speed sensor NA to detect the motor rotation speed Na. Alternatively, a rotation angle sensor KA is provided to detect the motor rotation angle Ka, and the rotation angle Ka is time-differentiated based on the rotation angle Ka to calculate the motor rotation speed Na. The adjustment unit DM performs rotation speed feedback control, controlling the switching elements so that the motor rotation speed Na (actual value) approaches and matches the target rotation speed Nt, which is the target value for the motor rotation speed Na.

[0029] The detector PA detects the regulated pressure Pa. The regulated pressure Pa is the pressure between the discharge port Qo of the fluid pump QA and the pressure regulating valve UA. In other words, the brake fluid (working fluid) BF discharged by the fluid pump QA is adjusted to the regulated pressure Pa by the pressure regulating valve UA.

[0030] The learning unit DG stores data Dp and Dq of the pressure Pa relative to the current Ia to determine the operating characteristics (IP characteristics) of the pressure regulating valve UA. The pressure regulating valve UA has hysteresis due to magnetic hysteresis of the solenoid SD, friction of the movable members, etc., so the operating characteristics of the pressure regulating valve UA differ between a characteristic Zip (pressure-increasing characteristic) when the regulated pressure Pa is increased and a characteristic Ziq (pressure-reducing characteristic) when the regulated pressure Pa is decreased. For this reason, the learning unit DG distinguishes between the pressure-increasing characteristic Zip and the pressure-reducing characteristic Ziq and acquires them separately.

[0031] Specifically, as the supply current Ia is gradually increased, a combination of the supply current Ia and the regulated pressure Pa is stored as data Dp (referred to as "pressure-increasing data") relating to the operating characteristic Zip during pressure increase. The pressure-increasing data Dp is measured and stored when the supply current Ia is maintained constant and the rotation speed Na of the electric motor MA is reduced and then maintained constant. Then, the pressure-increasing characteristic Zip is determined based on the stored pressure-increasing data Dp and stored in the learning unit DG.

[0032] Furthermore, when the supply current Ia is gradually reduced, a combination of the supply current Ia and the regulated pressure Pa is stored as data Dq (referred to as "pressure reduction data") relating to the operating characteristic Ziq during pressure reduction. The pressure reduction data Dq is measured and stored when the supply current Ia is maintained constant and the rotation speed Na of the electric motor MA is increased and then maintained constant. Then, based on the stored pressure reduction data Dq, the pressure reduction characteristic Ziq is determined and stored in the learning unit DG.

[0033] That is, in the learning unit DG, when the supply current Ia is maintained constant and the rotational speed Na of the electric motor MA is changed (increased or decreased) and then maintained constant, the pressure increase / decrease data Dp, Dq are measured and stored. Then, based on the pressure increase / decrease data Dp, Dq, pressure increase / decrease operating characteristics Zip, Ziq are determined and stored in the learning unit DG. Here, "measuring and storing the pressure increase / decrease data Dp, Dq" and "determining and storing the pressure increase / decrease operating characteristics Zip, Ziq" are also referred to as "learning."

[0034] <Learning Zip operating characteristics during pressure increase> A method for acquiring data Dp (pressure-increasing data) for calculating pressure-increasing characteristics Zip will be described below. In the following description, with regard to the rotation speed Na of the electric motor MA, a target rotation speed Nt of the electric motor MA is set by an adjustment unit DM, and control is performed so that the motor rotation speed Na (actual value) coincides with the target rotation speed Nt (target value). Also, with regard to the supply current Ia, a target current It is set by a supply unit DU, and control is performed so that the supply current Ia (actual value) coincides with the target current It (target value).

[0035] First, the electric motor MA and the pressure regulating valve UA are initially driven. This initial drive eliminates the effects of gaps in the braking device SX (gaps between friction members MS such as brake pads and rotating members KT such as brake discs, play between components, etc.) and air bubbles in the fluid path including the pressure regulating valve UA. During the initial drive, the rotational speed Na of the electric motor MA is increased to a predetermined starting rotational speed no. At the same time, the supply current Ia is increased to a predetermined starting current io. As a result, the regulating pressure Pa is increased to a predetermined starting pressure po. The predetermined starting rotational speed no and the predetermined starting current io are preset values (constants). Here, the predetermined starting current io is a value corresponding to the predetermined starting pressure po being high enough to remove air bubbles.

[0036] When the initial driving is completed, the adjustment unit DM drives the electric motor MA so that the motor rotation speed Na is constant at the first reference rotation speed np. Specifically, the target rotation speed Nt is set to the first reference rotation speed np. Then, the motor rotation speed Na (actual value) is controlled to coincide with the target rotation speed Nt (target value). Furthermore, the supply unit DU supplies power to the pressure regulating valve UA so that the supply current Ia is constant.

[0037] After the motor rotation speed Na and the supply current Ia are maintained constant, the target rotation speed Nt is reduced from the first reference rotation speed np to the first measurement rotation speed nq while the supply current Ia remains constant. As a result, the motor rotation speed Na is reduced from the first reference rotation speed np to the first measurement rotation speed nq. Thereafter, while the motor rotation speed Na is driven at a constant value of the first measurement rotation speed nq, the learning unit DG stores the supply current Ia and the regulated pressure Pa as pressure-increasing data Dp[1]. Here, the first reference rotation speed np and the first measurement rotation speed nq are preset values (constants). The first measurement rotation speed nq is smaller than the first reference rotation speed np by the first specified rotation speed nx (a preset constant). The number "n" in brackets [ ] indicates that this is the pressure-increasing data Dp acquired (i.e., detected and stored) for the nth time. Therefore, the pressure-increasing data Dp[1] is the first learning data.

[0038] When storage of the first pressure-boosting data Dp[1] is completed, the target rotation speed Nt is increased from the first measured rotation speed nq to the first reference rotation speed np. As a result, the motor rotation speed Na is increased (returned) from the first measured rotation speed nq to the first reference rotation speed np. At the same time, the target current It is increased by the predetermined current ix and maintained constant. As a result, the supply current Ia is increased by the predetermined current ix and maintained constant. Here, the predetermined current ix (also referred to as the "first predetermined current") is a predetermined value (constant) that has been set in advance.

[0039] After the motor rotation speed Na and the supply current Ia are maintained constant, the target rotation speed Nt (resulting in the motor rotation speed Na) is reduced from the first reference rotation speed np to the first measurement rotation speed nq while the target current It (resulting in the actual supply current Ia) is constant. Thereafter, while the motor rotation speed Na is driven at a constant first measurement rotation speed nq, the supply current Ia and the regulated pressure Pa are stored (learned) as pressure-increasing data Dp[2] (i.e., the second pressure-increasing data Dp).

[0040] When the storage of the second pressure-increasing data Dp[2] is completed, the motor rotation speed Na is again increased from the first measurement rotation speed nq to the first reference rotation speed np, and the supply current Ia is further increased by the first predetermined current ix and maintained at a constant state. As in the second learning, the supply current Ia is maintained at a constant state, and when the motor rotation speed Na is reduced and then maintained at a constant state, the supply current Ia and the regulated pressure Pa are learned (measured and stored) as the third pressure-increasing data Dp[3]. Thereafter, this procedure is repeated, and the pressure-increasing data Dp is sequentially learned multiple times (n times, for example, over ten).

[0041] The relationship between the supply current Ia and the regulated pressure Pa (IP characteristics during pressure increase) Zip when the supply current Ia is increased is approximated as a quadratic function based on the learned data Dp during pressure increase (i.e., n data) and the least squares method. Specifically, the quadratic polynomial Pa(Ia)=a·Ia 2 The coefficients a, b, and c are determined so that the sum of squares of the residuals (estimated values of errors) in "+b·Ia+c" is minimized. Then, this polynomial is adopted as the pressure-boosting characteristic Zip.

[0042] <Learning the operating characteristics Ziq during decompression> A method for acquiring data Dq (data during pressure reduction) for calculating the pressure reduction characteristic Ziq will now be described. Following the acquisition (detection and storage) of data Dq, the acquisition (detection and storage) of data Dq is executed. In the acquisition and calculation of data Dq, first, the adjustment unit DM drives the electric motor MA so that the motor rotation speed Na is constant at the second reference rotation speed ns. Then, the supply unit DU supplies power to the pressure adjustment valve UA so that the supply current Ia is constant. After the motor rotation speed Na and the supply current Ia are maintained constant, the motor rotation speed Na is increased from the second reference rotation speed ns to the second measurement rotation speed nu while the supply current Ia is constant. Then, while the motor rotation speed Na is driven constantly at the second measurement rotation speed nu, the learning unit DG learns (measures and stores) the supply current Ia and the regulated pressure Pa as data Dq[1]. Here, the second reference rotation speed ns and the second measurement rotation speed nu are predetermined values (constants) that have been set in advance. The second measured rotation speed nu is greater than the second reference rotation speed ns by a second predetermined rotation speed nz (a predetermined constant that has been set in advance). As with the pressure-increasing data Dq, the number "n" in brackets [ ] indicates that this is the nth pressure-decreasing data Dq. Therefore, the pressure-decreasing data Dq[1] is the first learning data during pressure reduction.

[0043] When the first learning (particularly, storage) of the data Dq[1] is completed, the motor rotation speed Na is reduced (returned) from the second measurement rotation speed nu to the second reference rotation speed ns, and the supply current Ia is reduced by a predetermined current iz and maintained constant. Here, the predetermined current iz (also referred to as the "second predetermined current") is a predetermined value (constant) that is set in advance. After the motor rotation speed Na and the supply current Ia are maintained constant, the motor rotation speed Na is increased from the second reference rotation speed ns to the second measurement rotation speed nu while the supply current Ia remains constant. Thereafter, while the motor rotation speed Na is driven at a constant second measurement rotation speed nu, the supply current Ia and the regulated pressure Pa are stored as pressure-reducing data Dq[2] (i.e., the second learning data Dq).

[0044] When the storage of the second data Dq[2] is completed, the motor rotation speed Na is again reduced from the second measurement rotation speed nu to the second reference rotation speed ns, and the supply current Ia is further reduced by the second predetermined current iz and maintained at a constant state. As in the second learning of the pressure reduction characteristic Ziq, when the supply current Ia is maintained at a constant state and the motor rotation speed Na is increased and then maintained at a constant state, the supply current Ia and the regulated pressure Pa are learned as the third pressure reduction data Dq[3]. Thereafter, this procedure is repeated, and the data Dq for the pressure reduction characteristic Ziq is sequentially learned multiple times (for example, over a dozen times).

[0045] Similar to the pressure increase characteristic Zip, the relationship Ziq between the supply current Ia and the adjusted pressure Pa when the supply current Ia is decreased (IP characteristic when the pressure is decreased) is approximated as a quadratic function based on a plurality of (i.e., n) pieces of data Dq and the least squares method. Specifically, the quadratic polynomial "Pa(Ia)=d·Ia 2 +e·Ia+h", the coefficients d, e, and h are determined so that the sum of squares of the residuals is minimized, and this is used as the pressure reduction characteristic Ziq.

[0046] When detecting the data Dp, Dq (data during pressure increase and pressure decrease) relating to the characteristics Zip, Ziq during pressure increase and pressure decrease, the data Dp, Dq during pressure increase and pressure decrease are learned (acquired) when the supply current Ia is kept constant and the rotation speed Na of the electric motor MA is changed once (i.e., increased or decreased) and then maintained constant, so as to reliably eliminate the influence of hysteresis of the pressure regulating valve UA.

[0047] The data Dp (pressure-increasing data) relating to the pressure-increasing characteristic Zip is learned when the supply current Ia is constant and the motor rotation speed Na is reduced and then maintained constant. When the motor rotation speed Na is reduced, the fluid force Fb is reduced. Therefore, under the above conditions, the solenoid SD is surely exerting the fluid force Fb. Therefore, the pressure-increasing characteristic Zip can be calculated appropriately.

[0048] The data Dq (data during pressure reduction) relating to the pressure reduction characteristic Ziq is learned when the supply current Ia is constant and the motor rotation speed Na is increased once and then maintained constant. When the motor rotation speed Na increases, the fluid force Fb also increases. Therefore, under the above conditions, a state in which the fluid force Fb presses the solenoid SD (i.e., a state opposite to that during pressure increase) is reliably realized. Therefore, the pressure reduction characteristic Ziq can be calculated appropriately.

[0049] <Processing related to determination of pressure boost characteristic Zip> 2, the learning operation of data Dp when supply current Ia is increased and the method of determining pressure-boosting characteristics Zip based on the data Dp will be described. Note that motor rotation speed Na and supply current Ia are the results of target rotation speed Nt and target current It. Therefore, by setting target rotation speed Nt and target current It, the actual motor rotation speed Na and actual supply current Ia are achieved.

[0050] First, a method for learning data Dp (pressure-increased data) relating to pressure-increased characteristics Zip will be described with reference to the time series diagram (transition diagram of state quantities over time T) in Figure 2(a). Prior to acquiring pressure-increased data Dp, initial drive is performed to close gaps between components and crush air bubbles (air bubbles) present in the brake fluid BF. In the initial drive, the adjustment pressure Pa is increased to the predetermined starting pressure po, thereby eliminating play between components and eliminating air bubbles.

[0051] The process from time t0 to time t3 is the initial drive. Specifically, at time t0, the electric motor MA is driven so that its rotational speed Na becomes the predetermined starting rotational speed no. At the same time, the supply current Ia is rapidly increased toward the predetermined starting current io. As a result, the regulated pressure Pa is increased to the predetermined starting pressure po. At time t1, the supply current Ia is maintained at the predetermined starting current io, and the regulated pressure Pa is maintained at the predetermined starting pressure po. This state continues for a predetermined time, and at time t2, the supply current Ia is reduced, and at time t3, the motor rotational speed Na is reduced.

[0052] At time t4, the process of acquiring data Dp for the pressure-increasing characteristic Zip begins. At time t4, the electric motor MA is rotated at a constant speed of "Na = np." Then, the supply current Ia to the pressure regulating valve UA is increased from "0" by a predetermined current ix at an increasing gradient Kp (the amount of change over time in the increase of the supply current Ia). Here, the increasing gradient Kp and the predetermined current ix are predetermined values (constants). At time t4, the regulated pressure Pa begins to increase as the supply current Ia increases.

[0053] At time t5, the supply current Ia is increased from "0" by a predetermined current ix to a value ia. The adjustment pressure Pa is increased in response to the supply current Ia to a value pn. From time t5, the current and rotation speed are maintained constant at "Ia=ia and Na=np", and the hydraulic pressure remains constant at "Pa=pn".

[0054] At time t6, with the supply current Ia kept constant at value ia, the motor rotation speed Na is decreased from the first reference rotation speed np to the first measurement rotation speed nq so as to decrease the fluid force Fb. As the motor rotation speed Na decreases, the adjustment pressure Pa decreases from value pn.

[0055] At time t7, the rotational speed Na of the electric motor MA becomes the first measured rotational speed nq, and thereafter the rotational speed is kept constant at "Na = nq." Accordingly, the adjustment pressure Pa becomes the value pa, and the hydraulic pressure is kept constant at "Pa = pa."

[0056] At time t8, the learning unit DG determines that the motor rotation speed Na is constant at the first measured rotation speed nq. The determination that "the rotation speed Na of the electric motor MA is constant" is made based on the fact that there is no change in the motor rotation speed Na over a predetermined determination time tx (also referred to as the "first predetermined determination time"). For example, the constant rotation speed state is determined when the amount of change dN of the motor rotation speed Na with time (i.e., the time differential value of the motor rotation speed Na) is continuously less than a first predetermined amount of change dm. Here, the first predetermined determination time tx and the first predetermined amount of change dm are threshold values for determination, and are predetermined values (constants) that are set in advance.

[0057] After time t8, which is the first predetermined determination time tx since time t7, "Ia=ia" is associated with "Pa=pa," and "Dp[1]=(ia, pa)" is stored in the learning unit DG (see (A) in the figure). Specifically, starting from time t8, the moving average value of the supply current Ia and the moving average value of the regulated pressure Pa are calculated over a predetermined measurement time tk (a preset constant). Then, the moving average value of the supply current Ia and the moving average value of the regulated pressure Pa are stored as data Dp[1].

[0058] At time t9 after the data Dp[1] has been stored, the supply current Ia is further increased by a predetermined current ix from the value ia at an increasing gradient Kp. At the same time, the motor speed Na is increased from the first measured speed nq toward the first reference speed np. At time t10, the motor speed Na reaches the first reference speed np, and thereafter, the motor speed Na is maintained at a constant speed at the first reference speed np. At time t11, the supply current Ia is increased by a predetermined current ix from the value ia to a value ib, and the adjustment pressure Pa is increased to a value pp. From time t11, "Ia = ib (constant current) and Na = np (constant speed)" are maintained, and "Pa = pp (constant hydraulic pressure)" continues.

[0059] At time t12, while the supply current Ia is maintained constant at value ib, the motor rotation speed Na is decreased from the first reference rotation speed np to the first measurement rotation speed nq so as to reduce the fluid force Fb. At time t13, the rotation speed Na of the electric motor MA becomes the first measurement rotation speed nq. At time t14, when the first predetermined judgment time tx has elapsed since time t13, it is determined that the motor rotation speed Na is constant at the first measurement rotation speed nq. At time t14, the values ib and pb are associated with each other, and the pressure-increasing data Dp[2] is stored in the learning unit DG as "(ib, pb)" (see (B) in the figure). Specifically, during a predetermined measurement time tk (a preset constant) from time t14, the moving average value of the supply current Ia and the moving average value of the regulated pressure Pa are calculated, and these are learned as the pressure-increasing data Dp[2].

[0060] From time t15 after learning of data Dp[2], the same process as above is repeated. That is, the supply current Ia is increased by a predetermined current ix at a predetermined increase gradient Kp, and the motor rotation speed Na is increased to a first reference rotation speed np and maintained at a constant rotation speed. Then, when the supply current Ia becomes constant, the motor rotation speed Na is decreased to a first measurement rotation speed nq while maintaining the constant state. Thereafter, when the motor rotation speed Na becomes constant at value nq, the supply current Ia and the regulated pressure Pa are measured. The measured supply current Ia and the regulated pressure Pa are then associated and stored as pressure-increasing data Dp. This process is repeated until the supply current Ia reaches the maximum value ie required for learning.

[0061] As explained in the above operational example, the learning unit DG of the characteristic acquisition device DT repeatedly and sequentially learns (measures and stores) pressure-increasing data Dp of the regulated pressure Pa relative to the supply current Ia when the supply current Ia is maintained constant and the motor rotation speed Na is reduced and then maintained constant. Specifically, as the supply current Ia increases, combinations of the supply current Ia and the regulated pressure Pa acquired starting from each point in time (such as t8) shown in (A) to (E) of FIG. 2(a) are sequentially learned as pressure-increasing data Dp. Then, after point t18 when the final pressure-increasing data Dp, "(ie, pe)," is stored, the pressure-increasing characteristic Zip is determined based on the multiple pressure-increasing data Dp stored in the learning unit DG.

[0062] Next, a method for determining the pressure-increasing characteristic Zip will be described with reference to the characteristic diagram of Figure 2(b). The characteristic diagram plots data Dp corresponding to the time points at which the data Dp is stored. In other words, plot points (A) to (E) in Figure 2(b) correspond to the pressure-increasing data Dp at the times (A) to (E) in Figure 2(a), respectively.

[0063] The pressure-increasing characteristic Zip is determined based on a plurality of pressure-increasing data Dp stored in the learning unit DG (see plot points (A) to (E)). For example, the pressure-increasing characteristic Zip is determined based on the quadratic function Pa(Ia)=a·Ia 2 +b·Ia+c where a, b, and c are defined as constants. The constant coefficients a, b, and c are then determined so that the sum of squares of the residuals (estimated error values) is minimized (i.e., based on the least squares method). Specifically, the pressure-boosting characteristic Zip is defined as a downwardly convex function in a characteristic diagram that shows the relationship between the supply current Ia and the regulated pressure Pa, and is stored in the learning unit DG.

[0064] In acquiring data Dp relating to the pressure-increasing characteristic Zip, the characteristic acquisition device DT does not simply adopt the condition that "the supply current Ia is constant and the motor rotation speed Na is constant," but rather adopts the condition that "the supply current Ia is constant and the motor rotation speed Na remains constant after being reduced." Because the fluid force Fb decreases as the motor rotation speed Na decreases, adopting the above acquisition condition eliminates the influence of hysteresis in the pressure regulating valve UA, and the characteristic Zip when the regulated pressure Pa is increased can be acquired with high accuracy.

[0065] In the process of acquiring the pressure-increasing data Dp described above, the supply current Ia is increased by the same amount (by the predetermined current ix) after learning the pressure-increasing data Dp. However, instead, the amount of increase in the supply current Ia may be set arbitrarily. Furthermore, the amount of increase in the supply current Ia may be set to increase as the supply current Ia increases. That is, the smaller the supply current Ia, the smaller the increase in the supply current Ia, and the denser the plot points of the pressure-increasing data Dp. On the other hand, the larger the supply current Ia, the larger the increase in the supply current Ia, and the coarser the plot points of the pressure-increasing data Dp. The more data points there are during pressure-increasing, the more accurate the pressure-increasing characteristic Zip will be, but it will take longer to acquire the data. However, by setting the amount of increase based on the magnitude of the supply current Ia, a trade-off can be achieved between the accuracy of the pressure-increasing characteristic Zip and the speed at which the pressure-increasing data Dp can be acquired.

[0066] <Processing for determining pressure reduction characteristics Ziq> 3, the learning operation of the data Dq when the supply current Ia is reduced and the method of determining the pressure-reducing characteristic Ziq based on the data Dq will be described. The data Dq (pressure-reducing data) for the pressure-reducing characteristic Ziq is acquired after the data Dq (pressure-increasing data) for the pressure-increasing characteristic Zip is acquired. As in the above, the motor rotation speed Na and the supply current Ia are the results of the target rotation speed Nt and the target current It, and therefore the actual motor rotation speed Na and the actual supply current Ia are realized by setting the target rotation speed Nt and the target current It.

[0067] First, a method for acquiring data Dq (pressure reduction data) relating to pressure reduction characteristics Ziq will be described with reference to the time series diagram of FIG. 3(a). The process for acquiring pressure reduction data Dq begins at time u0 after the process for acquiring pressure increase data Dp has been completed. Prior to time u0, the electric motor MA is driven at a constant rotation speed of Na=ns, and the supply current Ia is maintained at a constant current value ih. As a result, the adjustment pressure Pa is maintained at a constant hydraulic pressure value pg.

[0068] At time u0, the motor rotation speed Na starts to increase from the second reference rotation speed ns to the second measurement rotation speed nu so that the fluid force Fb increases while the current is constant at Ia=ih. As the motor rotation speed Na increases, from time u0, the adjustment pressure Pa is increased from the value pg.

[0069] At time u1, the rotational speed Na of the electric motor MA becomes the second measured rotational speed nu. After that, the rotational speed remains constant at "Na = nu." Accordingly, the adjustment pressure Pa becomes the value ph, and the hydraulic pressure remains constant at "Pa = ph."

[0070] At time u2, the learning unit DG determines that the motor rotation speed Na is in a constant state at the second measured rotation speed nu. As in the case of the pressure-increasing characteristic Zip, the "constant rotation speed state" is determined when the motor rotation speed Na does not change over a predetermined determination time tz (also referred to as the "second predetermined determination time"), even in the case of the pressure-decreasing characteristic Ziq. For example, the constant rotation speed state is determined when the amount of change dN over time of the motor rotation speed Na is continuously less than a second predetermined change amount dn. Here, the second predetermined determination time tz and the second predetermined change amount dn are predetermined values (constants) that are set in advance.

[0071] After time u2, "Pa=ph" and "Ia=ih" are associated with each other, and "Dq[1]=(ih,ph)" is stored in the learning unit DG (see (H) in the figure). Specifically, as in the case of the pressure-increasing characteristic Zip, the moving average value of the supply current Ia and the moving average value of the regulated pressure Pa are calculated over a predetermined measurement time tk (constant) starting from time u2. Then, the moving average values of the supply current Ia and the moving average values of the regulated pressure Pa are learned as pressure-decreasing data Dq[1].

[0072] At time u3 after the storage of the pressure-reducing data Dq[1] is completed, the supply current Ia is reduced by a predetermined current iz from the value ih at a reduction gradient Kq. At the same time, the motor speed Na is reduced from the second measured speed nu toward the second reference speed ns. At time u4, the motor speed Na reaches the second reference speed ns, and thereafter the speed is maintained constant at "Na = ns". At time u5, the supply current Ia is reduced by a predetermined current iz from the value ih to the value ij. Correspondingly, the adjustment pressure Pa is reduced to the value ps. From time u5 onwards, "Ia = ij (constant current state) and Na = ns (constant speed state)" are maintained, and "Pa = ps (constant hydraulic pressure state)" continues.

[0073] At time u6, while the supply current Ia is kept constant at value ij, the motor speed Na is increased from the second reference speed ns to the second measurement speed nu so as to increase the fluid force Fb. At time u7, the speed Na of the electric motor MA reaches the second measurement speed nu. Accordingly, the regulating pressure Pa is increased from value ps to value pj and then maintained constant at value pj.

[0074] At time u8, it is determined that the rotation speed is constant, i.e., "Na=nu." After that, "Ia=ij" is associated with "Pa=pj," and "Dq[2]=(ij,pj)" is stored (see (J) in the figure). For example, over a predetermined measurement time tk (a preset constant) from time u8, the moving average value of the supply current Ia and the moving average value of the adjustment pressure Pa are calculated, and these are learned as pressure-reducing data Dq[2].

[0075] From time u9 after the storage of the pressure-reducing data Dq[2] is completed, the same process as described above is repeated. That is, the supply current Ia is reduced by a predetermined current iz at a predetermined reduction gradient Kq, and the motor rotation speed Na is reduced from the second measurement rotation speed nu to the second reference rotation speed ns and maintained constant. Then, when the supply current Ia becomes constant, the motor rotation speed Na is increased from the second reference rotation speed ns to the second measurement rotation speed nu while maintaining the constant state. Thereafter, when the motor rotation speed Na becomes constant, the supply current Ia and the regulated pressure Pa are measured, associated with each other, and stored as pressure-reducing data Dq. This process is repeated until the minimum value im required for measuring the supply current Ia is reached.

[0076] As explained in the above operational example, when the supply current Ia is maintained constant and the motor rotation speed Na is increased and then maintained constant, the learning unit DG of the characteristic acquisition device DT associates the supply current Ia with the regulated pressure Pa and repeatedly learns (measures and stores) this as pressure-reducing data Dq. Specifically, as the supply current Ia decreases, combinations of the supply current Ia and the regulated pressure Pa acquired starting from each point in time (such as u2) shown in (H) to (M) of FIG. 3(a) are sequentially learned as pressure-reducing data Dq. Then, after point u13 when the final pressure-reducing data Dq, "(im, pm)," is stored, pressure-reducing characteristics Ziq are determined based on the multiple pieces of pressure-reducing data Dq.

[0077] Next, a method for determining the pressure-reducing characteristic Ziq will be described with reference to the characteristic diagram of Fig. 3(b). As above, each piece of pressure-reducing data Dq is plotted in the characteristic diagram in correspondence with the time point at which it is stored. That is, plot points (H) to (M) in Fig. 3(b) correspond to the pressure-reducing data Dq at times (H) to (M) in Fig. 3(a), respectively.

[0078] The pressure reduction characteristic Ziq is determined based on a plurality of pressure reduction data Dq stored in the learning unit DG (see plot points (H) to (M)). For example, the pressure reduction characteristic Ziq is determined based on the quadratic function Pa(Ia)=d·Ia 2+e·Ia+h where d, e, and h are defined as constants. The constant coefficients d, e, and h are then determined so that the sum of squares of the residuals (estimated values of errors) is minimized (i.e., based on the least squares method). Specifically, the pressure-reducing characteristic Ziq is defined as a downwardly convex function in a characteristic diagram showing the relationship between the supply current Ia and the regulated pressure Pa, and is stored in the learning unit DG.

[0079] As with the pressure-increase data Dp, the characteristic acquisition device DT does not simply adopt the condition "when the supply current Ia is constant and the motor rotation speed Na is constant" when acquiring the pressure-decrease data Dq. In other words, the condition "when the supply current Ia is constant and the motor rotation speed Na remains constant after being reduced" is adopted for acquiring the pressure-decrease data Dq. Because the fluid force Fb increases with an increase in the motor rotation speed Na, adopting the above acquisition condition eliminates the influence of hysteresis in the pressure regulating valve UA, and the operating characteristic Ziq when the regulated pressure Pa is reduced can be accurately acquired.

[0080] As in the case of the pressure-increase characteristic Zip, in the process of acquiring the data Dq for the pressure-reduction characteristic Ziq, the supply current Ia is reduced by the same amount (by the predetermined current iz) after learning the pressure-reduction data Dq. However, instead, the amount of reduction in the supply current Ia can be set arbitrarily. Furthermore, the amount of reduction in the supply current Ia may be set to decrease as the supply current Ia decreases. That is, the greater the supply current Ia, the greater the amount of reduction in the supply current Ia, and the coarser the plot points of the pressure-reduction data Dq. On the other hand, the smaller the supply current Ia, the smaller the amount of reduction in the supply current Ia, and the denser the plot points of the pressure-reduction data Dq. For the reasons described above, a trade-off between the accuracy of the pressure-reduction characteristic Ziq and the speed at which the pressure-reduction data Dq is acquired can be achieved.

[0081] The pressure reduction characteristic Ziq may be estimated from the pressure increase characteristic Zip. The hysteresis of the pressure regulating valve UA is known. Therefore, the pressure reduction characteristic Ziq can be calculated based on the pressure increase characteristic Zip. In this case, the measurement process of the pressure reduction data Dq is omitted, and the pressure reduction data Dq is not actually measured. Estimating the pressure reduction characteristic Ziq reduces the time required to learn the operating characteristics Zip and Ziq.

[0082] <First Configuration Example of Brake Control Device SC Equipped with Characteristics Acquisition Device DT> A first configuration example of a braking control device SC for a vehicle equipped with a characteristic acquisition device DT will be described with reference to the schematic diagram of Figure 4. In the braking control device SC, a braking force Fw (for example, a braking force due to friction between a brake pad and a brake disc) acting on a wheel WH is generated and adjusted by adjusting the wheel pressure Pw using a pressure regulating valve UA. The hydraulic circuit in the first configuration example of the braking control device SC is publicly known from JP 2020-032833 A and the like, and will be briefly described below.

[0083] The brake control device SC is composed of an operation amount sensor BA, a hydraulic unit HU, and a controller ECU. The hydraulic unit HU includes an apply unit AU including a master cylinder CM, and a pressurizing unit KU.

[0084] The operation amount sensor BA detects the operation amount Ba (referred to as the "braking operation amount") of a brake operating member BP (e.g., a brake pedal). For example, the operation amount sensor BA is provided with at least one of an operation displacement sensor SP that detects the operation displacement Sp of the brake operating member BP and an operation force sensor FP that detects the operation force Fp of the brake operating member BP. The braking operation amount Ba corresponds to at least one of the operation displacement Sp and the operation force Fp. In other words, the operation amount sensor BA and the braking operation amount Ba are generic terms.

[0085] <<Apply Unit AU>> The apply unit AU is composed of a master reservoir RV, a master cylinder CM, first and second master pistons NM and NS, an input cylinder CN, an input piston NN, an input spring EN, first and second on-off valves VA and VB, a stroke simulator SS, and a simulator pressure sensor PS.

[0086] Brake fluid BF is stored in a master reservoir (also called an "atmospheric pressure reservoir") RV. The master reservoir RV is connected to a master cylinder CM. The master cylinder CM is a tandem type, with first and second master pistons NM and NS forming front and rear master chambers Rmf and Rmr therein. The front and rear master chambers Rmf and Rmr (= Rm) are ultimately connected to the front and rear wheel cylinders CWf and CWr (= CW) via front and rear communication passages HSf and HSR (= HS) and a hydraulic pressure modulator MJ. The hydraulic pressures Pmf and Pmr in the front and rear master chambers Rmf and Rmr are referred to as "front and rear master pressures." The front and rear master pressures Pmf and Pmr are also simply referred to as "master pressure Pm."

[0087] Front and rear wheel master pressure sensors PMf and PMr are provided to detect front and rear wheel master pressures Pmf and Pmr. Since Pmf = Pmr, one of the front and rear wheel master pressure sensors PMf and PMr may be omitted.

[0088] The first master piston NM is provided with a flange. The flange further divides the interior of the master cylinder CM into a servo chamber Ru and a rear chamber Ro. For example, the pressure-receiving area ru of the flange of the first master piston NM (i.e., the pressure-receiving area of the servo chamber Ru, also referred to as the "servo area") and the pressure-receiving area rm of the end of the first master piston NM (i.e., the pressure-receiving area of the master chamber Rm, also referred to as the "master area") are set to be equal. In this case, the hydraulic pressure Pa (adjustment pressure) in the servo chamber Ru and the hydraulic pressure Pm (master pressure) in the master chamber Rm are statically equal, ignoring friction and other factors.

[0089] An input cylinder CN is fixed to the master cylinder CM. An input piston NN is inserted into the input cylinder CN to form an input chamber Rn. The input piston NN is mechanically connected to the brake operating member BP.

[0090] When the input piston NN and the first and second master pistons NM, NS are positioned at their furthest positions in the backward direction Hb (when the volumes of the master chamber Rm and the input chamber Rn are at their maximum), a gap Ks (also referred to as the "separation distance") is formed between the input piston NN and the first master piston NM. The gap Ks creates a state in which the wheel pressure Pw does not change even when a displacement Sp of the brake operating member BP occurs. In other words, the gap Ks enables the brake control device SC to execute regenerative cooperative control. Here, "regenerative cooperative control" refers to the cooperation of the frictional braking force Fw due to the wheel pressure Pw and the regenerative braking force due to the regenerative device (generator).

[0091] The input chamber Rn and the rear chamber Ro are connected via an input path HN. A first on-off valve VA is provided in the input path HN. The input path HN is connected to a master reservoir RV via a reservoir path HR between the rear chamber Ro and the first on-off valve VA. A second on-off valve VB is provided in the reservoir path HR. The first and second on-off valves VA and VB are two-position solenoid valves (also called "on-off valves") that have an open position (communicating state) and a closed position (blocking state). A normally closed solenoid valve is used as the first on-off valve VA. A normally open solenoid valve is used as the second on-off valve VB.

[0092] A stroke simulator (also simply referred to as "simulator") SS is connected to the rear chamber Ro. The simulator SS generates an operating force Fp of the brake operating member BP. In other words, the operating characteristics (relationship between the operating displacement Sp and the operating force Fp) of the brake operating member BP (brake pedal) are formed by the simulator SS. A simulator pressure sensor PS is provided to detect the hydraulic pressure (referred to as "simulator pressure") Ps of the simulator SS. Since the simulator pressure Ps is a state quantity (variable) equivalent to the operating force Fp, the simulator pressure sensor PS corresponds to the brake operation amount sensor BA.

[0093] That is, at least one of the simulator pressure sensor PS, the operation displacement sensor SP (stroke sensor), and the operation force sensor FP is used as the braking operation amount sensor BA. The braking operation amount Ba (detection value of the operation amount sensor BA) corresponds to at least one of the simulator pressure Ps, the operation displacement Sp, and the operation force Fp.

[0094] <Pressure unit KU> The pressurizing unit KU adjusts the hydraulic pressures Pwf and Pwr (front and rear wheel pressures) in the front and rear wheel cylinders CWf and CWr. The pressurizing unit KU is composed of an electric motor MA, a fluid pump QA, a pressure adjusting valve UA, and an adjusting pressure sensor PA.

[0095] The fluid pump QA is driven by an electric motor MA. The suction port Qi of the fluid pump QA is connected to the master reservoir RV via a reservoir line HR. The suction port Qi and discharge port Qo of the fluid pump QA are also connected via a return path HK. Therefore, when the electric motor MA is driven, a circulating flow KN of brake fluid BF is generated in the return path HK by the brake fluid BF discharged by the fluid pump QA (see the dashed arrows in the figure).

[0096] A pressure regulating valve UA is provided in the return path HK. The pressure regulating valve UA controls the hydraulic pressure Pa (regulated pressure) between the discharge port of the fluid pump QA and the pressure regulating valve UA. The pressure regulating valve UA is a linear solenoid valve (also called a "proportional valve" or "differential pressure valve") whose valve opening (lift amount) is continuously controlled based on the energization state (e.g., supply current). A normally open solenoid valve is used as the pressure regulating valve UA. When the supply current Ia to the pressure regulating valve UA increases, the valve opening Li decreases. At this time, the flow of brake fluid BF discharged from the fluid pump QA (circulation flow KN) is throttled by the pressure regulating valve UA, so that the regulated pressure Pa increases from atmospheric pressure.

[0097] The adjustment pressure Pa is supplied to the servo chamber Ru through the servo path HV. The adjustment pressure Pa generates a master pressure Pm via the master pistons NM and NS. The master pressure Pm (=Pmf, Pmr) is supplied to the wheel cylinders CW (=CWf, CWr), generating wheel pressures Pw (=Pwf, Pwr). The wheel pressure Pw generates a braking force Fw on the wheel WH. The pressure sensor PA is provided in the pressurizing unit KU to detect the adjustment pressure Pa.

[0098] <Controller ECU> The apply unit AU and the pressurizing unit KU are controlled by a controller ECU (also referred to as an "electronic control unit"). Specifically, the controller ECU receives inputs of the braking operation amount Ba (at least one of the simulator pressure Ps, operation displacement Sp, and operation force Fp), the adjustment pressure Pa, and the like. Based on these signals, the controller ECU calculates drive signals Va and Vb for the first and second on-off valves VA and VB, a drive signal Ua for the pressure regulating valve UA, and a drive signal Ma for the electric motor MA. The solenoid valves "VA, VB, UA" that constitute the fluid unit HU and the electric motor MA are controlled (driven) in accordance with the drive signals "Va, Vb, Ua, Ma."

[0099] The controller ECU includes a characteristic acquisition device DT. The characteristic acquisition device DT learns the operating characteristics Zip, Ziq of the pressure regulating valve UA based on the method described with reference to FIGS. 1 to 3. Specifically, the controller ECU maintains the current Ia supplied to the pressure regulating valve UA constant, and acquires data (pressure increase and pressure decrease data) Dp, Dq of the regulated pressure Pa relative to the current Ia while the rotation speed Na of the electric motor MA is increased or decreased and then maintained constant. The operating characteristics Zip, Ziq are then determined based on the pressure increase and pressure decrease data Dp, Dq and stored in the characteristic acquisition device DT of the controller ECU. The operating characteristics Zip, Ziq are used to control the drive of the pressure regulating valve UA (a linear solenoid valve).

[0100] The controller ECU calculates a target pressure Pt based on the operation amount Ba (braking operation amount) of the brake operating member BP. The target pressure Pt is a target value corresponding to the adjustment pressure Pa. The target pressure Pt is determined based on a preset calculation map so that the larger the braking operation amount Ba, the larger the target pressure Pt. When the target pressure Pt is increased, the target current It corresponding to the target pressure Pt is determined in accordance with the pressure-increasing characteristic Zip. When the target pressure Pt is decreased, the target current It corresponding to the target pressure Pt is determined in accordance with the pressure-decreasing characteristic Ziq.

[0101] The target current It is a target value of the current Ia (supply current) actually supplied to the pressure regulating valve UA. The controller ECU energizes (supplies power to) the pressure regulating valve UA so that the supply current Ia (detection value of the current sensor IA) matches the target current It. That is, the controller ECU executes current feedback control so that the supply current Ia (actual value) matches the target current It (target value).

[0102] Furthermore, in the controller ECU, the target current It is adjusted so that the adjusted pressure Pa (the detected value of the adjusted pressure sensor PA) matches the target pressure Pt. When "Pa < Pt", the target current It is increased based on the deviation hP between the adjusted pressure Pa and the target pressure Pt so that the adjusted pressure Pa is increased. Conversely, when "Pa > Pt", the target current It is decreased based on the deviation hP so that the adjusted pressure Pa is decreased. That is, in the controller ECU, hydraulic feedback control is executed so that the adjusted pressure Pa (actual value) matches the target pressure Pt (target value) (i.e., the hydraulic pressure deviation hP becomes "0").

[0103] <Second Configuration Example of the Brake Control Device SC Equipped with the Characteristic Acquisition Device DT> Referring to the schematic diagram of FIG. 5, a second configuration example of the vehicle's brake control device SC will be described. In the first configuration example of the brake control device SC, the four wheel pressures Pw are adjusted identically by one pressure regulating valve UA. However, in the second configuration example, the front and rear wheel pressures Pwf, Pwr (and as a result, the front and rear wheel braking forces Fwf, Fwr) can be adjusted individually. Since the hydraulic circuit in the second configuration example of the brake control device SC is known from, for example, Japanese Patent Laid-Open No. 2019-137202, it will be briefly described. Hereinafter, a vehicle equipped with a regeneration device KC (motor / generator) on the front wheel WHf is assumed, and the differences from the first configuration example will be described.

[0104] In the second configuration example, in the reflux path HK, in addition to the first pressure regulating valve UA, a second pressure regulating valve UB is provided. The second pressure regulating valve UB is a normally open linear solenoid valve, similar to the first pressure regulating valve UA. The second pressure regulating valve UB is arranged between the discharge part Qo of the fluid pump QA and the first pressure regulating valve UA. The brake fluid BF discharged by the fluid pump QA is adjusted to the adjusted pressure Pa (also referred to as the "first adjusted pressure") by the first pressure regulating valve UA. Specifically, when the first supply current Ia of the first pressure regulating valve UA is increased, the valve opening amount of the first pressure regulating valve UA is decreased. At this time, since the flow of the brake fluid BF (circulation flow KN) is restricted by the first pressure regulating valve UA, the first adjusted pressure Pa is increased from the atmospheric pressure.

[0105] Furthermore, the second pressure regulating valve UB regulates the pressure between the discharge port Qo and the first pressure regulating valve UA to a regulated pressure Pb (also referred to as the "second regulated pressure"). Specifically, when the second supply current Ib of the second pressure regulating valve UB is increased, the valve opening amount of the second pressure regulating valve UB is decreased. At this time, the flow of brake fluid BF (circulation flow KN) is further throttled by the second pressure regulating valve UB, so that the second regulated pressure Pb is increased from the first regulated pressure Pa. Therefore, the second regulated pressure Pb is equal to or greater than the first regulated pressure Pa (i.e., "Pb≧Pa").

[0106] Additionally, while a tandem-type master cylinder CM is used in the first configuration example, a single-type master cylinder CM is used in the second configuration example. Accordingly, in the second configuration example, the first regulated pressure Pa is supplied to the servo chamber Ru and ultimately output to the front wheel cylinder CWf. Meanwhile, the second regulated pressure Pb is supplied directly to the rear wheel cylinder CWr. The pressurizing unit KU is provided with first and second regulated pressure sensors PA and PB to detect the first and second regulated pressures Pa and Pb. Note that, since the first regulated pressure Pa and the master pressure Pm are substantially equal, the first regulated pressure sensor PA may be omitted if the master pressure sensor PM is provided.

[0107] Furthermore, in the second configuration example, first and second supply currents Ia and Ib (also referred to as "first and second currents") are supplied to the first and second pressure regulating valves UA and UB. In the second configuration example, the controller ECU also includes a characteristic acquisition device DT. The characteristic acquisition device DT separately learns pressure increase and pressure decrease characteristics Zipa and Ziqa (also referred to as "first operating characteristics") of the first pressure regulating valve UA and pressure increase and pressure decrease characteristics Zipb and Ziqb (also referred to as "second operating characteristics") of the second pressure regulating valve UB. That is, in the second configuration example, the first operating characteristics Zipa and Ziqa for the first pressure regulating valve UA and the second operating characteristics Zipb and Ziqb for the second pressure regulating valve UB are determined by separate processes.

[0108] A characteristic acquisition device DT (particularly, a supply unit DU) according to the second configuration example is provided with first and second current sensors IA and IB to detect first and second currents Ia and Ib. A pair of the first current Ia and the first adjustment pressure Pa, which are associated with each other, is stored in a learning unit DG as pressure-increasing and pressure-reducing data Dpa and Dqa (also referred to as "first data") for the first pressure regulating valve UA. Then, first operating characteristics Zipa and Ziqa are determined based on the first pressure-increasing and pressure-reducing data Dpa and Dqa. In a separate learning process, a pair of the second current Ib and the second supply pressure Pb, which are associated with each other, is stored in the learning unit DG as pressure-increasing and pressure-reducing data Dpb and Dqb (also referred to as "second data") for the second pressure regulating valve UB. Then, second operating characteristics Zipb, Ziqb are determined based on the second pressure increase and pressure decrease data Dpb, Dqb.

[0109] First, the determination of the first operating characteristics Zipa, Ziqa during pressure increase and pressure decrease will be described. The first pressure increase and pressure decrease data Dpa, Dqa for the first pressure regulating valve UA are learned while the second pressure regulating valve UB is not energized. Specifically, under the condition of "Ib=0," the first current Ia supplied to the first pressure regulating valve UA is maintained constant, and the rotation speed Na of the electric motor MA is maintained constant after being changed (i.e., increased or decreased), and data Dpa, Dqa (first pressure increase and pressure decrease data) of the first regulating pressure Pa relative to the first current Ia are acquired (learned). Then, based on the first pressure increase and pressure decrease data Dpa, Dqa, the first pressure increase and pressure decrease characteristics (first operating characteristics) Zipa, Ziqa are determined and stored. The first operating characteristics Zipa, Ziqa are used to control the drive of the first pressure regulating valve UA. Specifically, a first target current Ita corresponding to the first current Ia is calculated based on the first operating characteristics Zipa and Ziqa, and the first current Ia (actual value) of the first pressure regulating valve UA is controlled to coincide with the first target current Ita.

[0110] Next, the determination of the second operating characteristics Zipb, Ziqb will be described. The second pressure-increasing / pressure-reducing data Dpb, Dqb for the second pressure regulating valve UB are learned while the first pressure regulating valve UA is not energized. More specifically, under the condition of "Ia=0," the second current Ib supplied to the second pressure regulating valve UB is maintained constant, and data (second pressure-increasing / pressure-reducing data) Dpb, Dqb for the second regulating pressure Pb relative to the second current Ib are acquired while the rotation speed Na of the electric motor MA is maintained constant after being changed (i.e., increased or decreased). Then, based on the second pressure-increasing / pressure-reducing data Dpb, Dqb, the second pressure-increasing / pressure-reducing characteristics (second operating characteristics) Zipb, Ziqb are determined and stored. The second operating characteristics Zipb, Ziqb are used to control the drive of the second pressure regulating valve UB. Specifically, a second target current Itb corresponding to the second current Ib is calculated based on the second operating characteristics Zipb and Ziqb, and the second current Ib (actual value) of the second pressure regulating valve UB is controlled to coincide with the second target current Itb.

[0111] In the process of acquiring the first data Dpa, Dqa relating to the first operating characteristics Zipa, Ziqa (i.e., data for the first pressure regulating valve UA during pressure increase and pressure decrease), the second pressure regulating valve UB is in a fully open state, so "Pa = Pb." Therefore, the first regulating pressure Pa is detected by at least one of the first regulating pressure sensor PA and the second regulating pressure sensor PB. In a configuration in which the first regulating pressure sensor PA is omitted, the detected value Pb (second regulating pressure) of the second regulating pressure sensor PB is used as the first regulating pressure Pa in the first data Dpa, Dqa. Note that even when the second pressure regulating valve UB is in a fully open state, pressure loss may occur in the second pressure regulating valve UB. Because the pressure loss in the second pressure regulating valve UB is known, the first regulating pressure Pa is determined by correcting the detected value Pb of the second regulating pressure sensor PB for the pressure loss.

[0112] <Summary of the embodiment> The following summarizes embodiments of the characteristic acquisition device DT. The characteristic acquisition device DT acquires the operating characteristics Zip and Ziq of a linear solenoid valve UA (pressure regulating valve). Here, the pressure regulating valve UA is a solenoid valve that adjusts the pressure Pa (adjusted pressure) of brake fluid BF (working fluid) discharged by a fluid pump QA driven by an electric motor MA. The characteristic acquisition device DT is composed of a supply unit DU, a regulation unit DM, a detection unit PA, and a learning unit DG. The supply unit DU supplies a current Ia to the solenoid valve UA. The regulation unit DM regulates the rotation speed Na of the electric motor MA. The detection unit PA detects the pressure Pa. The learning unit DG measures and stores data Dp (when pressure is increased) and Dq (when pressure is reduced) of the pressure Pa relative to the current Ia when the motor rotation speed Na is changed (i.e., increased or decreased) and then maintained constant while the current Ia is maintained constant. The learning unit DG determines the operating characteristics Zipp (when increasing pressure) and Ziq (when decreasing pressure) based on the stored data Dp and Dq when increasing pressure and decreasing pressure. The operating characteristics Zip and Ziq when increasing pressure and decreasing pressure are stored in the learning unit DG.

[0113] Specifically, when determining the operating characteristics Zip (operating characteristics during pressure increase) when the pressure Pa is increased, data Dp (data during pressure increase) obtained when the motor rotation speed Na is decreased and then maintained constant is used. Also, when determining the operating characteristics Ziq (operating characteristics during pressure decrease) when the pressure Pa is decreased, data Dp (data during pressure decrease) obtained when the motor rotation speed Na is increased and then maintained constant is used.

[0114] The operating characteristics of the pressure regulating valve UA have hysteresis (history phenomenon). For this reason, even if the supply current Ia is the same, the regulated pressure Pa may not be uniquely determined. The operating characteristics of the pressure regulating valve UA are determined according to the equilibrium state between the suction force Fa of the solenoid SD and the resultant force Fg (the sum of the fluid force Fb and the elastic force Fs). For this reason, even if the supply current Ia is constant, if this state continues for a long period of time, fluctuations in the fluid force Fb will make it unclear whether "the solenoid SD is pushing the fluid force Fb" or "the solenoid SD is being pushed by the fluid force Fb."

[0115] The characteristic acquisition device DT determines pressure increase and pressure decrease characteristics Zip, Ziq based on pressure increase and pressure decrease data Dp, Dq obtained when the rotation speed Na of the electric motor MA is changed and then maintained constant while the supply current Ia is maintained constant. Fluid force Fb changes as the motor rotation speed Na changes. This makes it clear whether "the solenoid SD is pushing the fluid force Fb" or "the solenoid SD is being pushed by the fluid force Fb." As a result, the effects of hysteresis are reliably eliminated when determining the pressure increase and pressure decrease characteristics Zip, Ziq.

[0116] The pressure-increasing characteristic Zip is determined by using data Dp obtained when the supply current Ia is constant and the motor rotation speed Na is reduced and then maintained constant. The reduction in motor rotation speed Na reduces the fluid force Fb, ensuring that the solenoid SD is pushing against the fluid force Fb. This allows the pressure-increasing characteristic Zip to be accurately determined.

[0117] The pressure reduction characteristic Ziq is determined by using data Dq obtained when the supply current Ia is constant and the motor rotation speed Na is increased and then maintained constant. Since the fluid force Fb increases with the increase in the motor rotation speed Na, the solenoid SD is reliably pressed by the fluid force Fb. As a result, the pressure reduction characteristic Ziq is accurately determined.

[0118] The acquisition of the pressure increase and decrease data Dp, Dq and the determination of the pressure increase and decrease characteristics Zip, Ziq based on the data Dp, Dq are performed immediately after the pressure regulating valve UA is installed in the vehicle and the brake fluid BF is vacuum-charged. In other words, when the vehicle is shipped from the vehicle factory, the learning (determination and storage) of the pressure increase and decrease characteristics Zip, Ziq has been completed.

[0119] Only the data Dp relating to the pressure increase characteristic Zip may be measured, and the pressure decrease characteristic Ziq may be estimated based on the pressure increase characteristic Zip. This is based on the fact that the hysteresis of the pressure regulator valve UA is known and relatively stable. Since the pressure decrease characteristic Ziq is estimated, the data Dq relating to it is not measured, which can shorten the time required to learn the pressure increase and pressure decrease characteristics Zip and Ziq.

[0120] The characteristic acquisition device DT is applied to a brake control device SC. In the brake control device SC, a braking force Fw is generated on a wheel WH by the pressure (wheel pressure) Pw of brake fluid BF in a wheel cylinder CW provided on the wheel WH. The brake control device SC is composed of an electric motor MA, a fluid pump QA, a linear solenoid valve UA, and a controller ECU. The electric motor MA drives the fluid pump QA. The solenoid valve UA (pressure regulating valve) controls the brake fluid BF discharged from the fluid pump QA to an adjusted pressure Pa. The adjusted pressure Pa then adjusts the wheel pressure Pw. The controller ECU controls the electric motor MA and the solenoid valve UA.

[0121] The characteristic acquisition device DT is included in the controller ECU of the brake control device SC. The controller ECU acquires data (pressure-increase and pressure-decrease data) Dp, Dq of the regulated pressure Pa relative to the current Ia when the rotation speed Na of the electric motor MA is changed and then maintained constant while the current Ia supplied to the solenoid valve UA is maintained constant. Then, the operation characteristics Zip, Ziq of the solenoid valve UA are determined based on the pressure-increase and pressure-decrease data Dp, Dq. Furthermore, the controller ECU controls the regulated pressure Pa based on the pressure-increase and pressure-decrease operation characteristics Zip, Ziq. Specifically, when the braking operation amount Ba is increased and the regulated pressure Pa (and therefore the wheel pressure Pw) is increased, the regulated pressure Pa is controlled using the pressure-increase operation characteristic Zip. On the other hand, when the braking operation amount Ba is decreased and the regulated pressure Pa (and therefore the wheel pressure Pw) is decreased, the regulated pressure Pa is controlled using the pressure-decrease operation characteristic Ziq.

[0122] The brake control device SC may include two linear solenoid valves UA and UB (first and second pressure regulating valves). In this configuration, first data Dpa and Dqa for pressure increase and pressure decrease operating characteristics Zipa and Ziqa of the first solenoid valve UA (first pressure regulating valve) and second data Dpb and Dqb for pressure increase and pressure decrease operating characteristics Zipb and Ziqb of the second solenoid valve UB (second pressure regulating valve) are learned separately. The first operating characteristics Zipa and Ziqa are learned based on the first pressure increase and pressure decrease data Dpa and Dqa for the first pressure regulating valve UA. The second operating characteristics Zipb and Ziqb are learned based on the second pressure increase and pressure decrease data Dpb and Dqb for the second pressure regulating valve UB.

[0123] According to the above configuration, the brake control device SC learns the operating characteristics (Zip, etc.) of the solenoid valves (UA, etc.) with high accuracy, which improves the accuracy of adjusting the wheel pressure Pw by the solenoid valves. [Explanation of symbols]

[0124] DT...characteristics acquisition means, SC...brake control device, CW...wheel cylinder, ECU...controller (electronic control unit), UA, UB...pressure regulating valve (linear solenoid valve), MA...electric motor, QA...fluid pump, DU...supply unit, DM...adjustment unit, DG...learning unit, PA, PB...regulating pressure sensor (detection unit), Dp, Dq...data (data) during pressure increase and decrease, Zip, Ziq...characteristics (operating characteristics) during pressure increase and decrease, Na...motor rotation speed, Ia, Ib...supply current, Pa, Pb...regulating pressure (pressure), Pw...wheel pressure, Fa...suction force of solenoid SD, Fb...fluid force of brake fluid BF, Fw...braking force.

Claims

1. 1. A characteristic acquisition device for acquiring operating characteristics of a linear electromagnetic valve that adjusts the pressure of brake fluid discharged by a fluid pump driven by an electric motor, comprising: a supply unit that supplies current to the solenoid valve; an adjusting unit that adjusts the rotation speed of the electric motor; a detection unit that detects the pressure; a learning unit that stores data on the pressure relative to the current and determines the operation characteristics based on the data, The learning unit stores the data when the supply unit maintains the current constant and when the adjustment unit maintains the rotation speed constant after changing it.

2. The characteristic acquisition device according to claim 1, The learning unit determines the operating characteristics when the pressure is increased based on the data when the adjusting unit reduces the rotation speed and then maintains it constant.

3. 3. The characteristic acquisition device according to claim 1, The learning unit determines the operating characteristics when the pressure is reduced based on the data when the adjusting unit increases the rotation speed and then maintains it constant.

4. A vehicle brake control device that adjusts wheel pressure, which is the pressure of brake fluid in a wheel cylinder provided in a wheel, a fluid pump driven by an electric motor; a linear solenoid valve that controls the brake fluid discharged by the fluid pump to a regulated pressure and adjusts the wheel pressure based on the regulated pressure; a controller that controls the electric motor and the solenoid valve; The controller maintaining a constant current supplied to the solenoid valve and, when the rotational speed of the electric motor is changed and then maintained constant, acquiring data on the regulated pressure relative to the current, and determining an operating characteristic of the solenoid valve based on the data; A vehicle brake control device that controls the adjustment pressure based on the operating characteristic.

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