JP2009184674A - Method and device for controlling solenoid valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for more precisely controlling a valve of a brake circuit of a vehicle. <P>SOLUTION: In this method for controlling at least one valve of a brake circuit using an electrical control variable (i), a characteristic curve which characterizes the relationship between a pressure drop (Δp) across the valve and the electrical control variable (i) has a region in which a change in the electrical control variable (i) results in a change in the pressure drop (Δp). Also, a starting value for the electrical control variable is selected during actuation of the valve such that the starting value is in this region or at the boundary of this region. Also, the valve controlling device includes starting value selection means for selecting the starting value for the electrical control variable during actuation of the valve such that the starting value is in a valve control region or at the boundary of the valve control region. In the valve control region, a change of the electrical control variable (i) results in a change in the pressure drop (Δp) of the valve. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

Detailed Description of the Invention

  The present invention relates to a method and a control device for controlling a valve of a brake system.

  German Patent Specification No. 19620037A1 describes a method and apparatus for controlling a solenoid valve comprising a coil and a moving contact. In order to move the contact, current and / or voltage is applied to the coil in a clocked manner. With different controls, the solenoid valve can be selectively driven as an on-off valve or as a pressure regulating valve.

  In German Patent Specification No. 195255538A1, anti-lock, which minimizes the pulsation of brake pressure generated by the operation of a suction valve, eliminates noise and vibration, and improves the response sensitivity of the brake pedal A control method and control device for a brake system is described. In the case of this control device and control method, the signal waveform for opening and closing the suction valve has a slope that gradually rises and falls, and suppresses the pulsation of the brake pressure by not completely opening the brake pipe.

  The features of the prior art are based on German patent specification 195255538A1.

German Patent Specification No. 19620037 (A1) German Patent Specification No. 19525538 (A1)

  It is an object of the present invention to provide a method and a control device for more accurately controlling a valve of a brake system in a vehicle.

  According to the present invention, in a method for controlling at least one valve of a brake system by means of an electrical control value, a characteristic curve characterizing the relationship between a pressure drop in the valve and the electrical control value indicates that the change in the electrical control value is a pressure While having at least one region that causes a change in drop, the starting value of the electrical control value is selected to be within said region or at the boundary of said region during control of the valve.

  Thereby, precise control of the valve is possible. In this case, the term pressure drop is understood to be the difference between the pressure on the inlet side of the valve and the pressure on the outlet side of the valve. A feature of the preferred embodiment is that the starting value of the electrical control value during at least one adjustment cycle is selected as a function of the valve variable value or the valve control value in the preceding adjustment cycle.

  This makes it possible to use the main control value detected or generated during one adjustment cycle in the next adjustment cycle. Another advantageous embodiment is characterized by the current flowing through the valve coil such that the control value of the valve in the preceding adjustment cycle exceeds a predetermined value due to wheel brake slip.

  The time point at which the brake slip of the wheel exceeds a predetermined value is detected in advance by a conventional ABS control device (anti-lock brake control system). A feature of the advantageous embodiment is that the starting value of the electrical control value is such that the pressure generation phase is started in the wheel brake cylinder associated with the valve. Thereby, precise control of pressure generation becomes possible. That is, the starting value is a value for starting the pressure generation stage.

  Another advantageous feature is that the electrical control value takes a constant value in the first stage and that the first stage temporally precedes the pressure generation stage. In one advantageous embodiment, the brake pressure in the wheel brake cylinder during the pressure generation phase is increased until the brake slip of the wheel exceeds a predetermined value. Thereby, the slip phenomenon of the car due to the locked wheel is avoided.

  Another preferred embodiment is characterized in that the electrical control value is the current flowing through the valve coil. The value of the current is a value that is easily controlled electrically. According to the invention, in the device for controlling at least one valve of the brake system by means of an electrical control value, the starting value of the electrical control value is within the valve control area during the control of the valve, or Means are provided for selecting to be at the boundary of the valve control region, and within the valve control region, a change in electrical control value results in a change in pressure drop across the valve.

  In an advantageous configuration, the device is used to control a suction valve. In this suction valve, precise and properly calculated valve control is particularly important. A feature of an advantageous embodiment is that at least one valve is a pressure differential regulating valve. As an inherent characteristic of this valve, there is a substantially linear relationship between the coil current and the pressure drop in the valve.

FIG. 1 shows a wheel brake and a suction valve in the form of a hydraulic diagram. FIG. 2 shows the periodic control of the suction valve. FIG. 3 shows the normal type of control of the suction valve. FIG. 4 shows the state of the valve and the response of the wheel when controlling the valve when the control current is too high or too low. FIG. 5 shows the state of the valve and the reaction of the wheel during control according to the present invention. FIG. 6 shows the structure of the device according to the invention and its incorporation into the automotive environment.

  A hydraulic brake system is known, for example, from German Patent Specification No. 19712889 A1 (corresponding to US Pat. No. 6,273,525).

  FIG. 1 shows a cross-sectional view of the hydraulic system. In FIG. 1, block 100 indicates a suction valve, block 102 indicates a wheel brake, and Δp indicates a pressure drop in the suction valve. At that time, the suction valve is controlled via voltage u (t) or current i (t).

  In the present invention, the suction valve is a pressure difference adjusting valve or a linear electromagnetic valve (LMV). This has the characteristic that the coil current in the suction valve is proportional to the pressure drop Δp in the suction valve. At that time, the suction valve has both of the following limit states. That is, when the coil current is small, the valve opens, that is, Δp = 0.

  When the coil current is large, the valve closes and brake fluid or brake medium does not flow. The characteristics of the suction valve for adjusting the pressure are the following two basic characteristics.

  1. The relationship (i-Δp characteristic curve) between the current flowing through the valve and the regulated pressure drop does not change.

  2. Dynamic transient response. This can be explained quite accurately with a first order delay element, the time constant being a function of the connected hydraulic volume.

  A periodic operation of such a valve is shown in FIG. In this figure, time t is shown in the horizontal axis direction, and current i (t) is shown in the vertical axis direction. Here, the current i (t) alternates between a small value and a large value, and correspondingly, the suction valve is in the “open” state with negative results such as noise generation and high mechanical load on the valve. Alternate between the "closed" state.

  The characteristic i-Δp characteristic curve of the suction valve is shown in FIG. In this figure, the current i flowing through the coil of the suction valve is shown along the horizontal axis, and the pressure difference Δp at which the suction valve is adjusted by that value is shown along the vertical axis. If the current is small (0 <i <i1), the valve is open, ie Δp = 0. The current increases almost linearly between i1 and i2. At the current i2, the pressure difference Δp (Δpmax) that can be adjusted to the maximum by the suction valve is reached.

Here, the filling of the brake medium into the wheel brake cylinder and the generation of the brake pressure thereby will be described with reference to FIG.
First, the suction valve is closed, and a pressure of p0 is applied between the supply pipe to the suction valve and the wheel brake cylinder.
-In this case, for example, it is assumed that a current of i> i2 flows.
-Next, increase the pressure in the wheel brake cylinder. This is done by opening the suction valve.
In addition, the current i is gradually reduced with time from the value of i2 over time. Therefore, in FIG. 3, the state moves to the left along the dotted line.
-The pressure drop Δp at the suction valve decreases until the current value such that the dotted line intersects the characteristic curve of the suction valve indicated by the solid line.
Then the state of the suction valve is Δp = 0 along the characteristic curve Move to the point. In doing so, it is not absolutely necessary to reach this point. It clearly means that both current and pressure drop are reduced with time. By returning the current sufficiently slowly, the valve is driven in a static equilibrium state. This means that the valve is always in a static steady state, and the state of the valve moves along the characteristic curve shown in FIG.
The suction valve opens and the pressure in the wheel brake cylinder increases continuously. This opening process can be achieved, for example, by a linearly decreasing current ramp.

  The transition of the valve state along the characteristic curve means that the suction valve operates only in a static steady state during pressure generation in the wheel brake cylinder. This mode of operation is also known in physics under the heading "Adiabatic curve". The release process goes through a series of static states.

  In doing so, it does not matter whether the current is supplied to the valve continuously by current setting or voltage setting, or by pulse / pause driving. However, the pulse / pause drive needs to have a sufficiently high frequency so that the pressure difference adjusting valve cannot follow a high-frequency switching operation, but rather can follow only the average value of the pulse / pause drive. Therefore, the physical characteristic that the coil current does not change abruptly is utilized.

  In addition to the improvement of the open / close state, the present invention also has a supplementary advantage that when the current is known, the pressure difference Δp is also supplementarily determined via the i-Δp characteristic curve. Therefore, this supplementary information Δp can also be used for adjusting ABS (anti-lock brake system) / ESP (electronic stabilization program) / ASR (drive slip control).

  When using the above-described adjustment via the i-Δp characteristic curve, there arises a problem of what current the valve is controlled at the start of pressure generation, in addition to the time of pressure generation. There are two possibilities:

  1. In many travel dynamic characteristic adjustment systems (such as ESP, for example), the intake pressure in the brake system is known via a sensor device in the vehicle. Knowing the intake pressure and the actual brake pressure in the wheel brake cylinder, the pressure drop at the intake valve can be calculated. From there, the required open circuit current can be calculated via the i-Δp characteristic curve.

  2. For many systems (eg, many ABS systems), the intake pressure in the brake system is not known. Auxiliary means provided in such a case by using the pressure difference adjustment characteristic of the suction valve (similarly, the intake pressure is not known) will be described below.

  In the ESP system and ABS system concerned, pressure generation always takes place from the pressure holding stage. That is, the stage with a constant pressure in the wheel brake cylinder always precedes the pressure generation stage (in the wheel brake cylinder). In the pressure holding phase, the current through the valve is not critical as long as it remains to some extent sufficient to shut off the suction valve. In order to start pressure generation immediately, the valve current must be adjusted to correspond to the actual pressure difference. If this current value is wrong, the following two cases occur.

  Case 1: When the current is too small (that is, when the pressure difference that decreases in the suction valve decreases excessively rapidly), pressure generation with an unnecessarily large generation gradient occurs. As a result, the adjustment becomes unstable, the slippage of the wheel also increases, and the steering of the automobile becomes difficult. This situation is shown in the upper diagram of FIG. In this figure, the time t is described in the horizontal axis direction, and the valve current i, the wheel peripheral speed v, and the corresponding pressure p in the wheel brake / cylinder are described in the vertical axis direction. As soon as the current is switched on, a rapid pressure generation occurs, as indicated by point 401. Thereby, the peripheral speed of the wheel correspondingly falls abruptly (402), with the result that the ABS controller responds. The ABS controller dramatically increases the current flowing through the suction valve (404). Thereby, the suction valve is closed. As a result, the pressure in the wheel brake cylinder does not increase any further. Pressure generation (very gradual) in the wheel brake cylinder is effected by opening the corresponding discharge valve.

  Case 2: If the current is too large, pressure generation is delayed until the valve current (and thus the maximum pressure drop that can be shut off) and the pressure drop are in equilibrium. At this point the braking force is too small and the car is not optimally decelerated. This is illustrated in the lower diagram of FIG. 4, whose axes and the curves described are given the same reference numerals as in the upper diagram. The current i is too large (arrow 410), so the pressure drop Δp is kept too long and is not reduced immediately. Therefore, the brake pressure in the wheel brake / cylinder increases only at an extremely late point (see arrow 411).

  A possible alternative control method of the suction valve is shown in FIG. The same reference numerals as those in FIG. 4 are attached to the shafts. In this case, the progress of the control method follows the steps described below.

Step 1 : From the pressure holding stage, the current value decreases in an inclined manner starting from a value that is initially too high. At the time indicated by (1) on the time axis, force equilibrium at the valve is reached, where pressure generation begins. This can be seen by the increase in the pressure p in the wheel brake cylinder, in the lowest curve described.

  It should be emphasized here that in a system without a wheel pressure sensor device, the above time point cannot be detected.

Step 2 : Slowly ensure that the suction valve is always in a static steady state (as described above), although it meets the ABS controller pressure generation requirements (adjusted via the i-Δp characteristic curve). With a slope that only responds, the current is reduced again. This stage takes place between the stated time points (1) and (3) along the time axis.

Step 3 : The current drop increases the pressure in the wheel brake cylinder (as described above) (see increasing p in FIG. 5) and increases wheel instability. This indicates that the peripheral speed of the wheel rapidly decreases as shown in FIG. Thereby, the peripheral speed (v) curve of the wheel is increasingly further away from the curve of the forward speed of the vehicle (which is a straight line indicated by a dotted line), as seen at point 501, for example. The wheel circumferential speed v becomes increasingly lower compared to the vehicle forward speed, which clearly means that the brake slip of the wheel is increased. At time (3), the forward force reaches the maximum point, and the lock pressure p_block acts on the wheel brake cylinder. At the same time, the pressure drop Δp_instab decreases at the suction valve. Although the value of the lock pressure p_block is not known, the following relational expression applies to the pressure drop Δp_instab in the suction valve at the time point (3).

Δp_instab = p_hz− p_block where p_hz is the pressure in the main brake cylinder. A current corresponding to the pressure difference Δp_instab is found, and thereby the pressure difference Δp_instab is found via the i-Δp characteristic curve.

Step 4 : Subsequently, the pressure is reduced because the wheel is unstable. This pressure reduction continues until the observed wheel dynamics indicate that the wheel is again stable, i.e., below the slip threshold. The pressure reduction is done by closing the suction valve and opening the discharge valve (due to the large valve current achieved by the rapid current rise 504 in FIG. 5). Subsequently, a pressure holding phase (suction valve and discharge valve is closed) is performed between time points (3) and (4) until the desired time point for the generation of new pressure is reached. That is time point (4) in FIG. At this point, the wheel is in a stable state again.

Step 5 : In order to generate a new pressure, first the starting value of the current (503 in FIG. 5) must be determined. In determining the starting value, the following is assumed.

  -The friction value of the road and thus the lock pressure was almost constant during the last adjustment cycle.

  -The intake pressure in the last adjustment cycle was almost constant.

  The value obtained by reducing the pressure drop in the suction valve by the numerical value Δp_abbau necessary for wheel stabilization is always substantially constant regardless of the friction value. The numerical value Δp_abbau (as shown in FIG. 5) represents the pressure difference between the time when the suction valve static drive begins and the time when the suction valve static drive ends. In FIG. 5, the numerical value Δp_abbau is related to the current curve i. This becomes apparent when a linear relationship between the current i and the pressure drop Δp at the valve occurs when the suction valve drive is static.

  Thereby, the pressure drop at the suction valve at the start of pressure generation can be calculated by the following equation:

Δp_start = Δp_instab + Δp_abbau
This formula is clearly understood from the following concept. That is,
-Δp_instab is the pressure drop when the valve enters an unstable state, and
-Δp_abbau is a pressure difference to reduce the pressure drop across the valve at the start of the regulation cycle, and to reduce the pressure drop by that pressure difference as a result of the valve opening process.

  Also in this case, the starting value of the current at the time of pressure generation becomes clear from the i-Δp characteristic curve. Thereby, according to the method described, the pressure difference in the valve decreases very quickly at the start of pressure generation in the wheel brake cylinder, so that the pressure difference that decreases in the valve immediately decreases to a very accurate value. It becomes possible to increase the current dramatically.

  The structure of the device according to the invention and its incorporation in the automotive environment is shown in FIG. In this figure, the block 600 includes sensor means for detecting, for example, the pressure p_hz in the main brake cylinder or the wheel rotation speed. Block 602 contains the brake system, in particular the actuating means of the valve to be controlled. The valve controller is included in block 601. Block 601 includes start value selection means 603.

  The output signal of the sensor means 600 is sent to the valve control device 601. The output signal of the valve control device 601 is sent to the starting means 602. For example, when the current flowing through the coil of the valve is detected, feedback from the starting unit 602 to the sensor unit 600 is performed.

DESCRIPTION OF SYMBOLS 100 Suction valve 102 Wheel brake 600 Sensor means 601 Valve control apparatus 602 Start-up means 603 Start value selection means i Electric control value (DELTA) p Pressure difference

Claims (10)

  In the method for controlling at least one valve in the brake system using the electric control value (i), a characteristic curve representing the relationship between the pressure drop (Δp) in the valve and the electric control value (i) is an electric control value (i). ) Has a region that results in a change in pressure drop (Δp), and during control of the valve, the starting value of the electrical control value is such that it is within the region or at the boundary of the region A control method characterized by being selected.   2. The starting value of the electrical control value in at least one adjustment cycle is selected depending on a variable value of the valve or a control value of the valve in a preceding adjustment cycle (Δp_instab). The control method described in 1.   The control value (i) of the valve in the preceding adjustment cycle is a current (i) that causes the brake slip of the wheel to exceed a predetermined value when flowing through the coil of the valve. Control method.   2. Control method according to claim 1, characterized in that the starting value of the electrical control value (i) is a control value such that a pressure generation phase is started in a wheel brake cylinder associated with the valve.   5. The control method according to claim 4, wherein the electric control value takes a constant value in the first stage, and the first stage precedes the pressure generation stage in terms of time.   5. The control method according to claim 4, wherein, in the pressure generation stage, the brake pressure (p) in the wheel brake cylinder is increased until the brake slip of the wheel exceeds a predetermined value.   The control method according to claim 1, wherein the electric control value is a current (i) flowing through a coil of the valve.   In a control device for at least one valve in a brake system by means of an electrical control value (i), the starting value of the electrical control value during control of the valve is within the valve control region or at the boundary of the valve control region And a starting value selecting means for selecting the control, and within the valve control region, a change in the electric control value (i) causes a change in the pressure difference (Δp) that decreases in the valve. apparatus.   9. The control device according to claim 8, wherein the control device is used to control a suction valve.   9. The control device according to claim 8, wherein the at least one valve to be controlled is a pressure difference adjusting valve.

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