KR102600012B1 - Method for regulating the driving force of an electronically controllable motor for driving a pressure generator of a slip-controllable power brake system of an automobile - Google Patents

Abstract

The present invention relates to a method for regulating the driving force (I) of an electronically controllable motor (30) for driving a pressure generator (32) of an electronically slip controllable power brake system (10) of a motor vehicle. Plunger units 32 are used as pressure generators in the power brake system 10 to supply pressurized pressure medium to the wheel brakes 12 of the connected braking circuits A; B. At this time, in some cases, an undesirable increase in pressure may occur. In order to prevent pressure over-rise of the above type, adjustment (step S4) of the driving force I of the motor 30 for driving the pressure generator is carried out in one of the braking circuits A; B of the power brake system 10. According to the invention, it is proposed (step S3: yes) to be carried out in accordance with the control signal of the pressure building valve 42, which controls the pressure medium communication connection between the brake circuit and the wheel brake 12.

Description

Method for regulating the driving force of an electronically controllable motor for driving a pressure generator of a slip-controllable power brake system of an automobile

The invention is based on a method for regulating the driving force of an electronically controllable motor for driving a pressure generator of a slip controllable power brake system of a motor vehicle in accordance with the features of the preamble of claim 1.

Electronically slip-controllable power brake systems for automobiles are known in the prior art. Figure 1 shows the hydraulic layout of such a known power brake system 10 by way of example. This power brake system includes a plunger cylinder 40 in which a plunger piston 38 is movably or displaceably accommodated; A plunger unit composed of a motor for driving the plunger piston 38 is included as the pressure generator 32. This motor is an electric motor 30, and this electric motor is electronically controllable by a control device 28, and the driving force of this electric motor can be set through the current intensity delivered to the electric motor by the electronic control device 28. This motor has an output shaft, the rotational movement of which is converted into a translational movement of the plunger piston 38 by means of a gear device 36 connected downstream.

The advancing plunger piston 38 displaces the pressure medium present in the plunger cylinder 40 into the braking circuits A; B, which are connected to the plunger unit 32, under the build-up of pressure medium pressure. For example, the braking circuits are contacted with two wheel brakes 12 each, which are actuated by a displaced pressure medium. An electronically controllable pressure building valve 42 is connected upstream of each connected wheel brake 12. These pressure building valves 42 block or regulate the pressure medium connection between the wheel brakes 12 and the assigned braking circuits A; B, i.e. partially or completely open, thereby opening the wheel brakes ( By determining the prevailing pressure in 12), this pressure medium connection is controlled. Through this pressure, the braking force generated by the wheel brake 12 is established, which ultimately causes the vehicle to be braked. In this case, the braking force is matched by the electronic control unit 28 to the currently prevailing slip ratio between the wheels of the vehicle assigned to the wheel brakes 12 and the road. Wheels prone to locking are detected by wheel speed sensors 48 which detect the rotational speed of the wheels and transmit this to the electronic control unit 28 for evaluation.

In order to realize a particularly rapid build-up of braking pressure in the wheel brakes 12 and thus the shortest possible braking distances of the vehicle, the electric motor 30 of the plunger unit 32 is essentially controlled by the electronic control unit 28 to be high. It is operated by driving force, and thus a current of relatively high current intensity is supplied. The output shaft rotates correspondingly quickly and advances the plunger piston 38 quickly, and the generated pressure and the amount of pressure medium discharged per unit time are correspondingly large.

However, if the braking pressure in the wheel brake 12 rises strongly enough that there is a risk of locking the assigned wheel, the high dynamics in the power transmission part of the plunger piston 38 can appear as a disadvantage. In this case, the pressure build-up valve 42 blocks the pressure medium communication connection between the relevant wheel brake 12 and the braking circuit A; B, so that no further rise in braking pressure in the wheel brake 12 can occur. It becomes impossible.

The strength of the braking circuits is increased by hydraulically disconnecting one wheel brake or, as the case may be, a plurality of wheel brakes 12 from the braking circuits A; B, which inevitably results in each of the wheel brakes 12 This is because the mechanical elasticity of the brake caliper is no longer provided. Accordingly, the kinetic energy of the plunger movement and the kinetic energy within the drive portion of the plunger unit 32 may exert a load on the pressurized components, thereby negatively affecting the mechanical life of these components in the braking circuits (A; B) Affects the occurrence of undesirable pressure over-rises within

Prevention of pressure peaks or pressure over-rises in the braking circuits A and B can be achieved through a general reduction of the driving force transmitted from the electric motor 30, i.e. through a decrease in the current intensity supplied to the electric motor 30. However, this would have the disadvantage that the pressure build-up dynamics would deteriorate and thus the braking distance of the vehicle would worsen, even if in this case the risk of locking of one of the vehicle's wheels is not at all a concern.

Against this background, the invention provides a method that enables the operation of the power brake system 10 with good pressure build-up dynamics, but prevents the occurrence of undesirable pressure over-rises in selected operating states of this power brake system. It is based on the task proposed.

On the other hand, the method of adjusting the driving force of the electronically controllable electric motor of the plunger unit according to the feature of claim 1 is a power brake system adjusted according to this method when the strength of the braking circuits increases or the strength of the braking circuits increases. The advantage is that it has high pressure build-up dynamics, without pressure over-rises occurring in the braking circuits in case of an impending increase.

According to the invention, regulation of the driving force of the drive motor is carried out in accordance with the control signal of the pressure medium control valve assigned to the wheel brake.

The invention provides the knowledge that it is possible to derive from the control signal of the pressure build-up valve whether the pressure medium communication connection of the brake circuit and the wheel brake is currently open, just now closed by the pressure build-up valve, or is already closed. It is based on Moreover, since control of the pressure build-up valve by the electronic control unit is carried out only when the vehicle wheel assigned to each wheel brake is locked or at least at risk of locking, the strength of the braking circuits can be deduced indirectly from this information. If the strength of the braking circuits increases or is expected to increase, the driving force of the electric motor of the plunger device can be reduced through a limitation of the current intensity delivered to the drive motor by the electronic control device of the power brake system, and thus The emergence of overpressure rises can be prevented in a timely manner.

Information about the risk of a locking tendency of the vehicle wheels is provided from wheel speed sensors in the vehicle brake system. These wheel speed sensors are indispensable for the implementation of electronic slip control and already exist in slip-controlled power brake systems. Therefore, the method on which the invention is based is control-technically implementable within an electronic control unit and does not require additional brake hardware components.

In addition, the method according to the invention protects existing brake hardware components from mechanical overload, thereby extending their life and affecting the reduction of operating noise of the vehicle brake system. Furthermore, the invention allows the use of electric motors that rotate at higher speeds and are more cost-effective, having a shorter overall length than the drive motor for the pressure generator.

Further advantages or advantageous developments of the invention appear from the dependent claims or the description below.

Preferably, matching the driving force to the control signal of the pressure building valves is carried out only if the pressure prevailing in the braking circuit or braking circuits is greater than a threshold of 50 bar, below which the braking circuits This is because pressure over-rises that may occur due to increased strength of the circuits do not have a detrimental effect on the brake hardware components, and therefore the high pressure build-up dynamics within this pressure range take precedence.

The driving force of the drive motor is preferably reduced step by step from the maximum value to the minimum value, each step depending on the current strength of the braking circuits. The maximum value of the driving force is transmitted at the minimum strength of the braking circuits, and the minimum value is transmitted at the maximum strength of the braking circuits. The strength of the braking circuits is minimum when all connected wheel brakes are connected to the braking circuits in pressure medium communication, whereas the maximum strength of the braking circuits exists when none of the connected wheel brakes are anymore connected to the braking circuits in pressure medium communication. do. The minimum value of the driving force means that the current intensity supplied to the drive motor is sufficient to compensate for pressure medium leakage or associated pressure drops that may occur in the braking circuits. Of course, since the leakage of the pressure medium is extremely small, in some cases, the current supply to the drive motor and, accordingly, the driving force of the drive motor may be zero.

The method according to the invention is explained in detail in the description below with reference to the illustrations of FIGS. 1 and 2 .
1 is a diagram showing the hydraulic layout of an automobile power brake system capable of electronic slip control.
Figure 2 is a flow chart showing the method according to the present invention.

The power brake system 10 shown in FIG. 1 provides for electronic regulation of the slip ratio on automobile wheels equipped with wheel brakes 12 . In particular, this power brake system includes a master brake cylinder (16) operable by the driver and supplied with hydraulic pressure medium through a pressure medium reservoir (14), and this master brake cylinder (16) in pressure medium communication. It comprises two separate braking circuits (A, B) that are in contact. By actuating the actuating element 18 of the master brake cylinder 16, the driver displaces the brake piston inside the master brake cylinder 16 against the restoring force of the piston spring, in this case the brake of one of the brake pistons. The braking demand is predetermined by displacing the pressure medium from one or more pressure medium chambers bounded by the piston. Under normal conditions, i.e. in the normal state of the power brake system, the pressure medium displacing from the master brake cylinder 16 reaches the cylinder/piston arrangement called pedal path simulator 20, and is sealed by the simulator piston. buffered within the chamber. The inflow and outflow of pressure medium into the pedal path simulator 20 is controllable via an electronically controllable simulator control valve 22 disposed in the line connection between the master brake cylinder 16 and the pedal path simulator 20. . This simulator control valve is a directional control valve with two hydraulic connections that can be switched from the normally closed default position to the passing position via electronic control. The pressure medium flowing into the pedal path simulator 20 enables the actuating path of the actuating element 18 of the master brake cylinder 16 .

When the master brake cylinder 16 operates, braking is performed in an error-free normal operating state of the power brake system 10 so that no braking pressure is formed in the braking circuits A and B connected to the master brake cylinder 16. Circuit disconnecting valves 24 are provided to disconnect the pressure medium of the circuits A; B and the master brake cylinder 16. These circuit disconnect valves 24 also have two hydraulic connections, but, unlike the simulator control valve 22, they are each switchable from the default normally passed position to the blocked position.

The operating path of the actuating element 18 of the master brake cylinder 16 is detected by one or more path sensors 26 and transmitted to the electronic control unit 28 of the power brake system 10. From this path signal, this electronic control device 28 generates a plunger unit 32 which is connected to the braking circuits A; B in parallel to the master brake cylinder 16 and downstream of the circuit disconnect valves 24. A control signal for the electric motor 30 to drive is detected. The hydraulic connection of the braking circuits (A; B) with the plunger unit (32) is adjustable via plunger control valves (34). These plunger control valves 34 are normally closed, like the simulator control valve 22, and are respectively switched to the passing position through electronic control. These plunger control valves also include two pressure medium connections.

A gear device 36 exists between the electric motor 30 and the plunger unit 32. This gear device converts the rotational movement of the electric motor 30 into axial movement of the plunger piston 38. Driven in this way, the plunger piston 38 moves forward (towards the left in Figure 1) within the plunger cylinder 40 and forces the pressure medium stored within the plunger cylinder 40 into the open plunger control valves 34. It is displaced into the braking circuits (A; B). In this case, a build-up of braking pressure occurs in the braking circuits A; B, the height of which is correlated with the operating path of the operating element 18 of the master brake cylinder 16.

In order to match the braking pressure to the current slip rate on the wheels of the vehicle, each of the wheels is assigned a pressure modulation device consisting of a pressure build-up valve 42 and a pressure drop valve 44 respectively. The pressure building valve 42 is a normally open proportional valve that controls the inflow of pressure medium into the wheel brakes 12 of the wheel and, thus, the braking pressure build-up in these wheel brakes 12, while the pressure reducing valve 44 ) is designed as a normally closed diverter valve, controlling the outflow of the pressure medium from the wheel brake 12 back into the braking circuits A; B. The pressure medium flowing out from the wheel brakes 12 flows back into the pressure medium reservoir 14 of the master brake cylinder 16 through the common return 46.

The plunger cylinder 40 is connected to the return part 46 via a line connection 41 controlled by a check valve, thereby connecting the pressure medium reservoir 14 in pressure medium communication. When the plunger piston 38 moves into the plunger cylinder 40 by the corresponding control of its driving part, i.e. towards the right in Fig. 2, the volume of the plunger cylinder 40 is enlarged, and the pressure medium moves along these lines. It flows back from the pressure medium reservoir 14 through the connection 41 into the plunger cylinder 40 .

The power brake system according to Figure 1 is shown in the operational state and in the basic position without current supply (stationary state), i.e. when starting a vehicle equipped with it, the above-mentioned valves assume their respective switching positions. In this switching position, the simulator control valve 22, plunger control valves 34 and pressure reduction valve 44 are open, while the circuit isolating valves 24 and pressure building valves 42 are closed.

Now, when the driver initiates the braking process through actuation of the actuating element 18 of the master brake cylinder 16, the pressure medium flows into the pedal path simulator 20 from the master brake cylinder 16 and the actuating element 18 ) executes the operating path detected by the path sensor 26. This is passed to the electronic control unit 28, where it is converted into a control signal for the electric motor 30 of the plunger unit 32. The plunger piston 38 driven in this way displaces the pressure medium into the braking circuit A; B, which reaches the wheel brakes 12 via the now open pressure building valves 42 . Since the pressure reducing valves 44 are closed at the same time as the pressure building valves 42 are opened, there is in the wheel brakes 12 the actuating element 18 of the master brake cylinder 16, which brakes the assigned wheel. A braking pressure is created that is correlated to the operating path.

In this case, the prevailing slip ratio between the wheel and the road determines the braking force that can be transmitted from the wheel brake 12 and, therefore, the braking pressure that can still be transmitted. If there is a risk of wheel locking at low slip rates or high braking pressures, the pressure build-up valves 42 are closed and the pressure drop is reduced in order to reduce the braking pressure prevailing in the wheel brake 12 to a level where the relevant wheel is still rolling. Valves 44 are open. The locked state of the wheels is detected by the wheel speed sensors 48 and transmitted to the electronic control unit 28 for corresponding matching of the control of the pressure build-up valve 42 or the pressure drop valve 44.

By closing the pressure building valves 42 , the mechanical elasticity of the associated braking circuits A and B is inevitably reduced, since the component elasticity of the separated wheel brake 12 is no longer provided. Due to this, the kinetic energy present in the driving part of the plunger unit 32 creates pressure peaks or over-rises in the associated braking circuits A; B, which may have undesirable reactions on the pressure-loaded components. can cause In order to prevent further pressure build-up in the assigned wheel brake 12, this control device 28 generates a control signal to switch these hitherto open pressure build-up valves 42 to the closed position, As soon as it is transferred to one of the pressure building valves 42, i.e. as soon as one of the pressure building valves 42 is electronically controlled during the braking process, the driving force of the plunger unit 32 is transferred to the electronic control device 28. ), reactions of the above type are prevented according to the invention. Up to this point, the plunger unit 32 operates with a driving force that provides a high pressure medium flow and at the same time under a high braking pressure. The set vehicle deceleration is correspondingly large and the braking distance of the vehicle is correspondingly short.

The method already described above is illustrated once again in FIG. 2. After the start of the method S, in a first method step S1 the braking pressure generated in the braking circuits A; B by the plunger unit 32 is measured by the circuit pressure sensors 50, The results are supplied to the electronic control unit 28 of the power brake system 10. Then, in step "S2", the control device 28 checks whether the generated braking pressure is higher or lower than an application-specific storable limit value 52 in the electronic control device 28. This limit 52 is such that even when the wheel brakes 12 are disengaged, the kinetic energy of the plunger drive is such that the pressure can cause mechanical damage to the pressurized components of the braking circuits A; B. Indicates the threshold beyond which excessive rise will not occur.

If the threshold 52 is not met, the method is terminated and repeated at a later time (path 54).

On the other hand, if the limit value is exceeded (path 56), as soon as the risk of locking the wheels of the braking circuit (A; B) is detected by the corresponding signals of the wheel speed sensors 48, or according to step "S3" As soon as the query yields the result that a control signal has been generated and transmitted by the electronic control device 28 to one of the pressure building valves 42 of the vehicle braking system 10, the braking circuits A ; The elasticity of B) decreases, and accordingly, when the electronic control device 28 reduces the driving force of the electric motor 30 of the plunger unit 32, there is a risk of a detrimental excess pressure rise.

If the braking circuit (A, B) includes a plurality of wheel brakes (12) connected to the braking circuit, the driving force of the plunger unit (32) is adjusted by the electronic control device (28) as indicated in step “S4”. It can be reduced step by step, i.e. a first stage when the connected first wheel brake 12 is disconnected from the braking circuit A; B through control of the assigned pressure building valve 42; in one or more second or final stages when all wheel brakes 12 connected to the braking circuit A; B are disconnected via control of the pressure building valves 42 by the electronic control device 28; can be reduced.

By reducing the control signal to the pressure build-up valves 42, one or more pressure build-up valves 42 are opened again (interrogation according to step “S5”), whereby the wheel brakes 12 are again connected to the respective braking circuits ( By being hydraulically connected to A; B), as soon as the elasticity of the braking circuits A; B rises again, the driving force of the electric motor 30 of the plunger unit 32 is again shifted to the maximum output direction by the electronic control device 28. It can rise. The rise of this driving force is again step by step according to step "S6", depending on the number of wheel brakes 12 coupled to the braking circuit (A; B), and finally again the initial maximum pressure build-up dynamics are provided and the method This can run until terminated at "E". The control signal to the pressure building valves 42 is continuously monitored, in step "S5", according to the shown path "58", when the control signal is reduced by the electronic control unit 28 and a reaction takes place, i.e. braking. The pressure building valves 42 of the circuits A; B are no longer controlled and are thus returned to the default position, and the pressure medium connection between the wheel brakes 12 and the braking circuits A; B. forms.

Of course, changes or additions to the present invention beyond what is disclosed in this patent application are conceivable without departing from the basic concept of the present invention.

Claims (8)

A method for controlling the driving force of an electronically controllable motor (30) for driving the pressure generator (32) of a slip controllable power brake system of an automobile,
The power brake system comprises at least one braking circuit with at least one wheel brake (12) capable of being supplied with a pressure medium,
Upstream of the wheel brake 12, an electronically controllable pressure building valve 42 is connected, which controls the connection of the pressure medium of the braking circuit A; B with the wheel brake 12 in accordance with a control signal from the electronic control unit 28. In a method for controlling the driving force of an electronically controllable motor,
Regulation of the driving force of the motor 30 is carried out in accordance with a control signal to the pressure building valve 42,
The driving force of the motor 30 is reduced through two or more stages from the maximum value to the minimum value, and at the maximum value of the driving force, all wheel brakes 12 are connected to one of the braking circuits A and B. The driving force of the electronically controllable motor, characterized in that the pressure medium connection is opened and at the minimum value of the driving force all wheel brakes 12 are disconnected from the pressure medium connection with the braking circuit of one of the braking circuits A; B. How to control . According to paragraph 1,
In case of imminent interruption of the pressure medium connection between the braking circuit A; B and the wheel brake 12 assigned to the braking circuit A; B, by means of a control signal to the pressure building valve 42, the motor 30 A method for regulating the driving force of an electronically controllable motor, characterized in that the driving force is reduced. According to claim 1 or 2,
Characterized in that when the pressure medium connection between the braking circuit (A; B) and the assigned wheel brake (12) is blocked by the control signal of the pressure forming valve (42), the driving force of the motor (30) is reduced. A method for regulating the driving force of an electronically controllable motor. According to claim 1 or 2,
Electronic control, characterized in that when all wheel brakes (12) of the braking circuit (A; B) are disconnected from the pressure medium with the braking circuit (A; B), the driving force of the motor (30) is reduced to a minimum value. A method to adjust the driving force of the motor as much as possible. According to claim 1 or 2,
A method for adjusting the driving force of an electronically controllable motor, characterized in that control of the driving force of the motor (30) is carried out through the current intensity, and the rotation speed of the output shaft of the motor (30) is determined through the current intensity. According to claim 1 or 2,
The method for regulating the driving force of the electronically controllable motor is characterized in that it is carried out only when the pressure in the braking circuit (A; B) is higher than a limit value settable in the electronic control device (28). A method to adjust the driving force of the motor as much as possible. delete According to claim 1 or 2,
Control of the driving force of the motor 30 is carried out by an electronic control device 28 that also controls the application of braking pressure to the wheel brakes 12 of the power brake system. How to do it.

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