Method for controlling an electronically slip-controllable non-manual brake device with redundant brake pressure generation

Abstract

Due to operation, in this type of non-human brake system (10), a shift of the pressure-volume characteristic curve in the direction of higher pressures can occur. If the actual curve of the pressure-volume characteristic curve deviates from the setpoint curve to an extent that is no longer permissible, a correction is necessary. For this purpose, pressure medium volume must be discharged from the brake circuits (18a, 18b) into the reservoir (32) of the non-human brake system (10). The invention proposes a method by which the discharge of pressure medium into the reservoir (32) can be managed and carried out. The method can be carried out during the braking process without undesirable noise or unexpected deceleration changes occurring, which can be realized using control technology and thus particularly cost-effectively.

Description

Technical Field

[0001] The present invention relates to a method for controlling an electronically slip-controllable non-manual braking device with redundant brake pressure generation according to the features of the preamble of claim 1.

[0002] Vehicle braking devices basically need to be distinguished between well-known manual braking devices and new non-manual braking devices compared to manual braking devices. In the case of manual braking devices, the driver is at least involved in increasing the brake pressure via muscle power, whereas in the case of non-manual braking devices, the existing brake request is converted into brake pressure by an electrically driven brake pressure generator.

[0003] In connection with the development of highly automated or fully automated motor vehicles, non-manual braking devices have redundant brake pressure generation. Thereby, such vehicles can be automatically braked to a stop even if there is a fault in one of the plurality of pressure medium pumping devices.

[0004] For safety-technical reasons, non-manual braking devices may additionally have a hydraulic fallback level for the brake pressure supply of the non-manual braking device. The hydraulic fallback level enables normal brake pressure increase via the muscle power of the driver even if the voltage supply and / or the electronic system fails.

Background Art

[0005] FIG. 1 shows a hydraulic layout known in the prior art of an electronically slip-controllable non-manual braking device with redundant brake pressure generation, as underlying the subsequent present invention.

[0006] This known non-manual braking device (10) particularly has a brake request detection device, and the driver can set a brake request via the brake request detection device. The brake request detection device is a master brake cylinder (14) operable via a pedal (12), and the master brake cylinder (14) exemplarily has two pressure chambers (16a, 16b). The pressure chambers (16a, 16b) are each connected to one brake circuit (18a, 18b). Via the master brake cylinder (14), when the voltage supply or the electronic system of the non-manual braking device (10) fails, it is possible to increase the brake pressure via muscle power.

[0007] One of the pressure chambers (16a) is further connected to a pedal feel simulator (20), and the pedal feel simulator (20) provides haptic feedback to the driver when the pedal (12) is operated.

[0008] The non-manual braking device (10) further has a brake pressure generator (22), and the brake pressure generator (22) has a first pressure medium pumping device (24) that forms a brake pressure correlated with the set brake request. There is further a brake pressure modulator (26), and the brake pressure modulator (26) has a second pressure medium pumping device (28) for individually adjusting the brake pressure of each wheel.

[0009] The pressure medium pumping devices (24, 28) are arranged in hydraulic units (30a, 30b) together with the assigned direction control valves. In the illustrated embodiment variant, the hydraulic units (30a, 30b) are physically separated from each other but are hydraulically linked to each other.

[0010] Therefore, the pressure medium for hydraulics is supplied to both the brake pressure generator (22) and the brake pressure modulator (26) via a single common reservoir (32) arranged in the master brake cylinder (14) of the non - human - power brake device (10). The brake pressure generator (22) and the brake pressure modulator (26) are connected to both brake circuits (18a, 18b) in parallel with each other. A plurality of wheel brakes (34a - d) are respectively associated with these brake circuits (18a, 18b).

[0011] To control the pressure medium connection between components of the non - human - power brake device (10), there are a number of direction - control valves. A simulator valve (36) that can be driven and controlled electrically is provided to control the connection of the master brake cylinder (14) to the pedal feel simulator (20). The simulator valve (36) is driven and controlled electrically under normal operating conditions of the non - human - power brake device (10) and occupies an open position or a passing position.

[0012] Furthermore, there are circuit - cut - off valves (38a, 38b), and the circuit - cut - off valves (38a, 38b) control the connection between one pressure chamber (16a, 16b) of the master brake cylinder (14) and the assigned brake circuit (18a, 18b) respectively. These circuit - cut - off valves (38a, 38b) are normally open and cut off this connection in a state of being driven and controlled electrically, that is, in the normal state of the non - human - power brake device (10).

[0013] A plunger discharge valve (40) is provided, and the plunger discharge valve (40) controllably connects the first pressure - medium pumping device (24) to the reservoir (32) of the non - human - power brake device (10). This plunger discharge valve (40) is closed in the basic position and opens the corresponding pressure - medium connection in a state of being driven and controlled electrically.

[0014] Furthermore, plunger cut-off valves (42a, 42b) are provided, and the plunger cut-off valves (42a, 42b) are used to control the connection of the pressure medium from the first pressure medium pumping device (24) to each one of the brake circuits (18a, 18b). The plunger cut-off valves (42a, 42b) are open in a state of being driven and controlled electrically.

[0015] For each of the brake circuits (18a, 18b), furthermore, one so-called circuit pressure regulating valve (44a, 44b) is provided respectively. As the name implies, the pressure within the brake circuits (18a, 18b) can be adjusted by these valves. This valve is a normally open valve that can be operated in the closing direction by electric drive control.

[0016] In parallel with the circuit pressure regulating valves (44a, 44b), high-pressure switching valves (46a, 46b) are arranged. The high-pressure switching valves (46a, 46b) are used to control the supply of the pressure medium from the reservoir (32) to the second pressure medium pumping device (28). The high-pressure switching valves (46a, 46b) are normally closed.

[0017] For the adjustment of the brake pressure for each individual wheel, each wheel brake (34a to d) is additionally assigned one drive-controllable pressure increasing valve (48a to d) and one also drive-controllable pressure reducing valve (50a to d). The pressure increasing valves (48a to d) are configured to be normally open, whereas, in contrast, the pressure reducing valves (50a to d) are normally closed valves.

[0018] These valves mentioned above are formed as switching valves or as regulating valves. The switching valve occupies one or the other valve position, while the regulating valve can also be shifted to an intermediate position in order to throttle the flow of the pressure medium when necessary. The adjustability of the directional control valve is recognizable in the representation using the symbol of the directional control valve in FIG. 1 by a valve actuator with a diagonal arrow. The circuit pressure regulating valves (44a, 44b) and the pressure boosting valves (48a - d) are formed as regulating valves, and the remaining valves are switching valves.

[0019] Finally, the non - actuated brake device (10) shown in FIG. 1 further has electronic control devices (52a, 52b), and the electronic control devices (52a, 52b) are assigned to the brake pressure generator (22) or the brake pressure modulator (26). The electronic control devices (52a, 52b) drive - control the respective pressure medium pumping devices and / or the valves described as required, and for this purpose capture the signals of a plurality of sensors. The sensors detect the driving state of the vehicle, the current traffic situation and / or the measured quantities within the non - actuated brake device (10). Exemplarily mentioned in this context is the stroke measurement sensor system (64) of the non - actuated brake device (10) that detects the operating stroke of the pedal (12), and further the pressure sensors (61a, 61b) that detect the pressure generated by the master brake cylinder (14) or the first pressure medium pumping device (24).

[0020] Both control devices (52a, 52b) communicate electronically with each other. Both control devices (52a, 52b) may be combined into one electronic control unit.

[0021] The first pressure medium pumping device (24) of the brake pressure generator (22) is a plunger piston (54) or a push-out body, and the plunger piston (54) or the push-out body is movably accommodated in the plunger cylinder (56) and is guided axially in the plunger cylinder (56). The plunger piston (54) can be displaced in the pressure increasing direction or in the pressure decreasing direction opposite to the pressure increasing direction in the plunger cylinder (56) by an electric drive unit (58). Alternatively, it would also be possible to move the plunger cylinder (56) relative to the plunger piston (54).

[0022] The movement of the push-out body ends each time at a so-called outer turning point in the pressure increasing direction and at a so-called inner turning point in the pressure decreasing direction. With the movement of the plunger piston, the volume of the working chamber (60) surrounded by the plunger piston (54) and the plunger cylinder (56) changes. The volume of the working chamber (60) decreases when the plunger piston (54) moves in the pressure increasing direction and increases when the plunger piston (54) moves in the pressure decreasing direction, conversely.

[0023] The pressure-volume characteristic curve of the non-manual brake device (10) shows the pressure change in the connected brake circuits (18a, 18b) corresponding to the volume of the pressure medium pushed by this first pressure medium pumping device (24). This characteristic curve is almost structurally determined by the structural design of the brake circuits (18a, 18b) and the dimensions of the plunger piston (54) or the plunger cylinder (56) of the first pressure medium pumping device (24) and is stored digitally in the electronic control device (52).

[0024] The second pressure medium pumping device (28) is, in contrast, a pump that pumps the pressure medium continuously or periodically. For example, it could be a piston pump or a gear pump, and the piston pump or the gear pump is also driven by an electric motor (62) that can be driven and controlled.

[0025] Under the operating conditions of this non-manual braking device (10), for example, there may be a situation where the existing braking request requires a setting of the braking pressure that is higher than the maximum pressure p(max) that can be provided by the braking pressure generator alone. This maximum pressure is determined by the output of the drive unit (58) of the displacing body and the volume of the working chamber (60). When the braking request is higher than the maximum pressure that can be set by the first pressure medium pumping device (24), the second pressure medium pumping device (28) of the braking pressure modulator (26) is used to increase the existing braking pressure. In response to the corresponding request signal from the control device (52a) of the braking pressure generator (22) to the control device (52b) of the braking pressure modulator (26), the second pressure medium pumping device (28) is thus operated or driven for this purpose.

[0026] However, this volume of the pressure medium additionally displaced into the braking circuit (18a, 18b) by the second pressure medium pumping device (28) causes a shift of the described pressure-volume characteristic curve in the direction of higher pressure. Therefore, the actual progression of the pressure-volume characteristic curve deviates from the structurally predefined target progression.

[0027] At the time of reducing the brake pressure, which is carried out at the end of the braking process, the volume of the pressure medium displaced additionally into the brake circuits (18a, 18b) cannot, moreover, be completely removed again from the brake circuits (18a, 18b) by means of the first pressure medium pumping device (24) of the brake pressure generator (22). This is because, upon reaching the turning point inside the plunger piston (54) of the first pressure medium pumping device (24), the maximum receiving volume of the working chamber (60) has been exhausted. Therefore, a residual pressure remains in the brake circuits (18a, 18b), and this residual pressure can be dissipated towards the reservoir (32) without being controlled via the plunger discharge valve (40). This is because this plunger discharge valve (40) is formed as a switching valve, and accordingly, it only tolerates successive brake pressure reductions at most. Alternatively, a bleed-off line may be provided, which connects the working chamber (60) of the plunger cylinder (56) to the reservoir (32) and is opened by the plunger piston (54) as soon as the plunger piston (54) reaches or exceeds its inner turning point. Nevertheless, in this case too, the brake pressure reduction will be carried out abruptly, causing a drop that is hardly comfortable for vehicle deceleration and an undesirable operating noise.

Summary of the Invention

Advantages of the Invention

[0028] The present invention therefore proposes a method by which it is possible to manage and carry out the dissipation of this residual pressure in the brake circuits (18a, 18b) using existing components. In so doing, potential operating noise is avoided without the need for additional components for controlling the pressure medium or without the need for modifications to existing components. The proposed method is implemented using control technology and can thus be carried out particularly inexpensively.

[0029] Further advantages or advantageous developments of the present invention can be seen from the dependent claims or the following description.

[0030] The present invention is shown in the drawings and will be described in detail in the following description.

[0031] The drawings include a total of four figures.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0033] The non-manpower braking device (10) shown in Figure 1 is at the root of the method according to the present invention described below. Regarding the structure and function of the non-manpower braking device (10), it has already been described in the introduction part of the specification. For the understanding of the present invention, starting from the following initial state of the components of this non-manpower braking device (10): The non-manual braking device (10) is in the active mode. That is, the voltage supply unit is sound and there are no mechanical malfunctions in the components. The direction control valve accordingly occupies the position shown in FIG. 1. Accordingly, the simulator valve (36), i.e., the valve provided in the pressure medium connection from one of the pressure chambers (16a, 16b) of the main brake cylinder (14) to the pedal feel simulator (20), is open. The circuit cut-off valves (38a, 38b) that control the pressure medium connection of the pressure medium chambers (18a, 18b) of the main brake cylinder (14) to the brake circuit (18a, 18b) are in the cut-off position. The driver is thus disconnected from the brake pressure generation in the wheel brakes (34a - d) and only sets a brake request by operating the pedal (12). The confirmation of the brake request is carried out by the stroke measurement sensor system (64), which detects the stroke traveled by the pedal (12), converts it into an electronic signal, and transmits it to the electronic control unit (52a).

[0034] The plunger discharge valve (40) is closed, and thus the pressure medium connection of the first pressure medium pumping device (24) to the reservoir (32) is blocked, while the plunger cut-off valves (42a, 42b) are open and the circuit pressure regulating valves (44a, 44b) are closed. Brake pressure is applied to at least one of the wheel brakes (34a - 34d).

[0035] To form this brake pressure corresponding to the set brake request, the plunger piston (54) of the brake pressure generator (22) is operated by its drive unit (58) in the pressure increasing direction and is therefore at its outer turning point within the plunger cylinder (56). Accordingly, the working chamber (60) has a minimum volume.

[0036] Furthermore, the second brake pressure pumping device (28) of the brake pressure modulator (26) sucks additional volume from the reservoir (32) and pumps it into at least one brake circuit (18a, 18b) in order to increase the brake pressure. This is implemented via the pressure medium connection that starts from the reservoir (32) and leads to the suction side of this second pressure medium pumping device (28) via a check valve (66) arranged downstream of this reservoir and an electrically driven and thus opened high-pressure switching valve (46a, 46b).

[0037] The pressure increasing valves (48a - d) assigned to the wheel brakes (34a - d) are open, and the pressure reducing valves (50a - d) are closed.

[0038] The additional pumping of the pressure medium by the second pressure medium pumping device (28) is carried out, for example, during the braking process because it is necessary to adapt the brake pressure in the wheel brakes (32a - d) to the slip ratio of one or more wheels of the vehicle and / or because, although the brake pressure generator (22) has displaced the maximum possible volume of the pressure medium by the brake pressure generator (22), the brake pressure corresponding to the brake request has still not been set. This situation, as necessarily described above, involves shifting the pressure - volume - characteristic curve of the non - actuated brake device (10), which is structurally determined in itself, in the direction of higher pressure. By the method described below, this characteristic curve shift is managed and reversed.

[0039] The method for controlling the non - actuated brake device (10) with redundant pressure supply, which is at the basis of the present invention, is graphically shown in FIG. 2 for this purpose. This FIG. 2 includes a total of four graphs 2a - 2d arranged one above the other for this purpose, and the graphs 2a - 2d show the transitions of the parameters related to the method in time synchronization with each other respectively.

[0040] The uppermost graph 2a in FIG. 2 shows the pressure transition for this purpose. This graph 2a shows a total of two characteristic lines. Among these characteristic lines, the first pressure characteristic line (68a) shows the temporal transition of the pressure in the working chamber (60) of the first pressure medium pumping device (24), that is, in the brake pressure generator (22), while the second pressure characteristic line (68b) shows the transition of the brake pressure in one of the plurality of wheel brakes (34a - d), and thus, in turn, represents the set brake request.

[0041] The second graph 2b from the top describes the transition of the volume of the pressure medium displaced by each pressure medium pumping device (24, 28) over time. The first volume characteristic line (70a) shows the volume displaced by the first pressure medium pumping device (24), that is, the brake pressure generator (22), and the second volume characteristic line (70b) reproduces the volume of the pressure medium displaced by the second pressure medium pumping device (28), that is, the brake pressure modulator (26). Additionally, the graph 2b shows, with the signal characteristic line (72), the electrical drive control of the plunger discharge valve (40) provided in the pressure medium connection of the first pressure medium pumping device (24) to the reservoir (32). Since the plunger discharge valve (40) is a normally - closed switching valve here, this signal characteristic line (72) indicates when the plunger discharge valve (40) is electrically driven and thus when it is open.

[0042] The graph in Fig. 2c shows, with the differential pressure characteristic line (74), the temporal change in the differential pressure applied to the circuit pressure regulating valves (44a, 44b) of the brake circuit (18a, 18b). This differential pressure corresponds to the pressure difference between the pressure on the pressure medium in - side of this circuit pressure regulating valve (44a, 44b) and the pressure on the pressure medium out - side. The pressure medium in - side is on the wheel brake (34a - d) side based on the flow direction of the pressure medium, while the pressure medium out - side is on the side of the first pressure medium pumping device (24). When the displayed differential pressure is high, the circuit pressure regulating valves (44a, 44b) have a relatively small throttle cross - section or no throttle cross - section at all. And when the differential pressure is zero, the circuit pressure regulating valves (44a, 44b) are in the passing position.

[0043] In the bottom - most graph shown in Fig. 2d, finally, with the rotational speed characteristic line (76), the rotational speed of the motor (62) of the second pressure medium pumping device (28) is described over time.

[0044] The time axis in the graphs of Fig. 2 is divided into six time phases respectively, and these time phases are numbered sequentially as t1 - t6.

[0045] As can be seen from the graph shown in Fig. 2a, in the first time phase t1, pressure increase is carried out within at least one of the wheel brakes (34a - d) of the brake circuit (18a, 18b). This pressure increase is carried out constantly and uniformly, that is, along a straight - line ramp with an upward slope from the lower left to the upper right.

[0046] According to the graph shown in Fig. 2b, for this purpose, the pressure medium volume is pumped to the wheel brakes (34a - d) by the first pressure medium pumping device (24), that is, the brake pressure generator (22). The circuit pressure regulating valves (44a, 44b) are not driven and controlled electrically and thus are open. As a result, as shown in Fig. 2c, no differential pressure is applied to this directional control valve.

[0047] The second pressure medium pumping device (28) of the brake pressure modulator (26) is not required during this first time phase t1. Its drive unit (58) is not driven and controlled electrically, and thus its rotational speed is zero as shown in Fig. 2d.

[0048] During the subsequent second time phase t2, the brake pressure that already prevails in the wheel brakes (34a to d) is increased. The pressure medium required for this can no longer be provided by the first pressure medium pumping device (24) of the brake pressure generator (22). This is because the displacer of the brake pressure generator (22) has already reached the turning point outside the displacer or is present in the vicinity of this outer turning point. Accordingly, the electronic control device (52a) of the brake pressure generator (22) outputs a corresponding request signal to the electronic control device (52b) of the brake pressure modulator (26). The electronic control device (52b) drives and controls the motor (62) of the second pressure medium pumping device (28) in accordance with the request signal. The motor (62) rotates, for example, at a constant rotational speed as shown in Fig. 2d and drives the second pressure medium pumping device (28) accordingly. The second pressure medium pumping device (28) constantly pumps an increasing volume of pressure medium to the corresponding wheel brakes (34a to d) (graph 2b), and the pressure in this wheel brake (34a to d) rises to a maximum value (graph 2a).

[0049] The pressure regulation within the brake circuits (18a, 18b) or within the wheel brakes (34a - d) connected to the brake circuits (18a, 18b) is carried out by electrical drive control of the circuit pressure regulating valves (44a, 44b). For this purpose, the electrical drive control of the circuit pressure regulating valves (44a, 44b) gradually reduces the throttle cross - section to zero, whereby the pressure loss between the pressure medium in - side of the circuit pressure regulating valves (44a, 44b) and the pressure medium out - side of the circuit pressure regulating valves (44a, 44b) uniformly rises to a maximum value, as can be read from Figure 2c. Within the working chamber (60) of the first pressure medium pumping device (24), during this second time phase t2, the pressure drops to the atmospheric pressure level (graph 2a). The reason for this is that the second pressure medium pumping device (28), i.e., the brake pressure modulator (26), sucks in the pressure medium required for pressure increase from the reservoir (32), and the corresponding suction path is connected to this first pressure medium pumping device (24) via the open plunger cut - off valves (42a, 42b). The atmosphere prevails in the reservoir (32) beforehand.

[0050] Based on the pressure medium pumping to the wheel brakes (34a - d) by the second pressure medium pumping device (28), the pressure - volume - characteristic curve of the non - actuated brake device (10) no longer coincides with the structurally determined pressure - volume - characteristic curve of the first pressure medium pumping device (24). The structurally determined pressure - volume - characteristic curve of the first pressure medium pumping device (24) is shifted in the higher pressure direction as described above. This state can be confirmed within the framework of the characteristic curve inspection regularly carried out by the electronic control devices (52a, 52b) of the non - actuated brake device (10). For this purpose, the actually measurable actual value regarding the brake pressure and the actual value calculated from the operating parameters of the brake pressure generator (22) regarding the volume of the pressure medium pumped are compared with the known target values of the structurally predefined pressure - volume - characteristic curve of the first pressure medium pumping device (24). If the confirmed deviation is greater than the predefined limit value, this deviation is unacceptable and must be corrected. This will be described in detail later.

[0051] During the time phase t3.1 when the pressure within the wheel brakes (34a - d) is kept constant and neither of the pressure medium pumping devices (24, 28) pumps, the electrical drive control of the circuit pressure regulating valves (44a, 44b) is gradually canceled. As a result, the circuit pressure regulating valves (44a, 44b) open, expanding the throttle cross-section. Consequently, the differential pressure across these circuit pressure regulating valves (44a, 44b) decreases, and pressure is again formed within the working chamber (60) of the first pressure medium pumping device (24) via the pressure medium line controlled by the circuit pressure regulating valves (44a, 44b) and leading to the brake pressure generator (22). The throttling action of the circuit pressure regulating valves (44a, 44b) is adjusted in time phase t3.2 such that, as shown in the figure, a pressure level corresponding to the maximum pressure p(max) that the first pressure medium pumping device (24) can originally form in the brake circuits (18a, 18b) due to its design occurs within the working chamber (60). p(max) is entered as a horizontal line in Figure 2a. Instead of p(max), a pressure arbitrarily lower than p(max) may be set.

[0052] As can be read from the graph shown in Figure 2c, at this time, in the circuit pressure regulating valves (44a, 44b), only a relatively low differential pressure occurs corresponding to the relatively large throttle cross-section set for the circuit pressure regulating valves (44a, 44b). The pressure within the wheel brakes (34a - d) does not change during time phases t3.1 and t3.2 because the pressure medium is neither pumped into the wheel brakes (34a - d) nor flows out of the wheel brakes (34a - d) to a significant extent.

[0053] In the time phase t4 towards the end, the brake request is canceled, and accordingly, the brake pressure within the wheel brakes (34a - d) decreases. In this case, the brake pressure cancellation is carried out gradually, and as a result, the brake pressure transition follows a straight-line ramp from the upper left to the lower right (Figure 2a).

[0054] For the sake of distinction, during this pressure relief phase, which is referred to as the pressure relief phase controlled by the push-off body, the circuit pressure regulating valves (44a, 44b) are controlled to shift to their open positions. That is, the electrical drive control of the circuit pressure regulating valves (44a, 44b) is abandoned. The pressure medium from the wheel brakes (34a - d) thereby flows into the working chamber (60) of the first pressure medium pumping device (24). In parallel with this, the electrical drive control of the drive unit (58) of the first pressure medium pumping device (24) and thus the operation of the push-off body in the pressure relief direction, i.e., in the direction of the turning point inside the push-off body, are carried out.

[0055] In the subsequent time phase t5, the pressure relief phase controlled by this push-off body, due to the operation of the drive unit (58) of the first pressure medium pumping device (24) in the direction of the inner turning point, continues. The pressure relief remains unchanged and is discernible from the graph in Figure 2a according to the ramp function described above.

[0056] As soon as the plunger piston (54) of the first pressure medium pumping device (24) is present near the inner turning point of the plunger piston (54), the maximum receiving volume of the working chamber (60) is exhausted. Figure 2a shows this by the fact that the volume of the pressure medium initially displaced into the brake circuits (18a, 18b) by the first pressure medium pumping device (24) has now reached zero again. By canceling the electrical drive control of the drive unit (58) of the first pressure medium pumping device (24) by the electronic control device (52a), the pressure relief phase controlled by the push-off body ends. In parallel with this, a corresponding signal is output to the electronic control device (52b) of the brake pressure modulator (26).

[0057] At the start of the so-called valve-controlled decompression phase that follows, based on this electronically input information, the circuit pressure regulating valves (44a, 44b) are actuated electrically again. By means of a corresponding drive control signal, the circuit pressure regulating valves (44a, 44b) are shifted to a throttle position where the set throttle cross-section corresponds to the brake pressure assigned to the position of the plunger piston (54) within the plunger cylinder (56). In parallel with this, as shown in Fig. 2b, the plunger discharge valve (40) is drive-controlled and thus shifted from the closed position of the plunger discharge valve (40) to the open position of the plunger discharge valve (40). Since atmospheric pressure prevails in advance in the reservoir (32) of the non-manual braking device (10), this results in the pressure in the brake pressure generator (22) and thus also the pressure on the pressure medium outlet side of the circuit pressure regulating valves (44a, 44b) dropping to atmospheric pressure. As a result, the resulting differential pressure represents the current brake request.

[0058] Instead of the pressure reduction via the drive control of the plunger discharge valve (40), this pressure reduction may, in principle, be controlled via the movement of the plunger piston (54). For this purpose, however, a bleed-off line (not shown) would be necessary. The bleed-off line communicates from the working chamber (60) to the reservoir (32) and opens into the working chamber (60) in the region of the turning point inside the plunger piston (54). The incoming plunger piston (54) passes over this opening and only when the plunger piston (54) reaches the inner turning point does it completely release the bleed-off line. The differential pressure is now gradually reduced to zero or to the driver brake request presented by a linear change in the electrical drive control of this circuit pressure regulating valve (44a, 44b) by the electronic control unit (52b) (see Figure 2c). For this purpose, this circuit pressure regulating valve (44a, 44b) gradually opens again until the maximum throttle cross-section of the circuit pressure regulating valve (44a, 44b) and finally until the residual pressure remaining in the brake circuit (18a, 18b) is completely eliminated as shown in the graph shown in Figure 2a. This brake pressure reduction is also carried out constantly or continuously, so that the previous course of the brake pressure reduction continues seamlessly. Noise or deceleration changes perceptible to the vehicle occupants do not therefore occur.

[0059] By the controlled opening of the circuit pressure regulating valves (44a, 44b) and the simultaneous opening of the plunger discharge valve (40), the pressure medium is thus discharged from the wheel brakes (34a - d), via the first pressure medium pumping device (24), into the reservoir (32) of the non - actuated braking device (10) until the atmospheric pressure level prevails in the wheel brakes (34a - d) and the position of the plunger piston (54) of the first pressure medium pumping device (24) in the plunger cylinder (56) correlates with this. The pressure - volume - characteristic curve of the non - actuated braking device (10) now coincides again with the pressure - volume - characteristic curve of the first pressure medium pumping device (24). The proposed method is hereby completed, and the brake pressure modulator (26) returns to the passive state of the brake pressure modulator (26). In some cases, subsequent renewed brake pressure boosting is again controlled in the normal way, i.e., by the adapted electrical drive control of the drive unit (58) of the first pressure medium pumping device (24) or of the brake pressure generator (22).

[0060] The method described should definitely be carried out at least if the described shift of the pressure - volume - characteristic curve takes place or if it is considered to be of an unacceptable scale. Such a check is in any case carried out regularly in the non - actuated braking device and proceeds as follows, as shown in FIG. 3: First, in step (80), a deviation between a structurally determined pressure-volume-target characteristic line and a pressure-volume-actual characteristic line of the non-manual braking device is identified. For this purpose, various methods can be used. In a first variant, an actual value of the braking pressure is measured by a pressure sensor (61) provided in the brake circuit (18b) and compared with a target braking pressure. The target braking pressure, on the other hand, can be derived from a brake request and thus from a stroke signal of a stroke measurement sensor system (64) connected to the pedal (12) via a known pressure-volume characteristic line of the non-manual braking device (10). When a deviation occurs in this comparison, the volume of the pressure medium additionally displaced into the brake circuits (18a, 18b) by the second pressure medium pumping device (28) is identified from the confirmed deviation via the known pressure-volume characteristic line.

[0061] Alternatively, the volume of the pressure medium additionally displaced by the second pressure medium pumping device (28) may be determined by multiplying the operating duration of the motor (62) driving the second pressure medium pumping device (28) by the rotational speed of the motor (62) and a known value of the volume of the pressure medium displaced per revolution of the motor (62). Information about when and for what length of time the second pressure medium pumping device (28) has been operated can be derived from a request signal output from the control device (52a) of the brake pressure generator (22) to the control device (52b) of the brake pressure modulator (26).

[0062] Accordingly, when the volume of the pressure medium additionally displaced for pressure increase by the second pressure medium pumping device (28) is identified, in a subsequent second step (82), this value is compared with a determinable limit value (88). If it is below this limit value, the implementation of the described method can be omitted. This is because, in this case, the influence of the volume of the pressure medium additionally displaced on the pressure-volume characteristic line is acceptable.

[0063] However, when the required value is equal to or even higher than the limit value (88), the control method described above or the alternative control method described below is implemented, and this implementation is carried out within the framework of the ongoing braking process. Specifically, during the course of this braking process, when the brake request is canceled, it is implemented. The implementation of this method is indicated by the symbol labeled (86) in Figure 3.

[0064] The alternative method mentioned for controlling the non - man - power brake device (10) with redundant brake pressure generation is shown based on a total of 4 graphs in Figures 4a - 4d. These graphs, similar to the graphs in Figure 2, are recorded in time synchronization with each other, are divided into a plurality of time phases, and show the same transition parameters over time respectively.

[0065] In the first time phase t1, again the brake pressure is increased by the operation of the first pressure medium pumping device (24). The plunger discharge valve (40) is closed at this time, and the circuit pressure regulating valves (44a, 44b) are open. As a result, no differential pressure is applied to the circuit pressure regulating valves (44a, 44b) (Figure 4c). The motor (62) of the second pressure medium pumping device (28) is not driven and controlled electrically and thus is not rotating.

[0066] During the second time phase t2, the existing brake pressure is increased. The pressure medium required for this is provided by the second pressure medium pumping device (28) so that it can be read from the volume characteristic line in the graph shown in Fig. 4b and the rotational speed characteristic line of the motor (62) of the second pressure medium pumping device (28) shown in Fig. 4d. At the start of the second time phase t2, the plunger discharge valve (40) is driven and controlled electrically, thereby releasing the pressure medium connection of the first pressure medium pumping device (24) to the reservoir (32). The pressure in the working chamber (60) of the first pressure medium pumping device (24), and thus also the pressure on the pressure medium outlet side of the circuit pressure regulating valves (44a, 44b), accordingly retreats to atmospheric pressure. By means of the adapted electrical drive control of the circuit pressure regulating valves (44a, 44b), the pressure difference occurring in these circuit pressure regulating valves (44a, 44b) is set. The magnitude of the pressure difference depends on the brake pressure in the wheel brakes (34a - d) or the pressure exerted on the pressure medium inlet side of this directional control valve.

[0067] An alternative control of the plunger discharge valve (40), not visible in Fig. 4, would be to open this plunger discharge valve (40) only when a pressure reduction via the circuit pressure regulating valves (44a, 44b) is actually required or carried out. During pressure increase, the plunger discharge valve (40) would, in contrast, be closed, and the flow-through of the plunger discharge valve (40) would thus only be carried out in one direction, namely in the direction towards the reservoir (32). The advantage of this alternative control is that in this case, the plunger discharge valve (40) can be structurally implemented more favorably. This is because, for example, a filter device for removing foreign matter from the pressure medium flowing from the reservoir (32) into the plunger discharge valve (40) can be omitted.

[0068] In time phase t3, the brake pressure is continuously increased until it exceeds the maximum pressure p(max) that can originally be set in the brake circuits (18a, 18b) by the first pressure medium pumping device (24) due to design. The volume of the pressure medium required for this is also provided by the second pressure medium pumping device (28), and the second pressure medium pumping device (28) is driven for this purpose (see FIGS. 4b and 4d). Along with the increasing brake pressure, the differential pressure in the circuit pressure regulating valves (44a, 44b) also increases (FIG. 4c).

[0069] Upon reaching the maximum pressure in the brake circuits (18a, 18b), the pressure medium pumping by the second pressure medium pumping device (28) ends (motor speed zero shown in FIG. 4d), and the plunger discharge valve (40) remains open continuously.

[0070] The brake change in time phase t3 is adjusted by electrical drive control of the circuit pressure regulating valves (44a, 44b). In connection with the still-open plunger discharge valve (40), in the case of pressure reduction at this time, the pressure medium is discharged from the wheel brakes (34a - d) into the reservoir (32) of the non - servo brake device (10) via the first pressure medium pumping device (24), or in the case of pressure increase, the pressure medium is sucked from the reservoir (32) by the second pressure medium pumping device (28) through the open high - pressure switching valves (46a, 46b) and pushed into the wheel brakes (34a - d). In such a pressure - increasing phase, the circuit pressure regulating valves (44a, 44b) are traceably closed.

[0071] Brake pressure reduction is carried out from time phase t4. This is because the set brake request is canceled. First, at this time, the pressure medium is discharged from one or more wheel brakes (34a to d) as before, through the opened or partially opened circuit pressure regulating valves (44a, 44b), the working chamber (60) of the first pressure medium pumping device (24), and the also opened plunger discharge valve (40) to the reservoir (32). The adjustment of the brake pressure reduction is carried out by continuous adaptation of the corresponding electrical drive control of the circuit pressure regulating valves (44a, 44b), and accordingly, it is also called the pressure reduction phase controlled by the valves.

[0072] Thus, based on the advanced position of the push body of the first pressure medium pumping device (24) in the plunger cylinder (56), when the brake pressure in the wheel brakes (34a to d) is decreasing to such an extent that the volume of the working chamber (60) is sufficient to completely receive the volume of the pressure medium in the brake circuits (18a, 18b) for further brake pressure reduction to zero, the electrical drive control of the plunger discharge valve (40) is canceled at the end of time phase t4.

[0073] Accordingly, the plunger discharge valve (40) returns to the closed position of the plunger discharge valve (40), cutting off the pressure medium connection of the first pressure medium pumping device (24) to the reservoir (32). In parallel with this, the electrical drive control of the circuit pressure regulating valves (44a, 44b) is terminated. The circuit pressure regulating valves (44a, 44b) return to the open position of the circuit pressure regulating valves (44a, 44b), and accordingly, the differential pressure no longer occurs in the circuit pressure regulating valves (44a, 44b) (Figure 4c). By the opening of the circuit pressure regulating valves (44a, 44b), pressure is formed again in the working chamber (60) of the first pressure medium pumping device (24). The resulting pressure level corresponds to the pressure level assigned to the position of the plunger piston (54) in the plunger cylinder (56).

[0074] A further reduction in brake pressure (a pressure-relieving phase controlled by a pump), occurs at time phase t5 by operation of the drive unit (58) of the first pressure medium pumping device (24) or by driving the plunger piston (54) in the pressure-relieving direction. When this displacing body reaches the turning point inside the displacing body, the brake pressure reaches zero and the pressure-volume characteristic curve of the non-manual brake device (10) coincides again with the pressure-volume characteristic curve of the first pressure medium pumping device (24).

[0075] Finally, it should be noted that the method described can be carried out even if the displacing body of the first pressure medium pumping device (24) does not exist at the outer turning point at the start of the pressure-relieving phase controlled by the pump. In this case, the brake pressure is controlled by a valve and is reduced to a pressure level corresponding to the corresponding position of the plunger piston (54) in the plunger cylinder (56) according to the known pressure-volume characteristic curve of the non-manual brake device (10). The residual pressure still present in the brake circuit (18a, 18b) in this case could then be reduced to atmospheric pressure by further return travel of the displacing body of the brake pressure generator (22) to the inner turning point.

[0076] It should be made clearer that FIGS. 2 and 4 show a braking process in which the brake pressure corresponding to the brake request is higher than the maximum pressure p(max) that can be generated in the brake circuit (18a, 18b) by the first pressure medium pumping device (24). However, the above is not a prerequisite for implementing the described method. This is because in the non-manual brake device (10), there may also occur a braking process in which the pressure medium is pumped into the brake circuit (18a, 18b) by the second pressure medium pumping device (28) and in this case, the maximum pressure that can be provided by the first pressure medium pumping device (24) is not reached.

[0077] The trigger for implementing the method underlying the present invention is, therefore, not the brake pressure in the brake circuits (18a, 18b), but rather the volume of the pressure medium that is pumped into the brake circuits (18a, 18b) by the second pressure medium pumping device (28) to generate the brake pressure. The implementation of this method can be omitted when this volume assumes a value below a limit value that can be determined in the electronic control devices (52a, 52b). In this case, the deviation of the pressure-volume characteristic curve of the non-manual brake device (10) from the pressure-volume characteristic curve of the first pressure medium pumping device (24) is still acceptable.

[0078] Without departing from the basic idea of the invention claimed in claim 1, it is obvious that further modifications and / or advantageous developments are possible in the embodiments of the invention described. This basic idea lies, in particular, in that, under the premises explained in the specification, the reduction of the brake pressure in the brake circuits (18a, 18b) of the non-manual brake device (10) with a redundant pressure supply has a pressure reduction phase controlled by a valve, in which the pressure medium is discharged to the reservoir (32) by the electrically driven control of the circuit pressure regulating valves (44a, 44b). The connection of the pressure medium to the reservoir (32) can, in this case, be guided via the line in which the plunger discharge valve (40) is present or via a bleed line having an opening controlled by the plunger piston (54) into the working chamber (60).

Explanation of Reference Signs

[0079] 10 Non-manual brake device 12 Pedal 14 Master brake cylinder 16a, 16b Pressure chamber 18a, 18b Brake circuit 20 Pedal feel simulator 22 Brake pressure generator 24 First pressure medium pumping device 26 Brake pressure modulator 28 Second pressure medium pumping device Hydraulic units 30a, 30b Reservoir 32 Wheel brakes 34a - d Simulator valve 36 Circuit cut-off valves 38a, 38b Plunger discharge valve 40 Plunger cut-off valves 42a, 42b Circuit pressure regulating valves 44a, 44b High-pressure switching valves 46a, 46b Pressure intensifying valves 48a - d Pressure reducing valves 50a - d Electronic control devices 52a, 52b Plunger piston 54 Plunger cylinder 56 Electric drive unit 58 Working chamber 60 Pressure sensors 61a, 61b Motor 62 Stroke measurement sensor system 64 First pressure characteristic line 68a Second pressure characteristic line 68b First volume characteristic line 70a Second volume characteristic line 70b Signal characteristic line 72 Differential pressure characteristic line 74 Rotational speed characteristic line 76 Step 80 Second step 82 Implementation of the method 86 Limit value 88 p(max) Maximum pressure t1 First time phase t2 Second time phase t3.1 Time phase t3.2 Time phase t4 Time phase t5 Time phase

Claims

1. A method for controlling an electronically slip-controllable non-manual braking device (10) with a redundant brake pressure supply, wherein the non-manual braking device (10) comprises a brake request detection device (12) for setting a brake request, a brake pressure generator (22) for supplying a pressure medium to wheel brakes (34a - d) provided in at least one connected brake circuit (18a, 18b) under a brake pressure corresponding to the brake request, the brake pressure generator (22) is equipped with a controllably drivable first pressure medium pumping device (24), the first pressure medium pumping device (24) has a displacing body (54), and the displacing body (54) is in a cylinder (56) and is drivable for brake pressure boosting to an outer turning point in the boosting direction and for brake pressure reducing to an inner turning point in a brake pressure reducing direction opposite to the brake pressure boosting direction for brake pressure reduction, and together with the cylinder (56) defines a variable volume working chamber (60), a brake pressure generator (22), a brake pressure modulator (26) for individually adjusting the brake pressure in each one of the plurality of wheel brakes (34a - d) of the brake circuit (18a, 18b), the brake pressure modulator (26) is connected to the brake circuit (18a, 18b) in parallel with the brake pressure generator (22) and has a controllably drivable second pressure medium pumping device (28), a brake pressure modulator (26), a reservoir (32) for the pressure medium, an electrically drivable and controllable plunger discharge valve (40) for controlling a first pressure medium connection from the first pressure medium pumping device (24) to the reservoir (32) of the non-manual braking device (10), An electrically drivable pressure regulating valve (44a, 44b) for adjusting the brake pressure in the brake circuit (18a, 18b), and at least one electronic control device (52a, 52b) for electrically driving and controlling the respectively assigned brake pressure generator (22) and the brake pressure modulator (26) as required, having In a method, determine how much volume of the pressure medium is pumped into the brake circuit (18a, 18b) by the second pressure medium pumping device (28) for the pressure increase of the brake pressure, compare the determined pressure medium volume with a pre-given limit value (88), The brake pressure reduction has a decompression phase, in which a pressure medium connection is formed in which the pressure medium is discharged from the brake circuit (18a, 18b) into the reservoir (32) of the non-manual brake device (10), when the determined pressure medium volume is greater than or equal to the limit value (88), control the volume of the pressure medium discharged into the reservoir (32) by adapting the electrical drive control of the pressure regulating valve (44a, 44b), A method for controlling an electronically slip-controllable non-manual brake device with redundant brake pressure supply, characterized in that.

2. The pressure medium connection between the brake circuit (18a, 18b) and the reservoir (32) is formed by simultaneous electrical drive control of the plunger discharge valve (40) and the pressure regulating valve (44a, 44b), The method according to claim 1, characterized in that.

3. The method is carried out when the brake pressure in the brake circuit (18a, 18b) is higher than the maximum pressure p(max) that can be applied into the brake circuit (18a, 18b) by the first pressure medium pumping device (24), The method according to claim 1 or 2, characterized in that.

4. The brake pressure reduction has a further pressure reduction phase controlled by a displacing body, and in the pressure reduction phase controlled by the displacing body, the pressure medium connection to the reservoir (32) is closed, and by electric drive control of the drive unit (58), displacement of the displacing body (54) of the first pressure medium pumping device (24) in the pressure reduction direction is performed. The method according to any one of claims 1 to 3, characterized in that.

5. When the brake pressure in the brake circuit (18a, 18b) is a brake pressure and the displacing body (54) of the first pressure medium pumping device (24) correlates with the brake pressure generated in the brake circuit (18a, 18b) at the current position of the displacing body (54) in the cylinder (56) in consideration of the pressure-volume characteristic line at the base of the non-manual brake device (10), the pressure reduction phase ends. The method according to any one of claims 1 to 3, characterized in that.

6. Control the brake pressure reduction so that a constantly decreasing transition occurs. The method according to any one of claims 1 to 5, characterized in that.

7. When the displacing body (54) of the first pressure medium pumping device (24) reaches the turning point inside the displacing body (54), the brake pressure reduction ends. The method according to any one of claims 1 to 6, characterized in that.

8. The volume of the pressure medium displaced by the second pressure medium pumping device (28) is determined based on a comparison with the known pressure-volume characteristic line of the non-manual brake device (10), the pressure in the brake circuit (18a, 18b), and the position of the displacing body (54) of the first pressure medium pumping device (24) in the cylinder (56) assigned to the pressure. The method according to any one of claims 1 to 7, characterized in that...

9. Determining the volume of the pressure medium displaced by the second pressure medium pumping device (28) by multiplying the operating duration of the motor (62) of the second pressure medium pumping device (28) by the rotational speed of the motor (62) and the known volume of the pressure medium displaced by the second pressure medium pumping device (28) per revolution of the motor (62). The method according to any one of claims 1 to 7, characterized in that...

10. Performing a further third pressure reduction phase in which a controllable pressure medium connection is formed between the working chamber (60) of the first pressure medium pumping device (24) and the brake circuit (18a, 18b) by means of an electrical drive control of the pressure regulating valves (44a, 44b), and controlling the drive of the pressure regulating valves (44a, 44b) during the third pressure reduction phase such that the pressure in the working chamber (60) is reduced to the maximum pressure p(max) that can be applied by the first pressure medium pumping device (24) into the brake circuit (18a, 18b). The method according to claim 3, characterized in that...

11. Performing the third pressure reduction phase at the start of the brake pressure reduction. The method according to claim 10, characterized in that...

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