Control Device and Operating Method of a Regenerative Brake System for a Vehicle

Abstract

The present invention relates to a control device (16) for a regenerative braking system of a vehicle, and when it is possible to cause at least part of a required vehicle deceleration by means of at least one electric motor, a sub-step of determining a target differential pressure between a first wheel brake cylinder (10) of the braking system and a second wheel brake cylinder (12) of the braking system, a sub-step of controlling at least one wheel inlet valve (22) upstream of the second wheel brake cylinder (12) of the braking system by means of a current signal (52) output to the at least one wheel inlet valve (22) taking into account the determined target differential pressure, and a sub-step of determining a target current intensity of the current signal (52) taking into account the determined target differential pressure by selecting the target current intensity or an output value of the target current intensity of the current signal (52) from a value range including at least three current intensity values, and relates to an operating method for a regenerative braking system of a vehicle by executing differential pressure control within wheel brake cylinders (10, 12) of the braking system.

Description

Technical Field

[0001] The present invention relates to a control device for a regenerative brake system of a vehicle and a regenerative brake system of a vehicle. Further, the present invention relates to a method of operating a regenerative brake system of a vehicle.

Background Art

[0002] Figures 1a and 1b show coordinate systems for explaining a conventional method of operating a regenerative brake system of a vehicle known to the applicant as prior art inside. The abscissas of the coordinate systems in Figures 1a and 1b are each a time axis t.

[0003] In the first braking process shown by the coordinate system of Figure 1a, the driver of the vehicle requests a vehicle deceleration a not equal to zero by operating the brake operation element of the brake system from time t0. Therefore, in the conventional method, from time t0, the operating state Φ of the electric motor of the brake system operable in the regeneration mode Φ r is switched from the non-active mode Φ 0 to the regeneration mode Φ r During the period between time t0 and t1, the non-zero vehicle deceleration a requested by the driver can be generated by the electric motor operating in the regeneration mode Φ r Therefore, during the period between time t0 and t1, the first target brake pressure p to be adjusted in the first wheel brake cylinder of the brake system assigned to the first axle of the vehicle 1target and the second target brake pressure p to be adjusted in the second wheel brake cylinder of the brake system assigned to the second axle of the vehicle 2targetis equal to zero. In order to avoid an increase in the brake pressure in each one of the first wheel brake cylinders and each one of the second wheel brake cylinders for each brake circuit between time t0 and t1, a second wheel outlet valve, which is disposed behind the second wheel brake cylinder, is switched to an open state between time t0 and t1, which is not shown in the coordinate system of FIG. 1a. However, based on the coordinate system of FIG. 1a, it can be recognized that simultaneously with the switching of the first wheel inlet valve, which is disposed in front of the first wheel brake cylinder, to an open state, the second wheel inlet valve, which is disposed in front of the second wheel brake cylinder, is also switched to an open state between time t0 and t1. For this purpose, the current intensity I of the current signal output to the second wheel inlet valve, which is open when de-energized, is plotted in the coordinate system of FIG. 1a. Accordingly, between time t0 and t1, the first actual brake pressure p 1 present in the first wheel brake cylinder and the second actual brake pressure p 2 present in the second wheel brake cylinder are (substantially) equal to zero.

[0004] From time t1, the vehicle deceleration a required by the driver cannot be generated only by the electric motor operating in the regeneration mode Φ r . However, the required vehicle deceleration a can be generated between time t1 and t2 by the electric motor operating in the regeneration mode Φ r and by the first wheel brake cylinder assigned to the first axle of the vehicle. Accordingly, between time t1 and t2, the first target brake pressure p 1target to be adjusted in the first wheel brake cylinder is determined to be not equal to zero, while the second target brake pressure p 2targetremains equal to zero between times t1 and t2. Further, the first wheel outlet valve disposed downstream of the first wheel brake cylinder is held in the closed state from time t1, while the second wheel outlet valve disposed downstream of the second wheel brake cylinder is continuously controlled to be in the open state between times t1 and t2. Time interval T 0 During the differential pressure control performed by the second wheel inlet valve of the second wheel brake cylinder within, the first actual brake pressure p1 existing in the first wheel brake cylinder is adjusted according to the determined first target brake pressure p 1target according to. According to the conventional method, the differential pressure control during time interval T 0 is performed by the exchange between the overflow (Ueberstromung) and the underflow (Unterstromung) of the second wheel inlet valve. Additionally, the brake fluid can also be pumped from at least one low-pressure reservoir disposed downstream of the first wheel outlet valve and the second wheel outlet valve into the brake system by the non-zero pump rotational speed n of at least one pump of the brake system. However, as indicated by arrow 2, during the period between times t1 and t2, in many cases, a "wave-shaped" pressure increase occurs in the first wheel brake cylinder.

[0005] From time t2, the electric motor operating in the regeneration mode Φ r and the first wheel brake cylinder assigned to the first axle of the vehicle are no longer sufficient to generate a non-zero vehicle deceleration a required. Therefore, from time point t2, the second target brake pressure p to be adjusted in the second wheel brake cylinder 2targetis not equal to zero and is determined. The second wheel outlet valve, which is disposed behind the second wheel brake cylinder, is held in a closed state from time t2 (similarly to the first wheel outlet valve disposed behind the first wheel brake cylinder). By the differential pressure control executed by the second wheel inlet valve, the first actual brake pressure p existing in the first wheel brake cylinder 1 is adjusted according to the determined first target brake pressure p 1target and the second actual brake pressure p existing in the second wheel brake cylinder 2 is continuously adjusted according to the second target brake pressure p 2target . In the conventional method, this is continuously done by the exchange between the overflow of the second wheel inlet valve and the underflow of the second wheel inlet valve. The pressure increase in the second wheel brake cylinder caused in this way is shown by arrow 4, which may inconveniently cause a rapid pressure decrease in the first wheel brake cylinder.

[0006] Also in the second braking process shown by the coordinate system of FIG. 1b, the driver requests a vehicle deceleration a not equal to zero by operating the brake operating element from time t0. However, this vehicle deceleration can still be caused by the electric motor operating in the regeneration mode Φ r between time t0 and t1. However, compared with the above-described first braking process, in the second braking process, the driver requests much faster braking of the vehicle. Also in the second braking process, the vehicle deceleration a not equal to zero requested by the driver can be achieved by the electric motor operating in the regeneration mode Φ r between time t0 and t1, only by the first wheel brake cylinder of the first axle, and from time t2, by the electric motor operating in the regeneration mode Φ r and only by the first wheel brake cylinder and the second wheel brake cylinder of the second axle. The first target brake pressure p to be adjusted in the first wheel brake cylinder 1targetand a second target brake pressure p to be adjusted in the second wheel brake cylinder 2target is determined accordingly. A first actual brake pressure p present in the first wheel brake cylinder 1 and a second actual brake pressure p present in the second wheel brake cylinder 2 To adjust, during a time interval T 0 newly, by a second wheel outlet valve pre-positioned in the second wheel brake cylinder, differential pressure control is carried out by exchanging between an overflow of a second wheel inlet valve and an underflow of the second wheel inlet valve by a conventional method. Arrow 6 indicates that, based on a requirement for faster braking of the vehicle, a large difference can occur between a first target brake pressure p to be adjusted in the first wheel brake cylinder 1target and a first brake pressure p actually increased in the first wheel brake cylinder 1 which may be felt uncomfortably by the driver as a "soft" brake operation element. SUMMARY OF THE INVENTION

[0007] The present invention provides a control device for a regenerative brake system of a vehicle having the features of claim 1, a regenerative brake system of a vehicle having the features of claim 6, and an operating method for a regenerative brake system of a vehicle having the features of claim 7.

[0008] The present invention provides the possibility of operating the regenerative braking system of a vehicle such that the driver of the vehicle (substantially) does not perceive the harmonization processes (Verblendvorgaenge) that are carried out during the operation of the brake operating element of the braking system. For example, the braking of the vehicle with only at least one electric motor operating in the regeneration mode and the switching of the braking of the vehicle between at least one electric motor and the first wheel brake cylinder of the braking system assigned to the first axle of the vehicle do not cause / hardly cause an inconvenient "wavy" pressure increase in the first wheel brake cylinder. The switching of the braking of the vehicle by at least one electric motor, by the first wheel brake cylinder, and by the second wheel brake cylinder of the braking system assigned to the second axle of the vehicle also does not (normally) cause a significant deviation of the first actual brake pressure present in the first wheel brake cylinder from the first target brake pressure desired for the first wheel brake cylinder or a decompression in the first wheel brake cylinder. Thus, the possibility of operating the regenerative braking system of the vehicle provided by the present invention provides improved driving and braking comfort for the driver of the vehicle. Thus, the present invention contributes to making the driver inclined to purchase a vehicle equipped with a regenerative braking system, and the driving of this vehicle is also associated with a reduction in energy consumption and, in some cases, a reduction in harmful substance emissions.

[0009] In an advantageous embodiment of the control device, the electronics in the differential pressure control mode are designed and / or programmed to determine the target current intensity or the output value of the target current intensity of the current signal according to a specified continuous function having a value range including at least three current intensity values depending on the determined target differential pressure. This enables the "smooth" control of at least one (second) wheel inlet valve upstream of the second wheel brake cylinder by the embodiment of the control device described herein.

[0010] Preferably, even after the start of the differential pressure control mode, the electronic device additionally takes into account, for each of at least one first actual brake pressure in the first wheel brake cylinder measured or estimated during a specified comparison time interval from a first target brake pressure to be adjusted into the first wheel brake cylinder, respectively, at the same time, and determines an offset value of the target current intensity of the current signal, and is designed and / or programmed to determine the target current intensity of the current signal as the sum of the output value of the target current intensity and the offset value. The offset value thus determined or the resulting target current intensity can advantageously compensate for component tolerances and / or degradation phenomena of the respective regenerative brake system.

[0011] As an advantageous development, after the start of the differential pressure control mode, the electronic device additionally identifies, for each of at least one first actual brake pressure in the first wheel brake cylinder measured or estimated, the period during which it differs from a first target brake pressure to be adjusted into the first wheel brake cylinder, respectively, at the same time, by at least one specified minimum pressure deviation, and if the identified period exceeds a specified time threshold, determines the target current intensity of the current signal to be switched to a closed valve state during a closing valve time specified or determined by the current signal output to at least one wheel inlet valve during the closing valve time specified or determined thereby. In this way, the occurrence of a "soft" brake operating element / brake pedal, which often occurs in the prior art in many cases, can be avoided by the embodiments of the control device described herein.

[0012] As another advantageous development form, the electronic device may be designed and / or programmed to determine a target differential pressure as the difference between a first target brake pressure to be adjusted in a specified or determined first wheel brake cylinder and a second target brake pressure to be adjusted in a specified or determined second wheel brake cylinder at the beginning of the differential pressure control mode. However, if the measured or estimated first actual brake pressure in the first wheel brake cylinder is at least one specified limit deviation less than the first target brake pressure to be adjusted in the first wheel brake cylinder at the same time, the electronic device is designed and / or programmed to determine the target differential pressure as the difference between the first actual brake pressure in the measured or estimated first wheel brake cylinder and the second target brake pressure to be adjusted in the second wheel brake cylinder during the specified or determined transition time. Therefore, the development form of the control device described herein can advantageously respond to a significant deviation of the first actual brake pressure from the first target brake pressure, thereby preventing the occurrence of the same / corresponding deviation of the second actual brake pressure in the second wheel brake cylinder from the second target brake pressure to be adjusted in the second wheel brake cylinder.

[0013] The above-mentioned advantages are also guaranteed in a regenerative brake system of a vehicle comprising such a control device, a first wheel brake cylinder assigned to a first axle of the vehicle, a second wheel brake cylinder assigned to a second axle of the vehicle, and at least one wheel inlet valve upstream of the second wheel brake cylinder.

[0014] Furthermore, the implementation of a corresponding operating method of the regenerative brake system of the vehicle also provides the above-mentioned advantages. It is explicitly mentioned that the operating method of the regenerative brake system of the vehicle can also be developed according to the embodiments of the control device described above.

Brief Description of the Drawings

[0015]

Figure 1a

Figure 1b

Figure 2

Figure 3a

Figure 3b

[0016] Hereinafter, other features and advantages of the present invention will be described in detail with reference to the drawings.

[0017] FIG. 2 shows a schematic diagram of a regenerative braking system of a vehicle for explaining the operating principle of an embodiment of a control device that cooperates with the regenerative braking system of the vehicle.

[0018] The regenerative braking system schematically shown in FIG. 2 has a first wheel brake cylinder 10 and a second wheel brake cylinder 12. The first wheel brake cylinder 10 is assigned to the first axle of a vehicle equipped with the braking system, and the second wheel brake cylinder 12 is assigned to the second axle of the vehicle. This can be understood to mean that the first wheel brake cylinder 10 is assembled to the first axle of the vehicle and the second wheel brake cylinder 12 is assembled to the second axle. In the braking system of FIG. 2, a braking circuit of an X-type configuration is realized merely by way of example, and each one of the first wheel brake cylinders 10 and each one of the second wheel brake cylinders 12 are coupled to one of two braking circuits 14a and 14b. The first axle can be, for example, a front axle, while the second axle is a rear axle. However, alternatively, it is also possible that the first axle is a rear axle and the second axle is a front axle.

[0019] The braking system that cooperates with the control device 16 also includes at least one first wheel inlet valve 18 placed in front of the first wheel brake cylinder 10, at least one first wheel outlet valve 20 placed behind the first wheel brake cylinder 10, at least one second wheel inlet valve 22 placed in front of the second wheel brake cylinder 12, and at least one second wheel outlet valve 24 placed behind the second wheel brake cylinder 12. For example, one first wheel inlet valve 18 and one first wheel outlet valve 20 can be connected to the first wheel brake cylinder 10 respectively, and one second wheel inlet valve and one second wheel outlet valve can be connected to the second wheel brake cylinder 12 respectively. Preferably, the brake circuits 14a and 14b are connected to the master brake cylinder 26, and a brake operating element 28, such as a brake pedal 28, can be placed in front of this. Optionally, a brake booster 30 and / or a brake fluid reservoir 32 can also be hydraulically connected to the master brake cylinder 26.

[0020] Optionally, one storage chamber 34, particularly a low-pressure storage chamber 34, can be placed behind each of at least one first wheel outlet valve 20 and / or second wheel outlet valve 24 of each brake circuit 14a and 14b. It may also be advantageous if the brake circuits 14a and 14b have at least one pump 36 that can be operated by a common pump motor 38 of the braking system in particular. As other optional components, the brake circuits 14a and 14b of the braking system in FIG. 2 further have one switching valve 40 and one high-pressure switching valve 42 respectively.

[0021] However, it should be noted that the form of the braking system shown in FIG. 2 should be interpreted as being merely illustrative. Instead, all regenerative braking systems in which the hydraulic system has at least components 10, 12, and 18 - 24 can be used together with the control device 16 described below. Furthermore, the availability of the control device 16 or the regenerative braking system cooperating therewith is not limited to a specific vehicle type / automobile type of a vehicle / automobile equipped with the braking system.

[0022] The control device 16 has an electronic device 16a that is designed and / or programmed to query or confirm whether at least part of the required vehicle deceleration can be caused by at least one electric motor (not shown) operating in the braking system or the regenerative mode of the vehicle. The at least one electric motor can be, for example, an electric drive motor of the vehicle. The required vehicle deceleration can be understood, for example, as the vehicle deceleration required by the vehicle driver by operating the brake operation element 28. In particular, at least one brake operation element sensor 44 that outputs a sensor signal 46 corresponding to the operation of the brake operation element 28, such as a rod displacement sensor and / or a differential displacement sensor, can be assembled to the braking system. Alternatively or additionally, the required vehicle deceleration can also be required by a corresponding brake request signal from an automatic speed control device (not shown) of the vehicle.

[0023] When the sensor signal 46 of the brake operation element sensor 44 and / or the brake request signal of the automatic speed control device is provided to the electronic device 16a, the electronic device 16a can be designed / programmed to control / operate the regeneration mode of at least one electric motor. In this case, the electronic device 16a (automatically) checks whether it is possible to cause the required vehicle deceleration only by at least one electric motor operating in the regeneration operation mode when controlling at least one electric motor. However, alternatively, the control of at least one electric motor can also be executed by a motor control device. In that case, the motor control device controls / operates the regeneration mode of at least one electric motor in consideration of at least one sensor signal 46 of at least one brake operation element sensor 44 and / or the brake request signal of the automatic speed control device. In this case, the electronic device 16a recognizes that it is not possible to cause the required vehicle deceleration only by at least one electric motor operating in the regeneration mode by querying / reading the information signal output to the electronic device 16a by the motor control device.

[0024] In some cases, that is, when the required vehicle deceleration can be caused only in part by at least one electric motor operating in the regenerative mode, the electronic device 16a is in its differential pressure control mode. The electronic device 16a in the differential pressure mode is designed and / or programmed to determine the target differential pressure between the first wheel brake cylinder 10 and the second wheel brake cylinder 12. The target differential pressure determinable by the electronic device 16a in the differential pressure control mode is defined as the difference between the first target brake pressure or the actual brake pressure and the second target brake pressure. The first target brake pressure can be understood as the pressure to be adjusted within the first wheel brake cylinder 10, which may be specified to the electronic device 16a or determined by the electronic device 16a. The first actual brake pressure, which can be used to specify the target differential pressure instead of the first target brake pressure, is the first actual brake pressure measured or estimated within the first wheel brake cylinder 10. For example, a pressure sensor 48 coupled to one of the brake circuits 14a and 14b can output a pressure sensor signal 50 corresponding to the first actual brake pressure to the electronic device 16a. The second target brake pressure is the pressure to be adjusted within the second wheel brake cylinder 12, which may also be specified to the electronic device 16a or determined by the electronic device 16a. For example, an information signal output to the electronic device 16a by the motor control device can include the first target brake pressure and / or the second target brake pressure. The advantageous possibilities for the electronic device 16a to determine the first target brake pressure and / or the second target brake pressure will be further described later.

[0025] The electronic device 16a in differential pressure control mode is further designed and / or programmed to output a current signal 52 to at least one second wheel inlet valve 22 taking into account the determined target differential pressure, whereby the at least one second wheel inlet valve 22 can be controlled / is controlled by the output current signal 52. Additionally, the electronic device 16a in differential pressure control mode is designed and / or programmed to determine the target current intensity of the current signal 52 taking into account the determined target differential pressure. For this purpose, the electronic device 16a in differential pressure control mode can select / selects the target current intensity or the output value of the target current intensity of the current signal 52 from a value range including at least three current intensity values taking into account the determined target differential pressure. Next, the electronic device 16a in differential pressure control mode outputs a current signal 52 having a (real) current intensity corresponding to the determined target current intensity to at least one second wheel inlet valve 22.

[0026] Based on the advantageous design / programming of the electronic device 16a described in the previous paragraph, the control device 16, or the regenerative braking system cooperating therewith, provides the advantages explained based on the subsequent figures. The electronic device 16a of the control device 16 can in particular be designed / programmed to execute the process / method steps described below. Therefore, for other advantageous characteristics of the control device 16 or the regenerative braking system cooperating therewith, reference is made to the following description.

[0027] Figures 3a and 3b show a coordinate system for explaining an embodiment of the operation method of a regenerative braking system of a vehicle. The abscissas of the coordinate systems in Figures 3a and 3b are each a time axis t.

[0028] The method described below is merely exemplarily carried out by the above-described regenerative braking system. However, it is noted that the feasibility of the method is not limited to such a brake system type. Instead, the method is applicable to (substantially) all brake system types having at least a first wheel brake cylinder 10 assigned to a first axle of the vehicle, a second wheel brake cylinder 12 assigned to a second axle of the vehicle, at least one first wheel inlet valve 18 upstream of the first wheel brake cylinder 10, at least one first wheel outlet valve 20 downstream of the first wheel brake cylinder 10, at least one second wheel inlet valve 22 upstream of the second wheel brake cylinder 12, and at least one second wheel outlet valve 24 downstream of the second wheel brake cylinder 12. Similarly, the feasibility of the method is not limited to a specific vehicle type / motor vehicle type of a vehicle / motor vehicle equipped with each brake system.

[0029] In a first braking process schematically shown in FIG. 3a, starting from time t0, a vehicle deceleration a unequal to zero of a vehicle equipped with the above-described regenerative braking system is required. The vehicle deceleration a unequal to zero can be required, for example, by the driver of the vehicle by operating the brake operating element 28 of the brake system or by the vehicle's automatic speed control device. As soon as a vehicle deceleration a unequal to zero is required, in the method described herein, it is checked whether the required vehicle deceleration a can be caused only in part by at least one electric motor of the brake system / vehicle operating in the regeneration mode Φ r Additionally, starting from time t0, the operating state Φ of at least one electric motor is switched from the non-active mode Φ 0 to the regeneration mode Φ r Here, in the first braking process described, since the required vehicle deceleration a is very small between times t0 and t1, this vehicle deceleration is in the regeneration mode Φ

[0030] r rIt can be caused only by at least one electric motor operating at. Therefore, in order to achieve the highest possible regeneration efficiency during the first braking process, between times t0 and t1, the first target braking pressure p to be adjusted within the first wheel brake cylinder 10 1target and the second target braking pressure p to be adjusted within the second wheel brake cylinder 12 2targetis (substantially) equal to zero or below the response pressure of each wheel brake cylinder 10 or 12. Further, between times t0 and t1, at least one first wheel inlet valve 18 upstream of the first wheel brake cylinder 10, at least one first wheel outlet valve 20 downstream of the first wheel brake cylinder 10, at least one second wheel inlet valve 22 upstream of the second wheel brake cylinder 12, and at least one second wheel outlet valve 24 downstream of the second wheel brake cylinder 12 prevent (substantially) an increase in the brake pressure within the first wheel brake cylinder 10 and the second wheel brake cylinder 12. Thus, the first brake pressure p1 (presumably) present within the first wheel brake cylinder 10 and the second brake pressure p2 (presumably) present within the second wheel brake cylinder 12 are controlled to be below the response pressure of each wheel brake cylinder 10 or 12. For this purpose, at least one first wheel outlet valve 20 downstream of the first wheel brake cylinder 10 and at least one second wheel outlet valve 24 downstream of the second wheel brake cylinder 12 can be switched to an open state between times t0 and t1, which is not shown in the coordinate system of FIG. 3a. At least one first wheel inlet valve 18 upstream of the first wheel brake cylinder 10 can also be switched to an open state between times t0 and t1. As can be recognized based on the coordinate system of FIG. 3a, at least one second wheel inlet valve 22 upstream of the second wheel brake cylinder 12 is controlled to an open state by the current signal 52 between times t0 and t1, and since at least one second wheel inlet valve 22 is designed as a normally non-energized open valve, the current intensity I of the current signal 52 is equal to zero between times t0 and t1.

[0031] In the first braking process shown by FIG. 3a, the required vehicle deceleration a becomes very high starting from time t1, and the vehicle deceleration a is set to the regeneration mode Φr can only be caused in part by at least one electric motor operating in Δp During the following time interval T, the differential pressure control (Δp control) described below is carried out in the first wheel brake cylinder 10 and the second wheel brake cylinder 12 of the braking system.

[0032] Time interval T Δp In the first sub-step of the differential pressure control carried out during the time interval T, the target differential pressure Δp between the first wheel brake cylinder 10 and the second wheel brake cylinder 12 target is determined. The target differential pressure Δp target To determine, the first target brake pressure p to be adjusted in the first wheel brake cylinder 10 1target and the second target brake pressure p to be adjusted in the second wheel brake cylinder 12 2target are such that when the target brake pressures p 1target and p 2target in the wheel brake cylinders 10 and 12 of the braking system are reliably adhered to, the required vehicle deceleration a is highly likely to be caused by at least one electric motor operating in the regeneration mode Φ r and the first brake pressure p1 present in the first wheel brake cylinder 10 and the second brake pressure p2 present in the second wheel brake cylinder 12 can be continuously determined.

[0033] Preferably, during the differential pressure control, the vehicle deceleration a is the motor brake torque applied to the vehicle by at least one electric motor operating in the regeneration mode Φ r and the first target brake pressure p that can be caused by the first wheel brake cylinder 10 1target is achievable in the first wheel brake cylinder 10 (by the corresponding first brake pressure p1 present in the first wheel brake cylinder 10), the second target brake pressure p to be adjusted in the second wheel brake cylinder 12 2targetis determined to be equal to zero. If the required vehicle deceleration a can be caused (with a high probability) by at least one electric motor operating in the regeneration mode Φ r and only the first wheel brake cylinder 10, the braking of the second axle of the vehicle by the second wheel brake cylinder 12 can be omitted. Otherwise, i.e., if the motor brake torque generated by at least one electric motor operating in the regeneration mode Φ r and the first wheel brake cylinder 10 are not sufficient to cause the required vehicle deceleration a, the first target brake pressure p 1target and the second target brake pressure p 2target can both be determined not to be equal to zero, and the second target brake pressure p 2target is usually specified to be below the first target brake pressure p 1target . In particular, in this case, the second target brake pressure p 2target can be determined taking into account the required vehicle deceleration a, the motor brake torque of at least one electric motor, and the first target brake pressure p 1target .

[0034] Subsequently, the difference between the first target brake pressure p 1target or the first actual brake pressure p 1 and the second target brake pressure p 2target is specified as the target differential pressure Δp target . Thus, the target differential pressure Δp target is defined by the following equation (Equation 1) or Equation (Equation 2). (Equation 1) Δp target =p 1target -p 2target (Equation 1) Δp target =p 1 -p 2target The first actual brake pressure p 1 can be understood as the dominant measured or estimated pressure value (with a high probability) within the first wheel brake cylinder 10.

[0035] In the next sub-step, the target current intensity of the current signal 52 output to at least one second wheel inlet valve 22 is determined. The determination of the target current intensity of the current signal 52 is made taking into account the previously determined target differential pressure Δp target into account. For this purpose, taking into account the determined target differential pressure Δp target the target current intensity of the current signal 52 or the output value of the target current intensity is selected from a value range including at least three current intensity values. This can also be referred to as "smooth Δp control" by continuous control of the target current intensity of the current signal 52 using the determined target differential pressure Δp target In the next sub-step, at least one second wheel inlet valve 22 is controlled by the current signal 52 output to at least one second wheel inlet valve 22, and the (actual) current intensity I of the output current signal 52 substantially corresponds to the determined target current intensity. Thus, the control of at least one second wheel inlet valve 22 is carried out taking into account the target differential pressure Δp

[0036] determined during the time interval T Δp in this differential pressure control described herein. In this way, a "smooth" control / switching of at least one second wheel inlet valve 22 is obtained, as shown by arrow 60 in the coordinate system of FIG. 3a. In the "continuous" pressure increase in the first wheel brake cylinder 10 marked by arrow 62 in the coordinate system of FIG. 3a, no "waveform" pressure increase as in the prior art described above occurs. Arrow 64 in the coordinate system of FIG. 3a further shows that only a relatively small deviation of the first actual brake pressure p target in the first wheel brake cylinder 10 from the first target brake pressure p 1target to be adjusted in the first wheel brake cylinder 10 occurs. 1 In particular, the target current intensity of the current signal 52 or the output value of the target current intensity is the determined target differential pressure Δp

[0037] into account. targetIt is determined according to a specified continuous function having a value range including at least three current intensity values, depending on this. This can be easily implemented. In particular, the continuous function has a value range including at least four current intensity values. The value range of the continuous function can, in particular, include more than four current intensity values. The determined target differential pressure Δp target The value of the continuous function determined depending on target is proportional to the target differential pressure Δp target It can also be proportional to target . Alternatively, the target current intensity or the output value of the target current intensity of the current signal 52 can be determined according to a specified step function having at least three steps, preferably at least four steps, in particular more than four steps, depending on the determined target differential pressure Δp target

[0038] The output value of the target current intensity can be understood as the value on which the target current intensity is then determined taking this into account. For example, in the differential pressure control executed during the time interval T Δp at least one further different quantity can be determined, and this quantity is additionally taken into account together when determining the target current intensity taking the output value into account. In particular, during the specified comparison time interval, the deviation of at least one measured or estimated first actual brake pressure p 1target from the first target brake pressure p 1 to be adjusted into the first wheel brake cylinder 10, respectively, simultaneously, can be determined. Thereafter, taking the determined deviation into account, the offset value of the target current intensity of the current signal 52 can be determined. In this case, the target current intensity of the current signal 52 can be determined as the sum of the output value of the target current intensity and the offset value. By determining the target current intensity described herein, the component tolerances and / or degradation phenomena of the brake system can be advantageously compensated for.

[0039] As an optional development form, during the differential pressure control executed in the time interval T Δp at least one measured or estimated first actual brake pressure p 1 in the first wheel brake cylinder 10is, at the same time, the first target brake pressure p to be adjusted into the first wheel brake cylinder 10 1target and a period that differs by at least one specified minimum pressure deviation can be (continuously) determined. If the specified period exceeds the specified time threshold, preferably, during the specified or determined valve closing time, the target current intensity of the current signal 52 is determined to be switched to the valve closed state during the valve closing time specified or determined by the current signal 52 output to at least one second wheel inlet valve 22. In this way, the first target brake pressure p to be adjusted into the first wheel brake cylinder 10 at the same time 1target from the first actual brake pressure p in the first wheel brake cylinder 10 1 a relatively large deviation can be prevented from occurring over a time exceeding the time threshold.

[0040] Preferably, at the beginning of the differential pressure control executed during the time interval T Δp the target differential pressure Δp 1target is determined as the difference between the first target brake pressure p to be adjusted into the specified or determined first wheel brake cylinder 10 2target and the second target brake pressure p to be adjusted into the specified or determined second wheel brake cylinder 12 target by the formula (Formula 1), that is.

[0041] In the first braking process schematically shown by FIG. 3a, during the time between t1 and t2, the required vehicle deceleration a can be generated by at least one electric motor operating in the regeneration mode Φ r and the first wheel brake cylinder 10 assigned to the first axle of the vehicle. Therefore, the first wheel outlet valve 20 disposed behind the first wheel brake cylinder 10 is at time t 1While the first wheel outlet valve 20 is held in the closed state from [time point], the second wheel outlet valve 24, which is disposed downstream of the second wheel brake cylinder 12, is continuously controlled to be in the open state between times t1 and t2. In that case, the differential pressure control is carried out as described above between times t1 and t2.

[0042] From time t2, the required vehicle deceleration a can be achieved solely by at least one electric motor operating in the regeneration mode Φ r and the first wheel brake cylinder 10 and the second wheel brake cylinder 12 assigned to the second axle of the vehicle. Accordingly, the second wheel outlet valve 24, which is disposed downstream of the second wheel brake cylinder 12, is held in the closed state from time t2 (the same as the first wheel outlet valve 20 disposed downstream of the first wheel brake cylinder 10). Additionally, the brake fluid can also be pumped from at least one reservoir 34 disposed downstream of the first wheel outlet valve 20 and the second wheel outlet valve 24 into the brake system by a non-zero pump speed n of at least one pump 36 of the brake system. However, unlike the prior art described above, the pressure increase in the second wheel brake cylinder 12 generated from time t2 hardly causes a pressure decrease in the first wheel brake cylinder 10.

[0043] Also in the second braking process shown by the coordinate system of FIG. 3b, a non-zero vehicle deceleration a is required from time t0, and this vehicle deceleration can still be caused by at least one electric motor operating in the regeneration mode Φ r between times t0 and t1. However, compared to the first braking process, a much faster braking of the vehicle is required. Also in the second braking process, the required non-zero vehicle deceleration a is achieved between times t0 and t1 by at least one electric motor operating in the regeneration mode Φ r and the first wheel brake cylinder 10 of the first axle only, and from time t2, by the regeneration mode Φ rAt least one electric motor operating thereby, and it can be achieved only by the first wheel brake cylinder 10 and the second wheel brake cylinder 12 of the second axle. The first target brake pressure p to be adjusted in the first wheel brake cylinder 10 1target and the second target brake pressure p to be adjusted in the second wheel brake cylinder 12 2target are determined correspondingly.

[0044] However, during differential pressure control, if it is confirmed that the first actual brake pressure p in the first wheel brake cylinder 10 measured or estimated 1 is at least one specified limit deviation less than the first target brake pressure p to be adjusted in the first wheel brake cylinder 10 at the same time 1target Preferably, during the specified or determined transition time, the target differential pressure Δp target is determined by Equation (Equation 2), that is, the first actual brake pressure p in the first wheel brake cylinder 10 measured or estimated 1 and the second target brake pressure p to be adjusted in the second wheel brake cylinder 12 2target The difference between them. Therefore, it is possible to reliably prevent a deviation exceeding the limit deviation of the second actual brake pressure p in the second wheel brake cylinder 12 from the second target brake pressure p to be adjusted in the second wheel brake cylinder 12 at the same time 2target from occurring. 2

[0045] The first actual brake pressure p existing in the first wheel brake cylinder 10 1 and the second actual brake pressure p existing in the second wheel brake cylinder 12 2 To adjust, during the time interval T Δp The newly target differential pressure Δp target Is adjusted / regulated by the differential pressure control described above. For this purpose, also in the second braking process of Figure 3b, the determined target differential pressure Δp targetTaking this into account, the target current intensity of the current signal 52 or the output value of the target current intensity is selected from a value range including at least three current intensity values. The arrow 64 in the coordinate system of FIG. 3b indicates that the first target brake pressure p to be adjusted simultaneously in the first wheel brake cylinder 10 1target from the first actual brake pressure p in the first wheel brake cylinder 10 1 results in only a relatively small deviation. Therefore, different from the above-described prior art, during the differential pressure control executed in the time interval T Δp there is no occurrence of the "soft" brake operating element 28.

[0046] It should be mentioned that the differential pressure control executed in two braking processes omits the exchange between the overflow of at least one second wheel inlet valve 22 and the underflow of at least one second wheel inlet valve 22. Considering the determined target differential pressure Δp target it is not necessary to determine the target current intensity of the current signal 52 or the output value of the target current intensity from a value range including at least three current intensity values.

Explanation of Signs

[0047] 10 First wheel brake cylinder 12 Second wheel brake cylinder 14a, 14b Brake circuit 16 Control device 16a Electronic device 18 First wheel inlet valve 20 First wheel outlet valve 22 Second wheel inlet valve 24 Second wheel outlet valve 26 Master brake cylinder 28 Brake operating element, brake pedal 30 Brake booster 32 Brake fluid reservoir 34 Storage chamber, low-pressure storage chamber 36 Pump 38 Pump motor 40 Changeover valve 42 High-pressure changeover valve 44 Brake operation element sensor 46 Sensor signal 48 Pressure sensor 50 Pressure sensor signal 52 Current signal 60 Arrow 62 Arrow 64 Arrow

Claims

1. A control device (16) for a regenerative braking system of a vehicle, Whether the required vehicle deceleration (a) can be caused only in part by a braking system operating in a regeneration mode (Φ ｒ ), or by at least one electric motor of the vehicle, is queried or checked, and is designed and / or programmed to include an electronic device (16a) that is in a differential pressure control mode, in which differential pressure control mode a target differential pressure between a first wheel brake cylinder (10) of the braking system assigned to a first axle of the vehicle and a second wheel brake cylinder (12) of the braking system assigned to a second axle of the vehicle is - The first target brake pressure (p to be adjusted within the specified or determined first wheel brake cylinder (10) １ｔａｒｇｅｔ ), or the first actual brake pressure (p within the first wheel brake cylinder (10) measured or estimated １ ), and - The second target brake pressure (p to be adjusted within the specified or determined second wheel brake cylinder (12) ２ｔａｒｇｅｔ ) and determinable as a difference therebetween, in the control device, a current signal (52) can be output to at least one wheel inlet valve (22) preposed to the second wheel brake cylinder (12) of the braking system in consideration of the determined target differential pressure, whereby the at least one wheel inlet valve (22) can be controlled by the output current signal (52), the electronic device (16a) in the differential pressure control mode is additionally designed and / or programmed such that the electronic device (16a) can select a target current intensity of the current signal (52) or an output value of the target current intensity from a value range including at least three current intensity values in consideration of the determined target differential pressure, so as to determine the target current intensity of the current signal (52) in consideration of the determined target differential pressure. The control device is characterized by this.

2. The control device (16) according to claim 1, wherein the electronic device (16a) in the differential pressure control mode is designed and / or programmed to determine the target current intensity of the current signal (52) or the output value of the target current intensity according to a specified continuous function having the value range including the at least three current intensity values depending on the determined target differential pressure.

3. After the start of the differential pressure control mode, the electronic device (16a) additionally adjusts the first target brake pressure (p １ｔａｒｇｅｔ ), respectively, simultaneously into the first wheel brake cylinder (10). During a specified comparison time interval from the first wheel brake cylinder (10), the at least one first actual brake pressure (p １ ) is considered to determine an offset value of the target current intensity of the current signal (52), and the target current intensity of the current signal (52) is determined as the sum of the output value of the target current intensity and the offset value. The control device (16) according to claim 1 or 2, which is designed and / or programmed to do so.

4. After the start of the differential pressure control mode, the electronic device (16a) additionally determines, for at least one measured or estimated first actual brake pressure (p １ ) in the first wheel brake cylinder (10), a period during which it differs from a first target brake pressure (p １ｔａｒｇｅｔ ) to be adjusted into the first wheel brake cylinder (10) simultaneously by at least one specified minimum pressure deviation, and if the determined period exceeds a specified time threshold, determines the target current intensity of the current signal (52) for a specified or determined valve closing time, such that the at least one wheel inlet valve (22) is switched to a closed state during the valve closing time specified or determined by the current signal (52) output to the wheel inlet valve. The control device (16) according to any one of claims 1 to 3, which is designed and / or programmed as such.

5. The electronic device (16a) is designed and / or programmed to determine the target differential pressure as the difference between the first target brake pressure (p １ｔａｒｇｅｔ ), which is to be adjusted in the specified or determined first wheel brake cylinder (10), and the second target brake pressure (p ２ｔａｒｇｅｔ ), which is to be adjusted in the specified or determined second wheel brake cylinder (12). However, if the measured or estimated first actual brake pressure (p １ ) in the first wheel brake cylinder (10) is less than the first target brake pressure (p １ｔａｒｇｅｔ ) to be adjusted in the first wheel brake cylinder (10) by at least one specified limit deviation, the electronic device (16a) determines the target differential pressure as the difference between the measured or estimated first actual brake pressure (p １ ) in the first wheel brake cylinder (10) and the second target brake pressure (p ２ｔａｒｇｅｔ ) to be adjusted in the second wheel brake cylinder (12) during a specified transition time. The control device (16) according to any one of claims 1 to 4.

6. A regenerative braking system of a vehicle, comprising the control device (16) according to any one of claims 1 to 5, a first wheel brake cylinder (10) assigned to a first axle of the vehicle, a second wheel brake cylinder (12) assigned to a second axle of the vehicle, and at least one wheel inlet valve (22) preposed to the second wheel brake cylinder (12).

7. A method for operating a regenerative braking system of a vehicle, Whether at least part of the vehicle deceleration (a) required by the driver of the vehicle and / or the automatic speed control device of the vehicle can be caused by the braking system operating in the regeneration mode (Φ ｒ ) or at least one electric motor of the vehicle is checked. When it is possible to cause only part of the vehicle deceleration (a) by means of the at least one electric motor, the method includes the step of performing differential pressure control of the wheel brake cylinders (10, 12) of the brake system, and the step of performing differential pressure control comprises a sub-step of determining a target differential pressure between a first wheel brake cylinder (10) of the brake system assigned to a first axle of the vehicle and a second wheel brake cylinder (12) of the brake system assigned to a second axle of the vehicle, wherein - The first target brake pressure (p １ｔａｒｇｅｔ ) to be adjusted within the specified or determined first wheel brake cylinder (10), or the first actual brake pressure (p １ ) within the measured or estimated first wheel brake cylinder (10), and - The second target brake pressure (p ２ｔａｒｇｅｔ ) to be adjusted within the specified or determined second wheel brake cylinder (12) the difference therebetween is determined as the target differential pressure, the sub-step; a sub-step of controlling at least one wheel inlet valve (22) upstream of the second wheel brake cylinder (12) of the brake system by means of a current signal (52) output to the at least one wheel inlet valve (22) taking into account the determined target differential pressure; in a method. A method, characterized by a sub-step of determining the target current intensity of the current signal (52) taking into account the determined target differential pressure, by being able to select the target current intensity of the current signal (52) or an output value of the target current intensity from a value range including at least three current intensity values taking into account the determined target differential pressure. Claim 8 The method according to claim 7, wherein the target current intensity of the current signal (52) or the output value of the target current intensity is determined according to a specified continuous function having the value range including the at least three current intensity values, depending on the determined target differential pressure. Claim 9 During differential pressure control, the first target brake pressure (p １ｔａｒｇｅｔ ), to be adjusted simultaneously into the first wheel brake cylinder (10) respectively, during a specified comparison time interval from １ ), the offset value of the target current of the current signal (52) is determined taking into account each deviation of the at least one first actual brake pressure (p ), and the target current intensity of the current signal (52) is determined as the sum of the output value of the target current intensity and the offset value, the method according to claim 7 or 8. Claim 10 During said differential pressure control, said at least one measured or estimated first actual brake pressure (p １ ) in said first wheel brake cylinder (10) is simultaneously each time different from said first target brake pressure (p １ｔａｒｇｅｔ ) to be adjusted in said first wheel brake cylinder (10) by at least one specified minimum pressure deviation, and if a period during which the difference is greater than a specified time threshold is identified, then during a specified or determined valve closing time, the target current intensity of said current signal (52) is determined such that said at least one wheel inlet valve (22) is switched to a closed valve state during said specified or determined valve closing time by said current signal (52) output to said wheel inlet valve, the method according to any one of claims 7 to 9. Claim 11 At the beginning of the differential pressure control mode, a first target brake pressure (p １ｔａｒｇｅｔ ), which is to be adjusted in the specified or determined first wheel brake cylinder (10), and a second target brake pressure (p ２ｔａｒｇｅｔ ), which is to be adjusted in the specified or determined second wheel brake cylinder (12), the target differential pressure is determined as the difference therebetween. However, when the measured or estimated first actual brake pressure (p １ ) in the first wheel brake cylinder (10) is less than the first target brake pressure (p １ｔａｒｇｅｔ ) to be adjusted in the first wheel brake cylinder (10) simultaneously by at least one specified limit deviation, during the specified or determined transition time, the target differential pressure is determined as the difference between the measured or estimated first actual brake pressure (p １ ) in the first wheel brake cylinder (10) and the second target brake pressure (p ２ｔａｒｇｅｔ ) to be adjusted in the second wheel brake cylinder (12). The method according to any one of claims 7 to 10. Claim 12 During the differential pressure control, when the vehicle deceleration (a) is in the regeneration mode (Φ ｒ ), the motor braking torque applied to the vehicle by the at least one electric motor operating in this mode, and the first target braking pressure (p １ｔａｒｇｅｔ ) that can be generated by the first wheel brake cylinder (10) is achievable within the first wheel brake cylinder (10), the second target braking pressure (p ２ｔａｒｇｅｔ ) to be adjusted within the second wheel brake cylinder (12) is determined to be equal to zero; otherwise, the second target braking pressure (p ２ｔａｒｇｅｔ ) is determined taking into account the vehicle deceleration (a), the motor braking torque, and the first target braking pressure (p １ｔａｒｇｅｔ ). The method according to any one of claims 7 to 11.

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