Control method for a hydraulic system with a pump and valves for supplying multiple consumers as well as a cooling and / or lubrication device; and hydraulic system

Abstract

Method for controlling a hydraulic system (1) for an actuating device and a cooling and / or lubrication device of a motor vehicle, wherein the hydraulic system (1) comprises a pump (2), several actuating valves (3a, 3b, 3c), which actuating valves (3a, 3b, 3c) are each arranged between a system rail (5) connected to a pump outlet (4) and a hydraulic consumer (6a, 6b, 6c), and an auxiliary valve (7), which auxiliary valve (7) is arranged between the pump outlet (4) and a cooling and / or lubricant supply line (8), wherein the pump (2) is switched between normal operation and extended operation depending on the existing total power demand of the hydraulic consumers (6a, 6b, 6c), wherein in normal operation, in which the pump (2) is permanently driven, an existing system pressure in the system rail (5) is determined at regular intervals and a target pressure of the system rail (5) is calculated, and an upper pressure threshold and a lower pressure threshold are determined based on the target pressure, wherein the auxiliary valve (7) is closed when the system pressure is below the lower pressure threshold, and the auxiliary valve (7) is open when the system pressure is above the upper pressure threshold, and wherein in the extended operation the pump (2) is permanently driven, the auxiliary valve (7) is permanently closed and each of the actuating valves (3a, 3b, 3c) designed as pressure regulating valves is operated at least temporarily depending on an individual power requirement of the respective hydraulic consumer (6a, 6b, 6c) as soon as the system pressure reaches or exceeds a threshold value.

Description

[0001] The invention relates to a method for controlling a hydraulic system for an actuating device and a cooling and / or lubricating device of a motor vehicle, such as a car, truck, bus, or other commercial vehicle. The actuating device is preferably a clutch actuating device that actuates a clutch of a drive train of the motor vehicle. The cooling and / or lubricating device is preferably a hydraulic fluid distribution device coupled to a transmission, which serves to cool and lubricate the components of the transmission. Furthermore, the invention relates to a hydraulic system designed to carry out this method.

[0002] EP 1 451 493 B1 describes a method for controlling a pressure supply device in a hydraulic circuit.

[0003] EP 2 557 336 B1 describes a transmission hydraulic system of a dual-clutch transmission and a control method with hydraulic valves for a dual-clutch transmission.

[0004] Generic methods for actuating at least one clutch are known from the prior art, for example, from DE 10 2014 208 182 A1. It is also known to supplement hydraulic systems in such a way that they can be used to supply a cooling and / or lubricating device. The applicant's corresponding prior art was filed with the German Patent and Trademark Office with the German patent application under the file number DE 10 2018 130 700 A1.

[0005] Further state of the art is related to Fig. 4. A power pack system 1', which can primarily be seen here, has a pressure accumulator which is maintained at a relatively high pressure level during operation via a hysteresis control. The pump can be controlled relatively easily using a so-called two-point controller, and the control of the individual valves can be decoupled from the pump control. However, this system has the disadvantage that, due to the presence of the pressure accumulator, a relatively high pressure is provided even in those operating states in which this high pressure is not required, since the individual hydraulic consumers K0, K1, K2 would manage with significantly lower pressure. As a result, a relatively large portion of the energy previously fed into the pressure accumulator is lost again at a valve edge.

[0006] While hydraulic systems without accumulators are also available in principle, these systems often have the disadvantage of being relatively complex. Furthermore, the pump control must be coordinated as precisely as possible with the valve control to avoid any drivability restrictions.

[0007] It is therefore the object of the present invention to eliminate the disadvantages known from the prior art and to provide a control strategy that functions as simply and robustly as possible for the simplest possible construction of a hydraulic system.

[0008] This is achieved according to the invention by the subject matter of claim 1. Accordingly, a method for controlling a hydraulic system for an actuating device and a cooling and / or lubricating device of a motor vehicle is claimed, wherein the hydraulic system comprises a pump, a plurality of actuating valves, each of which is arranged between a system rail connected to a pump outlet and a hydraulic consumer, and an additional valve, which is arranged between the pump outlet and a cooling and / or lubricant supply line. The pump is switched between normal operation and extended operation depending on an existing total power requirement of the hydraulic consumers (determined at regular intervals).In normal operation, in which the pump is continuously driven, an existing system pressure in the system rail is determined at regular intervals and a target pressure for the system rail is calculated; an upper pressure threshold and a lower pressure threshold are also defined based on the target pressure, with the additional valve being opened when the system pressure is above the upper pressure threshold and the additional valve being closed when the system pressure is below the lower pressure threshold. In extended operation, the pump is continuously driven, the additional valve is permanently closed and each of the actuating valves designed as pressure control valves is operated at least temporarily depending on an individual power requirement of the respective hydraulic consumer as soon as the system pressure reaches or exceeds a threshold value.

[0009] This allows a hydraulic system to eliminate the need for a pressure accumulator and to control the pump and valves as independently as possible, for example, to effectively perform clutch actuation and hydraulic supply to the cooling and lubrication system. This significantly simplifies the control of the hydraulic system.

[0010] Further advantageous embodiments are claimed in the subclaims and explained in more detail below.

[0011] Accordingly, it is also advantageous if, at least during normal operation, the control of the actuating valves is (completely) decoupled from the control of the pump.

[0012] It is also advantageous if the electric motor driving the pump is subjected to a maximum available (electrical) system voltage both in the initial drive state of normal operation, in which the auxiliary valve is closed, and in the extended mode. This keeps the control process as simple as possible.

[0013] If a different, preferably lower, or the same electrical voltage is applied to the electric motor driving the pump in the first drive state of normal operation in which the additional valve is closed as in a second drive state of normal operation in which the additional valve is open, the hydraulic system is operated particularly efficiently.

[0014] To implement the expansion operation, it is also useful if a pressure relief valve is integrated / arranged in the system rail.

[0015] It is also advantageous if a check valve is arranged between the pump outlet and the system rail, blocking a backflow of hydraulic fluid from the system rail to the pump, wherein a branch leading to the additional valve is arranged between the pump outlet and the check valve.

[0016] Furthermore, it is advisable if the total power requirement (of all hydraulic consumers) that determines switching between normal operation and extended operation corresponds to the total flow rate requirement of all consumers. Extended operation is activated when the total flow rate requirement is above an upper flow rate threshold, and normal operation is activated when the total flow rate requirement is below a lower flow rate threshold. This results in even easier control of the hydraulic system.

[0017] In this regard, it is again advantageous if the upper volume flow threshold and / or the lower volume flow threshold are formed by a fixed constant or a temperature-dependent and / or system pressure-dependent variable. This keeps the control process particularly simple.

[0018] It is also advantageous if the total volume flow requirement is calculated based on the sum of a first partial volume flow requirement determined by a first hydraulic consumer and a second partial volume flow requirement determined by at least one further second hydraulic consumer, wherein the respective partial volume flow requirement is determined based on a pressure-volume function stored in software. In further embodiments, more than two hydraulic consumers, each with a partial volume flow requirement, are present. Accordingly, the total volume flow requirement is calculated based on the sum of individual partial volume flow requirements / partial volume flow requirement values ​​of more than two hydraulic consumers.

[0019] It is also advantageous if the target pressure is a maximum value from the group of target pressures required for each individual consumer. This makes it easy to determine the target pressure.

[0020] For the implementation of normal operation, it is also expedient if the upper pressure threshold is calculated using a first surcharge factor on the basis of the target pressure and / or the lower pressure threshold is calculated using a second surcharge factor on the basis of the target pressure, wherein the at least one surcharge factor represents a fixed constant or a temperature-dependent and / or system pressure-dependent variable.

[0021] Furthermore, the invention relates to a hydraulic system, wherein the hydraulic system is designed to carry out a method according to the invention according to at least one of the previously described embodiments.

[0022] In other words, the invention proposes a control method for a hydraulic arrangement (hydraulic system) with a pump and several valves. The basic idea is to identify an "event" with a high power requirement and to respond to it in a targeted manner. Based on this basic principle, there are two operating modes: normal operation and event intervention (extension operation). In normal operation, the pump is controlled by means of hysteresis control so that the system pressure is constantly maintained at a sufficient level. For this purpose, in a first sub-step a), the target pressure of the system rail is calculated. In a second sub-step b), an upper threshold and a lower threshold are calculated from the target pressure.In a third sub-step c), the pump is driven in a first drive state (valve open) when the system pressure is above the upper threshold, and in a second drive state (valve closed) when the system pressure is below the lower threshold. In normal operation, the valve control is decoupled from the pump control. Each control is based only on the target demand of individual consumers, e.g. the target pressure of a clutch. In "event intervention" mode, the pump is continuously driven. However, the valve control initially remains unchanged. This means that the valve current or the applied valve voltage remains at the level it was at when the "event intervention" mode was activated. Only after the system pressure has reached a threshold value are these valves controlled depending on the target demand of individual consumers.

[0023] The invention will now be explained in more detail below with reference to figures.

[0024] They show: Fig. 1 a representation of a state machine to illustrate a control strategy of a hydraulic system according to the invention, Fig. 2 a schematic diagram of a hydraulic system according to the invention according to a first embodiment, which is operated with the control strategy according to Fig. 1 is controllable, Fig. 3 a schematic diagram of a hydraulic system according to the invention according to a second embodiment, which also uses the control strategy according to Fig. 1 and is equipped with a pressure relief valve compared to the first embodiment, and Fig. 4 a schematic diagram of a hydraulic system with a pressure accumulator designed according to the state of the art.

[0025] The figures are merely schematic in nature and serve solely to understand the invention.

[0026] A hydraulic system 1 according to the invention, which is designed to carry out a method according to the invention, has, according to a first embodiment, the Fig. 2. In comparison to a hydraulic system 1' constructed according to the state of the art according to Fig. 4, the following differences exist: In contrast to the hydraulic system 1' of the prior art, the hydraulic system 1 of the inventive embodiment does not comprise a pressure accumulator. Several branches 10a, 10b, 10c branch off from the system rail 5, each of which can be connected to a hydraulic consumer 6a, 6b, 6c (K0, K1, K2) via an actuating valve 3a, 3b, 3c. The actuating valves 3a to 3c assigned to the individual consumers 6a to 6c are each implemented as pressure control valves / pressure reducers. Also, in a typical manner, as in connection with another hydraulic system 1 according to the invention according to a second embodiment in Fig. 3, a pressure relief valve 11, not shown here for the sake of clarity, is installed in a system rail 5 connected to an output 4 of a pump 2.

[0027] As continued in Fig. 2, the hydraulic system 1 according to the invention is equipped with a pump 2 driven by an electric motor 13. The pump 2 is thus operated / controlled via the electric motor 13. The pump 2 is connected with its inlet 14 to a tank 9. The pump 2 is connected with its outlet 4 directly to the system rail 5. In this embodiment, three branches 10a to 10c run from the system rail 5 to the actuating valves 3a to 3c. The respective branch 10a to 10c is coupled to a hydraulic consumer 6a to 6c depending on the position of the actuating valve 3a to 3c. Accordingly, in this embodiment, a first branch 10a branching off from the system rail 5 can be coupled to a first hydraulic consumer 6a via a first actuating valve 3a.A further second branch 10b, arranged along the system rail 5 offset from the first branch 10a, can be coupled to a second consumer 6b via a further second actuation valve 3b. A third branch 10c, which in turn is arranged offset from the two first and second branches 10a and 10b, can be coupled to a third consumer 6c via a third actuation valve 3c. According to further embodiments, however, it is also possible in principle to provide fewer than three consumers 6a, 6b, 6c, preferably only two consumers or more than three consumers. The consumers 6a, 6b, 6c are each part of an actuation device of a clutch (K0, K1, K2) of a drive train, for example in the form of a pressure cylinder.

[0028] In addition, a check valve 12 is installed between the outlet 4 of the pump 2 and the system rail 5. The check valve 12 is typically installed in such a way that it blocks a backflow of hydraulic fluid from the system rail 5 to the pump 2. A further fourth branch 10d is directly (permanently) connected to the outlet 4 on a side of the check valve 12 facing the pump 2. Via the fourth branch 10d, the outlet is coupled to an additional valve 7 (also referred to as a cooling valve), wherein a valve outlet 14 of the additional valve 7 is further connected to a cooling and / or lubricant supply line 8. The cooling and / or lubricant supply line 8 is typically further connected to a cooling and lubrication device of a transmission.

[0029] This in conjunction with Fig. The hydraulic system 1 according to the invention shown in Figure 3 according to the second embodiment differs from the first embodiment only by the provision of the pressure relief valve 11, which is connected to the system rail 5. The remaining structure of the hydraulic system 1 according to Fig. 3 corresponds to the hydraulic system 1 according to Fig. 2.

[0030] According to the invention, a method for controlling the hydraulic system 1 according to the invention is implemented, wherein the method also works particularly well in conjunction with Fig. 1. The process is compatible with both the hydraulic system according to Fig. 2 as well as with the hydraulic system according to Fig. 3 feasible.

[0031] The pump 2 can be switched between its normal operation and its extended operation depending on an existing total power requirement (total volume flow requirement Q_demand) of the hydraulic consumers 6a, 6b, 6c.

[0032] Normal operation refers to the operation of pump 2 in which an existing system pressure p_sys in system rail 5 is determined / measured at regular intervals and a target pressure p_sys_soll for system rail 5 is calculated. The target pressure p_sys_soll is the value that represents the highest pressure value that can be set in the system. The target pressure p_sys_soll is thus a maximum value from the group of consumer target pressures required at the respective individual consumer 6a, 6b, 6c. Based on the target pressure p_sys_soll, an upper pressure threshold p_h and a lower pressure threshold p_I are defined. The upper pressure threshold p_h and the lower pressure threshold p_I are calculated using a surcharge factor that represents a fixed constant or a temperature-dependent variable.The pump 2 is driven in a second drive state when the system pressure p_sys is below the lower pressure threshold p_I and in a first drive state when the system pressure p_sys is above the upper pressure threshold p_h. Thus, in normal operation, a certain pressure level in the system rail 5 (between the lower pressure threshold p_I and the upper pressure threshold p_h) is always kept constant. The pump 2 is switched between its two drive states in order to maintain this pressure level. An electrical voltage U_b applied to the electric motor 13 driving the pump 2 in the first drive state of normal operation is preferably lower than an electrical voltage U_cool applied in a second drive state of normal operation in which the additional valve 7 is open.

[0033] According to the invention, an additional extended mode of operation of the pump 2 is implemented. This extended mode is activated when the total power requirement Q_requirement exceeds a specific power requirement. The total volume flow requirement Q_requirement of all consumers 6a, 6b is determined as the total power requirement. The total volume flow requirement Q_requirement is a sum of partial volume flow requirements (V_1_requirement, V_2_requirement, ...) of all individual hydraulic consumers 6a, 6b, 6c at the respective point in time. The respective partial volume flow requirement is determined using a pressure-volume function stored in software. Accordingly, extended mode is activated / normal mode is deactivated when the total volume flow requirement Q_requirement is above an upper volume flow threshold value Q_h and normal mode is activated / extended mode is deactivated when the total volume flow requirement Q_requirement is below a lower volume flow threshold value Q_I.The upper volume flow threshold Q_h and the lower volume flow threshold Q_I are each calculated / derived either by a fixed constant or a temperature-dependent and system pressure-dependent variable.

[0034] In extended mode, pump 2 is driven continuously, just as in normal mode. In extended mode, pump 2 is driven with the same electrical voltage / system voltage U_b as in the first drive state of normal operation. Each of the actuating valves 3a, 3b, 3c designed as a pressure control valve is operated in extended mode, at least temporarily, depending on an individual power requirement of the respective hydraulic consumer 6a, 6b, 6c as soon as the system pressure p_sys reaches or exceeds a threshold value p_grenz. In other words, this means that the respective actuating valve 3a, 3b, 3c is specifically used to reduce the pressure when the system pressure p_sys in the system rail 5 reaches or exceeds the threshold value p_grenz.

[0035] The actuation valves 3a, 3b, 3c are typically controlled completely decoupled / independently from the control of the pump 2 / the electric motor 13.

[0036] Combined with Fig. Figure 1 shows a typical calculation and determination of the respective values ​​that determine the switching. In this figure, a motor voltage is denoted by U_motor. The system voltage is denoted by U_b, and the voltage of the second drive state, which is lower than the system voltage U_b, is denoted by U_cool. A valve current controlling the respective actuating valve 3a, 3b, 3c is denoted by I_valve_1 (first actuating valve 3a), I_valve_2 (second actuating valve 3b). Since the respective actuating valve 3a, 3b is implemented as a pressure control valve, the valve current I_valve_1, I_valve_2 is controlled according to a function based on the corresponding target pressure to be implemented at the actuating valve 3a, 3b (f(p_1_setpoint); f(p_2_setpoint)). When the limit pressure value / threshold p_grenz is reached, the control of the actuating valves 3a, 3b is switched accordingly in extended mode. This results in the following mathematical relationship: Since conventional pressure control valves are used, there is usually a mathematical relationship between the set pressure (p_1_set; p_2_set) downstream of the actuating valve and the valve current (I_valve_1; I_valve_2). This means that the pressure downstream of the actuating valve 3a, 3b, 3c is controlled by the valve current, i.e., I_valve=f(p_1_set) or p_1_set=f-1(I_valve).

[0037] To improve the control strategy used in Fig. 1, the following signal values ​​must be determined for each time step i: 1. For the pressure interfaces, p_h and p_I of the pressure hysteresis control must be determined mathematically as follows: p_sys_soll=max(p_1_soll, p_2_soll,…) p_h=p_sys_soll+dp_h p_l=p_sys_soll+dp_l

[0038] dp_h and dp_I are stored constants or are derived from a function / map dependent on operating temperature and p_sys_soll. The following applies: dp_h>dp_l>0 and consequently p_h>p_l>p_sys_soll

[0039] In order to know whether an event intervention, i.e. the activation of the expansion mode, is necessary, Q_demand, Q_h and Q_I are determined mathematically: Q_need+(V_1_need+V_2_need+…) / (ti−ti−1) with V_1_bedarf=max[(V_1(p_1_solli)−V_1(p_1_solli−1)),0] V_2_bedarf=max[(V_2(p_2_solli)−V_2(p_2_solli−1)),0]

[0040] In a further preferred embodiment of the invention, Q_bedarf is also mathematically determined as follows: Q_need=(V_1_need+V_2_need+…) / (ti−ti−1)

[0041] With V_1_bedarf=max[(V_1(p_1_solli)−V_1(p_1_isti)),0] V_2_bedarf=max[(V_2(p_2_solli)−V_2(p_2_isti)),0]

[0042] The functions V_1 and V_2 are pressure-volume characteristic curves stored in software. Q_h and Q_I are constants or from a function / characteristic map dependent on operating temperature and p_sys_soll. p_1_solli is a target pressure at the first hydraulic consumer 6a at a time i; p_2_solli is a target pressure at the second hydraulic consumer 6b at the time i. Accordingly, p_1_solli-1 is a target pressure at the first hydraulic consumer 6a at a time i-1 and p_2_solli-1 is a target pressure at the second hydraulic consumer 6b at the time i-1. p_1_isti is an actually existing (actual) pressure at the first hydraulic consumer 6a at the time i and p_2_isti is an actually existing (actual) pressure at the second hydraulic consumer 6b at the time i.

[0043] The applied motor voltage U_b is preferably a constant, but in other versions it is also calculated based on a function / map of operating temperature and p_sys_soll. The applied motor voltage U_b can also be derived directly from a pressure control system.

[0044] The auxiliary valve 7 is also designed such that it assumes the open position in its rest position, i.e., in its de-energized state (I_cooling_valve = 0). However, in its closed position, the auxiliary valve 7 is energized (I_cooling_valve = I_block). This closed position of the auxiliary valve 7 also remains permanently maintained throughout the entire expansion operation.

[0045] In other words, the basic idea of ​​the invention is to identify an event with a high power requirement and to respond to it in a targeted manner. Based on this basic idea, there are two operating modes: normal operation and event intervention (extension operation). In order to evaluate whether a switch between normal operation and event intervention is necessary, the total volume flow requirement of all consumers 6a, 6b, 6c (Q_demand) is calculated. If the value is above an upper threshold Q_h, the "event intervention" mode is activated. If the value is below a lower threshold Q_I, the "normal operation" mode is activated. To simplify control in normal operation and extension operation, the maximum available voltage is preferably always applied to the pump motor 7 when the pump 2 is to be driven.The system 1 preferably contains a pressure relief valve 11 on the system rail 5, which prevents an excessively high system pressure p_sys during the event intervention. List of reference symbols 1 hydraulic system 2 pumps 3a first actuating valve 3b second actuating valve 3c third actuating valve 4 Exit 5 System rail 6a first consumer 6b second consumer 6c third consumer 7 Additional valve 8 Coolant and / or lubricant supply line 9 Tank 10a first junction 10b second junction 10c third junction 10d fourth junction 11 Pressure relief valve 12 Check valve 13 Electric motor 14 Entrance

Claims

[1] Method for controlling a hydraulic system (1) for an actuating device and a cooling and / or lubricating device of a motor vehicle, wherein the hydraulic system (1) comprises a pump (2), a plurality of actuating valves (3a, 3b, 3c), which actuating valves (3a, 3b, 3c) are each arranged between a system rail (5) connected to a pump outlet (4) and a hydraulic consumer (6a, 6b, 6c), and an additional valve (7), which additional valve (7) is arranged between the pump outlet (4) and a coolant and / or lubricant supply line (8), wherein the pump (2) is switched between normal operation and extended operation depending on an existing total power requirement of the hydraulic consumers (6a, 6b, 6c), wherein in normal operation, in which the pump (2) is permanently driven, an existing system pressure in the system rail (5) is determined at regular intervals and a target pressure of the system rail (5) is calculated and an upper pressure threshold and a lower pressure threshold are determined based on the target pressure, wherein the additional valve (7) is closed when the system pressure is below the lower pressure threshold and the additional valve (7) is open when the system pressure is above the upper pressure threshold, and wherein in the extension operation the pump (2) is permanently driven, the additional valve (7) is permanently closed and each of the actuating valves (3a, 3b, 3c) designed as pressure control valves is operated at least temporarily in dependence on an individual power requirement of the respective hydraulic consumer (6a, 6b, 6c) as soon as the system pressure reaches or exceeds a threshold value. [2] Method according to claim 1, characterized by that at least in normal operation, control of the actuating valves (3a, 3b, 3c) is decoupled from control of the pump (2). [3] Method according to claim 1 or 2, characterized by that a maximum available system voltage is applied to an electric motor (13) driving the pump (2) both in a first drive state of normal operation, in which the additional valve (7) is closed, and in the extended operation. [4] Method according to claim 3, characterized by that in the first drive state of normal operation, in which the additional valve (7) is closed, a different, preferably lower, or the same electrical voltage is applied to the electric motor (13) driving the pump (2) as in a second drive state of normal operation, in which the additional valve (7) is open. [5] Method according to one of claims 1 to 4, characterized bythat a pressure relief valve (11) is arranged in the system rail (5). [6] Method according to one of claims 1 to 5, characterized by that a check valve (12) blocking a backflow of hydraulic medium from the system rail (5) to the pump (2) is arranged between the pump outlet (4) and the system rail (5), wherein a branch (10d) leading to the additional valve (7) is arranged between the pump outlet (4) and the check valve (12). [7] Method according to one of claims 1 to 6, characterized bythat the total power requirement determining a switchover between normal operation and extended operation corresponds to a total volume flow requirement of all consumers (6a, 6b, 6c), wherein extended operation is activated when the total volume flow requirement is above an upper volume flow threshold value, and normal operation is activated when the total volume flow requirement is below a lower volume flow threshold value. [8] Method according to claim 7, characterized by that the total volume flow requirement is calculated on the basis of a sum of a first partial volume flow requirement determined by a first hydraulic consumer (6a, 6b, 6c) and a second partial volume flow requirement determined by at least one further second hydraulic consumer (6a, 6b, 6c), wherein the respective partial volume flow requirement is determined on the basis of a pressure-volume function stored in a software. [9] Method according to one of claims 1 to 8, characterized by that the target pressure is a maximum value from the group of consumer target pressures required at the respective individual consumer (6a, 6b, 6c). [10] Hydraulic system (1) for a motor vehicle, wherein the hydraulic system (1) is designed to carry out a method according to one of claims 1 to 9.

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