KR100653113B1 - Piezoelectric driving pump for a hydraulic brake device of a vehicle and method for driving the same - Google Patents

Abstract

The invention relates, in particular, to a piezoelectric pump 36 for a hydraulic vehicle braking device 10 having a slip control device. In the present invention, the elastic component 70 is disposed in the pump housing 56 including the pump chamber 76 in the form of a hollow chamber, the elastic component to operate the piezoelectric actuator 60, thereby changing the volume of the pump chamber 76. And the braking fluid is delivered.

Slip Control Unit, Hydraulic Braking Unit, Piezo Actuated Pump, Pump Housing, Piezo Actuator

Description

Piezoelectric driving pump for a hydraulic brake device of a vehicle and method for driving the same

1 is a hydraulic circuit diagram of a hydraulic vehicle braking device with a piezoelectric pump according to the present invention.

2 and 3 show another variant embodiment of the piezoelectric pump of FIG. 1 according to the invention.

* Description of the simple symbols for the main parts of the drawings *

12: main braking cylinder 14: braking cylinder

16: main braking line 20: wheel braking line

22: switching valve 26: pressure rising valve

30: pressure drop valve 36: hydraulic pump

46: buffer chamber 60: piezoelectric actuator

62: first piston 64: leaf spring

66: second piston 70: elastic parts

72: end wall

The present invention relates to a piezoelectric pump for a hydraulic vehicle braking device according to the preamble of claim 1 and a method of operating said pump according to the preamble of claim 8.

Such pumps are known from US Pat. No. 4,738, 493. Known pumps include piezoelectric actuators that can be extended by supplying a voltage. The piezoelectric actuator is arranged with a piston defining a pump chamber volume of the pump. In addition to the pump inlet communicating with the pump chamber, the pump outlet communicating with the pump chamber is equipped with a check valve as an inlet valve or an outlet valve of a piezoelectric pump. By applying a pulse voltage to the piezoelectric actuator, the piezoelectric actuators are alternately extended and shortened. The actuator reciprocates the piston and, by this reciprocating motion, alternately shrinks and expands the pump chamber, where the piezoelectric pump transfers the braking liquid in a known manner from a mechanically driven piston pump.

A piezoelectric pump according to the invention having the features of claim 1 has an elastic part, for example an elastomer body, which is received in the pump housing and surrounds the hollow chamber as a pump chamber in the pump housing. The pump chamber surrounded by the elastic component communicates with the pump outlet as well as the pump inlet. The elastic component may be loaded by a piezoelectric actuator installed in or inside the pump housing. By applying a voltage to the piezoelectric actuator and thus changing the length of the piezoelectric actuator, the elastic component is deformed and the volume of the pump chamber surrounded by the elastic component is changed. Subsequent interruption of the voltage changes the length of the piezoelectric actuator back to its original size, whereby the elastic part also returns to its original form and the pump chamber again has its original volume. By reducing the pump chamber, the braking liquid is discharged from the pump chamber, and by the expansion of the pump chamber, the braking liquid flows in through the pump inlet. By applying a pulse voltage to the piezoelectric actuator, the pump chamber of the piezoelectric actuated pump according to the present invention is alternately reduced and expanded to transfer the braking liquid. The cross section of the pump chamber is smaller than the internal cross section of the pump housing in which the elastic component surrounding the pump chamber is inserted so that a high pressure is produced at a given actuator force.

The elastic part can seal the pump chamber without a separate sealing device and has the advantage of separating the piezoelectric actuator from the braking liquid. This simplifies the structure of the piezoelectric pump according to the invention. Another advantage of the present invention is that, since the elastic part sufficiently fills the internal space of the pump housing, the dead space in the case where the piezoelectric actuator is extended to the maximum by supplying the maximum voltage, that is, the remaining residual volume of the pump chamber is small. Small dead space improves pump efficiency. In addition, a pump chamber having a small volume is formed of the elastic component, which is very important for its transfer efficiency in a general small stroke of a piezoelectric pump. Another advantage of the present invention is that the resilient component fills the interior space of the pump housing sufficiently, thereby preventing the collection of air or gas in the interior space of the pump housing which degrades the transfer efficiency of the piezoelectric pump. Another advantage of the piezoelectric actuated pump according to the invention is its compact, strong and simple structure consisting of a small number of parts.

Piezoelectrically actuated pumps according to the invention are provided, in particular, as pumps in braking devices of vehicles and are used in wheel braking cylinders in pressure control. Depending on the type of braking device, abbreviations ABS, ASR, FDR, EHB are used for the braking device. In the braking device, for example, to transfer the braking liquid from one wheel brake cylinder or multiple wheel brake cylinders to the main brake cylinder ABS, and / or one wheel brake cylinder or multiple wheel brake cylinders from a storage tank. A pump is used to transfer the braking fluid to (ASR, FDR, EHB). The pump is required, for example, in a braking device with wheel slip control devices ABS, ASR and / or in a braking device FDR and / or an electro-hydraulic braking device EHB used as steering aid. Through the wheel slip control devices ABS and ASR, for example, during braking by applying a high pressure to the brake pedal ABS and / or by applying a high pressure to the accelerator pedal ASR, the rotation of the driving wheel is suppressed (ASR). Blocking of the wheel can be prevented. In braking devices used as steering aid (FDR), the braking pressure in one or multiple wheel braking cylinders, regardless of the operation of the brake pedal or the accelerator pedal, for example to prevent the vehicle from leaving the desired route. Is formed. The pump can also be used in an electro-hydraulic braking system (EHB) when the pump supplies braking fluid to the wheel braking cylinder when the electric brake pedal sensor detects the operation of the brake pedal or when the pump fills the storage tank of the braking system. .

The dependent claims encompass preferred embodiments and refinements of the invention described in the independent claims.

In the method according to the invention of claim 8, the wheel braking cylinder is hydraulically coupled to the pump inlet and the pump outlet of the piezoelectric pump via the wheel braking pressure regulating valve device and through the change of the voltage applied to the piezoelectric actuator. Not only changes the volume of the wheel but also changes the wheel braking pressure present in the wheel braking cylinder. Firstly, the wheel braking pressure is formed by a main braking cylinder or a piezoelectric pump which is separated from the wheel braking cylinder, for example by closing the valve. The method according to the invention is preferably used for the adjustment of the wheel braking pressure or the like for anti-lock control during braking. The method according to the invention only needs to change the valve of the wheel braking pressure regulating valve device of the wheel braking cylinder while only changing the voltage applied to the piezoelectric actuator of the piezoelectric pump to change the wheel braking pressure for the purpose of anti-lock control. There is no advantage.

In the following the invention is preferably selected and explained in detail in accordance with the embodiments shown in the drawings.

The drawings are shown schematically and simply.

The hydraulic vehicle braking device 10 according to the invention shown in FIG. 1 has a two-circuit main braking cylinder 12 connected to two mutually independent braking circuits I and II. Only the braking circuit I is shown in FIG. 1, and the other braking circuit II is configured in the same manner and operates in the same manner. One or more wheel braking cylinders 14 may be connected to each of the braking circuits I and II. In the illustrated embodiment, two wheel braking cylinders 14 are connected to each braking circuit I and II.

The main braking line 16 is guided from the main braking cylinder 12 to the branch 18, in which the two wheel braking lines 20 are respectively guided to the wheel braking cylinder 14. Is divided into

In the main braking line 16, a switching valve 22 is provided between the main braking cylinder 12 and the branch 18. The switching valve 22 is a 2 / 2-way magnetic valve that is open in its basic position, and the differential pressure valve 24 is integrated in the magnetic valve, and the differential pressure valve is the switching valve (if the switching valve 22 is closed). 22) Limit the high pressure on the wheel brake cylinder side. The switching valve 22 is connected in parallel with a spring-loaded check valve 25 which can flow in the direction of the wheel braking cylinder 14.

A pressure raising valve 26 is connected in series to each wheel braking cylinder 14, that is, the pressure raising valve 26 is mounted on the wheel braking line 20 between the branch 18 and the wheel braking cylinder 14. do. The pressure raising valve 26 is formed as a 2/2 directional magnetic valve that opens in its basic position. The pressure rise valve 26 is connected in parallel with a spring-loaded check valve 28 which can flow in the direction of the main braking cylinder 12.

The pressure drop valve 30 is connected to each wheel braking cylinder 14 rearward. The pressure drop valve 30 is disposed in the return line 32, which is guided from the wheel braking cylinder 14 to the suction side or pump inlet 34 of the hydraulic pump 36. The pressure drop valve 30 is formed as a 2/2 directional magnetic valve closed in its basic position. A hydraulic reservoir 38 is connected to the return line 32 and a spring-loaded check valve 40 is arranged in the return line 32 which can flow in the direction of the hydraulic pump 36.

The transfer line 44 extends from the pressure side of the hydraulic pump 36 or from the pump outlet 42 to the main braking line 16, in which a buffer chamber 46 and a throttle 48 are installed. do. The feed line 44 passes into the main braking line 16 on the wheel braking cylinder side of the diverting valve 22 between the diverting valve 22 and the branch 18.

A suction line 50 is connected to the main braking line 16 between the main braking cylinder 12 and the switching valve 22, which is led to a pump inlet 34. The suction line 50 is arranged with a suction valve 52 formed as a 2 / 2-way magnetic valve closed in the basic position.

The pressure raising valve 26 and the pressure lowering valve 30 of each wheel braking cylinder 14 form wheel braking pressure regulating valve devices 26 and 30 of each wheel braking cylinder 14. The wheel braking pressure regulating valve device is a wheel braking pressure regulating valve device instead of the two 2/2 directional magnetic valves 26, 30, for example having a 3/3 directional magnetic valve, the valve being in the default position. In addition to engaging the wheel braking cylinder 14 with the wheel braking line 20, the wheel braking cylinder 14 is separated from the wheel braking line 20 and the return line 32 at other connection positions.

The vehicle braking device 10 receives a signal from the wheel rotation sensor 55 for anti-lock braking control (ABS), drive slip control (ASR) and / or vehicle dynamic control (FDR) during braking. , 26, 30, 52 and an electronic control device 54 for controlling the hydraulic pump 36. Wheel braking in the wheel braking cylinder 14 by adjusting the braking pressure using the wheel braking pressure regulating valve devices 26 and 30 and the hydraulic pump 36 for the above-described anti-lock braking adjustment, drive slip adjustment, and vehicle dynamic adjustment. The functions of the vehicle braking device 10, including the adjustment of pressure, are general to those skilled in the art and will not be described in detail herein.

The hydraulic pump 36 is formed as a piezoelectric pump 36 according to the invention. The piezoelectric pump has a pump housing 56 in the form of a hollow cylinder consisting of two parts, the pump housing being divided in a radial plane and the two parts of the housing being coupled to each other via bolts 58. The piezoelectric actuator 60 consists of piezoelectric discrete parts in the form of disks stacked in a known manner or in a multi-layer technique. Voltage may be applied to the laminated parts or piezoelectric layers of the piezoelectric actuator 60 manufactured by the multilayer technology, which is briefly described below as a phenomenon generated by applying a voltage to the piezoelectric actuator 60. By applying a voltage to the piezoelectric actuator 60, the piezoelectric actuator is extended in the axial direction by the piezoelectric effect. In contrast, when the voltage is cut off, the piezoelectric actuator 60 is reduced back to its original or original length.

The first piston 62 is in contact with the end face of the piezoelectric actuator 60. The piston 62 is pressed against the piezoelectric actuator 60 by the leaf spring 64, which spring 64 is supported in a slot formed along the periphery inside the pump housing 56. The leaf spring 64 sets the piezoelectric actuator 60 in the axial direction under mechanical prestress to avoid the tensile load of the piezoelectric actuator 60 because the piezoelectric actuator 60 can only receive low tensile loads. to be. In addition, the mechanical prestress increases the length expandability of the piezoelectric actuator 60 by the application of a voltage, and through the mechanical prestress of the piezoelectric actuator 60, not only the stroke of the piezoelectric pump 36 but also its working capacity. Is increased.

The opposite end face of the piezoelectric actuator 60 of the first piston 62 is provided with a second piston, and the second piston has a side facing the first piston 62 which forms a free space for the leaf spring 64. An annular step 68 is provided that is disposed along the perimeter.

An elastic component 70 is disposed on the end face of the second piston 66 opposite the piezoelectric actuator 60. This elastic component 70 is in the form of a circular disk and is disposed in the pump housing 56 between the second piston 66 and the end wall 72 of the pump housing 56. The elastic component 70 has a spherical circumferential edge, the edge of which is in sealing manner to the interior of the pump housing 56 in a relaxed state not extending axially with the elastic component. When the voltage supply to the piezoelectric actuator 60 is interrupted, the elastic component 70 extends slightly in the axial direction and is inserted between the second piston 66 and the end wall 72 of the pump housing 56. When the piezoelectric actuator extends in the axial direction by applying a voltage, the elastic component 70 extends in the axial direction, which means that the elastic component is compressed. The elastic component 70 consists of an elastomer having a low shore hardness and a low internal buffering rate in the illustrated embodiment of the present invention, in which the voltage applied to the piezoelectric actuator 60 is cut off so that the piezoelectric actuator is of its original length. When it is reduced to, it recovers again almost without delay.

An elastic component 70 surrounds the pump chamber 76 between this elastic component and the end wall 72 of the pump housing 56. The pump chamber 76 is formed in the middle of the end face of the elastic component 70, which abuts the end wall 72 of the pump housing 56 through a hemispherical flat recess. The diameter of the pump chamber 76 is smaller than the inner diameter of the pump housing 56. In the illustrated embodiment, the diameter of the pump chamber 76 corresponds to about one third of the inner diameter of the pump housing 56. Thus a high feed pressure of the piezoelectric pump 36 at a given actuator force can be achieved.

Through the central hole 78 formed in the end wall 72 of the pump housing 56, the pump chamber 76 communicates with the holes 34 and 42 radially penetrating the end wall 72, the hole being pumped. Inlet 34 and pump outlet 42 are formed. Spring-operated check valves 80 and 82 are inserted into the transverse holes 34 and 42 on both sides of the central hole 78, one of which can flow in the direction of the central hole 78 and inlet valves. 80 is formed, the other transverse hole may flow outward from the central hole 78 and form the discharge valve 82 of the piezoelectric pump 36.

In addition, by arranging the elastic component 70 which generally fills the interior space of the pump housing 56 between the second piston 66 and the end wall 72 of the housing 36, at and below the dead space, ie the maximum voltage. Due to this, the remaining volume of the piezoelectric actuated pump 36 remaining when the piezoelectric actuator 60 extends in the axial direction to the maximum is small, thereby obtaining high efficiency. In addition, the elastic component 70 reliably seals the piezoelectric actuator 60 from the braking liquid of the hydraulic vehicle braking apparatus 10.

By applying a pulse voltage to the piezoelectric actuator 60, the piezoelectric actuators are alternately extended and shortened, so that the piezoelectric actuators 60 alternately squeeze the elastic parts 70 and relax again, thereby alternating the pump chamber 76. To the original volume. At this time, the braking liquid is alternately discharged from the pump chamber 76 through the discharge valve 82 and sucked again through the inlet valve 80, the piezoelectric pump 36 applies a pulse voltage to the piezoelectric actuator 60. Thereby transferring the fluid. To this end, a voltage source 84 is provided, for example a battery of a vehicle, wherein the variable voltage of the voltage source is, for example, via a transformer 86 of 12 V, as the voltage required to control the piezoelectric actuator. The voltage is converted to a voltage of about 100 V for the low voltage piezoelectric actuator 60 or about 1000 V for the high voltage piezoelectric actuator 60. The application of a voltage to the piezoelectric actuator 60 is controlled via the power output stage 88 by the electronic control device 54.

The control or adjustment of the wheel braking pressure in the wheel braking cylinder 14 for braking, for example for anti-lock adjustment, is made according to the invention as follows: Wheel braking pressure is actuated through the operation of the main braking cylinder 12 and / or piezoelectric. After being generated by the actuated pump 36 and the electronic control device 54 determines the degree of blocking of the wheel via the wheel rotation sensor 55, the changeover valve 22 is closed and the intake valve 52 remains closed. do. Thus, the main braking cylinder 12 is separated from the other vehicle braking device 10. The braking pressure raising valve 26 and the associated braking pressure lowering valve 30 of the corresponding wheel braking cylinder 14 are opened so that the corresponding wheel braking cylinder 14 is opened at the pump inlet of the piezoelectric pump 36. And a pump outlet 42. At the same time, the brake braking pressure rise valve 26 without blocking tendency is closed and the associated braking pressure drop valve 30 remains closed, so that the wheel braking cylinder 14 is piezoelectrically operated pump 36. Separated from. The piezoelectric actuator 60 is preferably applied with a variable voltage between " 0 " and the maximum voltage prior to the closing of the switching valve 22. As the voltage applied to the piezoelectric actuator 60 rises and falls, the volume of the pump chamber 76 of the piezoelectric actuated pump 36 is reduced or expanded, and the pressure of the braking liquid in the pump chamber 76 rises or falls. When the pressure in the pump chamber 76 rises, the wheel braking pressure in the wheel braking cylinder 14 increases through the discharge valve 82 of the piezoelectric pump 36 and the open braking pressure raising valve 26. When the pressure in the 76 drops, the wheel braking pressure in the wheel braking cylinder 14 becomes the inlet valve 80 of the open braking pressure drop valve 30 of the wheel braking cylinder 14 and the piezoelectric pump 36. Descends through). It is not necessary to always switch the magnetic valves 26, 30 of the vehicle braking device 10 for the wheel braking pressure adjustment by the method according to the invention, and the control or adjustment of the wheel braking pressure is applied to the piezoelectric actuator 60. This is achieved by increasing or decreasing the voltage.

In the piezoelectric actuated pump 36 according to the invention shown in FIG. 2, the pump chamber 76 is formed in a flat recess in the form of a hemisphere at the end wall of the pump housing 56, in the embodiment of the invention, a circular The disk-shaped elastic component 70 has two flat end faces without recesses.

3 shows another embodiment of a piezoelectric pump 36 according to the invention. The pump chamber 76 is here formed as a hollow chamber, ie, a kind of honeycomb 90, which communicates with the central hole 78 through the central hole 92 at the end wall 72 of the piezoelectric pump 36.

Notwithstanding the above-described differences of the piezoelectrically operated pumps 36 shown in FIGS. 2 and 3, they are not only configured identically to the piezoelectrically operated pumps 36 shown in FIG. 1 and operate in the same manner. The same reference numerals are used for identical components.

The piezoelectric actuated pump 36 according to the invention shown in the figure has an inner diameter of about 40 to about 50 mm in the housing and is about 5 cm ³ / S at a 30 Hz frequency of variable voltage applied to the piezoelectric actuator 60 of the pump. Has a feed rate of.

In the present invention, the elastic component can seal the pump chamber without a separate sealing device and has the advantage of separating the piezoelectric actuator from the braking liquid. Another advantage of the present invention is that since the elastic component fills the inside of the pump housing as a whole, the dead volume which forms the remaining volume of the pump chamber when the piezoelectric actuator is extended to the maximum by the supply of the maximum voltage is reduced to improve the efficiency of the pump. It can be improved. Another advantage of the piezoelectric pump according to the invention is that the structure is compact, strong and simple, consisting of only a few parts.

Claims (8)

In the piezoelectric actuated pump 36 for a hydraulic vehicle braking device having a pump housing and a piezoelectric actuator capable of varying its length by applying a voltage, The piezoelectric pump 36 has an elastic component 70 which is inserted into the pump housing 56 and can be deformed by a change in length of the piezoelectric actuator 60, The elastic component 70 surrounds the hollow chamber forming the pump chamber 76, which communicates with the pump inlet 34 and the pump outlet 42 and has a volume that is varied by the deformation of the elastic component 70. , The pump chamber (76) has a lateral size smaller than the inner lateral size of the pump housing (56). 2. A piezoelectric pump as claimed in claim 1 wherein said elastic component (70) seals said pump chamber (76) in said pump housing (56). 2. A piezoelectric pump as claimed in claim 1 wherein the pump chamber (76) is formed between the elastic component (70) and the housing wall (72) of the pump housing (56). 2. A piezoelectric pump as claimed in claim 1 wherein the pump chamber (76) is surrounded by the elastic component (70). The piezoelectric actuated pump according to claim 1, wherein the elastic part (70) is made of an elastomer. The piezoelectric pump according to claim 1, wherein the elastic component (70) has a low hardness. 2. The piezoelectric pump as claimed in claim 1, wherein the piezoelectric pump (36) has a prestress component (64) for applying mechanical prestress to the piezoelectric actuator (60). A hydraulic vehicle having a wheel braking cylinder and a wheel braking pressure regulating valve device through a piezoelectric pump according to any one of claims 1 to 7, and hydraulically connecting the wheel braking cylinder to the vehicle braking cylinder. In the operating method for operating the braking device, Wheel braking pressure is generated in the wheel braking cylinder 14, A voltage is applied to the piezoelectric actuator 60 of the piezoelectric pump 36, The wheel braking cylinder 14 is coupled with the pump inlet 34 and the pump outlet 42 of the piezoelectric pump 36 by wheel braking pressure regulating valve devices 26, 30, Piezoelectric actuated pump, characterized in that the wheel braking pressure is changed by the change of the voltage applied to the piezoelectric actuator (60).

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