KR20010076218A - Piezoelectric driving pump for a hydraulic brake device of a vehicle and method for driving the same - Google Patents

Abstract

PURPOSE: A piezoelectrically operated pump and method for operating piezoelectrically operated pump is provided to achieve a compact, rigid and lightweight structure consisting of a small number of component parts, while allowing the length of the piezoelectric actuator to be varied through the application of voltage. CONSTITUTION: A piezoelechically operated pump(36) has an elastic member(70), which is inserted into a pump casing(56) and deformed by varying the length of a piezoelectric actuator(60). The elastic member defines a hollow chamber forming a pump chamber(76), the hollow chamber communicating with a pump inlet(34) and a pump outlet(42) and being variable in volume through the deformation of the elastic member. The pump chamber has an inner lateral dimension smaller than the lateral dimension of the pump casing.

Description

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

The present invention relates to a piezoelectric drive pump having the features of the preamble of claim 1 and a drive method of the drive pump having the features of the preamble of claim 8.

Such pumps are known from US Pat. No. 4,738, 493. This known pump has a piezoelectric actuator which can be changed in length by supplying a current. Here, the piezoelectric actuator is provided with a piston defining a pump chamber volume of the pump. Further, not only the pump inlet communicating with the pump chamber but also the pump outlet communicating with the pump chamber are respectively equipped with a check valve as an inflow valve and a piezoelectric drive pump as a discharge valve. At this time, the piezoelectric actuator repeats expansion and contraction by providing a pulse voltage to the piezoelectric actuator. As such, the actuator exerts a reciprocating stroke on the piston that alternately shrinks and expands the pump chamber by moving the piston back and forth, wherein the piezoelectric drive pump delivers the braking fluid through a known method from a mechanically operated piston pump.

A piezoelectric drive pump according to the invention having the features of claim 1 has an elastic component, which is housed in a pump housing and encloses a pump chamber in the form of a hollow chamber in the pump housing, for example made of an elastomeric material. The pump room surrounded by the elastic component communicates with the pump outlet as well as the pump inlet. The elastic component may actuate a piezoelectric actuator installed on or within 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. Thereafter, by interrupting the supply of current, the piezoelectric actuator is restored to its original size, thereby returning the elastic part to its original form and the pump chamber again maintaining its original volume. By reducing the pump chamber, the braking liquid is discharged from the pump chamber and through 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 drive pump according to the present invention is alternately reduced and expanded to transport 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 arranged to generate a predetermined actuator force at high pressure.

The elastic component has the advantage of first sealing the pump chamber without an independent sealing device and separating the piezoelectric actuator from the braking fluid. In addition, the structure of the piezoelectric drive pump according to the present invention has the advantage of being very simple. Another advantage of the present invention is that the gap between which the elastic part is widely filled in the interior of the pump housing to form the residual volume of the pump chamber can be reduced by the application of the maximum voltage at the maximum change of the piezoelectric actuator. The gap formed in this way can improve the efficiency of the pump. In addition, the use of elastic components in the pump chamber allows the volume to be kept low, which is very important for transport efficiency in the general small stroke of piezoelectric drive pumps. Another advantage of the present invention is that the elastic component can be widely filled in the inner space of the pump housing to prevent the intake of air or gas into the inner space of the pump housing. The efficiency is lowered. Another advantage of the piezoelectric drive pump according to the invention is that the structure is compact, strong and simple, consisting of only a few components.

The piezoelectric drive pump according to the invention is provided, in particular, as a pump in the braking device of a vehicle and is used in wheel brake cylinders in pressure control. According to the description of the braking device, ABS, ASR, FDR, EHB, which are written in abbreviations, are used for the braking device thus formed. As the braking device, for example, to transfer the braking liquid from the vehicle braking cylinder or the plurality of wheel braking cylinders to the main braking cylinder ABS, and / or the wheel braking cylinder or the plurality of wheel braking cylinders ASR, FDR from the storage tank. , EHB) is used to supply the braking fluid. This pump is necessary, for example, in a braking device and / or an electro-hydraulic braking device EHB equipped with wheel slip control devices ABS and ASR. Through the wheel slip control devices ABS and ASR, for example, during braking by applying a high pressure to the brake pedal and / or by applying a high pressure to the gas pedal ASR, the rotation of the driving wheel is suppressed (ASR). Blocking of the wheel can be prevented. In a braking device used as a steering device (FDR), for example, a wheel braking cylinder or a plurality of wheel braking cylinders may be used independently of the operation of the brake pedal and the gas pedal to prevent the vehicle from deviating from a desired route. Braking pressure is applied. The pump according to the invention can also be used in an electrohydraulic braking system (EHB) when the pump supplies braking fluid to the wheel braking cylinder while the electric brake pedal sensor senses the operation of the brake pedal or when the pump fills the storage tank of the braking system. have.

The dependent claims have a structure different from the preferred form of the invention described in the independent claims.

A method according to the invention of claim 8, wherein the wheel braking cylinder is hydraulically coupled to the pump inlet and the pump outlet of the piezoelectric drive pump via the wheel braking pressure regulating valve device and through the change of the voltage applied to the piezoelectric actuator. In addition to changing the volume of, it is possible to change the wheel braking pressure in the wheel braking cylinder. First, the wheel braking pressure is applied to the main braking cylinder or the piezoelectric drive pump separated from the wheel braking cylinder by closing the valve, for example. The method according to the invention is preferably used for the adjustment of the wheel braking pressure for the control of blocking slip during braking. The method according to the invention only requires changing the wheel braking pressure regulating valve device of the wheel braking cylinder while changing only the voltage applied to the piezoelectric actuator of the piezoelectric drive pump in order to change the wheel braking pressure for the purpose of blocking slip control. There is no advantage.

Hereinafter, the present invention is preferably selected and described in detail according to the embodiments shown in the drawings.

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

2 and 3 each show another embodiment of the piezoelectric drive 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: front wall

The drawings are schematic and simplified.

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. 1 shows only the braking circuit I, 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 point 18, at which point two wheel braking lines 20 are respectively guided to the wheel braking cylinder 14. Is divided into

On the main braking line 16 a switching valve 22 is provided between the main braking cylinder 12 and the branch point 18. The switching valve 22 is a 2 / 2-way magnetic valve constituting the differential pressure valve 24 existing in the open position at the basic position of the valve, and the wheel of the switching valve 22 is closed as the switching valve 22 is closed. High pressure is formed on the braking 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 to the wheel braking line 20 between the branch point 18 and the wheel braking cylinder 14. do. The pressure raising valve 26 is formed as a 2 / 2-way magnetic valve that is open in its default position. A spring-loaded check valve 28 which can flow in the direction of the wheel braking cylinder 12 is connected in parallel to the pressure raising valve 26.

A pressure drop valve 30 is connected to each wheel braking cylinder 14. 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 of the hydraulic pump 36 or the pump inlet 34. The pressure drop valve 30 is formed as a 2 / 2-way magnetic valve that is in the closed state at its default position. Not only is the hydraulic reservoir 38 connected to the return line 32, but it is also arranged with a spring-loaded check valve 40 which can flow in the direction of the hydraulic pump 36.

From the pressure side of the hydraulic pump 36 or from the pump outlet 42, a supply line 44 is provided which is provided with a buffer chamber 46 and a throttle 48 to the main braking line 16. The supply line 44 communicates with the wheel braking cylinder side of the switching valve 22 between the switching valve 22 and the branch point 18 arranged in the main braking line 16.

A suction line 50 guided to the pump inlet 34 is connected to the main braking line 16 between the main braking cylinder 12 and the switching valve 22. The suction line 50 is arranged with a suction valve 52 formed as a 2 / 2-way magnetic valve present in the closed position 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-way magnetic valves 26, 30, for example having a 3 / 3-way magnetic valve, which valve in its 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.

For braking blocking adjustment (ABS), anti slip adjustment (ASR) and / or vehicle dynamic adjustment (FDR) during braking, the vehicle braking device 10 receives a signal from the wheel rotation sensor 55 to control the magnetic valve 22, 26, 30, 52 and an electric control device 54 for controlling the hydraulic pump 36. Wheels existing in the wheel braking cylinder 14 by adjusting the braking pressure by using the wheel braking pressure regulating valve devices 26 and 30 and the hydraulic pump 36 for the above-described blocking slip control, anti slip control, and vehicle dynamic control. The function of adjusting the braking pressure and other functions of the vehicle braking device 10 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 drive pump 36 according to the invention. This piezoelectric drive pump has a pump housing 56 in the form of a hollow cylinder consisting of two parts, in which the pump housing is divided in a radial plane, wherein both parts are coupled to each other via bolts 58. The piezoelectric actuator 60 is configured as piezoelectric discrete parts in the form of superimposed discs through known schemes and multi-layer techniques. As such, voltage may be applied to the piezoelectric layered structure of the piezoelectric actuator 60 manufactured by the overlapping component or the multilayer technology. Hereinafter, the phenomenon caused by applying a current to the piezoelectric actuator 60 will be briefly described. By applying a current to the piezoelectric actuator 60, the piezoelectric actuator expands in the axial direction in accordance with the piezoelectric effect. On the contrary, when the current is cut off, the piezoelectric actuator 60 is reduced back to its original length.

The first piston 62 is disposed in front of the piezoelectric actuator 60. The piston 62 is circumferentially formed inside the pump housing 56 and compressed against the piezoelectric actuator 60 by a leaf spring 64 supported in the slot. The leaf spring 64 sets the piezoelectric actuator 60 in the axial direction under a mechanical compressive stress that suppresses the tensile load of the piezoelectric actuator 60 because only the low tensile load is applied to the piezoelectric actuator 60. Because it is necessary. In addition, the mechanical compressive stress increases the elasticity of the piezoelectric actuator 60 by applying an electric current, and through the mechanical compressive stress of the piezoelectric actuator 60, not only the stroke of the piezoelectric drive pump 36 but also the operation thereof. Ability is increased.

On the front side of the first piston 62 spaced from the piezoelectric actuator 60, a second piston provided with an annular step 68 disposed circumferentially on the side facing the first piston 62 is disposed, and the leaf spring is arranged. Form 64 free spaces.

An elastic component 70 is disposed in front of the second piston 66 spaced apart from 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 front wall 72 of the pump housing 56. In addition, the elastic component 70 has a spherical edge along the circumference, so that the elastic component may be arranged to be sealed inwardly with respect to the pump housing 56 in a relaxed state without being compressed in the axial direction. When the current supply to the piezoelectric actuator 60 is stopped, the elastic component 70 is inserted between the second piston 66 and the front wall 72 of the pump housing 56 to be slightly pressed in the axial direction. When the piezoelectric actuator expands in the axial direction by applying a current, the elastic component 70 is pressed in the axial direction, which means that the elastic component is compressed. The elastic component 70 is composed of an elastomer having a low shore hardness and a low internal buffer ratio in the embodiment shown according to the present invention, and recovers almost without delay when the current applied to the piezoelectric actuator 60 is cut off. It is reduced in length.

An elastic component 70 surrounds the pump chamber 76 between this elastic component and the front wall 72 of the pump housing 56. The pump chamber 76 is formed in the middle of the front side of the elastic component 70 in contact with the front wall 72 of the pump housing 56 through a hat-shaped 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. For this reason, when a predetermined actuator force is formed, a high supply pressure may occur in the piezoelectric drive pump 36.

Through the central hole 78 formed in the front wall 72 of the pump housing 56, the pump chamber 76 communicates with the holes 34, 42 radially penetrating the front wall 72, thereby allowing the pump inlet ( 34 and pump outlet 42 are formed. The lateral holes 34 and 42 are provided with spring-actuated check valves 80 and 82 at both sides of the center hole 78, which are piezoelectric drives capable of flowing through in the direction of the center hole 78. On the other side of the inlet valve 80 of the pump 36, a discharge valve 82 is formed which can flow outward from the central hole 78.

In addition, by arranging the elastic component 70 which fills the internal space of the pump housing 36 widely between the second piston 66 and the front wall 72 of the housing 36, a piezoelectric actuator ( The gap which constitutes the remaining volume of the piezoelectric drive pump 36 formed when 60 is maximally extended in the axial direction is reduced, and thus high efficiency can be obtained. In addition, the elastic component 70 reliably seals the piezoelectric actuator 60 from the braking liquid of the hydraulic vehicle braking device 10.

By applying a pulse voltage to the piezoelectric actuator 60, the piezoelectric actuator is alternately expanded and contracted, so that the piezoelectric actuator 60 alternately compresses and elastically relaxes the elastic component 70, thereby causing the pump chamber to Alternately reduce (76) and expand to the original volume again. At this time, the braking liquid is alternately discharged from the pump chamber 76 through the discharge valve 82 and flows back through the inlet valve 80, wherein the piezoelectric drive pump 36 pulses the piezoelectric actuator 60 with a pulse voltage. Supply fluid by adding To this end, a power source 84 is provided, for example a battery of a vehicle, the variable voltage of which is a low voltage piezoelectric element as the voltage required for controlling the piezoelectric actuator, for example, via a transformer 86 of 12V. A voltage of about 100 V is applied for the type actuator 60 or about 1000 V for the high voltage piezoelectric actuator 60. The application of the variable voltage to the piezoelectric actuator 60 is controlled by the electronic control device 54 via an efficiency sending step 88.

The control or adjustment of the wheel braking pressure in the wheel braking cylinder 14 during braking, for example for blocking slip control, is made according to the invention as follows: The wheel braking pressure is actuated through the operation of the main braking cylinder 12. And / or after being applied to the piezoelectric drive pump 36 and after the electronic control device 54 determines the degree of blocking of the wheel via the wheel rotation sensor 55, the switching valve 22 and the intake valve 52 are It is closed. Thus, the main braking cylinder 12 is separated from the other vehicle braking device 10. The braking pressure lowering valve 30 associated with the brake pressure raising valve 26 of the corresponding wheel braking cylinder 14 is opened, so that the corresponding wheel braking cylinder 14 is opened at the pump inlet of the piezoelectric drive pump 36. And a pump outlet 42. At the same time, the brake braking pressure raising valve 26 of the wheel, which is unlikely to cause blocking, is closed and the associated braking pressure lowering valve 30 is closed, so that the wheel braking cylinder 14 has a piezoelectric drive pump 36. Separated from. The piezoelectric actuator 60 is mainly subjected to a variable voltage between "0" and the maximum voltage before closing of the switching valve 22. By increasing and decreasing the voltage applied to the piezoelectric actuator 60, the volume of the pump chamber 76 of the piezoelectric drive pump 36 is reduced or expanded, thereby increasing or decreasing the pressure of the braking liquid in the pump chamber 76. 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 drive 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 drive pump 36. Descends through). By carrying out the method according to the invention, it is not necessary to always switch the magnetic valves 26, 30 of the vehicle braking device 10 for the wheel braking pressure adjustment, and the control or adjustment of the wheel braking pressure is carried out with a piezoelectric actuator 60. This is achieved by raising or lowering the variable voltage applied to).

In the piezoelectric drive pump 36 according to the invention shown in FIG. 2, the pump chamber 76 is formed as a flat recess in the form of a hat at the front wall of the pump housing 56, in this embodiment according to the invention. The elastic component 70 in the form of a circular disk has two flat fronts without recesses.

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

Notwithstanding the above-described differences of the piezoelectric drive pumps 36 shown in Figs. 2 and 3, they are not only identical to the piezoelectric drive pumps 36 shown in Fig. 1, but also function in the same manner. The same reference numerals are used for identical components.

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

In the present invention, the elastic component can first seal the pump chamber without an independent sealing device and has the advantage of separating the piezoelectric actuator from the braking liquid. Another advantage of the present invention is that the gap between the elastic part being filled in the interior of the pump housing to form the remaining volume of the pump chamber can be reduced by applying the maximum voltage at the maximum change of the piezoelectric actuator to improve the efficiency of the pump. will be. Another advantage of the piezoelectric drive pump according to the invention is that the structure is compact, strong and simple, consisting of only a few components.

Claims (8)

In the piezoelectric drive pump 36 for a hydraulic vehicle braking device having a pump housing and a piezoelectric actuator capable of varying the length by applying a voltage, The piezoelectric drive pump 36 has an elastic component 70 that can be disposed within the pump housing 56 to change the length of the piezoelectric actuator 60, The elastic component 70 surrounds the pump chamber 76 in the form of a hollow chamber in communication with the pump inlet 34 and the pump outlet 42 and capable of changing the volume through deformation of the elastic component 70, The pump chamber (76) is a piezoelectric drive pump, characterized in that having a transverse diameter less than the transverse inner diameter of the pump housing (56). 2. The piezoelectric drive pump according to claim 1, wherein the elastic component (70) seals the pump chamber (76) in the pump housing (56). 2. The piezoelectric drive pump according to claim 1, wherein the pump chamber (76) is surrounded between an elastic component (70) and a housing wall (72) of the pump housing (56). The piezoelectric drive pump according to claim 1, wherein the pump chamber (76) is surrounded by an elastic component (76). The piezoelectric drive pump according to claim 1, wherein the elastic component (70) is made of an elastomer. The piezoelectric drive pump according to claim 1, wherein the elastic component has a low hardness. 2. A piezoelectric drive pump according to claim 1, characterized in that the piezoelectric drive pump (36) has a compressive stress component (64) for applying mechanical compressive stress to the piezoelectric actuator (60). A hydraulic vehicle braking device having a wheel braking cylinder and a wheel braking pressure regulating valve device and hydraulically connecting a wheel braking cylinder to a vehicle braking cylinder through a piezoelectric drive pump according to any one of claims 1 to 7. In the driving method for driving, Wheel brake pressure is applied to the wheel braking cylinder 14, A variable voltage is applied to the piezoelectric actuator 60 of the piezoelectric drive pump 36, The wheel braking cylinder 14 is coupled with the pump inlet 34 and the pump outlet 42 of the piezoelectric drive pump 36 via the wheel braking pressure regulating valve devices 26, 30, Piezoelectric drive pump, characterized in that the wheel brake pressure is changed by the variable voltage applied to the piezoelectric actuator (60).