Diagnostic valve

Abstract

A diagnostic valve for a brake system of a vehicle. The valve includes a first brake fluid opening for communicating with a brake fluid reservoir, a second brake fluid opening for communicating with a

Description

Field of the invention The invention relates to electronic braking control systems, and in particular, it refers to a diagnostic valve for a brake system based on a Tesla valve principle. Background of the invention The current diagnostic valves for the brake systems are designed for control of the pressure of the amount of the brake fluid passing from the reservoir to the tandem master cylinder according to electric control commands from the electronic units of the vehicle while monitoring the flow pressure requirements and checking the leaks of the brake system. In addition, the diagnostic valves ensure the change of the brake fluid pressure by a diphasic algorithm lifting and dump of pressure at specified values, allowing the reverse direction of the brake fluid from the tandem master cylinder to reservoir while maintaining braking fluid in the braking unit. The control of the amount of brake fluid is provided by the calibrated openings of the valves. However, the known diagnostic valves, for example the diagnostic valve type shown in Figure 1, have complicated designs, involving many complex inter-relating parts which are moving in respect to each other which generates a variety of operational issues in maintaining control of flow, temperature, and pressures in the brake systems. Disadvantages of prior art The known diagnostic valves have the following disadvantages: - known diagnostic valves have a high number of parts, with moving components, and various materials, with negative impact on tolerance chain / stack-up which may generate errors in functioning; - known diagnostic valves are space consumption solutions, needing a big packaging space; - known diagnostic valves involve complex assembling, and manufacturing processes which require specific tools and devices determining increased cost and production cycle time. Problem to be solved by the invention The invention attempts to solve the problems of high number of parts and materials, moving parts, big packaging space by providing a new diagnostic valve easier to be produced, easier to be adapted to each brake system, having a reduced production cycle time and corresponding costs, and being more robust. Summary of the invention In order to overcome the disadvantages of prior art, in a first aspect of the invention it is presented a diagnostic valve for a brake system of a vehicle comprising: - a first brake fluid opening for communicating with a first brake pipe from a reservoir of a brake fluid system; - a Tesla valve channel configured for connecting said first brake fluid opening with the second brake fluid opening, said Tesla valve channel comprising at least a series of Tesla valve units, each Tesla valve unit having a forward configuration, and a reverse configuration, said at least a series of Tesla valve units being formed by consecutively connecting each other of the Tesla valve units arranged with the forward configuration towards the second brake fluid opening thus defining a forward direction of the Tesla valve channel from the first brake fluid opening to the second brake fluid opening, and a reverse direction from the second brake fluid opening to the first brake fluid opening. In a second aspect of the invention it is presented a brake system comprising the diagnostic valve. Further advantageous embodiments are the subject matter of the dependent claims. Advantages The invention important advantages are as follows: - the new diagnostic valve has a compact, and a very versatile design allowing fine-tuning of its working space when a small distance is required at a wide range of sizes and in a variety of environments, - the new diagnostic valve has a reduced assembly and manufacturing complexity processes because the diagnostic valve is made from a single material that leads to a reduced production cycle time, while providing durability. - the new diagnostic valve compensates a wide tolerance interval of the assembly, since it is used a single component easy to be assembled, and does not have moving parts which may generate errors in operating conditions, - the new diagnostic valve is more robust than the known diagnostic valves, thus its life time is increased. Further features and advantages of the invention stems from the following description and the claims with reference to the accompanying drawings in which like reference characters designate the same component throughout the figures. Brief description of the drawings The invention will hereafter be described with reference to the drawings where: Fig. 1 shows a diagnostic valve according to the prior art presenting the complexity of the design Fig. 2a depicts an optimization study model consisted of a Tesla valve unit having a D configuration with its parameters used for conception of the invention, Fig. 2b depicts a further optimization study of the invention using a series of two Tesla valve units of the optimization study model of the Fig. 2a, Fig. 3 depicts one embodiment of the diagnostic valve according to the invention where the diagnostic valve consists of a cylindrical body having 9 Tesla valve units, Fig. 4 depicts another embodiment of the diagnostic valve according to the invention where the diagnostic valve comprises a rolled cylindrical body and a hollow shell. Detailed description In a first aspect of the invention, it is presented the diagnostic valve for the brake system of the vehicle. The inventors conceived a geometrical relationship for the diagnostic valve derived from an optimization study model comprising a Tesla valve unit of a D configuration, as shown in Fig. 2a. Based on the model of Fig. 2a, performance investigations in terms of diodicity and specific pressure-flow rate characteristics requirements of the brake system have been carried out resulting the geometry and design of the diagnostic valve according to the invention. In the Fig. 2a it is presented the optimization study model consisted of a Tesla valve unit having a D configuration consisting in a set of cavities and fluid-flow guides that allow flow with low resistance in forward direction but result in a high resistance to flow in the reverse direction, hence building up a backpressure. Each flow control segment consists of a slight deviation from the straight line path from source to target. The following values of the Tesla valve unit parameters shown in the Fig. 2a have been selected for the model: W= 2; L1 = 10; L2= 2; L3= 8.75; L4=7.86; L5=24,65; L6=50, R=22, a= 2,5 ( a= 33°), b= 4((3=243,5°), and e = 75°). The diameter of the Tesla valve channel of the model Tesla valve unit has been varried in a range of 0.2 to 2 mm. Thus, the inventors applied the Tesla valve principle, according to which the quantitative measure of flow delivery efficiency is expressed in diodicity, being the ratio of pressure drops for identical flow rates: where A^r is the reverse flow pressure drop, and APf is the forward flow pressure drop for flow rate . Based on the results of the optimization study model, the inventors adapted further optimization study models by arranging the Tesla valve units in series, tunning the size of the Tesla channel, and number of the Tesla valve units in order to obtain the pressure flow requirements of the brake system, as it is presented in Fig.2b, where two Tesla valve units have been arranged in a series at a distance of 17.5 mm between the Tesla valve units, and the following parameters have been selected W= 1; L3= 4,5; L5=13,5; R=11, and a= 1,25. In order to further define the features of the diagnostic valve, and to verify the performance based on the geometric values of the optimization study models comprising series of the Tesla valve units, the inventors also have taken into consideration the particularities of a brake fluid in terms of its hydraulic characteristics for calculating the Reynolds number to assess the pattern of the brake fluid flow: where p is the fluid density, V is the velocity of the flow, Dh is the hydraulic channel diameter, p dynamic viscosity of fluid, and Q is the debit of the brake fluid. Thus, in the optimization study models the following set of parameters of the brake fluid have been considered: Eh100 mm / s; p= 1043 kg / m3; V= 3.5m / s2; Q= 30cm3 / s in order to adjust the characteristics of the Tesla valve channel. According to the optimization study models carried out by the inventors, a Reynolds number at a value Re= 77 has been obtained, predicting a laminar flow of the brake fluid with well-defined streamlines of smooth, constant and orderly fluid motion without disruptions. The inventors conceived the diagnostic valve as a compact valve based on the Tesla valve principle of the hydraulic diode, having a fixed-geometry which is capable to provide at least the same pressure performance as the existing diagnostic valves for the brake systems having an increased life cycle, being resistant to wear and fatigue. Therefore, the diagnostic valve according to the invention comprises a first brake fluid opening for communicating with a first brake pipe from a reservoir of a brake fluid system of the vehicle, a second brake fluid opening for communicating with a second brake pipe from a tandem master cylinder of the brake fluid system of a vehicle The diagnostic valve further comprises a Tesla valve channel configured for connecting said first brake fluid opening with the second brake fluid opening. The Tesla valve channel comprises at least a series of Tesla valve units, each Tesla valve unit having a forward configuration, and a reverse configuration. The series of Tesla valve units has been formed by consecutively connecting each other of the Tesla valve units which have been arranged with the forward configuration towards the second brake fluid opening. The series of Tesla valve units defines a forward direction of the Tesla valve channel from the first brake fluid opening to the second brake fluid opening, and a reverse direction from the second brake fluid opening to the first brake fluid opening. In one embodiment of the diagnostic valve according to the invention, the Tesla valve channel is configured such that the pressure flow of a brake fluid passing through the diagnostic valve: - in the forward direction the pressure flow is >30 [cm3 / s] at the second brake fluid opening at a differential pressure of 25 [bar], and - in the reverse direction the pressure flow is 13.5 [cm3 / s] ± 1 at the first brake fluid opening at a differential pressure of = 15 [bar]. In another embodiment of the diagnostic valve according to the invention, the Tesla valve channel is configured such that the pressure flow of a brake fluid passing through the diagnostic valve: - in the forward direction the pressure flow is >25 [cm3 / s] at said second brake fluid opening at a differential pressure of 25 [bar]; - in the forward direction the pressure flow is 7 [cm3 / s] ± 1.2 at the first brake fluid opening at a differential pressure of = 15 [bar]. In another embodiment of the diagnostic valve according to the invention, with reference with the Fig.3, the diagnostic valve consists of a cylindrical body, and said first brake fluid opening is arranged at one end of the cylindrical body, and the second brake fluid opening is arranged at the other end of the cylindrical body. The Tesla valve channel connecting the first brake fluid opening with the second brake fluid opening is arranged inside said cylindrical body along its longitudinal axis. In another embodiment of the diagnostic valve according to the invention the diameter of the cylindrical body is 9mm. In another embodiment of the diagnostic valve according to the invention, the number of Tesla valve units is nine Tesla valve units successively disposed along the forward direction of the Tesla valve channel, the diagnostic valve being mounted directly in a bore in one of the components of the brake system. In another embodiment of the diagnostic valve according to the invention, with reference with the Figure 4, the diagnostic valve comprises: a rolled cylindrical body, and a hollow shell configured to receive the cylindrical body in a close fit connection. The Tesla valve channel connecting first brake fluid opening with the second brake fluid opening is arranged on a generating line on the periphery of the rolled cylindrical body which is placed parallelly in respect to the central axis of the rolled cylindrical body. In another embodiment of the diagnostic valve according to the invention, the number of Tesla valve units comprises three Tesla valve units successively disposed along the forward direction of the Tesla valve channel. In another embodiment of the diagnostic valve according to the invention, the rolled cylindrical body has a diameter of 10 mm, and a length of 9mm. In another embodiment of the diagnostic valve according to the invention, the Tesla valve channel comprises six series of Tesla valve units placed on generating lines on the periphery of the rolled cylindrical body paralelly in respect to the central axis of the rolled cylindrical body, said six series of Tesla valve units being connected at one end with the first brake fluid opening, and at the another end with the second brake fluid opening. The series of Tesla valve units has been formed by consecutively connecting each other of the Tesla valve units which have been arranged with the forward configuration towards the second brake fluid opening. The series of Tesla valve units defines a forward direction of the Tesla valve channel from the first brake fluid opening to the second brake fluid opening, and a reverse direction from the second brake fluid opening to the first brake fluid opening. In another embodiment of the diagnostic valve according to the invention, the diameter of the Tesla valve channel is 0,8mm. The temperature range is geometrically compensated in a suitable way. The diagnostic valve according to any embodiment of the invention is installed very easily being mounted in the appropriate position in the hydraulic component of the brake system by means of simple crimping. The diagnostic valve of any embodiment of the invention can be manufactured from many materials. In one preferred example, the diagnostic valve is made of plastic material. In a second aspect it is provided a brake system comprising the diagnostic valve in any of its embodiments. The brake system comprising the diagnostic valve of the invention has the advantage that is more robust and that its overall size is less bulky as compared with the brake system of prior art due to the compactness and reduced size of the diagnostic valve. While the description is made with reference to preferred embodiments, it will be understood that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the claims.

Claims

1. Diagnostic valve for a brake system of a vehicle comprising:- a first brake fluid opening for communicating with a first brake line from a reservoir of a brake fluid system;- a second brake fluid opening for communicating with a second brake line from a tandem master cylinder of said brake fluid system;- a Tesla valve channel configured for connecting said first brake fluid opening with the second brake fluid opening, said Tesla valve channel comprising at least a series of Tesla valve units, each Tesla valve unit having a forward configuration, and a reverse configuration, said at least a series of Tesla valve units being formed by consecutively connecting each other of the Tesla valve units arranged with the forward configuration towards the second brake fluid opening thus defining a forward direction of the Tesla valve channel from the first brake fluid opening to the second brake fluid opening, and a reverse direction from the second brake fluid opening to the first brake fluid opening.

2. Diagnostic valve for a brake system according to the claim 1 wherein the Tesla valve channel is configured such that the pressure flow of a brake fluid passing through the diagnostic valve:- in the forward direction the pressure flow is >30 [cm3 / s] at the second brake fluid opening at a differential pressure of 25 [bar], and- in the reverse direction the pressure flow is 13.5 [cm3 / s] ± 1 at the first brake fluid opening at a differential pressure of = 15 [bar],3. Diagnostic valve for a brake system according to the claim 1 wherein the Tesla valve channel is configured such that the pressure flow of a brake fluid passing through the diagnostic valve:- in the forward direction the pressure flow is >25 [cm3 / s] at said second brake fluid opening at a differential pressure of 25 [bar], and- in the reverse direction the pressure flow is 7 [cm3 / s] ± 1.2 at the first brake fluid opening at a differential pressure of = 15 [bar].

4. Diagnostic valve for a brake system according to any preceding claim, wherein:- the diagnostic valve consists of a cylindrical body, and said first brake fluid opening is arranged at one end of the cylindrical body, and the second brake fluid opening is arranged at the other end of the cylindrical body; and- the Tesla valve channel connecting the first brake fluid opening with the second brake fluid opening is arranged inside said cylindrical body along its longitudinal axis.

5. Diagnostic valve for a brake system according to claim 4 wherein the number of Tesla valve units is nine Tesla valve units successively disposed along the forward direction of the Tesla valve channel.

6. Diagnostic valve for a brake system according to claim 4 or 5 wherein said cylindrical body has a diameter of 9mm.

7. Diagnostic valve for a brake system according to claims from 1 to 3 wherein the diagnostic valve comprises:- a rolled cylindrical body, and- a hollow shell configured to receive the cylindrical body in a close fit connection wherein the Tesla valve channel connecting first brake fluid opening with the second brake fluid opening is arranged on a generating line on the periphery of the rolled cylindrical body, said Tesla valve channel being placed paralelly in respect to the central axis of the rolled cylindrical body.

8. Diagnostic valve for a brake system according to claim 7 wherein the number of Tesla valve units is three Tesla valve units successively disposed along the forward direction of the Tesla valve channel.

9. Diagnostic valve for a brake system according to claim 8 wherein the Tesla valve channel comprises six series of Tesla valve units placed on generating lines on the periphery of the rolled cylindrical body paralelly in respect to the central axis of the rolled cylindrical body, said six series of Tesla valve units being connected at one end with the first brake fluid opening, and at the another end with the second brake fluid opening.

10. Diagnostic valve for a brake system according to claims from 7 to 9 wherein the rolled cylindrical body has a diameter of 10mm, and a length of 9mm.

11. Diagnostic valve for a brake system according to any preceding claim, wherein the diameter of the Tesla valve channel is 0,8mm.

12. Diagnostic valve for a brake system according to any preceding claim, wherein the material of the diagnostic valve is plastic.

13. Brake system comprising the diagnostic valve according to any preceding claim.

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