Brake fluid for one-box brake-by-wire system and preparation method thereof

Abstract

The application discloses brake fluid for One-Box brake-by-wire system and a preparation method thereof, the brake fluid comprises triethylene glycol monomethyl ether borate, glycerol acid ester, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, diethylene glycol, anti-rust agent, antioxidant and pH value regulator. The brake fluid can reduce the friction coefficient to <=0.14 under the SRV test condition, the friction coefficient is reduced by 10% compared with that of traditional brake fluid, the abnormal sound and wear problem caused by poor lubrication of the brake system is effectively solved, and the reliability and safety of the brake system of the new energy vehicle are remarkably improved; in addition, the brake fluid also has low temperature kinetic viscosity (-40 DEG C) <=1000mm 2 / s, the pH value is controlled to be 7.5-8.0, and excellent corrosion prevention performance of the product is ensured.

Description

Technical Field

[0001] This invention belongs to the field of brake fluid technology, and particularly relates to a brake fluid for a One-Box brake-by-wire system and its preparation method. Background Technology

[0002] One-Box is a technical solution for hydraulic brake-by-wire (EHB) systems, integrating the electronic power steering and ESC / ABS functions into a single unit. It replaces the cumbersome physical transmission with electronic signals, combining two previously separate core components into a compact module. This design offers advantages such as fast response, high integration, low cost, and efficient energy recovery to increase range, making it the preferred solution for current new energy vehicles, especially intelligent vehicles. The One-Box system contains multiple friction pairs, including the motor drive mechanism, solenoid valve core and body, seals and cylinder, all lubricated by brake fluid. However, existing brake fluid standards (such as Class 4, Class 5.1, and Class 6) primarily focus on basic properties like boiling point and low-temperature viscosity, without specifying lubrication performance. This leads to insufficient lubrication in practical applications, causing abnormal wear of the friction pairs, resulting in abnormal noises and affecting driving comfort and system lifespan. Furthermore, with the increasing demands on NVH performance from new energy vehicles, and the frequent start-stop characteristics of One-Box systems in autonomous driving scenarios, higher requirements are placed on the tribological performance of brake fluid.

[0003] Currently, commercially available brake fluids mainly fall into three categories: alcohol ether type, borate ester type, and silane oil type. While existing borate ester type brake fluids possess excellent high-temperature anti-vapor resistance, their lubrication performance is generally low. According to SRV (Optimol SRV®) high-frequency linear vibration friction and wear test data, the average coefficient of friction for commercially available Class 4 brake fluids is typically in the range of 0.15-0.18. Under the high-frequency operating conditions of the brake master cylinder and wheel cylinders in new energy vehicles, a high coefficient of friction can easily induce a stick-slip effect between the piston and cylinder, leading to problems such as brake squealing and low-frequency creeping noise. These NVH (noise, vibration, and harshness) problems not only affect driving comfort but can also cause abnormal wear of braking system components, shortening their service life.

[0004] To address the aforementioned issues, there is an urgent need to develop a novel brake fluid formulation that combines excellent low-temperature resistance, stable lubrication performance, and reliable corrosion resistance. This would solve the problem of abnormal noises caused by insufficient lubrication performance in existing brake fluids and meet the practical application requirements of brake fluid in the One-Box brake-by-wire system of new energy vehicles. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a brake fluid for a One-Box brake-by-wire system, so as to reduce the friction coefficient of the brake fluid, improve the lubrication performance of the brake fluid, and effectively solve the problems of abnormal noise and wear caused by poor lubrication in the One-Box system.

[0006] Technical solution: The brake fluid for the One-Box brake-by-wire system described in this invention comprises the following raw materials by mass fraction: 65-75% triethylene glycol monomethyl ether borate, 0.5-1% glyceryl ester, 5-10% triethylene glycol monobutyl ether, 15-20% tetraethylene glycol monomethyl ether, 2-5% diethylene glycol, 0.2-0.5% rust inhibitor, 0.2-0.4% antioxidant, and 0.4-0.8% pH adjuster.

[0007] Furthermore, the boron content in the brake fluid of the present invention is 1.1-1.3%.

[0008] Furthermore, the glyceryl ester used in the brake fluid of the present invention is selected from glyceryl monooleate and / or glyceryl monoricinoleate.

[0009] Furthermore, the rust inhibitor used in the brake fluid of the present invention includes triethanolamine oleate and benzotriazole in a mass ratio of (1.5-2):1.

[0010] Furthermore, the antioxidant used in the brake fluid of the present invention is selected from 2,6-di-tert-butyl-p-cresol or 2,2-bis(4-hydroxyphenyl)propane.

[0011] Furthermore, the pH adjuster used in the brake fluid of the present invention is selected from diethanolamine or diisopropanolamine.

[0012] The method for preparing the above-mentioned brake fluid according to the present invention includes the following steps:

[0013] (1) Mix and stir triethylene glycol monomethyl ether borate, triethylene glycol monobutyl ether and tetraethylene glycol monomethyl ether in a closed, inert atmosphere for 10-15 min;

[0014] (2) Add glyceryl ester, diethylene glycol, rust inhibitor and antioxidant and continue stirring for 15-20 minutes;

[0015] (3) Add pH adjuster and continue stirring for 10-15 minutes to obtain brake fluid.

[0016] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are:

[0017] (1) Under SRV test conditions (load 300N, amplitude 1mm, frequency 50Hz, temperature 80℃, time 2h), the friction coefficient of this brake fluid can be reduced to ≤0.14, which is 10% lower than that of traditional brake fluid; that is, it has a lower friction coefficient, which reduces the friction coefficient and wear of internal friction of the brake fluid and multiple friction components (including motor transmission mechanism, gear rack, solenoid valve core, piston seal, etc.), which not only effectively improves the mechanical efficiency of the system, but also effectively solves the abnormal noise and wear problems caused by poor lubrication of the One-Box system, and improves the NVH performance and driving comfort of the whole vehicle;

[0018] (2) The brake fluid uses tetraethylene glycol monomethyl ether as a diluent. Compared with the traditional diethylene glycol monomethyl ether or triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether has a longer carbon chain and more ether oxygen bonds. While providing excellent solubility, it can effectively improve the low-temperature fluidity of the brake fluid. The low-temperature kinematic viscosity (-40℃) is ≤1000mm² / s.

[0019] (3) The brake fluid controls the pH value at 7.5-8.0 to ensure that the product has excellent anti-corrosion performance and will not affect styrene-butadiene rubber and ethylene propylene diene monomer rubber. It effectively avoids the risk of brake fluid leakage and system pressure drop caused by seal failure, and ensures the long-term sealing reliability of the One-Box system.

[0020] (4) The preparation process of the brake fluid is carried out in a closed system and inert atmosphere to effectively isolate oxygen and prevent the components from oxidizing and deteriorating. At the same time, the moisture content of the finished product is controlled below 0.1%, thereby ensuring the excellent quality and long-term stability of the brake fluid and improving the high temperature resistance of the brake fluid. Attached Figure Description

[0021] Figure 1 The diagram shows a comparison of the SRV friction coefficients of the low-friction coefficient brake fluid of Example 1 and existing commercially available brake fluids. The commercially available brake fluids are those that meet the HZY 4 specification in GB 12981-2012, i.e., basic brake fluid products. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0023] It should be noted that all raw materials used in this invention are commercially available. The information on the raw materials or their sources of purchase involved in the embodiments is shown in Table 1 below.

[0024] Table 1 Raw material information or purchase source

[0025]

[0026] Basic brake fluid products: We currently offer brake fluids that meet the HZY4 specification in GB 12981-2012. The B content in this basic brake fluid product is 0.6804%, and the raw material composition formula is shown in Table 2 below.

[0027] Table 2. Basic Brake Fluid Product Raw Material Component Formulation

[0028]

[0029] Example 1

[0030] The brake fluid raw material composition for the One-Box brake-by-wire system in Example 1 is shown in Table 3 below.

[0031] Table 3 Brake fluid raw material composition of Example 1

[0032]

[0033] The method for preparing the brake fluid in Example 1 includes the following steps:

[0034] (1) Add triethylene glycol monomethyl ether borate, triethylene glycol monobutyl ether and tetraethylene glycol monomethyl ether into the mixing vessel according to the ratio, and stir for 15 min under a sealed and nitrogen-filled environment;

[0035] (2) Add diethylene glycol, rust inhibitor, antioxidant and glyceryl ester and continue stirring for 20 minutes;

[0036] (3) Finally, add pH adjuster and continue stirring for 15 minutes to obtain brake fluid.

[0037] The brake fluid from Example 1 and a commercially available base brake fluid product were tested for their SRV (Self-Rating Variation) coefficient of friction. The results are as follows: Figure 1 As shown, with the increase of time, the friction coefficient of the product of Example 1 is significantly lower than that of commercially available products. It can also be seen that the friction coefficient of the product of Example 1 tends to stabilize at 0.12 with the increase of time, while the friction coefficient of the base brake fluid product continues to increase until it exceeds 0.15.

[0038] Comparative Example 1

[0039] Comparative Example 1, based on the conditions of the base brake fluid product, increases the borate ester content to meet the borate ester content standard of Example 1, but glyceryl esters are not added to the brake fluid raw materials. The specific raw material components are shown in Table 4 below, and the preparation method is the same as in Example 1.

[0040] Table 4 Brake fluid raw material composition of Comparative Example 1

[0041]

[0042] Comparative Example 2

[0043] Comparative Example 2 is based on the conditions of the base brake fluid product, with the same amount of glyceryl ester as in Example 1 added, but the content of borate ester in the brake fluid raw materials is not increased. The specific raw material components are shown in Table 5 below, and the preparation method is the same as in Example 1.

[0044] Table 5 Brake fluid raw material composition of Comparative Example 2

[0045]

[0046] Comparative Example 3

[0047] Comparative Example 3, based on the conditions of the base brake fluid product, adds twice the amount of glyceryl ester as in Example 1, but does not increase the content of borate ester in the brake fluid raw materials. The specific raw material components are shown in Table 6 below, and the preparation method is the same as in Example 1.

[0048] Table 6 Brake fluid raw material composition of Comparative Example 3

[0049]

[0050] Comparative Example 4

[0051] Comparative Example 4, based on the conditions of the base brake fluid product, adds the same amount of glyceryl ester and phosphate ester as in Example 1, but does not increase the content of borate ester in the brake fluid raw materials. The specific raw material components are shown in Table 7 below, and the preparation method is the same as in Example 1.

[0052] Table 7 Brake fluid raw material composition of Comparative Example 4

[0053]

[0054] Example 2

[0055] The brake fluid raw material composition for the One-Box brake-by-wire system in Example 2 is shown in Table 8 below. The preparation method is the same as in Example 1.

[0056] Table 8 Brake fluid raw material composition of Example 2

[0057]

[0058] Comparative Example 5

[0059] Comparative Example 5, based on the conditions of the base brake fluid product, adds twice the amount of glyceryl ester as in Example 2, but does not increase the content of borate ester in the brake fluid raw materials. The specific raw material components are shown in Table 9 below, and the preparation method is the same as in Example 2.

[0060] Table 9 Brake fluid raw material composition of Comparative Example 5

[0061]

[0062] Comparative Example 6

[0063] Comparative Example 6, based on the conditions of the base brake fluid product, adds the same amount of glyceryl ester and phosphate ester as in Example 2, but does not increase the content of borate ester in the brake fluid raw materials. The specific raw material components are shown in Table 10 below, and the preparation method is the same as in Example 2.

[0064] Table 10 Brake fluid raw material composition of Comparative Example 6

[0065]

[0066] Example 3

[0067] The brake fluid raw material composition for the One-Box brake-by-wire system in Example 3 is shown in Table 11 below. The preparation method is the same as in Example 1.

[0068] Table 11 Brake fluid raw material composition of Example 3

[0069]

[0070] Performance testing

[0071] The brake fluids prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were tested for their physicochemical properties according to the test methods in Table 12. The specific properties are shown in Tables 12, 13 and 14.

[0072] Table 12 Performance data of the embodiments

[0073]

[0074] Table 13 Performance Comparison of Example 1, Comparative Examples 1 to 4

[0075]

[0076] Table 14 Performance comparison of Example 2 and Comparative Examples 5 and 6

[0077]

[0078] As shown in Table 12, the product of this invention has a high dry and wet equilibrium reflux boiling point, a high boron content, and an SRV friction coefficient of less than 0.14. This verifies that the product of this invention has excellent anti-wear performance, and no abnormal noise was observed in the braking system after actual vehicle testing. This effectively solves the problem of abnormal noise and wear caused by poor lubrication in the One-Box system, and improves the NVH performance and driving comfort of the entire vehicle.

[0079] Furthermore, as shown in Tables 13 and 14, when preparing brake fluid, simply increasing the boron content, adding a single friction modifier, further increasing the content of the friction modifier, or using a compound friction modifier, based on the basic brake fluid product, cannot significantly reduce the friction coefficient and thus solve the problem of abnormal noise caused by poor lubrication. Only by increasing the boron content and adding a small amount of friction modifier can the synergistic effect of the two significantly reduce the friction coefficient and solve the abnormal noise and wear problems of the One-Box system.

[0080] In addition to the above embodiments, it should be noted that the technical effects claimed above can be obtained by using the components and their mass fraction range of the present invention, and therefore no further experimental verification is required.

Claims

1. A brake fluid for a One-Box brake-by-wire system, characterized in that, The product comprises the following raw materials by mass fraction: 65-75% triethylene glycol monomethyl ether borate, 0.5-1% glyceryl ester, 5-10% triethylene glycol monobutyl ether, 15-20% tetraethylene glycol monomethyl ether, 2-5% diethylene glycol, 0.2-0.5% rust inhibitor, 0.2-0.4% antioxidant, and 0.4-0.8% pH adjuster.

2. The brake fluid for a One-Box brake-by-wire system according to claim 1, characterized in that, The brake fluid contains 1.1-1.3% boron.

3. The brake fluid for a One-Box brake-by-wire system according to claim 1, characterized in that, The glyceryl ester is selected from glyceryl monooleate and / or glyceryl monoricinoleate.

4. The brake fluid for a One-Box brake-by-wire system according to claim 1, characterized in that, The rust inhibitor comprises triethanolamine oleate and benzotriazole in a mass ratio of (1.5-2):

1.

5. The brake fluid for a One-Box brake-by-wire system according to claim 1, characterized in that, The antioxidant is selected from 2,6-di-tert-butyl-p-cresol or 2,2-bis(4-hydroxyphenyl)propane.

6. The brake fluid for a One-Box brake-by-wire system according to claim 1, characterized in that, The pH adjuster is selected from diethanolamine or diisopropanolamine.

7. A method for preparing the brake fluid according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Mix and stir triethylene glycol monomethyl ether borate, triethylene glycol monobutyl ether and tetraethylene glycol monomethyl ether in a closed, inert atmosphere for 10-15 min; (2) Add glyceryl ester, diethylene glycol, rust inhibitor and antioxidant and continue stirring for 15-20 minutes; (3) Add pH adjuster and continue stirring for 10-15 minutes to obtain brake fluid.

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