CN113065092A - Method for calculating volume of brake vacuum tank - Google Patents
Method for calculating volume of brake vacuum tank Download PDFInfo
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- CN113065092A CN113065092A CN202110238473.5A CN202110238473A CN113065092A CN 113065092 A CN113065092 A CN 113065092A CN 202110238473 A CN202110238473 A CN 202110238473A CN 113065092 A CN113065092 A CN 113065092A
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Abstract
The invention discloses a method for calculating the volume of a brake vacuum tank, which analyzes the changes of the volumes and pressures in a brake booster and the brake vacuum tank in the primary braking process according to an ideal gas equation, derives a brake vacuum tank volume calculation formula, and then introduces set conditions to obtain the volume value of the brake vacuum tank. The subsequent vehicle type can be preset with a target value and then is led into the calculation method to obtain a volume calculation value, so that a design basis is provided for the development of the subsequent brake vacuum tank.
Description
Technical Field
The invention relates to a method for calculating the volume of a brake vacuum tank.
Background
At present, a brake vacuum tank is widely applied to an electric vehicle as a storage vacuum source device. The electric vehicle can consume a certain vacuum degree in the process of primary braking, and the braking vacuum tank can compensate the consumed vacuum degree, so that the starting frequency of the vacuum pump is reduced, and the service life of the vacuum pump is prolonged.
The larger the brake vacuum tank volume is, the higher the vacuum degree that can be stored is, but the brake vacuum tank volume needs to be calculated clearly because of the limitation of the cabin space.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a braking vacuum tank volume calculation method, which provides a design basis for the subsequent braking vacuum tank development.
The purpose of the invention is realized by the following technical scheme:
a braking vacuum tank volume calculation method comprises the following steps:
step one, deducing a calculation formula of the volume of the brake vacuum tank according to an ideal gas state equation:
1.1) analyzing the pressure and volume changes of a front cavity, a rear cavity and a brake vacuum tank in a brake booster in the primary braking process of a vehicle;
1.2) according to the analysis result in the step 1), combining an ideal gas state equation, deducing a calculation formula of the volume of the brake vacuum tank;
and step two, substituting the deceleration target value and the vacuum pump working threshold value into the braking vacuum tank volume calculation formula deduced in the step one to calculate the braking vacuum tank volume value.
2.1) defining the deceleration condition to be achieved by the vehicle during a braking operation;
2.2) setting a deceleration target value and a vacuum pump working threshold value of the vehicle in the primary braking process according to the deceleration condition;
and 2.3) substituting the deceleration target value and the vacuum pump working threshold value into a braking vacuum tank volume calculation formula to obtain a braking vacuum tank volume value.
Further, in step 1.1), the pressure and volume changes of the front cavity, the rear cavity and the brake vacuum tank in the brake booster during the primary braking process of the vehicle include:
(1) before the brake pedal is stepped on, the diaphragm does not move, and the effective volume in the booster is Vz;
(2) when a brake pedal is stepped, the diaphragm moves, the volumes of the front cavity and the rear cavity are changed, the front cavity and the rear cavity are not communicated, the volume of the front cavity is Vn, the volume of the rear cavity is (Vz-Vn), and the pressure intensity Pn in the vacuum tank is increased;
(3) the front and rear cavities are communicated, and the rear cavity is isolated from the atmosphere.
Further, in step 1.2), the ideal gas state equation is:
PV＝nRT。
in the formula:
p-ideal gas pressure;
v-ideal gas volume;
n-amount of gaseous species;
r is the ideal gas constant;
t-the thermodynamic temperature of the ideal gas.
Further, in step 1.2), the process of deriving the calculation formula of the brake vacuum tank volume Vg is as follows:
before the brake pedal is stepped on, the diaphragm does not move, the effective volume in the booster is Vz, the vacuum pump closing threshold Pgmin is 30kPa, and the gas state can be obtained according to an ideal gas state equation PV which is nrT:
(Vg+Vz)*Pgmin＝nRT (1)
when the brake pedal is depressed, under the deceleration condition, the front chamber volume is Vn, the rear chamber volume is (Vz-Vn), and the pressure Pn in the vacuum tank is obtained according to the ideal gas state equation PV — nRT:
(Vg+Vn)*Pn＝nRT (2)
(Vg+Vn)*Pn+Po*(Vz-Vn)＝n1RT (3)
the front cavity and the rear cavity are communicated, a vacuum pump is started to have a threshold value Pgmax, and the threshold value Pgmax can be obtained according to an ideal gas state equation PV ═ nRT:
(Vg+Vz)*Pgmax＝n1RT (4)
combining formulae (1) to (4), we obtain:
(Vg+Vz)*Pgmax＝(Vg+Vz)*Pgmin+(Vz-Vn)*Po
namely:
Vg＝(Vz*Pgmin+(Vz-Vn)*Po-Vz*Pgmax)/(Pgmax-Pgmin)。
further, in the 2.1), the deceleration condition is: under the condition that the vehicle reaches 0.3g deceleration in the primary braking process, the vacuum degree of the brake vacuum tank can compensate the vacuum degree consumed by the brake booster, and the vacuum pump does not intervene in the operation.
The invention has the following advantages:
the invention provides a method for calculating the volume of a brake vacuum tank, which analyzes the changes of the volumes and pressures in a brake booster and the brake vacuum tank in the primary braking process according to an ideal gas equation, derives a brake vacuum tank volume calculation formula, and then introduces set conditions to obtain the volume value of the brake vacuum tank. The subsequent vehicle type can be preset with a target value and then is led into the calculation method to obtain a volume calculation value, so that a design basis is provided for the development of the subsequent brake vacuum tank.
Drawings
FIG. 1 is a schematic view of the volume and pressure of the air in the brake booster and brake vacuum canister before the brake pedal is depressed;
FIG. 2 is a schematic diagram of the volume and pressure of the air in the brake booster and brake vacuum canister as the brake pedal moves to the end (0.3g deceleration);
FIG. 3 is a schematic diagram of the volume and pressure of the brake booster and the brake vacuum reservoir when the brake pedal is returned.
In the figure:
1-vacuum tank;
2-a booster;
3-a membrane.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention.
A braking vacuum tank volume calculation method comprises the following steps:
step one, deducing a calculation formula of the volume of the brake vacuum tank according to an ideal gas state equation:
1.1) analyzing the pressure and volume changes of a front cavity, a rear cavity and a brake vacuum tank in a brake booster in the primary braking process of a vehicle;
1.2) according to the analysis result in the step 1), combining an ideal gas state equation, deducing a calculation formula of the volume of the brake vacuum tank;
and step two, substituting the deceleration target value and the vacuum pump working threshold value into the braking vacuum tank volume calculation formula deduced in the step one to calculate the braking vacuum tank volume value.
2.1) defining the deceleration condition to be achieved by the vehicle during a braking operation;
2.2) setting a deceleration target value and a vacuum pump working threshold value of the vehicle in the primary braking process according to the deceleration condition;
and 2.3) substituting the deceleration target value and the vacuum pump working threshold value into a braking vacuum tank volume calculation formula to obtain a braking vacuum tank volume value.
Further, as shown in fig. 1 to 3, in step 1.1), the pressure and volume changes in the front and rear chambers and the brake vacuum tank in the brake booster during a braking process of the vehicle include:
(1) before the brake pedal is stepped on, the diaphragm does not move, and the effective volume in the booster is Vz;
(2) when a brake pedal is stepped, the diaphragm moves, the volumes of the front cavity and the rear cavity are changed, the front cavity and the rear cavity are not communicated, the volume of the front cavity is Vn, the volume of the rear cavity is (Vz-Vn), and the pressure intensity Pn in the vacuum tank is increased;
(3) the front and rear cavities are communicated, and the rear cavity is isolated from the atmosphere.
Further, in step 1.2), the ideal gas state equation is:
PV＝nRT。
in the formula:
p-ideal gas pressure;
v-ideal gas volume;
n-amount of gaseous species;
r is the ideal gas constant;
t-the thermodynamic temperature of the ideal gas.
Further, in step 1.2), the process of deriving the calculation formula of the brake vacuum tank volume Vg is as follows:
before the brake pedal is stepped on, the diaphragm does not move, the effective volume in the booster is Vz, the vacuum pump closing threshold Pgmin is 30kPa, and the gas state can be obtained according to an ideal gas state equation PV which is nrT:
(Vg+Vz)*Pgmin＝nRT (1)
when the brake pedal is depressed, under the deceleration condition, the front chamber volume is Vn, the rear chamber volume is (Vz-Vn), and the pressure Pn in the vacuum tank is obtained according to the ideal gas state equation PV — nRT:
(Vg+Vn)*Pn＝nRT (2)
(Vg+Vn)*Pn+Po*(Vz-Vn)＝n1RT (3)
the front cavity and the rear cavity are communicated, a vacuum pump is started to have a threshold value Pgmax, and the threshold value Pgmax can be obtained according to an ideal gas state equation PV ═ nRT:
(Vg+Vz)*Pgmax＝n1RT (4)
combining formulae (1) to (4), we obtain:
(Vg+Vz)*Pgmax＝(Vg+Vz)*Pgmin+(Vz-Vn)*Po
namely:
Vg＝(Vz*Pgmin+(Vz-Vn)*Po-Vz*Pgmax)/(Pgmax-Pgmin)。
further, in the 2.1), the deceleration condition is: under the condition that the vehicle reaches 0.3g deceleration in the primary braking process, the vacuum degree of the brake vacuum tank can compensate the vacuum degree consumed by the brake booster, and the vacuum pump does not intervene in the operation.
Examples
Certain vacuum degree can be consumed in the primary braking process of the automobile brake pedal, and the brake vacuum tank is used as a storage vacuum source device and can compensate the vacuum degree consumed in the process of stepping on the brake pedal, so that the starting frequency of the vacuum pump is reduced, and the purpose of prolonging the service life of the vacuum pump is achieved.
1. Theoretical basis
The theoretical basis for the calculation of the volume of the brake vacuum tank is an ideal gas state equation, which is a state equation describing the relationship among pressure, volume, mass and temperature when the ideal gas is in an equilibrium state, and the equation is PV ═ nRT.
In the formula:
p-ideal gas pressure;
v-ideal gas volume;
n-amount of gaseous species;
r is the ideal gas constant;
t-the thermodynamic temperature of the ideal gas.
2. Design objective
Taking a certain electric vehicle model as an example, the following design targets are defined: under the condition that the vehicle reaches 0.3g deceleration in the primary braking process, the vacuum degree of the brake vacuum tank can compensate the vacuum degree consumed by the brake booster, and the vacuum pump does not intervene in the operation.
3. Known conditions
Taking a certain electric vehicle model as an example, specific parameters are shown in table 1:
TABLE 1
4. Process calculation
As shown in fig. 1 to 3, the volume and pressure changes of the air in the brake booster and the brake vacuum tank during one braking process are shown.
Before the brake pedal is stepped on, the diaphragm does not move, the effective volume in the booster is Vz, the vacuum pump closing threshold Pgmin is 30kPa, and the vacuum pump closing threshold is nRT according to the formula PV
(Vg+Vz)*Pgmin＝nRT (1)
When the brake pedal is stepped on, under the condition of obtaining 0.3g deceleration, the diaphragm moves, the volumes of the front cavity and the rear cavity are changed, the front cavity and the rear cavity are not communicated, the volume of the front cavity is Vn, the volume of the rear cavity is (Vz-Vn), and the pressure Pn in the vacuum tank is high.
According to the formula PV ═ nRT
(Vg+Vn)*Pn＝nRT (2)
(Vg+Vn)*Pn+Po*(Vz-Vn)＝n1RT (3)
The front cavity and the rear cavity are communicated, the rear cavity is isolated from the atmosphere, the vacuum pump is started to have a threshold value Pgmax, and the threshold value Pgmax is n RT according to a formula PV
(Vg+Vz)*Pgmax＝n1RT (4)
Combining formulae (1) to (4), we obtain:
(Vg+Vz)*Pgmax＝(Vg+Vz)*Pgmin+(Vz-Vn)*Po
namely:
Vg＝(Vz*Pgmin+(Vz-Vn)*Po-Vz*Pgmax)/(Pgmax-Pgmin)
substituting the known conditions in table 1 yields Vg ═ 1.2L.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (5)
1. A method for calculating the volume of a brake vacuum tank is characterized by comprising the following steps:
step one, deducing a calculation formula of the volume of the brake vacuum tank according to an ideal gas state equation:
1.1) analyzing the pressure and volume changes of a front cavity, a rear cavity and a brake vacuum tank in a brake booster in the primary braking process of a vehicle;
1.2) according to the analysis result in the step 1), combining an ideal gas state equation, deducing a calculation formula of the volume of the brake vacuum tank;
and step two, substituting the deceleration target value and the vacuum pump working threshold value into the braking vacuum tank volume calculation formula deduced in the step one to calculate the braking vacuum tank volume value.
2.1) defining the deceleration condition to be achieved by the vehicle during a braking operation;
2.2) setting a deceleration target value and a vacuum pump working threshold value of the vehicle in the primary braking process according to the deceleration condition;
and 2.3) substituting the deceleration target value and the vacuum pump working threshold value into a braking vacuum tank volume calculation formula to obtain a braking vacuum tank volume value.
2. A method for calculating the volume of a brake vacuum tank according to claim 1, wherein in the step 1.1), the pressure and volume changes in the front and rear chambers of the brake booster and the brake vacuum tank during a braking process of the vehicle comprise:
(1) before the brake pedal is stepped on, the diaphragm does not move, and the effective volume in the booster is Vz;
(2) when a brake pedal is stepped, the diaphragm moves, the volumes of the front cavity and the rear cavity are changed, the front cavity and the rear cavity are not communicated, the volume of the front cavity is Vn, the volume of the rear cavity is (Vz-Vn), and the pressure intensity Pn in the vacuum tank is increased;
(3) the front and rear cavities are communicated, and the rear cavity is isolated from the atmosphere.
3. A brake vacuum canister volume calculation method as claimed in claim 2, characterized in that in step 1.2), the ideal gas state equation is:
PV＝nRT。
in the formula:
p-ideal gas pressure;
v-ideal gas volume;
n-amount of gaseous species;
r is the ideal gas constant;
t-the thermodynamic temperature of the ideal gas.
4. A brake vacuum canister volume calculation method according to claim 3, characterized in that in step 1.2), the derivation of the calculation formula for the brake vacuum canister volume Vg is carried out by:
before the brake pedal is stepped on, the diaphragm does not move, the effective volume in the booster is Vz, the vacuum pump closing threshold Pgmin is 30kPa, and the gas state can be obtained according to an ideal gas state equation PV which is nrT:
when the brake pedal is depressed (Vg + Vz) × Pgmin ═ nRT (1), under the deceleration condition, the front chamber volume is Vn, the rear chamber volume is (Vz-Vn), the pressure Pn in the vacuum tank is obtained according to the ideal gas state equation PV ═ nRT:
(Vg+Vn)*Pn＝nRT (2)
(Vg+Vn)*Pn+Po*(Vz-Vn)＝n1RT (3)
the front cavity and the rear cavity are communicated, a vacuum pump is started to have a threshold value Pgmax, and the threshold value Pgmax can be obtained according to an ideal gas state equation PV ═ nRT:
(Vg+Vz)*Pgmax＝n1RT (4)
combining formulae (1) to (4), we obtain:
(Vg+Vz)*Pgmax＝(Vg+Vz)*Pgmin+(Vz-Vn)*Po
namely:
Vg＝(Vz*Pgmin+(Vz-Vn)*Po-Vz*Pgmax)/(Pgmax-Pgmin)。
5. a brake vacuum tank volume calculation method according to claim 1, characterized in that in 2.1), the deceleration condition is: under the condition that the vehicle reaches 0.3g deceleration in the primary braking process, the vacuum degree of the brake vacuum tank can compensate the vacuum degree consumed by the brake booster, and the vacuum pump does not intervene in the operation.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101423055A (en) * | 2008-11-11 | 2009-05-06 | 吉林大学 | Electric brake operation system of hybrid powder sedan regenerative braking system |
| CN103268404A (en) * | 2013-04-27 | 2013-08-28 | 奇瑞汽车股份有限公司 | Method and device for selecting vacuum pump and vacuum tank included in vacuum braking system |
| CN105404782A (en) * | 2015-11-27 | 2016-03-16 | 郑州比克新能源汽车有限公司 | Calculation method of vacuum degree in car braking process |
| JP2018040671A (en) * | 2016-09-07 | 2018-03-15 | 中日本高速技術マーケティング株式会社 | Method of estimating cavity volume in concrete structure |
-
2021
- 2021-03-04 CN CN202110238473.5A patent/CN113065092A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101423055A (en) * | 2008-11-11 | 2009-05-06 | 吉林大学 | Electric brake operation system of hybrid powder sedan regenerative braking system |
| CN103268404A (en) * | 2013-04-27 | 2013-08-28 | 奇瑞汽车股份有限公司 | Method and device for selecting vacuum pump and vacuum tank included in vacuum braking system |
| CN105404782A (en) * | 2015-11-27 | 2016-03-16 | 郑州比克新能源汽车有限公司 | Calculation method of vacuum degree in car braking process |
| JP2018040671A (en) * | 2016-09-07 | 2018-03-15 | 中日本高速技術マーケティング株式会社 | Method of estimating cavity volume in concrete structure |
Non-Patent Citations (1)
| Title |
|---|
| 孙东睿: "电动汽车真空助力制动系统匹配技术研究", 《中国优秀博硕士学位论文全文数据库(硕士)工程科技Ⅱ辑》 * |
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Application publication date: 20210702 |
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