JPH08295230A - Controlling method for pump for use in negative-pressure brake - Google Patents

Abstract

PURPOSE: To efficiently perform forced drive of a pump at the recovery of negative pressure while eliminating the loss of time by detecting a pump application voltage during forced drive of the pump, and performing forced drive of the pump after failure judgment and only for negative-pressure charging completion time that is calculated from the detected pump application voltage. CONSTITUTION: Data on the relation between pump application voltage and forced pump drive time is stored in a ROM 6 of a control unit 1, and a pump application voltage detection signal is input to an input interface 2 along with a negative-pressure detection signal and a brake signal. The pump application voltage is detected at the timing of input of the brake signal by which a negative-pressure brake is turned on once, and negative pressure is built up by forcibly driving the pump for the forced pump drive time which corresponds to the pump application voltage at which the forced pump drive time corresponding to the detected pump application voltage is read from the ROM 6 into a CPU 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an electric pump for generating a negative pressure for operating a negative pressure brake (vacuum servo brake) mounted on an electric vehicle or the like,
In particular, it relates to a pump control method in an operation region where the negative pressure of the vacuum tank reaches the lower limit.

[0002]

2. Description of the Related Art A negative pressure brake mounted on an electric vehicle or the like operates by a negative pressure generated by an electric pump (vacuum pump) driven by applying a voltage to a main battery or an auxiliary battery of the electric vehicle. The negative pressure generated by the negative pressure brake pump is stored in a vacuum tank and given to the negative pressure brake. When negative pressure is stored in the vacuum tank up to a predetermined upper limit value, the negative pressure detection circuit system detects this and the pump stops, and when the vacuum tank negative pressure drops to a predetermined lower limit due to brake operation, etc. The negative pressure detection circuit system detects and the pump starts to drive again, and the negative pressure is raised to the upper limit value.

The negative pressure stored in the vacuum tank of the negative pressure brake is gradually reduced every time the negative pressure brake is turned on and off, and the braking ability of the negative pressure brake is gradually reduced.
Therefore, in order to maintain the braking ability of the negative pressure brake within an allowable range, a predetermined lower limit is set for the negative pressure, and this lower limit is detected by a negative pressure detection circuit system equipped with a linear sensor, a lower limit switch, etc. It controls the driving of the pump. There are various pump drive control methods that incorporate control means for dealing with a failure in the negative pressure detection circuit system.
One example thereof will be described with reference to FIGS.

FIG. 3 shows a control unit 1 of a microcomputer for controlling driving of an electric pump for negative pressure braking, and an input interface 2 of the microcomputer is provided with a negative pressure detection signal from a negative pressure detection circuit system and brake on / off. When a brake signal is input, the CPU 3 reads it and performs arithmetic processing on the data stored in the RAM 5 or ROM 6. C
When PU3 determines from the negative pressure detection signal that the negative pressure has reached the upper limit value, the pump stop signal is output and the pump stops. After the pump is stopped, the negative pressure brake is turned on and off several times to reduce the negative pressure, and when the CPU 3 determines from the negative pressure detection signal that the negative pressure has reached the lower limit value, the pump drive signal is output via the output interface 4. Outputs and the pump starts driving.

Starting the pump drive by detecting the lower limit of negative pressure
For example, the program shown in FIG. Pump control is started in step S1. In step S2, it is determined whether the pump is off, and if it is off, the process proceeds to step S3. In step S3, it is determined whether or not the lower limit of the negative pressure is detected. If it is determined that the lower limit is detected, the pump drive is started, and the process proceeds to the end of pump control in step S6. If it is determined in step S3 that the lower limit is not detected, the process proceeds to step S4, in which it is determined whether the negative pressure brake has been turned on / off a predetermined number of times (the number of times the negative pressure is equal to or lower than the lower limit). If it is determined in step S4 that the negative pressure brake has not been turned on / off a predetermined number of times, the process proceeds to step S6, and if it is determined that the negative pressure brake has been turned on / off a predetermined number of times or more, the process proceeds to step S5. Step S5
Then, although the negative pressure is equal to or lower than the lower limit, the lower limit of the negative pressure is not detected, and it is determined that the negative pressure detection circuit system has a failure, for example, a sensor failure, an alarm is displayed, and the process proceeds to step S6. A series of operations at the time of occurrence of a failure in the above steps S1 to S6 are shown in the waveform of FIG.

In step S5 of FIG. 5 (A), it is determined that the sensor has failed, and if it is left as it is, the pump drive is not restarted, the negative pressure is reduced, and the braking ability of the negative pressure brake is reduced. . It is FIG. 6A that avoids this negative pressure drop.
Is a control program at the time of sensor failure, and operates as follows.

When the current sensor failure control is started in step S7, it is determined in step S8 whether the negative pressure brake is turned on. If it is determined that the negative pressure brake is turned on once, the process proceeds to step S9 to force the pump. The driving is started, and the negative pressure is increased and the braking ability of the negative pressure brake is restored. If it is determined in step S8 that the brake is not turned on, the process proceeds to step S10, in which it is determined whether or not a predetermined time has elapsed by a timer or the like, and if the predetermined time has not elapsed, step S9 is performed. After that, the pump is continuously driven, and when a certain time has elapsed, the process proceeds to step S11 to stop the pump driving.

In the program of FIG. 6A, when the lower limit of the negative pressure is not detected due to a failure of the negative pressure detection circuit system, the pump is forcibly driven for a fixed time each time the negative pressure brake is turned on. This series of operations is shown in the waveform of FIG. 6 (B). The forced drive time of the pump driven by one ON operation of the negative pressure brake is regulated to a constant value for the following reason. That is, if the negative pressure detection circuit system malfunctions, even if the pump is forcibly driven and the negative pressure reaches the upper limit, the negative pressure upper limit is not detected, and the pump continues to be driven unnecessarily without stopping. Therefore, when the pump starts to be driven by one ON operation of the brake, the pump is forcibly driven for a fixed time in anticipation of the negative pressure filling completion time at which the negative pressure reaches a predetermined upper limit, and the pump is forcibly stopped after this fixed time elapses. There is.

[0009]

In a negative pressure brake pump driven by applying a voltage to a main battery or an auxiliary battery of an electric vehicle or the like, the voltage of the main battery fluctuates due to changes in operating conditions such as running of the electric vehicle. This voltage fluctuation directly changes the pump capacity. Therefore, when the pump applied voltage is increased, the pump capacity is increased to recover the negative pressure of the negative pressure brake early, and the negative pressure filling completion time from the start of pump driving until the negative pressure reaches the upper limit is shortened. On the contrary, when the voltage applied to the pump becomes low, the pump capacity is lowered, the rising speed of the negative pressure of the negative pressure brake becomes slow, and the negative pressure filling completion time becomes long. The relationship between the pump applied voltage and the negative pressure filling completion time is inversely proportional as shown by the solid line graph G1 in FIG.

As shown in FIG. 4, the negative pressure filling completion time Pn is the longest when the pump applied voltage is the minimum Va, and the load filling completion time Pm is the shortest when the applied voltage is the maximum Vb. Therefore, the fixed time set in step S10 of FIG. 6 (A) is set to the longest load filling completion time Pn of FIG. 4, and the fixed time T ′ is set at the position shown in the chain of FIG. 4, for example. It was The reason is that if the fixed time period T ′ is set shorter than the maximum load filling completion time period Pn, FIG.
When the pump is driven at the minimum applied voltage Va in step S9 of step 1, the driving is stopped for a fixed time T'before the load filling completion time Pn at this time is reached, the load does not rise to the upper limit, and the negative pressure brake is applied. This is because there is a problem that the braking ability of is not fully restored.

However, when the pump drive control is performed by setting the constant failure determination time T'as described above, there is not much problem when the pump applied voltage at the time of forced pump drive is low, but the higher the pump applied voltage is, the higher the pump applied voltage becomes. In addition, there is a problem in that the rate of waste of time for driving the pump unnecessarily long increases. For example, the difference between the load filling completion time Pm when the pump applied voltage is maximum Vb and the load filling completion time Pn when the pump applied voltage is minimum Va in FIG.
In the case of an ordinary electric vehicle, it takes about 20 seconds. In this case,
When the pump is forcibly driven by the negative pressure brake operation when the pump applied voltage is the maximum Vb, the time P at which the load charging is completed is completed.
The pump was stopped at a fixed time T ′ after about 20 seconds had passed from m, and the pump was unnecessarily driven for about 20 seconds.

An object of the present invention is to use the pump forcibly when recovering the negative pressure by forcibly driving the pump with a signal for turning on the negative pressure brake when the negative pressure detection circuit system fails. It is to do efficiently by omitting.

[0013]

DISCLOSURE OF THE INVENTION The present invention is a negative pressure filling in which an electric pump for generating a negative pressure for operating a negative pressure brake in an electric vehicle or the like is driven by a battery voltage to raise the negative pressure to a predetermined upper limit. After the completion time, the pump is stopped, and when the negative pressure drops to a predetermined lower limit after the pump is stopped, the pump is driven by the negative pressure lower limit detection signal at this time, and the negative pressure is set to a predetermined value after the pump is stopped. If the negative pressure lower limit detection signal is not obtained even if the pressure drops to the lower limit, it is determined that the negative pressure detection circuit system has failed, and the pump is forcibly driven from the ON operation signal of the negative pressure brake after this failure determination. In the pump control method, the pump applied voltage at the time of forced driving of the pump is detected, and the pump is forced after the failure determination for the negative pressure filling completion time obtained from the detected pump applied voltage. By that to perform the dynamic, it is to achieve the above object.

[0014]

When the electric pump that generates the negative pressure for operating the negative pressure brake is driven by the applied voltage of the battery voltage, the negative pressure filling completion time changes due to the fluctuation of the pump applied voltage. By setting the forced drive time of the negative pressure filling completion time based on the pump applied voltage, the forced pump drive time fluctuates according to the pump applied voltage fluctuation, and the forced drive of the pump during negative pressure brake operation is always the minimum. The optimum negative pressure filling completion time is obtained, and therefore, it is possible to execute without negative waste of time.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below with reference to FIGS. The graph G2 in FIG. 1 shows the relationship between the pump applied voltage and the forced pump drive time when controlling the forced drive of the negative pressure brake pump of the electric vehicle after the brake operation, and FIG. 2 shows the method of the present invention. A configuration example of a microcomputer that performs

In the method of the present invention, step S in FIG.
The forced pump drive time after the negative pressure brake is turned on in step 8 is calculated from the pump applied voltage at this time,
The pump is forcibly driven only for the calculated time.

That is, in a negative pressure brake pump that is driven by applying a voltage to a main battery or an auxiliary battery of an electric vehicle or the like, the pump applied voltage fluctuates due to the voltage fluctuation of the battery, and the pump is driven due to the fluctuation of the pump applied voltage. The negative pressure filling completion time required to generate the negative pressure up to a predetermined upper limit varies inversely (see FIG. 4). On the other hand, if the forced pump drive time after the negative pressure brake is turned on at the stage of step S8 of FIG. 6 is set based on the pump applied voltage at this time, the forced pump drive time is set to the completion of load filling in FIG. It can be variably set according to the time (see Fig. 1).

Therefore, in order to execute the method of the present invention, FIG.
The relational data between the pump applied voltage and the forced pump drive time is stored in the ROM 6 of the control unit 1 of FIG. 2, and the pump applied voltage detection signal is input to the input interface 2 together with the negative pressure detection signal and the brake signal. still,
The control unit 1 of FIG. 2 has basically the same configuration as that of FIG. 3 and executes the same program as that of FIGS. 5 and 6.

In the method of the present invention, step S in FIG.
At the timing of inputting the brake signal when the negative pressure brake is turned on once in step 8, the pump applied voltage at this time is detected, and the forced pump drive time corresponding to the detected pump applied voltage is read from the ROM 6 to the CPU 3. Be done.
The process moves from step S8 to step S10, and the pump is forcibly driven for the forced pump drive time corresponding to the pump applied voltage to raise the negative pressure. The forced pump drive time at this time corresponds to the load filling completion time that fluctuates according to the fluctuation of the pump applied voltage, so when the forced pump drive is completed, the negative pressure becomes the upper limit and the forced pump drive is stopped. To do.

As shown in FIG. 1, the pump applied voltage when the pump is forcibly driven by turning on the negative pressure brake is V
x, and Tx is the forced pump drive time obtained from the applied voltage Vx, Tx changes in the range of Tm ≦ Tx ≦ Tn according to the pump applied voltage. However, Tn is the forced pump drive time when the pump applied voltage is minimum Va, and Tm is the forced pump drive time when the pump applied voltage is maximum Vb. The forced pump drive time Tx at such an arbitrary pump applied voltage Vx becomes substantially equal to the negative pressure filling completion time at the corresponding pump applied voltage Vx, and as a result, the forced drive of the pump does not waste time. Done efficiently. For example, in the case of the forced pump drive time Tm when the pump applied voltage is the maximum Vb, there is a difference of about 20 seconds between the forced drive time of this time Tm and the fixed time T ′ set by the conventional control method.
Therefore, the time for driving the forced pump is eliminated.

[0021]

According to the present invention, even if the applied voltage of the electric pump for generating the negative pressure for operating the negative pressure brake fluctuates, the fluctuating pump applied voltage causes the pump to operate during the negative pressure brake operation. Since the forced drive time is set, this forced pump drive time fluctuates according to the fluctuation of the pump applied voltage, and the forced drive of the pump during negative pressure braking operation is always the minimum optimum even if the pump applied voltage fluctuates. The negative pressure filling completion time can be executed without wasting time, and even if a failure occurs in the negative pressure detection circuit system, it is possible to easily ensure a good braking ability of the negative pressure brake.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between pump applied voltage and forced pump drive time for explaining the method of the present invention.

FIG. 2 is a block diagram of a control unit for explaining the method of the present invention.

FIG. 3 is a block diagram of a control unit for explaining a conventional negative pressure brake pump control method.

FIG. 4 is a graph showing a relationship between a pump applied voltage of a negative pressure brake pump and a negative pressure filling completion time.

5A is a flow chart showing an example of a control program for a negative pressure brake pump, and FIG. 5B is a waveform diagram.

FIG. 6A is a flowchart showing an example of a control program of a conventional system for a negative pressure brake pump;
Is a waveform diagram.

[Explanation of symbols]

 V pump applied voltage T forced pump drive time

Claims (1)

[Claims] 1. An electric pump for generating a negative pressure for operating a negative pressure brake in an electric vehicle or the like is driven by a battery voltage to stop the pump after a negative pressure filling completion time at which the negative pressure rises to a predetermined upper limit. When the negative pressure falls to a predetermined lower limit after the pump is stopped, the pump is driven by the negative pressure lower limit detection signal at this time, and the negative pressure is reduced even if the negative pressure falls to the predetermined lower limit after the pump is stopped. When the lower limit detection signal is not obtained, it is determined that the negative pressure detection circuit system has failed, and in the pump control method for forcibly driving the pump from the ON operation signal of the negative pressure brake after this failure determination, The pump applied voltage during the forced drive of the pump is detected, and the pump is forcibly driven after the failure determination for the negative pressure filling completion time obtained from the detected pump applied voltage. Pump control method for a negative pressure brake according to claim.