JP3332651B2 - Pump control method for negative pressure brake - Google Patents

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, the present invention relates to a pump control method in an operation region where the negative pressure of the vacuum tank reaches a lower limit.

[0002]

2. Description of the Related Art A negative pressure brake mounted on an electric vehicle or the like is operated by a negative pressure generated by an electric pump (vacuum pump) driven by applying a voltage from 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 applied to the negative pressure brake. When negative pressure is stored in the vacuum tank up to a predetermined upper limit, the negative pressure detection circuit detects this and stops the pump, and when the vacuum pressure in the vacuum tank drops to a predetermined lower limit due to a brake operation or the like, this is reset. The negative pressure detection circuit detects the negative pressure and the pump starts driving again to increase the negative pressure to the upper limit.

The negative pressure stored in the vacuum tank of the negative pressure brake gradually decreases each time the negative pressure brake is turned on and off, and the braking capacity of the negative pressure brake gradually decreases.
Therefore, in order to maintain the braking capability of the negative pressure brake in an allowable range, a predetermined lower limit is set for the negative pressure, and the lower limit is detected by a negative pressure detection circuit system including a linear sensor, a lower limit switch, and the like. Control of the driving pump. There are various pump drive control methods incorporating control means for dealing with failure of the negative pressure detection circuit system.
One example will be described with reference to FIGS.

FIG. 3 shows a control unit 1 of a microcomputer for controlling the drive of an electric pump for negative pressure brake. An input interface 2 of the control unit 1 has a negative pressure detection signal from a negative pressure detection circuit system and a brake ON / OFF signal. When a brake signal is input, the CPU 3 reads the brake signal 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, a 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. When the CPU 3 determines that the negative pressure has reached the lower limit value based on the negative pressure detection signal, the CPU 3 outputs the pump drive signal via the output interface 4. Outputs and the pump starts driving.

[0005] The start of pump driving by detecting the lower limit of negative pressure is as follows:
For example, this is performed by a program shown in FIG. In step S1, pump control is started. In step S2, it is determined whether the pump is in the off state. If it is determined that the pump is in the off state, the process proceeds to step S3. It is determined in step S3 whether a lower limit of the negative pressure has been detected. If it is determined that the lower limit has been detected, pump driving is started, and the process proceeds to the end of pump control in step S6. If it is determined in step S3 that there is no lower limit detection, the process proceeds to step S4, where it is determined whether the negative pressure brake has been turned on and off a predetermined number of times (the number of times the negative pressure becomes equal to or less 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. If it is determined that the ON / OFF operation has been performed a predetermined number of times or more, the process proceeds to step S5. Step S5
In this case, although the negative pressure is lower than the lower limit, the lower limit of the negative pressure is not detected, the failure of the negative pressure detection circuit system, for example, a sensor failure is determined, an alarm is displayed, and the process proceeds to step S6. A series of operations at the time of occurrence of a failure in steps S1 to S6 described above are shown in the waveform of FIG.

In step S5 of FIG. 5A, it is determined that the sensor has failed. If the sensor is left unattended, the pump operation is not restarted, the negative pressure decreases, and the braking ability of the negative pressure brake decreases. . To avoid this negative pressure drop, FIG.
Is a control program at the time of sensor failure, and performs the following operation.

When the current sensor failure control is started in step S7, it is determined in step S8 whether or not the negative pressure brake has been turned on. If it is determined that the negative pressure brake has been turned on once, the process proceeds to step S9, in which the pump is forced to operate. When the driving is started, 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 has not been turned on, the process proceeds to step S10, where it is determined whether a predetermined time set in advance by a timer or the like has elapsed. , The pump is continuously driven, and after a lapse of a predetermined time, the process proceeds to step S11 to stop the drive of the pump.

In the program shown in FIG. 6A, when the lower limit of the negative pressure is not detected due to the failure of the negative pressure detecting circuit system, the pump is forcibly driven for a predetermined time every time the negative pressure brake is turned on once. This series of operations is shown in the waveform of FIG. The reason why the forced drive time of the pump driven by one operation of the negative pressure brake is regulated to a constant value is as follows. That is, if the negative pressure detection circuit system fails, even if the pump is forcibly driven and the negative pressure reaches the upper limit, the negative pressure upper limit is not detected, and a problem occurs in that the pump does not stop and continues to be driven unnecessarily. Therefore, when the pump starts to be driven by one operation of turning on the brake, the pump is forcibly driven for a certain time in anticipation of the negative pressure filling completion time at which the negative pressure reaches a predetermined upper limit, and after this certain time has elapsed, the pump is forcibly stopped. I have.

[0009]

In a negative pressure brake pump driven by applying a voltage from a main battery or an auxiliary battery of an electric vehicle or the like, the voltage of the main battery fluctuates due to a change in use conditions such as running of the electric vehicle. This voltage fluctuation becomes the fluctuation of the pump capacity as it is. Therefore, when the pump applied voltage is increased, the pump capacity is increased, and the negative pressure of the negative pressure brake is recovered at an early stage, and the negative pressure filling completion time from the start of pump driving to the time when the negative pressure reaches the upper limit is shortened. Conversely, when the pump applied voltage is reduced, the pumping capacity is reduced, the speed at which the negative pressure of the negative pressure brake is increased 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 when the pump applied voltage is the minimum Va is the longest, and the load filling completion time Pm when the applied voltage is the maximum Vb is the shortest. Therefore, the fixed time T 'is set, for example, at the position shown in the chain arrangement in FIG. 4 in accordance with the fixed time set in step S10 in FIG. 6A and the longest load filling completion time Pn in FIG. Was. The reason is that if the fixed time T ′ is set shorter than the maximum load filling completion time Pn, FIG.
When the pump is driven at the minimum applied voltage Va in step S9, the drive is stopped for a certain time T 'before the load filling completion time Pn at this time arrives, the load does not rise to the upper limit, and the negative pressure brake This is because a malfunction occurs in which the braking ability of the vehicle cannot be sufficiently restored.

However, when the pump drive control is performed by setting the fixed failure determination time T 'as described above, there is not much problem when the pump applied voltage at the time of forcible drive of the pump is low. In addition, there is a problem 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 the maximum Vb and the load filling completion time Pn when the pump applied voltage is the minimum Va in FIG.
In the case of a normal electric vehicle, it takes about 20 seconds. In this case,
When the forcible drive of the pump is performed by the negative pressure brake operation when the pump applied voltage is the maximum Vb, the time point P at which the load charging is completed is completed.
The pump was stopped at a fixed time T 'after about 20 seconds or more from m, and the pump was driven uselessly for about 20 seconds.

An object of the present invention is to waste time in forcibly driving a pump for recovering a negative pressure by forcibly driving the pump with a signal for turning on a negative pressure brake when a negative pressure detection circuit system fails. And to perform it efficiently.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a negative pressure charging system 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 so that the negative pressure rises to a predetermined upper limit. After the completion of the pump, the pump is stopped.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. If the negative pressure lower limit detection signal is not obtained even when 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 negative pressure brake ON operation signal after the failure determination. In the above-described pump control method, the pump application voltage at the time of forcible driving of the pump is detected, and the pump forcible operation after the failure determination is performed for the negative pressure filling completion time obtained from the detected pump application 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 by the battery voltage, the negative pressure filling completion time fluctuates due to the fluctuation of the pump applied voltage. By setting the forced drive time to 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 minimized Optimum negative pressure filling completion time is achieved, and therefore, execution can be performed without wasting time.

[0015]

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

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

That is, in a negative pressure brake pump driven by applying a voltage from a main battery or an auxiliary battery of an electric vehicle or the like, the pump applied voltage fluctuates due to the fluctuation of the battery voltage, and the pump is driven by the fluctuation of the pump applied voltage. The negative pressure filling completion time required to generate a 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 in step S8 of FIG. 6 is determined from the pump applied voltage at this time, the forced pump drive time is determined as shown in FIG. It can be set variably in accordance with the time (see FIG. 1).

In order to execute the method of the present invention, FIG.
Is stored in the ROM 6 of the control unit 1 shown in FIG. 2, and the input interface 2 is supplied with the pump application voltage detection signal together with the negative pressure detection signal and the brake signal. still,
The control unit 1 shown in FIG. 2 has basically the same configuration as that shown in FIG. 3 and executes the same program as that shown in FIGS.

In the method of the present invention, step S in FIG.
At the input timing of the brake signal indicating that the negative pressure brake has been 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 into the CPU 3. It is.
The process proceeds from step S8 to step S10, in which the pump is forcibly driven for the forced pump driving time corresponding to the pump applied voltage to increase the negative pressure. Since the forced pump drive time at this time corresponds to the load filling completion time that fluctuates in response to the change in the pump applied voltage, when the forced pump drive is completed, the negative pressure becomes the upper limit and the forced drive of the pump stops. I do.

As shown in FIG. 1, the voltage applied to the pump when the pump is forcibly driven by turning on the negative pressure brake is V.
x, assuming that the forced pump driving time obtained from the applied voltage Vx is Tx, Tx changes according to the pump applied voltage in the range of Tm ≦ Tx ≦ Tn. Here, 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. As a result, 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. It is done efficiently. For example, in the case of the forced pump drive time Tm at the time of the maximum pump applied voltage Vb, there is a difference of about 20 seconds between the time Tm and the fixed drive time T ′ set by the conventional control method,
To that extent, time wasted in 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 pump at the time of the negative pressure brake operation is operated with the fluctuating pump applied voltage. Since the forced drive time is set, the forced pump drive time fluctuates in accordance with the pump applied voltage fluctuation, and the forced drive of the pump during negative pressure brake operation is always the minimum optimum even if the pump applied voltage fluctuates. It can be executed without wasting time in the negative pressure charging completion time, and even if a failure occurs in the negative pressure detection circuit system, it is easily possible to always ensure a good braking capacity of the negative pressure brake.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a pump applied voltage and a forced pump driving time for explaining a 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 voltage applied to a negative pressure brake pump and a negative pressure filling completion time.

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

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

[Explanation of symbols]

 V Pump applied voltage T Forced pump drive time

Claims (1)

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