JPH0210736B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a safety device for an automatic speed control device in a motor vehicle.

The automatic speed control device (ASCD) uses a negative pressure servo, etc. as a vehicle speed control mechanism to automatically control the vehicle speed to a set speed without operating the accelerator pedal, or to control acceleration to the desired vehicle speed by operating a switch instead of operating the accelerator pedal (accelerate). Equipped with a control (resume) function that returns temporary deceleration to the original set vehicle speed.

Conventional automatic speed control devices are, for example, disclosed in Japanese Patent Application Laid-Open No. 1989-
In addition to the configuration shown in Japanese Patent No. 60923, the configuration is shown in FIG. The control amplifier 1 includes a set switch 2 for setting the vehicle speed, an acceleration switch 3 for controlling acceleration to the desired vehicle speed, and a resume switch 4 for returning to the set vehicle speed as operation switches, and a speed for detecting the actual vehicle speed. The vehicle speed is controlled using the detected value of the sensor 5 as a setting memory and feedback value. Vehicle speed control is achieved by a servo valve 6 that controls negative pressure (intake manifold negative pressure) led to the throttle valve actuator, and automatic speed control by switching between negative pressure and atmospheric pressure installed in the negative pressure path of this servo valve 6. The servo valve 6 and the two-way valve 7 are driven by the drive circuit output based on the control output of the control amplifier 1, using the two-way valve (two-way valve) 7 for switching to and release as the operating mechanism. The speed control and safety device will be specifically explained below.

The battery 9 is discharged by turning on the main switch 8.
Power is supplied to each part from After setting the desired vehicle speed with the accelerator pedal, when the set switch 2 is pressed, the control amplifier 1 generates a positive voltage at the terminals A and B, turning on the transistor 10. As a result, the relay 11 is energized and its contacts 11
A is switched from the illustrated state, and the two-way valve 7 operates in the path between the normally closed contact 12 of the brake pedal switch and the contact 11A, forming a negative pressure supply path to the servo valve 6. When the set switch 2 returns from this state, the control amplifier 1 stores the current vehicle speed and returns the terminals A and B to high impedance. However, the relay 11 is supplied with power through the path of the contact 11A and the diode 13, and the transistor 10
A base current is supplied through the line 14 to maintain the relay 11 and maintain the two-way valve 7 in its operating state. The control amplifier 1 outputs a positive voltage to the terminal C using the memorized current vehicle speed as a target value until the detected value of the speed sensor matches the target value, turns on the transistor 15, and changes the position of the servo valve 6, that is, the throttle valve is opened. Adjust the degree.

Next, acceleration control by the accelerate switch 3 is such that while the switch 3 is pressed, the control amplifier 1 generates a positive voltage at the terminals A and B to operate the two-way valve 7 in the same manner as described above, and at the same time, the switch 3 is pressed. During the operation of step 3, the transistor 15 is turned on directly from the switch 3 through the line 16, and the opening degree of the servo valve 6 is sequentially increased.
When the desired actual vehicle speed is reached by this acceleration control, when the acceleration switch 3 is reset, the control amplifier 1 memorizes the current vehicle speed and makes the terminals A and B high impedance in the same manner as the vehicle speed control by the switch 2. At the same time, the speed is automatically controlled by the control output of terminal C.

Next, the control for returning the vehicle speed to the set vehicle speed by the resume switch 4 will be explained. When the brake pedal is depressed in the vehicle speed control state, the normally closed contact 12 of the brake switch opens, the self-holding of the relay 11 is released, the contact 11A returns to the state shown, and the two-way valve 7 supplies negative pressure. The servo valve 6 also returns to the side where it shuts off. When the resume switch 4 is pressed in this deceleration state, the control amplifier 1 causes the relay 11 to self-hold and operate the two-way valve 7 in the same way as when setting the vehicle speed, and when the switch 4 returns, the setting is memorized before the brake operation. Acceleration control is performed using the output from terminal C so that the vehicle speed reaches the desired vehicle speed setting value.

Next, the safety device will be explained. The normally open contact 17 of the brake switch is used as a safety measure when the normally closed contact 12 cannot be opened due to welding or the like due to a short circuit in the servo valve 6 or the two-way valve 7. That is, when the brake is operated, even if the normally closed contact does not open, the transistor 18 is turned on by closing the normally open contact 17, the transistor 10 is turned off, and the self-holding of the relay 11 is released, and the two-way valve is closed. 7 is restored.

The welding detection circuit 19 detects welding of the contact 11A of the relay 11 to the terminal a side, suppresses acceleration control of the servo valve 6, and prevents acceleration against the driver's will. The welding detection method is to operate the brake at contact 12.
If the contact 11A returns to normal when the circuit is opened, the same battery 9 as the terminal B is connected to the terminal A of the detection circuit 19.
voltage appears, and when contact 11A is welded, terminal A
Judgment is based on the difference in which the ground is in contact with the ground. The welding detection circuit 19 continues to generate a positive voltage at the terminal C when detecting welding, keeps the transistor 20 in the on state,
The transistor 15 is regulated to be off through the diode 21, and the control output of the control amplifier 1 is locked through the terminal D of the amplifier.

In such a conventional safety device, the power circuit for the two-way valve 7 and the servo valve 6 is connected to the relay 11.
Since it is commonly formed by the contact 11A of the
5 due to a short-circuit failure between its collector and emitter, the servo valve 6 is driven to the fully open side by the self-holding of the relay 11 regardless of the control output of the control amplifier 1, and the servo valve 6 is accelerated against the driver's will. In response to this acceleration, by releasing the self-holding state of the relay 11 by operating the brake, it is possible to return to normal operation of the accelerator pedal. However, if the switch 3 is welded or the transistor 15 is short-circuited and the contact 11A is welded to the terminal a side, the current to the valves 7 and 16 can be cut off during brake operation;
When the brake is returned, the brake is returned to an unintended state of acceleration, and this acceleration continues until the main switch 8 is returned to its original position, without even the weld detection circuit 19 functioning to suppress the acceleration.

The present invention was made in view of the above circumstances, and
By using a drive circuit that has separate switch means for each of the two-way valve and servo valve to form a power supply circuit, we have created a safety device that reliably prevents unintentional acceleration due to drive circuit failure, etc. The purpose is to provide.

FIG. 2 shows an embodiment of the present invention, and the same parts or parts having the same functions as those in FIG. 1 are designated by the same reference numerals. In addition to the contact 11A forming the power supply circuit to the servo valve 6, the relay 11 includes the contact 11A.
It has a contact 11B forming a power supply circuit to the two-way valve 7 in the same switching mode as A, the terminals b and c of the contact 11B are connected in parallel to the respective terminals of the contact 11A, and the terminal a is connected to the two-way valve 7. be done. A diode 22 is provided in the forward direction from the output terminal C of the welding detection circuit 19 to the transistor 18 side, and allows the transistor 18 to release the self-holding of the relay 11 not only when the brake pedal is operated but also when the welding detection circuit 19 detects welding. There is.

In this embodiment, the control amplifier 1 outputs a control signal to match the current vehicle speed with the set vehicle speed by comparing the vehicle speed memory signal set by the vehicle speed setting switch 2 with the vehicle speed signal from the vehicle speed sensor 5. This becomes the first control means. Further, the transistor 15 is a second transistor that controls the servo valve 6 in response to a control signal from the control amplifier 1 or an acceleration control instruction signal from the acceleration switch 3.
becomes a means of control.

Then, transistors 10, 18 and relay 11
and its contact point 11A are connected to a transistor 1 which becomes a second control means in response to a signal from a control amplifier 1 according to the vehicle speed setting by a vehicle speed setting switch 2.
The first switch supplies power to the transistor 5 and cuts off the power to the transistor 15 in response to a signal from the brake switch 17. Similarly, relay 11
The contact 11B acts as a second switch that switches between supplying and cutting off power to the two-way valve 7 by operating together with the operation of the contact 11A, which is the output means of the first switch.

In this configuration, the relay 11 is self-holding and the contacts 11A and 11B are switched from the illustrated state,
If a welding failure occurs in one of the contacts 11A or 11B in the automatic travel control state where the two-way valve 7 and the servo valve 6 are energized, the welding detection circuit 19 detects welding by operating the brake and outputs the terminal C. Continue to maintain positive voltage. As a result, transistor 20 is turned on, transistor 15 is forcibly turned off, transistor 18 is turned on through diode 22, and transistor 10 is turned on.
is held in the off state. The relay 11 is energized in the return direction, and when the contact 11A is welded, the contact 11B returns to return the two-way valve 7 to the atmospheric pressure supply side, and when the contact 11B is welded, the contact 11A returns and the relay 1
Self-holding is canceled when the power to 1 is turned off. Therefore, when one of the contacts 11A, 11B has a welding failure, the operation of at least one of the valves is suppressed to avoid an unexpected speed increase.

In addition, the emitter-collector short circuit failure of the transistor 15 or the welding failure of the switch 3 and the contact 11
Even when a welding failure occurs in either A or 11B, an unexpected speed increase can be avoided in the same way as the above-mentioned effect. For example, failure of transistor 15 and contact 1
If the welding failure occurs on the terminal a side of 1A, it becomes impossible to energize or disconnect the servo valve 6 except for brake operation or main switch operation, but when the self-holding of the relay 11 is released, the contact 11B returns and the two-way The valve 7 is switched to the atmospheric pressure side and the acceleration control by the servo valve 6 is suppressed. Furthermore, if the transistor 15 fails and the contact 11B is welded to the terminal a side, the two-way valve 7 is biased toward the negative pressure side, but the power supply circuit of the servo valve 6 is interrupted, causing the valve itself to shift to the deceleration side. return.

According to this embodiment, in order to drive the servo valve and the two-way valve that control the accelerator throttle opening, two relays are used as switching means of the drive circuit.
Since a contact circuit is used and both contacts form separate power supply circuits for the servo valve and two-way valve, vehicle speed control is possible even in the event of contact welding failure of the relay, failure of the servo valve control transistor, or simultaneous failure of both. This has the effect of reliably preventing unintentional acceleration, for example, speed increase.

In addition, in the case of simultaneous occurrence of a welding failure of both contacts 11A and 11B and a short circuit failure of the transistor 15 in the embodiment, speed increase must be suppressed by operating the brake or main switch, but this failure occurrence rate is extremely low. By separately forming the power circuits for the servo valve and the two-way valve, a highly reliable safety device can be realized.

FIG. 3 shows the failure rate of the conventional device and this embodiment. _The failure rate P _{1 of the} conventional device shown in FIG _.
Then, the welding failure rate of contact 11A of relay 11 is
If B is ₁ , then the failure rate where both failures occur simultaneously is
P ₁ is approximately P ₁ = A×B ₁ ×10 ⁻⁹ (fit) …(1). Here, the failure rate unit (fit) is the number of failures per 10 ⁶ hours.

Compared to this conventional failure rate, the failure rate P ₂ in this embodiment is as shown in Figure 3b, and the failure rate B in which the contacts 11A and 11B of the relay 11 are welded at the same time is that the failure rate of one contact is the same as that of the entire relay. Since it is considered to be about 1% of the failure rate, which accounts for 50%, B=B ₁ /50(fit)...(2) Therefore, the failure rate P ₂ is as follows: The failure rate can be reduced to approximately 1/50 compared to

P ₂ = A × B ₁ × 1/50 × 10 ^-9 (fit) ... (3) In the embodiment, the relay 11 is used as a two-contact circuit to form separate power supply circuits for the servo valve 6 and the two-way valve 7, The configuration in which the diode 22 is omitted can also reduce the failure rate of unexpected speed increases compared to conventional devices. That is, in a configuration in which the diode 22 is omitted, if the contact 11B is welded to the terminal a side due to a short circuit in the two-way valve, the relay 1 is
1's self-holding is released and contact 11A returns,
Speed increase can be avoided by stopping the function of the servo valve 6. On the other hand, in the conventional device, if either the servo valve 6 or the two-way valve 7 is short-circuited and the contact point 11A is welded, speed increase cannot be avoided, and the failure rate is the sum of the failure rate of the servo valve and the two-way valve. Therefore, in this embodiment, the reliability is improved to the extent that the welding failure rate of the relay contacts is lower than that of the conventional device.

In addition, in the embodiment, a switch is provided between the relay contact 11B and the two-way valve 7, and this switch is controlled from on to off by the welding detection output of the welding detection circuit 19, thereby further avoiding acceleration failures. can be made certain. For example, as shown in FIG. 4, a PNP transistor 23 is connected between the terminal a of the contact 11B and the two-way valve 7.
is provided, and the transistor 23 is controlled from on to off by the output of the welding detection circuit 19. With this configuration, during normal operation, the transistor 23 is in the on state and the two-way valve 7 is controlled by the contact 11B, but when either one of the contacts 11A or 11B has a welding failure, the transistor 23 is in the off state. The two-way valve 7 can be returned to its original state, and a speed increase failure can be avoided.

As described above, according to the present invention, switching between supplying and cutting off power to a control means that controls a servo valve and switching between supplying and cutting off power to a two-way valve that switches between controlling and releasing the servo valve are performed. Because of the two-system configuration of the release signal, even if a failure occurs in one of the control threads of the servo valve and the two-way valve, the throttle control can be canceled by the normal operation of the other system, and the operation can be continued. This has the effect of reliably avoiding speed increase against the person's will.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional automatic speed control device, FIG. 2 is a circuit diagram showing an embodiment of the present invention, FIG. 3 is a diagram for explaining the failure rate of the conventional device and the present invention, and FIG. FIG. 4 is a main circuit diagram showing another embodiment of the present invention. 1...Control amplifier, 2...Set switch, 3...Accelerate switch, 4...Resume switch, 5...Speed sensor, 6...Servo valve, 7...Two-way valve, 8...Main switch, 11A, 11B... Relay contact, 12...
Normally closed contact of the brake pedal switch, 17... Normally open contact of the brake pedal switch, 19... Welding detection circuit.

Claims (1)

[Claims] 1. A vehicle speed detection means for detecting the speed of the vehicle, a brake switch for detecting that the brake is depressed, and a vehicle speed setting switch for instructing the setting of the vehicle speed.
A storage means for storing the vehicle speed set by the vehicle speed setting switch, an acceleration switch for instructing acceleration control, an actuator that opens and closes the throttle valve by controlling negative pressure, and negative pressure leading to the actuator. a servo valve that controls the vehicle speed; a first control device that receives the vehicle speed signal and the output signal from the storage device and outputs a control signal so that the current vehicle speed matches the set vehicle speed; a second control means for controlling the servo valve according to an acceleration control instruction signal from an acceleration switch; and a second control means for controlling the servo valve according to a vehicle speed setting signal output from the vehicle speed setting switch and a signal from the brake switch. a first switch that switches between supplying and cutting off power to the servo valve; a two-way valve that is provided in the negative pressure path of the servo valve and releases control of the servo valve when the brake is depressed; The signal from the brake switch causes the first
and a second switch that operates together with the operation of the switch to switch between supplying and cutting off power to the two-way valve.