JPS60249736A - Overheat preventing apparatus for electromagnetic clutch - Google Patents

Abstract

PURPOSE:To prevent overheating of electromagnetic clutch by detecting the slip of clutch through signals detected by an engine rotation sensor and a rotation sensor at the output side of clutch and stopping the engine. CONSTITUTION:An engine rotation sensor 9 and a rotation sensor 11 at the output side and provided to a clutch thus to detect the condition where the car is stopped or moving with quite low speed and the clutch is slipping continuously on the basis of the output signals from said sensors. The detected signals are fed through AND gate 16 of comparators 12, 14 to a timer 17 and upon reaching to some setting time, an larm is fed from a relay circuit 19 to turn off the battey voltage of a clutch coil 24 thus to stop the engine. In such a manner, the clutch is protected from burning.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overheat prevention device for an electromagnetic clutch used in a vehicle transmission system, and particularly to a device for preventing the clutch from continuously slipping when the vehicle is stopped or at an extremely low speed.

Regarding electromagnetic clutches for vehicles, the present applicant has proposed, for example, Japanese Patent Application Laid-Open No. 56-131430, which uses an electromagnetic clutch instead of a friction clutch and automates clutch operation at the time of starting and shifting to create an easy drive. The structure is designed to achieve this.

Here, in the start control of the electromagnetic clutch, the clutch current is generally controlled so that the clutch torque has a functional relationship with the engine rotation speed, and the relationship between the clutch torque rise characteristic and the engine torque at the time of start is as follows. Figure 1 shows this. In a region where the engine speed is lower than point A where the two intersect on this torque curve, engine torque TE and clutch torque TC are
Since the relationship E>Tc, the clutch is slipping and is in a so-called half-clutch state.

Next, the entire drive system using an electromagnetic clutch will be considered with reference to FIG. The engine torque of engine E is T
E, the clutch torque of clutch C is TC1, the driving torque of spit wheel W is Tw, and the load torque on the road surface is TR (however, TV and TR are values converted onto the clutch shaft), then each part of the above half clutch area. The torque relationship is as follows: TE>Tc, Tc=TV. Furthermore, in the clutch connection region where the engine rotation speed is higher than point A in FIG. 1, 7E<Tc, Tw=TE. That is, a driving torque Tw equal to the engine torque T8 is generated at the wheels. Here, if TW>Tpe, the vehicle can run.

Generally, in a mechanical clutch such as a friction clutch, the clutch torque TC is 1.5 to 2. Since it is set to OTE, in the clutch connection area, TE = Tw and N
If TE≦Tr, the engine may stall and the driver may recognize that the vehicle is unable to run.

By the way, in an electromagnetic clutch, the clutch torque TC is a function of the engine speed, so when the engine speed decreases when Tw≦T, the clutch torque TO also decreases, and therefore the point in Figure 1 At A, Tc=
TE'=Tw≦TI? It may be balanced in the state of At this time, the engine stall as described above does not occur, but the clutch continues to slip while the vehicle is stopped or at an extremely low speed, resulting in a situation where the amount of heat generated by the clutch increases rapidly and burns out.

This phenomenon is not limited to electromagnetic clutches, but is unique to clutches that control clutch torque based on engine rotational speed, and is a weak point of transmission systems using this clutch.

Regarding the prevention of electromagnetic clutch burnout, there is a prior art, for example, Japanese Patent Application Laid-Open No. 56-60733, but this is intended to deal with cases where second starts are repeated, and is different from the technical idea of the present invention. ing.

In view of the problems peculiar to transmission systems using such electromagnetic clutches, the present invention aims to prevent clutch burnout when the clutch continues to slip continuously when the vehicle is stopped or at extremely low speed. The purpose of the present invention is to provide an overheating prevention device for an electromagnetic clutch.

For this purpose, the present invention detects that the clutch is slipping when the vehicle is stopped or at an extremely low speed using signals from an engine rotation sensor and a rotation sensor on the clutch output side, and when this condition continues for a predetermined period of time, the engine The purpose is to stop the operation and perform various incidental actions.

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings.

In FIG. 3, to explain the transmission system etc. of a vehicle using an electromagnetic clutch to which the present invention is applied, reference numeral 1 is an engine, and the engine power is transmitted to the electromagnetic clutch 2@
#l@ to be transmitted to the drive wheels 6 via the transmission 3, propeller shaft 4, differential device 5, etc. Then, as a control system that automates clutch operation, I! is applied to shift lever 7. A shift lever switch 8 and an engine rotation sensor 9 are connected to the electromagnetic clutch 2 via a control circuit 10, and the clutch current is controlled during gear shifting to connect and disconnect the clutch. Further, as a control system for preventing overheating according to the present invention, a rotation sensor 11 is further provided on the output side of the electromagnetic clutch 2 together with the engine rotation sensor 9.

In FIG. 4, the control circuit 10 includes an engine rotation sensor 9
The signal is compared with the set value of the voltage dividing circuit 13 by the comparator 12, and an output is generated when the engine rotational speed NE is N≧N1 for a rotational speed N1 that is slightly lower than the point A in FIG. Also, the signal from the rotation sensor 11 is transmitted to the comparator 14.
These comparators 12 .14 output side is AND gate 1
6 to the timer 17. The timer 17 generates an output when the timer setting time to is reached after the signal is input, and the output sides of the AND gate 16 and the timer 17 are connected to the AN
It is connected to a drive transistor 28 of a relay circuit 19 via a D gate 18 . Relay circuit 19 has two relays 2
0.21 and a warning lamp 22, one relay 20 connects the electromagnetic clutch coil 24 connected via the clutch current control circuit 23 to the battery side, and the other relay 21 connects the ignition coil circuit 25. and starter solenoid circuit 2G. Then, the relay 21 returns to the state where the circuits 25 and 26 are connected by turning off the ignition switch 27 by -H.

Because of this configuration, when the normal two-wheel drive starts, the clutch torque of the electromagnetic clutch 2 increases due to the increase in engine rotation, and the electromagnetic clutch 2 is connected, so that the engine power is immediately transmitted to the control circuit 10. Comparator 1 of
The output of No. 4 becomes L level. Therefore, the drive transistor 28 is turned off to de-energize the relay circuit 19, the alarm lamp 22 is turned off, the relay 20 is opened, the relay 21 is closed, and the shift lever switch 8 and engine rotation sensor are 9, the circuit 23 controls the clutch current of the electromagnetic clutch 2 to automatically connect and disconnect the clutch.

On the other hand, when starting on a slope, etc., a large load torque due to the road surface acts on the drive wheels 6, and this suppresses the increase in clutch torque with the engine rotation. If the electromagnetic clutch 2 is slipping in a half-clutch state, the clutch output side The signal from the rotation sensor 11 becomes zero or extremely low. Therefore,
The output of AN and D gates 16 becomes H level and timer 1
7, and if this state continues for longer than the timer setting time to, the transistor 28 is turned on by the A N D gate 18 and the relay circuit 19 is energized. Therefore, the alarm lamp 22 lights up, the circuit 25 is cut off by the relay 21 to stop the engine, and the circuit 26 is cut off to prevent the starter from being driven immediately after the engine stops. Further, battery voltage is applied to the coil 24 of the electromagnetic clutch 2 by the relay 20 to maintain the connected state, thereby preventing the vehicle from moving backward.

As is clear from the above description, according to the present invention, in a vehicle transmission system using an electromagnetic clutch, when the clutch continuously slips when the vehicle is stopped or at an extremely low speed when the vehicle is started, Since the engine will stop automatically, the clutch will be prevented from burning out in this case. Further, at this time, such an abnormality can be known by lighting the warning lamp 22, and since the starter is not driven immediately after the engine is stopped, protection of the clutch can be further ensured, and safety can also be ensured by the connected state of the clutch.

[Brief explanation of the drawing]

Fig. M1 is a diagram showing the torque characteristics, Fig. 2 is a diagram showing the torque action state of the transmission system, Fig. 3 is a configuration diagram showing the transmission system and control system of a vehicle to which the present invention is applied, and Fig. 4 is a diagram showing the present invention. 1 is a circuit diagram showing an embodiment of a device according to the invention; FIG. 2... Electromagnetic clutch, 9... Engine rotation sensor, 10... Control circuit, 11... Rotation sensor, 12.
14... Comparator, 1G, 18... AND gate, 17... Timer, 19... Relay circuit, 20
．． 21...Relay, 22...Warning lamp, 25...
・Ignition coil circuit, 26...Starter solenoid circuit. Patent Applicant Fuji Heavy Industries Co., Ltd. Agent Patent Attorney Makoto Kobashi Ukiyo Patent Attorney Susumu Murai 1st 2nd Diagram

Claims (1)

[Claims] In a vehicle transmission system that uses an electromagnetic clutch, signals from the engine rotation sensor and the rotation sensor on the clutch output side detect that the clutch is slipping when the vehicle is stopped or at an extremely low speed, and this condition is detected for a predetermined period of time. An overheat prevention device for an electromagnetic clutch, characterized in that it is configured to at least stop the engine if the overheating continues.