GB1559822A

GB1559822A - Manually or pedally propelled vehicles such as bicycles

Info

Publication number: GB1559822A
Application number: GB2496075A
Authority: GB
Original assignee: TI Raleigh Industries Ltd
Current assignee: TI Raleigh Industries Ltd
Priority date: 1976-07-01
Filing date: 1976-07-01
Publication date: 1980-01-30

Description

(54) MANUALLY OR PEDALLY PROPELLED VEHICLES SUCH AS BICYCLES (71) We, TI RALEIGH INDUSTRIES (formerly RALEIGH INDUSTRIES LIMITED) a British Company of 177 Lenton Boulevard, Nottingham, NG7 2DD, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to manually or pedally propelled vehicles, such as bicycles, provided with electrical power assistance and in particular to such vehicles provided with an electrical control circuit for limiting the output of an electrical battery to avoid excessive discharge thereof.

Excessive electrical discharge of an electrical battery generally results in damage to the battery and full discharge, particularly if allowed to occur regularly, can seriously shorten the battery's effective working life.

However, curing this disadvantage is not just simply a matter of controlling the current flow from the battery so that the battery voltage or state of charge does not fall below a certain limit, by connecting to the battery an appropriate control circuit, since the control circuit itself will also consume power and this power consumed must be minimised. The control circuit of the invention has particular application in the field of motor control for it is in this field, where the current supply may be high, that an accidental complete battery discharge is likely to occur. Such motor control will be beneficial in the field of power assisted vehicles of the type described in the Applicants' co-pending application No. 4510/74 Serial No. 1 504 121 to which this present application is an application for a Patent of Addition. In vehicles of this type the ratio of the total operating time of the vehicle to the operating time of the motor and the total time that the control circuit is receiving current from the battery is likely to be relatively high.

According to the invention of co-pending application No. 4510/74 Serial No. 1 504 121 there is provided a wheeled vehicle for conveying one or more riders and including a drive transmission adapted to apply manual or pedal effort exerted by a rider or riders to the rotation of the wheels to propel the vehicle, incorporating electricallypowered auxiliary drive means also adapted to be effective through said drive transmission but which is inadequate alone to provide sufficient power for normal propulsion (as hereinafter defined) of the vehicle and its rider or riders, and control means sensitive to the manual or pedal force exerted on the drive transmission and adapted when said force reaches a selected level to bring the auxiliary drive means into operation.

By normal propulsion is meant continuous propulsion of the vehicle in still conditions along a level surface.

The alternate methods of motor control are either ON/OFF switching or some type of proportional control. Since the motor drive unit is designed for power assistance only, ON/OFF switching is adequate. However, direct mechanical ON/OFF switching does not permit battery low voltage protection, except as an extra circuit capable of switching the total motor current. An indirect switching system would normally be one of the following: controlled thyristor switching, controlled transistor switching, or controlled solenoid switching.

Controlled thyristor or transistor switching have a relatively constant voltage drop across the devices which can result in several percent of total power available to the motor being lost as heat in addition to other control circuit power losses. In contrast to this with controlled solenoid switching, the voltage drop across the switch is negligible but the solenoid current is a constant loss irrespective of the current through the motor.

According to the present invention, there is provided a wheeled vehicle for conveying one or more riders including a drive transmission adapted to apply manual or pedal effort exerted by a rider or riders to the rotation of the wheels to propel the vehicle, incorporating an electric motor also adapted to be effective through said drive transmission but which is inadequate alone to provide sufficient power for normal propulsion (as hereinbefore defined) of the vehicle and its rider or riders, control means sensitive to the manual or pedal force exerted on the drive transmission and adapted when said force reaches a selected level to bring the electric motor into operation, switching means forming part of the control means and comprising a solenoid operated relay having contacts disposed in the supply circuit from a battery terminal to the electric motor, a switch connected to the solenoid coil, and impedance means disposed in series with the solenoid coil for connection across the battery, the switch being operative to momentarily short circuit the impedance means to enable current to be supplied to the coil at a higher level to operate the solenoid to connect the electric motor to the battery terminal, the solenoid thereafter being held in that position at a lower current level, and a battery voltage sensing circuit connected to the switch, said sensing circuit being operative to sense battery voltage when the electric motor is required and to control the switch to prevent momentary closure of the switch when under charge conditions are sensed.

In order that the invention may be more clearly understood, several embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a control circuit for a battery power supply circuit to a motor incorporating PNP transistor switching means, Figure 2 shows an alternative to Figure 1 incorporating NPN transistor switching means, Figures 3 and 4 respectively show the circuits of Figures 1 and 2 with further modifications, Figure 5 shows a further embodiment including a protection against overcharging feature, and Figure 6 shows a modification of the embodiment of Fibre 5.

Referring to Figure 1, a motor 31 is connected through contacts 32 across the terminals of a battery 33. The contacts 32 are the contacts of a solenoid whose coil 34 is connected in series with impedance means in the form of a resistor 35 and through a switch 36 to one terminal of the battery 33.

The end of the coil 34 remote from the resistor is connected to the other terminal of the battery 33 and to the terminal of the motor 31 remote from the contacts 32.

The resistor 35 is connected across the collector emitter path of a PNP transistor 37 and the base of this transistor is connected through a voltage sensing network to the terminal of motor 31 connected to the contacts 32. Diodes 39 and 310 provide protection for the transistor 37, against induced spikes caused by operation of the switch 36 or contacts 32. The sensing network comprises a zener diode 314 loaded by a PNP transistor 311. The emitter of transistor 311 is connected to the base of transistor 37, the collector to a resistor 312 and the base to the junction between a resistor 313 and zener diode 314. The other terminal of the resistor is connected to the junction between the switch 36 and transistor 37, the other terminal of the zener diode 314 to the diode 39 and to the junction between the contacts 32 and motor 31, and the other terminal of the resistor 312 to the junction between the solenoid 34 and negative terminal of the battery 33.

In operation, with switch 36 closed, the battery voltage is sensed by the series combination of resistor 313 and zener diode 314 connected in series with the motor 31. If the battery voltage is above the predetermined minimum the zener diode conducts sufficiently, and a negative voltage appears at the base of PNP transistor 311 which switches transistor 311 on. This in turn switches the transistor 37 on to feed current direct to the solenoid coil 34 and operate the contacts 32 to complete the motor supply circuit When the contacts 32 close, the transistors 311 and 37 are turned off and the solenoid current is limited by resistor 35 to a holding current only. Should the battery voltage be too low to fully turn on the zener diode 314 and thus the transistors 311 and 37, the contacts 32 will not close and the motor 31 will therefore receive no current.

Figure 2 shows the preferred embodiment employing NPN switching transistors 47 and 411 but corresponding in other ways to the embodiment of Figure 1 except for the porality reversal attendant upon the use of NPN instead of PNP transistors. The operation of the circuit is the same as that of Figure 1 except that the transistors 411 and 47 are switched on by a positive voltage at their bases. Accordingly, the base of transistor 411 is connected to the negative terminal of the battery through resistor 413.

In the circuits of Figures 1 and 2 temporary current surges and resultant lowering of battery voltage may be accommodated employing a delay in the battery and/or trigger voltage sensing network. These will prevent relay chatter or oscillation when switching at marginal battery voltage or if the mechanics of the relay are such that the relay does not fully close before the voltage sensing circuit is disconnected.

The switch 36 or 46 is a torque sensing switch and is automatically operated whenever a certain torque value is reached in the drive transmission. An unnecessary drain may be imposed at the battery at a time when it is already largely discharged unless precautions to prevent this are taken. With a sensing network full solenoid closing current cannot flow unless the battery voltage indicates a sufficient state of charge since resistor 35 or 45 will still be in series with the solenoid coil. The loss is limited in this case to no more than solenoid holding current, and the battery is in measure protected against over discharge through the solenoid circuit, in addition to the motor being prevented from turning on.

Referring to Figures 3 and 4 circuits are shown respectively corresponding to Figures 1 and 2, but incorporating further modifications. In Figure 3 motor braking is provided for by providing a changeover switch 52 in place of the contacts used previously so that the motor 51, acting as a generator, can be stopped rapidly. A series connection of a light emitting diode 515 (LED) and a resistor 516 is connected between one terminal of the switch 56 and the zener diode 514 to provide an indication of low battery charge state or certain circuit failures. The light of the LED shows when switches 56 and 517 are closed (due to a sufficient torque being reached), but when the switch 52 has not closed the battery-motor circuit due to a low battery voltage. With the switch 52 in the position closing the battery-motor circuit and switches 56 and 517 closed, the LED 515 is short circuited. The switch 517 is key operated. Without some indication of low battery charge a rider of a power assisted vehicle might be tempted to alter the torque at which the switch 56 operates.

If the battery charge is sufficient so that the switch 52 closes the battery-motor circuit, the LED is flashed only momentarily as the closure of switch 52 follows closely on the closure of switch 56. A capacitor 518 bridging the resistor 513 prevents chatter if the solenoid does not operate rapidly and a diode 519 prevents damage to the control circuitry if the battery is inserted with reverse polarity.

Figure 4 shows a circuit similar to Figure 3 but with NPN transistors used and the polarity reversed accordingly.

Battery overcharge protection means such as are shown in Figure 5 may be provided.

The circuit is substantially the same as that of Figure 4, but with extra contacts for the solenoid and on the key switch and extra zener diode. The solenoid now has two sets of ganged two position changeover contacts 72(a) and 72(b) and terminals 721 and 722 are provided for the connection of a charger 720. The terminal 722 is connected to the contacts 72(b) and the terminal 721 to the positive terminal of the battery through a diode 724. The key operated switch 717 is a two position switch which in one position connects one terminal of the motor 71 to the positive terminal of the battery and in its other position connects the base of transistor 711 through an additional zener diode 723 to the positive terminal of the battery.

The negative terminal of the charger is connected, through a further switch 726 to a point between the diode 719 and switch 76.

This switch 726 is ganged with the switch 717.

This circuit works in the same way as the circuit of Figure 4 with the sensing network enabling closure of the solenoid contacts, except that the sensing network also senses the fully charged voltage.

Figure 5 shows the position of ganged switches 717 and 726 with the electrical drive system switched off. Switch 726 provides a return path for the current when the torque switch 76 is open, for example, when the vehicle is parked. By being ganged to switch 717 it cannot be used to by-pass switch 76 during riding as no drive could be possible since switch 717 would disconnect the motor from the battery.

As switch 726 is connected to the charger terminal 722 the return path is not affected by the operation of the solenoid contacts 72b when full charged state has been sensed.

Thus when the solenoid operates and contacts 72b also operate, the battery is disconnected from the charger but the solenoid remains energised.

Once the solenoid has operated, the zener diode 723 detects the charger open circuit voltage which will be greater than the fully charged battery voltage, and hence the solenoid will stay energised until the charger is disconnected.

When the charger is connected to the battery its open circuit voltage is reduced by the low impedance of the battery to essentially the battery voltage. As the battery charge state rises its terminal voltage also increases. The charger terminal voltage rises naturally with it. When the charge level reaches a level sufficient for zener 723 to turn on transistor 711, transistor 77 also turns on and energises the solenoid. Operation of solenoid causes the negative terminal's connection between the charger and battery to be broken and the battery cannot then be further charged. An additional diode 730 is connected into the circuit between the zener diode 714 and the junction between the base of transistor 711 and resistor 713 to block any battery partial discharge after full charge and solenoid operation via the path through the zener diodes 723 and 714 and contacts 72a to the negative terminal of the battery.

When switch 726 is operated without the charger, that is when normal propulsion is required, switch 717 reconnects the motor drive to the positive battery terminal, and isolates zener 723. This isolation is not really necessary since zener 723 will not conduct once the battery has been off charge a short time. Zener 723 could be connected directly to the battery + terminal but switch 717 would still be required to prevent the motor running when contacts 72a operate. A small boost charge can be applied by switching the charger off and then on again some time after the solenoid has operated. This will occur because battery voltage drops after the charge has been stopped for a short period.

A further modified embodiment is shown in Figure 6. The circuit is substantially the same as that of Figure 5 except for the following modifications. One terminal of the motor 81 is connected to one terminal of a resistor 88 which forms with a potentiometer 816 and further resistor 812, a potential divider and which senses the battery voltage via the motor and switch 817a. The poten tiometer slider is connected through zener diode 814 to the base of transistor 811. The base of this transistor 811 is also connected through a resistor 813 and diodes 823a and 823b to the negative line. The potentiometer permits fine voltage adjustments to be made to take account of component variations and the diodes 823a and 823b provide some tem perature compensation for components 87, 811 and 814 and reverse current protection against incorrect battery connection. A resistor 815 is connected between the potentiometer 816 and switch 817a and sets zener diode voltage sensing to high range for full battery charge sensing. The zener diode 814 permits base current to flow in transistor 811 when battery voltage is above a preset minimum and operates over two ranges de pending on the position of switch 817a or, resistor 815 could be connected directly to the positive voltage line, avoiding the necessity for an extra switch contact. The connection through resistor 815 is used when charging the battery, permitting the solenoid to operate only when the battery reaches volts corresponding to full charge. Once operated the solenoid disconnects the charger via 82b.

The charger however keeps current flowing in the control circuit even though the battery is disconnected thus preventing overcharging.

The connection through 88 permits the zener to sense low battery volts, i.e. it can only pass current to the transistors when the battery voltage is sufficiently high to drive the motor without ill effects. When the solenoid does operate, 88 is connected via 82a to the negative terminal 822 of the battery charger 820, thus turning off the transistors, leaving the solenoid held closed via 85 until 86 opens. The diodes 89 and 810 respectively suppress inductive spikes from the motor and solenoid contacts.

The above described circuits can be modified in a number of ways. In relation to the embodiment of Figure 6, for example, the following modifications are possible. The drive or charge functions could be operated independently and the unused parts of the circuit omitted. Motor braking could be dispensed with by removing the link from the switch 82a to the cathode of diode 89. Temperature compensating means alternative to the diodes 823a and 823b could be provided and PNP or a combination of NPN and PNP transistors could be used. Switch 86 could be a semi-conductor or similar solid state device.

Using this system the vehicle operator has no regular charging to terminate at awkward times. It should be habitual to connect the charger after every journey and expect a full battery on the next journey without unnecessary trickle charge. The penalty is that the charger is required to hold on the solenoid for the period from the end of the charge to charger disconnection, which may be hours. However, the charger is only delivering sufficient power to hold on the solenoid.

The above described circuitry enables the following advantages to be achieved. Low battery life due to overcharging or repeated full discharges can be avoided. The circuitry has been designed to minimise current consumption after switching the motor on. Apart from the solenoid holding current the circuitry is isolated and no other standby current is required. The circuit can be provided at very low cost and weight due to the use of a minimum number of components. By using a solenoid to close the main switch, (providing the predetermined minimum voltage allows this), the current required to perform the closing operation reduces, after closing, to a very much smaller holding current only. The motor is used as a part of the control circuit until the solenoid switch is closed thus automatically isolating the closure permitting circuit, and minimising the power loss. The solenoid switch can be made to reduce the "run-down" time of the motor after switching off (at the changeover switch) by in effect, short-circuiting the motor. The circuit enables a smaller battery to be used for a given range. The circuit is fail safe in that incorrect connection of the battery terminals will not damage the system and at the same time will not permit the motor to start. The circuit is designed such that even though the voltage may drop below the normal minimum the motor will not inadvertently switch off until such time as the torque sensing arrangement allows, (e.g. by reduction of pedalling effort). By this means the operator will be able to continue with power assistance for a reasonable distance without having an unexpected interruption of power assistance. If an excessive distance should be attempted e.g. by shorting the torque sensing switch, the battery voltage could fall to a level which is insufficient even to maintain the solenoid holding current. At this point the solenoid will drop out thus switching off the motor and minimising damage to the battery.

It will be appreciated that the above embodiments have been described by way of example only and that many modifications are possible without departing from the scope of the appended claims. For example, the key operated switch could be otherwise operated by a lever.

WHAT WE CLAIM IS: 1. A wheeled vehicle for conveying one or more riders including a drive transmission adapted to apply manual or pedal effort exerted by a rider or riders to the rotation of the wheels to propel the vehicle, incorporating an electric motor also adapted to be effective through said drive transmission but which is inadequate alone to provide sufficient power for normal propulsion (as hereinbefore defined) of the vehicle and its rider or riders, control means sensitive to the manual or pedal force exerted on the drive transmission and adapted when said force reaches a selected level to bring the electric motor into operation, switching means forming part of the control means and comprising a solenoid operated relay having contacts disposed in the supply circuit from a battery terminal to the electric motor, a switch connected to the solenoid coil, and impedance means disposed in series with the solenoid coil for connection across the battery, the switch being operative to momentarily short circuit the impedance means to enable current to be supplied to the coil at a higher level to operate the solenoid to connect the electric motor to the battery terminal, the solenoid thereafter being held in that position at a lower current level, and a battery voltage sensing circuit connected to the switch, said sensing circuit being operative to sense battery voltage when the electric motor is required and to control the switch to prevent momentary closure of the switch when under charge conditions are sensed.

2. A vehicle as claimed in Claim 1, wherein the switch comprises a transistor.

3. A vehicle as claimed in Claim 2, wherein the transistor is a PNP transistor.

4. A vehicle as claimed in Claim 2, wherein the transistor in an NPN transistor.

5. A vehicle as claimed in any preceding claim, wherein the sensing circuit comprises a zener diode, resistor and transistor, the zener diode and resistor forming a voltage divider, and the base of the transistor is connected to the junction of the voltage divider, the divider being adapted to be connected to the solenoid contacts.

6. A vehicle as claimed in Claim 5, when appendant to Claim 3, wherein the sensing circuit transistor is a PNP transistor.

7. A vehicle as claimed in Claim 5, when appendant to Claim 4, wherein the sensing circuit transistor is an NPN transistor.

8. A vehicle as claimed in any preceding claim, wherein a switch whose position is dependent upon the force supplied from the primary driving means is disposed in a supply circuit from the battery terminal to the solenoid coil, the switch being operative to close the supply current to the solenoid coil when the force supplied from the primary driving means has reached the selected level.

9. A vehicle as claimed in any preceding claim, wherein the solenoid contacts comprise a changeover switch having a first position in which the supply circuit from the battery terminal to the motor is completed and a second position in which the motor is short circuited.

10. A vehicle as claimed in Claim 9, wherein a key operated switch is disposed in a supply circuit from the battery terminal to the solenoid coil.

11. A vehicle as claimed in Claim 10, when appendant to Claim 8, wherein a series connection of a resistor and light emitting diode is connected between the solenoid coil side of the switches in the supply circuit to the coil and one terminal of the motor such that, in operation, current flows through the light emitting diode when the switches in the supply circuit are closed and the changeover switch is in the said second position.

12. A vehicle as claimed in any preceding Claim, wherein a diode is positioned in a supply circuit from the battery terminal to the solenoid coil to provide polarity reversal protection.

13. A vehicle as claimed in any preceding claim, wherein terminals are provided for the connection of a battery charger when the vehicle is stationary.

14. A vehicle as claimed in Claim 13, when appendant to Claim 9, wherein one of the terminals is connected to a two position switch ganged to the changeover switch comprising the solenoid contacts having a first position in which each charger terminal is connected to a respective battery terminal and corresponding to the second position of the changeover switch.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. system and at the same time will not permit the motor to start. The circuit is designed such that even though the voltage may drop below the normal minimum the motor will not inadvertently switch off until such time as the torque sensing arrangement allows, (e.g. by reduction of pedalling effort). By this means the operator will be able to continue with power assistance for a reasonable distance without having an unexpected interruption of power assistance. If an excessive distance should be attempted e.g. by shorting the torque sensing switch, the battery voltage could fall to a level which is insufficient even to maintain the solenoid holding current. At this point the solenoid will drop out thus switching off the motor and minimising damage to the battery. It will be appreciated that the above embodiments have been described by way of example only and that many modifications are possible without departing from the scope of the appended claims. For example, the key operated switch could be otherwise operated by a lever. WHAT WE CLAIM IS:

1. A wheeled vehicle for conveying one or more riders including a drive transmission adapted to apply manual or pedal effort exerted by a rider or riders to the rotation of the wheels to propel the vehicle, incorporating an electric motor also adapted to be effective through said drive transmission but which is inadequate alone to provide sufficient power for normal propulsion (as hereinbefore defined) of the vehicle and its rider or riders, control means sensitive to the manual or pedal force exerted on the drive transmission and adapted when said force reaches a selected level to bring the electric motor into operation, switching means forming part of the control means and comprising a solenoid operated relay having contacts disposed in the supply circuit from a battery terminal to the electric motor, a switch connected to the solenoid coil, and impedance means disposed in series with the solenoid coil for connection across the battery, the switch being operative to momentarily short circuit the impedance means to enable current to be supplied to the coil at a higher level to operate the solenoid to connect the electric motor to the battery terminal, the solenoid thereafter being held in that position at a lower current level, and a battery voltage sensing circuit connected to the switch, said sensing circuit being operative to sense battery voltage when the electric motor is required and to control the switch to prevent momentary closure of the switch when under charge conditions are sensed.

2. A vehicle as claimed in Claim 1, wherein the switch comprises a transistor.

3. A vehicle as claimed in Claim 2, wherein the transistor is a PNP transistor.

15. A vehicle as claimed in Claim 14,

when appendant to Claim 10, wherein the said one battery charger terminal is connected to the supply circuit to the solenoid coil through a two position switch which is ganged with the key operated switch which is a two position switch, the key operated switch having a first position in which the other battery charger terminal is connected to the battery voltage sensing circuit and a second position in which the other battery charger terminal is connected to one terminal of the motor, the first positions of the key operated switch corresponding to the closed position of the two position switch.

16. A vehicle as claimed in Claim 15, wherein the other terminal of the motor is connected to a potential divider comprising a resistor and a potentiometer, the slider of the potentiometer being connected to the battery voltage sensing circuit and providing for voltage adjustment to accommodate fluctuating component values.

17. A vehicle as claimed in claim 13, 14 or 15, in which the battery voltage sensing circuit is operative to control the switching means to disconnect the battery charger when over charge conditions are sensed and to prevent reconnection under those conditions.

18. A vehicle substantially as hereinbefore described with reference to Figure 1, 2, 3, 4, 5 or 6, of the accompanying drawings.