HK1102065B - Battery pack, cordless power tool and identification method thereof - Google Patents

Description

Battery pack, cordless power tool and identification method thereof

Technical Field

The present invention relates to cordless power tools, and more particularly to cordless power tools having tool identification circuitry.

Background

A wide variety of power tools are used in different applications such as construction applications, fire and rescue applications, and the like. Some examples of cordless power tools include, but are not limited to: wireless electric drill, wireless annular saw, wireless reciprocating saw, wireless sand mill, wireless screwdriver and flash light. Cordless power tools use a rechargeable battery pack to power them for operation. The rechargeable battery pack can be easily removed from the cordless power tool and connected to an external battery charger for recharging purposes.

The battery pack includes one or more batteries. The battery pack also includes monitoring circuitry for monitoring parameters such as battery voltage values, discharge current and charge current. There are many different cordless power tools and battery packs. One battery pack can be applied to various cordless power tools. However, there is no way to inform the battery pack of any details about the cordless power tool. Therefore, a tool identification circuit is needed to notify an inserted battery pack of data specific to the wireless tool.

Disclosure of Invention

The invention provides a cordless power tool. The cordless power tool includes tool identification circuitry that provides a tool identification signal to a battery pack. The tool identification signal represents data specific to the cordless power tool, said data including a threshold value of a power parameter of said cordless power tool; wherein the cordless power tool includes the battery pack, the battery pack includes monitoring and control circuitry that compares at least one monitored state value to the threshold value.

The invention also provides an identification method of the wireless electric tool. The identification method of the wireless electric tool comprises the following steps: a battery pack is coupled to a cordless power tool and a tool identification signal from the cordless power tool is provided to the battery pack when the battery pack is properly coupled to the cordless power tool. The tool identification signal represents data specific to the cordless power tool, said data including a threshold value of a power parameter of said cordless power tool, wherein said battery pack includes monitoring and control circuitry, said monitoring and control circuitry comparing at least one monitored condition value to said threshold value.

The invention also provides a battery pack. The battery pack includes at least one battery and a monitoring and control circuit, and the monitoring and control circuit is connected to the battery. The monitoring and control circuit receives a tool identification signal from the cordless power tool when the battery pack is properly connected to the cordless power tool. The tool identification signal represents data specific to the cordless power tool, said data including a threshold value of a power parameter of said cordless power tool, said monitoring and control circuitry comparing at least one monitored condition value to said threshold value.

Drawings

The features and advantages of embodiments of the present invention will become more apparent in light of the following description of the drawings in which like numerals represent like parts and in which:

FIG. 1 is a perspective view of a cordless power tool;

FIG. 2 is a circuit diagram of a power supply system of the cordless power tool of FIG. 1;

FIG. 2A is a circuit diagram illustrating one embodiment of the tool identification circuit of FIG. 2;

FIG. 2B is a circuit diagram of another embodiment of the tool identification circuit of FIG. 2;

FIG. 2C is a circuit diagram illustrating one embodiment of monitoring and control circuitry that functions in conjunction with the tool identification circuitry of FIGS. 2A and 2B;

FIG. 3 is a circuit diagram associated with FIG. 2, wherein the load is a motor driving components of the cordless power tool;

FIG. 4 is another circuit diagram of the power supply system of the cordless power tool of FIG. 1;

FIG. 5 is a circuit diagram of another embodiment of the monitoring and control circuit of FIG. 2; and

FIG. 6 is a flow diagram illustrating operations associated with one embodiment.

Although the following detailed description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the invention is intended to cover a wide range.

Detailed Description

Fig. 1 shows a perspective view of a cordless power tool 100. The cordless power tool 100 is illustrated as a cordless drill and will be described in relation to embodiments herein. The cordless power tool 100 may be any type of cordless power tool, including but not limited to: wireless circular saw, wireless reciprocating saw, wireless sand mill, wireless screwdriver and flash light. Cordless power tools include a rechargeable battery pack 102 for providing power to operate the tool 100. The rechargeable battery pack 102 can be easily removed from the cordless power tool 100 and connected to an external battery charger for recharging purposes. The cordless power tool 100 also includes a trigger 104. For a power drill, the user depresses and depresses the trigger 104 to control the speed of the chuck 142. For other tools, such as flashlights, the user may set the position of the trigger to control the intensity of the flashlights.

Fig. 2 is a circuit diagram of a power supply system 200 of the cordless power tool of fig. 1. The power system 200 includes a battery pack 102, a load 240, a trigger 104, and a tool Identification (ID) circuit 230. As used herein, a "circuit" includes: such as a single fixed circuit, programmable circuit, state machine circuit, and/or firmware that stores instructions executed by programmable circuit, or any combination of such circuits.

The battery pack 102 includes one or more batteries 203 for providing power to the system 200. The battery 203 may be a lithium ion battery in one embodiment. The battery pack 102 supplies power to the load 240 through the discharge switch 209. In one embodiment, the discharge switch may be a Field Effect Transistor (FET). The battery pack 102 also includes monitoring and control circuitry 208. The monitoring and control circuitry 208 measures one or more of the battery pack current, temperature, and battery voltage values for each battery.

The monitoring circuit 208 compares the measured values to the associated threshold values and identifies an overload condition if one of the measured values is greater than or equal to the associated threshold value monitoring circuit 208. For example, the overload condition may be a discharge current that is greater than or equal to a threshold value indicative of a maximum discharge current. In another example, the overload condition may be a charging current value provided to the battery 203 that is greater than or equal to a threshold value indicative of a maximum charging current. In another example, the overload condition may be a voltage value of a battery that is greater than or equal to a voltage threshold. In another embodiment, the overload condition may be a temperature of an element greater than or equal to a temperature threshold. The monitoring circuit 208 provides an output control signal for protecting the components of the power supply system 200 when an overload condition is detected. The output control signal is provided to one or more switches of the battery pack 102 or as a control input to other circuitry external to the battery pack 102 via path 127. In one embodiment, the output control signal is provided to the discharge switch 209 to open the switch 209, wherein the overload condition is a discharge current from the battery 203 that is greater than or equal to a maximum discharge current threshold.

The monitoring and control circuitry 208 also provides a control signal to the discharge switch 209 in response to the position of the trigger 104. The control signal may be a Pulse Width Modulation (PWM) signal 218 in one embodiment, and the discharge switch 209 controls the discharge current in response to the duty cycle of the PWM signal 218. The PWM signal 218 operates at a fixed frequency, such as 5 to 10 kilohertz (KHz). As the duty ratio of the PWM signal increases, the closing time of the discharge switch 209 also increases, and thus the discharge current value supplied to the load 240 increases. Similarly, as the duty cycle of the PWM signal decreases, the on time of the discharge switch 209 decreases, and thus the value of the discharge current provided to the load 240 decreases.

The tool identification circuit 230 provides a tool identification signal to the monitoring and control circuit 208. The tool identification signal represents data specific to the cordless power tool, such as power parameters for a particular cordless power tool. For example, the tool identification signal may indicate a maximum discharge current for the particular cordless power tool. For example, the tool identification signal may also represent a thermal overload point (hot overload point) of the cordless power tool. In one embodiment, the monitoring and control circuitry 208 provides a stimulus signal to the tool identification circuitry 230 and the tool identification signal is provided in response to the stimulus signal.

The tool identification circuit 230 also helps to confirm whether the battery pack 102 is properly connected to the cordless power tool and whether the battery pack supports the type of the particular cordless power tool. For example, if the battery pack 102 is not properly connected to the portable power tool, the tool identification circuit 230 may not provide a tool identification signal. In response, the battery pack 102 refuses to provide discharge current unless it receives an appropriate tool identification signal, thereby improving the safety of the system.

A universal battery pack may be connected to different cordless power tools, but may only support certain selected tools. Misconnection of the battery pack to the wrong cordless power tool may cause degradation in tool performance or create safety issues. Preferably, the tool identification circuit 230 provides a tool identification signal indicative of the type of the particular cordless power tool. If the battery pack 102 does not support the tool, the battery pack will refuse to provide discharge current and provide an indication of the event, which further improves the safety of the system.

Fig. 2A illustrates one embodiment 230a of the tool id circuitry 230 of fig. 2. The tool id circuit 230a includes a simple fixed resistor 250 having a fixed resistance value. The fixed resistance value is indicative of a characteristic of the particular cordless power tool. For example, the characteristic may be a thermal overload point for the particular cordless power tool. The fixed resistor 250 receives a stimulation signal, such as a current signal, from the monitoring and control circuit 208. The tool identification circuit 230 then responds to the stimulus signal and effectively provides the tool identification signal back to the monitoring and control circuitry 208. The resistance value of the fixed resistor 250, and a known stimulus signal, provide a predictable response that can be measured and correlated to a particular tool characteristic.

Fig. 2B illustrates another embodiment 230B of the tool identification circuit of fig. 2. The tool identification circuit includes inexpensive passive components such as a capacitor 252 and a resistor 254 in parallel.

FIG. 2C illustrates one embodiment of the monitoring and power control circuitry 208a that functions in conjunction with the tool id circuitry 230a/230B of FIGS. 2A and 2B. The monitoring and control circuit includes a current source 270, switch SW1, analog-to-digital converter (ADC)272, processor 285, and memory 287. The current source 270 provides a relatively small constant current, e.g., 1 milliamp, up to some maximum voltage Vmax. The ADC272 reads the voltage output of the current source 270 and provides an output to the processor 285. The switch SW1 is closed when the battery pack 102a is not connected to the cordless power tool. Switch SW1 is controlled directly or indirectly by processor 285. Since current source 270 is unloaded, the voltage output of current source 270 will increase to its maximum voltage value Vmax.

When the battery pack 102a is connected to the cordless power tool, the current source 270 provides a stimulation signal, such as a current signal, to the tool id circuitry 230a/230 b. The tool id circuit then effectively provides a tool id signal to the monitor and control circuitry 208a based on the resistance value of the fixed resistor 280, since the resistive load of the resistor 280 will be connected to the current source 270. Resistor 280 may be a separate resistor 250 in the embodiment of fig. 2A or resistor 254 in the embodiment of fig. 2B. The value of the resistor 280 controls the voltage drop of the current source 270 from Vmax, which is converted by the ADC272 and provided to the processor 285. The processor 285 then correlates the measured voltage value of the current source or the voltage drop from Vmax of the current source to a particular cordless power tool characteristic, such as by accessing data from the memory 287. A power tool characteristic may represent an overcurrent limit. If the measured value of the resistance is too small, for example less than 100 ohms, which can be considered a short circuit of the Vsense port 222 with the Vpack port 290, then the tool is disabled.

Since the embodiment of fig. 2B has capacitor 252 and resistor 254 (or 280 of fig. 2C) in parallel, processor 285 opens switch SW1 after decoding the first tool characteristic information taken from resistor 280. This will cause the capacitor 252 to discharge through the resistor 280. The processor 285 then correlates the measured discharge time to a second cordless power tool characteristic, such as a thermal overload point of the cordless power tool, by, for example, accessing data from the memory 287. This may also be accomplished by the battery pack 102 being connected to the cordless power tool if the charging time of the capacitor 252 is monitored and correlated to a tool characteristic.

Other embodiments of the tool id circuitry 230 include other methods, such as using a microcontroller in the tool id circuitry 230 that can communicate with the monitoring and control circuitry 208. A digital serial bus may also be used in other embodiments for communication between the tool id circuitry 230 and the monitoring and control circuitry 208.

Fig. 3 is a circuit diagram of a power supply system 300 associated with the power supply system 200 of fig. 2. Elements in fig. 3 that are similar to those in fig. 2 are labeled with the same parameters, so any repetitive description is omitted here for clarity. The load 240a of fig. 3 may be a motor 340 for driving the element 142 through an associated gear train (not shown). For example, the element 142 may be a chuck of the drill of fig. 1 used to control the drill bit of the drill. It would be advantageous to eliminate the conventional speed control switch on the input side of the motor 340 in a cordless power tool. In its place, the discharge switch 209 controls the discharge current and thus the speed of the element 142 driven by the motor 340.

The speed selection circuit 316 receives a signal from the trigger 104 indicative of the trigger 104 position, i.e., the desired speed of the cordless power tool element 142. The speed selection circuit 316 then provides an input signal indicative of the desired speed to the monitoring and control circuitry 208 of the battery pack 102. The monitoring and control circuit 208 then provides a control signal to the discharge switch 209 to control the speed of the element 142 by controlling the discharge current provided to the motor 340.

In operation of the cordless power tool, a user depresses the trigger 104 a desired amount to control the speed of the element 142. The speed selection circuit 316 provides an input signal to the monitoring and control circuit 208 in response to the position of the trigger 104. The monitoring and control circuit 208 includes a PWM generator that modifies the duty cycle of the PWM signal 218 in response to an input signal to the speed selection circuit 316. The PWM signal 218 operates at a fixed frequency, for example 5 to 10 khz. As the duty cycle of the PWM signal increases, the on time of the discharge switch 209 increases, and thus the speed of the cordless power tool element 142 increases. Similarly, as the duty cycle of the PWM signal is decreased, the closing time of the discharge switch 209 is decreased, and thus the speed of the component 142 of the power tool is decreased. In one example, the duty cycle of the PWM signal may vary from about 10% (slow) to 75% (fast).

Fig. 4 is another circuit diagram of the power supply system of the cordless power tool of fig. 1. The discharge switch 209 may be a field effect transistor Q1. The field effect transistor Q1 may be a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), such as a p-channel MOSFET (pmos) or an n-channel MOSFET (nmos). The battery pack 102b also includes a plurality of batteries 203-1, 203-2, …, 203- (n-1), and 203-n. The battery pack 102b provides power to a plurality of loads, including a load 240b, which is represented as a motor winding. The diode 410 is connected in parallel with the field effect transistor Q1 to allow a charging current to flow into the batteries 203-1, 203-2, …, 203- (n-1), and 203-n and to prevent a discharging current from the batteries. The battery pack 102a includes a selectable status indicator 406 for providing an indication of different measured conditions from the monitoring and control circuitry 208.

The speed select circuit 316a includes a variable resistor 454 in series with another resistor 452. The variable resistor 454 may be a potentiometer. The resistance value of the variable resistor 454 is set in response to the position of the trigger 104. The resistance value of variable resistor 454 thus represents the desired speed of element 142 (see fig. 3). The resistance of resistor 452 represents a maximum discharge current rate. The speed selection circuit 316a allows for inexpensive discharge limiting and/or variable power control in view of low cost cordless power tools, such as flashlights. The monitoring and control circuitry 208 receives information from the speed selection circuitry 316a regarding the desired speed using the third battery pack port 422. The monitoring and control circuitry 208 then provides a PWM signal 218 at a particular duty cycle to achieve the desired speed.

Fig. 5 shows another embodiment 208b of the monitoring and control circuitry 208. The monitoring and control circuit 208b includes a switching network 502, an analog-to-digital converter (ADC)504, a processor 506, a driver 508, a memory 534, a protection circuit 524, and a PWM generator 510. Processor 506 instructs switching network 502 to select a particular one of batteries 203-1, 203-2, …, 203- (n-1), and 203-n to monitor. The respective analog cell voltage values for each cell are then sampled through a switching network 502. The sampled analog signals are then converted to associated digital signals by the ADC 504 and provided to the processor 506. The processor 506 thus receives digital signals from the ADC 504 representing the voltage values of the respective cells 203-1, 203-2, …, 203- (n-1), and 203-n and compares these signals to different voltage thresholds.

For example, as the battery pack 102 is being charged, the monitoring and control circuitry 208a monitors the battery voltage values to determine if any of the battery voltage values exceed an over-voltage threshold. If there is a battery voltage that exceeds the threshold, then the processor 506 will take some precautionary action. For example, charging may be stopped by providing a signal to the driver 508 to open a particular switch. For example, as the battery pack 102 discharges, the monitoring and control circuitry 208a monitors the voltage level to determine if any of the battery voltage levels are less than an under-voltage threshold. If there is a battery voltage that is less than the under-voltage threshold, the processor 506 may take some precautionary action. For example, the discharge may be stopped by providing a signal to the driver 508 to open a particular switch.

Processor 506 also commands switch network 502 to close a switch (e.g., switch SW1 of fig. 2C) to cause ADC 504 to monitor the voltage of current source 270 (see fig. 2C). The current source 270 then provides a stimulus signal, such as a current signal, to the tool id circuitry, and the tool id circuitry then effectively provides a tool id signal to the monitoring and control circuitry 208b, which can be measured and correlated to a particular tool characteristic by, for example, accessing data from the memory 534 to correlate the different measured values to different tool characteristics.

The processor 506 also receives other signals from the protection circuit 524. The protection circuit 524 typically monitors the current flowing into (charge mode) or out of (discharge mode) the battery pack 102 to discover different current overload conditions, such as an overcurrent or short circuit condition, and alerts the processor 506 to these conditions to take precautionary action. For example, a current sensing element, such as sense resistor 404 (fig. 4), may provide a signal to the protection circuit 524 indicative of the value of the current flowing into or out of the battery pack as it changes. The protection circuit 524 compares the current value to different thresholds and provides a signal to the processor 506 informing the processor of an overcurrent condition or a short circuit condition so that the processor 506 can take precautionary measures.

The PWM generator 510 receives a signal from the speed selection circuit 316, 316a and provides an output PWM signal to a discharge switch, such as a field effect transistor Q1 (see fig. 4). The processor 506 allows the PWM signal to control the state of the discharge switch until an overload condition occurs. When an overload condition occurs, such as additional discharge current, the processor 506 disables the PWM generator 510 and commands the driver 508 to open the discharge switch. Thus, the monitoring and control circuit 208a may advantageously enable the PWM generator 510 to control the discharge switch 209 at the appropriate time, and the monitoring and control circuit 208a may also disable the PWM generator 510 and open the discharge switch when an overload condition is monitored.

Figure 6 illustrates an operational flow diagram 600 of one embodiment. Operation 602 includes connecting a battery pack to a cordless power tool. Operation 604 includes providing a tool identification signal from the cordless power tool to the battery pack once the battery pack is properly connected to the cordless power tool, the tool identification signal representing data specific to the cordless power tool.

Advantageously, the tool id circuitry allows the battery pack to receive data for a particular tool, which would otherwise not be known. Such data includes data representing the maximum discharge current of the particular cordless power tool, or a thermal overload point of the particular tool to indicate a connection. Additionally, the tool recognition circuitry may provide a useful secondary indication: the battery pack has been properly inserted into the appropriate cordless power tool. In the absence of an appropriate tool identification signal, the battery pack will refuse to discharge thereby improving the safety of the system.

The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described (or portions thereof), it being recognized that various modifications are possible within the scope of the invention claimed. Other modifications, variations, and alternatives are also possible. Therefore, the claims are intended to cover all such equivalents.

Claims (16)

1. A cordless power tool, comprising:

tool identification circuitry providing a tool identification signal to a battery pack, the tool identification signal representing data specific to the cordless power tool, the data including a threshold value for a power parameter of the cordless power tool;

wherein the cordless power tool includes the battery pack, the battery pack includes monitoring and control circuitry that compares at least one monitored state value to the threshold value.

2. The cordless power tool of claim 1, wherein said data includes a maximum discharge current of said cordless power tool.

3. The cordless power tool of claim 1, wherein the data includes a thermal overload point of the cordless power tool.

4. The cordless power tool of claim 3, wherein said tool identification circuit includes a resistor having a fixed resistance value, said battery pack providing a stimulus signal to said resistor when said battery pack is connected to said cordless power tool, and wherein said tool identification signal includes a response to said stimulus signal.

5. The cordless power tool of claim 1, wherein the tool identification circuit comprises a resistor and a capacitor connected in parallel, the resistor providing the tool identification signal indicative of an overload current limit of the cordless power tool, and the capacitor providing the tool identification signal indicative of a thermal overload point of the cordless power tool.

6. A method of identification of a cordless power tool, comprising:

connecting a battery pack to a cordless power tool; and

providing a tool identification signal from the cordless power tool to the battery pack once the battery pack is properly connected to the cordless power tool, the tool identification signal representing data specific to the cordless power tool, the data including a threshold value for a power parameter of the cordless power tool;

wherein the battery pack includes a monitoring and control circuit that compares at least one monitored state value to the threshold value.

7. The cordless power tool identification method of claim 6, wherein said data includes a maximum discharge current of said cordless power tool.

8. The cordless power tool identification method of claim 6, wherein the data comprises a thermal overload point of the cordless power tool.

9. The cordless power tool identification method of claim 6, wherein the tool identification signal is not provided to the battery pack if the battery pack is not properly connected to the cordless power tool, and the battery pack refuses to provide a discharge current into the cordless power tool if the battery pack does not receive the tool identification signal.

10. The cordless power tool identification method of claim 6, wherein the threshold is a threshold for a maximum discharge current of the cordless power tool.

11. The cordless power tool identification method of claim 6, wherein if the tool identification signal indicates that a particular cordless power tool type is not supported by the battery pack, the battery pack refuses to provide a discharge current to the cordless power tool.

12. The method of claim 6, wherein the battery pack provides a stimulus signal to the tool identification circuit, and wherein the tool identification signal comprises a response to the stimulus signal.

13. A battery pack, comprising:

at least one battery; and

monitoring and control circuitry coupled to the battery, the monitoring and control circuitry receiving a tool identification signal from a cordless power tool once a battery pack is properly connected to the cordless power tool, the tool identification signal indicating data specific to the cordless power tool, the data including a threshold value of a power parameter of the cordless power tool, the monitoring and control circuitry comparing at least one monitored state value to the threshold value.

14. The battery pack of claim 13, wherein the threshold is a threshold for a maximum discharge current of the cordless power tool, and the monitoring and control circuit monitors a discharge current of the battery and compares the discharge current to the threshold for the maximum discharge current and provides an output signal if the discharge current is greater than or equal to the threshold for the maximum discharge current.

15. The battery pack of claim 13, wherein the battery pack denies a discharge current to the cordless power tool if the tool identification signal indicates that a particular cordless power tool type is not supported by the battery pack.

16. The battery pack of claim 13, wherein the monitoring and control circuitry further provides a stimulus signal to the cordless power tool, and wherein the tool identification signal comprises a response to the stimulus signal.