Method for efficient discharge of rechargeable batteries

Abstract

The invention provides a method for open- and closed-loop control of a power tool having at least one rechargeable battery, a drive and at least one control device, the rechargeable battery serving as an energy source for the power tool. The method comprises the following method steps: recording at least one temperature value of the rechargeable battery by means of a temperature measuring device; recording at least one first voltage value of the rechargeable battery by means of a voltage measuring device; and setting a first performance parameter value of the power tool to a second performance parameter value of the power tool for setting a current intensity value if the recorded temperature value corresponds to a predetermined temperature threshold value and the recorded voltage value corresponds to a predetermined voltage threshold value. A system is also provided, comprising a power tool and at least one rechargeable battery for supplying the power tool with electrical energy for carrying out the method.

Description

Technical Field

[0001] The present invention relates to a method for open-loop and closed-loop control of a power tool having at least one rechargeable battery, a driver, and at least one control device, the rechargeable battery serving as the power tool's energy source.

[0002] Furthermore, the present invention relates to a system comprising a power tool and at least one rechargeable battery for supplying electrical energy to the power tool to perform the method according to the invention. Background Technology

[0003] Modern power tools (such as hammer drills, saws, grinders, etc.) have

[0004] When using rechargeable batteries as a power source for power tools, a problem arises because the batteries heat up due to the internal resistance (also known as output resistance) of the individual cells when delivering electrical energy. For safety reasons, energy delivery from the rechargeable battery ends when the individual cells reach or exceed a critical temperature threshold. The drawback here is that when the temperature threshold is reached, the rechargeable battery is often not fully discharged, or there is still capacity (voltage) remaining in the individual cells, which is no longer usable by the user of the power tool. In other words, the full capacity of the rechargeable battery cannot be used due to premature overheating of the individual cells. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a method for open-loop and closed-loop control of a power tool having at least one rechargeable battery, which solves the above-mentioned problems and ensures that the available capacity of the rechargeable battery is used as the energy source of the power tool as efficiently as possible before the individual rechargeable battery cells overheat.

[0006] This objective is achieved through the subject matter of this invention.

[0007] This objective is achieved in particular by a method for open-loop and closed-loop control of a power tool having at least one rechargeable battery, a drive, and at least one control device, the rechargeable battery serving as the power tool's energy source.

[0008] According to the present invention, the method includes the following steps:

[0009] - Record at least one temperature value of the rechargeable battery using a temperature measuring device;

[0010] - Record at least one first voltage value of the rechargeable battery using a voltage measuring device; and

[0011] - If the recorded temperature value corresponds to a predetermined temperature threshold and the recorded voltage value corresponds to a predetermined voltage threshold, then the first performance parameter value of the power tool is set as the second performance parameter value of the power tool to set the current intensity value.

[0012] According to an advantageous embodiment of the present invention, the method may include the following method steps:

[0013] - The set current intensity value is stored in the memory device of the rechargeable battery;

[0014] - The current intensity value is sent from the rechargeable battery's memory device to the power tool's control device; and

[0015] - When the rechargeable battery exceeds a predetermined charging value, the current intensity value is set by setting at least one performance parameter value of the power tool.

[0016] According to an advantageous embodiment of the invention, the performance parameter of the power tool may be the speed value or the torque value of the drive.

[0017] Furthermore, this objective is achieved by a system comprising a power tool and at least one rechargeable battery for supplying electrical energy to the power tool to perform the method. Attached Figure Description

[0018] Further advantages will become apparent in the following description of the accompanying drawings. Several different exemplary embodiments of the invention are illustrated in the drawings. The drawings and description contain many combinations of features. Those skilled in the art will also readily consider these features individually and combine them into useful further combinations.

[0019] In the attached diagram:

[0020] Figure 1 A cross-section through a system according to the invention is shown, the system comprising a power tool and a rechargeable battery connected thereto; and

[0021] Figure 2 The figure shows a graphical representation of voltage drop, temperature rise, and current intensity curves during the use of a rechargeable battery to supply power to a power tool. Detailed Implementation

[0022] Figure 1 A system 1 according to the present invention is shown, comprising a power tool 2 and a rechargeable battery 3. The rechargeable battery 3 is connected to the power tool and is used to supply electrical energy to the electrical load of the power tool 2. During the supply period, current flows from the rechargeable battery 3 to the power tool 2.

[0023] According to an alternative embodiment of the invention, the power tool 2 can be powered via a network connection instead of at least one rechargeable battery. The network connection can also be referred to as a power cable. This alternative embodiment of the invention is not shown in the figures.

[0024] like Figure 1 As shown, the power tool 2 is illustrated as a screwdriver operated by a rechargeable battery. According to other alternative embodiments, the power tool 2 may also be designed as a power drill, saw, grinder, etc.

[0025] The power tool 2, designed as a screwdriver operated by a rechargeable battery, generally includes a housing 4, a handle 5, a base 6, a tool assembly 7, an electric actuator in the form of an electric motor 8, a control device 9, a transmission mechanism 9a, an input shaft 11, an output shaft 12, and an activation switch 13.

[0026] An electric drive 8, designed as an electric motor, a transmission mechanism 10, an input shaft 11, an output shaft 12, and a control device 9 are positioned within a housing 4. The drive 8, transmission mechanism 10, input shaft 11, and output shaft 12 are positioned relative to each other and within the housing 4, such that the torque generated by the drive 8 is transmitted to the output shaft 12. The output shaft 12 transmits the torque to the transmission mechanism 10, which in turn transmits the torque to the input shaft 11. The tool assembly 7 is driven by the input shaft 11 by transmitting torque. Figure 1 As shown, a bit-shaped tool 14 is held in the tool assembly 7. The bit allows screws to be screwed into the material. Neither the screw nor the material is shown in the accompanying drawings.

[0027] like Figure 1 As also shown, housing 4 includes a top side 4a and a bottom side 4b. Handle 5 includes a first end 5a and a second end 5b. The first end 5a of handle 5 is fixed to the bottom side 4b of housing 4. Additionally, base 6 includes an upper end 6a and a lower end 6b. The upper end 6a of base 6 is fixed to the second end 5b of handle 5. The lower end 6b of base 6 includes a mechanical, electrical, and electronic interface 15 for mechanical, electrical, and electronic connections to the rechargeable battery 3. For drawing current, interface 15 includes multiple power connectors. Interface 15 also includes a data connector for transmitting and receiving signals between power tool 2 and rechargeable battery 3.

[0028] You can also from Figure 1 As can be seen, the control device 9 of the power tool 2 is located in the base 6 of the power tool 2. The control device 9 of the power tool 2 is used for open-loop and closed-loop control of various processes related to the power tool 2 and the rechargeable battery 3. The control device 9 specifically controls the current or current intensity flowing from the rechargeable battery 3 to the power tool 2 and is specifically used to drive the driver 8, which is configured as an electric motor.

[0029] The control unit 9 of the power tool 2 includes a microcontroller 18 (also referred to as an MCU) and a data interface with a first transceiver as part of a communication circuit for communication (i.e., data and signal exchange) between the rechargeable battery 3 and the power tool 2.

[0030] The rechargeable battery 3 basically includes a housing 21 with a rechargeable battery interface 22, multiple energy storage cells 23, control electronics 24, and a temperature measuring device 27. The control electronics 24 further includes a microcontroller 25, a voltage measuring device 26, and a memory device 28.

[0031] The temperature measuring device 27 can also be called a temperature sensor.

[0032] The rechargeable battery 3 also includes a data interface with a second transceiver as a component of a communication circuit for communication between the rechargeable battery 3 and the power tool 2.

[0033] The energy storage cell 23 can also be referred to as a rechargeable battery cell and is used to access, store and provide electrical energy or voltage.

[0034] The rechargeable battery interface 22 is located on one side of the housing 21. The rechargeable battery interface 22 includes multiple power connectors for drawing and delivering current, and also includes a data connector for transmitting and receiving signals between the power tool 2 and the rechargeable battery 3. Current from the energy storage cell 23 can be delivered via the power connectors.

[0035] like Figure 1 As shown, the power tool 2 is connected to the rechargeable battery 3, such that the power connector of the rechargeable battery 3 is also connected to the power connector of the power tool 2. Similarly, the data connector of the rechargeable battery 3 is connected to the data connector of the power tool 2.

[0036] Through the connection, current can flow from the energy storage cell 23 of the rechargeable battery 3 to the power tool 2. Furthermore, signals can be exchanged between the rechargeable battery 3 and the power tool 2 for communication.

[0037] From Figure 1As can be seen, the activation switch 13 is positioned on the front side 5c of the handle 5. The movement of the activation switch 13 in direction A results in a signal being transmitted from the activation switch 13 to the controller 9, which in turn transmits the signal to the control electronics 24 of the rechargeable battery 3. The signal transmitted to the control electronics 24 enables the release of electrical energy or current with a specific current value from the rechargeable battery 3 for use with the electrical load of the power tool 2, and particularly for the drive 8, which is configured as an electric motor. The power tool 2 has a current measuring device (not shown) capable of measuring the current intensity of the supplied current. If a supply current with an allowable current intensity is measured, the supply current can flow to the electrical load of the power tool 2. Alternatively or additionally, the current measuring device may also be located in the rechargeable battery 3.

[0038] In order to transmit a signal corresponding to the travel of the activation switch 13 in direction A to the controller 9, the activation switch 13 includes a potentiometer (not shown).

[0039] If the activation switch 13 moves again in direction B, a corresponding signal is transmitted to the controller 9 by means of a potentiometer (not shown), resulting in current no longer flowing from the rechargeable battery 3 to the power tool 2.

[0040] During the delivery of electrical energy, the energy storage cell 23 generates heat. The temperature profile of the rechargeable battery cell is recorded by the temperature measuring device 27 (see...). Figure 2 During the delivery of electrical energy from the rechargeable battery to the power tool, the temperature of the rechargeable battery cells typically ranges between 25°C and 70°C. The voltage at each rechargeable battery cell is recorded using a voltage measuring device 26. In the charging state, the voltage of a rechargeable battery cell is 4.2 volts, and in the discharging state, the voltage is 2.5 volts.

[0041] When the temperature of a single rechargeable battery cell rises above 70°C and the voltage of a single rechargeable battery cell drops below 2.5 volts, the control electronics 24 of the rechargeable battery 3 stops delivering electrical energy to the power tool 2.

[0042] To prevent the delivery of electrical energy from the rechargeable battery to the power tool from prematurely reaching the critical temperature threshold of the rechargeable battery cell 23, the power of the power tool is reduced accordingly. For this purpose, the speed of the drive 8 is reduced by means of the control device 9. By reducing the speed of the drive 8, the value of the current intensity flowing from the rechargeable battery cell 23 to the drive 8 of the power tool is reduced. Due to the lower current intensity, the temperature rise at the rechargeable battery cell is slower, allowing voltage (i.e., electrical energy) to be drawn from the rechargeable battery cell for a longer period of time.

[0043] Furthermore, the current intensity value in the rechargeable battery cell 23 that achieves the slowest possible temperature rise is stored in the memory device 28 of the rechargeable battery 3. When the rechargeable battery 3 is fully charged to be used again as a power source for the power tool 2, the current intensity value in the rechargeable battery cell 23 that achieves the slowest possible temperature rise is sent to the control device 9 of the power tool 2. With the aid of this determined current intensity value, the power output of the driver 8 is set or selected in a manner that prevents the temperature at the rechargeable battery cell 23 from rising too quickly and allows the rechargeable battery cell 23 to be almost completely discharged.

Claims

1. A method for open-loop and closed-loop control of a power tool (2), the power tool having at least one rechargeable battery (3), a driver (8), and at least one control device (9), the rechargeable battery (3) serving as an energy source for the power tool (2), Its characteristics are The following methods step - Record at least one temperature value of the rechargeable battery (3) using a temperature measuring device (27); - Record at least one first voltage value of the rechargeable battery (3) using a voltage measuring device (26); -If the recorded temperature value corresponds to a predetermined temperature threshold and the recorded voltage value corresponds to a predetermined voltage threshold, then the first performance parameter value of the power tool (2) is set as the second performance parameter value of the power tool (2) to set the current intensity value, wherein, in order to prevent the delivery of electrical energy from the rechargeable battery to the power tool from reaching the critical temperature threshold of the rechargeable battery too early, the power of the power tool is reduced accordingly, thereby ensuring that the available capacity of the rechargeable battery is effectively used as the energy source of the power tool before the rechargeable battery overheats; - The set current intensity value is stored in the memory device (28) of the rechargeable battery (3); - The current intensity value is sent from the memory device (28) of the rechargeable battery (3) to the control device (9) of the power tool (2); and - When the rechargeable battery (3) exceeds a predetermined charging value, the current intensity value is set by setting at least one performance parameter value of the power tool (2). The current intensity value that achieves the slowest possible temperature rise in the rechargeable battery (3) is stored in the memory device (28) of the rechargeable battery (3). When the rechargeable battery (3) is fully charged to be used again as the energy supply unit of the power tool (2), the current intensity value that achieves the slowest possible temperature rise in the rechargeable battery (3) is sent to the control device (9) of the power tool (2). With the help of the determined current intensity value, the power output of the driver (8) can be set or selected just when the rechargeable battery (3) is started to be used, so as to prevent the temperature at the rechargeable battery from rising too fast and to achieve almost complete discharge of the rechargeable battery (3).

2. The method as described in claim 1, Its features are, The performance parameters of the power tool (2) are the speed value or the torque value of the drive (8).

3. A system comprising a power tool (2) and at least one rechargeable battery (3) for supplying electrical energy to the power tool (2) to perform the method as claimed in claim 1 or 2.

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