WO2020126731A1

WO2020126731A1 - Display apparatus for an electric tool

Info

Publication number: WO2020126731A1
Application number: PCT/EP2019/084592
Authority: WO
Inventors: Marcin Rejman; Mickael Segret; Christoph Klee
Original assignee: Robert Bosch Gmbh
Priority date: 2018-12-20
Filing date: 2019-12-11
Publication date: 2020-06-25
Also published as: DE102018222485A1

Abstract

The present invention relates to a display apparatus (100) for an electric tool (200), comprising: an illuminated display (110) having at least one LED (111, 112, 113, 114, 115); a control device (120) for controlling the illuminated display (110); and a light sensor (140) designed to detect the ambient brightness. The control device (120) is designed to control the illumination intensity of the illuminated display (110) on the basis of the ambient brightness detected with the aid of the light sensor (140).

Description

description

title

Power tool display device

The invention relates to a display device for a power tool. Furthermore, the invention relates to a power tool or an accessory for such a power tool with a corresponding display device.

Power tools and accessories for such power tools, such as batteries or chargers, are often equipped with light indicators. For example, the state of charge or an operating state is indicated by means of LEDs on the battery or directly on the power tool. The

The fact that the charge status display for the user must be easily accessible and visible, as well as other constraints often lead to the fact that the charge status display is spatially separated from the rest of the electronics of the

Battery packs or the power tool is arranged. To make a self-illuminating display interpretable for a user, the contrast between illuminated and non-illuminated elements must be as large as possible. In the case of a luminous display, there is therefore the need to make the light intensity of the luminous element considerably greater than that of a non-luminous element. However, the perception of the

Light intensity of a light display also depends on the external one

Lighting situation. For example, a light indicator that is easily recognizable in low ambient lighting is less easy to recognize for the user in the case of relatively strong lighting from the sun or artificial light. On the other hand, a light display with strong intensity, which it with strong

Ambient lighting makes it easy to read, with less

Ambient lighting can cause glare to the user.

As a result, light points lying next to one another, for example, can no longer be correctly distinguished from one another by the eye. It is therefore an object of the invention to provide a possibility for adapting the display unit to the ambient brightness. This object is achieved by a display device according to claim 1. Furthermore, the object is achieved by an electric tool according to claim 9 and an accessory part for an electric tool according to claim 10. More beneficial

Embodiments are specified in the dependent claims.

According to the invention, a display device for a power tool is provided, which has a light display with at least one LED, a

Control device for controlling the light display and a light sensor designed to detect the ambient brightness. The control device is designed to control the luminosity of the luminous display in

Controlling dependence on the ambient brightness detected with the light sensor. By adapting the luminosity to the ambient brightness, the reading of the light display becomes a relatively bright and relatively dark

Environments improved. In particular, by increasing the

Luminosity of the contrast between illuminated and non-illuminated elements of the illuminated display, which is typically reduced in the case of particularly strong ambient lighting, is increased. On the other hand, a reduction in the luminosity reduces the glare that typically occurs in particularly weak ambient lighting and thus increases the resolution of the illuminated display that can be perceived by the user. By adjusting the display brightness to the ambient brightness, the user can be dazzled

dimly lit environment can be avoided and at the same time

ensure that the display is easy to read even under bright ambient lighting.

In one embodiment it is provided that the light display comprises an at least partially transparent window structure, the LED and the light sensor being arranged together behind the window structure. This arrangement of the light sensor enables an optimal measurement of the

Ambient brightness directly at the light source. At the same time, the structure is simplified since no separate window structure is required for the light sensor. According to a further embodiment, the control device is designed to deactivate the LED for a short period of time at defined time intervals and to detect the ambient brightness by means of the light sensor during the time in which the LED is deactivated. This effectively prevents the measurement of the ambient brightness using the light sensor from being falsified by the light from the adjacent LED.

According to a further embodiment, the control device is designed to control the LED using a control signal modulated by means of pulse width modulation. Furthermore, the control device is designed to detect the ambient brightness by means of the light sensor in a switch-off phase

Pulse width modulation to record modulated control signal. Using the switch-off phases of pulse width modulation enables a particularly simple measurement of the ambient brightness.

According to a further embodiment, the LED is designed to emit light radiation with at least one defined wavelength. The light sensor has a reduced sensitivity for the at least one wavelength of the light radiation emitted by the LED. This measure enables the ambient brightness to be measured independently of the control of the LED.

In a further embodiment it is provided that the LED has a luminous intensity which varies with the temperature. The control device is designed to determine the temperature of the LED with the aid of a temperature sensor and to compensate for a temperature-dependent change in the luminous intensity on the basis of the determined temperature. As a result, temperature-related luminous intensity variations can be largely compensated for.

In a further embodiment it is provided that the LED as

Temperature sensor is used. The control device is designed to detect a temperature-dependent forward voltage of the LED and to determine the temperature of the LED by evaluating the detected forward voltage. This measure can be used on a separate temperature sensor to be dispensed with. At the same time, the use of the LED enables

Temperature sensor a particularly precise determination of the temperature of the LED.

According to a further embodiment, the control device is designed to determine the temperature determined using the bias of the LED

Plausibility check of the measurement results of another temperature sensor. In this way, the other can be checked

Temperature sensor, which is arranged for example in the power tool or in the corresponding accessory, has a defect. This increases the operational safety of the power tool or the corresponding accessory.

In a further embodiment it is provided that the light display is in the form of a charge status display. Is often arranged in the immediate field of vision of the user an improvement in the illuminated display thus increases the ease of use of the power tool or the corresponding accessory.

The invention is described in more detail below with reference to figures. Show:

Fig. 1 shows schematically a battery-operated power tool with a

Housing of the power tool arranged display device;

Fig. 2 schematically shows a battery-operated power tool with a

Housing of the battery park arranged display device;

Fig. 3 is a block diagram of the display device;

4 shows a battery pack with a charge status indicator;

5 shows a digital control circuit implemented by means of a microcontroller for

Control an LED light indicator;

6 shows an analog control circuit for controlling an LED light indicator; 7 shows the digital control circuit from FIG. 5 with a temperature sensor,

8 shows the digital control circuit from FIG. 7, in which the LED is used as an additional temperature sensor.

FIG. 1 shows a schematic representation of a means of a

Exchangeable batteries 300 powered electric tool 200, which is designed in the present embodiment in the form of a cordless screwdriver. Such a power tool 200 generally has at least one light indicator 110 for displaying certain information in the

Connection with the operation of the power tool 200. These include, for example, the current operating state or operating mode of the

Power tool 200 or a power tool accessory 300 as well as other information of interest to the user, such as, for example, the currently set speed or the current charge status, the currently set gear, the current direction of rotation, the current device temperature, etc. Such light indicators 110, which are generally realized with the aid of light-emitting diodes (LED) 111, 112, 113, 114, 115, are typically arranged on the housing 210 of the power tool 200 or on the housing 310 of the rechargeable battery 300 in a manner that is clearly visible to the user. In the case of the power tool 200 shown in FIG. 1, the light indicator 110 is in an upper part of the

Power tool housing 210 arranged and in the form of a

Charging status display is formed, which comprises a plurality of light-emitting diodes 111 to 115 each forming individual LED segments. For reasons of clarity, only the first and the last LED 111, 115 have been provided with a reference symbol. The individual LEDs 111 to 115 are generally mounted on a printed circuit board in a spatially separated manner and are visible through a transparent window structure 116 formed in the housing 210. The transparent window structure 116 can be designed in the form of a transparent cover or in the form of a light-guiding element and, depending on the particular design, can be designed as a separate window structure for individual LEDs 111 to 115 or as a common window structure for all LEDs 111 to 115. The transparent window structure 116 can also be diffuse be formed so that an LED 111 to 115 arranged behind the window structure 116 appears to be areally illuminated to the viewer.

The illuminated display 110 forms part of a display device 100 housed in the power tool housing 210, which also further comprises a control device 120 for controlling the illuminated display 110.

According to the invention, the lighting device 100 also includes one

Light sensor 140 for detecting the ambient brightness. The control device 120 is designed to determine the brightness of the surroundings of the power tool 200 using the light sensor 140, which is preferably arranged in the immediate vicinity of the light display 110, and to determine the brightness of the display or

Luminosity of the light display 110 corresponding to the measured

Adjust ambient brightness. The luminosity of the

Illuminated display 110 increased at a high measured ambient brightness in order to increase the contrast between illuminated and non-illuminated elements and thus to improve the readability. If, on the other hand, a low ambient brightness is measured, the control device 120 reduces it

Luminosity of the light display 110 in order to avoid glare to the user in dimly lit surroundings.

Figure 2 shows an alternative embodiment in which the

Lighting device 100 with the light indicator 110 is arranged inside the housing 310 of the battery 300 serving as an accessory for the electrical device 200. In principle, such a lighting device 100 can also be provided on other accessories of the power tool 200, such as a charger, which is only temporarily connected to the power tool 200 or the battery 300.

FIG. 3 shows a simplified illustration of the electrical device 200 from FIG. 1. The electrical device 200 shown here as a block diagram includes the

Display device 100 with the light indicator 110 arranged in a housing opening of the electrical device 200 and the control device 120 arranged in the housing of the electrical device 200. The light indicator 110 comprises a total of five LEDs or LED segments 111 to 115, which are arranged behind a common transparent window structure 116. We also from Figure 3 can be seen, the light sensor 140 is arranged in the immediate vicinity of the first LED 111, so that it looks through the transparent window structure 116 together with the LEDs 111 to 115. The arrangement of the light sensor 140 in the immediate vicinity of the illuminated display 110 enables a particularly precise measurement of the ambient brightness, which is necessary for a corresponding adjustment of the luminous intensity of the illuminated display 110. Furthermore, no additional cover for the light sensor 140 is required in this construction.

As already described above, the light indicator 110 and the associated lighting device 100 can also be arranged on an accessory 300 of the electrical device 200. Such an alternative arrangement of the lighting device 100 within a battery pack 300 serving as an accessory is shown in FIG. The lighting device 100 also has a

Charge status indicator light indicator 110, which comprises five separate LEDs 111-115. In contrast to the embodiment from FIG. 3, in which all the LEDs are arranged behind a common window structure, the individual LEDs 111-115 of the light display 110 shown here each have separate window structures 116. The additional light sensor 140 is located directly next to the first LED 111 arranged so that the light sensor 140 and the first LED 111 use a common window structure 116.

As can also be seen from FIG. 3, the control device 120 comprises a special control circuit 121 for controlling the illuminated display 110 or the individual LEDs 111-115. The digital or analog control circuit 121 is designed to detect the ambient brightness with the aid of the light sensor 140 and to adapt the luminosity of the light segments 111 to 115 as a function of the detected ambient brightness. Various methods are possible to control the brightness of an LED 111 to 115.

For example, the LED can be controlled using a pulse-width-modulated signal, by means of which the LEDs are repeatedly switched on and off at relatively short time intervals. The ratio of the duration of the on and off phases determines the current brightness of the LEDs. For example, an extension of the switch-off phases and / or a

Shortening the switch-on phases perceived by the slow human eye as a reduction in the brightness of the LEDs. Alternatively, the Control circuit 121, which is implemented, for example, with the aid of a microcontroller, vary the supply voltage of the LEDs with the aid of a suitable circuit in order to adjust the luminosity of the illuminated display 110 in

Adjust ambient brightness.

FIG. 5 shows an example of a digitally implemented control circuit 121 as part of the control device 120. The control circuit 121 comprises one

Microcontroller 123 for controlling an LED 111. The LED 111 is connected via a series resistor 153 to an output PB5 of the microcontroller 123. The control circuit 121 further comprises a light sensor 140 in the form of a phototransistor, which is connected in series with an electrical resistor 152. The microcontroller 123 detects at its signal input PA3 the electrical potential of one arranged between the phototransistor 140 and the electrical resistor 152

Node 157. Since the ohmic resistance of the phototransistor 140 typically decreases with increasing ambient brightness, the electrical potential present at the signal input PA3 of the microcontroller 123 also changes accordingly with the ambient brightness. The microcontroller 121 is designed to change the electrical potential at its

Convert signal input PA3 into a corresponding control signal to control LED 111.

6 shows an alternative embodiment of the

Control device 120 with an analog control circuit 122

Control circuit 122 comprises an operational amplifier 124 which is connected to the cathode of LED 111 via a resistor 155. The analog control circuit 122 further comprises a light sensor in the form of a phototransistor 140. In the present example, the phototransistor 140 designed as an npn bipolar transistor is connected with its collector to a node 160 arranged between the anode of the LED 111 and a voltage source 170 and with its emitter via an electrical resistor 156 to the negative supply voltage GND. In this

Constellation, an increased ambient brightness reduces the ohmic resistance of the phototransistor 140, which leads to a reduction in the

Supply voltage and thus a lower brightness of the LED 111 leads. In contrast, a reduced ambient brightness increases the ohmic resistance of the phototransistor 140, which leads to a corresponding increase in the supply voltage and thus to a higher luminosity of the LED 111.

If the light sensor 140 is positioned directly next to an LED 111 of the illuminated display 110, as is the case for example in the exemplary embodiments shown in FIGS. 3 and 4, there is basically the risk that the light sensor 140 will also emit that emitted by the LED 111 in addition to the ambient light Light is captured and the measurement of the ambient brightness is falsified. To prevent this, the control circuit 121

be designed to evaluate the signal of the light sensor 140 before the LEDs 111-115 are switched on. If the illuminated display is in continuous operation, the control circuit 121 can also be designed to briefly interrupt the operation of the LEDs 111-115 in order to evaluate the brightness sensor during this time and then to adjust the brightness of the display accordingly. For such an interruption, a very short period of time is preferably used, which is imperceptible to the human eye, e.g. B. shorter than 10 ms. This embodiment is particularly useful in connection with a digital control circuit 121, since the LEDs are usually controlled by means of pulse width modulation. Accordingly, the ambient brightness is recorded in the switch-off phases of the pulse-width-modulated control signal. If a brief interruption of the lighting operation of the LEDs 111-115 is not desired or can only be implemented with great difficulty, which is usually the case when using an analog control circuit 122 for controlling the LEDs, the

Ambient brightness alternatively, a special light sensor 140 can also be used, which has a reduced sensitivity to light radiation with the wavelength emitted by the LEDs 111-115. Such

For example, wavelength selectivity can also be

suitable optical filter, which is arranged in front of the light sensor 140.

Basically all suitable ones can be used for the brightness measurement

Brightness sensors are used. However, when using it simple and inexpensive brightness sensors, such as

Phototransistors, disadvantageous that the corresponding sensor signal fluctuates very strongly with the temperature. In order to reduce the associated measurement inaccuracy, it makes sense for the control device 120 to detect the temperature of the light sensor 140 and thus the temperature-related variation of the

Sensor signal compensated. The

Use of a temperature sensor 150, which is present in the electrical device 200 anyway. Such temperature sensors are usually used

Monitoring the operating temperature of the electrical device 200 or the respective accessory 300 used. Since such a temperature sensor 150 is not necessarily arranged in the vicinity of the light sensor 140, the temperature measured with it can deviate from the actual temperature of the light sensor 140. Under certain circumstances, this will only allow inadequate compensation for the temperature dependence of the sensor signal. For this purpose, FIG. 7 shows a control circuit 121 equipped with a corresponding temperature sensor 151 to compensate for the temperature dependence of the light sensor 140, which is designed essentially analogously to the control circuit from FIG. 5. The in the present example in the form of a thermistor or

Thermistors with a negative temperature coefficient (NTC), temperature sensor 151, are connected in series with a further electrical resistor 154. The microcontroller 123 detects the electrical potential of a at its signal input PB5

Node 158 between the two resistors 151, 154. Due to the negative temperature coefficient of the temperature sensor 151, its ohmic resistance is reduced when the temperature rises, which has the result of a reduction in the electrical potential measured by the microcontroller 123 at its signal input PB4. On the other hand, a reduction in the temperature leads to an increase in the ohmic resistance of the temperature sensor 151, which is accompanied by an increase in the electrical potential determined by the microcontroller 123 at its signal input 11.

However, an improvement in the temperature compensation can be achieved by measuring the temperature of the light sensor 140 as directly as possible, which can be achieved, for example, by arranging the temperature sensor 150 in the immediate vicinity of the light sensor 140. If the light sensor 140, such as In the exemplary embodiment shown in FIG. 3, which is arranged directly next to an LED 111, this LED 111 can also be used as a temperature sensor 150. This takes advantage of the fact that the forward voltage of LED 111 is also strongly temperature-dependent. For this purpose, the relevant LED 111 is put into a known working state, for example in which a defined or at least known current is fed into the LED 111. The control device 120 then determines the forward voltage of the respective LED 111. The control device 120 can determine the current temperature of the relevant LED 111 from the measured forward voltage. Since the light sensor 140 has essentially the same temperature as the LED 111, the control device 120 can roughly determine the temperature of the light sensor 140 in this way. A correspondingly designed digital control circuit 121 is shown in FIG. 8. It can be seen that the microcontroller 123, with its signal input PC6, detects the electrical potential of a node 159 arranged between the LED 111 and the series resistor 153. In this arrangement, a change in the forward voltage of the LED 111 caused by an increase in the temperature leads to a measurable change in the electrical potential at the signal input 16 of the microcontroller 123.

Basically, this type of temperature measurement using LEDs 111-115 can also be used to measure the measured values of other temperature sensors

Electrical device 150 to make plausibility. They give way by means of the respective

Temperature sensor measured temperature and the temperature determined using the LEDs 111-115 strongly differ from each other, a control device of the electrical device 200 or the respective accessory 300 can recognize that a temperature measurement is unreliable. From this, the control device can derive, for example, the operation of the electrical device 200 or the

prevent the corresponding accessory 300 or issue a corresponding warning or error message to the user.

Although the invention has been illustrated and described in detail by the preferred exemplary embodiments, the invention is not restricted by the disclosed examples. Rather, other variations can be derived from this by a person skilled in the art without departing from the scope of protection of the invention.

Claims

Expectations

1. Display device (100) for a power tool (200) comprising a light indicator (110) with at least one LED (111, 112, 113, 114, 115), a control device (120) for controlling the light indicator (110) and a light sensor ( 140) designed to detect the ambient brightness, the control device (120) being designed to control the luminosity of the illuminated display (110) as a function of the ambient brightness detected using the light sensor (140).

2. Display device (100) according to claim 1,

wherein the light indicator (110) comprises an at least partially transparent window structure (116), and

wherein the at least one LED (111, 112, 113, 114, 115) and the

Light sensor (140) are arranged together behind the window structure (116).

3. Display device (100) according to claim 2,

wherein the control device (120) is designed, the at least one LED (111, 112, 113, 114, 115) at defined time intervals for a short

Deactivate the duration and in the time in which the LED (111, 112, 113, 114, 115) is deactivated, to detect the ambient brightness by means of the light sensor (140).

4. Display device (100) according to claim 3,

the control device (120) being designed to control the at least one LED (111, 112, 113, 114, 115) with the aid of a control signal modulated by means of pulse width modulation, and

wherein the control device (120) is also formed

Ambient brightness by means of the light sensor (140) in a switch-off phase of the control signal modulated by pulse width modulation. 5. Display device (100) according to claim 2 or 3,

wherein the at least one ED (111, 112, 113, 114, 115) is designed to emit light radiation with at least one defined wavelength, and

wherein the light sensor (140) has a reduced sensitivity for the at least one wavelength of the at least one LED (111, 112, 113, 114,

115) has emitted light radiation.

6. Display device (100) according to one of the preceding claims,

wherein the at least one LED (111, 112, 113, 114, 115) has a luminosity which varies with the temperature, and

wherein the control device (120) is designed to control the temperature of the at least one LED (111, 112, 113, 114, 115) using a

To determine temperature sensor (150) and to compensate for a temperature-related change in the luminosity based on the determined temperature.

7. Display device (100) according to claim 5,

wherein the at least one LED (111, 112, 113, 114, 115) as

Temperature sensor (150) is used, and

the control device (120) being designed to provide a temperature-dependent forward voltage of the at least one LED (111, 112, 113,

114, 115) and to determine the temperature of the at least one LED (111, 112, 113, 114, 115) by evaluating the detected forward voltage.

8. Display device (100) according to claim 6,

wherein the control device (120) is designed, which using the

To use forward voltage of the at least one LED (111, 112, 113, 114, 115) temperature to check the plausibility of the measurement results of another temperature sensor.

9. Display device (100) according to one of the preceding claims,

wherein the light indicator (110) is designed in the form of a charge status indicator.

10. Power tool (200) or power tool accessory (300) comprising a display device (100) according to one of claims 1 to 9.