Impact tool

1. An impact tool comprising:

a motor;

a tool support member which supports a work tool and is driven by the motor;

a hammer which applies a striking force in a rotational direction to the tool support member;

a rotating member which is arranged to be concentric with the tool support member, supports the hammer to be movable in an axial direction and the rotational direction with respect to the tool support member, and transmits motive power of the motor to the tool support member;

a switch member that sets rotation speed of the motor; and

a control unit which controls rotation speed of the motor or the rotating member,

wherein the hammer includes a plurality of first engaging portions,

wherein the tool support member includes a plurality of second engaging portions, and

wherein a number of times the hammer strikes the tool support member while the hammer rotates a single rotation with respect the tool support is adjusted based on the rotation speed of the motor or the rotating member and based on the number of the plurality of second engaging portions overpassed by one of the plurality of first engaging portions.

2. The impact tool according to claim 1 , wherein the plurality of first engaging portions includes three first engaging portions which are mutually arranged at an equal angle in the rotational direction, and

the plurality of second engaging portions includes three second engaging portions which are mutually arranged at an equal angle in the rotational direction and are struck separately by the three first engaging portions.

3. The impact tool according to claim 1 , wherein the impact tool is provided with a housing which contains the motor,

the motor is a brushless electric motor comprising:

a stator fixed to the housing and having a coil to which a current is supplied; and

a rotor which rotates when the current is supplied to the stator,

the impact tool comprises:

an inverter circuit which supplies the current to the coil;

the switch member that receives an input for setting rotation speed of the motor; and

the control unit controls the rotation speed of the motor by controlling a switching element of the inverter circuit in response to an operation of the rotation speed setting mechanism.

4. The impact tool according to claim 3 , wherein the control unit controls the rotation speed of the motor in response to any of:

a low-speed mode in which the rotation speed is set to first targeted rotation speed as the rotation speed of the motor;

a medium-speed mode in which the rotation speed is set to second targeted rotation speed higher than the first targeted rotation speed as the rotation speed of the motor; and

a high-speed mode in which the rotation speed is set to third targeted rotation speed higher than the second targeted rotation speed as the rotation speed of the motor.

5. The impact tool according to claim 4 , wherein the impact tool is provided with a DC power supply which supplies a current to the motor, and

the control unit sets the rotation speed of the motor to be any of the low-speed mode or the medium-speed mode when a voltage of the DC power supply is a predetermined value or lower.

6. The impact tool according to claim 5 , wherein the control unit executes:

control of setting a lower limit value and an upper limit value of the second targeted rotation speed and setting a lower limit value and an upper limit value of the third targeted rotation speed; and

control of performing, within one second, control to set the rotation speed of the motor between the lower limit value of the second targeted rotation speed and the upper limit value of the third targeted rotation speed when the voltage of the DC power supply is the predetermined value or lower.

7. The impact tool according to claim 1 , wherein the rotating member is provided with a first cam groove in an outer circumferential surface,

the hammer has an annular shape and is provided with a second cam groove in an inner circumferential surface,

a rolling element held by the first cam groove and the second cam groove is provided,

the hammer is movable in the axial direction and the rotational direction with respect to the tool support member by the rolling element rolling inside the first cam groove and the second cam groove,

a biasing member, which biases the hammer in the axial direction and in a direction of approaching the tool support member, is provided,

the first cam groove has a first inclined edge which is inclined with respect to the axial direction,

the second cam groove has a second inclined edge which is inclined with respect to the axial direction, and

both a first inclination angle on an acute angle side, which is formed between a straight line intersecting the axial direction and the first inclined edge, and a second inclination angle on an acute angle side, which is formed between the straight line and the second inclined edge, are set in a range of 24 degrees to 34 degrees.

8. The impact tool according to claim 1 , wherein the motor is an electric motor which generates motive power when a voltage is applied,

the control unit changes a number of strokes of the tool member due to one rotation of the hammer, and

the control unit increases the rotation speed of the rotating member by controlling the voltage applied to the electric motor after the hammer starts an operation of striking the tool support member, and decreases the number of strokes of the tool member due to the one rotation of the hammer.

9. The impact tool according to claim 1 , wherein the motor is an electric motor which generates motive power when a voltage is applied,

the control unit changes a number of strokes of the tool member due to the one rotation of the hammer, and

the control unit decreases the rotation speed of the rotating member by controlling the voltage applied to the electric motor after the hammer starts the operation of striking the tool support member, and increases the number of strokes of the tool member due to the one rotation of the hammer.